miR‐185‐5p Derived From hUC‐MSC Exosomes via Suspension Culture Under Hypoxic Conditions Promotes Scarless Wound Healing in Mice by Precisely Regulating Collagen I/III Regeneration

ABSTRACT Hypertrophic scars have long posed a significant challenge in wound healing, primarily because of an imbalance between Type I (COL‐I) and Type III (COL‐III) collagen caused by excessive fibroblast activation. Existing treatments cannot directly regulate collagen formation to intervene in scar hyperplasia. This study is the first to elucidate the key mechanism through which human umbilical cord‐derived mesenchymal stem cell (hUC‐MSCs) exosomes expressing miR‐185‐5p achieve scarless healing through remodeling of the collagen‐type ratio. In this method, a hypoxic three‐dimensional (3D‐HO) suspension culture system that more closely mimics the in vivo microenvironment was established, and functional exosomes with enhanced physiological activity and higher yields were harvested. In vivo experiments demonstrated that 3D‐HO exosomes significantly improved the COL‐III/COL‐I regeneration ratio during mouse wound healing. Mechanistic studies revealed that the RhoA/YAP signaling axis plays a key regulatory role in the collagen regeneration ratio. Further molecular analysis revealed enrichment of miR‐185‐5p in 3D‐HO exosomes, which directly target RhoA to regulate fibroblasts. Both in vivo and in vitro functional interventions confirmed miR‐185‐5p in maintaining collagen type balance. In summary, this study demonstrates that microenvironment‐enhanced hUC‐MSCs exosomes remodel the composition of different types of collagen via the miR‐185‐5p–RhoA/YAP signaling axis, thereby driving scarless healing.