Comparison of the acute ultraviolet photoresponse in congenic albino hairless C57 BL /6J mice relative to outbred SKH 1 hairless mice

Hairless albino Crl: SKH 1 ‐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 SKH 1 model suffers from key limitations that are not seen with congenic mouse strains. Inbred and congenic C57 BL /6J mice are commonly utilized for modified genetic mouse models. We compare the acute UV ‐induced photoresponse between outbred SKH 1 mice and an immune competent, hairless, albino C57 BL /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 SKH 1 mice. The skin of both SKH 1 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/m 2 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 SKH 1 mice. Compared with SKH 1 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 SKH 1 mice. Finally, at 72 h post‐ UV , SKH 1 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.