CYTOKINES AND SERUM CAUSE ALPHA(2)BETA(1) INTEGRIN-MEDIATED CONTRACTION OF COLLAGEN GELS BY CULTURED RETINAL-PIGMENT EPITHELIAL-CELLS

Purpose. Integrins, heterodimeric cell surface glycoproteins, are invo lved in cell-substratum and cell-cell interactions. The role of these molecules in cytokine-mediated contraction of extracellular matrix by retinal pigment epithelial cells has been investigated in a model syst em that may mimic epiretinal membrane contraction during retinal detac hment in proliferative vitreoretinopathy. Methods. Retinal pigment epi thelial cells were cultured on three-dimensional collagen gels that th ey cause to contract. The involvement of new protein synthesis and C-k inase-mediated signal transduction were studied using specific inhibit ors. Cell surface integrins synthesized by pigment epithelial cells we re identified using immunofluorescence, and the same antibodies were u sed in gel contraction assays to identify the integrin species respons ible for force transduction. Results. Contraction of collagen type I g els was small without cytokines but was greatly enhanced in the presen ce of serum or IL1 plus TGF beta. It was dependent on new protein synt hesis. Contraction induced by the combination of cytokines was depende nt on active protein kinases, whereas that induced by serum was not be cause only the former was inhibited by staurosporine, a C-kinase inhib itor. Pigment epithelial cells were found to produce beta(1), alpha(2) , and alpha, integrins, but only alpha(2) and beta(1) appeared to part icipate in the contraction process because only antibodies against the se integrins inhibited contraction. Conclusions. Retinal pigment epith elial cells contract an extracellular matrix in vitro in a manner simi lar to epiretinal membrane contraction in vivo. This contraction is me diated via cell surface glycoproteins of the integrin family that bind directly to extracellular matrix molecules.