Aims: To determine whether hepatocyte growth factor (HGF) and connective tissue growth factor (CTGF) are expressed in human specimens of proliferative vitreoretinopathy (PVR) and to propose a model of PVR pathogenesis based upon the known activities of these growth factors. Methods Immunohistochemical methods (ABC Elite) were used to demonstrate the presence of HGF and CTGF in cryostat sections of five human PVR membranes.
Results: In each of the five PVR membranes, stromal cells were immunohistochemically positive for both HGF and CTGF. Based upon this information and the known actions of these growth factors, a model of PVR pathogenesis was developed. In this model, injury of the retina induces an inflammatory response that upregulates HGF expression inducing the formation of multilayered groups of migratory retinal pigment epithelial cells (RPE). These RPE, present in a provisional extracellular matrix, come in contact with vitreous containing TGF-beta. The TGF-beta is activated, upregulating expression of CTGF. Under the influence of TGF-beta and CTGF, RPE become myofibroblastic and fibrosis ensues. Retinal traction induces further detachment continuing the cycle of retinal injury.
Conclusions: HGF and CTGF are expressed in PVR membranes and may play important roles in the pathogenesis of PVR. The expression and function of these growth factors should be critically examined in human PVR specimens, in in vitro cultures of RPE, and in animal models of PVR.