Structural Composition of Myocardial Infarction Scar Does Not Differ Between Male and Female Middle‐Aged Rats

Abstract

A number of studies indicate that females have a better reparative response in earlier stages of myocardial infarction (MI) compared to males. Nevertheless, little is known concerning the sex‐related differences in a later stage of MI healing (i.e. scar formation). Accordingly, we designed our study to determine whether the composition of the scar is affected by the biological sex of post‐MI animals. A large MI was induced in 12‐month‐old male (M‐MI) and female (F‐MI) Sprague‐Dawley rats by ligation of the left coronary artery. Four weeks after the MI, rats with transmural infarctions, greater than 50% of the left ventricular free wall, were evaluated. The fractional volume of fibrillar collagen (FC), cardiac myocytes (CM), myofibroblasts (MF) and vascular smooth muscle cells (VSMC) was determined in each scar. The mean scar size and thickness were comparable between F‐MI and M‐MI rats (61.3±3.9% vs. 63.8±2.5% and 0.66±0.04mm vs. 0.73±0.05mm, respectively). Although, there was a great degree of heterogeneity in spatial distribution of the analyzed structural components within each scar, their mean content showed no significant differences between F‐MI and M‐MI rats (FC: 53.3±6.6% vs. 61.6±4.5%; CM: 3.1±0.4% vs. 3.3±0.4%; MF: 9.6±1.2% vs. 9.6±1.7%; VSMC: 3.4±0.5 vs. 2.3±0.5%). Our data are the first to demonstrate that biological sex does not influence the structural composition of the MI scar in middle‐aged rats.Grant Funding Source: Internal Award from the NYCOM Office of Research (E.I. Dedkov) and NIH RO1‐HL62587 (R.J. Tomanek)