A chicken model to study the embryology of cloacal exstrophy

Abstract

Background/purpose: The embryology of bladder and cloacal exstrophy is a mystery. Reasons for this are the lack of human embryos showing these malformations as well as the scarcity of appropriate animal models. Here, the authors present cases of cloacal exstrophies found in chick embryos subsequent to the application of suramin and trypan blue. This animal model might facilitate insight into the embryology of cloacal exstrophy.

Methods: Fertilized chicken eggs were incubated at 38 degrees C and 75% humidity. Embryos were treated in ovo on incubation day 3. The egg shell was windowed, and solutions of suramin (stage 13, 2 x 40 microL/0.2%) or trypan blue (stage 14, 2 x 80 microL/0.03%) were injected into the coelomic cavity. The window was closed, and the embryos were reincubated until examination on incubation day 8. Fifty embryos were treated in each group.

Results: Among the surviving embryos, cloacal exstrophy was found in 2 cases in the suramin-treated group (2 of 29, 6.9%) and in 4 cases in the trypan blue-treated group (4 of 20, 20%).

Conclusions: Suramin and trypan blue can induce cloacal exstrophy in chick embryos. The authors now are modifying their experimental protocols to increase the incidence of this malformation. This model might facilitate studies on the morphogenesis of cloacal exstrophy.