Twenty-fold difference in hemodynamic wall shear stress between murine and human aortas

Endothelial cells regulate vascular tone and mural remodelling in a shear-dependent manner that is commonly assumed to keep wall shear stress constant across arteries and species. Allometric arguments show that aortic flow velocity is constant across species, a deduction that is consistent with much experimental data, but the same arguments also show that the shear stress experienced by aortic endothelium will depend inversely on body mass to the 38th power, and hence will be 20-fold higher in mice than in men. This conclusion is robust and has important implications for the study of shear-dependent vascular biology and pathology.