Influence of ionizing irradiation on tissue-resident stem cells

简介：方法：将8周龄C57 BL/J6小鼠随机分为对照组（CTR）、10 Gy一次照射组（10 Gy ×1）和5Gy二次照射组（5Gy×2）。脱毛后，照射腹股沟区。结果：照射后1、2、4周，10 Gy ×1组表皮厚度较CTR组和5Gy×2组明显增厚，但表皮角质形成细胞层数无明显增加。5Gy×2和10 Gy ×1照射组1周和2周时真皮毛细血管数较CTR组少。4周时，CTR组真皮厚度明显大于5Gy×2和10 Gy ×1组。6个月时，5Gy×2组皮下脂肪组织较10 Gy和CTR组薄。3个月和6个月时，5Gy ×2和10 Gy ×1组腹股沟脂肪中毛细血管较CTR组明显减少，脂肪细胞体积变小。许多毛干在1周时消失，随后在3个月时逐渐再生毛发。5 Gy ×2和10 Gy ×1照射组6个月时毛发数量和大小均较CTR组减少，肉眼观察到有灰白色毛发出现。远期（3 ~ 6个月）5Gy×2组的组织损伤一般较10 Gy ×1组严重。这些数据为最大限度地减少短期和长期辐射损伤以及恢复辐射缺血和纤维组织提供了临床见解。

Introduction: It remains unclear how ionizing radiation damages healthy skin and hair follicles in a short and long term.Methods: C57BL/J6 mouse (8 weeks old) were distributed to three groups (control: CTR,10Gy once irradiation: 10Gy×1, 5Gy twice irradiations: 5Gy×2). After hair epilation, the groin area was radiated. At 0, 1, 2, and 4 weeks, 3, 6 months after irradiation, the skin samples were evaluated histologically and macroscopically.Results: At 1, 2, and 4 weeks, the epidermis was thicker in 10Gy×1 than CTR and 5Gy×2,without increasing the layer number of epidermal keratinocytes. The number of capillaries in dermis was fewer in 5Gy×2 and 10Gy×1 than CTR at 1 and 2 weeks. At 4 weeks, the the dermis was thicker in CTR than 5Gy×2 and 10Gy×1. At 6 months, the subcutaneous fat tissue was thinner in 5Gy×2 than 10Gy and CTR. At 3 and 6 months, capillaries in groin fat of5Gy×2 and 10Gy×1 appeared to be fewer than thoes of CTR and the size of adipocytes became smaller in 5Gy×2. Many of hair shafts disappeared at 1 week, followed by gradual regrow of hairs by 3 months. The number and size of hair remained decreased in 5Gy×2 and 10Gy×1 than CTR at 6 months when hairs were restored and the gray hairs were macroscopically observed.Discussions/Conclusions: In short term (1 to 4 weeks), the number of hair follicles andcapillaries decreased and the dermis became thinner because of acute radiation injury. In long term (3 to 6 months), tissue damage was generally more severe in 5Gy×2 than 10Gy×1. These data provide clinical insights for minimizing short and long term radiation injuryand revitalizing the radiated ischemic and fibrous tissue.