In an animal model of angiotensin II-induced myocardial fibrosis, a matrix metalloproteinase-9 (MMP-9) knockout mouse model of myocardial infarction, and a mouse model of aging, M2 macrophages accumulate in large numbers and promote fibroblast activation and collagen synthesis and secretion (84). This evidence concerns the gene AGT and Myocardial fibrosis.