Cells of the human trabecular meshwork (TM) are constantly exposed to fluid mechanical forces generated by the intraocular pressure/flow of aqueous humor. Exposure to these forces can modulate the expression of many genes involved in aqueous humor physiology and pathophysiology. Elevated intraocular pressure (IOP), present in most forms of glaucoma, is known to affect structure and function of the TM. After 6 h elevated IOP, we found eleven genes to be consistently up-regulated in the human TM: interleukin-6, preprotachykinin-1, secretogranin-II, cathepsin-L, stromelysin-1, thymosin-beta4, alpha-tubulin, alphaB-crystallin, glyceraldehyde-3-phosphate dehydrogenase, metallothionein and Cu/Zn superoxide dismutase. The gene encoding TIGR/MYOC was up-regulated after 7 days. Our general hypothesis is that regulation of IOP is governed in part by the coordinated expression of TM genes. Specifically, we hypothesize that early response to elevated IOP would induce genes involved in maintaining homeostatic mechanisms of outflow regulation whereas sustained elevation of IOP would induce genes whose adverse products would be associated with pathological mechanisms. Finally, we hypothesize that the products of genes induced at 6 h predict mechanisms regulating outflow resistance that might be similar to those regulating vascular permeability. To test these hypotheses we propose to identify human TM/Schlemm's canal (SC) genes that are differentially expressed after 1 h, 48 h and 7 days exposure to an elevated pressure insult. We also propose to examine mechanisms of cellular permeability in human outflow cells and organ cultures under conditions of elevated pressure and over/under expression of selected genes. Our strategy includes perfused human anterior segment cultures, exponential amplification libraries, high- density cDNA arrays and adenoviral technology. This approach provides adequate mechanical stimulus (pressure drop), genetic homogeneity (paired eyes), libraries with small amounts of tissue and efficient gene delivery system. Even if some of the selected genes or mechanisms would appear to be not of primary relevance on the regulation of IOP, the identification of human TM/SC genes in the arrays will provide important new information on the coordinated gene expression of the outflow system under mechanical stress.
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