Collagen pleomorphism in Descemet's membrane of streptozotocin-induced diabetic rats: An electron microscopy study

Background. Diabetes mellitus causes ultrastructural changes in various basement membranes. These changes include increase in collagen biosynthesis rate and production of altered collagen. Purpose. To evaluate the ultrastructural changes in the corneas of streptozotocin-induced diabetic rats, focusing on Descemet's membrane. Methods. Sprague-Dawley rats were sacrificed at different intervals after induction of diabetes mellitus by streptozotocin. Ten animals were sacrificed 1, 2, 3, 4, 6, 8, and 12 months after the injection of streptozotocin. Five untreated rats of the same age were used as normal controls and were sacrificed at the same intervals. Ultrathin sections were obtained from the corneas and were examined by transmission electron microscopy. Results. Unusual 120-nm-spaced collagen fibril bundles were found in Descemet's membrane of the diabetic rats as early as the second month following the induction of diabetes. Their concentration and size increased gradually over the follow-up period of 12 months. Conclusions: Changes in the morphologic features of the collagen within Descemet's membrane may occur in diabetic-induced rats. The appearance of wide-spaced collagen fibrils in Descemet's membrane may represent alteration in collagen biosynthesis by the endothelial cells in diabetes or altered assembly of collagen due to increased glycosylation of normal formed collagen.