Trichohyalin-like 1 (TCHHL1) is a recently identified member of the fused-type S100 protein family. Although it has been reported to be expressed in the basal layer of the normal epidermis, the function of TCHHL1 remains unknown. Previous studies demonstrated that UVB irradiation induced epidermal hyperproliferation, alterations in the expression of differentiation markers and drastic modifications in the patterns of epidermal keratins. In the present study, we examined the changes that UVB irradiation caused in the pattern of TCHHL1 expression in human skin xenotransplants. The expression of TCHHL1 mRNA markedly increased in the UVB-exposed skin two days after UVB irradiation in comparison to the sham-irradiated skin. TCHHL1 was immunohistochemically detected only in the basal layers after sham irradiation. In contrast, on day 2 after irradiation, the TCHHL1 signals were spread in both the basal and spinous layers of the irradiated skin. Furthermore, the increased expression of cytokeratin 14 and a dramatic increase in the number of Ki67-positive cells were observed on day 2 after UVB irradiation. On day 7 after irradiation, TCHHL1 signals were still detected in the basal and suprabasal layers; however, the area was reduced in comparison to day 2. The present study demonstrated that the expression of TCHHL1 is enhanced by UVB irradiation and that the expression might be associated with epidermal hyperproliferation. In addition, it suggests that the increased expression of TCHHL1 might be a useful marker of acute UV damage in skin.

The expression of trichohyalin-like 1 protein in human skin xenotransplants is enhanced by ultraviolet B irradiation