A novel mechanism on disposing of effete enterocytes

1.豚鼠小肠上皮细胞是细胞体的主要部分，由固有层巨噬细胞吞噬。然而，在细胞凋亡事件发生后，顶端细胞质仍留在上皮内。结论：1.本研究结果表明，皮肤样的顶端细胞质通过连接复合体与相邻的肠上皮细胞相连，保留了上皮屏障。由于相邻细胞的关闭，具有刷状边缘的顶端细胞质突出到管腔内，当相邻细胞接触时，顶端细胞质被挤压到管腔内。在这个过程中，没有任何可辨认的上皮小孔。此后，肠腔内可见大量胞质碎片，边缘呈刷状。在大鼠的肠腔内，肠腔内含有大量有核的凋亡肠细胞胞体，提示整个胞体脱落进入肠腔。在猴子和马中发现了豚鼠猪型机制，而在小鼠中也发现了鼠型机制。人类基本上被归为后一种类型。肠细胞的细胞死亡可能不是单纯的程序性细胞死亡，而是容易受到外界因素的诱导。豚鼠上皮内淋巴细胞参与诱导细胞凋亡，而大鼠固有层巨噬细胞参与这一机制。

1. Effete epithelial cells in the small intestine of the guinea pig, major parts of cell bodies, are phagocytosed by lamina propria macrophages. However, the apical cytoplasm remain within the epithe lium after the apoptotic event. The present study demonstrated that the skin-like apical cytoplasm is connected with adjacent enterocytes by junctional complexes, still keeping the epithelial barrier.2. The apical cytoplasm with the brush border is protruded into the luminal space due to closing of adjacent cells, and pinched off into the lumen when the adjacent cells contacted. During the process, no holes of the epithelium were recognizable. Thereafter, there were numerous cytoplasmic fragments with the brush border in the lumen of intestine.3. In the rat, the intestinal lumen contained numerous cell bodies of apoptotic enterocytes with nuclei, suggesting exfoliation of whole cell bodies into the lumen.4. The guines pig-type mechanism on disposing of effete epithelial cells was recognized in the monkey and horse, while the rat-type mechanism was shared by the mouse. Humans were basically classified into the latter type.5. Cell death of enterocytes may not be soley programd cell death, but easily induced by external factors. Intraepithelial lymphocytes are involved in the induction of apoptosis in the guinea pig, while in the rat lamina propria macrophages participate in this mechanism.