uPA, tPA and PAI-1 mRNA expression in periretinal membranes

Purpose. Formation of periretinal membranes occurs in proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR) and includes cell migration, proliferation, extracellular matrix formation and tissue contraction, processes in which plasminogen activation (PA) system is involved. Methods. Twenty PVR, PDR or pucker membranes were examined to identify the cells with cell specific markers and to detect the expression of urokinase (uPA), tissue-type plasminogen activator (tPA) or plasminogen activator inhibitor-1 (PAI-1) by in situ hybridization and by immunohistochemistry. Results. In PVR, uPA, tPA and PAI-1 were expressed by retinal pigment epithelial (RPE) cells, macrophages or retinal glial cells. In PDR, PA components were also expressed by endothelial cells. Semi quantitative analysis in in situ hybridization and immunohistochemistry results demonstrated no notable differences in uPA, tPA or PAI-1 expression between PDR and PVR membranes. Conclusions. We conclude that local proteolytic activation is involved in extracellular matrix production both in diabetic and non-diabetic membranes.