Based on trichogram evidence, it has been claimed that, once terminal (T) scalp hair follicles (HFs) have been fully miniaturized into vellus (V) HFs in androgenetic alopecia (AGA), these cannot be reconverted into T HFs, even under therapy (Rushton et al. Exp Dermatol 2022). If true, this would mandate early intervention in AGA management, and would render hair transplantation the only meaningful therapy for late-stage AGA. Given that hypertrichosis-inducing drugs and hormones can rapidly induce V-T HF conversion, we wished to probe the validity of this provocative postulate by generating irrefutable histological evidence, using our novel humanized AGA mouse model under long-term therapy with minoxidil (MXL) or platelet rich plasma (PRP). Biopsies were obtained from 10 male pattern AGA patients (mean age: 35.9±9.4 years) and transplanted onto SCID/beige mice. 5 mice were treated once daily with 5% topical MXL, and 5 once monthly with intradermal injection of autologous PRP for 4 months. PRP was generated by isolating platelets from blood of patients and activating them with 10% calcium chloride (CaCl2). Quantitative histomorphometry of the xenotransplants after 4 months revealed a significantly decreased number of V and intermediate HFs in both groups of treated human scalp skin transplants as compared to the AGA scalp skin of the donors before transplantation (p<0.05, p<0.01, respectively), along with a significantly increased number of T HFs (p<0.05). This strongly suggests that, contrary to the above postulate, V-T reconversion of V HFs can indeed occur even in long-standing male pattern AGA, at least in this in vivo model, and that both MXL and PRP promote V-T reconversion. Yet, our limited pilot data also suggest that, as expected, intermediate HFs may be more reconversion-responsive than fully miniaturized V HFs, thus recommending early therapeutic intervention in AGA management.

ESDR561 - Vellus-to-terminal hair follicle reconversion does occur in male pattern balding in a new humanized mouse model of androgenetic alopecia and is promoted by minoxidil and PRP

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.