Modulation of retinal pigment epithelial cell behavior by Agaricus bisporus lectin

PURPOSE. To determine whether Agaricus bisporus lectin (ABL) binds retinal pigment epithelial cells (RPEs), to conduct a preliminary viability study o f RPEs exposed to ABL, and to evaluate the effects of ABL on RPE proliferat ion and RPE-mediated matrix contraction in vitro. METHODS. Using cultured bovine RPEs, immunohistochemistry was used to study ABL binding. Morphologic and trypan blue exclusion techniques were used fo r toxicity studies. The effect of ABL on RPE proliferation was investigated by [methyl-H-3]-thymidine incorporation. The effect of ABL on RPE-mediated matrix contraction was evaluated with RPE-populated three-dimensional coll agen matrices. RESULTS. ADL bound to RPE cells. This binding was inhibited by asialomucin. No change in RPE morphology or trypan blue exclusion compared with control s was observed in RPEs incubated with 5 to 60 mu g/ml ABL for 3 days. Twent y-four-hour incubations of RPEs with ABL significantly inhibited RPE prolif eration in a close-dependent way, 40 mu g/ml ABL inhibited proliferation by 83% (SE 14, P < 0.05). ABL showed 3 dose-dependent significant inhibition of RPE-mediated collagen matrix contraction over 3 days, with 93% inhibitio n compared with controls by 40 mu g/ml lectin (P < 0.05). The inhibitory ef fect of ABL on proliferation and gel contraction Ras partly reversible afte r eliminating ADL from the culture medium. CONCLUSIONS. Bovine RPE cells bind ABL, and preliminary evaluations suggest that levels of ABL that are nontoxic to the cells potently inhibit RPE pro liferation and RPE-mediated matrix contraction. ABL deserves further invest igation as a potential inhibitor of RPE proliferation and cell-mediated mat rix contraction in anomalous reparative processes such as proliferative vit reoretinopathy and as a laboratory tool for RPE behavioral studies.