The endothelium is critical for maintaining corneal transparency. With age, human corneal endothelial cells lose their ability to divide. Since there is no replacement of cells lost due to normal attrition the number of cells comprising the monolayer decreases over time. In older persons, the stress of disease, trauma, or intraocular surgery can further compromise this tissue, causing it to lose its ability to maintain an intact monolayer, producing edema and, sometimes, the need for corneal transplantation. Our long-term goal is to develop pharmacological treatment for age- and disease-related changes in the corneal endothelium. To do this, we must discover how corneal endothelial cells respond to a defect in the monolayer by breaking contact with their neighbors and migrating as individuals to repopulate the area, and/or by collectively enlarging and flattening, causing the continuous monolayer of cells to move or spread into the defect area. Using tissue culture models which mimic the behavior of adult human corneal endothelium, we have discovered that corneal endothelial migration and spreading are pharmacologically separable forms of movement. We will use these models to: 1) characterize the morphologic features which distinguish migrating from spreading cells, 2) determine whether extracellular matrix components might be endogenous signals for either migration or spreading, 3) identify the intracellular pathway which mediates the signal for cell migration or for spreading, 4) determine what modifications occur in gene expression and in protein synthesis, phosphorylation and subcellular organization to produce either migration or spreading, and 5) identify specific pharmacological agents which stimulate wound repair. Techniques that will be used in these studies include scanning electron microscopy, digitized morphometry, one and two-dimensional gel electrophoresis, metabolic labeling, immunocytochemical localization, Northern blot analysis, in vitro translation and in situ hybridization. Information obtained using these methods should provide a basis for designing drug treatments which will preserve human corneal endothelial function, stimulate and, perhaps, accelerate endothelial wound healing, and reduce the effects of stress on the aging endothelium. Our studies will also establish the corneal endothelium as a model for the study of wound repair in monolayer tissues in the eye and in other organs.
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