Responses of different cell lines from ocular tissues to elevated hydrostatic pressure

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Abstract
BACKGROUND/AIMS Mechanical forces are thought to induce cellular responses through activation of signalling pathways. Cells within the intraocular environment are exposed to constant changes in the levels of intraocular pressure. In this study, an attempt was made to determine the acute effects of elevated hydrostatic pressure on different intraocular cells grown in culture. METHODS Different cell lines derived from ocular tissues including non-pigmented and pigmented ciliary epithelium, trabecular meshwork, retina, and lamina cribrosa were incubated in a pressurised chamber at 50 mm Hg in a culture incubator at 37°C for up to 6 hours. Control cells were incubated at atmospheric pressure. The viability of the cells was examined using their intracellular esterase activity. The morphology and cytoskeleton of the cells were investigated using microscopy and phalloidin staining. Adenylyl cyclase activity was assessed by measuring the conversion of [3H]-cAMP from [3H]-ATP in response to elevated hydrostatic pressure for 1–6 hours. In addition, at the end of incubation period under elevated hydrostatic pressure the recovery of adenylyl cyclase activity to control levels was examined. RESULTS Cell viability did not change following exposure to elevated hydrostatic pressure for 6 hours. Cells subjected to elevated hydrostatic pressure demonstrated morphological differences characterised by a more rounded shape and a redistribution of actin stress fibres that was most prominent in lamina cribrosa astrocytes. A time dependent increase in basal adenylyl cyclase activity, and a decrease in maximum forskolin stimulated activity were observed in all cell lines following exposure to elevated hydrostatic pressure. CONCLUSION These observations demonstrate that cell lines from different ocular tissues are sensitive to changes in external pressure in vitro. They exhibit morphological and cytoskeletal changes as well as significant alterations of intracellular adenylyl cyclase activity following exposure to acute and sustained levels of elevated hydrostatic pressure of up to 6 hours' duration.