Bone fractures are one of the most frequent injuries in the musculoskeletal system. Despite the best treatment efforts, a large proportion of bone fracture cases still display undesirable outcomes. Here, we verified that calcitonin gene-related peptide (CGRP), a 37-amino acid neuropeptides, might be a critical regulator that link the nervous, immune and skeletal systems during bone healing. We used a CGRP overexpression lentiviral system and stably transfected M2 macrophages. Then, we investigated the biological function and the intrinsic mechanisms of CGRP on M2 macrophages. We confirmed that CGRP downregulated osteogenic factors (BMP2, BMP6, WNT10b and OSM) secretion at first and promoted them late on (p < 0.05). In addition, we utilized an indirect coculture system and further ascertain the influences of CGRP-induced M2 macrophages on MC3T3 osteogenesis. The results implied that CGRP-modulated osteoimmune environment elicit multiple effects on osteogenesis of MC3T3 during the entire observation period. Notably, verteporfin, a yes-associated protein 1 (Yap1) inhibitor, impaired CGRP effects significantly in our experiments. Taken together, our findings illustrated that CGRP might regulate osteogenesis by modulating the osteoimmune response of M2 macrophages via Yap1.

骨骼骨折是肌肉骨骼系统中最常见的损伤之一。尽管进行了最佳的治疗，但大部分骨折病例仍显示出不良后果。在这里，我们验证了降钙素基因相关肽（CGRP），一种37个氨基酸的神经肽，可能是在骨愈合过程中连接神经，免疫和骨骼系统的关键调节剂。我们使用了CGRP过表达的慢病毒系统，并稳定转染了M2巨噬细胞。然后，我们研究了CGRP对M2巨噬细胞的生物学功能和内在机制。我们证实，CGRP首先下调了成骨因子（BMP2，BMP6，WNT10b和OSM）的分泌，并在后期促进了它们的形成（p <0.05）。此外，我们利用间接共培养系统，并进一步确定CGRP诱导的M2巨噬细胞对MC3T3成骨的影响。结果表明，在整个观察期间，CGRP调节的骨免疫环境对MC3T3的成骨作用引起多种影响。值得注意的是，在我们的实验中，Verteporfin是一种与Yes相关的蛋白1（Yap1）抑制剂，可显着损害CGRP效果。综上所述，我们的发现说明CGRP可能通过调节Yap1调节M2巨噬细胞的骨免疫反应来调节成骨作用。