Targeting Cathepsin K to Promoted Diabetic Wound Healing

Abstract

Impaired wound healing is serious complication of diabetes and is responsible for over 70,000 amputations annually in the United States. Increased degradation of extracellular matrix (ECM) proteins by elevated levels of proteases has been established as a key pathogenic factor in diabetic wounds. Collagen is the most abundant ECM in the wound, which aids healing by facilitating migration of dermal fibroblasts and keratinocytes and stimulating endothelial cell angiogenesis. The most potent collagenolytic and elastolytic protease in the mammalian species is the cysteine protease cathepsin K. This study was undertaken to explore the hypothesis that cathepsin K is elevated in diabetic wound and pharmacological inhibition of cathepsin K improves wound healing. To this end, 8mm excision skin wounds were made in wild type and db/db mice, and cathepsin K mRNA and protein levels were determined in the wound tissue by real‐time PCR and immunohistochemistry. In vitro monolayer wound closure assay was used to determine the effect of cathepsin K inhibitor‐II on migration of human fibroblasts under high glucose (20mM) conditions. Cathepsin K puncta and mRNA levels were significantly elevated in the wound tissue of db/db mice compared to that in the wild‐type mice. Migration of fibroblasts was significantly impaired when subjected to high‐glucose treatment, was reversed by cathepsin K inhibitor‐II. Even under basal (5mM glucose) conditions, treatment with cathepsin K inhibitor‐II augmented fibroblast migration. Collectively, these data demonstrate that cathepsin K is upregulated in the diabetic wound and inhibition of cathepsin K accelerates migration of fibroblasts, suggesting that pharmacological or genetic targeting of cathepsin K may represent a viable strategy to facilitate diabetic wound healing.