Establishment of a mouse model of melasma using simple ultraviolet irradiation
10.3760/cma.j.cn114453-20231228-00277
- VernacularTitle:单纯紫外线照射法建立黄褐斑小鼠模型研究
- Author:
Liying LI
1
;
Jinghan SUN
;
Cheng HUA
;
Zhenyu CHEN
;
Lele LYU
;
Xian DU
Author Information
1. 青岛大学附属医院美容整形外科，青岛 266003
- Keywords:
Sunburn;
Melasma;
Animal models;
Ultraviolet irradiation
- From:
Chinese Journal of Plastic Surgery
2024;40(4):444-454
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To determine the optimal irradiation energy and frequency for the establishment of melasma mouse model using simple ultraviolet irradiation, and to provide guidance on animal strains and irradiation protocols for the successful establishment of melasma model.Methods:Animal models of melasma were established using BALB/c female mice and C57BL/6JNifdc female mice. BALB/c female mice were divided into 4 groups using a simple randomization method: A, B, C and G, with 5 mice in each group. C57BL/6JNifdc female mice were divided into 4 groups: D, E, F and H, with 5 mice in each group. All mice were irradiated with 8.428 mW/cm 2 of ultraviolet light. The irradiation time was 15 s (single irradiation energy of 0.13 J/cm 2) in groups A and D, 15 min (single irradiation energy of 7.59 J/cm 2) in groups B and E, and 30 min (single irradiation energy of 15.17 J/cm 2) in groups C and F. Each cycle consisted of 5 consecutive days of irradiation followed by 2 days of cessation, totaling 4 cycles of irradiation. Groups G and H were not irradiated. At the end of irradiation, all mice were kept under normal conditions. One week later, 3 mice from each group were selected for HE, Masson-Fontana, Masson, and immunohistochemical staining. Quantitative analysis was performed to measure the thickness of the acanthocyte layer, melanin granules, collagen percentage, and interleukin-1 (IL-1) levels. The remaining mice were kept for an additional week, depilated and photographed to observe the changes in coloration. Data were analyzed using SPSS 27.0 software, measurement data that did not conform to normal distribution were represented by M( Q1, Q3) and comparisons between groups were made using the Kruskal-Wallis rank sum test. Results:During the entire irradiation process, no visible discoloration was observed in the BALB/c female mice in all groups. In contrast, varying sizes of discoloration appeared in the C57BL/6JNifdc female mice in groups D, E, and F after irradiation in the second week. However, by the third week, the discoloration in group D gradually disappeared, while the discoloration in group E was more obvious than before. At the same time, group F exhibited significant discoloration, with some mice exhibited signs of skin peeling, burning and breakage on their backs. After the 4th week of irradiation, no new discoloration was formed in group D. The discoloration was more obvious in group E, and most mice in group F showed skin burn breakage. Two weeks after the completion of irradiation, there was no obvious discoloration on the dorsal skin of BALB/c female mice in all groups. In C57BL/6JNifdc female mice, group D showed no obvious discoloration, group E exhibited lighter discoloration compared to the 4th week post-irradiation, and group F had crusted skin at the burn sites with lighter discoloration than before. However, the discoloration in groups E and F was still obviously visible to the naked eye. HE staining showed that the difference in the thickness of the echinocyte layer was not statistically significant in groups A, B, C, and G ( H=1.08, P=0.782); whereas the difference was statistically significant in groups D, E, F and H ( H=12.85, P=0.005). The thickness of the echinocyte layer decreased gradually with the extension of the irradiation time. Additionally, there was a disruption in the arrangement of epidermal spindles in group F, and this situation was not observed in groups D and E. Masson-Fontana staining revealed no significant pigmentation in any of the BALB/c female mice. The difference in melanin granule counts between groups A, B, C, and G was not statistically significant ( H=7.77, P=0.051). In contrast, C57BL/6JNifdc female mice exhibited more noticeable pigmentation in the epidermis and dermis in groups E and F. The difference in melanin particle counts among groups D, E, F and H was statistically significant ( H=17.61, P<0.001), with melanin deposition increasing gradually with the duration of irradiation. Masson staining showed that the difference in collagen percentage between groups A, B, C, and G was not statistically significant ( H=7.26, P=0.064). However, significant disorganization of fibers and a loose structure were observed in groups E and F. The difference in collagen percentage between groups D, E, F, and H was statistically significant ( H=8.65, P=0.034). Immunohistochemical results showed that the difference in IL-1 expression levels between groups A, B, C, and G was statistically significant ( H=17.86, P<0.001); also between groups D, E, F, and H was statistically significant ( H=14.19, P=0.003), suggesting that ultraviolet irradiation stimulated an inflammatory response in the skin of mice. Conclusion:BALB/c female mice are not suitable for melasma models under the frequency and duration of irradiation in this experiment. C57BL/6JNifdc female mice are irradiated with a single irradiation energy dose of 7.59 J/cm 2 five days a week for 4 weeks, which can establish stable animal models of melasma with a specific level of pigmentation that persisted for at least 2 weeks.
