In order to assess the effect of daily exercise on extracellular matrix remodeling in the heart after myocardial infarction (MI), we measured collagen concentration (%COL) and nonreducible collagen cross-linking (hydroxylysylpyridinoline, HP) in the right ventricle (RV), and regionally within the infarcted (INF) and viable left ventricular free wall (LVF) and septum (LVS), using a rodent MI training model.
Infarcts (19%–24% of LV) were surgically induced in adult rats that were assigned to either trained (MI-TR) or sedentary (MI-SED) groups and compared to sham–surgery sedentary controls (SHAM).
In LVF, 10 wk of treadmill running had no effect on the increase (P < 0.001) in %COL seen with MI (MI-SED = 7.14% ± 0.15%, MI-TR = 7.61% ± 0.19%, SHAM = 3.55% ± 0.19%). However, it normalized the increase (P < 0.05) in HP cross-linking (MI-SED = 0.43 ± 0.02, MI-TR = 0.27 ± 0.03, SHAM = 0.30 ± 0.04 mol HP·mol−1 collagen). The INF scar in MI-SED rats showed a sevenfold increase in %COL (P < 0.001) compared to SHAM LVF myocardium, an increase that was attenuated by training (MI-SED = 26% ± 1% vs MI-TR = 21% ± 2%; P < 0.05). However, training had no effect on MI-induced increases in cross-linking in the INF scar (1.01 ± 0.22 vs 0.84 ± 0.14 mol HP·mol−1 collagen). In LVS, although a small but significant increase in %COL was seen in both MI groups, HP cross-linking was unaltered compared to SHAM rats. Training also normalized the increase observed in cross-linking in RV after MI.
Because increased HP cross-linking in the heart is associated with decreased chamber compliance, these findings may help to explain the improved heart function seen after daily exercise in cardiac rehabilitation patients.
1Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA; 2Department of Biomedical Sciences, Missouri State University, Springfield, MO; 3Department of Animal Science, University of Wyoming, Laramie, WY; 4Department of Zoology and Physiology, University of Wyoming, Laramie, WY; and 5Division of Kinesiology & Health, University of Wyoming, Laramie, WY
Address for correspondence: D. Paul Thomas, Ph.D., FACSM, Division ofKinesiology and Health, College of Health Sciences, University of Wyoming, Dept. 3196, 1000 E University Ave, Laramie, WY 82071; E-mail: firstname.lastname@example.org.
Submitted for publication October 2011.
Accepted for publication December 2011.