Recently, a cohort of miRNAs, including miR-31, was reported to be downregulated during osteogenic induction by miR microarray analysis. It remains unclear how changes in miR-31 expression collaborate with bone transcription factors to activate the biological pathways that regulate the differentiation of bone mesenchymal stem cells (BMSCs). Here the effects of miR-31, Runx2 , and Satb2 on the osteogenic differentiation of BMSCs were investigated using mimics and inhibitors of miR-31, small interfering RNA for knockdown of Runx2 and plasmids for overexpression of Runx2 . Our results showed that miR-31 expression decreased progressively in BMSC cultures during differentiation. Inhibition of miR-31 dramatically increased the alkaline phosphatase activity and mineralization in BMSC cultures. Additionally, miR-31 diminished the levels of the Satb2 protein without significantly affecting Satb2 mRNA levels, and Runx2 directly repressed miR-31 expression. Overexpression of miR-31 significantly reduced expression of the osteogenic transcription factors OPN, BSP, OSX, and OCN, but not Runx2. Furthermore, the high expression of miR-31 in BMSCs cultured in the proliferation medium repressed Satb2 protein levels, which may contribute to the maintenance of BMSCs in an undifferentiated state. In conclusion, our results suggest that a Runx2 , Satb2 , and miR-31 regulatory mechanism may play an important role in inducing BMSC osteogenic differentiation. The results of this study provide us with a better understanding of the molecular mechanisms that govern the BMSC fate.

MicroRNAs (miRNAs) are endogenous small noncoding ~22-nt RNAs, which have been reported to play a crucial role in maintaining bone development and metabolism. Osteogenesis originates from mesenchymal stem cells (MSCs) differentiating into mature osteoblasts and each period of bone formation is inseparable from the delicate regulation of various miRNAs. Of note, apprehending the sophisticated circuit between miRNAs and osteogenic homeostasis is of great value for artificial skeletal regeneration for severe bone defects. In this review, we highlight how different miRNAs interact with diverse osteo-related genes and endeavor to sketch the contours of potential manipulations of miRNA-modulated bone repair.

The repair of critical-sized defects (CSDs) is a significant challenge in bone tissue engineering. Combining the use of progenitor cells with gene therapy represents a promising approach for bone regeneration. MicroRNAs play important roles in most gene regulatory networks, regulate the endogenous expression of multiple growth factors and simultaneously modulate stem cell differentiation. Our previous study showed that knocking down miR-31 promotes the osteogenesis of bone marrow stromal stem cells (BMSCs). To investigate the therapeutic potential of cells engineered to express anti-miR-31 for CSD repair, lentiviral vectors encoding negative control, miR-31 precursor and anti-sense sequences were constructed and transduced into osteo-inductive BMSCs. The expression of osteogenic-specific genes, alkaline phosphatase activity and Alizarin Red S staining were investigated to evaluate the effects of miR-31 on the cell fate of BMSCs over a 3-week period. In addition, miR-31-modified BMSCs seeded on poly(glycerol sebacate) (PGS) scaffolds were used to repair 8 mm critical-sized calvarial defects in rats. The results showed that miR-31 suppression significantly increased the expression of osteogenic-specific genes in vitro at the mRNA and protein levels, and that robust new bone formation with high local bone mineral density was observed in the anti-miR groups in vivo. Moreover, the PGS scaffolds carrying anti-miR-31-expressing BMSCs exhibited good biocompatibility and a high regeneration rate (~60%) within in vivo bone defects. Our results suggest that miR-31 gene delivery affects the potential of BMSCs for osteogenic differentiation and bone regeneration and that PGS is a potential substrate for genetically modified, tissue-engineered bone in the repair of large bone defects.

Detachment is the initial and critical step for cancer metastasis. Only the cells that survive from detachment can develop metastases. Following the disruption of cell–extracellular matrix (ECM) interactions, cells are exposed to a totally different chemical and mechanical environment. During which, cells inevitably suffer from multiple stresses, including loss of growth stimuli from ECM, altered mechanical force, cytoskeletal reorganization, reduced nutrient uptake, and increased reactive oxygen species generation. Here we review the impact of these stresses on the anchorage-independent survival and the underlying molecular signaling pathways. Furthermore, its implications in cancer metastasis and treatment are also discussed.