Macrophage-Stimulating Protein Promotes Hair Growth Ex Vivo and Induces Anagen from Telogen Stage Hair Follicles In Vivo

In the 2004 study by McElwee et al., macrophage-stimulating protein (MSP) was shown to promote hair growth in human hair follicles ex vivo and to induce the anagen phase in telogen stage hair follicles in vivo. MSP was found in cultured human dermal papilla and dermal sheath cells, and its receptor RON was expressed in hair follicles. In vitro, human hair follicles treated with MSP for 8 days grew significantly longer than controls. In vivo, mice injected with MSP showed visible hair growth by day 16, unlike control mice. The study suggests MSP could be a modulator of hair growth and might be used to treat hair loss. The ex vivo experiments used hair follicles from five human volunteers, while the in vivo experiments used groups of C3H/HeJ mice, with specific numbers detailed in the methods section.