[Vitronectin: mediator of cell adhesion in proliferative vitreoretinopathy?]

Vitronectin, also known as protein S, the "serum spreading factor", or epibolin, was detected as an essential mediator of adhesion and spreading in many cells in vitro. The relatively low molecular weight of 65 kDa and a high plasma level of 200 mg/l implicate vitronectin as a possibly important factor in the pathogenesis of proliferative vitreoretinopathy (PVR) which is characterized by a breakdown of blood-ocular barriers. In a study of 15 periretinal membranes, using double label immunofluorescence techniques, we found vitronectin to be a significant component of the specimens' extracellular matrix in 13 cases. Vitronectin is co-localized with fibronectin, a much larger glycoprotein suggested as being involved in the pathogenesis of PVR. Among the biological properties of fibronectin are a role in cellular migration, adhesion, and proliferation. Both proteins share a unique cell recognition amino acid sequence, which mediates the receptor-dependent interaction between the extracellular matrix macromolecules and proliferating cells. Plasma is suggested as the major source of vitronectin in PVR because vitronectin could be detected in vitreous aspirates from patients with PVR, using electrophoresis and immunoblotting, but not in physiological human vitreous.