Vellus-to-terminal hair follicle reconversion is induced by topical minoxidil and platelet rich plasma therapy in the humanized mouse model of male pattern androgenetic alopecia  

In this short communication, recently published in Journal Acta Dermato Venerologica, the authors challenged a current hypothesis claiming that human hair follicles (HFs) cannot reconvert from vellus to terminal states in patients suffering from male pattern Androgenetic Alopecia (mpAGA).

One characteristic feature of mpAGA pathology is the conversion from terminal HFs, forming thick and long hair shafts, as seen on the scalp, to vellus HFs which produce shorter, thinner and lighter coloured hair – a process known as HF miniaturization in specific scalp regions (fronto-temporal, vertex). Drugs and therapies used to treat mpAGA patients, such as minoxidil, finasteride or platelet-rich-plasma (PRP) therapy, prevent hair loss. Yet, whether they also inhibit or reverse terminal-to-vellus HFs conversion remains a matter of debate.

The lead author, Prof. Amos Gilhar, Technion – Israel Institute of Technology, Haifa, Israel – is a long standing collaborator of Monasterium Laboratory GmbH. In this work, the authors employed the humanized mpAGA mouse model, which is also offered by Monasterium, and re-analyzed human mpAGA scalp xenotransplants before and after long-term treatment with minoxidil or PRP1,2 to investigate whether or not the number of vellus HFs declines while that of terminal HFs increases under therapy.

The mpAGA xenotransplants were cut horizontally, and HF diameters were measured and allocated to either terminal, intermediate (a state between terminal and vellus HFs) or vellus HFs, based on objective histomorphometry criteria. Particularly vellus HFs, which were associated with an arrector pili muscle (APM), were analyzed. The APM is thought to be only present in vellus HFs that once were terminal HFs (the ones that underwent miniaturization), while HFs that have always been in the vellus state lack this muscle.

Interestingly, the authors found less vellus HFs with APM, and less intermediate HFs in minoxidil and PRP treated xenotransplants, while the number of terminal HFs was increased. These findings suggest, that a large proportion of vellus HFs did indeed reconvert into terminal HFs under standard mpAGA therapy.

Read the full story here:

1) Laufer Britva et al., Br J Dermatol 2021; 2) Gilhar A et al., Exp Dermatol 2022

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