Regenerating Hair Follicles

In 2007, Ito et al. observed structures resembling early developing hair follicles in healing skin wounds in mice. This process, known as hair follicle neogenesis, occurred in adult mice after injuries that resulted in healed wounds 0.25 cm2 or larger. The newly generated follicles, which proliferated and produced unpigmented hair, appeared to arise from extrafollicular epidermal cells or infundibular cells, not from existing hair follicle stem cells. The process was associated with the expression of the same genes and proteins found during embryonic follicle development. Wnt signaling, which has been implicated in hair follicle development, was found to be crucial for this process. Inhibition of Wnt signaling prevented hair follicle neogenesis, while overexpression of Wnt7a enhanced wound-dependent hair follicle regeneration. The authors suggested that modulating Wnt signaling in wounds could provide a means of decreasing scarring and treating alopecia.