As a profoundly anabolic regulator of bone, Wnt7b is well acknowledged to enhance osteoblast activities. Here, we report that bone marrow mesenchymal stem cells (BMSCs) are another important population responding to Wnt7b. In this study, we systematically investigated the in vivo role of Wnt7b in BMSCs using transgenic mice, high‐throughput RNA‐seq, immunohistochemistry, RT‐qPCR, and in situ hybridization. These methods led us to uncover that Sox11 is induced via Wnt7b in BMSCs. Colony formation assay, flow cytometry, EdU incorporation labeling, RT‐qPCR, and Western blot were conducted to detect the self‐renewal capacity of BMSCs. Alkaline phosphatase staining, alizarin red staining, and ex vivo BMSCs transplantation were utilized to detect the osteogenic ability of BMSCs. ChIP‐qPCR, shRNAs, and immunofluorescence staining were utilized to investigate the underlying mechanisms. Consequently, bone‐derived Wnt7b was found to decrease in osteoporosis and elevate in bone fracture healing. During bone fracture healing, Wnt7b was particularly expressed in the mesenchymal cells residing within healing frontiers. RNA‐seq data of Wnt7b‐overexpressed bones uncovered the significant upregulation of Sox11. Histological results further unveiled that Sox11 is specifically increased in BMSCs. Wnt7b‐induced Sox11 was demonstrated to reinforce both self‐renewal and osteogenic differentiation of BMSCs. Mechanistically, Wnt7b activates the Ca2+‐dependent Nfatc1 signaling to directly induce Sox11 transcription, which in turn activates the transcriptions of both proliferation‐related transcription factors (Ccnb1 and Sox2) and osteogenesis‐related factors (Runx2, Sp7) in BMSCs. It is intriguing that this Wnt7b‐Sox11 signaling in BMSCs is β‐Catenin‐independent. Overall, this study provides brand new insights of Wnt7b in bone formation, namely, Wnt7b can enhance both self‐renewal and osteogenic differentiation of BMSCs via inducing Sox11. These findings present a new crosstalk between Wnt and Sox signaling in BMSCs.

中文翻译：

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Wnt7b 诱导的 Sox11 功能增强骨髓间充质干细胞的自我更新和成骨承诺

作为一种深刻的骨合成代谢调节剂，Wnt7b 被公认为增强成骨细胞活性。在这里，我们报告骨髓间充质干细胞 (BMSCs) 是另一个对 Wnt7b 有反应的重要群体。在这项研究中，我们使用转基因小鼠、高通量 RNA-seq、免疫组织化学、RT-qPCR 和原位杂交系统地研究了 Wnt7b 在 BMSCs 中的体内作用。这些方法使我们发现 Sox11 是通过 BMSC 中的 Wnt7b 诱导的。进行集落形成测定、流式细胞术、EdU 掺入标记、RT-qPCR 和蛋白质印迹以检测 BMSCs 的自我更新能力。碱性磷酸酶染色、茜素红染色和离体骨髓间充质干细胞移植用于检测骨髓间充质干细胞的成骨能力。ChIP-qPCR、shRNA、和免疫荧光染色被用来研究潜在的机制。因此，发现骨源性 Wnt7b 减少骨质疏松症并提高骨折愈合率。在骨折愈合过程中，Wnt7b 特别在位于愈合边界内的间充质细胞中表达。Wnt7b 过表达骨骼的 RNA-seq 数据揭示了 Sox11 的显着上调。组织学结果进一步揭示了 Sox11 在 BMSC 中特别增加。Wnt7b 诱导的 Sox11 被证明可以增强 BMSCs 的自我更新和成骨分化。从机制上讲，Wnt7b 激活 Ca2+ 依赖的 Nfatc1 信号直接诱导 Sox11 转录，进而激活 BMSC 中增殖相关转录因子（Ccnb1 和 Sox2）和成骨相关因子（Runx2、Sp7）的转录。有趣的是，BMSCs 中的这种 Wnt7b-Sox11 信号是 β-连环蛋白独立的。总的来说，这项研究为 Wnt7b 在骨形成中提供了全新的见解，即 Wnt7b 可以通过诱导 Sox11 来增强 BMSCs 的自我更新和成骨分化。这些发现提出了 BMSC 中 Wnt 和 Sox 信号之间的新串扰。