Iwanaga T
Department of Anatomy, Hokkaido University Faculty of Veterinary Medicine, Sapporo, Japan.
Arch Histol Cytol. 1995 Jun;58(2):151-9. doi: 10.1679/aohc.58.151.
Epithelial cells of the gut are characterized by rapid, constant cell renewal. The death of epithelial cells at the villus tips occurs so regularly that it must be regarded as a well-controlled cell death, designated as apoptosis. However, only limited information has been available on the mechanism of this phenomenon, including the disposal of the effete cells. In the small intestine of the guinea pig and monkey, macrophages are densely aggregated at the lamina propria of the villus tips and vigorously engaged in the phagocytosis of effete epithelial cells. Intraepithelial lymphocytes possessing cytoplasmic granules, possibly intense in cytotoxicity, are topographically associated with the dying enterocytes, suggesting lymphocyte-mediated killing. After the engulfing of apoptotic enterocytes is left within the epithelium, maintaining the epithelial barrier until it is pinched off by the pushing of surrounding enterocytes. In the rat and mouse, on the other hand, effete enterocytes are exfoliated as a whole from the villus tips into the gut lumen. Macrophages, also numerous at the villus tips in these species, are less intense in phagocytotic activity. At the shoulder region of the villus, subepithelial macrophages extend thick processes deep into the epithelium; the processes appear to push out some enterocytes with typical apoptotic signs into the gut lumen. Lamina propria macrophages in the rat and mouse do not engulf enterocytes, but are believed to be involved in the induction of their apoptosis. The species difference in the mechanism of the apoptosis of enterocytes provides clues for understanding apoptosis.
肠道上皮细胞的特点是细胞更新迅速且持续不断。绒毛顶端上皮细胞的死亡如此有规律，以至于必须将其视为一种受到良好控制的细胞死亡，即凋亡。然而，关于这一现象的机制，包括衰老细胞的处理，目前可用的信息有限。在豚鼠和猴子的小肠中，巨噬细胞密集聚集在绒毛顶端的固有层，并积极参与衰老上皮细胞的吞噬作用。具有细胞质颗粒、可能具有强烈细胞毒性的上皮内淋巴细胞在地形上与即将死亡的肠细胞相关，提示淋巴细胞介导的杀伤作用。凋亡肠细胞被吞噬后留在上皮内，维持上皮屏障，直到被周围肠细胞的推挤而被掐断。另一方面，在大鼠和小鼠中，衰老的肠细胞作为一个整体从绒毛顶端脱落到肠腔中。巨噬细胞在这些物种的绒毛顶端也很多，但吞噬活性较低。在绒毛的肩部区域，上皮下巨噬细胞伸出粗大的突起深入上皮；这些突起似乎将一些具有典型凋亡迹象的肠细胞推出到肠腔中。大鼠和小鼠固有层中的巨噬细胞不吞噬肠细胞，但被认为参与诱导其凋亡。肠细胞凋亡机制的物种差异为理解凋亡提供了线索。
