β-irradiation (166Ho patch)-induced skin injury in mini-pigs: effects on NF-κB and COX-2 expression in the skin

In the present study, the detrimental effect of beta-emission on pig skin was evaluated. Skin injury was modeled in mini-pigs by exposing the animals to 50 and 100 Gy of beta-emission delivered by Ho-166 patches. Clinicopathological and immunohistochemical changes in exposed skin were monitored for 18 weeks after beta-irradiation. Radiation induced desquamation at 2 similar to 4 weeks and gradual repair of this damage was evident 6 weeks after irradiation. Changes in basal cell density and skin depth corresponded to clinically relevant changes. Skin thickness began to decrease 1 week after irradiation, and the skin was thinnest 4 weeks after irradiation. Skin thickness increased transiently during recovery from irradiation-induced skin injury, which was evident 6 similar to 8 weeks after irradiation. Epidermal expression of nuclear factor-kappa B (NF-kappa B) differed significantly between the untreated and irradiated areas. One week after irradiation, cyclooxygenase-2 (COX-2) expression was mostly limited to the basal cell layer and scattered among these cells. High levels of COX-2 expression were detected throughout the frill depth of the skin 4 weeks after irradiation. These findings suggest that NF-kappa B and COX-2 play roles in epidermal cell regeneration following beta-irradiation of mini-pig skin.