Basic Research

RETINA & VITREOUS

Age-related macular degeneration (AMD) is the leading cause of visual loss in the United States with currently ~1.75 million persons severely affected. Our goal is to functionalize cell-based therapy as a treatment option for patients with geographic atrophy (GA), the advanced form of dry aged-related macular degeneration (AMD), for which there is currently no treatment. The aim of cell-based therapy for AMD is to replace cells vital to vision, the retinal pigment epithelium (RPE), that are diseased, dying, or missing due to aging and AMD changes.

A major obstacle to successful RPE transplantation in AMD patients is the failure of transplanted cells to survive and become functional in the AMD eye. RPE transplantation in AMD patients typically has produced limited visual recovery regardless of the type of cell transplanted, even in immune suppressed patients.  An important limitation to RPE transplant success is the age- and AMD-related modification of Bruch’s membrane, the surface on which transplanted RPE must survive. These changes to Bruch's membrane appear to have a significant effect on RPE graft survival. Evidence from aged and AMD donor eye-based organ culture assays performed in our laboratory predicts the poor survival that is observed in patients receiving RPE transplants, even when healthy RPE are transplanted (e.g., cultured fetal human RPE and RPE derived from human embryonic stem cells).

Utilizing the organ culture assay, the Ocular Cell Transplantation laboratory research team has discovered  a biological mixture that supports attachment and long-term survival of transplanted RPE, including RPE derived from human embryonic stem cells, in early and late AMD donor eyes. Current studies are aimed at identifying bioactive components of CM with the long-term goal of developing a synthesized mixture of bioactive molecules to be used as an adjunct to RPE replacement therapy, supporting graft survival and functionality in AMD eyes.

Synaptic Function and Regeneration of Neurons in the Eye

Ellen Townes-Anderson, PhD

Dr. Townes-Anderson is using an in vitro system to examine synaptic function and regeneration of the mature central nervous system. We isolate functional, fully differentiated neurons from the adult vertebrate eye and maintain them in defined culture conditions. Sensory neurons, short interneurons, and projection neurons are all able to regrow neurites and reform functional synapses in vitro. Projects are currently under way to determine the specificity of synapse reformation, the effects of calcium and other second messengers on this regeneration, the signal transduction pathways that control cytoskeletal reorganization and changes in gene expression, and the effects of aging on regenerative capabilities. Much of the work is done on photoreceptors, since degeneration of these sensory neurons is a major cause of blindness. The techniques used include cell culture, immunocytochemistry, a variety of light microscopic techniques (including confocal laser scanning microscopy), electron microscopy, video-time-lapse photography, image processing, in-situ hybridization, and Northern blots. Recently, Dr. Anderson's group began using a new micromanipulation techniqueÑoptical tweezersÑto form specific groups of interacting neurons in culture. In the long term, the goal of this work is not only to better understand the capabilities of central synapses, but also to use this information to suggest clinical solutions for central nervous system repair and transplantation.