Role of inflammatory populations and their intermediates in post-ischemic adverse remodeling in rat model of myocardial infarction

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Junta de Andalucía- Fondos FEDER

Compelling evidence demonstrated the critical role of inflammation in ventricular adverse remodeling after acute myocardial infarction. However, it remains unclear how inflammatory cell population and their intermediates participate in the progress of the disease.

This study aims to elucidate the role of inflammatory population in cardiac remodeling after myocardial infarction in a rat model, focusing on their role in fibrosis.

We used a surgical procedure by transient ligation of the left descendant coronary artery, to evoke ischemia-reperfusion (I/R) in rats. We performed FACS analysis to evaluate counts of neutrophils and two monocytes’ subsets: CD43lowHis48high (classical monocytes), and CD43highHis48low (non-classical monocytes), which are the most pro-inflammatory subset in peripheral blood. Subsequently, we performed immunofluorescence to detect pro-inflammatory M1 and M2 macrophages (CD68+ and CD163+) in the rat infarcted myocardium. Moreover, we sorted the two monocyte subsets and performed genes and microRNAs Array.

FACS analysis of neutrophils and monocytes subsets showed an increased level of these cells in the rat model of myocardial infarction, one week after the post-ischemic event. In parallel, the infiltration of M1 macrophages was increased in the myocardium until 1 week after surgery, indicating a long extravasation of inflammatory cells after the ischemic event. Moreover, co-culture of fibroblasts and cardiomyocytes with intermediates released by inflammatory cells subjected to I/R increased the expression of fibrotic and apoptotic genes. In addition, the analysis of genes’ Array by GSEA indicated that CD43highHis48low monocytes had an enrichment score in pathways associated with angiogenesis, fibrosis and inflammation, while CD43lowHis48high population exhibited an enrichment in cytokines and inflammation, apoptosis and fibrosis. Finally, we found significant overexpression of microRNAs, for instance, miR-27a-3p, miR-29b-3p, miR-30e-5p and miR-194-5p in CD43highHis48low 24h after the I/R procedure. Those miRNAs are predicted to modulate pro-fibrotic genes.

The level of inflammatory cell populations is increased in I/R rat model. Moreover, these cells infiltrate in the myocardium likely to change the transcriptome of resident cells towards a pro-apoptotic and pro-fibrotic phenotype.