P864Histopathological damages in the epicardial coronary artery after ischemia and reperfusion injury in swine
Authors: Rios Navarro C , Ruiz-Sauri A , Daghbouche-Rubio N , Gavara J , Marcos-Garces V , Minana G , Chorro F J , Bodi V 
Published: October 2019

Abstract

Background
The microscopic consequences in the myocardial capillaries after myocardial infarction (MI) have been widely addressed, but little attention has been paid to epicardial coronary arteries. Since epicardial circulation is responsible for providing blood flow to the heart, understanding the microscopical changes on the epicardial artery after MI becomes also crucial.

Purpose
To evaluate the dynamics of the microscopic damages in the coronary arteries post-MI in swine model of reperfused MI.

Methods
MI was induced in swine by transient 90-min coronary occlusion of the left anterior descending (LAD) coronary artery using angioplasty balloons. One control group and four MI groups were defined: 1) without reperfusion, and 2) 1-min, 3) 1-week, and 4) 1-month reperfusion (n=3, each). In each group, LAD (infarct-related artery) and the right coronary artery (RCA) were isolated. Taking as reference the region in which balloon was inflated, we also separated samples from two different regions: proximal and distal LAD. Histological stainings (HE, Masson's trichromic, and orcein) and immunohistochemistry against CD31 (endothelial cells), a-smooth muscle cells, and CD45 (total leukocytes) were performed.

Results
Abnormalities in the endothelial monolayer of the LAD artery started even before reperfusion (during ischemia). This damage dramatically increased after reperfusion, observing an almost absence of CD31+ cells in the tunica intima and some breaks in the internal elastic layer from the 1-min and 1-week reperfusion groups. No irregularities were found in the tunica media from the no reperfusion group, whereas an increased in its thickness was detected soon after reperfusion. In the 1-week reperfusion group, larger thickness, a desorganized muscular cells distribution, and oedema were found. The damage in the tunica intima and media was more pronounced in the region distal to the angioplasty balloon compared to the proximal region, whereas no changes were detected in the RCA. In the tunica adventitia, vasa vasorum density was reduced during the ischemic phase, remaining low in the 1-min and 1-week reperfusion group, while being restored after 1-month reperfusion. This dynamics was similar in both LAD regions, while no changes in the RCA were found. After coronary reperfusion, a higher leukocyte adhesion to the endothelium from the LAD artery, mainly in the region proximal to the balloon inflation, was observed. The process evolves, resulting in a massive presence of CD45+ cells not only in the tunica intima, but also in the media and the adventitia monolayer isolated from the 1-week reperfusion group.

Conclusions
The microscopic structure of the infarct-related coronary artery was compromised after MI. This damage started during ischemia and boosted after reperfusion, becoming more pronounced in the region distal to balloon inflation. Exploring these damages will be important for a better understanding of the pathophysiology of MI.

Acknowledgement/Funding
This study was funded by “Instituto de Salud Carlos III” and “Fondos Europeos de Desarrollo Regional FEDER” (PIE15/00013, PI17/01836, and CIBERCV16/11