Li Xiaoyan, Guo Lijia, Liu Yitong, Su Yingying, Xie Yongmei, Du Juan, Zhou Jian, Ding Gang, Wang Hao, Bai Yuxing, Liu Yi
Laboratory of Tissue Regeneration and Immunology and Department of Periodontics, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, PR China.
Department of Orthodontics School of Stomatology, Capital Medical University, PR China.
Biochem Biophys Res Commun. 2017 Nov 18;493(2):928-933. doi: 10.1016/j.bbrc.2017.09.119. Epub 2017 Sep 22.
Bone marrow mesenchymal stem cells (BMMSCs) are pluripotent stem cells, and the osteogenic differentiation of BMMSCs has been drawing attention for a long time. Bone formation is regulated by numerous molecular and cellular signaling pathways, and the differentiation of BMMSCs is controlled by a well-defined genetic program. In the present study, we isolated BMMSCs from the bone cavities of wild-type (WT) and microRNA-21 knock-out (miR-21-KO) mice and found that miR-21 was significantly upregulated during the osteogenic differentiation of BMMSCs. Under osteoinductive conditions, ALP staining and alizarin red staining showed that the bone formation of BMMSCs from miR-21-KO mice was less than that of BMMSCs from WT mice. Consistently, RT-PCR and western blotting revealed that ALP and Runx2 expression levels in miR-21-KO mice were downregulated compared with those in WT mice. Meanwhile, the calvarial bone defects of miR-21-KO mice showed less newly formed bone than did those of WT mice. Additionally, the Smad7-Smad1/5/8-Runx2 axis showed the same tendency; Smad7 overexpression and the expression of phosphorylated Smad1/5/8 complex decreased when miR-21 was knocked down. We identified a novel mechanism by which microRNA-21 (miR-21) promotes the bone formation of BMMSCs and found that this process is regulated, in part, by the Smad7-Smad1/5/8-Runx2 pathway.
骨髓间充质干细胞（BMMSCs）是多能干细胞，BMMSCs的成骨分化长期以来一直备受关注。骨形成受众多分子和细胞信号通路调控，BMMSCs的分化由明确的遗传程序控制。在本研究中，我们从野生型（WT）和微小RNA-21基因敲除（miR-21-KO）小鼠的骨腔中分离出BMMSCs，发现miR-21在BMMSCs成骨分化过程中显著上调。在骨诱导条件下，碱性磷酸酶（ALP）染色和茜素红染色显示，miR-21-KO小鼠的BMMSCs骨形成少于WT小鼠的BMMSCs。同样，逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹法显示，与WT小鼠相比，miR-21-KO小鼠中ALP和Runx2的表达水平下调。同时，miR-21-KO小鼠的颅骨缺损处新形成的骨组织比WT小鼠的少。此外，Smad7-Smad1/5/8-Runx2轴也呈现相同趋势；当miR-21被敲低时，Smad7过表达以及磷酸化Smad1/5/8复合物的表达降低。我们确定了一种新机制，即微小RNA-21（miR-21）促进BMMSCs的骨形成，并且发现这一过程部分受Smad7-Smad1/5/8-Runx2途径调控。
