In this study we set out to investigate the changes in the microRNA (miRNA) expression that occur during the osteogenic differentiation of bone marrow-derived MSCs. To this purpose, we analyzed the miRNA expression profile of MSCs deriving from 3 donors during the differentiation and mineralization processes by microarray. 29 miRNAs were significantly and consistently modulated during the osteogenic differentiation and 5 during the mineralization process. Interestingly, most of the differentially expressed miRNAs have been reported to be implicated in stemness maintenance, differentiation and/or oncogenesis. Subsequently, we focused our attention on the regulation of Osterix by miRNAs and demonstrated that one of the miRNAs differentially modulated during osteogenic differentiation, miR-31, controls Osterix expression through association to the 3¡ä untranslated region of this transcription factor. By analyzing miR-31 and Osterix expression levels we found an inverse miRNA-target expression trend during osteogenic differentiation and in osteosarcoma cell lines. Moreover, the inhibition of the microRNA activity led to an increase in the endogenous expression of Osterix.
Our results define a miRNA signature characterizing the osteogenic differentiation of MSCs and provide evidence for the involvement of miR-31 in the regulation of the bone-specific transcription factor Osterix.