Abstract We055: Role of Classical Dendritic Cells in the Sterile Inflammatory Response Following Myocardial Infarction

Abstract

Myocardial infarction and the subsequent development of chronic ischemic cardiomyopathy is the most common cause of congestive heart failure. Infarction is associated with an intense sterile inflammatory response which can lead to adverse remodeling over the long term. Dendritic cells (DCs) are antigen presenting cells that function as a bridge between innate and adaptive immunity. Precursor DCs give rise to several distinct classical DC (cDC) subsets that mediate a variety of functions. The cDC1 subset is essential for cross-presentation of antigens to CD8 + T cells, while the cDC2 lineage is a potent inducer of CD4 + T cell proliferation. The aim of the study was to characterize the profile of the cDC populations present during the various stages of the development of chronic ischemic cardiomyopathy. We hypothesized that cDCs are essential mediators of chronic LV remodeling in the period following ischemic myocardial injury. We sought to determine which specific cDC subtype (cDC1 vs cDC2) forms the predominant population in the heart and secondary lymphoid tissues following ischemic injury. Adult male C57BL/6 (WT) mice underwent non-perfused myocardial infarction by ligating the left anterior descending artery (LAD) to induce sterile injury, with sham operated mice used as controls. Left ventricular (LV) remodeling was assessed by echocardiography at 1 w and 8 w following surgery. Alterations in cDC1 (CD45+CD11c+CD103-XCR1-) and cDC2 (CD45+CD11c+CD103+XCR1+) profile were examined by flow cytometry. When compared with the sham operated mice, mice with ischemic cardiomyopathy following LAD ligation exhibited the following features. There is an initial influx of cDC2 into the myocardium 1 w after MI (mean of 3.0% vs 0.26% of CD45 + leukocytes, p=0.02). This is followed by a subsequent influx of cDC1 into the myocardium 4 weeks after MI (mean of 1.98% vs 0.16% of CD45 + leukocytes, p=0.001). This influx of cDC into the heart is accompanied by an egress of cDC from the spleen (mean of 0.37% vs 0.76% of CD45 + leukocytes, P=0.001) at 4 weeks following MI. In conclusion, the findings of our study suggest that there is an initial influx of cDC2 followed by a more sustained influx of cDC1 into the myocardium in the weeks following an infarct. Antigen presentation by cDC likely plays a critical role in driving the inflammatory response and inducing chronic LV remodeling in the period following MI.