Avian models in teratology and developmental toxicology

Abstract

The avian embryo is a long-standing model for developmental biology research. It also has proven utility for toxicology research both in ovo and in explant culture. Like mammals, avian embryos have an allantois and their developmental pathways are highly conserved with those of mammals, thus avian models have biomedical relevance. Fertile eggs are inexpensive and the embryo develops rapidly, allowing for high-throughput. The chick genome is sequenced and significant molecular resources are available for study, including the ability for genetic manipulation. The absence of a placenta permits the direct study of an agent's embryotoxic effects. Here, we present protocols for using avian embryos in toxicology research, including egg husbandry and hatch, toxicant delivery, and assessment of proliferation, apoptosis, and cardiac structure and function.

Figure 1

(A) A windowed fertile chick egg. An embryo having 3 somites (arrow) is visible atop the yolk and is surrounded by the transparent area pellucida. (B) Same embryo 24hr later, harvested using the filter ring method and transferred to a tissue culture dish. The embryo, now having 18 somites, is centered within a paper ring cut from Whatman #1 filter paper. The outer ring diameter is 15mm and inner opening is 5mm. The nascent extraembryonic vasculature is clearly visible surrounding the embryo proper. (C) In ovo chick embryo having 4 somites (stage 8) viewed dorsally and stained with 30 μl of 0.05% neutral red. Resting on the right neural fold is an AG50W-X8 resin bead (arrow, BioRad) of 100–200 mesh and having a 100–250 micron diameter. We typically use this bead size for chick embryo work.