[Thrombospondin and its importance in proliferative retinal diseases]

Thrombospondin (TSP), a platelet-derived protein of the integrin-binding family with adhesive and mitogenic properties was localized in surgically obtained epiretinal traction membranes from patients with traumatic (7/8) and idiopathic (8/8) proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR) (6/8). Using double-label immunofluorescence techniques, we demonstrated co-localization of TSP with the endothelial cell marker, von Willebrand factor, in PDR; however, only a minority of labeled macrophages showed simultaneous staining for TSP. Therefore, macrophages are probably not a major source of TSP in PVR. We demonstrated co-distribution of blood coagulation factor XIII and two of its cross-linking substrates, fibronectin and TSP, in epiretinal membranes, as well as the detection of plasmin and presumably plasmin-induced TSP breakdown products in physiologic and pathologic vitreous. These results suggest that the coagulation system has a functional role in proliferative retinal disorders and imply that the application of inhibitors of the coagulation cascade like heparin may be a potential therapeutic approach.