Organ-Level Quorum Sensing Directs Regeneration in Hair Stem Cell Populations

The study demonstrated that organ-level quorum sensing in hair follicles allowed for coordinated regeneration in response to patterned hair plucking. Plucking hair at varying densities resulted in the regeneration of up to 5 times more neighboring, unplucked hairs, suggesting a collective decision-making process. The quorum signal was estimated to have a range of about 1 mm. The mechanism involved a two-step process where CCL2 released from injured hairs recruited TNF-α-secreting macrophages, which then signaled to both plucked and unplucked follicles. This coupling of immune response with regeneration enabled the skin to predictively respond to injury, activating stem cells in response to significant distress while ignoring mild injury.