A Subset of TREM2+ Dermal Macrophages Secretes Oncostatin M to Maintain Hair Follicle Stem Cell Quiescence and Inhibit Hair Growth

In 2019, researchers discovered that a subset of TREM2+ dermal macrophages, also known as trichophages, secrete Oncostatin M (OSM), a cytokine that inhibits hair growth by keeping hair follicle stem cells (HFSCs) in a resting state. This is achieved through the OSM-OSMRβ-STAT5 signaling pathway. When these macrophages were removed, hair growth and HFSC activation occurred. Genetic deletion of the OSM receptor or STAT5 also led to premature HFSC activation, indicating that the resting stage of hair growth is actively maintained by the hair follicle niche. The study suggests that manipulating this pathway could potentially regulate hair growth.