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

The study demonstrated that hair follicle regeneration in response to injury was coordinated through a mechanism similar to quorum sensing, where plucking hair at varying densities triggered regeneration of up to 5 times more neighboring, unplucked hairs. This process involved the release of CCL2 from injured hairs, recruiting TNF-α-secreting macrophages, which were crucial for regeneration. The signaling range was about 1 mm, indicating a longer signaling length scale than typical diffusible molecular cues. Experiments with CCL2 null mice showed delayed hair regrowth, emphasizing CCL2's role. The study highlighted the potential to exploit stem cell social behavior to enhance regeneration reliability, suggesting that quorum sensing could be a common principle in tissue and organ regeneration beyond the skin.