Open clinical study of eye-drops containing tetrapeptides derived from substance P and insulin-like growth factor-1 for treatment of persistent corneal epithelial defects associated with neurotrophic keratopathy.

BACKGROUND/AIMS: Loss of corneal sensation results in the development of persistent corneal epithelial defects. The combination of a substance P-derived peptide (FGLM-amide) and an insulin-like growth factor-1 (IGF-1)-derived peptide (SSSR) stimulates rabbit corneal epithelial migration in vitro and rabbit corneal epithelial wound closure in vivo. The clinical efficacy of eye-drops containing FGLM-amide and SSSR for the treatment of persistent corneal epithelial defects in individuals with neurotrophic keratopathy was examined in a prospective open study. METHODS: Twenty-five consecutive patients (26 eyes) with persistent corneal epithelial defects associated with neurotrophic keratopathy were treated by administration of eye-drops containing FGLM-amide and SSSR. The course of epithelial healing was monitored by slit-lamp examination. RESULTS: Epithelial defects resurfaced completely in 19 of the 26 eyes (73%) within 4 weeks after treatment initiation. Complete resurfacing of epithelial defects was apparent in 18 of 22 (82%) or in one of four (25%) eyes without or with limbal stem cell deficiency, respectively. No adverse effects of treatment were observed in any subject. CONCLUSION: Eye-drops containing FGLM-amide and SSSR induced the rapid resurfacing of persistent epithelial defects in stem cell-positive individuals with neurotrophic keratopathy.

Abnormal light scattering detected by confocal biomicroscopy at the corneal epithelial basement membrane of subjects with type II diabetes.

AIMS/HYPOTHESIS: Abnormalities of the basement membrane are thought to contribute to the complications of diabetes. The suitability of the cornea for detecting such abnormalities was assessed by determining its light-scattering index, a quantitative measure of tissue reflectivity in the basement membrane zone, with a confocal biomicroscope. METHODS: The light-scattering index was measured in 65 subjects with Type II (non-insulin-dependent) diabetes mellitus and 18 control subjects and was evaluated for its possible relation to the stage of diabetic retinopathy. Diabetic retinopathy was staged by ophthalmoscopic examination as non-diabetic (NDR), simple (SDR), preproliferative (PPDR), or proliferative (PDR). RESULTS: Examination of the cornea layer-by-layer with a confocal biomicroscope did not show any marked differences in morphology between diabetic and control subjects. The LSI (mean +/- SD) was 0.81 +/- 0.13, 0.87 +/- 0.09, 0.90 +/- 0.09, 0.90 +/- 0.13, and 1.02 +/- 0.25 in control subjects and in diabetic subjects with NDR, SDR, PPDR, or PDR, respectively; the light-scattering index of diabetic subjects with PDR was significantly greater than that of the control subjects (p = 0.001). An LSI greater than 1.0 was detected in 5.6, 6.3, 15.0, 15.4, and 50.0% of control subjects and of patients with NDR, SDR, PPDR, or PDR, respectively; the percentage of subjects with an LSI greater than 1.0 was significantly increased in diabetic patients with PDR than for control subjects. CONCLUSION/INTERPRETATION: These results suggest that the LSI increases with the stage of diabetic retinopathy, and that measurement of corneal light scattering could provide an index of basement membrane abnormality in people with diabetes.

Characterization of insulin-like growth factor-1 receptors in rabbit corneal epithelial cells.

Substance P (SP) and insulin-like growth factor-1 (IGF-1) synergistically facilitate corneal epithelial wound healing in vitro and in vivo. This synergism is mediated through the NK-1 receptors for SP, and IGF-1 does not modulate the binding affinity of NK-1 receptors. To clarify the effect of SP on the binding characteristics of IGF-1 receptors, the binding affinity and number of binding sites for IGF-1 in rabbit corneal epithelial cells were studied using a binding assay for(125)I-IGF-1. The binding affinity and number of binding sites for IGF-1 were determined by Scatchard plot analysis. Cultured rabbit corneal epithelial cells bound specifically to IGF-1. For IGF-1 in corneal epithelial cells, the binding affinity was 4 n m and the number of binding sites was 1x10(5)binding sites cell(-1). Although IGF-2 and insulin also bind to IGF-1 receptors, their affinities were, respectively, eight- and 300-fold lower than that of IGF-1. IGF-1 and IGF-2 stimulated corneal epithelial migration in the presence of SP, but insulin did not. Pretreatment of the corneal epithelial cells with SP (2x10(-5)m) failed to change the binding affinity or number of binding sites for IGF-1. These results demonstrated that corneal epithelial cells possess specific receptors for IGF-1. The synergistic effect of SP and IGF-1 on corneal epithelial wound healing does not result from regulation at the receptor level.

Hyaluronan facilitates corneal epithelial wound healing in diabetic rats.

We investigated the effect of hyaluronan on corneal epithelial wound healing in rats affected by diabetes. Furthermore, because hyaluronan is thought to affect corneal epithelial wound healing through the mechanism of binding of hyaluronan to provisional fibronectin in the wounded area, we compared the localization of fibronectin immunohistochemically during corneal epithelial wound healing in diabetic and non-diabetic rats. Streptozotocin was used to induce diabetes in half the rats. Two weeks after treatment, the whole corneal epithelium of diabetic and untreated rats was debrided. The rats were divided into groups (seven or eight rats per group), and hyaluronan eye drops at concentrations of 0.03, 0.1, or 0.3%, chondroitin sulfate (3%), or phosphate buffered saline (PBS) was given in eye drops 6 times a day for 4 days, starting immediately after debridement. The area of the corneal epithelial wound was measured immediately after debridement and at 12, 18, 24, 30, 48, 72, and 96 hours afterwards. Although the healing process was similar in non-diabetic and diabetic rats, the healing rate in diabetic rats was slower than that in normal controls. In both diabetic and non-diabetic rats, hyaluronan increased the healing rate in a dose-dependent manner; the difference was significant compared with the PBS-treated group, at hyaluronan doses of 0.1% and 0.3%. However, chondroitin sulfate did not affect corneal epithelial wound closure, regardless of whether the rats were diabetic or not; the healing rates were identical to those of PBS-treated diabetic and non-diabetic controls. In both diabetic and non-diabetic corneas, fibronectin was localized in the corneal subepithelial region, and in streaks between collagen fibers of the stroma. One day after debridement, a layer of fibronectin immunofluorescence was clearly visible on the surface of the denuded stroma. As healing progressed staining of fibronectin diminished at the interface between the new epithelium and the stroma. These changes in localization of fibronectin during corneal epithelial wound healing were similar in both diabetic and non-diabetic rats. Our results demonstrate that hyaluronan facilitates corneal epithelial wound healing in diabetic rats, and suggest that one possible mechanism of its stimulatory effect lies in its binding to a provisional fibronectin matrix, in both diabetic and non-diabetic rats.