Liu Tao, Li Bo, Zheng Xin-Feng, Jiang Sheng-Dan, Zhou Ze-Zhu, Xu Wen-Ning, Zheng Huo-Liang, Wang Chuan-Dong, Zhang Xiao-Ling, Jiang Lei-Sheng
Spine Center, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Department of Orthopedic Surgery, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Front Endocrinol (Lausanne). 2019 Jun 12;10:360. doi: 10.3389/fendo.2019.00360. eCollection 2019.
Chordin-like 1 (CHRDL1) is a secreted glycoprotein with repeated cysteine-rich domains, which can bind to BMPs family ligands. Although it has been reported to play important roles in several systems, the exact roles of CHRDL1 on human bone mesenchymal stem cells (hBMSCs) osteogenesis remain to be explored. The present study aimed to investigate the roles of CHRDL1 on the osteogenic differentiation of hBMSCs and the underlying molecular mechanisms. We found that CHRDL1 was upregulated during hBMSCs osteogenesis, and rhBMP-4 administration could enhance CHRDL1 mRNA expression in a dose and time dependent manner. Knockdown of CHRDL1 did not affect hBMSCs proliferation, but inhibited the BMP-4-dependent osteogenic differentiation, showing decreased mRNA expression levels of osteogenic markers and reduced mineralization. On the contrary, overexpression of CHRDL1 enhanced BMP-4 induced osteogenic differentiation of hBMSCs. Moreover, experiments by transplanting CHRDL1 gene modified hBMSCs into nude mice defective femur models displayed higher new bone formation in CHRDL1 overexpression groups, but lower new bone formation in CHRDL1 knockdown groups, compared with control groups. In consistent with the bone formation rate, there were increased CHRDL1 protein expression in new bone formation regions of defective femur in CHRDL1 overexpression groups, while reduced CHRDL1 protein expression in CHRDL1 knockdown groups compared with control groups. These indicate that CHRDL1 can promote osteoblast differentiation . Furthermore, the mechanisms study showed that CHRDL1 improved BMP-4 induced phosphorylation of SMAD1/5/9 during osteogenic differentiation of hBMSCs. Besides, promotion of osteogenic differentiation and the activation of SMAD phosphorylation by CHRDL1 can be blocked by BMP receptor type I inhibitor LDN-193189. In conclusion, our results suggested that CHRDL1 can promote hBMSCs osteogenic differentiation through enhancing the activation of BMP-4-SMAD1/5/9 pathway.
类脊索蛋白1（CHRDL1）是一种具有多个富含半胱氨酸结构域的分泌型糖蛋白，能够与骨形态发生蛋白（BMPs）家族配体结合。尽管已有报道称其在多个系统中发挥重要作用，但CHRDL1在人骨髓间充质干细胞（hBMSCs）成骨过程中的具体作用仍有待探索。本研究旨在探讨CHRDL1在hBMSCs成骨分化中的作用及其潜在分子机制。我们发现，在hBMSCs成骨过程中CHRDL1表达上调，并且重组人骨形态发生蛋白-4（rhBMP-4）给药能够以剂量和时间依赖的方式增强CHRDL1 mRNA表达。敲低CHRDL1不影响hBMSCs增殖，但抑制了BMP-4依赖的成骨分化，表现为成骨标志物的mRNA表达水平降低以及矿化减少。相反，CHRDL1过表达增强了BMP-4诱导的hBMSCs成骨分化。此外，将CHRDL1基因修饰的hBMSCs移植到裸鼠股骨缺损模型中的实验显示，与对照组相比，CHRDL1过表达组有更高的新骨形成，而CHRDL1敲低组新骨形成较少。与骨形成率一致，CHRDL1过表达组缺损股骨新骨形成区域的CHRDL1蛋白表达增加，而与对照组相比，CHRDL1敲低组的CHRDL1蛋白表达减少。这些表明CHRDL1可以促进成骨细胞分化。此外，机制研究表明，CHRDL1在hBMSCs成骨分化过程中增强了BMP-4诱导的SMAD1/5/9磷酸化。此外，I型BMP受体抑制剂LDN-193189可阻断CHRDL1促进的成骨分化和SMAD磷酸化激活。总之，我们的结果表明，CHRDL1可通过增强BMP-4-SMAD1/5/9信号通路的激活来促进hBMSCs成骨分化。
