糖皮质激素诱导小鼠胸腺细胞死亡的形态学改变

目的 探讨糖皮质激素诱导小鼠胸腺细胞死亡的形态学改变. 方法 4～6周龄雌性BALB/C小鼠腹腔注射地塞米松,采用末端转移酶介导的dUTP缺口末端标记(TUNEL)法检测DNA单链或双链的裂解,TUNEL和酸性磷酸酶(ACP)双重染色法进行酸性磷酸酶的检测,观察细胞凋亡后吞噬细胞的活动,透射电子显微镜检测凋亡细胞和吞噬细胞的超微结构.结果 光镜观察地塞米松组,TUNEL阳性细胞较多并且分散在皮质各处,凋亡指数为0.460±0.012;正常对照组TUNEL阳性细胞数目较少,凋亡指数为0.020±0.001,与地塞米松组比较,差异有显著性(P<0.05).TUNEL和酸性磷酸酶双重染色法显示,所有TUNEL阳性胸腺细胞均被ACP阳性细胞吞噬.透射电子显微镜观察发现,大部分凋亡细胞均被吞噬细胞所吞噬,少量未被吞噬的胸腺细胞表现出大范围的染色质浓集,这些少量未被吞噬的胸腺细胞显然是死细胞. 结论 典型的细胞凋亡的特点是DNA裂解,但这不是糖皮质激素诱导胸腺细胞死亡的主要方式,死亡的胸腺细胞均是被ACP阳性细胞所吞噬;糖皮质激素对胸腺细胞的首要影响是可诱导无DNA裂解的细胞固缩.

Study on the cell morphology of glucocorticoid-induced murine thymocyte death

Objective To study cell morphological change of glucocorticoid(GC) induced murine thymocyte death. Method After intraperitoneal injection of dexamethasone into 4-6-week-old female BALB/C mice, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end-labeling (TUNEL) method was used to detect the DNA fragmentation or double strand breaks. To examine acid phosphatase (ACP), we applied double staining of the section with the TUNEL method and ACP. Moreover, we used transmission electron microscopy to observe ultrastructure of apoptosis cells and macrophages as well as the activity of macrophages after apoptosis. Results We demonstrated under light microscopy that, the TUNEL positive thymocytes were scattered throughout the cortex of GC-treated thymus, and the apoptosis index was 0.460±0.012;In the control group, the TUNEL positive ones were few and the apoptosis index was 0.020±0.001. There was significant difference between the two groups(EM>P/EM><0.05). Double staining revealed that all the TUNEL positive cells were phagocytosed by ACP positive macrophages. It was also observed by transmission electron microscopy, and these small unphagocytosed thymocytes were apparently dead cells, as based on the extent of chromatin condensation was enormous. Conclusion Typical apoptosis, which is characterized by DNA fragmentation, was not the dominant type of GC-induced murine thymocyte death. These dead thymocytes were phagocytosed by ACP positive cells.The most important effect of GC for thymocyte was that it can induce chromatin pycnosis without DNA fra