Abstract
BACKGROUND:
Caffeine reportedly counteracts the suppression of hair shaft production by testosterone in organ-cultured male human hair follicles (HFs).
OBJECTIVES:
We aimed at investigating the impact of caffeine a) on additional key hair growth parameters, 
on major hairgrowth-regulatory growth factors and c) on male versus female HFs in the presence of testosterone.
METHODS: on major hairgrowth-regulatory growth factors and c) on male versus female HFs in the presence of testosterone.
Microdissected male and female human scalp HFs were treated in serum-free organ culture for 120 h with testosterone alone (0,5 μg/ml) or in combination with caffeine (0.005-0.0005%), and effects on hair shaft elongation, HF cycling (i.e. anagen-catagen transition), hair matrix keratinocyte proliferation and expression of a key catagen inducer, transforming growth factor β2 (TGF-β2), and anagen-prolonging insulin-like growth factor 1 (IGF-1) were evaluated by quantitative (immuno-) histomorphometry. Caffeine effects were further investigated in human outer root sheath keratinocytes (ORSK).
RESULTS:
Caffeine enhanced hair shaft elongation, prolonged anagen duration and stimulated hair matrix keratinocyte proliferation. Female HFs showed higher sensitivity to caffeine compared to male HFs. Caffeine counteracted testosterone-enhanced TGF-β2 protein expression in male HFs. In female HFs, testosterone failed to induce TGF-β2 expression, while caffeine reduced it. In male and female HFs, caffeine enhanced IGF-1 protein expression. In ORSK, caffeine stimulated cell proliferation, inhibited apoptosis/necrosis, up-regulated IGF-1 gene expression and protein secretion, while TGF-β2 protein secretion was down-regulated.
CONCLUSIONS:
This study reveals new growth-promoting effects of caffeine on human hair follicles of both genders at different (molecular, cellular and organ) levels. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
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