Mechanisms by which late coronary reperfusion mitigates postinfarction cardiac remodeling
Munehiro Nakagawa1, Genzou Takemura, Hiromitsu Kanamori
1Division of Cardiology, Gifu University Graduate School of Medicine, Gifu, Japan.
Insights
Late reperfusion after myocardial infarction (MI) preserves heart function by promoting a thicker, cell-rich scar. This late reperfusion strategy reduces cardiac remodeling and improves survival through enhanced cell proliferation and reduced apoptosis.
Area of Science:
- Cardiovascular Biology
- Regenerative Medicine
- Pathophysiology
Background:
- Late reperfusion following myocardial infarction (MI) is associated with reduced cardiac remodeling and mortality.
- The precise mechanisms underlying these beneficial effects remain incompletely understood.
Purpose of the Study:
- To investigate the cellular and molecular mechanisms by which late reperfusion (LR) influences cardiac repair and function post-MI.
- To compare the effects of opening the infarct-related artery 24 hours after MI versus permanent occlusion.
Main Methods:
- Comparison of infarcted rat hearts with late reperfusion (LR) versus permanently occluded arteries.
- Assessment of left ventricular dimensions, function, cell proliferation, and apoptosis at various time points post-MI.
- In vitro studies to confirm hypoxia-induced apoptosis in infarct tissue-derived myofibroblasts.
Main Results:
- Late reperfusion significantly mitigated left ventricular dilatation and dysfunction up to 4 weeks post-MI.
- The infarcted wall was thicker and more cellular in the LR group, correlating with reduced wall stress.
- LR enhanced granulation tissue cell proliferation and decreased apoptosis, contributing to scar quality.
- Myocardial debris removal and collagen synthesis were accelerated in the LR group.
- Hypoxia directly accelerated Fas-mediated apoptosis in vitro.
- Salvaged cardiomyocytes showed reduced degenerative changes and restored protein expression in the LR group.
Conclusions:
- Late reperfusion promotes a thicker, cell-rich scar by increasing cell proliferation and reducing apoptosis in the infarct zone.
- Accelerated debris clearance and enhanced collagen synthesis contribute to improved scar quality and function.
- These findings provide an additional pathophysiological basis for the benefits of late reperfusion therapy after myocardial infarction.
Abstract:
Although recanalization of the infarct-related artery late after myocardial infarction (MI) is known to reduce both cardiac remodeling and mortality, the mechanisms responsible are not yet fully understood. We compared infarcted rat hearts in which the infarct-related coronary artery was opened 24 hours after infarction (late reperfusion [LR] group) with those having a permanently occluded artery. Left ventricular dilatation and dysfunction were significantly mitigated in the LR group 1, 2, and 4 weeks post-MI. Attributable, in large part, to the greater number of cells present, the infarcted wall was significantly thicker in the LR group, which likely reduced wall stress and mitigated cardiac dysfunction. Granulation tissue cell proliferation was increased to a greater degree in the LR group 4 days post-MI, whereas the incidence of apoptosis was significantly lower throughout the subacute stage (4 days, 1 week, and 2 weeks post-MI), further suggesting preservation of granulation tissue cells contributes to the thick, cell-rich scar. Functionally, myocardial debris was more rapidly removed from the infarcted areas in the LR group during subacute stages, and stouter collagen was more rapidly synthesized in those areas. Direct acceleration of Fas-mediated apoptosis by hypoxia was confirmed in vitro using infarct tissue-derived myofibroblasts. In salvaged cardiomyocytes, degenerative changes, but not apoptosis, were mitigated in the LR group, accompanied by restoration of GATA-4 and sarcomeric protein expression. Along with various mechanisms proposed earlier, the present findings appear to provide an additional pathophysiological basis for the benefits of late reperfusion.
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