The Abnormal Expression Of IGF-1 In Corneal Wound Healing Of Diabetes Rats

PURPOSE:Delayed wound healing in diabetic cornea result in significant morbidity, prolonged hospitalization, and enormous health-care expenses. The aim of this study was to explore the expression of IGF-1 in corneal wound healing of diabetic rats.METHOD:1. Animals and induction of DM:Male Wistar rats (approximately 170-225g, n=35) were injected with 55 mg/kg of streptozocin, serum glucose levels were monitored from the tail vein at 48 hours after the injection of streptozocin. Rats injected with citrate buffer were considered healthy (n=30).2. Corneal Abrasions:A 5-mm-diameter circle was outlined in the center of the cornea with a trephine, and the encircled corneal epithelium was removed with a No.15 Bard-Parker scalpel blade.3. Photographs were taken immediately after epithelium debridement (Oh,12h,24h,36h,48h,60h and72h). The area of defect was determined using software and was calculated as the percentage of the original epithelial defect.4. The expression of IGF-1 was analyzed by HE, RT-PCR and immunofluorescence.RESULTS:1. Rats with DB weighed significantly less (approximately 25.8%, P<0.01) than healthy rats beginning at week 1 and continuing throughout the 8-week study. Rats with DB had glucose levels greater than 18.43±1.04 mmol/L which was significantly higher than that in healthy rats (P<0.01).2. Healthy rats had corneal wounds that re-epithelialized significantly faster than DB rats at 24,36,48 and 60 hours (P<0.01).3. Normal rats had the transparent healed corneas. Corneal wound healing in diabetic rats was delayed with appearing cloudy and HE staining of corneal sections showed stromal edema with numerous clefts and inflammatory cells and neo-vessels, particularly at the margins of the corneas. Moreover, the epithelial layer appeared to be detached from the corneal surface in some diabetic corneas.4. RT-PCR showed that the expression of IGF-1mRNA in diabetic cornea was 4.8-fold lower that expression in non-diabetic wounds at day 2,1.6-fold lower at day 3, and 2.2-fold lower at day 4.5. There was no IGF-1 expression in normal rat cornea while little IGF-1 expression was found in epithelium and stroma in diabetic rat. After corneal injury, in the new covering epithelium and stroma of wound area, IGF-1 expression firstly appeared at Id, reached peak level at 3d and decreased at 5d in normal rat cornea. In diabetic cornea, IGF-1 tends to increase at 1d, reached peak level at 3d and decreased at 5d in normal rat cornea. IGF-1 expression in diabetic wounded cornea was significant lower than that in normal wounded cornea (P<0.01). Expression of IGF-1 in diabetic wounded cornea was 4.6-fold lower that expression in normal wounded cornea at day 1,2.2-fold lower at day 3, and 2.4-fold lower at day 7.CONCLUSION:Diabetic rats have impaired wound healing in cornea that is accompanied by a delay and reduction of the expression of IGF-1. Delayed wound healing in diabetic cornea may be associated with the abnormal expression of IGF-1 and impaired inflammatory reaction.