Vitamin A Metabolism During Refractory Telogen

The study investigated the role of retinoic acid (RA) synthesis and signaling in the hair cycle, particularly during the refractory telogen phase, which is a period of rest for hair follicles characterized by the expression of bone morphogenetic protein 4 (BMP4). The research focused on female C57BL/6 J mice and examined the localization of proteins involved in RA metabolism, such as SDR16C5, RDH10, ALDH1A2, CRABP2, CYP26B1, and BMP4, within the hair follicles during telogen. The findings indicated that all these proteins were present in BMP4 positive refractory telogen hair follicles, with varying levels observed in BMP4 negative competent telogen follicles. Additionally, the study found that both low and excess dietary vitamin A led to a higher percentage of hair follicles in refractory telogen, suggesting that RA synthesis and signaling might be more active during this phase and could contribute to the inhibition of the hair cycle. The research was supported by NIH/NIAMS and internal funding.