Remodeling in early myocardial infarction: alteration of extracellular matrix; Collagen-1, Collagen-3, α-SMA, and α-Actinin in Porcine heart model

Background: Myocardial infarction (MI) leads to remodeling due to altered cardiac structure and function. The study of MI histopathology in humans or large animals mimicking the human heart is limited. Using the porcine heart model, our study investigated the composition of myocardial extracellular matrix (ECM) in collagen-1, collagen-3, α-smooth muscle actin (α-SMA), and α-actinin before and after myocardial infarction. Methods: This study used two groups of domestic pigs: the Infarct group (n=4) and the Sham group (n=4). MI was induced by permanent ligation of the proximal branch of the posterior left ventricular artery. Cardiac enzymes, electrocardiography, and echocardiography data were collected before and after ligation. Cardiac tissue was harvested from the infarcted area after 60 minutes of ligation and stained with hematoxylin-eosin and Movat’s Pentachrome. Collagen-1, collagen-3, and α-SMA were identified with immunohistochemical labeling, and the labeled area was measured using ImageJ. Meanwhile, α-actinin was visualized using immunofluorescence. Results: Expression of collagen-1, collagen-3, and α-SMA in the infarct group were significantly decreased after 60 minutes of infarction compared with those in the sham group (p<0.01). The α-actinin was fragmented and diminished in the infarct group. Conclusion: Myocardial remodeling was detected 60 minutes after infarction with mild alteration in myocardial histoarchitecture and significant deterioration of ECM composition of collagen-1, collagen-3, α-SMA, and fragmented α-actinin fibers in the porcine heart model.