Characterization of the vessel geometry, flow mechanics and wall shear stress in the great arteries of wildtype prenatal mouse.
BACKGROUND
Abnormal fluid mechanical environment in the pre-natal cardiovascular system is hypothesized to play a significant role in causing structural heart malformations. It is thus important to improve our understanding of the prenatal cardiovascular fluid mechanical environment at multiple developmental time-points and vascular morphologies. We present such a study on fetal great arteries on the wildtype mouse from embryonic day 14.5 (E14.5) to near-term (E18.5).


METHODS
Ultrasound bio-microscopy (UBM) was used to measure blood velocity of the great arteries. Subsequently, specimens were cryo-embedded and sectioned using episcopic fluorescent image capture (EFIC) to obtain high-resolution 2D serial image stacks, which were used for 3D reconstructions and quantitative measurement of great artery and aortic arch dimensions. EFIC and UBM data were input into subject-specific computational fluid dynamics (CFD) for modeling hemodynamics.


RESULTS
In normal mouse fetuses between E14.5-18.5, ultrasound imaging showed gradual but statistically significant increase in blood velocity in the aorta, pulmonary trunk (with the ductus arteriosus), and descending aorta. Measurement by EFIC imaging displayed a similar increase in cross sectional area of these vessels. However, CFD modeling showed great artery average wall shear stress and wall shear rate remain relatively constant with age and with vessel size, indicating that hemodynamic shear had a relative constancy over gestational period considered here.


CONCLUSIONS
Our EFIC-UBM-CFD method allowed reasonably detailed characterization of fetal mouse vascular geometry and fluid mechanics. Our results suggest that a homeostatic mechanism for restoring vascular wall shear magnitudes may exist during normal embryonic development. We speculate that this mechanism regulates the growth of the great vessels.
Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore.
Choon Hwai
CH
Yap
Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
Xiaoqin
X
Liu
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America.
Kerem
K
Pekkan
D000818:Animals; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000502:physiology; D001158:Arteries / Q000000981:diagnostic imaging* / Q000502:physiology*; D005333:Fetus / Q000196:embryology*; D005453:Fluorescence; D006439:Hemodynamics / Q000502:physiology*; D021621:Imaging, Three-Dimensional; D051379:Mice; D033401:Microscopy, Acoustic; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D033081:Shear Strength / Q000502:physiology