基质金属蛋白酶及其组织抑制因子在左心室机械辅助减负荷模型中的表达

目的 研究基质金属蛋白酶(MMP)及其组织抑制因子(TIMP)在左心室机械辅助减负荷模型中的表达,探讨左心室减负荷后心肌逆向重构的分子机制.方法 结扎Lewis大鼠冠状动脉左前降支诱导心力衰竭,4周后将14只心力衰竭大鼠随机分为心力衰竭组(n=7)与移植组(n=7).将供体移植组心力衰竭大鼠的心脏及右肺移植到受体正常Lewis大鼠的腹部,通过供体的升主动脉与受体的降主动脉吻合.7只正常Lewis大鼠作为正常组.结扎左前降支4周后心脏超声测量3组大鼠心室直径和心肌梗死范围.移植2周后,称取各组大鼠心脏、左心室质量；显微镜观测左心室心肌细胞直径与心肌纤维化程度；采用实时荧光定量PCR检测MMP-1、MMP-9、TIMP-1的mRNA表达及计算MMP-1mRNA/TIMP-1 mRNA的比值.结果 结扎左前降支4周后,心力衰竭组及移植组舒张末直径(LVEDD)较正常组升高、左心室短轴缩短率(LVFS)较正常组下降,而此两组间LVEDD、LVFS及心肌梗死范围比较差异无统计学意义,两组的心力衰竭严重程度差异也无统计学意义.心力衰竭组心脏、左心室质量和左心室心肌细胞直径大于移植组与正常组；移植组心脏、左心室质量、左心室心肌细胞直径接近正常组.心肌纤维化的程度移植组＞心力衰竭组＞正常组(7.90±2.32)％比(4.20±1.84)％比(1.54±0.31)％,均P＜0.05].心力衰竭组和移植组MMP-1、MMP-9mRNA表达均高于正常组(1.89±0.23、1.32±0.16比0.41±0.01,2.03±0.15、1.50±0.13比0.46+0.01,均P＜0.05),但心力衰竭组与移植组比较差异无统计学意义.心力衰竭组TIMP-1mRNA表达低于正常组与移植组(0.72±0.18比1.21±0.02、1.68±0.21,均P＜0.05)；正常组与移植组比较差异无统计学意义.心力衰竭组MMP-1 mRNA/TIMP-1mRNA比值较正常组及移植组明显增高(2.03±0.15比0.30±0.01、0.81±0.11,均P＜0.05)；正常组与移植组差异则无统计学意义.结论 左心室减负荷后,心肌逆向重塑的过程伴随着心肌细胞MMP及TIMP水平的改变.

Expression of matrix metalloproteinases and tissue inhibitor of metalloproteinases in the model of left ventricular mechanical unloading

Objective To study the expression of matrix metalloproteinases (MMPs) and their tissue inhibitor (TIMPs) in the model of left ventricular mechanical unloading and to explore the molecular mechanism of cardiac reverse remodeling after left ventricular unloading.Methods Lewis rats underwent left anterior descending artery ligation.Four weeks later,14 rats with heart failure were randomly divided into heart failure group (HF,n=7) and heart transplantation group (HT,n=7).Heart and right lung of heart failure donors from HT group were transplanted into normal recipient rats,with ascending aorta of doners anastomosed with descending aorta of recipients.Another 7 normal rats were enrolled as controls.Four weeks after ligation,heart ultrasonography was performed to detect the ventricle diameter and myocardial infarction (MI) field of the three groups.Two weeks later after transplantation,heart mass and left ventricular mass were weighted,myocyte diameter and myocardial fibrosis were evaluated under microscope.Expression of MMP-1,MMP-9,TIMP-1 and proportion of MMP-1/TIMP-1 mRNA were examined by real-time polymerase chain reaction (PCR).Results Four weeks later after ligation,left ventricular end- diastolic diameter (LVEDD) increased but left ventricular fractional shortening (LVFS) decreased in both HF and HT groups when comparing with the normal controls.No statistical significance of LVEDD,LVFS,MI field and heart failure severity was observed between HF and HT groups.Heart mass,left ventricle mass and myocyte diameter were higher in HF group than those of HT group and controls,and those parameters in HT group were almost normal.The severity of myocardial fibrosis was as follows: HT group ＞ HF group ＞ controls (7.90±2.32) ％ vs (4.20± 1.84) ％ vs ( 1.54±0.31 ) ％,all P＜0.05 ].The levels of MMP- 1 and MMP-9 mRNA were significantly higher in HF group and HT group than those in normal group (1.89±0.23,1.32±0.16 vs0.41±0.01; 2.03±0.15,1.50±0.13 vs 0.46±0.01,all P＜0.05),and these parameters of HF group and HT group had no statistical significance.The level of TIMP- 1 mRNA was lower in HF group than that in normal group and HT group (0.72±0.18 vs 1.21 ±0.02,1.68±0.21,all P＜0.05),and the difference was not significant between normal group and HT group.The MMP-1 mRNA/TIMP-1mRNA was higher in HF group as compared to other two groups (2.03±0.15 vs 0.30±0.01,0.81±0.11,all P＜0.05),and the difference was not significant between normal group and HT group.Conclusion After left ventricular unloading,the reverse remodeling of myocardial tissue happens with the changes of MMPs and TIMPs levels in myocytes.