HuR/BMP/Runx2信号轴调控骨髓间充质干细胞成骨分化的作用与机制研究

Bone loss is a common lesion in orthopaedics, how to promote bone regeneration and repair remains tough in clinical treatment. Bone marrow mesenchymal stem cells (BMSC) are ideal candidates for stem cell transplantation to treat bone loss and promote bone regeneration and repair, due to their potential of osteogenic differentiation, easy access to specimen, easy amplification and low immunogenicity. Previous studies have shown that BMP family proteins and the transcription factor Runx2 play an important role in osteogenic differentiation of BMSC. Recent studies have found that the RNA binding protein HuR in vascular smooth muscle cells can competitively bind with miRNA to up-regulate the expression of BMP-2. The applicant's preliminary experiment found that HuR significantly promoted the expression of various BMP proteins and Runx2 in BMSC, as well as the osteogenic differentiation, but the specific molecular mechanism was still unclear. Therefore, we propose the scientific hypothesis that HuR promoted BMSC osteogenic differentiation and mineralization by activating the BMP/Runx2 signaling axis. The purpose of this study is to explore the molecular mechanism of HuR in promoting BMPs and Runx2 expression in cell models, and to clarify its role in osteoblastic repair in animal models. This study will further enrich the regulatory mechanism of BMSC osteogenic differentiation, and provide new ideas for the clinical treatment of bone loss or bone defects.

骨质丢失是骨科的常见病损，如何促进骨再生与修复是临床治疗的难题。骨髓间充质干细胞（BMSC）因具有成骨分化潜能以及取材方便、易于扩增、低免疫原性等优点，成为干细胞移植治疗骨质丢失和促进骨再生与修复的理想选择。既往研究显示，BMP家族蛋白与转录因子Runx2在BMSC成骨分化中发挥重要作用。最近研究发现，血管平滑肌细胞内RNA结合蛋白HuR能够与miRNA竞争性结合从而上调BMP-2的表达。申请人预实验发现，HuR显著促进BMSC内多种BMP蛋白与Runx2的表达以及成骨分化，然而其具体分子机制仍不清楚。由此我们提出科学假设：HuR通过激活BMP/Runx2信号轴，从而促进BMSC成骨分化与矿化。本课题拟在细胞模型中探讨HuR促进BMPs与Runx2表达的分子机制，并明确其在动物模型中的成骨修复作用。本研究将进一步丰富BMSC成骨分化的调控机制，为临床上治疗骨质丢失或骨缺损疾病提供新的思路。

如何有效促进骨髓间充质干细胞（BMSC）向成骨方向分化是骨组织再生与修复重建领域的研究重点。HuR作为一种RNA结合蛋白，能够识别并结合至靶基因mRNA 3’UTR区域，从而促进mRNA分子稳定性与靶基因的表达。然而，关于HuR在BMSC成骨分化调控方面的作用尚未见报道。本研究围绕科学假设“HuR通过激活BMP/Runx2信号轴，从而促进BMSC成骨分化与矿化”进行。研究结果发现：（1）RNA结合蛋白HuR促进hBMSC的成骨分化；（2）HuR上调hBMSC多种BMP家族蛋白、转录因子Runx2以及ALP、COL1A1、OCN等成骨标志物的表达；（3）HuR通过结合至BMP-2与Runx2 mRNA 3’UTR并提升其mRNA稳定性从而上调BMP-2与Runx2的表达；（4）HuR过表达hBMSC移植能够延缓小鼠骨质疏松，以上结果阐明了HuR促进hBMSC成骨分化的作用和分子机制。此外，本研究对原课题内容进一步深化拓展，发现：成骨标志物如SPARC、SPP1和BGLAP（OCN）等，具有预测不同癌症病人生存与预后的价值，其机制可能与肿瘤微环境中DC的捕获和功能障碍相关，并提示成骨标志物SPARC、SPP1和BGLAP可能成为肿瘤免疫治疗的潜在靶点。通过开展本研究项目，我们进一步揭示和丰富了hBMSC成骨分化的潜在调控机制，为临床上治疗骨质疏松/骨缺损提供新的思路和科学依据。