Protective Effect of Hyaluronic Acid on the Corneal Endothelial Function Against Free-Radical Damage

PURPOSE: To investigate the protective effects of hyaluronic acid with glutathione and ascorbic acid on corneal endothelial function against free-radical damage. METHODS: bovine corneal endothelial(BCEN) cells were treated with a flux of chemically generated superoxide anion produced by the combination of 1 mM hypoxanthine and 0.06 U/ml xanthine oxidase(HX-XO) for 10 minutes, and rabbit corneas were mounted in the dual-chamber specular microscope and perfused with bicarbonate Ringer(BR) solution for one hour and their endothelial surface was exposed to HX-XO for five minutes, and then perfused with glutathione, hyaluronic acid, or ascorbic acid in BR solution for three hours. BCEN cells was observed using MTT assay and rabbit corneal thickness was measured every 15 minutes and corneal swelling rates were calculated by linear regression analysis. Also, corneal endothelial permeability was measured using carboxyfluorescein and fluorometer. RESULTS: MTT assay showed less cytotoxicity in the cells treated with glutathione, hyaluronic acid, or ascorbic acid compared to HX-XO alone. Glutathione, hyaluronic acid, or ascorbic acid reduced the rabbit corneal swelling caused by HX-XO. Corneal endothelial permeability(Pac) increased in corneas perfused with HX-XO(7.88 x 10 cm/min) while those with BR had Pac of 4.54 x 10 cm/min. Following treatment with glutathione, hyaluronic acid, or ascorbic acid, Pac decreased to 4.96, 6.81, and 5.25 respectively(p<0.05). CONCLUSIONS: In conclusion, these data suggest that hyaluronic acid scavenges HX-XO-generated oxyradicals as well as glutathione and less likely ascorbic acid.

Immunohistochemical Stain and Electron Microscopic Study on the Pericytes of Fibrovascular Diabetic Preretinal Membrane

Seven fibrovascular diabetic preretinal membranes were examined with lightmicroscophic immunohistochemical stain and electron-microscopy to evaluate the possibility of pericytes to be involved in membrane contraction. Pericytes were positively stained with anti-actin antibody together with some stromal cells thought to be myofibroblasts presumedly. On transmission electron microscopic study, pericytes were highly active with numerous cytoplasmic processes and contained abundant microfilaments considered as actin in their cytoplasm. Pericyte/endothelial cell ratio of vascular channels were increased in some actively proliferative portion of the membranes. Myofibroblasts that contain abundant cytoplasmic microfilaments were also demonstrated in the extravascular stroma of the membranes and were very similar to the pericytes morphologically. Although the evidence that the pericytes are related to the origin of the myofibroblasts could not be demonstrated, this study suggested that the pericytes may play important roles in development and contraction mechanism of fibrovascular diabetic preretinal membranes.

Comparison of Inhibitory Effects of 5-Fluorouracil and Mitomycin C on Proliferation of Fibroblagts and Retinal Pigment Epithelial Cells

We evaluated the antiproliferative properties of Fluorouracil(5-FU) and Mitomycin C(MMC) in a tissue culture model of fibroblast and retinal pigment epithelial cells. Both drugs caused the dose dependent inhibition on proliferation of the cultured cells. The concentrations of 5 FU and MMC required for 50% inhibition of cellular growth(ID50) were 0.45mg/L and 2.3 X 10(-3)mg/L for rabbit subconjuntival fibroblasts, 0.21mg/L and 3.5 X 10(-3)mg/L for rabbit dermal fibroblast, 0.58mg/L and 7.4 X 10(-3)mg/L for rabbit retinal pigment epithelial cells, and 0.38mg/L and 3.4 X 10(-3)mg/L for human retinal pigment epithelial cells, respectively. In general, ID50 of both drugs were higher in retinal pigment epithelial cells than in fibroblasts but MMC showed same inhibitory effect on proliferation of all cell types at lower doses in comparision to 5-FU. These results suggest that 5-FU and MMC may be of significant values in the treatment of intraocular proliferative disorders and MMC, however, seems to be more useful than 5-FU if it's safty would be proved.

The Effect of Corticosteoid Treatment on Myopic Regression after Photorefractive Keratectomy

With the aim of reversing myopic regression after PRK, the effect of highdose topical corticosteroid in modulating changes in refraction and corneal transparency were assessed prospectively. Seventy-two eyes of 62 patients (mean preoperative SE -6.14D; -2.30 D to -11.50D), demonstrating myopic regression ranging between -0.75D to -5.33D (mean: -1.69D), were treated with 0.1% dexamethasone eye solution five times a day for averaging 2.8 weeks. The age of patient, amount of attempted correction and K-reading did not influenced statistically significantly on myopic regression. Uncorrected visual acuity, mean refraction before reintroducing corticosteroids (mean: 0.58, -1.69D) improved after corticosteroid treatment (mean: 0.85, -0.42D)(p<0.01). Corneal haze changed statistically significant from 0.80 +/- 0.61 to 0.53 +/- 0.40 after steroid treatment(p<0.01). Topical corticosteroid therapy can modulate refractive changes after PRK, appearing to improve myopic regression. However, a long term follow up will be necessary to determine the final refractive outcome of these eyes.