Pseudophakic (PBK) and aphakic (ABK) bullous keratopathy is the most common indication for corneal transplantation. The investigators have showed that in PBK/ABK corneas, there is an increased expression and deposition of specific isoforms of an extracellular matrix protein, tenascin-C (TN-C), that is not expressed in normal corneas. TN-C can affect cell adhesion, migration and proliferation that are important in wound healing and tissue remodeling. They have also shown that PBK/ABK corneas have a corresponding increase in the expression of TN-C integrin receptors and certain growth factors/cytokines, which could induce TN-C expression. The following hypotheses are proposed: (1) that PBK/ABK corneas present an ongoing """"""""injury-response cycle"""""""" where the entire cornea stays in a continuous state of remodeling, (2) growth factors and/or cytokines play an important role in this cycle, and (3) the expression and deposition of TN-C affects the adhesive, migratory, proliferative and functional properties of corneal cells. Understanding these facets could lead to future therapeutic interventions. While TN-C, growth factors and cytokines are thought to play a significant role in PBK/ABK pathogenesis, other as yet unidentified abnormalities are probably also involved. Therefore, powerful new micro-sensitive techniques have been adapted for differential screening of genes from individual corneas. The hypothesis is that with these techniques, abnormalities in the expression of other genes important for PBK/ABK pathogenesis will be identified. There are three specific aims: (1) to determine the function of TN-C isoforms in PBK/ABK corneas by growing corneal cells on various isoforms of TN-C and determine rates of cell adhesion, migration, proliferation and function; (2) to determine the influence of growth factors and cytokines upon the expression of TN-C and TN-C binding integrins by: (a) identifying the abnormal growth factors/cytokines in PBK/ABK corneas, (b) determining the effects that these factors and dexamethasone have on the expression of TN-C and its binding integrins in corneal cells in vitro, and (c) determining if various isoforms of TN-C can affect the expression of TN-C binding integrins in vitro; and (3) to examine the differential gene expression in normal and PBK/ABK corneas and identify unique gene expression patterns by: (a) screening cellular mRNAs in normal vs. PBK/ABK corneas and cell layers using differential display, nucleic acid array and subtraction libraries; (b) determining if differentially-expressed genes are specific for PBK/ABK; and (c) determining whether altered gene expression in PBK/ABK is reflected at the protein level.
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