Inhibition by female sex hormones of collagen gel contraction mediated by retinal pigment epithelial cells

PURPOSE. Collagen contraction mediated by retinal pigment epithelial (RPE) cells contributes to the pathogenesis of proliferative vitreoretinopathy (PVR). We examined the effects of sex hormones on this process. METHODS. Mouse RPE cells were cultured in a type I collagen gel and exposed to 17b-estradiol, progesterone, or dehydro-epiandrosterone. Collagen contraction induced by transforming growth factor-b2 (TGF-b2) was determined by measurement of gel diameter. Expression of asmooth muscle actin (a-SMA), as well as phosphorylation of Smad2 and myosin light chain (MLC), was examined by immunoblot analysis. Matrix metalloproteinase (MMP) release was evaluated by gelatin zymography. Fibronectin and interleukin-6 secretion was measured with immunoassays. RESULTS. The female sex hormones 17b-estradiol and progesterone inhibited TGF-b2-induced collagen contraction mediated by RPE cells, whereas the male sex hormone dehydroepiandrosterone had no such effect. The TGF-b2-induced release of MMP-2 and MMP-9 from RPE cells was also inhibited by 17b-estradiol and progesterone, and the MMP inhibitor GM6001 attenuated TGF-b2-induced collagen contraction. Expression of the mesenchymal markers a-SMA and fibronectin, interleukin-6 release, and Smad2 and MLC phosphorylation induced by TGF-b2 were all inhibited by 17b-estradiol and progesterone. Immunohistochemical analysis also detected nuclear immunoreactivity for estrogen and progesterone receptors in proliferative fibrocellular membranes of PVR patients. CONCLUSIONS. Female sex hormones inhibited TGF-b2-induced collagen contraction mediated by RPE cells. This action appeared to be mediated through inhibition both of MMP, a-SMA, and fibronectin expression as well as of Smad2 and MLC phosphorylation. Female sex hormones might thus prove effective for the treatment of PVR