Edible mushroom (Agaricus bisporus) lectin modulates human retinal pigment epithelial cell behaviour in vitro.

The retinal pigment epithelium (RPE) plays a major role in the development of proliferative vitreoretinopathy (PVR). In particular, RPE cells are implicated in generating the contraction forces seen. The present study was undertaken to investigate whether human RPE binds a lectin from the common edible mushroom, Agaricus bisporus, and to evaluate the effect of any binding on RPE-mediated matrix contraction in an in vitro model of PVR. Fluorescein isothiocyanate (FITC)-labelled Agaricus bisporus lectin (ABL) was used to study binding of lectin to normal retina, PVR scar tissue specimens and cultured human RPE. The effect of a 3-day exposure of ABL on human RPE-mediated contraction was evaluated using 2- and 3D RPE-populated collagen matrices. Effect of ABL on cell adhesion was measured using a collagen type I adhesion assay and determining the relative cellular attachment using absorbance readings. The normal RPE monolayer did not stain with FITC-ABL while PVR scar tissue stained intensely. Staining of in vitro RPE was characteristic but time-dependent. ABL caused a dose-dependent inhibition of RPE-mediated contraction of both 2D (one-way ANOVA, F = 7.94, p < 0.008) and 3D collagen matrices (one-way ANOVA, F = 164.955, p < 0.001). Pre-incubation of ABL with RPE in the 2D model caused a dramatic arrest of contraction (one-way ANOVA, F = 20.1, p < 0.001) that was due to a dose-dependent inhibition of adhesion (one-way ANOVA, F = 15.603, p < 0.001). Recovery of contraction was partially reversible on removal of ABL and was dependent on initial concentration of the lectin. ABL inhibits contraction and adhesion of human RPE cells in vitro without apparent cytotoxicity. It therefore deserves consideration as a potential therapeutic agent in the prevention and treatment of PVR and other non-ocular anomalous wound-healing processes.