Title
Absence of type VI collagen paradoxically improves cardiac function, structure, and remodeling after myocardial infarction.
Description
RATIONALE: We previously reported that type VI collagen deposition increases in the infarcted myocardium in vivo. To date, a specific role for this nonfibrillar collagen has not been explored in the setting of myocardial infarction (MI). OBJECTIVE: To determine whether deletion of type VI collagen in an in vivo model of post-MI wound healing would alter cardiac function and remodeling in the days to weeks after injury. METHODS AND RESULTS: Wild-type and Col6a1(-/-) mice were subjected to MI, followed by serial echocardiographic and histological assessments. At 8 weeks after MI, infarct size was significantly reduced, ejection fraction was significantly preserved (43.9% +/- 3.3% versus 29.1% +/- 4.3% for wild-type), and left ventricular chamber dilation was attenuated in the Col6a1(-/-) MI group (25.8% +/- 7.9% increase versus 62.6% +/- 16.5% for wild-type). The improvement in cardiac remodeling was evident as early as 10 days after MI in the Col6a1(-/-) mice. Myocyte apoptosis within the infarcted zones was initially greater in the Col6a1(-/-) group 3 days after MI, but by day 14 this was significantly reduced. Collagen deposition also was reduced in the infarcted and remote areas of the Col6a1(-/-) hearts. The reductions in chronic myocyte apoptosis and fibrosis are critical events leading to improved long-term remodeling and functional outcomes. CONCLUSIONS: These unexpected results demonstrate for the first time that deletion of type VI collagen in this knockout model plays a critical protective role after MI by limiting infarct size, chronic apoptosis, aberrant remodeling, and fibrosis, leading to preservation of cardiac function.
Subject
Animal; Animals; Apoptosis/physiology; Cardiac/pathology/physiology; Collagen Type VI/*genetics/*metabolism; Disease Models; Echocardiography; Extracellular Matrix/metabolism/pathology; Fibrosis/genetics/pathology/physiopathology; Knockout; Male; Mice; Myocardial Infarction/diagnostic imaging/*genetics/*physiopathology; Myocytes; Ventricular Remodeling/*physiology