Plasticity and Cytokinetic Dynamics of the Hair Follicle Mesenchyme: Implications for Hair Growth Control

The study investigated the dynamics of the hair follicle mesenchyme, focusing on the follicular papilla (FP) and connective tissue sheath (CTS) in C57BL/6 mice. It found that during hair growth, the FP size increased due to cell proliferation and migration from the CTS, with the FP cell numbers peaking at anagen VI before decreasing by 25% during sustained hair production. This decrease was not due to apoptosis but rather fibroblast migration back to the CTS. The study highlighted the significant plasticity of the hair follicle mesenchyme, suggesting that these dynamics could be crucial for understanding hair follicle transformations, such as those seen in androgenetic alopecia. The findings challenged the belief that the hair follicle mesenchyme was a stable population without proliferative potential and proposed that the CTS played a major role in driving the reconstruction of the anagen FP, potentially serving as a target for pharmacologic intervention in hair growth studies.