In vitro effects of mitomycin-C on human keratocytes

BACKGROUND: The purpose of the present study is to quantify the in vitro antiproliferative and cytotoxic effects of mitomycin-C on human keratocytes for their 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: Cytotoxic changes and inhibition of keratocyte proliferation exhibited after exposure to mitomycin-C were both dose- and time-dependent. The lowest concentrations to significantly (>50%) inhibit keratocyte proliferation after 5-minute exposures were 0.05 mg/ml (P<.005) and after 1-hour exposures were 0.005 mg/ml (P<.001). At 5 minutes, ID₅₀ was 0.038 mg/ml and LD₅₀ was much higher than the greatest concentration tested (0.5 mg/ml). Mitomycin-C's median inhibitory dose (ID₅₀) and median lethal dose (LD₅₀) after 1 hour of exposure differed by a magnitude of 50 (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 antiproliferative rather than cytotoxic concentrations.