[Effect of silencing myocardin gene expression on differentiation of mouse bone mesenchymal stem cells into smooth muscle-like cells induced by PDGF-BB].

Objective: Construction of a small interfering RNA (siRNA) eukaryotic expression vector specific to mouse myocardin gene and study on the role of myocardin-siRNA on differentiation of mouse bone mesenchymal stem cells (MSCs) into smooth muscle-like cells induced by PDGF-BB in vitro.

Methods: Mouse MSCs were isolated from bone marrow and cultured with 50 mg/L PDGF-BB and fetal bovine serum (20%). Specific myocardin-siRNA sequence was cloned into a plasmid pGenesil-1.0 vector, which contained U6 promoter. The recombinant plasmid and control plasmid were transfected into MSCs which had been cultured with PDGF-BB for 6 days beforehand. The expression of myocardin mRNA was detected by RT-PCR 48 hours after the transfection. Immunohistochemistry was used to detect the SM-MHC and to identify the smooth muscle-like cells.

Results: The recombinant plasmids carrying myocardin-siRNA sequences were constructed successfully and the myocardin mRNA was reduced 42.86% by pGen-myo-shRNA in comparing with that of the controls (P<0.01); and the expression of SM-MHC protein was down-regulated (P<0.01).

Conclusion: Subset of mouse MSCs have the potential to differentiate into smooth muscle-like cells, a possible cell source responsible for atherosclerotic plaque formation, and myocardin expression may play an important role during this process.