Exercise training post-MI favorably modifies heart extracellular matrix in the rat.
OBJECTIVE
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.


METHODS
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).


RESULTS
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.


CONCLUSIONS
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.
Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA, USA.
Christopher M
CM
Yengo
Scott D
SD
Zimmerman
Richard J
RJ
McCormick
D Paul
DP
Thomas
D000704:Analysis of Variance; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D004562:Electrocardiography; D005109:Extracellular Matrix / Q000378:metabolism*; D006346:Heart Septum / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D006909:Hydroxyproline / Q000378:metabolism; D009203:Myocardial Infarction / Q000378:metabolism / Q000534:rehabilitation*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats
D003094:Collagen; D006909:Hydroxyproline