The effect of latanoprost and brimonidine on rabbit subconjunctival fibroblasts

Purpose: Subconjunctival fibroblasts play a critical role in scarring and t reatment failure in fistulizing surgery for glaucoma The proliferation of s ubconjunctival fibroblasts appears to be modulated by topical glaucoma medi cations. This study was conducted to evaluate the effects of latanoprost an d brimonidine on subconjunctival fibroblast proliferation in rabbit eyes. Methods: Twelve pigmented Dutch-belted rabbits were divided into treatment groups of four: latanoprost 0.005%, brimonidine 0.2%, or balanced saline so lution (BSS) each were administered to one treatment group, both eyes of ea ch rabbit, twice a day, 6 days a week for 10 weeks. The eyes were then enuc leated along with the conjunctiva, fixed, processed, and evaluated by light microscopy and immunohistochemistry using anti-proliferating cell nuclear antigen (PCNA) and anti-muscle-specific actin antibody (HHF-35). Fibroblast cell counts were performed at magnification x40. Results: In all groups, few inflammatory cells were seen in the subconjunct ival space under light microscopy. PCNA staining revealed a statistically s ignificant increase in the mean number of labeled fibroblasts in the group receiving brimonidine compared with the control (BSS) group. The. group rec eiving latanoprost also had a significantly higher mean number of labeled f ibroblasts than the groups receiving brimonidine or BSS. Only a few fibrobl asts stained positively with the anti HHF antibody. Eyes treated with latan oprost, however, had significantly higher numbers of positively labeled cel ls than eyes treated with brinonidine or BSS. Conclusion: When applied to rabbit eyes, latanoprost and brimonidine appear to increase the number of positively labeled proliferating subconjunctival fibroblasts.