Adipocyte Differentiation of Immortalized Human Bone Marrow-derived Stromal Cells is Modulated by microRNA-155, microRNA-221 and microRNA-222

Human bone marrow mesenchymal stromal cells are capable of limited self-renewal and multi-lineage differentiation in vitro. Several studies have demonstrated that microRNAs, post-transcriptional modifiers of protein expression, play crucial roles in the regulation of these complex processes. To gain knowledge regarding the role of microRNAs in human adipocyte regulation, we examined the microRNA expression profile of the immortalized human bone marrow-derived stromal cell line hMSC-Tert20. We identified 12 microRNAs that were differentially expressed during adipogenesis, of which several have previously been shown to play important roles in adipocyte biology. The expression of miR-155, miR-221 and miR-222 decreased during the adipogenic program, suggesting that they act as negative regulators of differentiation. Interestingly, adenovirus-mediated expression of either miR-155 alone or miR-221 plus miR-222 significantly inhibited adipogenesis and repressed induction of the master regulators C/EBP α and PPARgamma Our study provides the first experimental evidence that miR-155, miR-221 and miR-222 function in human adipocyte differentiation. The telomerase immortalized human bone marrow-derived stromal cell line hMSC-Tert20 was differentiated towards adipocytes, and total RNA was harvested at various time points (0, 8, 24, 32, 48 and 72 hours, and 7, 14 and 21 days). All hybridizations, except for 0h, 8h and 32h, were performed twice. The expression of each miRNA at a given time point was calculated as a ratio relative to its level on day 0. No dye swaps.