P2.21 HUMAN HAIR FOLLICLE ORGAN CULTURE AS A SCREENING TOOL FOR “HAIR DRUG” DISCOVERY

A. Mescalchin*, M. Massironi*, A. Bettermann#, R. Paus# and P. Pertile*

* Cutech Srl, Padova, Italy; # Dept. of Dermatology, UKE, Hamburg, Germany

Organ culture of human hair follicles, pioneered by Philpott et al., is still the only reliable in vitro-method for predicting how a test agent might affect human hair growth in vivo. Here, we reconsider this assay and propose modifications for its optimisation. Microdissected human scalp hair follicles in anagen VI are cultured up to 10 days during which time hair shaft elongation proceeds at an in vivo-like rate. In its traditional form, this assay is best-suited for testing candidate hair growth-inhibitors, since anagen VI hair bulbs show already maximal growth and are highly susceptible to inhibitory compounds. Also, this assay imitates only systemic drug administration and is limited in its physiological relevance due to the absence of large portions of the pilosebaceous apparatus. To overcome these limitations, we have modified and optimised the assay, e.g. by enlarging and standardizing the read-out parameters for evaluating the modulatory properties of a candidate "hair drug". Besides hair shaft elongation, proliferation and apoptosis of hair matrix cells, hair cycle stage, hair pigmentation (melanin quantity/distribution and melanocyte detection) and indications of compound toxicity (signs of follicle dystrophy) are assessed. This allows highly instructive test compound screening for its effects on spontaneous catagen development, "physiological" catagen development (induced by TGF-beta2), premature "pathological" (i.e. inflammation-associated) catagen development (induced by IFN-gamma). In parallel, we have applied strict parameters for quality control of organ-cultured hair follicles and included automated measurements by customized digital analysis software. These modifications greatly enhance the instructiveness, sensitivity and predictive value of this assay as a screening tool for candidate hair growth and/or hair pigmentation-modulatory molecules, while simultaneously offering indications of a test compound's potential toxicity in the human system.