The expression of Hoxd-13 in anorectum of rats with anorectal malformations

Objective To investigate the expression of Hoxd-13 in the development of anorectal malformations(ARMs) in Ethylenethiourea(ETU)-treated rat embryos, and try to explore its role in the morphogenesis of ARMs. Methods Rat embryos were divided into the ARMs group (n = 75) and control group (n = 108). The ETU routine model of ARMs was employed. The embryos were taken out and made into median sagittal plane sections on E13, E14, E15, E16, E18 and E21. Temporal-spatial study was carried out to detect Hoxd-13 expression by immunohistochemical assay and RT-PCR. Results In immunohistochemical staining, Hoxd-13 expression was confined to the mesen-chyme of the urorectal septum (URS) and the epithelia of the hindgut, cloaca membrane and urogeni-tal sinus in the control group. The mean optical density of Hoxd-13 in the mesenchyme of URS and the epithelium of the hindgut, cloaca membrane or fistula membrane was significantly lower in the ARMs group than that in the control group on E13-16 (P<0.05). RT-PCR amplification showed that Hoxd-13 gene was weak positive or negative in ARMs group, while positive in the control group. The amount of Hoxd-13 mRNA in the embryos with ARMs was significantly lower than that in the control group on E13-16 (P<0.05). The RT-PCR results were consistent with the immnohistochemical stai-ning results. Conclusions The decreased expression of Hoxd-13 gene in the mesenchyme of URS and the epithelium of the hindgut, cloaca and urogenital sinus may be related to the development of ARMs. Key words: Hoxd-13 gene; Anus,abnormalities; Rectum,abnormalities;  Embryology;  Cloaca