Myokine Irisin promotes osteogenesis by activating BMP/SMAD signaling via αV integrin and regulates bone mass in mice
Yuan Xue, Sihan Hu, Chichi Chen, Jiachen He, Jie Sun, Yesheng Jin, Yuanshu Zhang, Guo‐Qing Zhu, Qin Shi, Yongjun Rui
Abstract
Irisin is well-known to contribute to bone homeostasis due to its bidirectional regulation on osteogenesis and osteoclastogenesis. However, the mechanisms of irisin involved in mesenchymal stem/stromal cells (MSCs)-derived osteogenesis are still under investigated. Fibronectin type III domain-containing protein 5 (FNDC5) is the precursor protein of irisin, compare with wild type (WT) littermates, FNDC5 -/-mice lost bone mass significantly, collectively evidenced by the decrease of bone mineral density (BMD), impaired bone formation and reduced N-terminal propertied of type I procollagen (P1NP) in sera. Meanwhile, the bone resorbing of FNDC5 -/-mice has enhanced accompanied by increased tartrate phosphatase (TRAP) staining cells morphologically and cross-Linked C-telopeptide of type 1 collagen (CTX) level in sera. In vitro study showed that lack of irisin impeded the MSC-derived osteogenesis of FNDC5 -/-mice. The addition of irisin promote the osteogenesis of WT and irisin-deficient MSCs, by activating V integrin-induced ERK/STAT pathway, subsequently enhancing bone morphogenetic protein 2 (BMP2) expression and BMP/SMAD signaling activation. Taken together, these findings further indicate that irisin regulates bone homeostasis. Moreover, irisin promotes MSC-derived osteogenesis by binding to V integrin and activating BMP/SMAD signaling consequently. Thus, irisin may be a promising therapeutic target for osteoporosis and bone defects.