Activin B Regulates Fibroblasts to Promote Granulation Tissue Formation and Angiogenesis During Murine Skin-Wound Healing via the JNK/ERK Signaling Pathway

Fibroblasts determine repair quality during skin-wound healing. Our previous study found that Activin B promotes keratinocyte proliferation and migration, facilitating re-epithelialization. However, specific mechanisms governing fibroblast function during wound healing remain unclear. Here, we aimed to elucidate the mechanism by which Activin B regulates fibroblast activity during skin-wound healing. Using a murine skin-wound model, we performed hematoxylin-eosin, immunohistochemical, and Masson's trichrome staining to evaluate Activin B's effects on granulation tissue formation, angiogenesis, and collagen fiber synthesis. We assessed Activin B's effects on fibroblast proliferation, migration, and collagen protein synthesis and investigated signaling pathway mechanisms in vitro. Animal experiments showed that Activin B accelerated wound healing by promoting granulation tissue regeneration and angiogenesis without affecting collagen fibers and Type I collagen synthesis. In vitro experiments demonstrated that Activin B modulates fibroblast proliferation and migration by activating JNK and ERK signaling pathways. Activin B may enhance angiogenesis by stimulating fibroblasts to secrete vascular endothelial growth factor, which induces dermal microvascular endothelial cell proliferation, promoting angiogenesis. Thus, we elucidated the dual regulatory paradigm of Activin B in fibroblasts; Activin B drives proliferation and migration via JNK/ERK signaling but does not directly regulate collagen synthesis.