Wnt5a expression in the hindgut of fetal rats with chemically induced anorectal malformations--studies in the ETU rat model.

Wnt5a is involved in the initiating and patterning morphological adaptations of gut. However, its role remained unknown during terminal hindgut development in the normal and anorectal malformation (ARM) rat embryos. This study was designed to investigate the expression pattern of Wnt5a in the terminal hindgut in ARM rat embryos. Ethylenethiourea-induced ARM model was introduced to investigate the expression pattern of Wnt5a during terminal hindgut development using immunohistochemical staining, reverse transcriptase polymerase chain reaction (RT-PCR), and Western blot analysis. Immunostaining revealed that Wnt5a expression showed space-dependent changes in the developing terminal hindgut. On embryonic day 17 (E17) in normal embryos, the Wnt5a protein was initially expressed in the mesenchyme of the terminal hindgut. From E18 to 19, the positive staining cells gradually increased. The expression was detected mainly in the circular muscle and myenteric plexus of hindgut. In the ARM embryos, on E17, the Wnt5a protein was also expressed in the hindgut. However, from E18 to 19, the positive staining cells in the middle hindgut gradually increased but in the terminal hindgut decreased. In Western blot and RT-PCR, time-dependent changes of Wnt5a protein and mRNA expression were remarkable during the terminal hindgut development in normal and ARM embryos. These data implied that the downregulation of Wnt5a at the time of hindgut neuromuscular development might partly be related to the maldevelopment of terminal hindgut in ARM.