Retinal Pigment Epithelium Derived from Human Embryonic Stem Cells
The long-term objective of this proposal is to develop applications of human embryonic stem (hES) cells in the treatment of eye diseases, including Age-Related Macular Degeneration, one of the leading causes of human blindness. This disease, as well as other retinal degenerations, is thought to involve the death of the retinal pigmented epithelium (RPE), a layer of pigmented cells in the back of the eye that nourish the photoreceptors of the retina. Preliminary work has shown that hES cells can differentiate into RPE-like cells, so a possible cellular therapy could involve transplantation of these cells in areas where native RPE has been lost. However, there is much to do before it is safe to begin human clinical trials with these cells. Currently only small numbers of cells can be produced, and it is not yet clear if they can fulfill all of the important functions carried out by the native RPE. Studies are proposed that focus on aspects of hES-RPE cell biology that will impact their potential application in ocular therapy. The first aim targets the identification of molecular mechanisms regulating the differentiation of hES-RPE cells, focusing on growth factors, extracellular matrix, matrix receptors, and transcription factors that have been implicated in RPE development in animal studies. Currently little is known about the factors that cause an undifferentiated hES cell to turn into an RPE cell. Ultimately, these studies should lead to the identification of optimal culture conditions that drive hES cells down the RPE differentiation pathway. The second aim is a comprehensive a molecular and cellular characterization of hES-RPE to assess the full extent of similarity to native RPE. Key RPE functions, including transport of nutrients, synthesis of pigment, and interaction with photoreceptors will be assessed. hES-RPE will be compared to native RPE via analysis of proteins, RNAs, and DNAs. Finally, the third aim proposes functional testing of hES-RPE in animal models to evaluate their key functions in vivo. While the proposed studies are considered high risk, they have an equally high potential gain. The experiments will provide a provisional assessment of the suitability of hES-RPE for ocular therapeutic applications.
Age-related macular degeneration (AMD) is the leading cause of blindness in elderly patients in California. An estimated 30% of people over 75 years of age are diagnosed with AMD and the disease incidence is predicted to double over the next 25 years, which represents a significant public health challenge to the State. The disease leads to the deterioration of fine acuity vision in the middle of the visual field, and can eventually lead to total blindness. The pathogenesis of this disease is poorly understood and there are no effective treatments. Loss of vision is a result of photoreceptor death, which is thought to be a consequence of the death of the neighboring retinal pigment epithelial (RPE) cells. One strategy that holds promise for the treatment of AMD is the replacement of defective RPE cells via cellular transplantation, and recently, it was demonstrated that human embryonic stem cells can be coaxed to turn into RPE-like cells (hES-RPE). This proposal will assess the suitability of these cells for possible use in human therapy for AMD. The benefit to California will be the development of a potential therapy for a blinding disease that affects millions of its citizens.