Objective: To preliminarily explore the mechanism of tensile stress regulating endochondral osteogenesis of condyle by analyzing the expression profiles of significantly different microRNAs (miRNAs) in exosomes of rat mandibular condylar chondrocytes (MCC) under quiescent and cyclic tensile strain (CTS) conditions. Methods: Rat condylar chondrocytes were cultured under static and CTS conditions respectively (10 SD rats, male, 2 weeks old), and exosomes were extracted. The two groups of exosomes were named as control group and CTS group respectively. The differential expression miRNAs were screened by high-throughput sequencing. Bioinformatics analysis and prediction of target genes related to osteogenesis were performed by TargetScan and miRanda website. Results: The exosomes of rat condylar chondrocytes cultured under tensile stress showed a "double concave disc" monolayer membrane structure, the expression of CD9 and CD81 were positive, and the particle size distribution accorded with the characteristics of exosomes, which was consistent with that of static cultured rat condylar chondrocytes. A total of 85 miRNAs with significantly different expression were detected by high-throughput sequencing (P<0.05). The main biological processes and molecular functions of differential miRNAs were biological processes and protein binding, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) database pathway enrichment analysis showed that there was significant enrichment in mammalian target of rapamycin (mTOR) signal pathway. The candidate target genes of miR-199a-5p include bone morphogenetic protein 3 (BMP3), endothelin converting enzyme 1, and miR-186-5p may target Smad8 and BMP3 to exert osteogenesis-related functions. Conclusions: Compared with static state, tensile stress stimulation can change the expression of miRNAs such as miR-199a-5p, miR-186-5p in the exocrine body of rat condylar chondrocytes, which can be considered as a mean to regulate the application potential of the exosomes.
目的： 分析静止和循环张应力条件下大鼠髁突软骨细胞（mandibular condylar chondrocytes，MCC）外泌体显著差异微RNA（microRNA，miRNA）的表达谱并探究张应力调节髁突软骨内成骨的作用机制。 方法： 分别选择5只2周龄雄性SD大鼠（共10只）在静止和循环张应力条件下培养大鼠MCC，提取细胞外泌体，两组外泌体分别命名为对照组和实验组。采用透射电子显微镜、纳米流式检测仪、纳米颗粒追踪分析等方法观察并鉴定，通过高通量测序筛选表达显著差异的miRNA，采用TargetScan、miRanda网站进行生物信息学分析及成骨相关靶基因预测。 结果： 实验组大鼠MCC外泌体均呈“双凹圆盘状”单层膜结构，CD9、CD81表达阳性，粒径分布符合外泌体特征，与对照组大鼠MCC外泌体一致。高通量测序筛选表达显著差异的miRNA共85个（P<0.05）。差异miRNA主要参与的生物学过程与分子功能分别为生物学过程和蛋白质结合；京都基因与基因组数据库通路富集分析显示在哺乳动物雷帕霉素靶蛋白信号通路有显著富集（P<0.05）。其中miR-199a-5p的候选靶基因有骨形态发生蛋白3（bone morphogenetic protein 3，BMP3）、内皮素转换酶-1，miR-186-5p可靶向Smad8、BMP3，以发挥成骨相关功能。 结论： 相比于静止状态，CTS刺激能改变大鼠MCC外泌体中miR-199a-5p、miR-186-5p等miRNA的表达量，可考虑作为调节外泌体应用潜能的一种手段。.