Influence of ionizing irradiation on tissue-resident stem cells

前言：电离辐射对健康皮肤和毛囊的短期和长期损伤尚不清楚。方法：8周龄C57BL/J6小鼠随机分为3组(对照组：CTR组，10Gy1次照射组，10Gy2次照射组，5Gy2次照射组，5Gy2次照射组)。脱毛后，对腹股沟区域进行照射。结果：照射后1周、2周、4周、3个月、6个月时，照射后1、2、4周的皮肤组织学观察及肉眼观察结果显示，照射后1、2、4周，照射组大鼠皮肤表层较CTR组和5Gy2组增厚，表皮角质形成细胞层数未见增加。照射后1周和2周，5Gy2和10Gy1次照射组真皮毛细血管数明显少于CTR组。4周时，CTR组真皮厚度大于5Gy2和10Gy×1；6个月时，5Gy2组皮下脂肪组织厚度小于10Gy组和10Gy组。3个月和6个月时，5Gy2和10Gy1组腹股沟脂肪中的毛细血管明显少于CTR组，5Gy2组脂肪细胞体积变小，1周时许多毛干消失，3个月后毛发逐渐再生。6个月后恢复毛发，大体观察到白发，5Gy2和10Gy1组的毛发数量和大小仍比CTR组减少。在长期内(3~6个月)，5Gy2的组织损伤一般比10Gy1的组织损伤更严重。这些数据为减少短期和长期的辐射损伤，恢复受辐射的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.