| Chapter 1 Establishment and evaluation of chronic ischemic heart failure model in mini pigChronic myocardial ischemia has become the most important cause of heart failure in China. The aim of this study is to create a large animal model of chronic ischemic heart failure. Ameroid constrictor was implanted in the initial segment of LAD in mini pig by open chest surgery. Regional myocardial perfusion was assessed by SPECT. Cardiac function was determined by echocardiography and serum levels of heart failure related inflammatory factor TNF-α, neural-hormonal factors BNP, Ang II and ET-1 were also measured by radioimmunoassay. 4 weeks after ameroid implantation, a fixed perfusion defect was detected in LAD dependent area in ischemic pig. Also, the overall cardiac systolic and diastolic function, regional myocardial motion and thickness were significantly decreased compared with the control animal, with significant increase of the serum levels of the above heart failure related biomarkers. These results indicated that implantation of ameroid constrictor in the initial segment of LAD is a dependable way to create animal model of chronic ischemic heart failure. Chapter 2 Improved cardiac function after SERCA2a gene delivery in mini pig model of chronic ischemic heart failureSERCA2a gene delivery has been reported to be beneficial to the cardiac function in a variety of heart failure animal models, but its effects on chronic ischemic heart failure are still unknown. The aim of this study was to investigate whether SERCA2a gene delivery could improve the cardiac function in this heart failure type. Intramyocardial injection was performed to deliver the recombinant adeno-associated viral vector containing either EGFP or SERCA2a in chronic ischemic heart failure pigs. Effects of SERCA2a gene delivery on cardiac function were assessed by echocardiography and hemodynamic measurement. Changes of regional myocardial perfusion were determined by SPECT and changes of serum levels of heart failure related biomarkers were measured by radioimmunoassay. rAAV1-SERCA2a effectively restored the protein level and activity of SERCA2a in ischemic myocardium and significantly improved overall cardiac function 8 weeks after gene delivery, with significant decrease of serum heart failure related biomarkers. However, no improvement of regional myocardial perfusion was detected 8 weeks after SERCA2a gene delivery. These results demonstrated that intramyocardial rAAV1-SERCA2a gene delivery is an effective way to improve cardiac function of chronic ischemic heart failure in mini pig, indicating the potential therapeutic role of SERCA2a gene delivery in chronic ischemia induced heart failure. Chapter 3 Attenuation of ER stress related myocardial apoptosis by SERCA2a gene delivery in a mini pig model chronic ischemic heart failureMyocardial apoptosis has been reported to play an important role in the pathogenesis of chronic ischemic heart failure and ER stress-apoptosis signaling pathway is a newly defined mechanism of cellular apoptosis. The aim of this study is to investigate the effects of SERCA2a gene delivery in ischemic myocardial apoptosis and ER stress associated apoptosis pathway. TUNEL staining was used to measure the apoptosis of ischemic myocardium of animals in section 2. Immunohistochemistry and Western Blot were performed to detect the activation of the components of UPR pathway ATF6, IRE1 and PERK, and ER stress related apoptotic proteins CHOP, caspase-12 and JNKs. Enhanced myocardial apoptosis and activation of UPR pathway signaling proteins were detected in EGFP transduced animals compared to control, with significant increase of ER stress related apoptotic proteins, indicating ER stress related apoptosis was enhanced in the myocardium of chronic ischemic heart failure pigs. However, restoration of SERCA2a expression by gene transfer significantly attenuated the apoptosis of ischemic myocardium and reversed the activation of UPR pathway and ER stress related apoptotic proteins. These results demonstrated that the beneficial effects of SERCA2a gene delivery to chronic ischemic heart failure may be related to the attenuation of ER stress associated myocardial apoptosis. |
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