The goal of this research is to create a collection of iPSCs reprogrammed from a unique source - the adult human retinal pigment epithelium (RPE) - and use this to create a model of dry age-related macular degeneration (AMD), one of the most prevalent neurodegenerative diseases of aging. AMD is the leading cause of blindness in patients over age 50 and affects over 11 million patients, with vision loss in the macula, the center of the retina, needed for high acuity vision (reading, writing, recognizing faces). There ar no disease-altering therapies for AMD. A stem cell-derived RPE intraocular transplantation approach is in clinical trials, but this might not be an option for many elderly patients. A better understanding of the disease process could lead to new therapeutic options for this highly prevalent and devastating condition. Dry AMD is imperfectly modeled by murine species, which do not have a macula, or by transformed cell lines such as ARPE-19 that do not express key phenotypic features of human RPE. Human iPSCs can produce cells with the salient properties of native RPE. We propose that iPSC-derived RPE can form the basis of a valuable model of dry AMD. Several GWAS studies have demonstrated gene linkages for AMD, making it possible to screen iPSC lines for these SNPs to obtain a profile of known genetic risk. In addition a number of environmental factors have been shown to increase the risk of dry AMD, including the widely acknowledged factor, chronic oxidative stress. The macula RPE is exposed to an extraordinary level of oxidative stress due to focused light and to the diurnal phagocytosis of cone photoreceptor outer segments which contain very high levels of oxidized products. This stress causes significant changes within the RPE cells, resulting in inefficient phagocytosis and metabolism, and in some individuals, to the build-up of material into large excrescences that are deposited under the RPE causing inflammatory reactions and further damage - the hallmark of AMD is these 'drusen'deposits. Consequently, decades of chronic stress lead to alterations in the RPE, providing a strong rationale for producing iPSCs from this disease target tissue itself.
In aim 1 we will produce RPE cells from fetal, normal aged and AMD patient eyes, and from these generate iPSC lines that will be documented for AMD-related SNPs.
In aim 2 we will differentiate these cells into RPE and characterize the cells with a comprehensive phenotypic and functional analysis.
This aim will be carried out in collaboration with Sheldon Miller at NEI, an expert in RPE characterization.
In aim 3, we will determine how these different lines respond to chronic oxidative stress in a novel model for dry AMD we developed for primary human RPE that measures production of several drusen proteins. Thus we will create a valuable iPSC-RPE based model for dry AMD. By comparing the responses of young, normal aged and AMD RPE-iPSC-RPE from several individuals, we will reveal changes associated with normal aging and macula disease. These CNS-derived iPSCs could be valuable for modeling other CNS aging diseases.
Age-related macular degeneration is the leading cause of blindness in the elderly with over 11 million sufferers in the US alone and no effective treatments. Animal models do not have the correct retinal anatomy to model this disease, so alternatives are actively being sought. We propose to use the new human induced pluripotent stem cell (iPSC) technology to create a collection of young, old and AMD human iPSC lines, and use these to develop a novel model for AMD to accelerate progress towards therapeutics. This 'disease in a dish'model uses the relevant human retinal cells throughout the process, and therefore can help reveal the molecular pathways that decline with aging and that underlie AMD, a prevalent, devastating age-related neurodegenerative disease.