Bar-Dayan Y, Afek A, Bar-Dayan Y, Goldberg I, Kopolovic J
Department of Medicine B, Sheba Medical Center, Tel-Hashomer, Israel.
Tissue Cell. 1999 Aug;31(4):391-6. doi: 10.1054/tice.1999.0001.
The thymus reaches its maximal size at the age of 1 month in ICR mice and thereafter, the thymic cortex undergoes an exponential decline. This study was designed to compare the proliferation and apoptosis of thymocytes in different parts of the thymus of ICR female mice at the beginning and after the rapid phase of decline of the thymic cortical cellularity. The pattern of proliferation and apoptosis of the thymus was studied in situ in 1-month-old ICR female mice (10 mice) compared to mice at 7 months of age (10 mice). Staining for argyrophylic nucleolar organizer region by histochemistry was used to determine the proportion of type 2 thymocytes, which are considered as cells at S phase of the cell cycle. The mean number of type 2 cells in four random samples of 50 cells in each part of the thymus was defined as the proliferation index of this part of the thymus. In situ detection of apoptosis of thymocytes was carried out using the Apoptag kit, which can detect a single cell apoptosis. The mean number of apoptotic cells in five randomly selected fields of each part of the thymus was defined as the apoptotic index of this part of the thymus. The proliferation index of the peripheral cortex of the 1-month-old mice was 3.6 times higher than the proliferation index of the deep cortex and 5.8 times higher than the proliferation index of the medulla (P < 0.0001). The proliferation index of the peripheral cortex of the 7-month-old mice was reduced by 45% compared to the 1-month-old mice (P < 0.005). The apoptotic index of the corticomedullary junction of the 1-month-old mice was six times higher than the apoptotic index of the cortex and 18 times higher than the apoptotic index of the medulla. The apoptotic index of the thymic cortex was elevated by 66% in the 7-month-old mice compared to the 1-month-old mice (P < 0.0001). We conclude that there is a reduction of the proliferation index and an elevation of the apoptotic index of the thymic cortex in adult mice compared to young mice. These changes might account for the reduction of thymic cortical cellularity during thymic involution.
在ICR小鼠中，胸腺在1月龄时达到最大尺寸，此后，胸腺皮质呈指数级衰退。本研究旨在比较ICR雌性小鼠胸腺皮质细胞数量快速下降期开始时和之后，胸腺不同部位胸腺细胞的增殖和凋亡情况。研究了1月龄ICR雌性小鼠（10只）与7月龄小鼠（10只）胸腺增殖和凋亡的原位模式。采用组织化学方法对嗜银核仁组织区进行染色，以确定2型胸腺细胞的比例，2型胸腺细胞被认为是处于细胞周期S期的细胞。胸腺各部分50个细胞的四个随机样本中2型细胞的平均数量被定义为该部分胸腺的增殖指数。使用Apoptag试剂盒对胸腺细胞凋亡进行原位检测，该试剂盒可检测单细胞凋亡。胸腺各部分五个随机选择视野中凋亡细胞的平均数量被定义为该部分胸腺的凋亡指数。1月龄小鼠外周皮质的增殖指数比深层皮质的增殖指数高3.6倍，比髓质的增殖指数高5.8倍（P < 0.0001）。与1月龄小鼠相比，7月龄小鼠外周皮质的增殖指数降低了45%（P < 0.005）。1月龄小鼠皮质髓质交界处的凋亡指数比皮质的凋亡指数高6倍，比髓质的凋亡指数高18倍。与1月龄小鼠相比，7月龄小鼠胸腺皮质的凋亡指数升高了66%（P < 0.0001）。我们得出结论，与年轻小鼠相比，成年小鼠胸腺皮质的增殖指数降低，凋亡指数升高。这些变化可能解释了胸腺退化过程中胸腺皮质细胞数量的减少。
