MeCP2-421-mediated RPE epithelial-mesenchymal transition and its relevance to the pathogenesis of proliferative vitreoretinopathy.

Proliferative vitreoretinopathy (PVR) is a blinding eye disease. Epithelial-mesenchymal transition (EMT) of RPE cells plays an important role in the pathogenesis of PVR. In the current study, we sought to investigate the role of the methyl-CpG-binding protein 2 (MeCP2), especially P-MeCP2-421 in the pathogenesis of PVR. The expressions of P-MeCP2-421, P-MeCP2-80, PPAR-γ and the double labelling of P-MeCP2-421 with α-SMA, cytokeratin, TGF-β and PPAR-γ in human PVR membranes were analysed by immunohistochemistry. The effect of knocking down MeCP2 using siRNA on the expressions of α-SMA, phospho-Smad2/3, collagen I, fibronectin and PPAR-γ; the expression of α-SMA stimulated by recombinant MeCP2 in ARPE-19; and the effect of TGF-β and 5-AZA treatment on PPAR-γ expression were analysed by Western blot. Chromatin immunoprecipitation was used to determine the binding of MeCP2 to TGF-β. Our results showed that P-MeCP2-421 was highly expressed in PVR membranes and was double labelled with α-SMA, cytokeratin and TGF-β, knocking down MeCP2 inhibited the activation of Smad2/3 and the expression of collagen I and fibronectin induced by TGF-β. TGF-β inhibited the expression of PPAR-γ, silence of MeCP2 by siRNA or using MeCP2 inhibitor (5-AZA) increased the expression of PPAR-γ. α-SMA was up-regulated by the treatment of recombinant MeCP2. Importantly, we found that MeCP2 bound to TGF-β as demonstrated by Chip assay. The results suggest that MeCP2 especially P-MeCP2-421 may play a significant role in the pathogenesis of PVR and targeting MeCP2 may be a potential therapeutic approach for the treatment of PVR.