Diabetic preretinal membranes. An immunohistochemical study.

Fibrovascular membranes removed during vitreous surgery from patients with proliferative diabetic retinopathy were examined using indirect immunofluorescence. Antisera against collagen types I, III, IV, and V, attachment factors fibronectin and laminin, endothelial marker factor VIII, and the glial-marker glial-fibrillary acidic protein were used to examined the membranes. Seven of ten specimens contained cells staining positively for glial-fibrillary acidic protein, either singly or in large clusters within the membrane. Four of six membranes showed a well-developed vascular bed surrounded by a dense collagenous matrix. The matrix stained strongly with antiserum against both interstitial type I collagen and its associated attachment factor, fibronectin. In contrast, only localized staining was observed when antisera against both type IV collagen and its associated attachment factor, laminin, were used, and this was concentrated in regions of blood vessels and associated internal limiting membrane.