Epithelial migration and/or adhesion to the basement membrane are compromised in recurrent epithelial erosions and persistent epithelial defects. To better understand how epithelial cells migrate in response to injury in the cornea, it is important to understand the adhesive interactions that exist between the epithelium and the underlying basement membrane. Previously, it was hypothesized that integrins, a family of cell surface receptors which are known to be involved in mediating cell:substrate interactions and signal transduction in many cell types, were involved in cell migration in the corneal epithelium. It was shown that distinct integrins, including a6B4 and a9, are expressed at elevated levels during healing in response to debridement and that their expression appears correlated with cell proliferation. Also shown previously was that a6B4 integrin was a component of the hemidesmosomes, those stable attachment sites which allow the epithelium to remain adherent when not migrating.
Aim 1 of this proposal is to determine whether the accumulation a6B4 protein in corneal epithelial cells in vivo in response to injury is regulated by changes in mRNA expression, protein turnover rates, or by phosphorylation.
Aim 2 is to determine whether increased expression of a6B4 during migration in vivo alters the properties of the cells as compared to cells migrating in vitro by measuring cell adhesion, cell:cytoskeletal associations, cell proliferation, and cell signaling in both models.
Aim 3 is to determine the role environmental factors, including growth factors (EGF, HGF, IGF, TGFB) and neurotrophic factors, play in the quality of the wound response using rat corneal debridement wounds B in vitro and in organ culture.
Aim 4 is to determine whether initiation of cell proliferation using the excimer laser to ablate superficial cell layers only induces integrin expression in the corneal epithelium.
Aim 5 is hemidesmomes after wounding using morphometry and tenascin knockout mice. The proposed studies of integrin expression in the corneal epithelium will provide insight into the basic cell biology of migration and the role of integrin:matrix interactions in the healing of corneal wounds.
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