心脏再同步治疗通过调控线粒体钙单向转运体表达改善心功能的机制研究

Mechanisms of cardiac resynchronization therapy ameliorating failing heart function via regulating mi-tochondrial calcium uniporter expression

目的：探讨心脏再同步治疗（ CRT）通过调控线粒体基质钙稳态治疗心力衰竭（心衰）的可能机制。方法通过左束支消融后右心室快速起搏4周建立心衰犬模型（ n＝6），联合心外膜电极刺激4周建立CRT治疗组（ n＝6），同时设立正常对照组（ n＝3）。在观察终点测量心功能及心肌同步性超声心动图指标；电镜下观察心肌组织线粒体超微结构改变；检测线粒体钙离子浓度变化；基因芯片筛查及多聚酶链反应（ PCR）验证线粒体钙通道相关基因表达改变。体外牵张试验进一步验证相关基因的表达情况。结果与心衰组犬相比，CRT 4周后心脏收缩同步性改善、射血分数提高。电镜观察发现心衰犬心肌线粒体肿胀、线粒体嵴断裂，正常线粒体数目减少，CRT则部分恢复了上述病理改变。基因芯片筛查发现心衰犬线粒体钙单向转运体（ mitochondrial calcium uniporter ，MCU）表达增加，同时线粒体钙离子浓度增加，而CRT可下调上述改变；提示CRT可能通过调控MCU表达调节线粒体钙稳态。同时心衰犬心肌组织中线粒体能量代谢相关酶类丙酮酸脱氢酶激酶4（ pyruvate dehydrogenase kinase 4，PDK4）的表达亦受到CRT调控而恢复正常水平。牵张试验的结果与上述结果一致。结论 CRT可能通过调节心衰心肌组织中MCU的表达，恢复线粒体基质钙稳态，影响线粒体能量代谢相关酶类的功能恢复，从而对心衰发挥治疗作用。

Objective To investigate the mechanisms of cardiac resynchronization therapy （ CRT） in improving failing heart function via modulating mitochondrial calcium homeostasis .Methods Beagles Heart failure model were established followed by CRT for 4 weeks.Left ventricular ejection fraction （LVEF）,left ven-tricular internal diameter ,septal to posterior wall motion delay （ SPWMD） was measured using ultrasonic cardi-ogram.Mitochondrial ultrastructures were observed under electron microscope followed by mitochondrial calcium assays.Microarray-assay and real time polymerase chain reaction （ PCR） were used to target the differentially expressed genes.Results CRT restored LVEF and the heart synchronization （ P〈0.05 ） .Ultrastructure changes of mitochondria swelling , crista broken and decreasing were ameliorated post CRT .Calcium assay demonstrated a calcium concentration rise in HF dogs （ P=0.004） and restoration after CRT （ P=0.04） .Mi-croarray assay targeted mitochondrial calcium uniporter （ MCU） and pyruvate dehydrogenase kinase 4（ PDK4） , which were regulated post CRT respectively .Conclusions CRT restored mitochondrial calcium homeostasis via regulating MCU expression and regulated PDK 4 activity so that it improved the failing heart function .