Pathogenic Role of Diabetes-Induced Overexpression of Kallistatin in Corneal Wound Healing Deficiency Through Inhibition of Canonical Wnt Signaling

It was reported previously that circulation levels of kallistatin, an endogenous Wnt signaling inhibitor, are increased in patients with diabetes. The current study was conducted to determine the role of kallistatin in delayed wound healing in diabetic corneas. Immunostaining and Western blot analysis showed kallistatin levels were upregulated in corneas from humans and rodents with diabetes. In murine corneal wound healing models, the canonical Wnt signaling was activated in nondiabetic corneas and suppressed in diabetic corneas, correlating with delayed wound healing. Transgenic expression of kallistatin suppressed the activation of Wnt signaling in the cornea and delayed wound healing. Local inhibition of Wnt signaling in the cornea by kallistatin, an LRP6-blocking antibody, or the soluble VLDL receptor ectodomain (an endogenous Wnt signaling inhibitor) delayed wound healing. In contrast, ablation of the VLDL receptor resulted in overactivation of Wnt/β-catenin signaling and accelerated corneal wound healing. Activation of Wnt signaling in the cornea accelerated wound healing. Activation of Wnt signaling promoted human corneal epithelial cell migration and proliferation, which was attenuated by kallistatin. Our findings suggested that diabetes-induced overexpression of kallistatin contributes to delayed corneal wound healing by inhibiting the canonical Wnt signaling. Thus, kallistatin and Wnt/β-catenin signaling in the cornea could be potential therapeutic targets for diabetic corneal complications.