miR-105/Runx2 axis mediates FGF2-induced ADAMTS expression in osteoarthritis cartilage

Fibroblast growth factor 2 (FGF2) plays an important role in the development of osteoarthritis (OA) through the regulation of cartilage degradation. However, the molecular mechanism underlying FGF2-induced OA is poorly characterized. MicroRNAs (miRNAs) maintain cartilage homeostasis. To examine whether FGF2 regulates OA through the modulation of miRNA, we screened potential miRNA molecules that could be regulated through FGF2 using microarray analysis. The results showed that microRNA-105 (miR-105) was significantly downregulated in chondrocytes stimulated with FGF2. Runt-related transcription factor 2 (Runx2), a key transcription factor involved in OA, has been identified as a novel potential target of miR-105. FGF2 suppressed miR-105 expression through the recruitment of the subunit of the nuclear factor kappa B transcription complex p65 to the miR-105 promoter. The knockdown of Runx2 mimicked the effect of miR-105 and abolished the ability of miR-105 to regulate the expression of a disintegrin-like and metalloproteinase with thrombospondin 4 (ADAMTS4), ADAMTS5, ADAMTS7 and ADAMTS12, both of which are responsible for the degradation of collagen 2A1 (COL2A1) and aggrecan (ACAN). miR-105 is also required for FGF2/p65-induced Runx2 activation and ADAMTS expression. Moreover, miR-105 expression was downregulated in OA patients and inversely correlated with the expression of Runx2, ADAMTS7 and ADAMTS12, which were upregulated in OA patients. These data highlight that the FGF2/p65/miR-105/Runx2/ADAMTS axis might play an important role in OA pathogenesis and that miR-105 might be a potential diagnostic target and useful strategy for OA treatment. Runx2 was identified as a novel direct target of miR-105. FGF2 inhibits miR-105 transcription through recruitment of p65 to miR-105 promoter. p65/miR-105 is essential for FGF2-mediated Runx2 and ADAMTS upregulation. miR-105 is downregulated in OA and inversely correlated with Runx2 expression.