Xenopus: An in vivo model for studying skin response to ultraviolet B irradiation

Ultraviolet B (UVB) in sunlight cause skin damage, ranging from wrinkles to photoaging and skin cancer. UVB can affect genomic DNA by creating cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidine (6-4) photoproducts (6-4PPs). These lesions are mainly repaired by the nucleotide excision repair (NER) system and by photolyase enzymes that are activated by blue light. Our main goal was to validate the use of Xenopus laevis as an in vivo model system for investigating the impact of UVB on skin physiology. The mRNA expression levels of xpc and six other genes of the NER system and CPD/6-4PP photolyases were found at all stages of embryonic development and in all adult tissues tested. When examining Xenopus embryos at different time points after UVB irradiation, we observed a gradual decrease in CPD levels and an increased number of apoptotic cells, together with an epidermal thickening and an increased dendricity of melanocytes. We observed a quick removal of CPDs when embryos are exposed to blue light versus in the dark, confirming the efficient activation of photolyases. A decrease in the number of apoptotic cells and an accelerated return to normal proliferation rate was noted in blue light-exposed embryos compared with their control counterparts. Overall, a gradual decrease in CPD levels, detection of apoptotic cells, thickening of epidermis, and increased dendricity of melanocytes, emulate human skin responses to UVB and support Xenopus as an appropriate and alternative model for such studies.

Automated summary

Ultraviolet B (UVB) in sunlight causes skin damage, such as wrinkles, photoaging, and skin cancer. This study investigated the impact of UVB on skin physiology using Xenopus laevis as an in vivo model. The expression levels of genes related to DNA repair and photolyases were found in all stages of embryonic development and adult tissues. UVB irradiation led to decreased CPD levels, increased apoptotic cells, thickening of the epidermis, and increased dendricity of melanocytes in Xenopus embryos. Blue light exposure effectively activated photolyases, resulting in quick CPD removal and decreased apoptotic cells. This study suggests that Xenopus is a suitable alternative model for studying UVB-induced skin responses.