Mechanisms Of VEGF-B In The Promotion Of Corneal Nerve Fiber Regeneration In Diabetic Mice

Purpose Through in vitro(Trigeminal ganglion neurons) and in vivo(streptozotocin induced diabetic mice) experiments, observing the function of Vascular endothelial growth factor-B)(VEGF-B)in corneal epithelial repair and nerve fibers regeneration of diabetic model mice, and investigating its mechanism.Methods In this study, diabetic mice were induced by using streptozotocin(STZ), and age matched C57/BL6 mice were chosen as control. The corneal epithelial wound healing model was established and administrated with subconjunctival injection with VEGF-B., The expression of endogenous VEGF-B in intact and regenerated corneal epithelium were evaluated in normal and diabetic mice. The effects of exogenous VEGF-B on diabetic corneal epithelial wound healing and corneal nerve regeneration were evaluated. Mouse trigeminal ganglion cells were cultured in this experiment. The effects of exogenous VEGF-B on TG cell neurite outgrowth were analyzed. The signaling pathway that mediating VEGF-B's function was investigated by Western blots.Results With prolonged hyperglycemia duration, the corneal sensitivity is decreased. The whole-mount corneal staining showed that the nerve ending density in corneal epithelium was significantly decreased in diabetic mice than that of normal mice. Endogenous expression of VEGF-B in the regenerated corneal epithelium of normal mice showed significant upregulation than that of normal mice, while hyperglycemia attenuated the endogenous expression of VEGF-B in regenerated diabetic corneal epithelium. Exogenous VEGF-B application promoted corneal nerve regeneration and epithelial regeneration in both normal and diabetic mice in vivo. Moreover, VEGF-B improved diabetic corneal sensation.In vitro, TG neurons from diabetic and normal mice were cultured to explore the role of VEGF-B. VEGF-B treatment attenuated ROS accumulation and mitochondrial superoxide generation, accompanied by the recovery of mitochondrial membrane potential. VEGF-B enhanced neurite elongation in TG neurons, through the reactivation of PI-3K/Akt-GSK3?-m TOR signaling via the VEGF receptor-1 and neuropilin-1.Conclusion Hyperglycemia suppressed endogenous VEGF-B expression in regenerated corneal epithelium of diabetic mellitus, while exogenous VEGF-B promoted corneal nerve fiber regeneration in diabetic mice through reactivating PI-3K/Akt-GSK-3?-m TOR signaling and attenuating neuronal oxidative stress.