Collagen gel contraction by ARPE-19 cells is mediated by a FAK-Src dependent pathway

Proliferative vitreoretinopathy (PVR) may result in part from de-differentiation of retinal pigment epithelium (RPE) in an aberrant wound-healing strategy. An in vitro model of PVR, collagen gel contraction by RPE, likely requires integrin engagement and activation as an important initial step. The purpose of this study was to identify the important associated integrins and signal transduction pathway. The retinal pigment epithelial cell line ARPE-19 was used in these studies. Cell surface integrin expression was assessed using flow cytometry. An in vitro contraction assay was performed and the percent contraction quantified at specific time intervals using image capture (Gel Doc) and NIH Image software. Cells were pretreated with either small molecule inhibitors of signal transduction pathways or monoclonal antibodies with specificity for specific integrin isoforms. Transient transfections with a FAK siRNA were used to decrease FAK expression. ARPE-19 cells express alpha1, alpha2, and alpha3 integrin, isoforms involved in collagen ligation. Cell surface integrin blockade using anti-integrin alpha2 (P=0.02), alpha3 (P=0.01), or a combination of alpha1, alpha2, and alpha3 (P=0.001) antibodies significantly reduced collagen gel contraction. Inhibition of the FAK-Src complex, but not MEK or PI3K, significantly decreased contraction (P=0.0001). FAK siRNA transient transfection significantly reduced FAK protein expression by 71% (P=0.02) and concordantly decreased gel contraction (P=0.0001). RPE-mediated collagen gel contraction is a multi-step process. Integrin ligation and FAK-Src activation is necessary for collagen gel contraction produced by the ARPE-19 cell line. Validation of these observations in primary RPE cells may suggest new targets for therapeutic intervention in PVR.