BACKGROUND: Bone marrow mesenchymal stem cells (BMSCs) are widely used in the field of tissue engineering because of their multi-directional differentiation potential. Micro RNAs play an important role in promoting osteogenic differentiation of BMSCs.OBJECTIVE: To investigate the effect of miR-218 and miR-26a on the osteogenic differentiation of rat BMSCs, and to provide reference for the study on osteogenic differentiation of BMSCs and the clinical application. METHODS: The bone marrow of the femur of Wistar rats was extracted and the BMSCs were isolated and cultured to the 3rd generation. MiR-218, miR-26a and polyethyleneimine (PEI) were mixed in a specific ratio to form a miRNA/PEI complex. Meanwhile, a negative control group was established.RESULTS AND CONCLUSION: (1) Rat BMSCs grew well. (2) The optimal concentration of miRNA mimics was 50 nmol/L by MTT method. (3) The expression of alkaline phosphatase and collagen type I mRNA was significantly increased (P < 0.05). (4) Alkaline phosphatase staining showed that compared with the blank control group and the negative control group, the cytoplasm showed obvious coloring. (5) There were a lot of mineralized nodules shown by alizarin red staining. Therefore, miR-218/PEI complex, miR-26a/PEI complex and miR-218+miR-26a/PEI co-transfection complex could promote the osteogenic differentiation of BMSCs. Under the same conditions, the osteogenesis of miR-26a was slightly better than that of miR-218.

Objective:To transfect the non-viral vector polyethylenimine (PEI)mediated miR-2861 mimic into the MC3T3-E1 cell line,and to explore the transfection efficiency of PEI/miR-2861 complex and its effects on the proliferation and osteogenesis differentiation in pre-osteoblasts. Methods:The proper amount of PEI was blended with miR-2861 mimic and negative control (NC)separately in a ratio of N∶P=10∶1,and they were divided into experiment group and NC group. The NC/PEI complex acted as the NC group was used to eliminate the interference of osteogenesis from the addition of double-stranded RNA mimic.MTT assay was used to determine the optimal concentration of PEI/miR-2861 mimic complex.The fluorescence imaging technique and bulge-loop RT-PCR were used to detect the transfection efficiency and mRNA expression of miRNA-2861 in the cells with different concentrations (10,30, 50,and 100 nmol · L-1 ), separately.The osteogenesis ability of MC3T3 cells was identified with RT-PCR and Alizarin red staining with the selected concentration of PEI/miR-2861 by transient transfection.Results:Compared with blank control group,the proliferation rates of MC3T3 cells in 100 nmol·L-1 PEI/miR-2861 group was decreased significantly at 72 h (P < 0. 05 ). With the increasing of transfected concentration the transfection efficiency of miRNA/PEI complex was increased gradually.The results of Alizarin red staining and quantitative analysis showed that calcium deposits were more and bigger in experiment group after induced for 21 d,while both in blank control group and NC group they were less.Conclusion:The miRNA-2861 mimic can be effectively transfected into the MC3T3-E1 cell line and expresses with a high level,which is mediated by PEI as the gene vector.miR-2861 mimic has a certain ability of promoting osteogenesis differentiation of MC3T3-E1 cells.