Paclitaxel inhibits growth, migration and collagen production of human Tenon's fibroblasts—potential use in drug-eluting glaucoma drainage devices

OBJECTIVE/AIM: One of the factors limiting the long-term success of glaucoma drainage devices and traditional filtering surgery is the tendency of bleb encapsulation. Glaucoma shunts present an opportunity of introducing drug-eluting mechanisms for a lasting exposure of the bleb to anti-proliferative substances. The aim of this in vitro study was to investigate the effects of short- and long-term exposure of primary cultures of human Tenon's fibroblasts to different concentrations of paclitaxel on cell proliferation, migration, collagen production and cytotoxicity, in order to evaluate the suitability of the drug for the use in such a device. MATERIALS/METHODS: Seven individual primary cultures of human Tenon's fibroblasts were observed over the course of 1 week after administering paclitaxel concentrations varying from 10(−9) mol/l to 10(−6) mol/l for either 1 hour or continuously. Relative cell count and migration across a cell-free area introduced by scratching through a confluent cell layer were determined every 24 hours, using photomicrographs of the cells for each concentration and exposure time. Soluble collagen concentration in the cell culture medium was determined using a Sircol collagen assay 72 hours after paclitaxel exposure. Cytotoxicity of the compound was assessed by flow cytometry using dual staining with annexin V-FITC and propidium iodide. RESULTS: Paclitaxel dose-dependently inhibited both proliferation and migration of the cells. Cell count was reduced at all concentrations and both exposure times (p = 0.001); similarly, all but two concentrations of paclitaxel caused a significant reduction of cell migration (p < 0.001). This may be explained in part by the dose- and time-dependent induction of apoptosis in up to 23.7% of the cells (maximal effect at 10(−6) mol/l, 7 days after exposure). Collagen production was significantly reduced at all concentrations and at both exposure times. However, no statistically significant difference was observed between any of the concentrations, indicating that this inhibition may be an indirect effect. CONCLUSION: Paclitaxel may be a useful addition to the repertoire of anti-proliferative substances currently in use in glaucoma filtering surgery and shunt implantation. Further studies of the compound and its effects on Tenon's fibroblasts as well as other ocular tissues are warranted.