Heart-resident macrophages: are they involved in the rhythm of every beat?

Macrophages are one of the main components of the innate immune system and play a major role in cardiovascular disease (1,2). These cells are derived from blood monocytes and differentiate into tissue macrophages. They are well known for their immunologic roles including phagocytosis and antigen presentation. The role of macrophages in normal and disease physiology, however, is much more complex as illustrated by the fact that they can develop into distinct functional phenotypes depending upon their microenvironment. Different sub-populations of macrophages have been characterized, of which M1 “inflammatory” macrophages and “pro-healing” M2 macrophages are the most studied (3).