The Bulge: The Location of Follicular Stem Cells

The Hair Follicle Bulge

Hair follicle stem cells are cells with the potential to generate new hairs and potentially even other tissue types as well. There is an incredibly important area of the hair follicle where stem cells live. This area is known as the “bulge” and is located where the arrector pili muscle inserts into the outer root sheath (see pink dot in diagram). It was Dr George Cotsarelis, together with Dr Robert Lavker who discovered back in 1990 that the bulge was the location where hair follicle stem cells reside. Dr Cotsarelis was a dermatology resident at the time he made these breakthrough discoveries. He has since contributed to some of the most important discoveries in hair research in recent times.

Reference

Cotsarelis G et al. Label-retaining cells reside in the bulge area of pilosebaceous unit: implications for follicular stem cells, hair cycle, and skin carcinogenesis. Cell. 1990.