Estrogen receptor alpha, but not estrogen receptor beta, is involved in the regulation of the hair follicle cycling as well as the thickness of epidermis in male mice.

Estrogen is of importance for the regulation of hair growth and epidermal thickness. The effects of estrogen have predominantly been studied in females; however, recent studies demonstrate that estrogen also is critical for males. The aim of this study was to investigate the relative functional importance of estrogen receptor alpha and estrogen receptor beta in the regulation of the hair follicle cycling and epidermal thickness in male mice. Seven month old transgenic male mice, lacking estrogen receptor alpha (ERKO), estrogen receptor beta (BERKO), or both receptors (DERKO), were orchidectomized and treated for 3 week with 17beta-estradiol or vehicle. Orchidectomy induced a synchronized anagen phase of the hair follicles, which was inhibited by 17beta-estradiol treatment in wild-type and BERKO mice, but not in ERKO and DERKO mice. Furthermore, 17beta-estradiol treatment increased the thickness of epidermis in wild-type and BERKO mice, but not in ERKO and DERKO. This study demonstrates that estrogen is of importance for the regulation of hair follicle cycling and epidermal thickness in male mice. The effect on hair follicle cycling is caused by an estrogen receptor alpha mediated inhibition of telogen-anagen transition and the effect of estrogen to increase epidermal thickness is associated with an estrogen receptor alpha mediated increase in the proliferative rate of the keratinocytes in the basal cell layer of the epidermis.