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.
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.
SYNOPSIS: David Hinton at the University of Southern California proposes to grow retinal pigment epithelium (RPE) cells from NIH-approved hESC cell lines, defining the optimal conditions for definitive differentiation of hESCs into RPE, to establish monolayers of such cells in culture, and subretinal transplantation of polarized sheets of the cells into animal models (the Royal College of Surgeon model). The work will be carried out in collaboration with the laboratory of Martin Pera who has experience and facilities for hESC work. The applicant is supported by the NIH for his work with grants to study RPE cells in proliferative vitreoretinopathy and also demyelinating diseases.
SIGNIFICANCE AND INNOVATION: While not particularly original or novel, this work nevertheless is unique. No other laboratory in the world has the experience and the capability of this laboratory to achieve the goal of defining the culture conditions needed to generate sheets of retinal pigmented epithelial cells and testing these in a well-defined animal model of macular degeneration.
Previous work has shown that RPE colonies arise in human ES cell cultures under differentiating conditions. These cells have been transplanted into animal models of RPE degeneration and show some ability to preserve the photoreceptors. The PI argues that these previous studies have not provided definitive proof that the RPE derived form ES cells functions in vivo as the normal RPE would, and instead proposes that the transplant of functionally polarized monolayers of RPE will be more effective. The overall strategy is not too innovative, since most of what is proposed has already been carried out by Lanza's group. However, the innovative part of this proposal is to culture the ES cell derived RPE cells onto biodegradeable polymers and then use these for transplantation.
STRENGTHS: The important problem of blindless and macular degeneration addressed by this approach. The set of experiments proposed are focused and feasible and are very likely to succeed. The PI is experienced and productive and has a track record in successful projects. The PI and collaborators (Pera) already have derived RPE cell lines from human ES cells. They thus have something to work with for the next experiments. The PI has extensive experience with culture of RPE cells, including the functional characterization of these cells in vitro.
WEAKNESSES: Much of the work has already been achieved in mouse ES cell lines by the applicant and other investigators. One wonders why this has not been funded by the NIH since it utilizes NIH-approved cell lines.
The surgery required for transplantation of an RPE sheet into the subretinal space of a rat eye is likely to be very difficult. It is not clear what measures of graft function will likely discriminate between the sheet transplant and the dissociated cell transplant. In most cases, the problem with dissociated cells is that they do not adhere well to a pathological (ie. AMD) Bruch's membrane. Can this be assessed with the sheet transplants? How will the dissociated cells and sheet be compared to test the hypothesis? Some additional information about the measures for comparison of the sheet and dissociated cell transplants would be very helpful.
DISCUSSION: Besides perhaps Lanza's group at ACT, no other lab in the world has the expertise to define these culture conditions. They have enlisted help from Martin Pera to make these cells, and they are thinking appropriately about the yield. Other labs are gearing up for transplantation studies, and the novelty in this proposal is the use of RPE sheets in the transplant because RPE are a monolayer in the eye. Although the comparison measures are not well described, the PI intends to compare the transplantation of sheets to single cells. The transplantation of sheets is expected to be tricky, and not many details were provided in the application. While not terribly innovative, these are the right experiments to move the field forward and they will produce useful data.
PROGRAMMATIC DISCUSSION: It was proposed that this application be given special consideration if additional funding becomes available based on: 1) no other eye-related research application is in 'recommended to be funded' pool and 2) this was the top-scoring application for scientific merit of research pertaining to eye-related applications.