6.      Study of cell senescence in cultured primary balding and non-balding dermal papilla cells.
Adiam W Bahta, Dermatology (QMUL), London, UK

The dermal papilla (DP) expresses androgen receptors and is known to control normal hair growth. The paradox of androgen action in human hair growth is well established but the molecular mechanisms are poorly understood. DP cells derived from frontal (balding) human scalp hair follicles (BDPC) are used to study Androgenetic alopecia. Cultured BDPC are known to have a much slower rate of growth in vitro than DP from non balding sites (NBDPC), however, the cause of this has not been reported. In this study we have investigated the growth of human BDPC and NBDPC in vitro. We observed that BDPC have a limited life span of 2-6 passages. We observed that from passage 2 onwards BDPC but not NBDPC showed a large flattened morphology characteristic of senescent fibroblasts and that once they had assumed this morphology they could no longer be passaged. We showed that these BDPC but not NBDPC of the same passage expressed senescence-associated beta-galactosidase activity at PH-6. Moreover, stress induced premature senescence was induced with more prominent characteristic behaviour in BDPC than NBDPC after exposure to sub-cytotoxic levels of H2O2 a known inducer of oxidative stress. Finally BDPC also expressed a wide range of oxidative stress markers including HSP27, Super Oxide Dismutase and Catalase. These data suggest that the well documented, slower in vitro proliferative rate of BDPC is due in part to premature senescence. Moreover, our observation that cultured BDPC express markers of oxidative stress and their response to H2O2 suggest that oxidative stress may play a major role in male pattern hair loss. Others and we have observed that DHT is able to induce TGF-beta1 in BDPC. TGF-beta1 is known to induce oxidative stress and this may therefore, link androgens with oxidative stress and help explain the paradox of androgen action on hair growth.