Human scalp hair follicles (HFs) are a major non-classical site of neurohormone production. While we had previously shown that growth hormone (GH), unexpectedly, inhibits female human scalp HFs growth ex vivo, it is unknown whether human HFs also produce key HPS axis neurohormones themselves, i.e. GH, its upstream regulator, GHRH, and/or the negative feedback control, somatostatin (SST), and whether GHRH modulates hair growth. To answer these questions, human scalp HFs were organ-cultured and stimulated with human GH (100 or 300ng/mL), GHRH (100 or 300ng/mL), or vehicle for mRNA or protein analysis of key HPS axis elements. This revealed HF expression of both, GHRH and GH receptor protein as well as of their cognate ligands. Moreover, GHRH stimulation significantly upregulated both GH and SST protein and mRNA expression in the hair matrix and outer root sheath (ORS) keratinocytes ex vivo. After treatment with GHRH for 6 days, test HFs remained significantly longer in anagen than vehicle-treated HFs and showed increased IGF-1 protein expression in the ORS. GH stimulation significantly downregulated GH and GHRH mRNA and protein expression, and upregulated SST, exhibiting negative feedback control of these hormones. Taken together, this introduces GHRH as a novel endogenous modulator of human hair growth and demonstrates that human scalp HFs operate a fully functional peripheral equivalent of the central HPS neuroendocrine signaling axis. Since insufficient/excessive GH serum levels can cause hair growth abnormalities, this newly identified neuroendocrine system in human skin is clinically relevant and invites novel hair growth intervention strategies that target peripheral HPS hormones or their receptors.

ESDR562 - Neuroendocrinology of human scalp hair follicles: Growth hormone-releasing hormone (GHRH) stimulates hair growth and controls a fully functional intrafollicular hypothalamic-pituitary-somatotropic (HPS) signaling axis

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.