Purpose: The purpose of this study is to determine why a single intraoperative dose of mitomycin C (MMC) appears to promote the success of glaucoma filtration surgery. Methods: Human Tenon's capsule fibroblasts were exposed to MMC and 5-fluorouracil (5-FU) in vitro at the concentrations and durations of exposure used clinically. Cell proliferation was assessed by quantification of 3H-thymidine uptake. Cell viability was studied using a sulfarhodamine B cell protein stain and by trypan blue exclusion. Results: Neither MMC (0.4 mg/ml) nor 5-FU (40 mg/ml) were cytocidal. Both 1- and 5-minute exposures to MMC were antiproliferative. A 1-minute exposure to 0.4 mg/ml inhibited 3H-thymidine uptake by 77%. For the 5-minute exposure, 3H-thymidine uptake was inhibited by 50% at 0.06 mg/ml and by 90% at 0.4 mg/ml. For 5-FU, 3Hthymidine uptake was inhibited by 50% at 10 mg/ml and by 64% at 40 mg/ml. Conclusions: Mitomycin C probably does not improve the success of filtration surgery by killing fibroblasts. The ability of a brief exposure to MMC to improve filtration surgery may be due to an almost complete inhibition of proliferation. Alternatively, it may be due to sustained tissue binding, effects on other components of wound healing, such as cell migration and extracellular matrix production, or effects on the vasculature. A 1-minute exposure may be as effective as a 5-minute exposure.
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