[Expression profile of microRNA secreted by rat condylar chondrocytes under tensile stress]

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.