HAIR FOLLICLE EXPRESSION OF 1,25-DIHYDROXYVITAMIN D-3 RECEPTORS DURING THE MURINE HAIR CYCLE

Because the hair follicle is a highly hormone-sensitive miniorgan, the role of hormones produced locally in the skin in the control of hair growth deserves systematic analysis. It has been shown previously that the potent steroid hormone 1,25-dihydroxyvitamin D-3 (1,25-D-3) modul ates growth and differentiation of keratinocytes via binding to a high -affinity nuclear vitamin D receptor (VDR). In this study, we have exa mined the in situ expression of VDR during the murine hair cycle. VDR expression was detected immunohistochemically. To obtain defined stage s of the murine hair cycle, hair growth was induced by depilation in C 57 BL-6 mice. In addition to the recognized VDR expression of outer ro ot sheath keratinocytes, we detected VDR immunoreactive cells in the d ermal papilla, the mesenchymal key structure of the hair follicle. Fur thermore, VDR immunoreactivity in the nuclei of outer root sheath kera tinocytes and in dermal papilla cells was stronger during anagen IV-VI and catagen than during telogen and anagen I-III. This suggests hair cycle-associated changes in the expression of VDR, and points to a pot ential role for 1,25-D-3 in hair follicle biology. Selected follicular cell populations may display hair cycle-dependent sensitivity to 1,25 -D-3 stimulation.