Abstract
Despite the prevalence of diabetic retinopathy, the majority of adult diabetic patients develop visually debilitating corneal complications, including impaired wound healing. Unfortunately, there is limited treatment for diabetes-induced corneal damage. The current project investigates a novel, peptide-based combination therapy, thymosin beta-4 and vasoactive intestinal peptide (Tβ4/VIP), against high-glucose-induced damage to the corneal epithelium. Electric cell-substrate impedance sensing (ECIS) was used for real-time monitoring of barrier function and wound healing of human corneal epithelial cells maintained in either normal glucose (5 mM) or high glucose (25 mM) ± Tβ4 (0.1%) and VIP (5 nM). Barrier integrity was assessed by resistance, impedance, and capacitance measurements. For the wound healing assay, cell migration was also monitored. Corneal epithelial tight junction proteins (ZO-1, ZO-2, occludin, and claudin-1) were assessed to confirm our findings. Barrier integrity and wound healing were significantly impaired under high-glucose conditions. However, barrier function and cell migration significantly improved with Tβ4/VIP treatment. These findings were supported by high-glucose-induced downregulation of tight junction proteins that were effectively maintained similar to normal levels when treated with Tβ4/VIP. These results strongly support the premise that Tβ4 and VIP work synergistically to protect corneal epithelial cells against hyperglycemia-induced damage. In addition, this work highlights the potential for significant translational impact regarding the treatment of diabetic patients and associated complications of the cornea.