Advances in hair growth

Abstract

Hair is a deeply rooted component of identity and culture. Recent articles in this series have focused on scientific evidence relating to hair growth and new insights into the pathogenesis and mechanism of hair loss. This article reviews emerging evidence that has advanced our understanding of hair growth in both of these areas to provide a context for outlining current and emerging therapies. These include finasteride, minoxidil, topical prostaglandins, natural supplements, microneedling, low-level laser light, platelet-rich plasma, fractional lasers, cellular therapy, Wnt activators and SFRP1 antagonism.

Keywords: Alopecia; androgenetic alopecia; antiandrogens; exosomes; female pattern hair loss; fractional lasers; hair cycling; hair growth; low-level laser light; male pattern hair loss; micro-needling; minoxidil; platelet rich plasma; prostaglandins.

Figure 1.. Miniaturisation of the hair follicle.

In a previous F1000 article, a model of androgenetic alopecia is presented. Through consecutive hair cycles, progressive miniaturisation of the hair follicle unit occurs, initially affecting secondary follicles, associated with hair density reduction, before the arrector pili muscle is replaced by fat. Ultimately, detachment of this muscle from the regenerative bulge area is associated with irreversible hair loss^,. This figure was adapted from Sinclair et al. which is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) (https://creativecommons.org/licenses/by-nc/4.0/).

Figure 2.. Androgenetic alopecia miniaturised follicles.

In androgenetic alopecia, there is a reduction in the number of hairs per follicular unit (white arrow) versus in the normal hair follicular unit (red arrow), where multiple hairs emerge from a single infundibulum. This image was kindly provided by RS from his clinic.