Study on the spati otemporal distribution of cell apoptosis and proliferation during human embryo development of hindgut,anus and rectum

doi:10.3969/j.issn.1002-7386.2014.23.06

Abstract：Objective To explore the human embryo development process of anorectum,and to investigate initially the effect of cell proliferation/apoptosis during embryo development of anus and rectum.Methods The human embryo specimens (3~9week) were stained by HE,then the morphologic change process of anus and rectum was dynamically observed continuously,and the spatiotemporal distribution regular pattern of cell apoptosis and proliferation was analyzed , combined with the detection results by TUNEL, PCNA immunohistostaining.Results During the 6th week of embryo development,apoptosis cells were located mainly in anus ,rectum,urorectal septum ( URS) and urogenital sinus epithelium, especially a lot of apoptosis cells were located around anus opening area.At the 7th week of embryo development, a great quantity of apoptosis cells were distributed in rectum distal end and rectum dorsal mesenchymal area.During the 8th week, apoptosis cells could be found in rectum and anal tube epithelium,however,few apoptosis cells could be observed in urorectal septum dorsal and cloacal membrane (CM).At the 6th week of embryo development,few proliferation cells could be observed in anus, rectum, urogenital sinus and urorectal septum, and sporadic proliferation cells were located in dorsal cloacal membrane.During the 7th week,proliferation cells were found in urorectal septum mesenchymal,and most cells were located in anus,rectum,urorectal septum ventral mesenchymal.At the 8th week,proliferation cells were distributed mainly in epitheliums of urinary canal,anus and rectum,meanwhile,a lot of proliferation cells aggregated in the fusion area of urorectal septum and ventral cloacal membrane.Conclusion During the embryo development of anorectum, the URS never fuses with dorsal CM before dorsal CM disintegration, the normal anorectal development may depend on the dorsal cloaca and dorsal CM.The distribution of cell apoptosis and proliferation in anorectum and ventral cloacal mesenchyme may play an important role in formation of anorectum.