LAUSR

The human heart contains CC chemokine receptor type 2 (CCR2)+ and CCR2 macrophage subsets with distinct origins and functions, similar to the macrophage heterogeneity found in mouse hearts. Investigators used transmural left ventricular (LV) myocardial specimens collected during heart transplantation or the implantation of an LV assist device in patients with dilated or ischaemic cardiomyopathy. Analysis of sexmismatched heart transplantation recipients showed that CCR2+ macrophages are maintained through monocyte recruitment and proliferation. By contrast, CCR2 macrophages are replenished exclusively by local proliferation and are a tissueresident population. The subsets of macrophages have distinct functions, analogous to the inflammatory CCR2+ and reparative CCR2 macrophages in mouse hearts. Of note, CCR2+ macrophage abundance is associated with systolic function and LV remodelling in patients with heart failure.