Intracellular calcium response to hydraulic pressure in human trabeculum-derived cells

Purpose. To understand the mechanism for regulation of the intraocular pressure, we examined whether human trabeculum-derived cells could respond to the change in hydraulic pressure. Methods. Cells were cultured from human trabeculum tissue fragments excised during trabeculectomy in two patients with primary open-angle glaucoma, and exposed to hydraulic pressure change in a polystyrene tissue culture flask connected to a glass syringe. The pressure in the flask was elevated by automatic infusion of the piston of the syringe and monitored by a pressure gauge. The intracellular calcium concentration was measured in real time with a calcium-binding fluorescent dye, fluo-3. Results. The small number of cells (about 10%) showed transient elevations of the intracellular calcium concentration (transients) or a group of these transients (oscillations), in response to the elevation of hydraulic pressure around 20 mm Hg. Each transient lasted for 40 to 60 seconds. The base line levels of intracellular calcium in the responding cells were not different from those in the non-responding cells. The morphological difference between the responding and non-responding cells was not evident. Conclusions. Some cells in the human trabecular tissue could sense the change in intraocular pressure and might play a role in its regulation.