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The frequency and extent of immunostaining for actin, fibronectin (FN), and glial fibrillary acidic protein (GFAP) were determined in 37 preretinal membranes (PRMs) obtained at vitrectomy from 35 patients with proliferative diabetic retinopathy (PDR) (n = 16), proliferative vitreoretinopathy (PVR) (n = 18), or idiopathic macular pucker (MP) (n = 3). All three proteins were detected in the vast majority of specimens (actin, 86%; FN, 95%; GFAP, 96%), although the extent of staining varied for each. Actin-FN co-localization was observed in all diagnostic groups on comparison of adjacent sections and in double-labeled sections. The extent of actin staining did not correlate with clinical grading of PRM contraction. In PDR membranes, FN staining was low overall, but proportional to the vascular content of the PRM. Fibronectin staining of PVR membranes was greater, and extensive even in avascular specimens. In MP membranes, most cells were GFAP-positive, whereas in PDR and PVR specimens, GFAP staining was variable. The lack of correlation of clinical contractility and membrane composition, as studied in this article by immunostaining, indicates that other factors must play significant roles in determining membrane behavior.

Previous studies of fibronectin (FN) distribution in eye tissue have relied on immunofluorescence (IF) techniques on frozen sections, and have not included the rat. Using rat eyes, a technique was developed for immunoperoxidase (IP) staining of formalin fixed paraffin embedded material, and the results were compared to those obtained by IF. IP was technically more difficult, and required pepsinization of tissue after formalin fixation to obtain consistent results. The optimum pepsin time varied for different structures in the eye. IP offers better tissue preservation and stain resolution. Results with IF were consistent with those observed with the newly applied IP. The distribution of FN in rat eyes was similar though not identical to that reported in other species. Prominent stain was observed in the conjunctiva, basement membrane of the corneal epithelium, corneal stroma, anterior aspect of Descemet's membrane, trabecular meshwork, perivascular stroma of the ciliary body, choroid and retinal blood vessels. Lens structures, vitreous, and internal limiting membrane of the retina were negative.