Alteration of circRNA Expression in rDFCs During Osteogenic Differentiation

Circular RNAs (circRNAs) are novel among noncoding RNAs and play crucial roles in various biological processes. However, little is known about the functions of circRNAs during osteogenic differentiation. The current study aimed to investigate the differential expression of circRNAs in rat dental follicle cells (rDFCs) upon osteogenic medium culture. Those potential circRNAs were identified by RNA high-throughput sequencing and quantitative real-time polymerase chain reaction (qRT-PCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to further explore circRNA biofunctions. 266 differentially-expressed circRNAs were revealed and involved in several important signaling pathways, which include MAPK and TGF-β signaling pathways. Among these, circFgfr2 and its predicted downstream targets, miR-133 and BMP6, were identified both in vivo and in vitro. For further validation, circFgfr2 was overexpressed during osteogenic differentiation, bringing about the down-regulation of miR-133 and the up-regulation of BMP6. Taken together, the results revealed the circRNA expression profiles and indicate the importance of circRNAs during the osteogenic differentiation of rDFCs. In addition, circFgfr2 might promote osteogenesis by controlling miR-133/BMP6, which possibly provide new target to manipulate tooth regeneration and bone formation.环状RNA（circular RNAs, circRNAs）是一类新兴的非编码RNA（noncoding RNAs），在多种生物学过程中发挥关键作用。然而，目前对于成骨分化过程中circRNAs的功能仍知之甚少。本研究旨在探究大鼠牙囊细胞（rat dental follicle cells, rDFCs）在成骨培养基培养条件下的circRNAs差异表达情况。研究通过RNA高通量测序与实时荧光定量聚合酶链式反应（quantitative real-time polymerase chain reaction, qRT-PCR）筛选鉴定得到潜在circRNAs，并采用基因本体论（Gene Ontology, GO）与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集分析进一步探索circRNAs的生物学功能。结果共鉴定出266个差异表达circRNAs，这些circRNAs参与了包括丝裂原活化蛋白激酶（MAPK）通路、转化生长因子-β（TGF-β）通路在内的多条重要信号通路。其中，circFgfr2及其预测的下游靶标miR-133与骨形态发生蛋白6（BMP6）在体内与体外实验中均得到验证。为进一步验证该调控轴，本研究在成骨分化过程中过表达circFgfr2，导致miR-133表达下调、BMP6表达上调。综上，本研究揭示了rDFCs成骨分化过程中的circRNAs表达谱，证实了circRNAs在rDFCs成骨分化中的重要作用。此外，circFgfr2可能通过调控miR-133/BMP6轴促进成骨过程，这为牙齿再生与骨形成的干预提供了全新的潜在靶点。