Combined effects of substance P and insulin-like growth factor-1 on corneal epithelial wound closure of rabbit in vivo

Purpose. We investigated the combined effects of substance P (SP) and insulin-like growth factor-1 (IGF-1) on corneal epithelial wound closure in vivo. Methods. The corneal epithelium of 16 rabbits was debrided by n-heptyl alcohol treatment; SP (1 mg/ml) and/or IGF-1 (1 mu g/ml) in phosphate-buffered saline (PBS) were administered immediately and at 2, 3, 6, 8, 10, 24, 26, 28, 30, 32, and 34 hours after debridement. Controls received PBS alone. The eyes were stained with fluorescein and photographed at baseline and at 6, 12, 18, 24, 30, 36, and 38 hours after debridement. The wound radii of the epithelial defects were recorded from hour 12 to hour 30, and the rate of healing was calculated by linear regression analysis. Results. The mean (+/- SD) healing rate in the control group was 57.03 +/- 7.88 mu m/h. The administration of SP or IGF-1 alone did not affect the healing rates, which were 55.49 +/- 2.49 and 55.57 +/- 7.14 mu m/hr, respectively. However, when SP and IGF-1 were combined, the mean healing rate was significantly higher (75.16 +/- 6.68 mu m/hr) than that of the control, SP-treated, or IGF-1-treated groups (p < 0.05). Conclusions. These results demonstrated that SP and IGF-1 synergistically affect corneal epithelial wound closure.