J Vet Sci.  2015 Mar;16(1):1-9. 10.4142/jvs.2015.16.1.1.

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

• Kim JS
• Rhim KJ
• Jang WS
• Lee SJ
• Son Y
• Lee SS
• Park S
• Lim SM

• KMID: 2160814
• DOI: http://doi.org/10.4142/jvs.2015.16.1.1

Abstract

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 166Ho patches. Clinicopathological and immunohistochemical changes in exposed skin were monitored for 18 weeks after beta-irradiation. Radiation induced desquamation at 2~4 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 6~8 weeks after irradiation. Epidermal expression of nuclear factor-kappa B (NF-kappaB) 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 full depth of the skin 4 weeks after irradiation. These findings suggest that NF-kappaB and COX-2 play roles in epidermal cell regeneration following beta-irradiation of mini-pig skin.

Keyword

beta-ray; irradiation; pig; skin

MeSH Terms

Animals
Cyclooxygenase 2/genetics/*metabolism
*Holmium
Male
NF-kappa B/genetics/*metabolism
Radiation Injuries, Experimental/metabolism/*veterinary
Skin/metabolism/*radiation effects
Swine
Swine, Miniature
Cyclooxygenase 2
Holmium
NF-kappa B

Figure

• 

  Fig. 1 β-irradiation exposure using 166Ho patches to induce mini-pig dorsal skin lesions. (A) The 166Ho patch. (B) The 166Ho patch applied to dorsal skin of a mini-pig. (C) β-irradiated lesions (caused by 50 or 100 Gy) with the separate observation fields and punch biopsy sites. a; sequential biopsy, b; observation.

• 

  Fig. 2 Time-dependent changes in skin gross morphology of a mini-pig after treatment with either 50 or 100 Gy of β-irradiation delivered by a 166Ho skin patch. (A) Two weeks after β-irradiation (50 Gy). (B) Four weeks after irradiation (50 Gy). (C) Eight weeks after irradiation (50 Gy). (D) Fourteen weeks after irradiation (50 Gy). (E) Two weeks after irradiation (100 Gy). (F) Four weeks after irradiation (100 Gy). (G) Eight weeks after irradiation (100 Gy). (H) Fourteen weeks after irradiation (100 Gy). (I) The dose- and time-dependent gross morphological changes of pig skin after application of a 166Ho skin patch (50 or 100 Gy). Data are expressed as the mean ± SEM. *p < 0.05 vs. the sham controls. Scale bar = 1 cm.

• 

  Fig. 3 Histological changes in mini-pig skin after 50 or 100 Gy of β-irradiation delivered by a 166Ho skin patch. (A) Before exposure to irradiation. (B) Two weeks after β-irradiation (50 Gy). (C) Four weeks after irradiation (50 Gy). (D) Eight weeks after irradiation (50 Gy). (E) Fourteen weeks after irradiation (50 Gy). (F) Two weeks after β-irradiation (100 Gy). (G) Four weeks after irradiation (100 Gy). (H) Eight weeks after irradiation (100 Gy). (I) Fourteen weeks after irradiation (100 Gy). (J) Dose- and time-dependent changes in epidermal thickness a mini-pig following β-irradiation (50 or 100 Gy). (K) Dose- and time-dependent changes in basal cell density in mini-pig skin following β-irradiation (50 or 100 Gy). Data are presented as the mean ± SEM. *p < 0.05 vs. the sham controls. (A~I) Hematoxylin and eosin staining; 200× magnification. Scale bar = 100 µm.

• 

  Fig. 4 Time-dependent changes in NF-κB expression after β-irradiation of mini-pig skin (50 or 100 Gy) with a 166Ho patch. (A) No NF-κB expression was observed in the skin before exposure to irradiation. (B) Two weeks after β-irradiation (50 Gy). (C) Intense cytoplasmic NF-κB expression with occasional nuclear staining 4 weeks after irradiation (50 Gy). (D) Strong nuclear expression of NF-κB throughout the hyperplastic epidermis 6 weeks after irradiation (50 Gy). (E) Persistent and strong nuclear expression of NF-κB in the full layers of the hyperplastic epidermis 8 weeks after β-irradiation (50 Gy). (F) Loss of nuclear NF-κB expression 14 weeks after irradiation (50 Gy). (G) NF-κB expression 2 weeks after β-irradiation (100 Gy). (H) Epidermal loss 4 weeks after irradiation (100 Gy). (I) Strong nuclear expression of NF-κB in the full layers of the hyperplastic epidermis 6 weeks after irradiation (100 Gy). (J) Persistent and strong nuclear expression of NF-κB 8 weeks after irradiation (100 Gy). (K) Striking decrease in the expression of nuclear NF-κB scattered in a few cells 14 weeks after irradiation (100 Gy). (L) Dose- and time-dependent changes in NF-κB expression in the epidermis following β-irradiation (50 or 100 Gy). Data are expressed as the mean ± SEM. *p < 0.05 vs. the sham controls. (A~K) Immunohistochemical counterstaining with hematoxylin; 400× magnification. Scale bar = 50 µm.

• 

  Fig. 5 Time-dependent changes in COX-2 expression in mini-pig epidermis following β-irradiation (50 or 100 Gy). (A) No COX-2 expression was observed in the skin before β-irradiation. (B) COX-2 expression in basal cells 2 weeks after β-irradiation (50 Gy). (C) COX-2 expression in full layers of the atrophic epidermis 4 weeks after irradiation (50 Gy). (D) Intermediate levels of COX-2 expression in the basal and spinous layer of the hyperplastic epidermis 6 weeks after irradiation (50 Gy). (E) COX-2-positive staining in the superficial granular layer with no expression in the basal layer 8 weeks after β-irradiation (50 Gy). (F) Almost complete loss of COX-2 expression 14 weeks after irradiation (50 Gy). (G) COX-2 expression in the basal and spinous layers of the atrophic epidermis 2 weeks after β-irradiation (100 Gy). (H) Four weeks after irradiation (100 Gy). (I) Intermediate levels of COX-2 expression in the full layers of the hyperplastic epidermis 6 weeks after irradiation (100 Gy). (J) COX-2 expression in the upper layers but not in the basal layer 8 weeks after irradiation (100 Gy). (K) Loss of COX-2 expression in the basal layer with persistent COX-2 expression seen in the upper layers 14 weeks after irradiation (100 Gy). (A~K) Immunohistochemical counterstaining with hematoxylin; 400× magnification. Scale bar = 50 µm.

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