Human diabetic corneas preserve wound healing, basement membrane, integrin and MMP-10 differences from normal corneas in organ culture

Abstract

The authors have previously documented decreased epithelial basement membrane (BM) components and α 3β 1 epithelial integrin, and increased expression of matrix metalloproteinase (MMP)-10 in corneas of patients with diabetic retinopathy (DR) compared to normal corneas. The purpose of this study was to examine if organ-cultured DR corneas exhibited the same alterations in wound healing and diabetic marker distribution as the autopsy DR corneas. Twenty normal and 17 DR corneas were organ-cultured in serum-free medium over agar–collagen gel at the air–liquid interface for up to 45 days. Circular 5 mm central epithelial wounds were made with n-heptanol, the procedure that will preserve fragile diabetic corneal BM. Wound healing was monitored microscopically every 12 hr. Distribution of diabetic corneal epithelial markers including laminin-10 α5 chain, nidogen-1/entactin, integrin α 3β 1, and MMP-10, was examined by immunofluorescence. Normal corneas healed the central epithelial defect within 3 days (mean=2·3 days), whereas DR corneas on average healed about two times slower (mean=4·5 days). In wounded and completely healed organ-cultured corneas, the patterns of studied markers were the same as in the unwounded organ-cultured corneas. This concerned both normal and DR corneas. As in vivo, normal organ-cultured corneas had continuous staining for laminin-10 and nidogen-1/entactin in the epithelial BM, strong and homogeneous staining for both chains of α 3β 1 integrin in epithelial cells, and little if any staining for MMP-10. Organ-cultured DR corneas also had marker patterns specific for in vivo DR corneas: interrupted to no staining for laminin-10 and nidogen-1/entactin in the epithelial BM, areas of weak or disorganized α 3β 1 integrin in epithelial cells, and significant MMP-10 staining in the epithelium and keratocytes. Fibrotic extracellular matrix and myofibroblast markers were largely absent. Thus, epithelial wound healing was much slower in organ-cultured DR corneas than in normal corneas, in complete accordance with clinical data in diabetic patients. DR corneas in organ culture preserved the same marker abnormalities as in vivo. The marker distribution was unchanged in wounded and healed organ-cultured corneas, compared to unwounded corneas. The established corneal organ culture provides an adequate system for elucidating mechanisms of epithelial alterations in human DR corneas.