Institution of localized high-frequency electrical stimulation targeting early myocardial infarction: Effects on left ventricle function and geometry

Large Animal Models of Cell-Free Cardiac Regeneration

The adult mammalian heart lacks the ability to sufficiently regenerate itself, leading to the progressive deterioration of function and heart failure after ischemic injuries such as myocardial infarction. Thus far, cell-based therapies have delivered unsatisfactory results, prompting the search for cell-free alternatives that can induce the heart to repair itself through cardiomyocyte proliferation, angiogenesis, and advantageous remodeling. Large animal models are an invaluable step toward translating basic research into clinical applications. In this review, we give an overview of the state-of-the-art in cell-free cardiac regeneration therapies that have been tested in large animal models, mainly pigs. Cell-free cardiac regeneration therapies involve stem cell secretome- and extracellular vesicles (including exosomes)-induced cardiac repair, RNA-based therapies, mainly regarding microRNAs, but also modified mRNA (modRNA) as well as other molecules including growth factors and extracellular matrix components. Various methods for the delivery of regenerative substances are used, including adenoviral vectors (AAVs), microencapsulation, and microparticles. Physical stimulation methods and direct cardiac reprogramming approaches are also discussed.

Interstitial changes after reperfused myocardial infarction in swine: morphometric and genetic analysis

Background

Following myocardial infarction (MI), we aimed to characterize morphometric and genetic changes in extracellular matrix (ECM) components from ischemia onset until late phases after coronary reperfusion in necrotic and salvaged myocardium.

Results

Swine were divided into one control (n = 5) and three MI groups: 90-min of ischemia without reperfusion, or followed by 1-week or 1-month reperfusion (n = 5 per group). In samples from the necrotic and salvaged areas, ECM components were morphometrically quantified and mRNA levels of factors involved in ECM remodeling were evaluated. After 90-min of ischemia, fibronectin, laminin, and elastic fibers content as well as upregulated mRNA expression of tissue inhibitors of metalloproteinases (TIMP)1, TIMP2, TIMP3 and connective tissue growth factor increased in the necrotic and salvaged myocardium. In both reperfused MI groups, collagen-I, collagen-III, elastic fibers, glycosaminoglycans, laminin, and fibronectin levels heightened in the necrotic but not the salvaged myocardium. Moreover, mRNA expression of TIMP1, TIMP2 and TIMP3, as well as metalloproteinase-2 and metalloproteinase-9 heightened in the necrotic but not in the salvaged myocardium.

Conclusions

Matrix remodeling starts after ischemia onset in both necrotic and salvaged myocardium. Even if ECM composition from the salvaged myocardium was altered after severe ischemia, ECM makes a full recovery to normal composition after reperfusion. Therefore, rapid coronary reperfusion is essential not only to save cardiomyocytes but also to preserve matrix, thus avoiding impaired left ventricular remodeling.