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Interferon-gamma is a potent inducer of catagen-like changes in cultured human anagen hair follicles.

BACKGROUND
Interferon (IFN)-gamma appears to be an important hair cycle modulator in mice. It is unclear whether it has similar hair growth modulatory functions in human hair follicles.


OBJECTIVES
To study whether IFN-gamma can be exploited to modulate the growth, pigmentation and/or cycling of organ-cultured human anagen scalp hair follicles, as an in vitro indicator system for how IFN-gamma affects human hair growth in vivo. This was correlated with the hair follicle expression patterns of IFN-gamma receptors alpha and beta. In addition, we wanted to establish a new, simple tool for the rapid experimental induction of catagen in vitro.


METHODS
Normal human scalp hair follicles in the anagen VI stage of the hair cycle were cultured according to the method of Philpott et al., with or without IFN-gamma (50-1000 IU mL(-1)). Hair shaft elongation and pigmentation changes were measured, complemented by quantitative histomorphometry to assess changes in hair follicle cycling (hair cycle score), proliferation (Ki-67), melanogenesis (Masson-Fontana) and apoptosis (TUNEL). IFN-gamma receptors were also localized by immunofluorescence and EnVision technique. As transforming growth factor (TGF)-beta2 is a recognized key inducer of catagen in human hair follicles, TGF-beta2 expression was investigated by tyramide signal amplification and reverse transcription-polymerase chain reaction in anagen hair follicles treated with vehicle (phosphate-buffered saline) or IFN-gamma.


RESULTS
IFN-gamma rapidly inhibited hair elongation in cultured human anagen hair follicles and induced morphological signs of catagen transformation after only 4 days of culture, i.e. faster than with other reported catagen-inducers (e.g. TGF-beta2). Proliferation was inhibited, apoptosis was increased and follicular melanogenesis was switched off in hair bulb keratinocytes treated in situ with IFN-gamma. Anagen hair follicles displayed strong IFN-gamma receptor alpha-like immunoreactivity, while the immunoreactivity for IFN-gamma receptor beta in the hair matrix was only weak. TGF-beta2 immunoreactivity and mRNA transcript levels were enhanced in hair follicles treated with IFN-gamma.


CONCLUSIONS
These data suggest that IFN-gamma is a potent catagen inducer in normal human scalp hair follicles, which express cognate receptors, and show that IFN-gamma administration offers an excellent tool for experimental catagen induction in organ-cultured human hair follicles. This catagen induction probably occurs at least in part via upregulation of the recognized catagen-stimulatory growth factor TGF-beta2.