Ultraviolet B irradiation increases the expression of trichohyalin-like 1 protein in human skin xenotransplants

Trichohyalin-like (TCHHL)1 is a member of the fused-type S100 protein family. Its function remains unknown, although it has been reported to be expressed in the basal layer of the normal epidermis. The aim of this study was to investigate the effects of ultraviolet B (UVB) irradiation on the expression of TCHHL1 in human skin xenotransplants. Expression of TCHHL1 mRNA was increased in the UVB-exposed skin 2 days after UVB irradiation. TCHHL1 was immunohistochemically detected in the basal layers after sham irradiation. However, on Day 2 after irradiation, the TCHHL1 signals were spread throughout the basal and spinous layers of the irradiated skin, with increased expression of cytokeratin 14 and a dramatic increase in the number of Ki67-positive cells observed. These results show that TCHHL1 is a novel protein whose expression can be increased by UVB irradiation. In addition, this study experimentally shows that TCHHL1 is expressed in proliferative keratinocytes.