Vision Loss

Coding Dimension ID: 
325
Coding Dimension path name: 
Vision Loss

Human retinal progenitor cells as candidate therapy for retinitis pigmentosa

Funding Type: 
Early Translational II
Grant Number: 
TR2-01794
ICOC Funds Committed: 
$4 738 251
Disease Focus: 
Vision Loss
Stem Cell Use: 
Adult Stem Cell
oldStatus: 
Closed
Public Abstract: 
The targeted disease is retinitis pigmentosa (RP), is a severe form of blindness that runs in families. This disease is not overly common, yet represents an attainable near term target for stem cell therapy for a number of reasons: 1) RP destroys the light detecting cells of the retina but generally leaves the rest of the visual system and body unharmed, so the clinical goal is circumscribed; 2) RP is prototypical of degenerations of the nervous system, so a cure for this less common disease would accelerate progress towards new therapies for a range of more familiar conditions; 3) scientific research has shown that degenerating rods and cones can be spared in animals by transplanting particular types of stem cells, so the scientific feasibility of treating RP in this way has already been established in principle. The therapeutic approach is to save the light sensing cells of the eye (rod and cone photoreceptors) in people going blind using a type of stem cell obtained from the immature retina, but not from early embryos. These particular stem cells from the retina, known as progenitor cells, are capable of rescuing photoreceptors from degeneration following transplantation to the eye. These same cells are also highly efficient at becoming rod photoreceptors and this provides another more sustained pathway by which they preserve the crucial cone photoreceptors. In addition, there is evidence that the stem cells themselves might become functional photoreceptors and thereby stabilize the retina by directly replacing the dying cells in the patient’s eye. Thus, transplanted stem cells could treat the targeted disease of RP in multiple ways simultaneously. Importantly, there are a host of reasons why clinical trials in the eye are easier and safer than most locations in the body. The eye is an important proving ground for stem cell-based therapies and provides a stepping stone to many otherwise incurable diseases of the brain and spinal cord.
Statement of Benefit to California: 
Benefits to the state of California and its citizens are both direct and indirect. The direct benefit is medical in that there is currently no cure or established treatment for the individuals and families that suffer from the dreadful hereditary blindness known as retinitis pigmentosa. In addition, there are many people in California and throughout the world that suffer from degenerative diseases of the retina and central nervous system that could benefit from further development and alternate applications of the type of stem cell therapy proposed in the current application. The rapid progress that could be achieved via this proposal would help legitimize the use of stem cells and should thereby accelerate the development of stem cell-based therapeutics for a wide range of other diseases. In so doing there would be an indirect benefit to California by making our state a focal point for stem cell breakthroughs. This would increase medical capabilities, strengthen the [REDACTED], and energize local biotechnology companies with outside investment and a payoff in jobs and tax revenues.
Progress Report: 
  • At the end of Year 1 of the grant period, our team has made substantial progress and achieved quite a few of the milestones initially established for the entire 3 year period. A retinal cell bank has been established for research purposes and, in addition, initial clinical-grade cell production is now under way with the target of generating 3 clinical cell banks. We have shown that our human cells are able to help blind rats to see following transplantation to the eye. We have developed a range of methods to help prove the safety of our cells, both before and after transplantation, with definitive long term tests results to be obtained over the next few months. We have begun to unravel the molecular genetics of the cell and are specifically investigating what give them the ability to preserve vision in the face of progressive blindness. In summary, work is advancing rapidly and ahead of schedule, consistent with a realistic, achievable biological strategy. On behalf of the patients who we know are depending upon us, our team is committed to seeing this technology into the clinic in the shortest possible timeline.

Development of a Stem Cell-based Transplantation Strategy for Treating Age-related Macular Degeneration

Funding Type: 
Early Translational I
Grant Number: 
TR1-01272
ICOC Funds Committed: 
$5 503 069
Disease Focus: 
Vision Loss
Stem Cell Use: 
Adult Stem Cell
iPS Cell
oldStatus: 
Closed
Public Abstract: 
Age related macular degeneration (AMD) is a blinding disease of the elderly affecting nearly one in three individuals over the age of 75. Central vision is lost in AMD, severely impairing the ability to read, watch television, or drive. The epicenter of AMD is the retinal pigment epithelium (RPE), a single layer of cells in the retina adjacent to the photoreceptor cells. A recent breakthrough in AMD research showed that this disease is caused in about 50% of cases by the innate immune system (complement system) inappropriately attacking RPE cells. Specifically, AMD results when regulators of the complement system, which normally protect the RPE, are weakened by mutations. This sickens and later kills the RPE, causing secondary degeneration of photoreceptors in the central retina (macula). The goal of this proposal is to develop a strategy for transplanting stem-cell derived RPE cells into the eyes of patients with AMD. In the past, transplantation of RPE cells from postmortem donors yielded encouraging initial therapeutic effects that subsequently failed due to immune rejection. Current stem-cell technology offers the opportunity to avoid this complication. We plan to generate functional RPE cells from stem cells of the ciliary margin zone (CMZ) in the eye, or pluripotent stem cells induced from skin fibroblasts (iPS cells) taken from the same AMD patient who will later receive the induced RPE cells as a transplant. The study of inherited blindness has benefited greatly from mouse genetic models, where new potential therapies can be tested and developed. One aim of this proposal is to produce RPE cells from mouse and human CMZ- and iPS-cell precursors. To establish that these cells are functional, we will test for two hallmarks of a fully differentiated RPE: (i) the ability to convert vitamin A into visual chromophore for photoreceptor-opsin pigments, and (ii) the ability to phagocytose photoreceptor outer-segments. In a later aim we will transplant these induced RPE cells into the eyes of two genetic “knockout” mice that lack the ability to synthesize visual chromophore. We will test for rescue of the biochemical defects, and correction of the blindness in these mutant mice. In another experiment, we will add to the induced RPE cells a gene that protects from inappropriate complement activation. These cells will be transplanted into the eyes of two other knockout mouse-models of AMD that exhibit abnormal activation of the complement system. We will study these mice to establish correction of the immune defect. Finally, we will test the safety of CMZ- and iPS-derived RPE cells by transplanting them into immune-deficient mice to confirm no tumor formation. At the end of the grant period, we expect to have a new and well-tested stem-cell based transplantation strategy that will be ready for phase-one clinical trials in AMD patients.
Statement of Benefit to California: 
This proposal is to develop a stem-cell based transplantation approach for treating age-related macular degeneration (AMD). AMD is a severe and common disease of the elderly that causes central blindness. The prevalence of AMD increases with advancing age. By 75 years, approximately one in three individuals have some degree of visual loss due to AMD. Thus AMD is significantly more prevalent than Alzheimer disease. Patients with AMD lose the ability to drive, read, watch TV, and recognize faces. With advancing visual impairment, AMD patients lose the ability to care for themselves and others. Thus, AMD imposes a large social and economic burden on our society. As the population in California ages, this burden is expected to increase. The stem-cell based transplantation strategy in this proposal offers the real potential of slowing or arresting the progression of blindness in AMD patients. This alone would represent an important benefit to the people of California. Further, the project would advance innovative technology in stem cell therapy. This technology has application to other neurodegenerative diseases. The project will train new stem-cell researchers in California. As the project enters the clinical phase, it will engage new scientists and physicians and attract funding by the federal government. Further, the opportunity to treat a hugely prevalent disease like AMD will undoubtedly attract biotechnology investment in California. This stem-cell based transplantation approach to treat a major disease like AMD is well-aligned with the broad mission of CIRM and the objectives of the Early Translational Research Award program.
Progress Report: 
  • The broad goal of this project is to develop a stem-cell derived replacement for RPE cells in the eye that die in patients with age-related macular degeneration (AMD). Since RPE cells are often genetically defective in AMD, we will correct this defect in the stem-cell derived RPE cells before transplanting them into patients. These transplanted cells will express specific proteins that will protect them from being attacked by the innate immune system. During the first year of funding we made excellent progress toward this goal. We learned how to generate RPE cells from mouse and human stem cells of various sources. We prepared all the DNA constructs that will be required to protect the transplanted RPE cells from attack by the innate immune system. We also developed a new approach for injecting RPE cells into the correct part of the mouse eye (subretinal space) without damaging other parts of the retina. We are enthusiastic to continue our work on this exciting project.
  • The broad goal of this project is to develop a stem-cell derived replacement for retinal pigment epithelial (RPE) cells in the eye, which die in patients with age-related macular degeneration (AMD). Since RPE cells are often genetically defective in AMD, we will correct this defect in the stem-cell derived RPE cells before transplanting them into patients. These transplanted cells will express specific proteins that will protect them from being attacked by the innate immune system. During our second year of funding, we transplanted human stem-cell derived RPE cells into the eyes of mice that are blind due to a genetic defect in the rpe65 gene. We showed that the human cells integrated into the RPE layer of these mice. Further, we demonstrated that the transplanted cells partially rescued the blindness in rpe65 / mice. We also generated and tested the recombinant viruses that will protect RPE cells from attack by the innate immune system. We are on schedule to complete the planned studies for this project during the final year of funding.
  • This project is to develop a new treatment for age-related macular degeneration (AMD) based on transplantation of retinal pigment epithelial (RPE) cells into the subretinal space of a patient’s eyes. These RPE cells are induced from stem cells collected from the same patient, to avoid the problem of immune rejection. AMD is primarily an inflammatory disorder caused by inappropriate attack of RPE cells by the complement system. Accordingly, negative regulators of complement activation will be expressed in the stem-cell derived RPE cells by viral transduction. We explored two sources of stem cells that can be collected from a patient: embryonic stem cells and induced pluripotent stem (iPS) cells from skin fibroblasts. We successfully programed these stem cells into fully functional RPE cells. Our team has extensive experience with the biochemistry and cell biology of the RPE. We used “knockout” mouse models with mutations in RPE genes to test the efficiency of RPE-cell transplantation. Next, we planned to test the strategy of protecting RPE cells from complement attack by over-expressing complement negative-regulatory factors. We tested the long-term viability of induced RPE cells, and rule-out tumorgenicity by transplanting these cells into the eyes of severe-combined immunodeficient mice.

Autologous Retinal Pigmented Epithelial Cells Derived from Induced Pluripotent Stem Cells for the Treatment of Atrophic Age Related Macular Degeneration

Funding Type: 
Early Translational I
Grant Number: 
TR1-01219
ICOC Funds Committed: 
$5 945 738
Disease Focus: 
Aging
Vision Loss
Stem Cell Use: 
iPS Cell
Cell Line Generation: 
iPS Cell
oldStatus: 
Closed
Public Abstract: 
The leading cause of visual loss in Americans over the age of 65 is age related macular degeneration (AMD) which occurs in both a "wet" and a "dry" form. Both forms of the disease are associated with loss of cells called retinal pigmented epithelium (RPE) which can lead to profound loss of central vision. Currently, there is no treatment that will reverse or prevent the loss of these cells and associated blindness. Nutritional supplementation with antioxidants, macular pigments and long chain PUFAs was shown to slightly reduce disease progression but the clinical reality is that 6-8% of people over the age of 75 are legally blind from this disease. Others have observed that RPE cells can be obtained from human embryonic stem cells and that these cells may be transplanted into eyes of animals with diseases that resemble human macular degeneration with RPE dysfunction. Potential problems with this approach to treating humans with this disease include the possibility that the embryonic stem cells from which the RPE are derived may be carried over into the eye and form tumors or elicit an immune response in the recipient eye since the cells are not from the same individual receiving the transplant. Recent advances in stem cell biology now make it possible to induce the formation of pluripotent stem cells (iPSC) from adult, or somatic, tissues of individuals; these cells, in turn, may be stimulated to form RPE cells. Thus, it would be possible to produce RPE cells from the skin or hair of the same individual who would receive the transplant. In order to do this, current technology requires the use of lentiviral vectors that integrate into the genetic material of the recipient cells. In addition, the efficiency with which the iPSC are formed is not very high and to produce these cells, and the derived RPE cells, it is necessary to use "feeder" cell layers and molecules derived from animals. In this research proposal, we will take advantage of novel chemistries and molecular biological techniques to develop iPSC from somatic tissues of patients with AMD and produce RPE cells that could then be used to replace damaged tissue in these patients' eyes. Using small molecules obtained from unique chemical libraries, we will enhance the efficiency of iPSC and RPE production from somatic cells and eliminate the use of animal cell "feeder" layers and supplements. Furthermore, we will use a unique procedure ("an episomal vector") to produce iPSC from somatic cells that does not require the use of potentially dangerous viruses and permanently integrated genetic material. If we are successful, a patient with early signs of AMD could come into their ophthalmologist's office, have a skin biopsy performed that could be used to obtain RPE cells that could then be transplanted into that individual's eye at a later date when their own RPE begin to degenerate, but before they have visual loss.
Statement of Benefit to California: 
As the population ages, individuals are prone to develop diseases of aging that significantly impact the quality of life in the "golden years." Foremost among these diseases is age related macular degeneration (AMD), a disease that affects the tissue in the back of the eye (the retina) used for vision. The central portion of this tissue, called the macula, is most affected in AMD and can lead to loss of fine, or "reading", vision. Vision loss occurs from two principal forms of the disease; the "wet" type involving the abnormal growth of new blood vessels and the "dry" type, involving degeneration and scarring of the macula. In both forms, special types of cells under the retina, called retinal pigmented epithelial (RPE) cells degenerate and contribute to the loss of vision. It is estimated that 15-20 million Americans over the age of 65 have AMD and 10-15% of these have vision loss secondary to the disease. Geographic atrophy (the dry type) affects 0.81% of the US population, equivalent to a prevalence of approximately 300,000 in California. Another 6.12% of the population (2.2 million Californians) suffer from early-stage AMD which puts them at high risk for developing geographic atrophy within 5 years. Currently there are some drugs available to help a certain portion of patients with the "wet" form of the disease, but there are no treatments for the "dry" or atrophic, form of the disease. We propose the use of transplants of healthy RPE cells into the eyes of patients with the atrophic form of AMD; these cells would be derived from the patients own skin or hair cells after inducing the production of pluripotent stem cells which could then be stimulated to become RPE cells. If successful, this approach would potentially provide a treatment for the leading cause of vision loss in Californians over the age of 65 with cells derived from their own tissue, avoiding potential complications associated with (1) repeated injections into the eye, (2) using cells from animals or other individuals and (3) deriving cells for transplant that have been exposed to animal cells or molecules and viral genetic material. Preserving vision in the elderly population not only would immensely improve the quality of life for these individuals, but it would also greatly facilitate their ability to function independently and productively.
Progress Report: 
  • The recent development of technologies capable of producing induced pluripotent stem (iPS) cells from adult somatic tissues may permit their use to generate autologous retinal pigment epithelium (RPE) grafts for the treatment of diseases like age-related macular degeneration. However, conventional reprogramming techniques are based on random genomic integration of four transcription factors with oncogenic potential. To minimize the risk of tumor formation, the use of iPS cells reprogrammed with a reduced number of these factors would be advantageous. We therefore evaluated the differentiation capacity of iPS cells generated from primary human epidermal keratinocytes by lentiviral transduction with only two or one factor (Oct4 and Klf4 or Oct4 only, respectively) and additional treatment with small molecules. Human iPS cells reprogrammed by conventional methods were used for comparison. Four factor-, two factor-, and one factor-derived iPS cells could be differentiated into cells that expressed RPE-specific markers (e.g., bestrophin, CRALBP, RPE65, tyrosinase). Moreover, these cells exhibited morphological and functional features characteristic of RPE cells such as formation of epithelial monolayers with intercellular tight junctions, homogenous polygonal morphology, pronounced pigmentation, phagocytosis of photoreceptor outer segments, and vectorial apical-to-basolateral fluid transport. Furthermore, we have demonstrated that the 1-factor iPSC-derived RPE cells, when injected into a rodent model of atrophic macular degeneration, could establish grafts of RPE and prevent the degeneration of photoreceptors (neurons) in this model. Thus, we demonstrate that human iPS cells generated by novel reprogramming techniques can be differentiated into cells with RPE-specific morphology, gene/protein expression and function. Compared to conventional iPS cells, these cells may be superior for clinical application due to the elimination of oncogenic reprogramming factors and, ultimately, retroviral transfection vectors.
  • The recent development of technologies capable of producing induced pluripotent stem (iPS) cells from adult somatic tissues may permit their use to generate autologous retinal pigment epithelium (RPE) grafts for the treatment of diseases like age-related macular degeneration. However, conventional reprogramming techniques are based on random genomic integration of four transcription factors with oncogenic potential. To minimize the risk of tumor formation, the use of iPS cells reprogrammed with a reduced number of these factors would be advantageous. We therefore evaluated the differentiation capacity of iPS cells generated from primary human epidermal keratinocytes by lentiviral transduction with only two or one factor (Oct4 and Klf4 or Oct4 only, respectively) and additional treatment with small molecules. Human iPS cells reprogrammed by conventional methods were used for comparison. Four factor-, two factor-, and one factor-derived iPS cells could be differentiated into cells that expressed RPE-specific markers (e.g., bestrophin, CRALBP, RPE65, tyrosinase). Moreover, these cells exhibited morphological and functional features characteristic of RPE cells such as formation of epithelial monolayers with intercellular tight junctions, homogenous polygonal morphology, pronounced pigmentation, phagocytosis of photoreceptor outer segments, and vectorial apical-to-basolateral fluid transport. Furthermore, we have demonstrated that the 1-factor iPSC-derived RPE cells, when injected into a rodent model of atrophic macular degeneration, could establish grafts of RPE and prevent the degeneration of photoreceptors (neurons) in this model. Thus, we demonstrate that human iPS cells generated by novel reprogramming techniques can be differentiated into cells with RPE-specific morphology, gene/protein expression and function. Compared to conventional iPS cells, these cells may be superior for clinical application due to the elimination of oncogenic reprogramming factors and, ultimately, retroviral transfection vectors.
  • The recent development of technologies capable of producing induced pluripotent stem (iPS) cells from adult somatic tissues may permit their use to generate autologous retinal pigment epithelium (RPE) grafts for the treatment of diseases like age-related macular degeneration. However, conventional reprogramming techniques are based on random genomic integration of four transcription factors with oncogenic potential. To minimize the risk of tumor formation, the use of iPS cells reprogrammed with a reduced number of these factors would be advantageous. We therefore evaluated the differentiation capacity of iPS cells generated from primary human epidermal keratinocytes by lentiviral transduction with only two or one factor (Oct4 and Klf4 or Oct4 only, respectively) and additional treatment with small molecules. Human iPS cells reprogrammed by conventional methods were used for comparison. Four factor-, two factor-, and one factorderived iPS cells could be differentiated into cells that expressed RPE-specific markers (e.g., bestrophin,CRALBP, RPE65, tyrosinase). Moreover, these cells exhibited morphological and functional features characteristic of RPE cells such as formation of epithelial monolayers with intercellular tight junctions, homogenous polygonal morphology, pronounced pigmentation, phagocytosis of photoreceptor outer segments, and vectorial apical-to-basolateral fluid transport. Furthermore, we have demonstrated that the 1-factor iPSC-derived RPE cells, when injected into a rodent model of atrophic macular degeneration, could establish grafts of RPE and prevent the degeneration of photoreceptors (neurons) in this model. Thus, we demonstrate that human iPS cells generated by novel reprogramming techniques can be differentiated into cells with RPE-specific morphology, gene/protein expression and function. Compared to conventional iPS cells, these cells may be superior for clinical application due to the elimination of oncogenic reprogramming factors and, ultimately, retroviral transfection vectors.
  • The recent development of technologies capable of producing induced pluripotent stem (iPS) cells from adult somatic tissues may permit their use to generate autologous retinal pigment epithelium (RPE) grafts for the treatment of diseases like age-related macular degeneration. However, conventional reprogramming techniques are based on random genomic integration of four transcription factors with oncogenic potential. To minimize the risk of tumor formation, the use of iPS cells reprogrammed with a reduced number of these factors would be advantageous. We therefore evaluated the differentiation capacity of iPS cells generated from primary human epidermal keratinocytes by lentiviral transduction with only two or one factor (Oct4 and Klf4 or Oct4 only, respectively) and additional treatment with small molecules. Human iPS cells reprogrammed by conventional methods were used for comparison. Four factor-, two factor-, and one factorderived iPS cells could be differentiated into cells that expressed RPE-specific markers (e.g., bestrophin,CRALBP, RPE65, tyrosinase). Moreover, these cells exhibited morphological and functional features characteristic of RPE cells such as formation of epithelial monolayers with intercellular tight junctions, homogenous polygonal morphology, pronounced pigmentation, phagocytosis of photoreceptor outer segments, and vectorial apical-to-basolateral fluid transport. Furthermore, we have demonstrated that the 1-factor iPSC-derived RPE cells, when injected into a rodent model of atrophic macular degeneration, could establish grafts of RPE and prevent the degeneration of photoreceptors (neurons) in this model. We have completed a study of the long-term effects of these cells injected into rodent eyes and observe continued trophic rescue effects and lack of any adverse events for up to two years post-injection. Thus, we demonstrate that human iPS cells generated by novel reprogramming techniques can be differentiated into cells with RPE-specific morphology, gene/protein expression and function. Compared to conventional iPS cells, these cells may be superior for clinical application due to the elimination of oncogenic reprogramming factors and, ultimately, retroviral transfection vectors.

Therapeutic potential of Retinal Pigment Epithelial cell lines derived from hES cells for retinal degeneration.

Funding Type: 
SEED Grant
Grant Number: 
RS1-00222
ICOC Funds Committed: 
$684 322
Disease Focus: 
Aging
Vision Loss
Stem Cell Use: 
Embryonic Stem Cell
oldStatus: 
Closed
Public Abstract: 
Retinal degeneration represents a group of blinding diseases that are increasingly impacting the health and well being of Californians. It is estimated that by 2020, over 450,000 Californians will suffer from vision loss or blindness due to the age-related macular degeneration (AMD), the most common cause of retinal degeneration diseases in the elderly. Furthermore, retinitis pigmentosa is the leading cause of inherited blindness in younger people. Currently there are no cures for these diseases. A layer of cells at the back of the eye called the retinal pigment epithelium (RPE), provide support, protection, and nutrition to the light sensitive retina, and cooperate with other retinal cells to maintain normal visual function. The dysfunction and/or loss of these RPE cells play a critical role in the development of the previously described blinding diseases. We suggest that effective treatment of retinal degeneration could be achieved by the proper replacement of damaged RPE and retinal cells with healthy ones. However, lack of the reasonable supply of healthy human eye cells hampers the application of this therapeutic approach. Recent advances in knowledge and technology of embryonic stem cells brings new hope for the development of cell replacement treatment. Embryonic stem (ES) cells are capable of unlimited self-replication and production of different cell types. RPE cells derived from human ES cells (hES-RPE) are a potentially unlimited resource for the cell replacement approach. We hypothesize that the dysfunction and/or loss of RPE can be replenished and restored through the transplantation of functionally polarized RPE monolayers derived from human embryonic stem cells, and this transplantation can cure the retinal degeneration diseases caused by RPE dysfunction.We propose to: 1. Derive RPE cells from human ES cells; 2. Establish and characterize the functionally mature or polarized monolayer of hES-RPE cells that will be suitable for transplantation; 3. Rescue the retinal degeneration phenotype through the transplantation of functionally mature or polarized monolayer of hES-RPE cells in animal models. Our goal is to determine the feasibility of treating the retinal degeneration diseases caused by RPE dysfunction through the transplantation of a monolayer of polarized hES-RPE cell sheet. The knowledge and technology from our research can be used to develop new treatments for human retinal degeneration diseases.
Statement of Benefit to California: 
Age-related macular degeneration (AMD) is the leading cause of severe vision loss or blindness among the elderly, and currently no cure for this disorder exists. Based on the fact that California is the most populated state, and that the population continues to age, it is estimated that over 450,000 of Californians will suffer from AMD with severe vision impairment by 2020. Studies have shown that the devastating consequences of AMD include the progressive loss of independence and productivity, and increased risks of falls, fractures, and depression among diseased population. So this is not only a problem of the individual quality of life, but also an issue of increasing public health burden and concern. In this study we will test the feasibility of treating AMD and other retinal degenerative diseases through the transplantation of human embryonic stem cells that have been treated to differentiate into retinal pigment epithelial cells (RPE); the cells known to primarily degenerate or die in AMD. If our experimentation with RPE replacement therapy is successful in animal models, the knowledge and techniques can be quickly used to develop novel treatments for human diseases. Hundreds of thousands of Californians with AMD and other retinal degeneration diseases could benefit from our research for better quality of life with reduced morbidity. The California economy may significantly benefit from this work through potential reduced costs for health care, social welfare, and the loss of labor force.
Progress Report: 
  • It is estimated that by 2020, over 450,000 Californians will suffer from vision loss or blindness due to the age-related macular degeneration (AMD), the most common cause of retinal degeneration in the elderly. A layer of cells at the back of the eye called the retinal pigment epithelium (RPE), provides support, protection, and nutrition to the light sensitive retina, and cooperates with other retinal cells to maintain normal visual function. The dysfunction and/or loss of these RPE cells play a critical role in the development of dry AMD, the most common form of that disease. RPE cells derived from human ES cells (hES-RPE) are a potentially unlimited resource for cell replacement therapy.
  • During this grant period we were able to develop methods to reproducibly derive RPE cells from established human ES (hES) cell lines.
  • Normal RPE cells have a polarized appearance, meaning that they have specialized appearances and functions on the top (retinal facing) and bottom of the cells. We were then able to induce the hES-derived RPE to develop a polarized appearance very similar to that found in the normal eye. These cells had specialized characteristics that were remarkable similar to normal RPE and showed ability to function like normal RPE cells. We then developed sheets of hES-derived RPE on substrates that could be used for surgical implantation into animal eyes.
  • We then performed studies to establish appropriate animal models in which to test the ability of hES-derived RPE to prevent or slow retinal degeneration in animal models that have some features of human AMD. We were not able to use standard mouse models of AMD because mouse eyes are too small to perform the surgical implantation of polarized RPE. We first looked at a rabbit model of RPE degeneration induced by a toxin (sodium iodate). We were able to establish reproducible RPE degeneration in these animals but whenever we tried to implant hES-derived RPE under the retinas of these animals, the RPE cells did not survive. We believe that the toxin that was used to induce this model was being taken up by the transplanted cells resulting in their death. We then tested a genetic model of retinal degeneration in rats (RCS rat). We were able to demonstrate reproducible retinal degeneration in these animals. When we transplanted hES-derived RPE under the retinas of these animals, we were able to show that the RPE were indeed human in origin and that they were able to survive for at least several weeks after transplantation. Importantly, we were able to show that in the areas where hES-derived RPE were transplanted, there was less retinal degeneration than in the areas in which there was no transplantation or "sham" transplantation.
  • Thus, in conclusion, we were able to show (1) the reproducible culture of RPE cells from human ES cell lines, (2) that these hES-derived RPE had the appearance and functional characterisitics of human RPE and could be grown on substrates as sheets or polarized cells, and (3) that when these sheets of polarized hES-derived RPE were implanted under the retinal of rats with retinal degeneration, that they were able to survive and showed the ability to slow the progression of retinal degeneration in these animals.
  • The results of this study suggest that hES cells may be an unlimited source of RPE cells suitable for transplantation into eyes with retinal degeneration and that subretinal implantation of polarized hES-derived RPE may represent a novel therapy for dry AMD.

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