Abstract: Objective To evaluate the effects of mitofusin 2(mfn2) gene silencing by specific small interference RNA(siRNA) on vascular smooth muscle cells(VSMCs) derived foam cells formation inhibited by testosterone. Methods The three double-strand siRNAs targeting mfn2 gene were designed and synthesized, then transfected into rat VSMCs by positive ion liposome Lipofectamine 2000. The mRNA and protein expression levels of mfn2 in VSMCs were detected by real-time fluorescent quantitative PCR and Western blotting, respectively. Then, VSMCs were divided into control group, testosterone group, testosterone+control-siRNA group, and testosterone+mfn2-siRNA group. Effects of testosterone with or without siRNA on the quantity of intracellular lipid of the VSMCs were detected with Oil red O staining and enzymatic fluorometric method. The expression of the Mfn2 was analyzed with Western blotting. We also examined the effect of testosterone with or without siRNA on the cholesterol transport related protein(CD36 and ABCA1). Results After mfn2-siRNAs were successfully transfected into rat VSMCs, compared to the non-targeting siRNA，the mfn2 mRNA and protein expression levels in VSMCs were significantly decreased at 12, 24, 36, 48 h(P<0.05). Compared with the control group, lipid deposition was reduced significantly in the testosterone with or without control-siRNA groups(both P<0.05). Testosterone markedly increased the expression of Mfn2 and ABCA1(both P<0.05), while suppressed the expression of CD36(P<0.05) in ox-LDL stimulated VSMCs. Moreover, such suppressive effects of testosterone on foam cells formation could partly been reversed by the mfn2-siRNA(P＜0.05), suggesting an involvement of mfn2 in the mechanism. Conclusions Testosterone inhibited the formation of VSMCs derived foam cells induced by ox-LDL partly via the Mfn2 dependent manner by down-regulation of CD36 and up-regulation of ABCA1 expression.

Key words: small interfering RNA, mitofusin 2, testosterone, vascular smooth muscle cells, foam cells