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ISOLATED LINEAGE NEGATIVE HEMATOPOIETIC STEM CELLS
AND METHODS OF TREATMENT THEREWITH
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Application for
Patent Serial No. 10/833,743, filed on April 28, 2004, which is a continuation-
in-part of U.S. Application for Patent Serial No. 10/628,783, filed on July
25,
2003, which claims the benefit of Provisional Application for Patent Serial
No.
60/398,522, filed on July 25, 2002, and Provisional Application for Patent
Serial
No. 60/467,051, filed on May 2, 2003, the entire disclosures of which are
incorporated herein by reference.
STATEMENT OF GOVERNMENT INTEREST
A portion of the work described herein was supported by grant
number CA92577 from the National Cancer Institute and by grants number
EY11254, EY12598 and EY125998 from the National Institutes of Health. The
United States Government has certain rights in this invention.
FIELD OF THE INVENTION
This invention relates to isolated, mammalian, stem cells. More
particularly the invention is related to lineage negative hematopoietic stem
cell
(Lin HSC) populations derived from bone marrow and methods of preserving
cone cells in a retina of a mammal suffering from an ocular degenerative
disease
by treating the eye of the mammal with the isolated Liri HSC populations.
BACKGROUND OF THE INVENTION
Age related macular degeneration (ARMD) and diabetic
retinopathy (DR) are the leading causes of visual loss in industrialized
nations
and do so as a result of abnormal retinal neovascularization. Since the retina
consists of well-defmed layers of neuronal, glial, and vascular elements,
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relatively small disturbances such as those seen in vascular proliferation or
edema
can lead to significant loss of visual function. Inherited retinal
degenerations,
such as retinitis pigmentosa (RP), are also associated with vascular
abnormalities,
such as arteriolar narrowing and vascular atrophy. Most inherited human
retinal
degenerations specifically affect rod photoreceptors, but there is also a
concomitant
loss of cones, the principal cellular component of the macula, the region of
the
retina in humans that is responsible for central, fme visual acuity. Cone-
specific
survival factors have been described recently (Mohand-Said et al. 1998, Proc.
Natl.
Acad. Sci. USA, 95: 8357-8362) and may facilitate cone survival in mouse
models
of retinal degeneration.
Inherited degenerations of the retina affect as many as 1 in 3500
individuals and are characterized by progressive night blindness, visual field
loss,
optic nerve atrophy, arteiriolar attenuation, altered vascular permeability
and
ceintral loss of vision often progressing to complete blindness (Heckenlively,
J.
R., editor, 1988; Retinitis Pigmentosa, Philadelphia: JB Lippincott Co.).
Molecular genetic analysis of these diseases has identified mutations in over
110
different genes accounting for only a relatively small percentage of the known
affected individuals (Humphries et al., 1992, Science 256:804-808; Farrar et
al.
2002, EMBO J. 21:857-864.). Many of these mutations are as'sociated with
enzymatic and structural components of the phototransduction machinery
including rhodopsin, cGMP phosphodiesterase, rds peripherin, and RPE65.
Despite these observations, there are still no effective treatments to slow or
reverse the progression of these retinal degenerative diseases. Recent
advances in
gene therapy have led to successful reversal of the rds (Ali et al. 2000, Nat.
Genet. 25:306-310) and rd (Takahashi et al. 1999, J. Virol. 73:7812-7816)
phenotypes in mice and the RPE65 phenotype in dogs (Acland et al. 2001, Nat.
Genet. 28:92-95) when the wild type transgene is delivered to photoreceptors
or
the retinal pigmented epithelium (RPE) in animals with a specific mutation.
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For many years it has been known that a population of stem cells
exists in the normal adult circulation and bone marrow. Different
sub-populations of these cells can differentiate along hematopoietic lineage
positive (Lin') or lineage negative (Lin') lineages. Furthermore, the lineage
negative hematopoietic stem cell (HSC) population has recently been shown to
contain endothelial progenitor cells (EPC) capable of forming blood vessels in
vitro and in vivo (See Asahara et al. 1997, Science 275: 964-7). These cells
can
participate in normal and pathological postnatal angiogenesis (See Lyden et
al.
2001 Nat. Med. 7, 1194-201; Kalka et al. 2000, Proc. Natl. Acad. Sci. U. S. A.
97:3422-7; and Kocher et al. 2001, Nat. Med. 7: 430-6) as well as
differentiate
into a variety of non-endothelial cell types including hepatocytes (See
Lagasse et
al. 2000, Nat. Med. 6:1229-34), microglia (See Priller et al. 2002 Nat. Med.
7:1356-61), cardiomyocyties (See Orlic et al. 2001, Proc. Natl. Acad. Sci. U.
S.
A. 98:10344-9) and epithelium (See Lyden et al. 2001, Nat. Med. 7:1194-1201).
Although these cells have been used in several experimental models of
angiogenesis, the mechanism of EPC targeting to neovasculature is not known
and no strategy has been identified that will effectively increase the number
of
cells that contribute to a particular vasculature.
Hematopoietic stem cells from bone marrow are currently the only
type of stem cell commonly used for therapeutic applications. Bone marrow
HSC's have been used in transplants for over 40 years. Currently, advanced
methods of harvesting purified stem cells are being investigated to develop
therapies for treatment of leukemia, lymphoma, and inherited blood disorders.
Clinical applications of stem cells in humans have been investigated for the
treatment of diabetes and advanced kidney cancer in limited numbers of human
patients.
SUMMARY OF THE INVENTION
The present invention provides a method of ameliorating cone cell
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degeneration in the retina of a mammal that suffers from an ocular disease.
The
method comprises the step of administering to the retina of the mammal a
mammalian bone marrow-derived, isolated, lineage negative hematopoietic stem
cell population, which comprises hematopoietic stem cells and endothelial
progenitor cells. The cells are administered in an amount sufficient to retard
cone cell degeneration in the retina.
A preferred method comprises isolating from the bone marrow of a
mammal suffering from an ocular disease a lineage negative hematopoietic stem
cell population that includes endothelial progenitor cells and subsequently
intravitreally injecting the isolated stem cells into an eye of the mammal in
a
number sufficient to ameliorate the degeneration of cone cells in the retina.
The methods of the present invention utilize an isolated,
mammalian, lineage nega-tive hematopoietic stem cell (Lin HSC) population
(i.e.,
hematopoietic stem cells (HSCs) that do not express lineage surface antigens
(Lin) on their cell surface) derived from mammalian bone marrow. Preferably
the cells are autologous stem cells (i.e., derived from the bone marrow of the
individual mammal that is to be treated). The isolated, mammalian, population
of
Lin HSCs, includes endothelial progenitor cells (EPC), also known as
endothelial precursor cells, that selectively target activated retinal
astrocytes
when intravitreally injected into the eye. Preferably the mammal is a human.
In a preferred embodiment the Lin HSC populations of the present
invention are isolated by extracting bone marrow from a mammal suffering from
an ocular disease; separating a plurality of monocytes from the bone marrow;
labeling the monocytes with biotin-conjugated lineage panel antibodies to one
or
more lineage surface antigens, removing monocytes that are positive for the
lineage surface antigens and then recovering a Liri HSC population containing
EPCs. Preferably the monocytes are labeled with biotin-conjugated lineage
panel
antibodies to one or more lineage surface antigen selected from the group
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consisting of CD2, CD3, CD4, CD11, CD11a, Mac-1, CD14, CD16, CD19,
CD24, CD33, CD36, CD38, CD45, Ly-6G, TER-119, CD45RA, CD56, CD64,
CD68, CD86, CD66b, HLA-DR, and CD235a (Glycophorin A). Preferably, at
least about 20% of the cells of the isolated Lin7 HSC population of the
present
invention express the surface antigen CD31. The isolated cells are then
administered to the diseased eye of the mammal, preferably by intraocular
injection. In a preferred embtldiment, at least about 50% the isolated Lin7
HSCs
express the surface antigen CD31 and at least about 50% the isolated Lin7 HSCs
express the surface antigen CD117 (c-kit).
The EPC's within the population of Lin HSCs of the present
invention extensively incorporate into developing retinal blood vessels and
into
the neuronal network of the retina, and remain stably incorporated into
neovasculature and neuroinal network of the eye. The normal mouse retina is
predominantly rods, however, in mice treated by the methods of the present
invention, the rescued cells after treatment with Lin-HSCs were surprisingly
nearly
all cones.
In one preferred embodiment, the cells of the isolated Lin HSC
populations are transfected with a therapeutically useful gene. For example,
the
cells can be transfected with polynucleotides that operably encode for
neurotrophic agents or anti-angiogenic agents that selectively target
neovasculature and inhibit new vessel formation without affecting already
established vessels through a form of cell-based gene therapy. In one
embodiment, the isolated, Lin7 HSC populations useful in the methods of the
present invention include a gene encoding an angiogenesis inhibiting peptide.
The angiogenesis inhibiting Lin7 HSCs are useful for modulating abnormal blood
vessel growth in diseases such as ARMD, DR and certain retinal degenerations
associated with abnormal vasculature. In another preferred embodiment, the
isolated, Lin HSCs of the present invention include a gene encoding a
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neurotrophic peptide. The neurotrophic Lin7 HSCs are useful for promoting
neuronal rescue in ocular diseases involving retinal neural degeneration, such
as
glaucoma, retinitis pigmentosa, and the like.
A particular advantage of ocular treatments with the isolated
Lin HSC populations of the present invention is a vasculotrophic and
neurotrophic rescue effect observed in eyes intravitreally treated with the
Lin7 HSCs. Retinal neurons and photoreceptors, particularly cones, are
preserved and some measure of visual function can be maintained in eyes
treated
with the isolated Lin7 HSCs of the invention.
Preferably the diseased retina to be treated by the methods of the
invention includes activated astrocytes. This can be accomplished by early
treatment of the eye when there is an associated gliosis, or by using a laser
to
stimulate local proliferation of activated astrocytes.
BRIEF DESCRIPTION OF THE DRAWINGS
In the DRAWINGS:
FIGURE 1 depicts schematic diagrams of developing mouse retina.
(a) Development of primary plexus. (b) The second phase of retinal vessel
formation. GCL, ganglion cell layer; IPL, inner plexus layer; INL, inner
nuclear
layer; OPL, outer plexus layer; ONL, outer nuclear layer; RPE, retinal pigment
epithelium; ON, optic nerve; P, periphery. Panel (c) depicts flow cytometric
characterization of bone marrow-derived Lin' HSC and Lin7 HSC separated cells.
Top row: Dot plot distribution of non-antibody labeled cells, in which R1
defmes
the quantifiable-gated area of positive PE-staining; R2 indicates GFP-
positive;
Middle row: Lin7 HSC (C57B/6) and Bottom row: Lin+ RSC (C57B/6) cells,
each cell line labeled with the PE-conjugated antibodies for Sca-1, c-kit,
Flk-1/KDR, CD31. Tie-2 data was obtained from Tie-2-GFP mice. Percentages
indicate percent of positive-labeled cells out of total Lin7 HSC or Lin+ HSC
population.
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FIGURE 2 depicts engraftment of Lin HSCs into developing
mouse retina. (a) At four days post-injection (P6) intravitreally injected
eGFPt
Lin HSC cells attach and differentiate on the retina (b) Lin HSC
(B6.129S7-Gtrosa26 mice, stained with p-gal antibody) establish themselves
ahead of the vasculature stained with collagen IV antibody (asterisk indicates
tip
of vasculature). (c) Most of Lin+ HSC cells (eGFP') at four days post-
injection
(P6) were unable to differentiate. (d) Mesenteric eGFP+ murine EC four days
post-injection (P6). (e) Lin7 HSCs (eGFP') injected into adult mouse eyes. (f)
Low magnification of eGFP+ Lin7 HSCs (arrows) homing to and differentiating
along the pre-existing astrocytic template in the GFAP-GFP transgenic mouse.
(g) Higher magnification of association between Lin7 cells (eGFP) and
underlying
astrocyte (arrows). (h) Non-injected GFAP-GFP transgenic control. (i) Four
days post-injection (P6), -eGFP' Lin7 HSCs migrate to and undergo
differentiation
in the area of the future deep plexus. Left figure captures Lin HSC activity
in a
whole mounted retina; right figure indicates location of the Liri cells
(arrows) in
the retina (top is vitreal side, bottom is scleral side). (j) Double labeling
with
a-CD31-PE and a-GFP-alexa 488 antibodies. Seven days after injection, the
injected Lin7 HSCs (eGFP), red) were incorporated into the vasculature (CD3
1).
Arrowheads indicate the incorporated areas. (k) eGFP+ Lin- HSC cells form
vessels fourteen days post-injection (P17). (1 and m) Intra-cardiac injection
of
rhodamine-dextran indicates that the vessels are intact and functional in both
the
primary (1) and deep plexus (m).
FIGURE 3 shows that eGFP+ Lin7 HSC cells home to the gliosis
(indicated by GFAP expressing-astrocytes, far left image) induced by both
laser
(a) and mechanical (b) induced injury in the adult retina (asterisk indicates
injured site). Far right images are a higher magnification, demonstrating the
close association of the Lin7 HSCs and astrocytes. Calibration bar= 204M.
FIGURE 4 shows that Lin7 HSC cells rescue the vasculature of the
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retinal degeneration mouse. (a-d) Retinas at 27 days post-injection (P33) with
collagen IV staining; (a) and (b), retinas injected with Lin' HSC cells
(Balb/c)
showed no difference in vasculature from normal FVB mice; (c) and (d) retinas
injected with Lin HSCs (Balb/c) exhibited a rich vascular network analogous to
a
wild-type mouse; (a) and (c), frozen sections of whole retina (top is vitreal
side,
bottom is scleral side) with DAPI staining; (b) and (d), deep plexus of
retinal
whole amount; (e) bar graph illustrating the increase in vascularity of the
deep
vascular plexus formed in the Lin HSC cell-injected retinas (n=6). The extent
of deep retinal vascularization was quantified by calculating the total length
of
vessels within each image. Average total length of vessels/high power field
(in
microns) for Lin HSC, Lin+HSC or control retinas were compared. (f)
Comparison of the length of deep vascular plexus after injection with Lin HSC
(R, right eye) or Lin "HSC (L, left eye) cells from rd/rd mouse. The results
of
six independent mice are shown (each color represents each mouse). (g) and (h)
Lin HSC cells also (Balb/c) rescued the rd/rd vasculature when injected into
P15
eyes. The intermediate and deep vascular plexus of Lin HSC (G) or Lin+HSC
(H) cell injected retinas (one month after injection) are shown.
FIGURE 5 depicts photomicrographs of mouse retinal tissue: (a)
deep layer of retinal whole mount (rd/rd mouse), five days post-injection
(P11)
with eGFP' Lin HSCs visible (gray). (b) and (c) P60 retinal vasculature of
Tie-2-GFP (rd/rd) mice that received Balb/c Lin cells (b) or Lin+HSC cell (c)
injection at P6. Only endogenous endothelial cells (GFP-stained) are visible
in
the left panels of (b) and (c). The middle panels of (b) and (c) are stained
with
CD31 antibody; arrows indicate the vessels stained with CD31 but not with GFP,
the right panels of (b) and (c) show staining with both GFP and CD3 1. (d) a-
SMA staining of Lin- HSC injected (left panel) and control retina (right
panel).
FIGURE 6 shows that T2-TrpRS-transfected Liri HSCs inhibit the
development of mouse retinal vasculature. (a) Schematic representation of
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human TrpRS, T2-TrpRS and T2-TrpRS with an Igk signal sequence at the amino
terminus. (b) T2-TrpRS transfected Lin HSC-injected retinas express T2-TrpRS
protein in vivo. (1) Recombinant T2-TrpRS produced in E. coli; (2) Recombinant
T2-TrpRS produced in E. coli; (3) Recombinant T2-TrpRS produced in E. coli;
(4) control retina; (5) Lin HSC + pSecTag2A (vector only) injected retina; (6)
Liri HSC + pKLel35 (Igk-T2-TrpRS in pSecTag) injected retina. (a)
Endogenous TrpRS. (b) Recombinant T2-TrpRS. (c) T2-TrpRS of Liri HSC
injected retina. (c-f) Representative primary (superficial) and secondary
(deep)
plexuses of injected retinas, seven days post-injection; (c) and (d) Eyes
injected
with empty plasmid-transfected Lin HSC developed normally; (e) and (f) the
majority of T2-TrpRS-transfected Lin HSC injected eyes exhibited inhibition of
deep plexus; (c) and (e) primary (superficial) plexus; (d) and (f) secondary
(deep) plexus). Faint outline of vessels observed in (f) are "bleed-through"
images of primary network vessels shown in (e).
FIGURE 7 shows the DNA sequence encoding His6-tagged
T2-TrpRS, SEQ ID NO: 1.
FIGURE 8 shows the amino acid sequence of His6-tagged T2-
TrpRS, SEQ ID NO: 2.
FIGURE 9 illustrates photomicrographs and electroretinograms
(ERG) of retinas from mice whose eyes were injected with the Liri HSC of the
present invention and with Lin+ HSC (controls).
FIGURE 10 depicts statistical plots showing a correlation between
neuronal rescue (y-axis) and vascular rescue (x-axis) for both the
intermediate
(Int.) and deep vascular layers of rdlyd mouse eyes treated with Liri HSC.
FIGURE 11 depicts statistical plots showing no correlation
between neuronal rescue (y-axis) and vascular rescue (x-axis) for rd/rd mouse
eyes that were treated with Lin'HSC.
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FIGURE 12 is a bar graph of vascular length (y-axis) in arbitrary
relative units for rd/rd mouse eyes treated with the Liri HSC (dark bars) and
untreated (light bars) rd/rd mouse eyes at time points of 1 month (IM), 2
months
(2M), and 6 months (6M) post-injection.
FIGURE 13 includes three bar graphs of the number of nuclei in
the outer neural layer (ONR) of rd/rd mice at 1 month (1M), 2 months (2M) and
6 months (6M), post-injection, and demonstrates a significant increase in the
number of nuclei for eyes treated with Lin HSC (dark bars) relative to control
eyes treated with Lin+ HSC (light bars).
FIGURE 14 depicts plots of the number of nuclei in the outer
neural layer for individual yd/rd mice, comparing the right eye (R, treated
with
Lin HSC) relative to the left eye (L, control eye treated with Lin+ HSC) at
time
points (post injection) of 1 month (1M), 2 months (2M), and 6 months (6M);
each line in a given plot compares the eyes of an individual mouse.
FIGURE 15 depicts retinal vasculature and neural cell changes in
rdl/rdl (C3H/HeJ, left panels) or wild type mice (C57BL/6, right panels).
Retinal vasculature of intermediate (upper panels) or deep (middle panels)
vascular plexuses in whole-mounted retinas (red: collagen IV, green: CD3 1)
and
sections (red: DAPI, green: CD3 1, lower panels) of the same retinas are shown
(P: postnatal day). (GCL: ganglion cell layer, INL: inter nuclear layer, ONL:
outer nuclear layer).
FIGURE 16 shows that Liri HSC injection rescues the
degeneration of neural cells in rdl /rdl mice. (A, B and C), retinal
vasculature of
intermediate (int.) or deep plexus and sections of Lin HSC injected eye (right
panels) and contralateral control cell (CD31-) injected eye (left panels) at
P30
(A), P60 (B), and P180 (C). (D), the average total length of vasculature (+ or
-
standard error of the mean) in Liri HSC injected or control cell (CD31' )
injected
retinas at P30 (left, n=10), P60 (middle, n=10), and P180 (right, n=6). Data
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of intermediate (Int.) and deep vascular plexus are shown separately (Y axis:
relative length of vasculature). (E), the average numbers of cell nuclei in
the
ONL at P30 (left, n=10), P60 (middle, n=10), or P180 (right, n=6) of control
cell (CD31-) or Lin HSC injected retinas (Y axis: relative number of cell
nuclei
in the ONL). (F), Linear correlations between the length of vasculature (X
axis)
and the number of cell nuclei in the ONL (Y axis) at P30 (left), P60 (middle),
and P180 (right) of Lin7 HSC or control cell injected retinas.
FIGURE 17 demonstrates that retinal function is rescued by
Lin HSC injection. Electroretinographic (ERG) recordings were used to measure
the function of Lin HSC or control cell (CD31- ) injected retinas. (A and B),
Representative cases of rescued and non-rescued retinas 2 months after
injection.
Retinal section of Lin HSC injected right eye (A) and CD3 1- control cell
injected
left eye (B) of the same anirnal are shown (green: CD31 stained vasculature,
red:
DAPI stained nuclei). (C), ERG results from the same animal shown in (A &
B).
FIGURE 18 shows that a population of human bone marrow cells
can rescue degenerating retinas in the rdl mouse (A-C). The rescue is also
observed in another model of retinal degeneration, rdlO (D-K). A, human
Lin HSCs (hLiri HSCs) labeled with green dye can differentiate into retinal
vascular cells after intravitreal injection into C3SnSmn.CB17-Prkdc SCID mice.
(B and C), Retinal vasculature (left panels; upper: intermediate plexus,
lower:
deep plexus) and neural cells (right panel) in hLiri HSC injected eye (B) or
contralateral control eye (C) 1.5 months after injection. (D-K), Rescue of
rd10
mice by Liri HSCs (injected at P6). Representative retinas at P21 (D: Lin7
HSCs,
H: control cells), P30 (E: Lin7 HSCs, I: control cells), P60 (F: Lin HSCs, J:
control cells), and P105 (G: Lin HSCs, K: control cells) are shown (treated
and
control eyes are from the same animal at each time point). Retinal vasculature
(upper image in each panel is the intermediate plexus; the middle image in
each
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panel is the deep plexus) was stained with CD31 (green) and Collagen IV (red).
The lower image in each panel shows a cross section made from the same retina
(red: DAPI, green: CD31).
FIGURE 19 demonstrates that crystallin aA is up regulated in
rescued outer nuclear layer cells after treatment with Lin HSCs but not in
contralateral eyes treated with control cells. Left panel; IgG control in
rescued
retina, Middle panel; crystallin aA in rescued retina, Right panel; crystallin
aA in
non-rescued retina. i
FIGURE 20 includes tables of genes that are upregulated in murine
retinas that have been treated with the Lin7 HSCs of the present invention.
(A)
Genes whose expression is increased 3-fold in mouse retinas treated with
murine
Lin7 HSCs. (B) Crystallin genes that are upregulated in mouse retinas treated
with murine Lin HSC. (C) Genes whose expression is increased 2-fold in mouse
retinas treated with human Liri HSCs. (D) Genes for neurotrophic factors or
growth factors whose expression is upregulated in mouse retinas treated with
human Lin7 HSCs.
FIGURE 21 illustrates the distribution of CD31 and integrin a6
surface antigens on CD133 positive (DC133') and CD133 negative (CD133-)
human Lin7 HSC populations of the present invention. The left panels show flow
cytometry scatter plots. The center and right panels are histograms showing
the
level of specific antibody expression on the cell population. The Y axis
represents the number of events and the X axis shows the intensity of the
signal.
A filled histogram shifted to the right of the outlined (control) histogram
represents an increased fluorescent signal and expression of the antibody
above
background level.
FIGURE 22 illustrates postnatal retinal development in wild-type
C57/B16 mice raised in normal oxygen levels (normoxia), at post natal days P0
through P30.
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FIGURE 23 illustrates oxygen-induced retinopathy model in
C57/B 16 mice raised in high oxygen levels (hyperoxia; 75 % oxygen) between P7
and P12, followed by normoxia from P12-P17.
FIGURE 24 demonstrates vascular rescue by treatment with the
Lin HSC populations of the present invention in the oxygen -induced
retinopathy
model.
FIGURE 25 shows rescued photoreceptors in rdl mouse outer
nuclear layer (ONL) following intravitreal injection of Lin-HSC are
predominantly
cones. A small percentage of photoreceptors in the wild type mouse retina
(upper
panel) were cones as evidenced by expression of red/green cone opsin (A) while
most cells of the ONL were positive for rod specific rhodopsin (B). Retinal
vasculature autofluoresces with pre-immune serum (C) but nuclear layers were
completely negative for staining with rod or cone-specific opsins. Rd/rd mouse
retinas (lower panels) had a diminished inner nuclear layer and a nearly
completely
atrophic ONL, both of which were negative for cone (D) or rod (Panel G) opsin.
Control, CD31- HSC treated eyes are identical to non-inj ected rd/rd retinas,
without
any staining for cone (E) or rod (H) opsin. Lin-HSC treated contralateral eyes
exhibited a markedly reduced, but clearly present ONL that is predominantly
comprised of cones, as evidenced by positive immunoreactivity for cone
red/green
opsin (F). A small number of rods were also observed (I).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Stem cells are typically identified by the distribution of antigens on
the surface of the cells (for a detailed discussion see Stem Cells: Scientific
Progress and Future Directions, a report prepared by the National Institutes
of
Health, Office of Science Policy, June 2001, Appendix E: Stem Cell Markers,
which is incorporated herein by reference to the extent pertinent).
The present invention provides a method of ameliorating cone cell
degeneration in the retina of a mammal that suffers from an ocular disease. A
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mammalian bone marrow-derived, isolated, lineage negative hematopoietic stem
cell population, which comprises hematopoietic stem cells and endothelial
progenitor cells, is administered to the retina of the mammal, preferably by
intravitreal injection. The cells are administered in an amount sufficient to
ameliorate cone cell degeneration in the retina.
A preferred method comprises isolating the lineage negative,
hematopoietic stem cell population from the bone marrow of the mammal to be
treated and then administering the cells to the mammal in a number sufficient
to
ameliorate the degeneration of cone cells in the retina.
The cells can be obtained from the diseased mammal, preferably at
an early stage of the ocular-disease. Alternatively, the cells can be obtained
prior
to the onset of disease in a patient known to have a genetic predisposition to
an
ocular disease such as retinitis pigmentosa, for example. The cells can be
stored
until needed, and can then be injected prophylactically at the first observed
indication of disease onset. Preferably the diseased retina includes activated
astrocytes, to which the stem cells are targeted. Accordingly, early treatment
of
the eye when there is an associated gliosis is beneficial. Alternatively, the
retina
can be treated with a laser to stimulate local proliferation of activated
astrocytes
in the retina prior to administering the autologous stem cells. .
Hematopoietic stem cells are that stem cells that are capable of
developing into various blood cell types e.g., B cells, T cells, granulocytes,
platelets, and erythrocytes. The lineage surface antigens are a group of
cell-surface proteins that are markers of mature blood cell lineages,
including
CD2, CD3, CD11, CD11a, Mac-1 (CD11b:CD18), CD14, CD16, CD19, CD24,
CD33, CD36, CD38, CD45, CD45RA, murine Ly-6G, murine TER-119, CD56,
CD64, CD68, CD86 (B7.2), CD66b, human leucocyte antigen DR (HLA-DR),
and CD235a (Glycophorin A). Hematopoietic stem cells that do not express
significant levels of these antigens are commonly referred to a lineage
negative
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(Liri ). Human hematopoietic stem cells commonly express other surface
antigens
such as CD31, CD34, CD117 (c-kit) and/or CD133. Murine hematopoietic stem
cells commonly express other surface antigens such as CD34, CD117 (c-kit),
Thy-1, and/or Sca-1.
The present invention provides isolated hematopoietic stem cells
that do not express significant levels of a "lineage surface antigen" (Lin) on
their
cell surfaces. Such cells are referred to herein as "lineage negative" or
"Lin"
hematopoietic stem cells. In particular this invention provides a population
of
Lin7 hematopoietic stems cells (Lin HSCs) that include endothelial progenitor
cells (EPCs), which are capable of incorporating into developing vasculature
and
then differentiating to become vascular endothelial cells. Preferably the
isolated
Lin7 HSC populations are present in a culture medium such as phosphate
buffered
saline (PBS).
As used herein and in the appended claims, the phrase "adult" in
reference to bone marrow, includes bone marrow isolated postnatally, i.e.,
from
juvenile and adult individuals, as opposed to embryos. The term "adult mammal"
refers to both juvenile and fully mature mammals.
The isolated, mammalian, lineage negative hematopoietic stem cell
(Lin HSC) populations of the invention include endothelial progenitor cells
(EPCs). The isolated Lin7 HSC populations preferably comprise mammalian cells
in which at least about 20% of the cells express the surface antigen CD3 1,
which
is commonly present on endothelial cells. In other embodiment, at least about
50% of the cells express CD31, more preferably at least about 65%, most
preferably at least about 75 %. Preferably at least about 50 % of the cells of
the
Lin7 HSC populations of the present invention preferably express the integrin
a6
antigen.
In one preferred murine Lin HSC population embodiment, at least
about 50% of the cells express CD31 antigen and at least about 50% of the
cells
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express the CD 117 (c-kit) antigen. Preferably, at least about 75 % of the
Lin7 HSC cells express the surface antigen CD3 1, more preferably about 81 %
of
the cells. In another preferred murine embodiment, at least about 65 % of the
cells express the surface antigen CD117, more preferably about 70% of the
cells.
A particularly preferred embodiment of the present invention is a population
of
murine Lin7 HSCs in which about 50 % to about 85 % of the cells express the
surface antigen CD31 and about 70 % to about 75 % of the cells express the
surface antigen CD 117.
Another preferred embodiment is a human Lin7 HSC population in
which the cells are CD 133 negative, in which at least about 50% of the cells
express the CD31 surface antigen and at least about 50% of the cells express
the
integrin a6 antigen. Yet another preferred embodiment is a human Lin7 HSC
population in which the cells are CD133 positive, in which at less than about
30% of the cells express the CD31 surface antigen and less than about 30% of
the
cells express the integrin a6 antigen.
The isolated Lin HSC populations of the present invention
selectively target astrocytes and incorporate into the retinal neovasculature
when
intravitreally injected into the eye of the mammalian species, such as a mouse
or
a human, from which the cells were isolated.
The isolated Liri HSC populations of the present invention include
endothelial progenitor cells that differentiate to endothelial cells and
generate
vascular structures within the retina. In particular, the Liri HSC populations
of
the present invention are useful for the treatment of retinal neovascular and
retinal vascular degenerative diseases, and for repair of retinal vascular
injury.
The Lin7 HSC cells of the present invention also promote neuronal rescue in
the
retina and promote upregulation of anti-apoptotic genes. It has surprisingly
been
found that adult human Lin7 HSC cells of the present invention can inhibit
retinal
degeneration even in severe combined immunodeficient (SCID) mice suffering
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from retinal degeneration. The normal mouse retina is predominantly rods, but
the
rescued cells, after treatment with Lin-HSC are nearly all cones.
Additionally, the
Liri HSC populations can be utilized to treat retinal defects in the eyes of
neonatal mammals, such as mammals suffering from oxygen induced retinopathy
or retinopathy of prematurity.
The present invention also provides a method of treating ocular
diseases in a manunal comprising isolating from the bone marrow of the mammal
a lineage negative hematopoietic stem cell population that includes
endothelial
progenitor cells, and intravitreally injecting the isolated stem cells into an
eye of
the mammal in a number sufficient to arrest the disease. The present method
can
be utilized to treat ocular diseases such as retinal degenerative diseases,
retinal
vascular degenerative diseases, ischemic retinopathies, vascular hemorrhages,
vascular leakage, and choroidopathies in neonatal, juvenile or fully mature
mammals. Examples of such diseases include age related macular degeneration
(ARMD), diabetic retinopathy (DR), presumed ocular histoplasmosis (POHS),
retinopathy of prematurity (ROP), sickle cell anemia, and retinitis
pignientosa, as
well as retinal injuries.
The number of stem cells injected into the eye is sufficient for
arresting the disease state of the eye. For example, the number of cells can
be
effective for repairing retinal damage of the eye, stabilizing retinal
neovasculature, maturing retinal neovasculature, and preventing or repairing
vascular leakage and vascular hemorrhage.
Cells of the Liri HSC populations of the present invention can be
transfected with therapeutically useful genes, such as genes encoding
antiangiogenic proteins for use in ocular, cell-based gene therapy and genes
encoding neurotrophic agents to enhance neuronal rescue effects.
The transfected cells can include any gene which is therapeutically
useful for treatment of retinal disorders. In one preferred embodiment, the
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transfected Lin HSCs of the present invention include a gene operably encoding
an antiangiogenic peptide, including proteins, or protein fragments such as
TrpRS
or antiangiogenic fragments thereof, e.g., the T1 and T2 fragments of TrpRS,
which are described in detail in co-owned, co-pending U.S. patent application
Serial No. 10/080,839, the disclosure of which is incorporated herein by
reference. The transfected Lin HSCs encoding an antiangiogenic peptide of the
present invention are useful for treatment of retinal diseases involving
abnormal
vascular development, such as diabetic retinopathy, and like,diseases.
Preferably
the Lin HSCs are human cells.
In another preferred embodiment, the transfected Lin HSCs of the
present invention include a gene operably encoding a neurotrophic agent such
as
nerve growth factor, neurotrophin-3, neurotrophin-4, neurotrophin-5, ciliary
neurotrophic factor, retinal pigmented epithelium-derived neurotrophic factor,
insulin-like growth factor, glial cell line-derived neurotrophic factor,
brain-derived neurotrophic factor, and the like. Such neurotrophic Liri HSCs
are
useful for promoting neuronal rescue in retinal neuronal degenerative diseases
such as glaucoma and retinitis pigmentosa, in treatment of injuries to the
retinal
nerves, and the like. Implants of ciliary neurotrophic factor have been
reported
as useful for the treatment of retinitis pigmentosa (see Kirby et al. 2001,
Mol
Ther. 3(2):241-8; Farrar et al. 2002, EMB(? Journal 21:857-864). Brain-derived
neurotrophic factor reportedly modulates growth associated genes in injured
retinal ganglia (see Fournier, et al., 1997, J. Neurosci. Res. 47:561-572).
Glial
cell line derived neurotrophic factor reportedly delays photoreceptor
degeneration
in retinitis pigmentosa (see McGee et al. 2001, Mol Ther. 4(6):622-9).
The present invention also provides a method of isolating a lineage
negative hematopoietic stem cells comprising endothelial progenitor cells from
bone marrow of a mammal. The method entails the steps of (a) extracting bone
marrow from an adult mammal; (b) separating a plurality of monocytes from the
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bone marrow; (c) labeling the monocytes with biotin-conjugated lineage panel
antibodies to one or more lineage surface antigens, preferably lineage surface
antigens selected from the group consisting of CD2, CD3, CD4, CD11, CD11a,
Mac-1, CD14, CD16, CD19, CD24, CD33, CD36, CD38, CD45, Ly-6G
(murine), TER-119 (murine), CD45RA, CD56, CD64, CD68, CD86 (B7.2),
CD66b, human leucocyte antigen DR (HLA-DR), and CD235a (Glycophorin A);
(d) removing monocytes that are positive for said one or more lineage surface
antigens from the plurality of monocytes and recovering a population of
lineage
negative hematopoietic stem cells containing endothelial progenitor cells,
preferably in which at least about 20 % of the cells express CD3 1.
When the Lin HSC are isolated from adult human bone marrow,
preferably the monocytes are labeled with biotin-conjugated lineage panel
antibodies to lineage surface antigens CD2, CD3, CD4, CD11a, Mac-1, CD14,
CD16, CD19, CD33, CD38, CD45RA, CD64, CD68, CD86 (B7.2), and
CD235a. When the Lin HSC are isolated from adult murine bone marrow,
preferably the monocytes are labeled with biotin-conjugated lineage panel
antibodies to lineage surface antigens CD3, CD 11, CD45, Ly-6G, and TER-119.
In a preferred method, the cells are isolated from adult human
bone marrow and are further separated by CD133 lineage. One preferred method
of isolating human Lin- HSCs includes the additional steps of labeling the
monocytes with a biotin-conjugated CD133 antibody and recovering a CD133
positive, Liri HSC population. Typically, less than about 30 % of such cells
express CD31 and less than about 30% of such cell express integrin a6. The
human Cd133 positive, Liri HSC populations of the present invention can target
sites of peripheral ischemia-driven neovascularization when injected into eyes
that
are not undergoing angiogenesis.
Another preferred method of isolating human Lin HSCs includes
the additional steps of labeling the monocytes with a biotin-conjugated CD133
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antibody, removing CD133 positive cells, and recovering a CD133 negative,
Lin HSC population. Typically, at least about 50% of such cells express CD31
and at least about 50% of such cell express integrin a6. The human CD133
negative, Lin7 HSC populations of the present invention can incorporate into
developing vasculature when injected into eyes that are undergoing
angiogenesis.
The present invention also provides methods for treating ocular
angiogenic diseases by administering transfected Lin7 HSC cells of the present
invention by intravitreal injection of the cells into the eye. Such
transfected
Lin HSC cells comprise Lin HSC transfected with a therapeutically useful gene,
such as a gene encoding antiangiogenic or neurotrophic gene product.
Preferably
the transfected Liri HSC cells are human cells.
Preferably, at least about 1 x 105 Lin7 HSC cells or transfected
Lin7 HSC cells are administered by intravitreal injection to a mammalian eye
suffering from a retinal degenerative disease. The number of cells to be
injected
may depend upon the severity of the retinal degeneration, the age of the
mammal
and other factors that will be readily apparent to one of ordinary skill in
the art of
treating retinal diseases. The Lin HSC may be administered in a single dose or
by multiple dose administration over a period of time, as determined by the
clinician in charge of the treatment.
The Lin HSCs of the present invention are useful for the treatment
of retinal injuries and retinal defects involving an interruption in or
degradation
of the retinal vasculature or retinal neuronal degeneration. Human Lin7 HSCs
also can be used to generate a line of genetically identical cells, i.e.,
clones, for
use in regenerative or reparative treatment of retinal vasculature, as well as
for
treatment or amelioration of retinal neuronal degeneration.
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EXAMPLES
Example 1. Cell Isolation and Enrichment; Preparation of Murine Lin HSC
Populations A and B.
General Procedure. All in vivo evaluations were performed in
accordance with the NIH Guide for the Care and Use of Laboratory Animals, and
all evaluation procedures were approved by The Scripps Research Institute
(TSRI, La Jolla, CA) Animal Care and Use Committee. Bone marrow cells were
extracted from B6.129S7-Gtrosa26, Tie-2GFP, ACTbEGFA, FVB/NJ (rd/rd
mice) or Balb/cBYJ adult mice (The Jackson Laboratory, ME).
Monocytes were then separated by density gradient separation
using HISTOPAQUEO polysucrose gradient (Sigma, St. Louis, MO) and labeled
with biotin conjugated lineage panel antibodies (CD45, CD3, Ly-6G, CD 11,
TER-1 19, Pharmingen, San Diego, CA) for Lin selection in mice. Lineage
positive (Lin') cells were separated and removed from Lin HSC using a
magnetic separation device (AUTOMACSTM sorter, Miltenyi Biotech, Auburn,
CA). The resulting Lin HSC population, containing endothelial progenitor cells
was further characterized using a FACSTM Calibur flow cytometer (Becton
Dickinson, Franldin Lakes, NJ) using following antibodies: PE-conjugated-Sca-
1,
c-kit, KDR, and CD31 (Pharmingen, San Diego, CA). Tie-2-GFP bone marrow
cells were used for characterization of Tie-2.
To harvest adult mouse endothelial cells, mesenteric tissue was
surgically removed from ACTbEGFP mouse and placed in collagenase
(Worthington, Lakewood, NJ) to digest the tissue, followed by filtration using
a
45 m filter. Flow-through was collected and incubated with Endothelial Growth
Media (Clonetics, San Diego, CA). Endothelial characteristics were confirmed
by observing morphological cobblestone appearance, staining with CD31 mAb
(Pharmingen) and examining cultures for the formation of tube-like structures
in
MATRIGELTM matrix (Beckton Dickinson, Franldin Lakes, NJ).
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Murine Lin HSC Population A. Bone marrow cells were
extracted from ACTbEGFP mice by the General Procedure described above. The
Lin" HSC cells were characterized by FACS flow cytometry for CD31, c-kit,
Sca-1, Flk-1, and Tie-2 cell surface antigen markers. The results are shown in
FIG. 1(c). About 81 % of the Liu HSC exhibited the CD31 marker, about
70.5 % of the Lin HSC exhibited the c-kit marker, about 4% of the Lin HSC
exhibited the Sca-i marker, about 2.2% of the Lin HSC exhibited the F1k-1
marker and about 0.91 % of the Lin HSC cell exhibited the Tie-2 marker. In
contrast, the Lin' HSC that were isolated from these bone marrow cells had a
significantly different cell marker profile (i.e., CD31: 37.4%; c-kit: 20%;
Sca-i:
2.8 %; Flk-: 0.05%).
Murine Lin- HSC Population B. Bone marrow cells were
extracted from Balb/C, ACTbEGFP, and C3H mice by the General Procedure
described above. The Liri HSC cells were analyzed for the presence of cell
surface markers (Sca-1, KDR, c-kit, CD34, CD31 and various integrins: al, a2,
0, a4, a5, a6, aM= av1 ax, aTtbaI RII R41 R31 04= R5and R,). The results are
shown
in Table 1.
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Table 1. Characterization of Lin' HSC Population B.
Cell Marker Liui HSC
a1 0.10
a2 17.57
a3 0.22
a4 89.39
a5 82.47
a6 77.70
aL 62.69
aM 35.84
aX 3.98
aV 33.64
aIIb 0.25
(31 86.26
p2 49.07
R3 45.70
p4 0.68
p5 9.44
p7 11.25
CD31 51.76
CD34 55.83
Flk-1/KDR 2.95,
c-kit (CD 117) 74.42
Sca-1 7.54
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Example 2. Intravitreal Administration of Cells in a Murine Model.
An eyelid fissure was created in a mouse eyelid with a ftne blade
to expose the P2 to P6 eyeball. Lineage negative HSC Population A of the
present invention (approximately 105 cells in about 0.5 1 to about 1 l of
cell
culture medium) was then injected intravitreally using a 33-gauge (Hamilton,
Reno, NV) needled-syringe.
Example 3. EPC Transfection.
Murine Liri HSC (Population A) were transfected with DNA
encoding the T2 fragment of TrpRS also enclosing a His6 tag (SEQ ID NO: 1,
FIG. 7) using FuGENETM6 Transfection'Reagent (Roche, Indianapolis, IN)
according to manufacturer's protocol. Lin HSC cells (about 106 cell per ml)
were suspended in opti-MEM medium (Invitrogen, Carlsbad, CA) containing
stem cell factor (PeproTech, Rocky Hill, NJ). DNA (about 1 g) and FuGENE
reagent (about 3 l) mixture was then added, and the mixtures were incubated
at
about 37 C for about 18 hours. After incubation, cells were washed and
collected. The transfection rate of this system was approximately 17 % that
was
confirmed by FACS analysis. T2 production was confirmed by western blotting.
The amino acid sequence of His6-tagged T2-TrpRS is shown as SEQ ID NO: 2,
FIG. 8.
Example 4. Immunohistochemistry and Confocal Analysis.
Mouse retinas were harvested at various time points and were
prepared for either whole mounting or frozen sectioning. For whole mounts,
retinas were fixed with 4% paraformaldehyde, and blocked in 50 % fetal bovine
serum (FBS) and 20% normal goat serum for one hour at ambient room
temperature. Retinas were processed for primary antibodies and detected with
secondary antibodies. The primaries used were: anti-Collagen IV (Chemicon,
Temecula, CA, anti-p-gal (Promega, Madison, WI), anti-GFAP (Dako
Cytomation, Carpenteria, CA), anti-a-smooth muscle actin (a-SMA, Dako
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Cytomation). Secondary antibodies used were conjugated either to Alexa 488 or
594 fluorescent markers (Molecular Probes, Eugene, OR). Images were taken
using an MRC 1024 Confocal microscope (Bio-Rad, Hercules, CA).
Three-dimensional images were created using LASERSHARP software (Bio-
Rad) to examine the three different layers of vascular development in the
whole
mount retina. The difference in GFP pixel intensity between enhanced GFP
(eGFP) mice and GFAP/wtGFP mice, distinguished by confocal microscopy, was
utilized to create the 3 dimensional images.
Example 5. In vivo Retinal Angiogenesis Quantification Assay in Mice.
For T2-TrpRS analysis, the primary and deep plexus were
reconstructed from the three dimensional images of mouse retinas. The primary
plexus was divided into two categories: normal development, or halted vascular
progression. The categories of inhibition of deep vascular development were
construed based upon the percentage of vascular inhibition including the
following criteria: complete inhibition of deep plexus formation was labeled
"Complete", normal vascular development (including less than 25% inhibition)
was labeled "Normal" and the remainder labeled "Partial. " For the rd/rd mouse
rescue data, four separate areas of the deeper plexus in each whole mounted
retina were captured using a lOx lens. The total length of vasculature was
calculated for each image, summarized and compared between the groups. To
acquire accurate information, Lin HSC were injected into one eye and Lin+ HSC
into another eye of the same mouse. Non-injected control retinas were taken
from the same litter.
Example 6. Adult Retinal Injury Murine Models.
Laser and scar models were created using either a diode laser (150
mW, 1 second, 50 nun) or mechanically by puncturing the mouse retina with a 27
gauge needle. Five days after injury, cells were injected using the
intravitreal
method. Eyes were harvested from the mice five days later.
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Example 7. Neurotrophic Rescue of Retinal Regeneration.
Adult murine bone marrow derived lineage negative hematopoietic
stem cells (Liri HSC) have a vasculotrophic and neurotrophic rescue effect in
a
mouse model of retinal degeneration. Right eyes of 10-day old mice were
injected intravitreally with about 0.5 microliters containing about 10s Lin
HSC of
the present invention and evaluated 2 months later for the presence of retinal
vasculature and neuronal layer nuclear count. The left eyes of the same mice
were injected with about the same number of Lin+HSC as a control, and were
similarly evaluated. As shown in FIG. 9, in the Liri HSC treated eyes, the
retinal vasculature appeared nearly normal, the inner nuclear layer was nearly
normal and the outer nuclear layer (ONL) had about 3 to about 4 layers of
nuclei.
In contrast, the contralateral Lin+HSC treated eye had a markedly atrophic
middle retinal vascular layer, a completely atrophic outer retinal vascular
layer;
the inner nuclear layer was markedly atrophic and the outer nuclear layer was
completely gone. This was dramatically illustrated in Mouse 3 and Mouse 5. In
Mouse 1, there was no rescue effect and this was true for approximately 15 %
of
the injected mice.
When visual function was assessed with electroretinograms (ERG),
the restoration of a positive ERG was observed when both the vascular and
neuronal rescue was observed (Mice 3 and 5). Positive ERG was not observed
when there was no vascular or neuronal rescue (Mouse 1). This correlation
between vascular and neurotrophic rescue of the rd/rd mouse eyes by the
Lin HSC of the present invention is illustrated by a regression analysis plot
shown in FIG. 10. A correlation between neuronal (y-axis) and vascular (x-
axis)
recovery was observed for the intermediate vasculature type (r=0.45) and for
the
deep vasculature (r=0.67).
FIG. 11 shows the absence of any statistically, significant
correlation between vascular and neuronal rescue by Lin+ HSC. The vascular
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rescue was quantified and the data are presented in FIG. 12. Data for mice at
1
month (1M), 2 months (2M), and 6 months (6M), post-injection shown in FIG.
12, demonstrate that vascular length was significantly increased in eyes
treated
with the Lin7 HSC of the present invention (dark bars) relative to the
vascular
length in untreated eyes from the same mouse (light bars), particularly at 1
month
and 2 months, post-injection. The neurotrophic rescue effect was quantified by
counting nuclei in the inner and outer nuclear layers about two months after
injection of Lin7 HSC or Lin'HSC. The results are presented in FIG. 13 and 14.
Example S. Human Lin HSC Population.
Bone marrow cells were extracted from healthy adult human
volunteers by the General Procedure described above. Monocytes were then
separated by density gradient separation using HISTOPAQUE polysucrose
gradient (Sigma, St. Louis, MO). To isolate the Lin7 HSC population from
human bone marrow mononuclear cells the following biotin conjugated lineage
panel antibodies were used with the magnetic separation system (AUTOMACSTM
sorter, Miltenyi Biotech, Auburn, CA): CD2, CD3, CD4, CD11a, Mac-1, CD14,
CD16, CD19, CD33, CD38, CD45RA, CD64, CD68, CD86, CD235a
(Pharmingen),.
The human Lin7 HSC population was further separated into two
sub-populations based on CD133 expression. The cells were labeled with biotin-
conjugated CD133 antibodies ans separated into CD133 positive and CD133
negative sub-populations.
Example 9. Intravitreal Administration of Human and Murine Cells in
Murine Models for Retinal Degeneration.
C3H/HeJ, C3SnSmn.CB17-Prkdc SCID, and rdlO mouse strains
were used as retinal degeneration models. C3H/HeJ and C3SnSmn.CB17-Prkdc
SCID mice (The Jackson Laboratory, Maine) were homozygous for the retinal
degeneration 1(rdl) mutation, a mutation that causes early onset severe
retinal
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degeneration. The mutation is located in exon 7 of the Pde6b gene encoding the
rod photoreceptor cGMP phosphodiesterase (3 subunit. The mutation in this gene
has been found in human patients with autosomal recessive retinitis pigmentosa
(RP). C3SnSmn.CB17-Prkdc SCID mice are also homozygous for the severe
combined immune deficiency spontaneous mutation (Prkdc SCID) and were used
for human cell transfer experiments. Retinal degeneration in rd10 mice is
caused
by a mutation in exon 13 of Pde6b gene. This is also a clinically relevant RP
model with later onset and milder retinal degeneration than rdl/rdl). All
evaluations were performed in accordance with the NIH Guide for the Care and
Use of Laboratory Animals, and all procedures were approved by The Scripps
Research Institute Animal. Care and Use Committee.
An eyelid fissure was created in a mouse eyelid with a fme blade
to expose the P2 to P6 eyeball. Lineage negative HSC cells for murine
population A or human population C (approximately 105 cells in about 0.5 111
to
about 1 l of cell culture medium) were then injected in the mouse eye
intravitreally using a 33-gauge (Hamilton, Reno, NV) needled-syringe. To
visualize the injected human cells, cells were labeled with dye (Cell tracker
green
CMFDA, Molecular Probes) before injection.
Retinas were harvested at various time points and fixed with 4%
paraformaldehyde (PFA) and methanol followed by blocking in 50% FBS/20%
NGS for one hour at room temperature. To stain retinal vasculature, retinas
were
incubated with anti-CD31 (Pharmingen) and anti-collagen IV (Chemicon)
antibodies followed by Alexa 488 or 594 conjugated secondary antibodies
(Molecular Probes, Eugene, Oregon). The retinas were laid flat with four
radial
relaxing incisions to obtain a whole mount preparation. Images of vasculature
in
intermediate or deep retinal vascular plexuses (see Dorrell et al. 2002 Invest
Ophthalrnol. Vis. Sci. 43:3500-3510) were obtained using a Radiance MP2100
confocal microscope and LASERSHARP software (Biorad, Hercules,
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California). For quantification of vasculature, four independent fields (900
m x
900 pm) were chosen randomly from the mid portion of the intermediate or deep
vascular layer and the total length of vasculature was measured using
LASERPIX analyzing software (Biorad). The total lengths of these four fields
in the same plexus were used for further analysis.
The flat-mounted retinas were re-embedded for cryostat sections.
Retinas were placed in 4% PFA overnight followed by incubation with 20 %
sucrose. The retinas were embedded in optimal cutting temperature compound
(OCT: Tissue-Tek; Sakura FineTech, Torrance, CA). Cryostat sections (10 m)
were re-hydrated in PBS containing the nuclear dye DAPI (Sigma-Aldrich, St.
Louis, Missouri). DAPI-labeled nuclear images of three different areas (280 m
width, unbiased sampling) in a single section that contained optic nerve head
and
the entire peripheral retina were taken by confocal microscope. The numbers of
the nuclei located in ONL of the three independent fields in one section were
counted and summed up for analysis. Simple linear-regression analysis was
performed to examine the relationship between the length of vasculature in the
deep plexus and the number of cell nuclei in the ONL.
Following overnight dark-adaptation, mice were anesthetized by
intraperitoneal injection of 15 g/gm ketamine and 7 g/gm xylazine.
Electroretinograms (ERGs) were recorded from the corneal surface of each eye
after pupil dilation (1 % atropine sulfate) using a gold loop corneal
electrode
together with a mouth reference and tail ground electrode. Stimuli were
produced with a Grass Photic Stimulator (PS33 Plus, Grass Instruments, Quincy,
MA) affixed to the outside of a highly reflective Ganzfeld dome. Rod responses
were recorded to short-wavelength (Wratten 47A; Xmax = 470 nm) flashes of
light
over a range of intensities up to the maximum allowable by the photic
stimulator
(0.668 cd-s/m2 ). Response signals were amplified (CP511 AC amplifier, Grass
Instruments), digitized (PCI-1200, National Instruments, Austin, TX) and
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computer-analyzed. Each mouse served as its own internal control with ERGs
recorded from both the treated and untreated eyes. Up to 100 sweeps were
averaged for the weakest signals. The averaged responses from the untreated
eye
were digitally subtracted from the responses from the treated eye and this
difference in signal was used to index functional rescue.
Microarray analysis was used for evaluation of Lin HSC-targeted
retinal gene expression. P6 rd/rd mice were injected with either Liri or CD31-
HSCs. The retinas of these mice were dissected 40 days post-injection in RNase
free medium (rescue of the retinal vasculature and the photoreceptor layer is
obvious at this time point after injection). One quadrant from each retina was
analyzed by whole mount to ensure that normal HSC targeting as well as
vasculature and neural protection had been achieved. RNA from retinas with
successful injections wasTurified using a TRIzol (Life Technologies,
Rockville,
MD), phenol/chloroform RNA isolation protocol. RNA was hybridized to
Affymetrix Mu74Av2 chips and gene expression was analyzed using
GENESPRING software (SiliconGenetics, Redwood City, CA). Purified human
or mouse HSCs were injected intravitreally into P6 mice. At P45 the retinas
were dissected and pooled into fractions of 1) human HSC-injected, rescued
mouse retinas, 2) human HSC-injected, non-rescued mouse retinas, and 3) mouse
HSC-injected, rescued mouse retinas for purification of RNA and hybridization
to
human-specific U133A Affymetrix chips. GENESPRINGO software was used to
identify genes that were expressed above background and with higher expression
in the human HSC-rescued retinas. The probe-pair expression profiles for each
of these genes were then individually analyzed and compared to a model of
normal human U133A microarray experiments using dChip to determine human
species specific hybridization and to eliminate false positives due to cross-
species
hybridization.
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FIGURE 21 illustrates flow cytometry data comparing the
expression of CD31 and integrin alpha 6 surface antigens on CD133 positive
(DC133+) and CD133 negative (CD133-) human Liri HSC populations of the
present invention. The left panels show flow cytometry scatter plots. The
center
and right panels are histograms showing the level of specific antibody
expression
on the cell population. The Y axis represents the number of events and the X
axis shows the intensity of the signal. The outlined histograms are isotype
IgG
control antibodies showing the level of non-specific background staining. The
filled histograms show the level of specific antibody expression on the cell
population. A filled histogram shifted to the right of the outlined (control)
histogram represents an increased fluorescent signal and expression of the
antibody above background level. Comparing the position of the peaks of the
filled histograms between the two cell populations represents the difference
in
protein expression on the cells. For example, CD31 is expressed above
background on both CD133+ and CD 133- cells of the invention; however, there
are more cells expressing lower levels of CD31 in the CD133+ cell population
than there are in the CD133- population. From this data it is evident that
CD31
expression varies between the two populations and that the alpha 6 integrin
expression is largely limited to cells in the Lin- population, and thus may
serve as
a marker of cells with vasculo- and neurotrophic rescue function.
When the CD133 positive and CD133 negative Lin HSC sub-
population was intravitreally injected into the eyes of neonatal SCID mice,
the
greatest extent of incorporation into the developing vasculature was observed
for
the CD133 negative sub-population, which expresses both CD31 and integrin a6
surface antigens (see FIG. 21, bottom). The CD133 positive sub-population,
which does not express CD31 or integrin a6 (FIG. 21, top) appears to target
sites
of peripheral ischemia-driven neovascularization, but not when injected into
eyes
undergoing angiogenesis.
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Rescued and non-rescued retinas were analyzed
immunohistochemically with antibodies specific for rod or cone opsin. The same
eyes used for the ERG recordings presented in FIG. 17 were analyzed for rod or
cone opsin. In wild type mouse retinas, less than 5% of photoreceptors present
are
cones (Soucy et al. 1998, Neuron 21: 481-493) and the immunohistochemical
staining pattenns observed with red/green cone opsin as shown in FIG. 25 (A)
or rod
rhodopsin as shown in FIG. 25 (B), were consistent with this percentage of
cone
cells. Antibodies specific for rod rhodopsin (rho4D2) were provided by Dr.
Robert
Molday of the University of British Columbia and used as described previously
(Hicks et al. 1986, Exp. Eye Res. 42: 55-71). Rabbit antibodies specific for
cone
red/green opsin were purchased from Chemicon (AB5405) and used according to
the manufacturer's instructions.
Example 10. Intravitreal Administration of Murine Celis in Murine Models
for Oxygen Induced Retinal Degeneration.
New born wild-type C57B16 mice were exposed to hyperoxia
(75% oxygen) between postnatal days P7 to P12 in an oxygen-induced retinal
degeneration (OIR) model. FIG 22 illustrates normal postnatal vascular
development in C57B16 mice from P0 to P30. At P0 only budding superficial
vessels can be observed around the optic disc. Over the next few days, the
primary superficial network extends toward the periphery, reaching the far
periphery by day P10. Between P7 and P12, the secondary (deep) plexus
develops. By P17, an extensive superficial and deep network of vessels is
present
(FIG. 22, insets). In the ensuing days, remodeling occurs along with
development of the tertiary (intermediate) layer of vessels until the adult
structure
is reached approximately at P21.
In contrast, in the OIR model, following exposure to 75 % oxygen
at P7-P12, the normal sequence of events is severely disrupted (FIG. 23).
Adult
murine Lin HSC populations of the invention were intravitreally injected at P3
in
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an eye of a mouse that was subsequently subjected to OIR, the other eye was
injected with PBS or CD31 negative cells as a control. FIG. 24 illustrates
that
the Lin HSC populations of the present invention can reverse the degenerative
effects of high oxygen levels in the developing mouse retina. Fully developed
superficial and deep retinal vasculature was observed at P17 in the treated
eyes,
whereas in the control eyes showed large avascular areas with virtually no
deep
vessels (FIG. 24). Approximately 100 eyes of mice in the OIR model were
observed. Normal vascularization was observed in 58% of the eyes treated with
the Liri HSC populations of the invention, compared to 12% of the control eyes
treated with CD31- cells and 3% of the control eyes treated with PBS.
RESULTS AND DISCUSSION
Murine Retinal Vascular Development; A Model for Ocular
Angiogenesis. The mouse eye provides a recognized model for the study of
mammalian retinal vascular development, such as human retinal vascular
development. During development of the murine retinal vasculature,
ischemia-driven retinal blood vessels develop in close association with
astrocytes.
These glial elements migrate onto the third trimester human fetus, or the
neonatal
rodent, retina from the optic disc along the ganglion cell layer and spread
radially. As the murine retinal vasculature develops, endothelial cells
utilize this
already established astrocytic template to determine the retinal vascular
pattern
(See FIG. 1 (a and b)). FIG. 1 (a and b) depicts schematic diagrams of
developing mouse retina. Panel (a) depicts development of the primary plexus
(dark lines at upper left of the diagram) superimposed over the astrocyte
template
(light lines) whereas, (b) depicts the second phase of retinal vessel
formation. In
FIG. 1, GCL stands for ganglion cell layer; IPL stands for inner plexus layer;
INL stands for inner nuclear layer; OPL stands for outer plexus layer; ONL
stands for outer nuclear layer; RPE stands for retinal pigment epithelium; ON
stands for optic nerve; and P stands for periphery.
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At birth, retinal vasculature is virtually absent. By postnatal day
14 (P14) the retina has developed complex primary (superficial) and secondary
(deep) layers of retinal vessels coincident with the onset of vision.
Initially,
spoke-like peripapillary vessels grow radially over the pre-existing
astrocytic
network towards the periphery, becoming progressively interconnected by
capillary plexus formation. These vessels grow as a monolayer within the nerve
fiber through P10 (FIG. 1(a)). Between P7-P8 collateral branches begin to
sprout from this primary plexus and penetrate into the retina to the outer
plexiform layer where they form the secondary, or deep, retinal plexus. By
P21,
the entire network undergoes extensive remodeling and a tertiary, or
intermediate, plexus forms at the inner surface of inner nuclear layer (FIG. 1
(b)).
The neonatal mouse retinal angiogenesis model is useful for
studying the role of HSC during ocular angiogenesis for several reasons. In
this
physiologically relevant model, a large astrocytic template exists prior to
the
appearance of endogenous blood vessels, permitting an evaluation of the role
for
cell-cell targeting during a neovascular process. In addition, this consistent
and
reproducible neonatal retinal vascular process is known to be hypoxia-driven,
in
this respect having similarities to many retinal diseases in which ischemia is
known to play a role.
Enrichment of Endothelial Progenitor Cells (EPC) From Bone
Marrow. Although cell surface marker expression has been extensively
evaluated on the EPC population found in preparations of HSC, markers that
uniquely identify EPC are still poorly defmed. To enrich for EPC,
hematopoietic
lineage marker positive cells (Lin+), i.e., B lymphocytes (CD45), T
lymphocytes
(CD3), granulocytes (Ly-6G), monocytes (CD11), and erythrocytes (TER-119),
were depleted from bone marrow mononuclear cells of mice. Sca-1 antigen was
used to further enrich for EPC. A comparison of results obtained after
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intravitreal injection of identical numbers of either Lin7 Sca-1+ cells or
Lin7 cells,
no difference was detected between the two groups. In fact, when only Liri
Sca-1- cells were injected, far greater incorporation into developing blood
vessels
was observed.
The Lin7 HSC populations of the present invention are enriched
with EPCs, based on functional assays. Furthermore, Lin+HSC populations
functionally behave quite differently from the Lin7 HSC populations. Epitopes
commonly used to identify EPC for each fraction (based on previously reported
in
vitro characterization studies) were also evaluated. While none of these
markers
were exclusively associated with the Lin7 fraction, all were increased about
70 to
about 1800% in the Lin7 HSC, compared to the Lin'HSC fraction (FIG. 1 (c)).
FIG. 1, Panel (c) illustrates flow cytometric characterization of bone
marrow-derived Lin+ HSC and Lin HSC separated cells. The top row of Panel
(c) shows a hematopoietic stem cell dot plot distribution of non-antibody
labeled
cells. Rl defines the quantifiable-gated area of positive PE-staining; R2
indicates
GFP-positive. Dot plots of Lin HSC are shown in the middle row and dot plots
of Lin+ HSC are shown in the bottom row. The C57B/6 cells were labeled with
the PE-conjugated antibodies for Sca-1, c-kit, Flk-1/KDR, CD31. Tie-2 data was
obtained from Tie-2-GFP mice. The percentages in the corners of the dot plots
indicate the percent of positive-labeled cells out of total Lin7 or Lin+ HSC
population. Interestingly, accepted EPC markers like Flk-1/KDR, Tie-2, and
Sca-1 were poorly expressed and, thus, not used for further fractionation.
Intravitreally Injected HSC Lin Cells Contain EPC That
Target Astrocytes and Incorporate into Developing Retinal Vasculature. To
determine whether intravitreally injected Lin7 HSC can target specific cell
types
of the retina, utilize the astrocytic template and participate in retinal
angiogenesis,
approximately 105 cells from a Lin7 HSC composition of the present invention
or
Lin+ HSC cells (control, about 105 cells) isolated from the bone marrow of
adult
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(GFP or LacZ transgenic) mice were injected into postnatal day 2 (P2) mouse
eyes. Four days after injection (P6), many cells from the Lin7 HSC composition
of the present invention, derived from GFP or LacZ transgenic mice were
adherent to the retina and had the characteristic elongated appearance of
endothelial cells (FIG. 2 (a)). FIG. 2 illustrates engraftment of Lin7 cells
into
developing mouse retina. As shown in FIG. 2, Panel (a), the four days
post-injection (P6) intravitreally injected eGFP+ Liri HSC attach and
differentiate on the retina.
In many areas of the retinas, the GFP-expressing cells were
arranged in a pattern conforming to underlying astrocytes and resembled blood
vessels. These fluorescent cells were observed ahead of the endogenous,
developing vascular network (FIG. 2 (b)). Conversely, only a small number of
Lin+HSC (FIG. 2 (c)), or adult mouse mesenteric endothelial cells (FIG. 2 (d))
attached to the retinal surface. In order to determine whether cells from an
injected Lin7 HSC population could also attach to retinas with already
established
vessels, we injected a Lin HSC composition into adult eyes. Interestingly, no
cells were observed to attach to the retina or incorporate into established,
normal
retinal blood vessels (FIG. 2 (e)). This indicates that the Lin7 HSC
compositions
of the present invention do not disrupt a normally developed vasculature and
will
not initiate abnormal vascularization in normally developed retinas.
In order to determine the relationship between an injected Lin7 HSC
compositions of the present invention and retinal astrocytes, a transgenic
mouse
was used, which expressed glial fibrillary acidic protein (GFAP, a marker of
astrocytes) and promoter-driven green fluorescent protein'(GFP). Examination
of
retinas of these GFAP-GFP transgenic mice injected with Liri HSC from eGFP
transgenic mice demonstrated co-localization of the injected eGFP EPC and
existing astrocytes (FIG. 2 (f-h), arrows). Processes of eGFP+Liri HSC were
observed to conform to the underlying astrocytic network (arrows, FIG. 2 (g)).
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Examination of these eyes demonstrated that the injected, labeled cells only
attached to astrocytes; in P6 mouse retinas, where the retinal periphery does
not yet
have endogenous vessels, injected cells were observed adherent to astrocytes
in
these not yet vascularized areas. Surprisingly, injected, labeled cells were
observed
in the deeper layers of the retina at the precise location where normal
retinal
vessels will subsequently develop (FIG. 2 (i), arrows).
To determine whether injected Lin HSC of the present invention are
stably incorporated into the developing retinal vasculature, retinal vessels
at several
later time points were examined. As early as P9 (seven days after injection),
Liri HSC incorporated into CD31'structures (FIG. 2(j)). By P16 (14 days after
injection), the cells were already extensively incorporated into retinal
vascular-like
structures (FIG. 2 (k)). When rhodamine-dextran was injected intravascularly
(to
identify functional retinal~blood vessels) prior to sacrificing the animals,
the
majority of Lin HSC were aligned with patent vessels (FIG. 2 (1)). Two
patterns
of labeled cell distribution were observed: (1) in one pattern, cells were
interspersed along vessels in between unlabeled endothelial cells; and (2) the
other
pattern showed that vessels were composed entirely of labeled cells. Injected
cells
were also incorporated into vessels of the deep vascular plexus (FIG. 2 (m)).
While sporadic incorporation of Lin- HSC-derived EPC into neovasculature has
been previously reported, this is the first report of vascular networks being
entirely
composed of these cells. This demonstrates that cells from a population of
bone
marrow-derived Lin HSC of the present invention injected intravitreally can
efficiently incorporate into any layer of the forming retinal vascular plexus.
Histological examination of non-retinal tis'sues (e.g., brain, liver,
heart, lung, bone marrow) did not demonstrate the presence of any GFP positive
cells when examined up to 5 or 10 days after intravitreal injection. This
indicates
that a sub-population of cells within the Lin HSC fraction selectively target
to
retinal astrocytes and stably incorporate into developing retinal vasculature.
Since
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these cells have many characteristics of endothelial cells (association with
retinal
astrocytes, elongate morphology, stable incorporation into patent vessels and
not
present in extravascular locations), these cells represent EPC present in the
Lin7 HSC population. The targeted astrocytes are of the same type observed in
many of the hypoxic retinopathies. It is well known that glial cells are a
prominent
component of neovascular fronds observed in DR and other forms of retinal
injury.
Under conditions of reactive gliosis and ischemia-induced neovascularization,
activated astrocytes proliferate, produce cytokines, and up-regulate GFAP,
similar
to that observed during neonatal retinal vascular template formation in many
mammalian species including humans.
Lin7 HSC populations of the present invention will target activated
astrocytes in adult mouse eyes as they do in neonatal eyes, Liri HSC cells
were
injected into adult eyes with retinas injured by photo-coagulation (FIG. 3
(a)) or
needle tip (FIG. 3 (b)). In both models, a population of cells with prominent
GFAP staining was observed only around the injury site (FIG. 3 (a and b)).
Cells
from injected Lin7 HSC compositions localized to the injury site and remained
specifically associated with GFAP-positive astrocytes (FIG. 3 (a and b)). At
these
sites, Lin HSC cells were also observed to migrate into the deeper layer of
retina
at a level similar to that observed during neonatal formation of the.deep
retinal
vasculature. Uninjured portions of retina contained no Lin HSC cells,
identical to
that observed when Lin7 HSC were injected into normal, uninjured adult retinas
(FIG. 2 (e)). These data indicate that Lin7 HSC compositions can selectively
target
activated glial cells in injured adult retinas with gliosis as well as
neonatal retinas
undergoing vascularization.
Intravitreally Injected Lin7 HSC Can Rescue and Stabilize
Degenerating Vasculature. Since intravitreally injected Lin HSC compositions
target astrocytes and incorporate into the normal retinal vasculature, these
cells also
stabilize degenerating vasculature in ischemic or degenerative retinal
diseases
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associated with gliosis and vascular degeneration. The rd/rd mouse is a model
for
retinal degeneration that exhibits profound degeneration of photoreceptor and
retinal vascular layers by one month after birth. The retinal vasculature in
these
mice develops normally until P16 at which time the deeper vascular plexus
regresses; in most mice the deep and intermediate plexuses have nearly
completely
degenerated by P30.
To determine whether HSC can rescue the regressing vessels, Lin+
or Lin HSC (from Balb/c mice) were injected into rd/rd mice intravitreally at
P6.
By P33, after injection with Lin+ cells, vessels of the deepest retinal layer
were
nearly completely absent (FIG. 4 (a and b)). In contrast, most Lin HSC-
injected
retinas by P33 had a nearly normal retinal vasculature with three parallel,
well-formed vascular layers (FIG. 4 (a and d)). Quantification of this effect
demonstrated that the average length of vessels in the deep vascular plexus of
Liri
injected rd/rd eyes was nearly three times greater than untreated or Lin+
cell-treated eyes (FIG. 4 (e)). Surprisingly, injection of a Lin HSC
composition
derived from rd/rd adult mouse (FVB/N) bone marrow also rescued degenerating
rd/rd neonatal mouse retinal vasculature (FIG. 4 (f)). Degeneration of the
vasculature in rd/rd mouse eyes in observed as early as 2-3 weeks post-
natally.
Injection of Lin HSC as late as P15 also resulted in partial stabilization of
the
degenerating vasculature in the rd/rd mice for at least bne month (FIG. 4 (g
and
h)).
A Lin HSC composition injected into younger (e.g., P2) rd/rd mice
also incorporated into the developing superficial vasculature. By P11, these
cells
were observed to migrate to the level of the deep vascular plexus and form a
pattern identical to that observed in the wild type outer retinal vascular
layer (FIG.
(a)). In order to more clearly describe the manner in which cells from
injected
Lin HSC compositions incorporate into, and stabilize, degenerating retinal
vasculature in the rd/rd mice, a Lin HSC composition derived from Balb/c mice
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was injected into Tie-2-GFP FVB mouse eyes. The FVB mice have the rd/rd
genotype and because they express the fusion protein Tie-2-GFP, all endogenous
blood vessels are fluorescent.
When non-labeled cells from a Liri HSC composition are injected
into neonatal Tie-2-GFP FVB eyes and are subsequently incorporated into the
developing vasculature, there should be non-labeled gaps in the endogenous,
Tie-2-GFP labeled vessels that correspond to the incorporated, non-labeled
Liri HSC that were injected. Subsequent staining with another vascular marker
(e.g., CD-3 1) then delineates the entire vessel, permitting deternunation as
to
whether non-endogenous endothelial cells are part of the vasculature. Two
months
after injection, CD31-positive, Tie-2-GFP negative, vessels were observed in
the
retinas of eyes injected with the Liri HSC composition (FIG. 5 (b)).
Interestingly,
the majority of rescued vessels contained Tie-2-GFP positive cells (FIG. 5
(c)).
The distribution of pericytes, as determined by staining for smooth muscle
actin,
was not changed by Lin HSC injection, regardless of whether there was vascular
rescue (FIG. 5 (d)). These data clearly demonstrate that intravitreally
injected
Lin HSC compositions of the present invention migrate into the retina,
participate
in the formation of normal retinal blood vessels, and stabilize endogenous
degenerating vasculature in a genetically defective mouse.
Inhibition of Retinal Angiogenesis by Transfected Cells from Lin-
HSC. The majority of retinal vascular diseases involve abnormal vascular
proliferation rather than degeneration. Transgenic cells targeted to
astrocytes can
be used to deliver an anti-angiogenic protein and inhibit angiogenesis. Cells
from
Liri HSC compositions were transfected with T2-tryptophanyl-tRNA synthetase
(T2-TrpRS). T2-TrpRS is a 43 kD fragment of TrpRS that potently inhibits
retinal
angiogenesis (FIG. 6 (a)). On P12, retinas of eyes injected with a control
plasmid-transfected Liri HSC composition (no T2-TrpRS gene) on P2 had normal
primary (FIG. 6 (c)) and secondary (FIG. 6 (d)) retinal vascular plexuses.
When
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the T2-TrpRS transfected Liri HSC composition of the present invention was
injected into P2 eyes and evaluated 10 days later, the primary network had
significant abnormalities (FIG. 6 (e)) and formation of the deep retinal
vasculature
was nearly completely inhibited (FIG. 6(f)). The few vessels observed in these
eyes were markedly attenuated with large gaps between vessels. The extent of
inhibition by T2-TrpRS-secreting Lin HSCs is detailed in Table 2.
T2-TrpRS is produced and secreted by cells in the Lin HSC
composition in vitro and after injection of these transfected cells into the
vitreous, a
30 kD fragment of T2-TrpRS in the retina (FIG. 6 (b)) was observed. This 30 kD
fragment was specifically observed only in retinas injected with transfected
Liri HSC of the present invention and this decrease in apparent molecular
weight
compared to the recombinant or in vitro-synthesized protein may be due to
processing or degradation4of the T2-TrpRS in vivo. These data indicate that
Liri HSC compositions can be used to deliver functionally active genes, such
as
genes expressing angiostatic molecules, to the retinal vasculature by
targeting to
activated astrocytes. While it is possible that the observed angiostatic
effect is due
to cell-mediated activity this is very unlikely since eyes treated with
identical, but
non-T2-transfected Liri HSC compositions had normal retinal vasculature.
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Table 2. Vascular Inhibition by T2-TrpRS-secreting Lin HSCs
Primary Plexus Deep Plexus
Inhibited Normal Complete Partial Normal
T2TrpRS 60% 40% 33.3% 60% 6.7%
(15 eyes) (9 eyes) (6 eyes) (5 eyes) (9 eyes) (1 eye)
Control 0% 100% 0% 38.5% 61.5%
(13 eyes) (0 eyes) (13 eyes) (0 eyes) (5 eyes) (8 eyes)
Intravitreally injected Lin HSC populations localize to retinal
astrocytes, incorporate into vessels, and can be useful in treating many
retinal
diseases. While most cells -from injected HSC compositions adhere to the
astrocytic template, small numbers migrate deep into the retina, homing to
regions
where the deep vascular network will subsequently develop. Even though no
GFAP-positive astrocytes were observed in this area prior to 42 days
postnatally,
this does not rule out the possibility that GFAP-negative glial cells are
already
present to provide a signal for Liri HSC localization. Previous studies have
shown
that many diseases are associated with reactive gliosis. In DR, in particular,
glial
cells and their extracellular matrix are associated with pathological
angiogenesis.
Since cells from injected Lin HSC compositions specifically
attached to GFAP-expressing glial cells, regardless of the type of injury, Lin
HSC
compositions of the present invention can be used to target pre-angiogenic
lesions
in the retina. For example, in the ischemic retinopathies such as diabetes,
neovascularization is a response to hypoxia. By targeting Lin HSC compositions
to sites of pathological neovascularization, developing neovasculature can be
stabilized preventing abnormalities of neovasculature such as hemorrhage or
edema
(the causes of vision loss associated with DR) and can potentially alleviate
the
hypoxia that originally stimulated the neovascularization. Abnormal blood
vessels
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can be restored to nonnal condition. Furthermore, angiostatic proteins, such
as
T2-TrpRS can be delivered to sites of pathological angiogenesis by using
transfected Liri HSC compositions and laser-induced activation of astrocytes.
Since laser photocoagulation is a commonly used in clinical ophthalmology,
this
approach has application for many retinal diseases. While such cell-based
approaches have been explored in cancer therapy, their use for eye diseases is
more
advantageous since intraocular injection makes it possible to deliver large
numbers
of cells directly to the site of disease.
Neurotrophic and Vasculotrophic Rescue by Lin'HSC. MACS
was used to separate Lin7 HSC from bone marrow of enhanced green fluorescent
protein (eGFP), C3H (rd/rd), FVB (rd/rd) mice as described above. Lin7 HSC
containing EPC from these mice were injected intravitreally into P6 C3H or~FVB
mouse eyes. The retinas-were collected at various time points (1 month, 2
months,
and 6 months) after injection. The vasculature was analyzed by scanning laser
confocal microscope after staining with antibodies to CD31 and retinal
histology
after nuclear staining with DAPI. Microarray gene expression analysis of mRNA
from retinas at varying time points was also used to identify genes
potentially
involved in the effect.
Eyes of rd/rd mice had profound degeneration of both neurosensory
retina and retinal vasculature by P21. Eyes of rd/rd mice treated with Lin7
HSC on
P6 maintained a normal retinal vasculature for as long as 6 months; both deep
and
intermediate layers were significantly improved when compared to the controls
at
all time points (1M, 2M, and 6M) (see FIG. 12). In addition, we observed that
retinas treated with Liri HSC were also thicker (1M; 1.2=fold, 2M; 1.3-fold,
6M;
1.4-fold) and had greater numbers of cells in the outer nuclear layer (1M; 2.2-
fold,
2M; 3.7-fold, 6M; 5.7-fold) relative to eyes treated with Lin' HSC as a
control.
Large scale genomic analysis of "rescued" (e.g., Lin7 HSC) compared to control
(untreated or non-Lin treated) rd/rd retinas demonstrated a significant
upregulation
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of genes encoding sHSPs (small heat shock proteins) and specific growth
factors
that correlated with vascular and neural rescue, including genes encoding the
proteins listed in FIG. 20, panels A and B.
The bone marrow derived Lin HSC populations of the present
invention significantly and reproducibly induced maintenance of a normal
vasculature and dramatically increased photoreceptor and other neuronal cell
layers
in the rd/rd mouse. This neurotrophic rescue effect correlated with
significant
upregulation of small heat shock proteins and growth factors and provides
insights
into therapeutic approaches to currently untreatable retinal degenerative
disorders.
Rdl/rdl Mouse Retinas Exhibit Profound Vascular and Neuronal
Degeneration. Normal postnatal retinal vascular and neuronal development in
mice has been well described and is analogous to changes observed in the third
trimester human fetus (Dorrell et al., 2002, Invest. Ophthalmol. Vis. Sci.
43:3500-
35 10). Mice homozygous for the rdl gene share many characteristics of human
retinal degeneration (Frasson et al., 1999, Nat. Med. 5:1183-1187) and exhibit
rapid photoreceptor (PR) loss accompanied by severe vascular atrophy. as the
result
of a mutation in the gene encoding PR cGMP phosphodiesterase (Bowes et al.
1990, Nature 347:677-680). To examine the vasculature during retinal
development and its subsequent degeneration, antibodies against collagen IV
(CIV),
an extracellular matrix (ECM) protein of mature vasculature, and CD31 (PECAM-
1), a marker for endothelial cells were used (FIG. 15). Retinas of rdl/rdl
(C3H/HeJ) developed normally until approximately postnatal day (P) 8 when
degeneration of the photoreceptor-containing outer nuclear layer (ONL) began.
The ONL rapidly degenerated and cells died by apoptosis such that only a
single
layer of nuclei remained by P20. Double staining of the whole-mounted retinas
with antibodies to both CIV and CD31 revealed details of the vascular
degeneration
in rdl /rdl mice similar to that described by others (Blanks et al., 1986, J.
Comp.
Neurol. 254:543-553). The primary and deep retinal vascular layers appeared to
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develop normally though P12 after which there is a rapid loss of endothelial
cells as
evidenced by the absence of CD31 staining. CD31 positive endothelial cells
were
present in a normal distribution through P12 but rapidly disappeared after
that.
Interestingly, CIV positive staining remained present throughout the time
points
examined, suggesting that the vessels and associated ECM formed normally, but
only the matrix remained after P13 by which time no CD31 positive cells were
observed. (FIG. 15, middle panels). The intermediate vascular plexus also
degenerates after P21, but the progression is slower than that observed in the
deep
plexus (FIG. 15, upper panel). Retinal vascular and neural cell layers of a
normal
mouse are shown for comparison to the rdl/rdl mouse (right panels, FIG. 15).
Neuroprotective Effect of Bone Marrow-Derived Lin- HSCs in
rdl/rdl Mice. Intravitreally injected Lin7 HSCs incorporate into endogenous
retinal vasculature in all three vascular plexuses and prevent the vessels
from
degenerating. Interestingly, the injected cells are virtually never observed
in the
outer nuclear layer. These cells either incorporate into the forming retinal
vessels
or are observed in close proximity to these vessels. Murine Lin7 HSCs (from
C3H/HeJ) were intravitreally injected into C3H/HeJ (rdl/rdX) mouse eyes at P6,
just prior to the onset of degeneration. By P30, control cell (CD31-)-injected
eyes
exhibited the typical ydl/rdl phenotype, i.e., nearly complete degeneration of
the
deep vascular plexus and ONL was observed in every retina examined. Eyes
injected with Lin HSCs maintained normal-appearing intermediate and deep
vascular plexuses. Surprisingly, significantly more cells were observed in the
internuclear layer (INL) and ONL of Lin HSC-injected eyes than in control cell-
injected eyes (FIG. 16 (A)). This rescue effect of Lin7 HSCs could be observed
at
2 months (FIG. 16 (B)) and for as long as 6 months after injection (FIG. 16
(C)).
Differences in the vasculature of the intermediate and deep plexuses of Lin7
HSC-
injected eyes, as well as the neuronal cell-containing INL and ONL, were
significant at all time points measured when rescued and non-rescued eyes were
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compared (FIG. 16 (B and C)). This effect was quantified by measuring the
total
length of the vasculature (FIG. 16 (D)) and counting the number of DAPI-
positive
cell nuclei observed in the ONL (FIG. 16 (E)). Simple linear-regression
analysis
was applied to the data at all time points.
A statistically significant correlation was observed between vascular
rescue and neuronal (e.g., ONL thickness) rescue at P30 (p < 0.024) and P60 (p
< 0.034) in the Liri HSC-injected eyes (FIG. 16 (F)). The correlation remained
high, although not statistically significant (p < 0.14) at P180 when comparing
Lin HSC-injected retinas to control cell-injected retinas (FIG. 16 (F)). In
contrast,
control cell-injected retinas showed no significant correlation between the
preservation of vasculature and ONL at any time point (FIG. 16 (F)). These
data
demonstrate that intravitreal injection of Lin HSCs results in concomitant
retinal
vascular and neuronal rescue in retinas of rdl/rdl mice. Injected cells were
not
observed in the ONL or any place other than within, or in close proximity to,
retinal blood vessels.
Functional Rescue of Liri HSC-injected rd/rd Retinas.
Electroretinograms (ERGs) were performed on mice 2 months after injection of
control cells or murine Liri HSCs (FIG. 17). Immunohistochemical and
microscopic analysis was done with each eye following ERG recordings to
confirm
that vascular and neuronal rescue had occurred. Representative ERG recordings
from treated, rescued and control, non-rescued eyes show that in the rescued
eyes,
the digitally subtracted signal (treated minus untreated eyes) produced a
clearly
detectable signal with an amplitude on the order of 8-10 microvolts (FIG. 17).
Clearly, the signals from both eyes are severely abnormal. However, consistent
and
detectable ERGs were recordable from the Lin HSC-treated eyes. In all cases
the
ERG from the control eye was non-detectable. While the amplitudes of the
signals
in rescued eyes were considerably lower than normal, the signals were
consistently
observed whenever there was histological rescue and were on the order of
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magnitude of those reported by other, gene based, rescue studies. Overall
these
results are demonstrate of some degree of functional rescue in the eyes
treated with
the Lin HSCs of the invention.
Rescued rai/rd retinal cell types are predominantly cones. Rescued
and non-rescued retinas were analyzed immunohistochemically with antibodies
'specific for rod or cone opsin. The same eyes used for the ERG recordings
presented
in FIG. 17 were analyzed for rod or cone opsin. In wild type mouse retinas,
less than
about 5% of photoreceptors present are cones (Soucy et al. 1998, Neuron 21:
481-493) and the immunohistochemical staining pattems observed with red/green
cone opsin as shown in FIG. 25 (A) or rod rhodopsin as shown in FIG. 25 (B),
were
consistent with this percentage of cone cells. When wild type retinas were
stained
with pre-immune IgG, no staining was observed anywhere in the neurosensory
retinas
other than autoflouresence of the blood vessels (FIG. 25 (C)). Two months
after
birth, retinas of non-injected rd/rd mice had an essentially atrophic outer
nuclear layer
that does not exhibit any staining with antibodies to red green cone opsin
(FIG. 25
(D)) or rhodopsin (FIG. 25 (G)). Eyes injected with control, CD31- HSC also
did not
stain positively for the presence of either cone (FIG. 25 (E))) or rod (FIG.
25 (H))
opsin. In contrast, contralateral eyes injected with Lin-HSC had about 3 to
about 8
rows of nuclei in a preserved outer nuclear layer; most of these cells were
positive for
cone opsin (FIG. 25 (F)) with approximately 1-3% positive for rod opsin (FIG.
25
(I)). Remarkably, this is nearly the reverse of what is ordinarily observed in
the
normal mouse retina, which is rod-dominated. These data demonstrate that the
injection of Lin-HSC preserves cones for extended periods of time during which
they
would ordinarily degenerate.
Human bone marrow (hBM)-derived Lin- HSCs also Rescue
Degenerating Retinas. Liri HSCs isolated from human bone marrow behave
similarly to murine Lin HSCs. Bone marrow was collected from human donors
and the Lin + HSCs were depleted, producing a population of human Liri HSCs
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(hLiri HSCs). These cells were labeled ex-vivo with fluorescent dye and
injected
into C3SnSmn.CB17-Prkdc SCID mouse eyes. The injected hLin HSCs migrated
to, and targeted, sites of retinal angiogenesis in a fashion identical to that
observed
when murine Liri HSCs were injected (FIG. 18 (A)). In addition to the vascular
targeting, the human Lin HSCs also provided a robust rescue effect on both the
vascular and neuronal cell layers of the rdl/rdl mice (FIG. 18 (B and Q. This
observation confirms the presence of cells in human bone marrow that target
retinal
vasculature and can prevent retinal degeneration.
Lin HSCs have Vasculo- and Neurotrophic Effects in the
rd10/rd10 Mouse. While the rdl/rdl mouse is the most widely used and best
characterized model for retinal degeneration (Chang et al. 2002, Vision Res.
42:517-525), the degeneration is very rapid and in this regard differs from
the
usual, slower time course observed in the human disease. In this strain,
photoreceptor cell degeneration begins around P8, a time when the retinal
vasculature is still rapidly expanding (FIG. 15). Subsequent degeneration of
the
deep retinal vasculature occurs even while the intermediate plexus is still
forming
and, thus, the retinas of rdl/rdl mice never completely develops, unlike that
observed in most humans with this disease. An rdlO mouse model, which has a
slower time course of degeneration and more closely resembles the human
retinal
degenerative condition, was used to investigate Lin HSC-mediated vascular
rescue.
In the rdlO mouse, photoreceptor cell degeneration begins around P21 and
vascular
degeneration begins shortly thereafter.
Since normal neurosensory retinal development is largely complete
by P21, the degeneration is observed to start after the retina has completed
differentiation and in this way is more analogous to human retinal
degenerations
than the rdl/rdl mouse model. Liri HSCs or control cells from rdlO mice were
injected into P6 eyes and the retinas were evaluated at varying time points.
At P21
the retinas from both Liri HSC and control cell-injected eyes appeared normal
with
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complete development of all vascular layers and normal development of the INL
and ONL (FIG. 18 (D and H)). At approximately P21 the retinal degeneration
began and progressed with age. By P30, the control cell-injected retinas
exhibited
severe vascular and neuronal degeneration (FIG. 18 (I)), while the Liri HSC-
injected retinas maintained nearly normal vascular layers and photoreceptor
cells
(FIG. 18 (E)). The difference between the rescued and non-rescued eyes was
more
pronounced at later time points (compare FIG. 18 (F and G) to 18 (J and K)).
In
the control treated eyes, the progression of vascular degeneration was very
clearly
observed by immunohistochemical staining for CD31 and collagen IV (FIG. 18 (1-
K)). The control-treated eyes were nearly completely negative for CD3 1,
whereas
collagen IV-positive vascular "tracks" remained evident, indicating that
vascular
regression, rather than incomplete vascular formation, had occurred. In
contrast,
Liri HSC-treated eyes had both CD31 and collagen IV-positive vessels that
appeared very similar to normal, wild-type eyes (compare FIG. 18 (F and I)).
Gene Expression Analysis of rd/rd Mouse Retinas after L'ui HSC
Treatment. Large scale genomics (microarray analysis) was used to analyze
rescued and non-rescued retinas to identify putative mediators of neurotrophic
rescue. Gene expression in rdl /rdl mouse retinas treated with Lin" HSCs was
compared to uninjected retinas as well as retinas injected with control cells
(CD31-). These comparisons each were performed in triplicate. To be considered
present, genes were required to have expression levels at least 2-fold higher
than
background levels in all three triplicates. Genes that were upregulated 3-fold
in
Liri HSC-protected retinas compared to control cell-injected and non-injected
rd/rd
mouse retinas are shown in FIG. 20, panels A and B. Coefficient of variance
(COV) levels were calculated for the expressed genes by dividing the standard
deviation by the mean expression level of each cRNA replicate. In addition,
the
correlation between expression levels and noise variance was calculated by
correlating the mean and standard deviation (SD). A correlation between gene
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expression level and standard deviation for each gene was obtained, allowing
background levels and reliable expression level thresholds to be determined.
As a
whole, the data fell well within acceptable limits (Tu et al. 2002, Proc.
Natl. Acad.
Sci. USA 99: 14031-14036). The genes that are discussed individually, below,
exhibited expression levels above these critical expression levels. Paired
"t=test
"values for the discussed genes are also presented in Table 1. In each case, p-
values
are reasonable (near or below 0.05), which demonstrates that there are
similarities
between replicates and probable significant differences between the different
test
groups. Many of the significantly upregulated genes, including MAD and Ying
Yang-1 (YY-1) (Austen et al. 1997, Curr. Top. Microbiol. Immunol. 224: 123-
130.),
encode proteins with functions involving the protection of cells from
apoptosis. A
number of crystallin genes, which have sequence homology and similar functions
to
known heat-shock proteins involving protection of cells from stress, were also
upregulated by Lin- HSC treatment. Expression of a-crystallin was localized to
the
ONL by immunohistochemical analysis (FIG. 19). FIGURE 19 shows that crystallin
aA is up regulated in rescued outer nuclear layer cells after treatment with
Lin HSCs but not in contralateral eyes treated with control cells. The left
panel
shows IgG staining (control) in rescued retina. The middle panel shows
crystallin
aA in a rescued retina. The right panel shows crystallin aA in non-rescued
retina.
Messenger RNA from rdl/rdl mouse retinas rescued with human
Lin HSCs were hybridized to human specific Affymetrix U133A microarray chips.
After stringent analysis, a number of genes were found whose mRNA expression
was human specific, above background, and significantly higher in the human
Lin HSC rescued retinas compared to the murine Liri HSC rescued retinas and
the
human control cell-injected non-rescued retinas (FIG. 20, panel C). CD6, a
cell
adhesion molecule expressed at the surface of primitive and newly
differentiated
CD34+ hematopoietic stem cells, and interferon alpha 13, another gene
expressed
by hematopoietic stem cells, were both found by the microarray bioinformatics
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technique, validating the evaluation protocol. In addition, several growth
factors
and neurotrophic factors were expressed above background by human Liri HSC
rescued mouse retina samples (FIG. 20, panel D).
Markers for lineage-committed hematopoietic cells were used to
negatively select a population of bone marrow-derived Liri HSC containing EPC.
While the sub-population of bone marrow-derived Lin HSC that can serve as EPC
is not characterized by commonly used cell surface markers, the behavior of
these
cells in developing or injured retinal vasculature is entirely different than
that
observed for Lin' or adult endothelial cell populations. These cells
selectively
target to sites of retinal angiogenesis and participate in the formation of
patent
blood vessels.
Inherited retinal degenerative diseases are often accompanied by loss
of retinal vasculature. Effective treatment of such diseases requires
restoration of
function as well as maintenance of complex tissue architecture. While several
recent studies have explored the use of cell-based delivery of trophic factors
or
stem cells themselves, some combination of both may be necessary. For example,
use of growth factor therapy to treat retinal degenerative disease resulted in
unregulated overgrowth of blood vessels resulting in severe disruption of the
normal retinal tissue architecture. The use of neural or retinal stem cells to
treat
retinal degenerative disease may reconstitute neuronal function, but a
functional
vasculature will also be necessary to maintain retinal functional integrity.
Incorporation of cells from a Lin HSCs of the present invention into the
retinal
vessels of rd/rd mice stabilized the degenerative vasculature without
disrupting
retinal structure. This rescue effect was also observed *when the cells were
injected
into P15 rd/rd mice. Since vascular degeneration begins on P16 in rd/rd mice,
this
observation expands the therapeutic window for effective Liri HSC treatment.
Retinal neurons and photoreceptors are preserved and visual function is
maintained
in eyes injected with the Liri HSC of the present invention.
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Adult bone marrow-derived Lin HSCs exert profound vasculo- and
neurotrophic effects when injected intravitreally into mice with retinal
degenerative
disease. This rescue effect persists for up to 6 months after treatment and is
most
efficacious when the Liri HSCs are injected prior to complete retinal
degeneration
(up to 16 days after birth in mice that ordinarily exhibit complete retinal
degeneration by 30 days postnatally). This rescue is observecl in 2 mouse
models
of retinal degeneration and, remarkably, can be accomplished with adult human
bone marrow-derived HSCs when the recipient is an inununodeficient rodent with
retinal degeneration (e.g., the SCID mouse) or when the donor is a mouse with
retinal degeneration. While several recent reports have described a partial
phenotypic rescue in mice or dogs with retinal degeneration after viral based
gene
rescue with the wild type gene (Ali, et al. 2000, Nat Genet 25:306-310;
Takahashi
et al. 1999, J. Virol. 73:7812-7816; Acland et al. 2001, Nat. Genet. 28:92-
95.),
the present invention is the first generic cell-based therapeutic effect
achieved by
vascular rescue. Thus, the potential utility of such an approach in treating a
group
of diseases (e.g., retinitis pigmentosa) with over 100 known associated
mutations is
more practical than creating individual gene therapies to treat each known
mutation.
The precise molecular basis of the neurotrophic rescue effect remains
unknown, but is observed only when there is concomitant vascular
stabilization/rescue. The presence of injected stem cells, per se, is not
sufficient to
generate a neurotrophic rescue and the clear absence of stem cell-derived
neurons
in the outer nuclear layer rules out the possibility that the injected cells
are
transforming into photoreceptors. Data obtained by microarray gene expression
analysis demonstrated a significant up-regulation of genes known to have anti-
apoptotic effects. Since most neuronal death observed in retinal degenerations
is by
apoptosis, such protection may be of great therapeutic benefit in prolonging
the life
of photoreceptors and other neurons critical to visual function in these
diseases.
C-myc is a transcription factor that participates in apoptosis by upregulation
various
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downstream apoptosis-inducing factors. C-myc expression was increased 4.5 fold
in rd/rd mice over wild-type indicating potential involvement in the
photoreceptor
degeneration observed in the rdl/rdl mouse. Mad1 and YY-1, two genes
dramatically upregulated in Lin HSC-protected retinas (Fig. 20, panel A), are
known to suppress the activity of c-myc, thus inhibiting c-myc induced
apoptosis.
Overexpression of Madl has also been shown to suppress Fas-induced activation
of
caspase-8, another critical component of the apoptotic pathway. Upregulation
of
these two molecules may play a role in protection of the retina from vascular
and
neural degeneration by preveinting the initiation of apoptosis that normally
leads to
degeneration in rdlyd mice.
Another set of genes that were greatly upregulated in Lin HSC
protected retinas includes members of the crystallin family (Fig 20, panel B).
Similar to heat-shock and other stress-induced proteins, 'crystallins may be
activated
by retinal stress and provide a protective effect against apoptosis.
Abnormally low
expression of aA-crystallin is correlated with photoreceptor loss in a rat
model of
retinal dystrophy and a recent proteomic analysis of the retina in the rd/rd
mouse
demonstrated induction of crystalline up-regulation in response to retinal
degeneration. Based on our microarray data of EPC-rescued rd/rd mouse retinas,
upregulation of crystallins appear to play a key role in EPC mediated retinal
neuroprotection.
Genes such as c-myc, Mad1., Yx-1 and the crystallins are likely to be
downstream mediators of neuronal rescue. Neurotrophic agents can regulate anti-
apoptotic gene expression, although our microarray analysis of retinas rescued
with
mouse stem cells did not demonstrate induction of increased levels of known
neurotrophic factors. Analysis of human bone marrow-derived stem cell-mediated
rescue with human specific chips did, on the other hand, demonstrate low, but
significant increases in the expression of multiple growth factor genes.
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The upregulated genes include several members of the fibroblast
growth factor family and otoferlin. Mutations in the otoferlin gene are
associated
with genetic disorders leading to deafness due to auditory neuropathy. It is
possible that otoferlin production by injected Lin HSCs contributes to the
prevention of retinal neuropathy as well. Historically, it has long been
assumed
that vascular changes observed in patients and animals with retinal
degeneration
were secondary to decreased metabolic demand as the photoreceptors die. The
present data indicate that, at least for mice with inherited retinal
degeneration,
preserving normal vasculature can help maintain components of the outer
nuclear
layer as well. Recent reports in the literature would support the concept that
tissue-
specific vasculature has trophic effects that go beyond that expected from
simply
providing vascular "nourishment." For example, liver endothelial cells can be
induced to produce, after VEGFRI activation, growth factors critical to
hepatocyte
regeneration and maintenance in the face of hepatic injury (LeCouter et al.
2003,
Science 299:890-893).
Similar indicative interactions between vascular endothelial cells and
adjacent hepatic parenchymal cells are reportedly involved in liver
organogenesis,
well before the formation of functional blood vessels. Endogenous retinal
vasculature in individuals with retinal degeneration may not facilitate so
dramatic a
rescue, but if this vasculature is buttressed with endothelial progenitors
derived
from bone marrow hematopoietic stem cell populations, they may make the
vasculature more resistant to degeneration and at the same time facilitate
retinal
neuronal, as well as vascular, survival. In humans with retinal degeneration,
delaying the onset of complete retinal degeneration may provide years of
additional
sight. The animals treated with the Lin HSCs of the present invention had
significant preservation of an ERG, which may be sufficient to support vision.
Clinically, it is widely appreciated that there may be substantial loss of
photoreceptors and other neurons while still preserving functional vision. At
some
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point, the critical threshold is crossed and vision is lost. Since nearly all
of the human
inherited retinal degenerations are of early, but slow, onset, an individual
with retinal
degeneration can be identified and treated intravitreally with a graft of
autologous
bone marrow stem cells of the invention to delay retinal degeneration and
concomitant loss of vision. To enhance targeting and incorporation of the stem
cells
of the invention, the presence of activated astrocytes is desirable (Otani et
al. 2002,
Nat. Med. 8: 1004-1010); this can be accomplished by early treatment when
there is
an associated gliosis, or by using a laser to stimulate local proliferation of
activated
astrocytes. Optionally, ex vivo transfection of the stem cells with one or
more
neurotrophic substances prior to intraocular injection can be used to enhance
the
rescue effect. This approach can be applied to the treatment of other visual
neuronal
degenerative disorders, such as glaucoma, in which there is retinal ganglion
cell
degeneration.
The Lin HSC populations of the present invention contain a
population of EPC that can promote angiogenesis by targeting reactive
astrocytes
and incorporate into an established template without disrupting retinal
structure.
The Liri HSC of the present invention also provide a surprising long-term
neurotrophic rescue effect in eyes suffering from retinal degeneration. In
addition,
genetically modified, autologous Liri HSC compositions containing EPC 'can be
transplanted into ischemic or abnormally vascularized eyes and can stably
incorporate into new vessels and neuronal layers and continuously deliver
therapeutic molecules locally for prolonged periods of time. Such local
delivery of
genes that express pharmacological agents in physiologically meaningful doses
represents a new paradigm for treating currently untreatable ocular diseases.
Photoreceptors in the normal mouse retina, for example, are
predominantly rods, but the outer nuclear layer observed after rescue with Lin-
HSCs
of the invention contained predominantly cones. Most inherited human retinal
degenerations occur as a result of primary rod-specific defects, and loss of
the cones
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is believed to be secondary to rod dysfunction, which is likely related to the
loss of
some trophic factor expressed by rods. The present method of inducing cone
survival
in the face of rod/retinal degeneration facilitated by Lin-HSC, affords a way
to better
preserve the cone-dominated human macula in diseases such as retinitis
pigmentosa.
Numerous variations and modifications of the embodiments
described above may be effected without departing from the spirit and scope of
the
novel features of the invention. No limitations with respect to the specific
embodiments illustrated herein are intended or should be inferred.
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