There is currently no effective treatment to restore or improve vision for patients suffering from incurable blinding diseases such as dry age-related macular degeneration and retinitis pigmentosa, which need both new photoreceptors and retinal pigment epithelium. However, a unique method to transplant fetal retinal progenitor sheets together with its supporting retinal pigment epithelium (RPE) has been shown to improve vision in animal models of retinal degeneration and in patients. Differentiation of human embryonic stem cells (hESCs) into sheets of retinal progenitor tissue that contain photoreceptor progenitors and RPE cells would create an unlimited supply of donor tissue. Our lab has generated retinal progenitor tissue from hESCs in 3-D constructs (“layers”) and implanted sheets of ESC-derived neuronal progenitors into a rat model of retinal degeneration where they survived and continued to develop in the subretinal space. The hypothesis of the proposed project then is that hESCs can be consistently differentiated into sheets of retinal tissue, which can restore visual responses after transplantation to a new immunodeficient rat model of retinal degeneration that does not reject human cells. We will also determine whether this tissue is safe to use in patients by testing it in an immunodeficient rat strain. This project will ultimately help to restore vision in patients suffering from retinal diseases.
Retinal diseases reduce the quality of life of patients who suffer from vision loss and at significant cost to the health care system. Age-related macular degeneration (AMD) destroys the central vision and is the most common cause of blindness among people over 65. Over a 15-year period, late AMD will affect 3.1 % of the general population which means 9.6 millions in the U.S. and about 1.15 millions in California, with these numbers growing as the population ages. Another incurable disease, retinitis pigmentosa (RP) which is inherited (1:4000) and occurs in younger people, affects the light-sensing photoreceptors first, but also the supporting RPE layer beneath the retina following photoreceptor degeneration. Thus, both AMD and RP patients will need both new RPE and photoreceptors. The proposed replacement therapy is the only one that targets more mature disease stages of both AMD and RP, for which no other therapy exists. An effective treatment will keep afflicted individuals productive, enhance State tax revenues and defray the healthcare cost burden to taxpayers. It will also lead to robust industry developments in the fields of clinical transplantation, drug screening, and predictive toxicology, effectively leading to job creation and tax benefits to the State as a result of consumption of research and clinical goods and services.