Bone marrow-derived mesenchymal stem cells (BMSCs) have been suggested to possess the capacity to differentiate into different cell lineages. Maintaining a balanced stem cell differentiation program is crucial to the bone microenvironment and bone development. MicroRNAs (miRNAs) have played a critical role in regulating the differentiation of BMSCs into particular lineage. However, the role of miR-149-3p in the adipogenic and osteogenic differentiation of BMSCs has not been extensively discovered. In this study, we aimed to detect the expression levels of miR-149-3p during the differentiation of BMSCs and investigate whether miR-149-3p participated in the lineage choice of BMSCs or not. Compared with mimic-negative control (NC), miR-149-3p mimic decreased the adipogenic differentiation potential of BMSCs and increased the osteogenic differentiation potential. Further analysis revealed that overexpression of miR-149-3p repressed the expression of fat mass and obesity-associated (FTO) gene through binding to the 3' UTR of the FTO mRNA. Also, the role of miR-149-3p mimic in inhibiting adipogenic lineage differentiation and potentiating osteogenic lineage differentiation was mainly through targeting FTO, which also played an important role in regulating body weight and fat mass. In addition, BMSCs treated with miR-149-3p anti-miRNA oligonucleotide (AMO) exhibited higher potential to differentiate into adipocytes and lower tendency to differentiate into osteoblasts compared with BMSCs transfected with NC. In summary, our results detected the effects of miR-149-3p in cell fate specification of BMSCs and revealed that miR-149-3p inhibited the adipogenic differentiation of BMSCs via a miR-149-3p/FTO regulatory axis. This study provided cellular and molecular insights into the observation that miR-149-3p was a prospective candidate gene for BMSC-based bone tissue engineering in treating osteoporosis.

Bone marrow-derived mesenchymal stem cells (BMSCs) have the potential to differentiate into osteoblasts or adipocytes, and the shift between osteogenic and adipogenic differentiation determines bone mass. The aim of this study was to identify whether lncRNAs are involved in the differentiation commitment of BMSCs during osteoporosis. Here, we found ORLNC1, a functionally undefined lncRNA that is highly conserved, which exhibited markedly higher expression levels in BMSCs, bone tissue, and the serum of OVX-induced osteoporotic mice than sham-operated counterparts. Notably, a similar higher abundance of lncRNA-ORLNC1 expression was also observed in the bone tissue of osteoporotic patients. The transgenic mice overexpressing lncRNA-ORLNC1 showed a substantial increase in the osteoporosis-associated bone loss and decline in the osteogenesis of BMSCs. The BMSCs pretreated with lncRNA-ORLNC1-overexpressing lentivirus vector exhibited the suppressed capacity of osteogenic differentiation and oppositely enhanced adipogenic differentiation. We then established that lncRNA-ORLNC1 acted as a competitive endogenous RNA (ceRNA) for miR-296. Moreover, miR-296 was found markedly upregulated during osteoblast differentiation, and it accelerated osteogenic differentiation by targeting Pten. Taken together, our results indicated that the lncRNA-ORLNC1-miR-296-Pten axis may be a critical regulator of the osteoporosis-related switch between osteogenesis and adipogenesis of BMSCs and might represent a plausible therapeutic target for improving osteoporotic bone loss.

Background/Aims: Bone marrow-derived mesenchymal stem cells (BMSCs) have the ability to differentiate into multilineage cells such as osteoblasts, chondrocytes, and cardiomyocytes. Dysfunction of BMSCs in response to pathological stimuli participates in the development of diseases such as osteoporosis. Astragalus polysaccharide (APS) is a major active ingredient of Astragalus membranaceus, a commonly used anti-aging herb in traditional Chinese medicine. The aim of this study was to investigate whether APS protects against iron overload-induced dysfunction of BMSCs and its underlying mechanisms. Methods: BMSCs were exposed to ferric ammonium citrate (FAC) with or without different concentrations of APS. The viability and proliferation of BMSCs were assessed by CCK-8 assay and EdU staining. Cell apoptosis, senescence and pluripotency were examined utilizing TUNEL staining, β-galactosidase staining and qRT-PCR respectively. The reactive oxygen species (ROS) level was assessed in BMSCs with a DCFH-DA probe and MitoSOX Red staining. Results: Firstly, we found that iron overload induced by FAC markedly reduced the viability and proliferation of BMSCs, but treatment with APS at 10, 30 and 100 μg/mL was able to counter the reduction of cell proliferation. Furthermore, exposure to FAC led to apoptosis and senescence in BMSCs, which were partially attenuated by APS. The pluripotent genes Nanog, Sox2 and Oct4 were shown to be downregulated in BMSCs after FAC treatment, however APS inhibited the reduction of Nanog, Sox2 and Oct4 expression. Further study uncovered that APS treatment abrogated the increase of intracellular and mitochondrial ROS level in FAC-treated BMSCs. Conclusion: Treatment of BMSCs with APS to impede mitochondrial ROS accumulation can remarkably inhibit apoptosis, senescence, and the reduction of proliferation and pluripotency of BMSCs caused by FAC-induced iron overload.