Refinement of a morphological scoring system for postimplantation rabbit conceptuses

• Published in: Birth defects research. Part B. Developmental and reproductive toxicology Vol. 80; no. 3; pp. 213 - 222
• Main Authors: Carney, Edward W., Tornesi, Belen, Keller, Charles, Findlay, Heather A., Nowland, William S., Marshall, Valerie A., Ozolinš, Terence R.S.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-06-2007
• Subjects: Animals; comparative development; Culture Techniques; embryo; Embryo, Mammalian - abnormalities; Embryo, Mammalian - drug effects; Embryo, Mammalian - pathology; Embryo, Mammalian - physiology; Embryonic Development; Female; morphology; Pregnancy; Pregnancy, Animal - physiology; Rabbits - embryology; Toxicology - methods; whole embryo culture
• ISSN: 1542-9733; 1542-9741
• DOI: 10.1002/bdrb.20118

BACKGROUND: The rabbit is used extensively in developmental toxicity testing, yet basic information on rabbit embryo development is lacking. The goals of this study were to refine a rabbit embryo morphology scoring system, and use it to evaluate rabbit whole embryo cultures (WEC). METHODS: A total of 265 conceptuses were harvested between GD 8.0 and 12.0 (coitus = GD 0) at 6‐hr intervals and examined in detail. Discreet developmental landmarks were then established for 18 morphological features and assigned scores ranging from 0 up to 6. The scoring system was then validated on a subset of randomly selected in vivo conceptuses, and was used to evaluate conceptuses grown for 12, 24, 36, or 48 hr in WEC beginning from GD 9.0 or 10.0. A few embryos also were examined using microscopic computed tomography (microCT)‐based virtual histology™ to assess the utility of this technology. RESULTS: Morphology scores of in vivo developed conceptuses increased linearly (r2 = 0.98) with advancing gestational age, from means of 0.0 on GD 8.0 to 67.9 on GD 12.0. Application of the scoring system, supplemented with evidence from Virtual histology™, indicated that the WEC system supported normal morphological development of rabbit conceptuses. However, when explanted at GD 9, the rate of development was about 20% slower than in vivo, whereas the rate of development in WEC from GD 10 was indistinguishable from in vivo. CONCLUSIONS: This work enhances the evaluation tools available to study mechanisms of normal and abnormal development in this widely used animal testing species. Birth Defects Res (Part B), 2007. © 2007 Wiley‐Liss, Inc.