Wall shear stress in the mouse aortic arch: Does size matter?

In recent studies wall shear stress (WSS) in the mouse aortic arch has been investigated and values up to 30 times higher than in humans have been reported. However adult mice experience a significant increase in body weight and aortic dimensions with age. In this paper the influence of the age and body mass of the investigated mouse on the resulting wall shear stress is investigated. A model of a mouse aortic arch was created based on a micro-CT scan of a vascular corrosion cast of an 8-week old wild type mouse. This model was then rescaled based on a set of rules to obtain 5 models with aortic root diameter varying from 0.7 to 1.5 mm. This variation in aortic dimension covers the range that occurs throughout different stages in the mouse life cycle (also depending on the mouse strain and sex). Fluent was used to solve the Navier-Stokes equations for the flow. All models were calculated using both a steady and a time-dependent inlet velocity. Consistent with literature, wall shear stresses much higher than those normally encountered in humans were found. For the steady simulations we found a decrease in average wall shear stress from +/- 10 Pa to +/- 6 Pa for a diameter increasing from 0.7 mm to 1.5 mm. The magnitude and pattern of wall shear stresses for the aortic arch were in line with literature when comparing for similar diameters. Our results show that one should be very cautious when interpreting wall shear stress values for mice, since the obtained values depend strongly on the age and corresponding body mass of the investigated animal.