Department of Pediatric Surgery, Shengjing Hospital, China Medical University, No. 36 Sanhao Street, Heping District, Shenyang 110004, People's Republic of China.
Int J Colorectal Dis. 2011 Jan;26(1):109-16. doi: 10.1007/s00384-010-1034-2. Epub 2010 Aug 5.
The aim of the present analysis is to examine the morphological changes, the spatiotemporal distribution of apoptosis/proliferation in the human embryonic anorectum, to reveal the normal development of human anorectum, and investigate the possible roles of apoptosis/proliferation during anorectal development.
The embryos were sectioned serially and sagittally, stained with hematoxylin and eosin (H & E) between the third and eighth week of gestation, TdT-mediated dUTP-digoxigenin nick end-labeling (TUNEL) and proliferative cell-specific nuclear antigen (PCNA) immunohistochemical staining from the sixth to the eighth week.
From the fourth to the seventh week, with the growth of the mesenchyme around the cloaca, the cloaca was remolded, subsequently, the cloacal membrane (CM) moved perpendicularly then horizontally. The dorsal cloaca gradually descended to the tail groove, the urorectal septum (URS) and the CM approximated; however, the fusion of URS with the dorsal CM was never observed. During the eighth week, the URS shifted ventrally and finally fused with the ventral CM. Moreover, from the sixth to the eighth week, the apoptotic cells were concentrated in the CM, the mesenchyme of terminal rectum, and the dorsal rectum. Meanwhile, the proliferative cells could be observed in the ventral mesenchyme around the cloaca, the CM, the fused tissue between the URS, and the ventral CM.
During the development of human anorectum, it was intriguing to reveal that the URS never fused with the dorsal CM before dorsal CM disintegration, the normal anorectal development may depend on the dorsal cloaca and the dorsal CM; furthermore, the distribution of apoptosis and proliferation in the anorectum and ventral cloacal mesenchyme played a pivotal role in the formation of the anorectum.
本分析旨在研究人胚肛直肠的形态变化及凋亡/增殖的时空分布，揭示人肛直肠的正常发育，并探讨凋亡/增殖在肛直肠发育过程中的可能作用。
胚胎在第 3 至第 8 孕周行连续矢状位切片，第 6 至第 8 孕周行苏木精和伊红（H&E）染色、末端转移酶介导的 dUTP 缺口末端标记（TUNEL）和增殖细胞核抗原（PCNA）免疫组织化学染色。
从第 4 周到第 7 周，随着腔周围间质的生长，腔被重塑，随后腔膜（CM）垂直然后水平移动。背腔逐渐下降到尾沟，尿直肠隔（URS）和 CM 接近；然而，从未观察到 URS 与背 CM 的融合。在第 8 周，URS 向腹侧移位，最终与腹 CM 融合。此外，从第 6 周到第 8 周，凋亡细胞集中在 CM、直肠末端的间质和背直肠。同时，可在腔周围的腹侧间质、CM、URS 和腹 CM 之间的融合组织中观察到增殖细胞。
在人肛直肠发育过程中，有趣的是发现 URS 在背 CM 解体之前从未与背 CM 融合，正常肛直肠发育可能依赖于背腔和背 CM；此外，肛直肠和腹侧腔系膜中凋亡和增殖的分布在肛直肠的形成中起关键作用。
