Appreciation of a central role for recruited monocyte-derived macrophages to repair organs
after injury is gaining considerable momentum. In the past 2 years, monocyte-derived tissue
leukocytes have been identified as orchestrators of repair in skin, muscle, gut, brain, and
heart. Macrophages, however, exhibit considerable plasticity in their phenotype and can
polarize into functional states that additionally contribute to tissue injury or fibrosis. These
functional states have become known as M1 for pro-injurious functions and M2 for …