MiR-16 Enhances Bone Marrow Derived Mesenchymal Stem Cells Differentiation Towards Cardiac Phenotypes In Cardiac Niche In Vitro.

Objective To induce human bone marrow-derived mesenchymal stem cells (hBM-MSCs) to differentiate into cardiac phenotypic cells (Cps) by coculturing hBM-MSCs with neonatal Sprague-Dawley(SD) rat ventricular myocytes(NRVM) indirectly and detect miRNAs profile between hBM-MSCs and Cps. Then to find out functional miRNAs which can induce hBM-MSCs to differentiate into Cps and study molecular mechanisms of differentiation induced by functional miRNAs.Methods (1) Human bone marrow was cultured with culture medium in flask directly in order to isolate adherent cells. The proliferation character and shape of primary or passage cells, the phenotype of cells analyzed using a flow cytometer and the ability of osteoblast differentiation were used to confirm whether the cells were hBM-MSCs. (2) hBM-MSCs were induced to differentiate into Cps by coculturing hBM-MSCs with NRVM indirectly in vitro(cardiac niche in vitro). (3) miRNA array technology was used to detect the miRNA profiles between hBM-MSCs and Cps and screen those upregulated miRNAs (folds>2) in Cps. (4) qRT-PCR technology was used to detect upregulated miRNAs expression in order to test the results of miRNA array.Results (1) Cells isolated from human bone marrow were fusiform shape and had large nuclear-cytoplasmic ratio. The results of flow cytometer demonstrated that CD29/CD44 expression in hBM-MSCs was very high and CD34/CD4 expression was very low. (2) hBM-MSCs could be induced to differentiate into Cps in cardiac niche in vitro(indirect coculture method in vitro). Because some genes such as GATA4, Nkx2.5 could be detected in Cps. (3) It was demonstrated by miRNA array technology that 5 miRNAs(hsa-miR-16,hsa-let-7e,hsa-miR-138,hsa-let-7a,hsa-miR-524) were upregulated in Cps compared to that of hBM-MSCs (folds>2). (4) Results of qRT-PCR technology to detect the expression of 4 upregulated miRNAs (hsa-miR-16,hsa-let-7e,hsa-miR-138,hsa-miR-524) confirmed the results of miRNA array. (5) It is demonstrated by qRT-PCR,western-bloting,cell cycle analysis and so on that miR-16 could induce hBM-MSCs in cardiac niche in vitro to differentiate into Cps. Overexpressing miR-16 in hBM-MSCs can promote them in cardiac niche in vitro to express high GATA4, Nkx2.5, MEF2C and cTnI gene. (6) Overexpressing miR-16 in hBM-MSCs could downregulate the expression of CCND1, CCND 2 and CDK6 gene and arrest the stem cell cycle in G1-phase which might involve in promoting hBM-MSCs in cardiac inche to differentiate into CPs.Conclusion (1) Cells isolated from human bone marrow were pure hBM-MSCs. (2) Cardiac inche in vitro(indirect coculturing method) could induce hBM-MSCs to differentiate into Cps. There are different miRNAs profiles between hBM-MSCs and Cps. Perhaps some miRNAs upregulated in Cps played an important part in hBM-MSCs differentiation. (3) Overexpressing miR-16 in hBM-MSCs could also promote hBM-MSCs in Cardiac inche in vitro to differentiate into Cps through downregulating CDK6 mRNA and arresting hBM-MSCs cell cycle in G1-phase.