Aging of trabecular meshwork cells of the human eye in vitro.

A monolayer cell line established from the trabecular meshwork of a human eye exhibited a limited proliferation potential with about 18 population doublings (PD). There was a gradual increase of the average PD time with increasing PD level. Finally, there was complete growth cessation. These non-replicating cells were larger and more flattened (decrease of the saturation density); they became granulated and finally died off in the course of several months. This growth pattern resembled the senescence phenomenon, as originally described by Hayflick and Moorhead for cultured human fibroblasts. In comparison to proliferating phase-II cultures, senescent cultures revealed reduced glycosaminoglycan synthesis rates with a relative decrease of hyaluronic acid and increase of heparan sulfate. Exogenous (medium-supplied) hyaluronic acid or ascorbic acid stimulated hyaluronic acid synthesis of phase-II cultures.