| By utilizing a model in vitro in which primary cultures of trabecular cells of the eye could be exposed to variable and controlled levels of hydrostatic pressure, we showed that cells exposed to 0 mmHg or to a sustained pressure of 15 mmHg for 24 hours maintained a spindle shape morphology, low level of pseudopodial movement, and normal organization of actin filaments and microtubules. At sustained hydrostatic pressures of 30, 40, or 50 mmHg, most cells developed a retracted profile, their cell membranes exhibited extensive and rapid pseudopodial movement, some individual cells became rounded and detached from the culture plate, and the organization of cytoskeleton was partially or completely disrupted. Morphometric analysis revealed that the intercellular area was enlarged, the cell area index decreased, and the cell thickness increased at elevated pressures. These alterations were more conspicuous at higher pressure. Additionally, exposure of trabecular cells to both physiologic and pathologic levels of hydrostatic pressure resulted in decreased cell viability.;By enzyme-linked immunosorbent assay (ELISA), it was shown that the culture medium conditioned by trabecular cells exposed to the physiologic level of pressure at 15 mmHg contained the same level of total TGF-beta 2 as, but less amount of intrinsically active TGF-beta 2, than that of cells at 0 mmHg. The amount of both total and intrinsically active TGF-beta 2 in the conditioned-medium was the same for cultures exposed to 15 mmHg or to 30 or 40 mmHg. Western blotting analysis of the extracts from trabecular cells demonstrated that the steady-state levels of cellular fibronectin were not altered by 24 hour elevation of hydrostatic pressure.;The results indicate that trabecular cells are sensitive to the ambient pressure level within their environment and imply that pressure within the eye may have a role in the regulation of the aqueous outflow through the bioactivity of the trabecular cells. The findings also explain, at least in part, the alterations that are characteristic of the trabecular meshwork in aging eyes and in eyes with glaucoma in which the intraocular pressure is elevated. |
