Angiogenesis, Cardiomyocyte Proliferation and Anti-Fibrotic Effects Underlie Structural Preservation Post-Infarction by Intramyocardially-Injected Cardiospheres

ObjectiveWe sought to understand the cellular and tissue-level changes underlying the attenuation of adverse remodeling by cardiosphere transplantation in acute myocardial infarction (MI).BackgroundCardiospheres (CSps) are heart-derived multicellular clusters rich in stemness and capable of multilineage differentiation. Post-MI CSp transplantation improves left ventricular (LV) function and attenuates remodeling in both small and large animal studies. However, the mechanisms of benefit have not yet been fully elucidated.MethodsFour groups were studied: 1) “Sham” (Wistar Kyoto rats with thoracotomy and ligature without infarction); 2) “MI” (proximal LAD ligation with peri-infarct injection of vehicle); 3) “MI+CSp” (MI with cardiospheres injected in the peri-infarct area); 4) “Small MI” (mid-LAD ligation only).ResultsIn vivo 1 week after CSp transplantation, LV functional improvement was associated with an increase in cardiomyocyte proliferation. By 3 weeks, microvessel formation was enhanced, while cardiomyocyte hypertrophy and regional fibrosis were attenuated. Collagen deposition was reduced, collagen degradation was enhanced, and MMPs were upregulated. The beneficial effects of CSp transplantation were not observed in the Small MI group, indicating that the effects are not solely due to CSp-induced cardioprotection. In vitro, CSp-conditioned media reduced collagen production in coculture with fibroblasts and triggered neoangiogenesis in an ex vivo aortic ring assay.ConclusionCardiospheres enhance cardiomyocyte proliferation and angiogenesis, and attenuate hypertrophy and fibrosis, in the ischemic myocardium. These synergistic effects underlie the attenuation of adverse remodeling by cardiospheres.研究目的：本研究旨在明确急性心肌梗死（acute myocardial infarction, MI）模型中，心脏球（cardiosphere, CSps）移植减轻不良心室重构的细胞与组织层面机制。 研究背景：心脏球（cardiosphere, CSps）是源自心脏的多细胞簇，富含干细胞特性且具备多系分化能力。已有大小动物实验证实，心肌梗死后心脏球移植可改善左心室（left ventricular, LV）功能并减轻心室重构，但目前其获益机制尚未完全阐明。 研究方法：本研究设置四组实验对象：1）假手术组（Sham）：仅对Wistar Kyoto大鼠行开胸及丝线结扎操作，未造成心肌梗死；2）心肌梗死组（MI）：结扎近端左前降支（left anterior descending artery, LAD），并在梗死周边区域注射溶剂；3）心脏球移植组（MI+CSp）：行近端LAD结扎后于梗死周边区域注射心脏球；4）小梗死组（Small MI）：仅结扎中段LAD。 研究结果：体内实验显示，心脏球移植后1周，左心室功能改善与心肌细胞增殖增加相关；至移植后3周，微血管生成增强，同时心肌细胞肥大与区域纤维化得到缓解，胶原沉积减少、胶原降解增强，且基质金属蛋白酶（matrix metalloproteinases, MMPs）表达上调。小梗死组未观察到心脏球移植的获益效应，提示其作用并非仅由心脏球诱导的心肌保护所介导。体外实验中，心脏球条件培养基可在与成纤维细胞共培养时减少胶原生成，并在离体主动脉环实验中诱导新生血管生成。 研究结论：心脏球可在缺血心肌中促进心肌细胞增殖与血管生成，并缓解心肌细胞肥大与纤维化。这些协同效应是心脏球移植减轻不良心室重构的核心机制。