Experimental Research On Telomerase Activity, Cell Senescence And Apoptosis In Lens Epithelial Cells

Objective: (l)To investigate whether lens epithelial cell possesses telomerase activity. (2)Telomerase activity diversification, cell senescence and apoptosis in cultured lens epithelial cells. (3)Different sensitivities to apoptotic induction between healthy and senescent lens epithelial cells.Methods: (l)Telomeric repeat amplification protocol enzyme-linked immunoassay (TRAP-ELISA) was used to detect telomerase activities in ovine, rabbit, healthy and cataractous human lens epithelial cells. (2)Rabbit lens epithelial cells were cultured, passed from each generation. Telomerase activity of each generation was detected by TRAP-ELISA. Cell senescence was confirmed by the detection of beta-galactosidase. Cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL). (3)10 umol/1 camptothecin was used to induce cell apoptosis in the first, forth and seventh passage cells to distinguish different sensitivities to apoptotic induction factor in healthy and senescent cells.Results: (1)Telomerase activities were detected in rabbit, ovine and healthy human primary-cultured lens epithelial cells. No telomerse activity was detected in human cataractous lens epithelial cells. (2)The activity decreased during each cell passage until under detectable level at passage 4. Telomerase activities from lens explants, primary to thethird passage are 0.459±0.046, 0.322 ± 0.026, 0.253±0.029, 0.187 ± 0.019, 0.107 ± 0.038. The number of senescent cells increased correlating with the loss of telomerase activity. Senescent cells from the first to the ninth passage are (0.98 ± 0.39)%, (4.93 ± 1.35)%, (11.08 ± 1.69)%, (24.98 ± 3.55)%, (33.89 ± 3.74)%, (41.17 ± 5.24)%, (51.75 ± 8.32)%, (73.00 ± 5.98)%, (77.00±14.18)%. No senescent cell was detected from lens explants and the primary cultures. Apoptotic cells were not detected during cell cultures. (3)The sensitivities to apoptotic induction by camptothecin in healthy and senescent cells were in statistical significance. The Apoptotic cells in the first, forth and seventh passage were (23.86±3.45)% , (32.08±4.75)% and (38.29 ± 4.01)% in respect.Conclusions: (l)Telomerase activities do exist in healthy lens epithelial cells. Cataractous human lens epithelial cells do not possess telomerase activity. (2)Telomerase activity decreases during lens epithelial cell culture. Senescent cells increase with cell passages. Senescent lens epithelial cells do not display spontaneous apoptosis. However, senescent cells are prone to die through apoptosis induced by camptothecin.