51.    Caffeine counteracts the growth inhibitory effect of testosterone in ex vivo human hair follicles from male patients with AGA.
T.W. Fischer(1&2), U.C. Hipler(1), P. Elsner(1) 1.Department of Dermatology and Allergology, Friedrich-Schiller-University, Jena, Germany 2.Department of Dermatology and Venerology, University Hospital Schleswig-Holstein, University of Lübeck, Lübeck, Germany.

Androgenetic alopecia (AGA) is a common problem in men of all ages, starting at the age of 20 and affecting about 50% at the age of 50. The underlying cause is an androgen-dependent miniaturization of genetically predetermined hair follicles, modulated by dihydrotestosterone (DHT) and the expression of androgen receptor (AR). Here, we used ex vivo hair follicles from balding areas of men with AGA and cultivated them in vitro to investigate the effects of testosterone and caffeine, the latter being a promising candidate for hair growth stimulation. Hair follicles from 14 biopsies, taken from the vertex areas from male AGA patients, were cultivated for 120-192h in the presence of normal William's E medium (control) or William's E medium containing different concentrations of testosterone and/or caffeine. The outcome parameters were hair shaft elongation and keratinocyte proliferation assessed by Ki-67 staining of longitudinal hair follicle cryosections. Testosterone which is metabolized by intrafollicular 5-ex-reductase to DHT lead to significant growth suppression at the concentration of 5 ug/ml.This suppression was neutralized by caffeine in concentrations of 0.001 and 0.005%. Moreover, caffeine alone lead to a significant stimulation of hair follicle growth compared to normal medium. The results were confirmed by proliferation assessment with Ki-67 staining. Androgen-dependent growth inhibition of ex vivo hair follicles from patients suffering from AGA was present in the human hair organ culture model. This model imitates the clinical situation ofAGA in vitro and may serve for future studies to screen new substances against androgen-dependent hair loss. Caffeine counteracted the inhibitory effect of testosterone and was identified as a stimulator of human hair growth in vitro, a fact which may have important impact on clinical management of AGA.