红细胞生成素对大鼠心肌梗死后间质重塑及MMPs、TIMP-4表达的影响

Effects of erythropoietin on matrix remodeling and the expressions of MMPs and TIMP-4 after myocardial infarction in rats

目的探讨重组人红细胞生成素(rhEPO)对心肌梗死大鼠心肌细胞间质重构和基质金属蛋白酶(MMPS)及其抑制物(TIMP-4)表达的影响。方法80只SD大鼠随机分为心梗组(MI)、心梗药物组(MIE)、假手术组(SH)、假手术药物组(SHE)。术后1周及6周分别测量各组大鼠血细胞比容,毛细血管密度,心肌梗死面积,Ⅰ、Ⅲ型胶原容积分数及其比值,免疫组化测定MMP-2、MMP-9及TIMP-4蛋白在大鼠左室心肌中的表达,并行超声心动图测定左室功能。结果术后1周时免疫组化示MI、MIE组MMP-2、MMP-9表达较SH、SHE组增高(P<0.05),MMP-2、MMP-9表达较MI组降低(P<0.05),MI组TIMP-4表达较SH、SHE降低(P<0.05),MIE组TIMP-4表达较MI组增高(P<0.05),MI组和MIE组梗死交界区Ⅰ、Ⅲ型胶原容积分数无明显差异(P>0.05)。6周后大鼠超声心动图示MI和MIE组左室舒张末期内径(LVDd)、左室收缩末期内径(LVDs)、左室舒张末期容积(LVEDV)、左室收缩末期容积(LVESV)均高于SH和SHE组,而左室射血分数(LVEF)和左室短轴缩短平(LVFS)均低于SH组和SHE组(P<0.05),MI组LVDd、LVDs、LVEDV、LVESV高于MIE组,而LVEF、LVFS低于MIE组(P<0.05)。术后6周MIE组梗死交界区毛细血管数目较MI组明显增多(P<0.05),而心肌梗死面积较MI组明显减少(P<0.05);MIE组心肌梗死交界区Ⅰ、Ⅲ型胶原容积分数及其比值较MI组明显降低(P<0.05),以I型胶原升高为主。结论心肌梗死后大鼠左室心功能降低,心肌内MMP-2、MMP-9蛋白表达升高,TIMP-4蛋白表达降低,心肌间质Ⅰ、Ⅲ型胶原含量增加,共同参与了心室重塑。rhEPO早期干预可改善心肌重塑,其可能机制是通过升高TIMP-4来抑制MMP-2、MMP-9蛋白表达,降低胶原含量,从而减少间质纤维化。

Objective To investigate the effects of erythropoietin （EPO） on extracellular matrix remodeling and the expressions of matrix metalloproteinase （MMPs） and tissue inhibitor of metalloproteinase-4 （TIMP-4） after myocardial infarction in rats. Methods Eighty male SD rats were randomly divided into four groups： sham operation（SH） group, sham operation and drug（SHE） group, myocardial infarction（MI） group, and myocardial inferct and erythropoietin（MIE） group. Myocardial infarction in MI group and MIE group was reproduced by ligation of a branch of left anterior descending coronary artery. Hematocrit, echocardiography, capillary density, infarct area, fibrosis and collagen volume fraction were tested, and MMP-2, MMP-9 and TIMP-4 were measured by immunohistochemistry at 1- week and 6-week after myocardial infraction. Results One week after myocardial infraction, the protein expressions of MMP-2 and MMP- 9 in MI and MIE groups were significantly higher than that in SH and SHE group （P〈0. 01）, and the protein expressions of MMP-2 and MMP-9 in MIE group were lower than that in MI group （P〈0. 01）. The protein expression of TIMP-4 in MI group was lower than that in SH, SHE and MIE groups （P〈0.01）. There was no difference in the collagen volume fraction in junctional zone between MI group and MIE group （P〈0.05）. Six weeks after myocardial infraction, echocardiography revealed that the left ventricular end-diastolic dimension （LVDd）, left ventricular end-systolic dimension （LVDs）, left ventricular end-diastolic volume （LVEDV） and left ventricular end-systolic volume （LVESV） were significantly increased, and left ventricular ejection fraction （LVEF） and left ventricular fractional shortening （LVFS） were significantly decreased in MI and MIE groups compared with those in SH and SHE groups （P〈0. 01）. LVDd, LVDs, LV- EDV and LVESV were significantly higher, while LVEF and LVFS were significantly lower in MI group compared with those in MIE group （P〈20. 05）. The infarct size and collagen volume fraction were significantly lower, but the capillary density was significantly higher in MIE group than those in MI group （P〈0. 01）. Conclusions Increased expressions of MMP-2, MMP-9, collagen Iand collagen llI, decreased expression of TIMP-4 and degraded LV function may play an important role in cardiac remodeling following myocardial infarction （MI）. rhEPO can prevent left ventricular remodeling and improve LV function, which is associated with up-regulation of TIMP-4 expression and inhibition of the activity of MMP-2 and MMP-9.