Comparison of the acute ultraviolet photoresponse in congenic albino hairless C57BL/6J mice relative to outbred SKH1 hairless mice

Hairless albino Crl:SKH1‐Hr^hr mice are commonly utilized for studies in which hair or pigmentation would introduce an impediment to observational studies. Being an outbred strain, the SKH1 model suffers from key limitations that are not seen with congenic mouse strains. Inbred and congenic C57BL/6J mice are commonly utilized for modified genetic mouse models. We compare the acute UV‐induced photoresponse between outbred SKH1 mice and an immune competent, hairless, albino C57BL/6J congenic mouse line B6.Cg‐Tyr^c?2J Hr^hr/J]. Histologically, B6.Cg‐Tyr^c?2J Hr^hr/J skin is indistinguishable from that of SKH1 mice. The skin of both SKH1 and B6.Cg‐Tyr^c?2J Hr^hr/J mice exhibited a reduction in hypodermal adipose tissue, the presence of utricles and dermal cystic structures, the presence of dermal granulomas and epidermal thickening. In response to a single 1500 J/m² ultraviolet B dose, the oedema and apoptotic responses were equivalent in both mouse strains. However, B6.Cg‐Tyr^c?2J Hr^hr/J mice exhibited a more robust delayed sunburn reaction, with an increase in epidermal erosion, scab formation and myeloperoxidase activity relative to SKH1 mice. Compared with SKH1 mice, B6.Cg‐Tyr^c?2J Hr^hr/J also exhibited an aberrant proliferative response to this single UV exposure. Epidermal Ki67 immunopositivity was significantly suppressed in B6.Cg‐Tyr^c?2J Hr^hr/J mice at 24 h post‐UV. A smaller non‐significant reduction in Ki67 labelling was observed in SKH1 mice. Finally, at 72 h post‐UV, SKH1 mice, but not B6.Cg‐Tyr^c?2J Hr^hr/J mice, exhibited a significant increase in Ki67 immunolabelling relative to non‐irradiated controls. Thus, B6.Cg‐Tyr^c?2J Hr^hr/J mice are suitable for photobiology experiments.