Feng J M, Wu J S
Department of Histology and Embryology, Beijing Medical University, Beijing 100083, P. R. China.
Shi Yan Sheng Wu Xue Bao. 1998 Mar;31(1):29-39.
In vitro thymus explants culture designed in this paper can mimic the thymic microenvironment as it were in vivo. Theoretically, thymus explants are cut off free from blood stream. So if some developing or developed thymocytes had the inclination to migrate into the periphery, they would only be accumulated in the blood vessels within thymus explants. After 3-day's culture, under transmission electron microscope we observed the migrating thymocytes accumulated in the blood vessels of C57BL/6 mice thymus explants, and these thymocytes were occurring apoptosis at different stage. To our knowledge, this findings offers the first morphological evidence that thymocytes do not necessarily die inside the thymus in situ, and that having acquired the death signals thymocytes can migrate into the blood stream and die quickly outside the thymus. But this is not to say that we deny the intrathymic death hypothesis. On the contrary, we found the number of thymocytes occurring in situ apoptosis on the surfaces of stromal cells is far more than that of migrating into the blood vessels. So, our proposal is that there are two sites for thymocytes apoptosis, some die inside the thymus and the others die outside the thymus.
本文所设计的体外胸腺外植体培养能够模拟胸腺在体内的微环境。从理论上讲，胸腺外植体与血流切断。所以，如果一些正在发育或已发育的胸腺细胞有迁移到外周的倾向，它们只会积聚在胸腺外植体的血管内。培养3天后，在透射电子显微镜下我们观察到迁移的胸腺细胞积聚在C57BL/6小鼠胸腺外植体的血管中，并且这些胸腺细胞正处于不同阶段的凋亡过程中。据我们所知，这一发现提供了首个形态学证据，表明胸腺细胞不一定在胸腺内原位死亡，并且在获得死亡信号后，胸腺细胞可以迁移到血流中并在胸腺外迅速死亡。但这并不是说我们否定胸腺内死亡假说。相反，我们发现基质细胞表面原位凋亡的胸腺细胞数量远远多于迁移到血管中的数量。所以，我们的提议是胸腺细胞凋亡有两个位点，一些在胸腺内死亡，另一些在胸腺外死亡。
