Corneal erosions/abrasions ranging from superficial defects to full thickness epithelial lesions are found in 50% of diabetic patients, and this condition is termed diabetic keratopathy. Moreover, difficulty with corneal re-epithelialization and persistent epithelial defects/recurrent erosions is associated with the use of donor corneas from diabetic patients, and with corneal epithelial removal during vitrectomy in diabetic individuals. Such corneal epithelial defects can result in infectious corneal ulcers, secondary scarring, and loss of vision. Compelling evidence shows that blockade of opioid-receptor interactions by the opioid antagonist, naltrexone (NTX), restores corneal epithelial wound healing in uncontrolled diabetes. This grant is designed to make the transition from bench to bedside and explores the hypothesis that topical application of NTX will prevent and/or ameliorate corneal epithelial wound healing complications related to Type 1 diabetes. A multi-disciplinary research team consisting of a basic scientist, two ophthalmologists, and a biostatistician have formed a partnership in order to reach the full therapeutic potential of this advance in cell and molecular biology. In the R21 phase (with completion in the R33 phase), this hypothesis is tested in animal models of well-controlled Type 1 diabetes as to the toxicity and efficacy of NTX in the homeostatic (unwounded) and injured corneal epithelium. In order to prepare for FDA requirements, two species of animals are utilized: rat and rabbit. The grant utilizes a well-documented and reliable model of corneal re-epithelialization in the rat and rabbit, induction of Type 1 diabetes by injection of streptozotocin (STZ) (rats) or alloxan (rabbits), and subcutaneous insulin pellets to maintain normoglycemia. The R21 studies the effects of NTX on uninjured (Specific Aim #1) and injured (Specific Aim #2) corneal epithelium of rats, and the uninjured rabbit corneal epithelium (Specific Aim #3). The R33 investigates the safety and efficacy of NTX treatment in corneal abrasions in the diabetic rabbit (Specific Aim #1). If the animal experiments successfully show a non-toxic dose with efficacy, we will perform due diligence testing under the guidelines of the Food and Drug Administration (Specific Aim #2). These data will be used to secure an IND number in order to pursue clinical trials, and as evidence for Institutional Review Board approval to conduct Phase I clinical trials. The proposed use of biotherapy with NTX is an innovative approach whereby the patient's own growth regulatory mechanisms are manipulated to correct complications from diabetes.
