Abstract
Vasoactive intestinal peptide (VIP), a neuropeptide released by sensory nerve fibers in the skin, T cells, macrophages, keratinocytes, dermal microvascular endothelial cells, Merkel cells, and smooth muscle cells, exerts its influence through the widely expressed receptors VPAC1 and VPAC2, which play a pivotal role in the intricate physiology of both the epidermis and hair follicles (HFs). Our preliminary pilot data suggest that VIP may play a key role in promoting the transformation of amelanotic human hair bulb melanoblasts into fully functional melanocytes, capable of melanin production within the hair follicle pigmentary unit (HFPU), particularly in female donors.
This study was dedicated to exploring VIP's role in regulating human scalp HF melanogenesis. To investigate this, we obtained frontotemporal human scalp skin specimens from healthy patients undergoing cosmetic facelift surgery and isolated hair follicles used in hair transplantation. Male donor hair follicles were systematically treated with two different concentrations of VIP (100nM and 1uM) or a control vehicle for six days, administered every other day. Our investigation discovered a significant reduction in melanin production within male donor HFs following VIP treatment, which diverges from our initial expectations based on data from female donors.
Knowing the role of VIP as a guardian of immune privilege within hair follicles, combined with its newfound influence on HF pigmentation, a critical question emerges: why is the reduction of melanin crucial for safeguarding hair follicles against potential damage? The answer to this intriguing puzzle is multifaceted. It will need further investigation to comprehensively understand its specific impact on hair pigmentation and its possible relevance to conditions such as alopecia areata.