M.Y. Rennie, K.J. Whiteley, S. Kulandavelu, S.L. Adamson, J.G. Sled

This study evaluates microcomputed tomography (micro-CT) as a method to obtain quantitative three-dimensional (3D) information on the arterial and venous vasculature of the mouse placenta. Surface renderings at embryonic days (E) 13.5, 15.5, and 18.5 (full term) revealed that the arterial and venous vasculature branched within the chorionic plate whereas only the arterial vasculature deeply penetrated the placenta. Umbilical vessel diameters measured by micro-CT did not significantly differ from those measured non-invasively in vivo by ultrasound biomicroscopy. Variability in umbilical diameters, and surface area and volume measurements of arterial and venous vascular trees due to experimental error was low relative to biological variability, and significant inter-litter differences within gestational ages were detected. Furthermore, umbilical vessel diameter increased significantly and incrementally to an arterial diameter of 0.631+/-0.009 mm and a venous diameter of 0.690+/-0.018 mm at E18.5. Umbilical vein diameter was 3-9% greater than the artery, and both were significantly correlated with embryonic body weight (R> or =0.96). Surface area and volume were determined for vessels greater than the minimum resolvable diameter of 0.03 mm which therefore excluded capillaries. Arterial surface area and volume were unchanged from E13.5-15.5 but then more than doubled at E18.5 (to 170+/-13 mm(2) and 7.2+/-0.8mm(3), respectively). Venous surface areas and volumes changed similarly with development although surface areas were lower than their arterial counterparts. We conclude that micro-CT has sufficient accuracy and precision to quantify late gestational changes in the 3D structure of the arterial and venous vasculature of the mouse placenta.