过氧化物酶体增殖物激活受体γ促进外源性骨髓间充质干细胞表达Cx43的作用及机制

Peroxisome proliferator-activated receptor gamma promotes exogenous mesenchymal stem cells to express connexin 43: its role and mechanism

背景:过氧化物酶体增殖物激活受体γ激动剂能促进外源性骨髓间充质干细胞的生存和向心肌细胞分化及改善心功能。研究欲进一步验证吡格列酮能否促进内源性骨髓间充质干细胞向心肌细胞的分化及改善心功能的相关机制。目的:比较过氧化物酶体增殖物激活受体γ激动剂吡格列酮联合骨髓间充质干细胞移植治疗、单纯吡格列酮治疗及磷酸缓冲液治疗疗效的差异及其相关机制。方法:开胸结扎30只SD大鼠左前降支冠状动脉并随机分为3组:骨髓间充质干细胞+吡格列酮组、吡格列酮组、磷酸缓冲液组。造模后2周骨髓间充质干细胞+吡格列酮组在局部梗死心肌内注射PKH26标记的由PBS悬浮的骨髓间充质干细胞,吡格列酮组和磷酸缓冲液组在梗死心肌内注射PBS,骨髓间充质干细胞+吡格列酮组和吡格列酮组在注射骨髓间充质干细胞后予以吡格列酮3 mg/(kg·d)连续灌胃2周。治疗2周后检测心功能,摘取心脏检测左心室心肌组织不同区域过氧化物酶体增殖物激活受体γ、缝隙连接蛋白43和TGF-β1/SMAD通路相关因子的表达变化。结果与结论:(1)3组大鼠在干预开始时心功能参数无明显差异性。干预2周后,骨髓间充质干细胞+吡格列酮联合治疗组左室舒张末径、左室收缩末径明显减小,左室射血分数明显增高;(2)骨髓间充质干细胞+吡格列酮组和吡格列酮组左心室心肌组织不同区域过氧化物酶体增殖物激活受体γ表达量显著增加;(3)骨髓间充质干细胞+吡格列酮组在梗死区和梗死边缘区Cx43表达较吡格列酮组和磷酸缓冲液组显著增高,TGF-β1、SMAD2、SMAD3表达明显下降,吡格列酮组与磷酸缓冲液组在上述指标方面表达差异无显著性意义;(4)结果表明,过氧化物酶体增殖物激活受体γ激动剂吡格列酮并不能刺激内源性骨髓间充质干细胞的增殖分化并改进心功能,吡格列酮联合外源性骨髓间充质干细胞能改善心功能,其机制可能与过氧化物酶体增殖物激活受体γ抑制TGF-β1/SMAD通路进而促进外源性骨髓间充质干细胞表达Cx43有关。

BACKGROUND： Piglitazone, a peroxisome proliferator-activated receptor γ（PPAR-γ） agonist, has been demonstrated to promote survival and cardiac differentiation of exogenous bone marrow mesenchymal stem cells to improve cardiac function. In this study, we attempted to investigate whether pioglitazone could induce cardiac differentiation of endogenous bone marrow mesenchymal stem cells and improve cardiac function, and meanwhile, probed into the relevant mechanisms. OBJECTIVE： To compare the therapeutic efficacy of pioglitazone combined with bone marrow mesenchymal stem cell transplantation, pioglitazone alone and phosphate buffer solution（PBS） and to investigate the relevant mechanisms. METHODS： Thirty Sprague-Dawley rats with myocardial infarction induced by ligation of the left anterior descending coronary artery were randomized into combined group（combination of bone marrow mesenchymal stem cells and pioglitazone）, pioglitazone group and PBS group. Two weeks later, PKH26-labeled bone marrow mesenchymal stem cells in PBS or PBS alone were injected into the local infarct zone in the combined group and the other two groups, respectively. Pioglitazone（3 mg/kg/d） was given by the oral gavage in the combined and pioglitazone groups for continuous 2 weeks after cells transplantation. At 2 weeks after treatment, cardiac functions were evaluated. In addition, expressions of PPAR-γ, connexin 43 and relative factors in transforming growth factor-β1/SMAD signaling pathway were examined in different areas of the left ventricle from each harvested heart. RESULTS AND CONCLUSION： There were no differences in the baseline parameters of cardiac function between the two groups. Two weeks after treatment, left ventricular end-diastolic diameter, left ventricular end-systolic diameter and left ventricular ejection fraction were significantly improved in the combined group compared with the other two groups; the expression of PPAR-γ was significantly increased in different zones of the left ventricle in the combined and pioglitazone groups. In the combined group, there was a significantly higher expression of connexin 43, and the levels of transforming growth factor-β1, SMAD2 and SMAD3 were obviously attenuated in the infarct and marginal zones. However, no differenceswere found in the above determinants between the pioglitazone and PBS groups. To conclude, pioglitazone cannot induce the differentiation and proliferation of endogenous bone marrow mesenchymal stem cells, but pioglitazone combined with exogenous bone marrow mesenchymal stem cells can improve cardiac function post myocardial infarction. In this process, PPAR-γ might promote the connexin 43 expression in exogenous bone marrow mesenchymal stem cells via the blockade of transforming growth factor-β1/SMAD signaling pathway.