Cellular immunophenotypes in human embryonic, fetal and adult heart

The cellular immunoprofile of cardiac dysfunctions and lesions of ischemic etiology are insufficiently studied to date, especially regarding the contribution of non-cardiomyocytic structures. Aiming to explore this immunoprofile, we used immunohistochemistry applied on embryonic, fetal and adult normal or ischemic myocardium. We observed a decrease of smooth muscle alpha-actin expression in fetal vs. embryonic cardiomyocytes, its absence in normal adult myocardium and its intense expression in the fibrotic scars of ischemic myocardium. DDR2 and vimentin, which are present in the interstitial cells and cardiomyocytes of the embryo, fetus and normal adult heart, are absent in the fibrotic scar tissue and cicatricial infarction, the latter expressing smooth muscle alpha-actin and CD34. This suggested that myofibroblasts and not local fibroblasts that participate in ischemic remodeling. An EGFR-positive vascular network was better represented in the ischemic heart than in the adult normal one, a fact possibly related to EGFR implication in cardiac ischemic pre- and post-conditioning. Therefore, cardiomyocytes and non-cardiomyocytic cells have an undulating immunoprofile according to the intrauterine life stage or age after birth, and a variable contribution in cardiac lesions, mostly in ischemic ones.