The hMetrnl-PLGA-PEG-PLGA Hydrogel Facilitates Skin Wound Healing Through Dual Regulation on eNOS Activity and Stability

<b>Background/Objectives:</b> Metrnl (Meteorin-like), a secreted protein identified in our lab, has been shown to promote wound healing in mice. However, current therapeutic strategies and the underlying mechanisms remain incompletely understood. This study aimed to (1) develop a recombinant human Metrnl (hMetrnl) hydrogel formulation for topical delivery, and (2) elucidate its molecular mechanism in wound repair. <b>Methods:</b> hMetrnl was dispersed in a thermosensitive PLGA-PEG-PLGA hydrogel (hMet-PPP) and applied topically to full-thickness skin wounds in male C57BL/6 mice. A large initial dose was administered on the day of injury, followed by a lower maintenance dose regimen. Mechanistic studies were performed using molecular/cellular assays to assess the effects of hMetrnl. <b>Results:</b> Administration of hMet-PPP significantly accelerated wound healing, reducing the initial wound area and shortening the overall recovery time. hMetrnl transmits signals to endothelial cells via the KIT receptor tyrosine kinase (C-Kit), a membrane receptor, thereby initiating a dual regulatory mechanism involving eNOS to promote angiogenesis: (1) rapid activation of eNOS activity within 30 min through the PI3K/AKT signaling pathway; and (2) suppression of proteasomal and lysosomal eNOS degradation, resulting in enhanced eNOS expression and prolonged functional activity under sustained treatment. <b>Conclusions:</b> Topical hMet-PPP administration represents a promising therapeutic strategy for enhancing early-stage wound healing. hMetrnl exerts its biological effects through C-Kit, which mediates dual regulation of eNOS, both activation and stabilization, providing a mechanistic basis for its potent angiogenic properties. These findings uncover a novel Metrnl mechanism with potential implications for the development of therapies targeting vascular dysfunction and tissue repair.