Macrophages, Wound Healing, and Fibrosis: Recent Insights

Purpose of Review Macrophages are central players in the immune response following tissue injury. These cells perform many functions, and the changing tissue microenvironment during injury shapes macrophage phenotype down a variety of polarized pathways. This review summarizes the current knowledge on the roles of macrophages during different stages of tissue injury, repair, and-if repair is not achieved-fibrosis. Recent Findings Macrophages present early in inflammation are functionally distinct from those at later stages. The predominant macrophage phenotype must transition from pro-inflammatory to pro-reparative to facilitate wound healing and scar resolution. If macrophages fail to acquire a tissue-healing phenotype, dysregulated signals can be drivers of disease processes, such as sustained, exuberant inflammation-as occurs in arthropathies-and fibrosis. Summary Comprehensive understanding of the roles of specific macrophage populations at different stages of the repair process will support the development of immune-targeted therapies for diseases such as fibrosis.