Aim: To investigate the dysregulation of microRNAs (miRNAs) during the differentiation of osteoclasts and the precise roles of miR-125a-5p in the differentiation of osteoclasts.
Methods: The cell model of RAW 264.7 osteoclast precursor cell differentiation induced by RANKL plus M-CSF stimulation was established. During the early stage of osteoclast differentiation, miRNA expression profiles were detected using the biochip technique and analyzed by cluster analysis. TargetScan, miRTarBase and miRDB database analysis was applied to find the key target genes of miR-125a-5p. A dual luciferase experiment was conducted to identify the direct target of miR-125a-5p. MiR-125a-5p mimic transfection and anti-miR-125-5p treatment were conducted to verify the role of miR-125q-5p in osteoclast differentiation. The levels of triiodothyronine receptor auxiliary protein (TRAP), matrix metallopeptidase 2 (MMP-2), MMP-9 and cathepsin K were analyzed by qRT-PCR and western blot assay. The expression levels of MMP-2 and MMP-9 were determined using western blotting and immunofluorescence assay. The migration and invasion of RAW 264.7 cells were assessed by wound healing and Transwell invasion assays. The proliferation of RAW 264.7 osteoclast precursor cells was detected using MTT assay.
Results: There were 44 microRNAs differently expressed during the differentiation of RAW 264.7 osteoclast precursor cells into osteoclasts, 35 of which were up-regulated and 9 were down-regulated. By luciferase reporter assay, it was confirmed that the TNF receptor superfamily member 1B gene (TNFRSF1B) was the target gene of miR-125a-5p. Up-regulation of miR-125a-5p inhibited TNFRSF1B protein expression and promoted osteoclast differentiation whereas down-regulation of miR-125a-5p caused completely opposite results.
Conclusions: In conclusion, overexpression of miR-125a-5p suppresses the expression of TNFRSF1B and promotes osteoclast differentiation. These results reveal the crucial role of miR-125a-5p in the differentiation of osteoclasts.
Keywords: Osteoclast; Osteoporosis; TNFRSF1B; miR-125a-5p.