microRNA-126-5p在骨质疏松中的调控作用及机制研究

Osteoporosis is one of the most common age-related diseases, often leading to lumbar back pain and compression fracture, seriously impacting on the quality of life. MiRNAs have been confirmed to play a key role in osteoporosis occurrence and development. However, the related molecular mechanism still needs further study. By using the miRNA chip analysis in cell lines and the qRT-PCR analysis in clinical samples, we found that miR-126-5p was significantly down-regulated in the plasma of patients with osteoporosis. Further study showed that the deficiency of miR-126-5p led to obvious reduced bone mass by using the miR-126-5p knockout mouse model. In addition, we found that estrogen could promote the expression of miR-126-5p in osteoclasts and further stimulate the secretion of miR-126-5p by exosomes, while these exosomes could significantly evaluate the level of miR-126-5p in osteoblasts. These results indicate that exosomes may play an important role in the effect of miR-126-5p in osteoporosis. Next, we plan to investigate the up-regulation of miR-126-5p and the transport effect of exosomes to miR-126-5p in osteoporosis, and further clarify the molecular mechanism during the process of miR-126-5p regulating osteoporosis. This study is an important supplement on the pathogenesis of osteoporosis, and will further provide insight into the new drug target in the treatment of osteoporosis.

骨质疏松症是最常见的老年性疾病之一，常导致腰背部疼痛、压缩性骨折等，严重影响患者生活质量。MiRNA已被证实参与骨质疏松的发生和发展，但相关分子机制仍有待进一步研究。本课题组前期通过miRNA芯片及临床样本分析发现miR-126-5p在骨质疏松患者血浆中呈低表达，并通过构建miR-126-5p敲除鼠模型证实miR-126-5p可导致骨量减少。进一步研究发现雌激素可促进破骨细胞miR-126-5p的表达并以外泌体的形式分泌及向成骨细胞转运，从而提高成骨细胞内miR-126-5p的水平，这可能是miR-126-5p在骨质疏松中发挥作用的重要分子机制。以此为基础，本项目拟在分子、细胞和动物水平重点探讨雌激素促进miR-126-5p表达及外泌体对miR-126-5p的转运在骨质疏松中的调控作用和分子机制。本项目不仅为骨质疏松症的病因学研究提供重要的理论基础，而且为其治疗提供新的理论依据及分子靶点。

骨质疏松症是最常见的老年性疾病之一，随着我国人口老龄化进程的加速，我国已成为骨质疏松发病率最高的国家之一。骨质疏松症常导致腰背部疼痛、压缩性骨折等，严重影响患者生活质量。在此次研究中，我们发现在骨质疏松患者的血浆和骨组织中miR-126-5p均呈显著下降，且miR-126-5p的水平与骨密度呈一定的相关性。且雌激素可能通过激活Notch通路促进miR-126-5p的表达，从而发挥作用。研究也发现TGF-β，一种在骨基质中大量存在，并在骨破坏过程中释放的细胞因子，可显著抑制miR-126-5p的表达，说明miR-126-5p在骨质疏松中的降低可能受到多种原因的影响。我们的前期研究已证实PTHrP和MMP13是miR-126-5p的靶基因，此次研究中，我们进一步明确了miR-126-5p对RUNX2表达和其3’UTR区域的抑制作用，并明确了作用位点。利用构建成功的miR-126-5p基因敲除小鼠，提取其BMM细胞和BMSC细胞进行条件共培养后，发现miR-126-5p敲除的BMSC对野生型BMM细胞向破骨细胞分化的诱导作用明显加强，对miR-126-5p基因敲除小鼠的检测也进一步证实了miR-126-5p敲除可导致骨质疏松，并促进RUNX2、PTHrP和MMP13的表达。且对OVX骨质疏松小鼠模型通过尾静脉注射miR-126-5p可显著抑制骨质疏松的发生，说明miR-126-5p可能在体内发挥治疗骨质疏松的作用。同时，我们发现外泌体参与了miR-126-5p在破骨细胞和成骨细胞间的细胞运输，且含miR-126-5p的外泌体也可在体内发挥一定抑制骨质疏松的作用。这些研究结果说明说明miR-126-5p可能单独或联合其它指标作为骨质疏松诊断和严重程度评判的标准之一，且可能作为骨质疏松症新的临床治疗靶点。