Whole Embryo Culture: An Important Tool in Developmental Toxicology Today

Abstract

The number of candidate chemicals or drugs for registration and authorization is increasing at a fast rate and only few of the existing substances have been tested for teratogenicity to date. Therefore, there is high pressure on authorities to accept models like the whole embryo culture as a screening system for safety evaluation procedures. In view of this background the gradual development of the whole embryo culture into a standardized, scientifically validated tool for developmental toxicology during the last 70 years is summarized. The methodological development of the culture technique is described with the completion, improvement and refinement of the basic culture method as main intention. Special attention was paid to different culture techniques, culture media, gassing schedules, and evaluation strategies. Furthermore the importance of taking "in vitro pharmacokinetics" into consideration when a comparison of in vitro/in vivo results from embryotoxicity testing is intended, is stressed. Additionally, the demonstration of the broad spectrum of useful scientific applications when using this culture system in combination with sophisticated analytical techniques is demonstrated. Finally, an overview on different strategies for the validation of this culture system as an in vitro embryo toxicity test is provided and the officially accepted formal validation process for this application is summarized. The successful validation makes the whole embryo culture a complex in vitro embryotoxicity test with high accuracy and predictability. This robust in vitro system modelling the main phase of rodent organogenesis with a high reproducibility is valuable enough to attract special attention in related scientific fields.

Morphology‐based mammalian stem cell tests reveal potential developmental toxicity of donepezil

“…In this assay, the embryo is removed from its dam and cultured for 1–2 days to allow developmental progress in vitro (New, ; Ellis‐Hutchings and Carney, ). In developmental toxicology studies, the advantage of whole‐embryo culture over animal‐based tests is that abnormalities in embryos can be directly related to the concentration of the drug being tested, which may then be compared to the serum concentration present in humans (Webster et al, ; Flick and Klug, ). Here, embryos were dissected from euthanized pregnant mice at 8.5 dpc, and cultured for 24 hr with or without 10 µM of donepezil.…”

Identification of a Potent Endothelium-Derived Angiogenic Factor

“…The screening approach using the chorioallantoic membrane of the developing rat embryo [11], [28] showed that the supernatant obtained from HMEC-1 stimulated by shear stress elicited an angiogenic effect in comparison to control ( Figure 1 .A ). Gestational day 9.5 rat embryos were cultured for 48 h. This time period during embryogenesis covers a major part of organogenesis, when a complex vasculature is developed in the yolk sac as well as in the embryo itself.…”

“…After identification and synthesis of Up 4 U, the angiogenic effects of synthetic Up 4 U were verified using the assay whole embryo culture system [11], [28]. Figure 1 .C demonstrates the impact of Up 4 U on the morphological pattern of the vascularisation of the yolk sac membrane.…”

“…The whole embryo culture (WEC) has been used before to study different growth factors, e.g. vascular endothelial growth [11], or to demonstrate the impact of different genes involved in angiogenesis [12]. We showed that incubation with alkaline phosphatase just partly reduced and blockade of purine P2 receptors markedly reduced the angiogenic effect of the endothelial secretome.…”

Editorial [Hot Topic:Recent Advances in Developmental and Reproductive Toxicology (Executive Editor: Gian Mario Tiboni )]

“…The review authored by Flick and Klug [5], concentrates on whole embryo culture system. Besides illustrating important methodological aspects and recent developments of the system, the authors summarize the growing literature supporting whole embryo culture as useful tool in assessing the embryotoxic potential of chemicals for regulatory purposes.…”