中文摘要：

目的探讨通过超声微泡介导丙二酰辅酶A脱羧酶（MCD）-microRNA干扰质粒靶向抑制心肌MCD对心肌梗死大鼠心功能的影响及其可能机制。方法将MCD表达质粒与4条待筛选的MCD-microRNA干扰质粒分别共转染至HEK293细胞中,通过实时荧光定量PCR检测MCD mRNA表达水平,筛选出抑制率最高的干扰序列进行动物实验。通过结扎大鼠左冠状动脉前降支构建心肌梗死模型,将28只心肌梗死大鼠随机分为心肌梗死＋生理盐水组及3个心肌梗死干预组（心肌梗死＋质粒组,心肌梗死＋超声＋质粒组,心肌梗死＋超声＋微泡＋质粒组）,每组7只;另取7只大鼠（假手术＋生理盐水）作为假手术组。将筛选出的MCD-microRNA干扰质粒与脂质微泡混合,通过超声介导转染入心肌梗死后4周的大鼠中,每4d转染1次,连续转染28d后,通过超声心动图观察左室射血分数（LVEF）、短轴缩短分数（FS）和左室舒张末期内径（LVIDd）的变化,采用高效液相色谱法测量丙二酰辅酶A的含量,酶联免疫法检测心肌乳酸的变化。结果根据实时荧光定量PCR结果选择出1条对MCD mRNA表达抑制率最高的干扰质粒,其转染抑制率约为82%。在动物实验中,心肌梗死＋超声＋微泡＋质粒组的LVEF、FS均高于其他心肌梗死干预组（P〈0.05）,但明显低于假手术组（P〈0.05）;乳酸含量明显低于其他心肌梗死干预组（P〈0.05）,但高于假手术组（P〈0.05）;丙二酰辅酶A含量明显高于其他各组（P〈0.05）;LVIDd在各心肌梗死干预组之间无显著差异（P〉0.05）,但明显低于假手术组（P〈0.05）。结论超声微泡介导MCD-microRNA干扰质粒靶向转染入梗死后心肌,可增加丙二酰辅酶A含量,降低乳酸含量,虽不能抑制心室扩张,但可明显延缓心功能的恶化。

英文摘要：

Objective To evaluate the effect of the targeted inhibition of myocardial malonyl-CoA decarboxylase（MCD） by ultrasound microbubble mediated MCD-microRNA interference plasmids on cardiac function in rats with myocardial infarction （MI） and its possible mechanism.Methods The MCD expression plasmid and four MCD-microRNA interference plasmids to be screened were co-transfected into HEK293 cells.The levels of MCD mRNA were determined by real-time fluorescence quantitative PCR,and interference sequence with the highest rate of suppression was selected.MI model was reproduced by ligating the left anterior descending coronary artery.The 28 rats with myocardial infarction were randomly assigned into four experimental groups： MI ＋ saline（group 1）,MI ＋ plasmid（group 2）,MI ＋ ultrasound ＋ plasmid（group 3）,MI ＋ ultrasound ＋ microbubble ＋ plasmid （group 4）, 7 rats in each group. An alternative group of sham-operated ＋ saline served as control. The mixture of the selected interference plasmids and lipid microbubbles were co-transfected once every four days into rats with MI for 4 weeks mediated by ultrasound.After transfection for 28 days,the changes in left ventricular ejection fraction（LVEF）,short axis fractional shortening （FS）,left ventricular end-diastolic diameter（LVIDd） were examined by echocardiography,and MCD and lactic acid levels were determined by high-performance liquid chromatography method and enzyme-linked immunosorbent assay respectively.Results One MCD-microRNA interference plasmid with the highest inhibition rate,which was 82%,was selected according to the result of real-time fluorescence quantitative PCR.In animal experiments,the levels of LVEF and FS in the group 4 were both higher than those in other MI intervention groups （P0.05）, but significantly lower than those in the control group （P0.05）. The lactic acid level was lower in group 4 than in other MI-intervention groups （all P 0.05）, but significantly higher than that in the control group