Hisashi Hosotani

Isolation and Chromosomal Localization of a Cornea-Specific Human Keratin 12 Gene and Detection of Four Mutations in Meesmann Corneal Epithelial Dystrophy

Keratin 12 (K12) is an intermediate-filament protein expressed specifically in corneal epithelium. Recently, we isolated K12 cDNA from a human corneal epithelial cDNA library and determined its full sequence. Herein, we present the exon-intron boundary structure and chromosomal localization of human K12. In addition, we report four K12 mutations in Meesmann corneal epithelial dystrophy (MCD), an autosomal dominant disorder characterized by intraepithelial microcysts and corneal epithelial fragility in which mutations in keratin 3 (K3) and K12 have recently been implicated. In the human K12 gene, we identified seven introns, defining eight individual exons that cover the coding sequence. Together the exons and introns span approximately 6 kb of genomic DNA. Using FISH, we found that the K12 gene mapped to 17q12, where a type I keratin cluster exists. In this study, four new K12 mutations (Arg135Gly, Arg135Ile, Tyr429Asp, and Leu140Arg) were identified in three unrelated MCD pedigrees and in one individual with MCD. All mutations were either in the highly conserved alpha-helix-initiation motif of rod domain 1A or in the alpha-helix-termination motif of rod domain 2B. These sites are essential for keratin filament assembly, suggesting that the mutations described above may be causative for MCD. Of particular interest, one of these mutations (Tyr429Asp), detected in both affected individuals in one of our pedigrees, is the first mutation to be identified within the alpha-helix-termination motif in type I keratin.

Reversal of Abnormal Corneal Epithelial Cell Morphologic Characteristics and Reduced Corneal Sensitivity in Diabetic Patients by Aldose Reductase Inhibitor, CT-112

PURPOSE A randomized clinical study was undertaken to determine whether a topically applied aldose reductase inhibitor, CT-112, was capable of reversing the abnormal morphologic characteristics of corneal epithelial cells, as well as the reduced corneal sensitivity, in diabetic patients. METHODS Thirty-nine diabetic patients were randomly divided into two groups: one group was treated with topical aldose reductase inhibitor (CT-112) in an ophthalmic preparation, and a control group was treated with the same preparation without the inhibitor. Specular microscopy was performed to analyze the morphologic characteristics of corneal epithelial cells before and after the treatment. Corneal sensitivity was measured by means of the Cochet-Bonnet esthesiometer. RESULTS The anterior surface area of superficial cells in the group treated with CT-112 was significantly decreased from a mean value of 881 to 728 microns2 (P < .0001), whereas the control group showed no significant changes. Corneal sensitivity remained decreased in the control group, whereas that in the group treated with CT-112 significantly improved, from 5.36 to 1.37 g/mm2 (P < .0001). CONCLUSIONS These results indicate that treatment with topical CT-112 is capable of reversing abnormal morphologic characteristics of corneal epithelial cells and reduced corneal sensitivity in diabetic patients.

Vitamin A eyedrops for superior limbic keratoconjunctivitis.

We treated 12 patients with superior limbic keratoconjunctivitis with topical vitamin A (retinol palmitate) eyedrops. After a follow-up period of at least three months, this therapy was found to be effective, to a varying extent, in ten patients (83%). Superior limbic keratoconjunctivitis lesions did not recur in these patients as long as topical application was continued.

Aldose reductase inhibitor (CT-112) eyedrops for diabetic corneal epitheliopathy.

We treated two diabetic patients with corneal epithelial disorder that resisted conventional medical therapy with topical CT-112 (5-[3-ethoxy-4-pentyloxyphenyl]-2,4-thiazolidinedione), a newly synthesized aldose reductase inhibitor. One patient had developed recurrent corneal erosion after vitrectomy and the other had spontaneously developed superficial punctate keratopathy. The corneal lesion in each patient responded to topical CT-112 in two to four weeks and was almost cleared within two months. A similar corneal lesion recurred in both patients soon after CT-112 was discontinued, but it disappeared again when the drug was resumed.

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...

Core vitrectomy preceding triple corneal procedure in patients at high risk for increased posterior chamber pressure.

We evaluated the effectiveness of performing a core vitrectomy to prevent intraoperative posterior chamber pressure evaluation in eyes at high risk for development of this complication, prior to penetrating keratoplasty, extracapsular cataract extraction and posterior chamber lens (IOL) implantation. Results in 10 cases with core vitrectomy were compared with 10 cases without (controls); in all eyes with vitrectomy, a posterior chamber IOL was easily implanted but four eyes of the control group developed vitreous complications. Our results indicate that core vitrectomy does facilitate IOL implantation during a triple corneal procedure in eyes at increased risk of elevated posterior chamber pressure.

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.