RÉSUMÉ
Objective: To summarize the research progress of the regulatory role of microRNA (miRNA) in osteogenic differentiation of mesenchymal stem cells (MSCs) and its application as a therapeutic target and diagnostic tool in orthopedic diseases. Methods: The recent literature on the regulation of MSCs osteogenic differentiation by miRNAs was extensively reviewed, and its regulatory mechanism and its application as a therapeutic target and diagnostic tool in orthopedic diseases were reviewed. Results: miRNAs are small endogenous non-coding RNAs with a length of 20-22 nucleotides, which play an important role in the osteogenic differentiation of MSCs. Osteogenesis begins with the differentiation of MSCs into mature osteoblasts, and each stage of dynamic homeostasis of bone metabolism is associated with the regulation of different miRNAs. miRNAs are regulated from the post-transcriptional level by mRNAs cleavage, degradation, translational repression, or methylation. In addition, current studies suggest that miRNAs can be used as a new diagnostic tool and therapeutic target for orthopedic diseases. Conclusion: Further study on the regulation mechanism of miRNAs will provide more ideas for finding new therapeutic targets and diagnostic tools for orthopedic disease.
RÉSUMÉ
Objective To study the effect of continuous strain on the proliferation and osteogenic differentiation of rat bone marrow stromal cells(BMSCs) in vitro. Methods Rat BMSCs were obtained from adult female Sprague-Dawley rats (3-month old), and purified by full-blood attachment culture. BMSCs between passage 3—5 were seeded on Flexercell mechanical loading system(10%, 1 Hz), and divided into 1 h group, 6 h group, 12 h group, 24 h group, 48 h group, respectively, according to the time subjected to strain. Effects of continuous strain on the morphology, proliferation and osteogenic differentiation of BMSCs were observed and analyzed. Results (1) Compared with the control group, cells subjected to 10% strain showed the particular orientation. Their alignment elongated mostly in the direction perpendicular to the strain axis in a time-dependent manner. (2)10% continuous strain could significantly decrease the proliferation of BMSCs. (3) Continuous strain could increase mRNA expression of ALP, COLⅠand Runx2 in a time-dependent manner. Compared with the control group, mRNA expression of ALP was increased significantly at 24 h, COLⅠat 24 h and 48 h, and Runx2 at 6 h. mRNA expression of osteocalcin (OC) ascended greatly in the beginning, but went down gradually and was significantly lower than that of control at 48 h（P＜0.05）. (4) Continuous strain could induce an increase in Runx2 protein level. A sharp increase in Runx2 protein was observed at 6 h(P＜0.05) , then Runx2 protein level decreased slowly with its mRNA expression being significantly lower than that of control at 24 h（P＜0.05） Conclusions Continuous strain could induce rat BMSCs to orient in an orderly manner, suppress its proliferation activity, but stimulate the osteoblastic differentiation at the early stage.