Dermal TRPV1 Innervations Engage a Macrophage- and Fibroblast-Containing Pathway to Activate Hair Growth in Mice

The study explores the role of TRPV1 activation in promoting hair growth in mice, highlighting a pathway involving macrophages and fibroblasts. Activation of TRPV1 leads to accelerated hair growth by triggering regenerative cycling in dormant hair follicles, mediated by the neuropeptide CGRP and the expansion of Spp1-expressing dermal fibroblasts. The study demonstrates that blocking Spp1 significantly reduces hair growth, emphasizing its importance. Macrophages are also crucial, as their depletion or reduced CGRP sensitivity diminishes fibroblast induction and hair growth. The findings suggest that TRPV1 activation can stimulate hair growth through a complex interaction between neurons, macrophages, and fibroblasts, offering potential therapeutic insights for hair loss.