Figure 1.

Developmental origin and subtype function of cardiac macrophages. Embryonic development (E7.5-E12.5) revolves around the hematopoietic endothelium (HE) of the yolk sac (YS), which undergoes three waves of hematopoiesis. A short period of deterministic hematopoietic cells migrates to the fetal liver after generating YS macrophages or multiple lineages, which subsequently develop into resident macrophages and eventually migrate to the embryonic heart. During the perinatal period, traditional bone marrow hematopoietic stem cells (HSCs) will become the primary site of hematopoiesis, differentiating into circulating monocytes and macrophages in the peripheral blood to produce a full immune lineage. In adult mice, resident cardiac macrophages are depleted after myocardial infarction and mononuclear-derived macrophages are recruited and enriched in large numbers and subsequently partially restored to the level of the uninjured state.