L8.      Dihydrotestosterone (DHT)-inducible DICKKOPF 1 from scalp dermal papilla cells causes apoptosis in follicular keratinocytes.
Young-Kwar Sung, Mi-Hee Kwack, Moon-Kyu Kim, Jung-Chul Kim; Department of Immunology, School of Medicine, Kyungpook National University, Daegu, Korea.

Paracrine factors induced by dihydrotestosteron (DHT) are thought to influence the activity of the follicular cells. RT-PCR analysis and ELISA showed that DICKKOPF 1 (DKK-1) is up-regulated and secreted to conditioned media upon DHT exposure. In addition, in vitro co-culture system by using dermal papilla cells (DPCs) and outer root sheath keratinocytes (ORS) showed that DHT inhibits ORS growth and neutralizing antibody against DKK-1 significantly attenuates DHT-induced growth inhibition of ORS cells. Flow cytometry analysis showed DHT induces substantial apoptosis in co-cultured ORS and caspase inhibitor attenuates DHT-induced growth inhibition of ORS. Altogether, this study shows that secreted DKK-1 from DPCs by DHT causes apoptosis in keratinocytes and suggests that DHT-inducible DKK-1 is responsible for the hair growth inhibition.