Retinal pigment epithelial (RPE) cells form a columnar, barrier epithelium at the back of the retina and do not normally divide in the mature animal. However, in some disease states, such as proliferative vitreoretinopathy (PVR), they gain access to, and proliferate in the vitreous. In PVR, cells in the vitreous elaborate membranous material containing extracellular matrix and cells. Contraction of these membranes results in traction forces that can detach the neural retina from the underlying RPE and cause blindness. RPE cells in the vitreous lose some of their normal properties and undergo a morphological transformation such that they have a more mesenchymal (fibroblast-like) appearance. These changes are also seen when RPE cells are cultured in the presence of vitreous in vitro. Little is known about biochemical changes involved, although a few gene products, including FGF-2, has been shown to be regulated by exposure to vitreous.
The aim of this application is to identify additional genes the expression of which is modulated by vitreous and to determine the role of the known and newly identified genes in the altered phenotype of the RPE cells upon vitreous-treatment. Using gene array technology, it is planned to examine a limited number of genes (approximately 1000) which are known to be regulated in neoplastic cells which also undergo epithelial-mesenchymal transformation as well as genes which are known to be involved in cell-cell interaction and those coding for growth factors, cytokines and their receptors. This makes it possible to examine the expression of many genes simultaneously. Since the gene sequence and protein sequence for each gene is known, and some information is available relating to each gene's function, the results should give insights into both what the changes are, and which ones might be important. This should facilitate the generation of hypotheses concerning the pathway of the epithelial-to-mesenchymal transformation, the possible nature of the vitreous components involved, and the implications of the results in retinopathies involving aberrant RPE cells, such as PVR. In future studies, beyond the scope of the current proposal, the information obtained will be used to investigate human epiretinal membranes removed during surgery, and to investigate changes in an animal model for PVR. The ultimate aim is the development of novel therapeutic approaches for PVR. This facilitated by the ability to deliver agents directly to the vitreous, which is separated from the blood stream by the blood-eye barrier.
