Takashi Awata

Dynamics of Fibronectin in Corneal Wound Healing: Immunohistochemical Study of Experimental Bullous Keratopathy in Rabbits

ABSTRACT The source of fibronectin in corneal wound healing was investigated in rabbits by inducing experimental bullous keratopathy using benzalkonium chloride. The location of fibronectin was detected by indirect immunofluorescent microscopy. One day after irrigation with benzalkonium chloride, no endothelial cells were found and epithelial damage was observed. Specific fluorescence for fibronectin was observed at the limbal area, which suggests the vascular origin of fibronectin, and at the stromal side of Descemets membrane. On day 3, endothelial healing became active. Fibronectin from limbal circulation was much more prominent than at day 1, and it diffused into the central portion of the cornea. Both the endothelial and stromal side of Descemets membrane stained for fibronectin. On day 7, fibronectin from limbal circulation decreased, as did fibronectin in the stroma. Retrocorneal membrane was observed and stained strongly for fibronectin. Our study demonstrates that fibronectin was released from limbal blood vessels and diffused into the stroma, and that endothelial cells may synthesize fibronectin during the healing process.

The effects of aldose reductase inhibitor on the corneal endothelial morphology in diabetic rats

Diabetic rats were produced by intravenous injection of streptozotocin. Of these, eleven rats were treated with topical instillation of 0.5% aldose reductase inhibitor (ARI), while ten received vehicle alone. The corneal endothelium of these diabetic rats was examined by specular microscopy and compared to age-matched nondiabetic rats (ten rats). Computerized morphometric analysis of individual cells demonstrated that the endothelium of the untreated diabetic rats had marked polymegathism (increased coefficient of variation in cell area) and pleomorphism (decreased percentage of hexagonal cells), as previously observed in diabetic patients. Similar endothelial changes were also noted in the ARI-treated diabetic rats, but to a significantly lesser extent. These results suggest that topically applied ARI can be effective in reducing morphologic changes of the diabetic endothelium, and that activation of the sorbitol pathway may be implicated in the etiology of such endothelial changes.

Effects of topical aldose reductase inhibitor CT-112 on corneal sensitivity of diabetic rats

Purpose. To investigate whether the loss in corneal sensation observed in human diabetics could be duplicated in diabetic rats and if this abnormality could be prevented by topical instillation of an aldose reductase inhibitor (ARI), CT-112.Methods. Rats were made diabetic by injection of streptozotocin. Some of these rats were treated with eye drops of CT-112 while others were treated with the same vehicle solution without ARI. Normal rats served as controls. Corneal sensitivity was measured by means of a Cochet-Bonnet aesthesiometer, using the blink reflex as an objective sign. Corneal changes in ultrastructure in diabetic rats were also observed.Results. The corneal sensitivity of diabetic rats was significantly decreased and this change was prevented by ARI treatment. Ultra-structurally, degenerations of axons and mitochondria of the corneal nerve were seen in the diabetic rats and the ARI treatment prevented these morphological changes.Conclusions. It is clear that corneal hypesthesia occurs in diabe...

.The effect of long-term topical administration of commercial beta-blockers on the rat corneal endothelium

To determine the effect of long-term topical application of commercial beta-blockers on the corneal endothelium, normal rats were randomly assigned to receive a drop of 0.5% timolol, 1% befunolol, or 2% carteolol four times daily for 8 months. Specular microscopy showed marked pleomorphism in the endothelium after three months of treatment with 1% befunolol. In contrast, the eyes treated with either 0.5% timolol or 2% carteolol demonstrated no significant change in endothelial morphology. Scanning and transmission electron microscopy at eight months after treatment revealed marked degeneration of the endothelium of the eyes treated with 1% befunolol. Similar endothelial changes were also noted in the 0.5% timolol-treated group, but to a significantly lesser extent. The eyes treated with 2% carteolol, however, showed only mild alteration of the endothelial ultrastructure. These results indicate that the corneal endothelium can be affected by long-term topical administration of commercial beta-blockers.

Effects of Topical Aldose Reductase Inhibitor (CT-112) on Corneal Sensitivity of Diabetic Rats

PURPOSE To investigate whether the loss in corneal sensation observed in human diabetics could be duplicated in diabetic rats and if this abnormality could be prevented by topical instillation of an aldose reductase inhibitor (ARI), CT-112. METHODS Rats were made diabetic by injection of streptozotocin. Some of these rats were treated with eye drops of CT-112 while others were treated with the same vehicle solution without ARI. Normal rats served as controls. Corneal sensitivity was measured by means of a Cochet-Bonnet aesthesiometer, using the blink reflex as an objective sign. Corneal changes in ultrastructure in diabetic rats were also observed. RESULTS The corneal sensitivity of diabetic rats was significantly decreased and this change was prevented by ARI treatment. Ultrastructurally, degenerations of axons and mitochondria of the corneal nerve were seen in the diabetic rats and the ARI treatment prevented these morphological changes. CONCLUSIONS It is clear that corneal hypesthesia occurs in diabetic rats as it does in human diabetics, and treatment with an ARI prevents this change. Along with the functional abnormality, the ultrastructural changes of corneal nerve also occur in diabetic rats, and they are prevented by ARI. These results strongly suggest that aldose reductase is involved in corneal hypesthesia and ultrastructural changes of corneal nerve in diabetic rats. These defects are ameliorated by aldose reductase inhibitor.