Hair Growth Induced by Blockade of Macrophage-Derived Oncostatin M and Downstream JAK-STAT5 Signaling in Hair Follicle Stem Cells

In the 2018 study by E Wang and A Christiano, it was found that hair growth can be induced by blocking the action of a cytokine called Oncostatin M (OSM), which is produced by a specific subset of macrophages in the skin. OSM acts through the JAK-STAT5 signaling pathway to maintain hair follicle stem cells (HFSCs) in a quiescent state. By conditionally ablating the OSM receptor (OSMRB) or STAT5 in mouse skin during the resting phase of the hair cycle, the researchers observed a significant shortening of this phase and an activation of HFSCs. Additionally, they discovered that depleting the macrophages that produce OSM, using various methods such as neutralizing antibodies or small-molecule inhibitors, resulted in hair growth and increased proliferation of HFSCs. This study highlights the role of immune cells in regulating HFSC quiescence and suggests potential new treatments for hair disorders involving arrested hair follicles by targeting cells outside the hair follicle itself.