Vitamin D promotes wound healing in aged skin by modulating inflammation, angiogenesis, and EMT via the Hippo pathway

Abstract

Age-related impairment in skin wound healing represents a significant healthcare challenge. Vitamin D (VD) has been shown to enhance diabetic wound healing. However, its therapeutic potential in age-related wound healing deficits remains unexplored. Here, we investigated VD’s impact on wound healing in aged mice and the underlying mechanisms. Twelve-month-old C57BL/6 J mice received VD supplementation for 3 months before full-thickness excisional wounds were created. Wound healing was evaluated through multiple aspects, including inflammation, angiogenesis, epithelial-mesenchymal transition (EMT), and the Hippo signaling pathway. We also examined responses to 1α,25(OH)₂D₃ in HaCaT cells. VD supplementation significantly accelerated wound closure by modulating several key processes. It promoted inflammation resolution by suppressing pro-inflammatory factors (IL-6, TNF-α), elevating IL-10 levels, and facilitating M1-to-M2 macrophage polarization. VD enhanced angiogenesis through increased CD31-positive vessel formation and upregulation of angiogenic factors (VEGF, VEGFR2, PDGF). It also promoted EMT, as evidenced by reduced epithelial markers, increased mesenchymal markers, and upregulated EMT-related transcription factors. Mechanistically, VD inactivated the Hippo pathway, shown by downregulated Mst1 and Lats1 expressions, decreased p-YAP protein levels, increased YAP and TAZ protein levels, and upregulated target gene expressions (Cyr61). In vitro studies using HaCaT cells confirmed that 1α,25(OH)₂D₃ promoted cell migration and EMT through Hippo pathway modulation, as these effects were abolished after verteporfin (YAP inhibitor) treatment. Our findings demonstrated that VD supplementation effectively accelerated wound healing in aged skin by modulating inflammation, increasing angiogenesis, and promoting EMT via the Hippo pathway, suggesting VD as a promising therapeutic strategy for managing age-related wound healing deficits.