In vitro effects of mitomycin-C on human keratocytes

Purpose. To quantify the in vitro antiproliferative and cytotoxic effects of mitomycin-C on human keratocytes for its potential to modulate corneal stromal wound healing. Methods. Cultured human keratocytes were exposed to various concentrations of mitomycin-C for periods of 5 minutes and 1 hour. Keratocyte proliferation and viability were assessed by phase-contrast microscopy, ³H-thymidine uptake, and electronic cell counting. Results. Cyctotoxic changes and inhibition of keratocyte proliferation exhibited after exposure to mitomycin-C were both dose- and time-dependent. The lowest concentrations to significantly (>50%) inhibited keratocyte proliferation after 5-minute and 1-hour exposures were 0.05 mg/ml (p=0.005) and 0.005 mg/ml (p<0.001), respectively. With a concentration of 0.5mg/ml of mitomycin-C, 80.5% of the cells remained viable as compared to control after 5 minutes of incubation (p<.001); 45.7% of the cells remained viable after 1 hour of incubation (p<0.001). The median inhibitory dose (ID₅₀) and median lethal dose (LD₅₀) of mitomycin-C after 1 hour of exposure differed by a magnitude of 58 (0.0048 vs. 0.28 mg/ml). Conclusions. Mitomycin-C has antiproliferative effects at concentrations below those cytotoxic to human keratocytes. If used after photorefractive keratectomy, the drug should be administered at an antiproliferative rather than cytotoxic concentration.