Comparative mechanics of diverse mammalian carotid arteries

Abstract

The prevalence of diverse animal models as surrogates for human vascular pathologies necessitate a comprehensive understanding of the differences that exist between species. Comparative passive mechanics are presented here for the common carotid arteries taken from bovine, porcine, ovine, leporine, murine-rat, and murine-mouse specimens. Data is generated using a scalable biaxial mechanical testing device following consistent circumferential (pressure-diameter) and axial (force-length) testing protocols. The structural mechanical response of carotids under equivalent loading, quantified by the deformed inner radius, deformed wall thickness, lumen area compliance and axial force, varies significantly among species but generally follows allometric scaling. Conversely, descriptors of the local mechanical response within the deformed arterial wall, including mean circumferential stress, mid-wall circumferential stretch, and mean axial stress, are relatively consistent across species. Unlike the larger animals studied, the diameter distensibility curves of murine specimens are non-monotonic and have a significantly higher value at 100 mmHg. Taken together, our results provide baseline structural and mechanical information for carotid arteries across a broad range of common animal models.

Fig 1. Images of common carotid arteries.

(left) Vessels mounted within the biaxial testing device at λ_z = 1.5 and P = 100 mmHg. (a) Bovine: OD = 8.82 mm, (b) porcine: OD = 4.96 mm, (c) ovine: OD = 5.49 mm, (d) leporine: OD = 2.60 mm, (e) murine-rat: OD = 1.14, and (f) murine-mouse: OD = 0.65 mm vessels shown. Scale bars are 1 mm. (right) Unloaded ring sectors of each vessel with 1 mm ruler.

Fig 2. Full range of common carotid arteries subjected to passive mechanical testing.

(top) Pressure-diameter at λ_z = 1.5, (bottom) axial force-stretch on a logarithmic scale at P = 100 mmHg for Bovine, porcine, ovine, leporine, murine-rat, and murine-mouse. All values are mean (n = 6) ± SEM.

Fig 3. Comparative structural and force values for common carotid arteries subjected to passive mechanical testing at 100 mmHg and 1.5 axial stretch ratio.

(a) Inner radius, (b) wall thickness, (c) area compliance, and (d) axial force from bovine, porcine, ovine, leporine, murine-rat, and murine-mouse carotid arteries. All values are mean ± STD. (*) denotes statistical significance at p ≤ 0.05 between the leftmost group and the corresponding hash-mark.

Fig 4. Full range of stress and stretch for common carotid arteries subjected to passive mechanical testing.

(top) Circumferential stress-stretch at λ_z = 1.5, and (bottom) axial stress-stretch at 100 mmHg for bovine, porcine, ovine, leporine, murine-rat, and murine-mouse common carotid arteries. All values are mean (n = 6) ± SEM.

Fig 5. Comparative stress and strain values for common carotid arteries subjected to passive mechanical testing at 100 mmHg.

(a) Circumferential stress, (b) circumferential stretch, and (c) axial stress for bovine, porcine, ovine, leporine, murine-rat, and murine-mouse carotid arteries at 1.5 axial stretch ratio. Figure (d) illustrates the minimal axial stretch ratio to maintain vessels in tension at 100 mmHg. All values are mean ± STD. (*) denotes statistical significance at p ≤ 0.05 between the leftmost group and the corresponding hash-mark.

Fig 6. Distensibility of bovine, porcine, ovine, leporine, murine-rat, and murine-mouse carotid arteries.

Diameter distensibility at (a) full pressure range mean ± SEM (b) 100 mmHg mean ± STD, and (c) 100 mmHg mean ± STD vs. animal weight and fit to a power law allometric scaling relationship with the coefficient of determination shown. (*) denotes statistical significance at p ≤ 0.05 between the leftmost group and the corresponding hash-mark.

Fig 7. Allometric scaling of structural quantities with weight.

(a) Inner radius, (b) wall thickness, (c) area compliance, (d) axial force, at 100 mmHg and λ_z = 1.5. All data fit to a power law allometric scaling relationship with the coefficient of determination shown. All values are mean ± STD.

Fig 8. Allometric scaling of mechanical quantities with weight.

(a) Circumferential stress, (b) axial stress, and (c) circumferential stretch measured at λ_z = 1.5. (d) Minimum axial stretch at 100 mmHg. All data fit to a power law allometric scaling relationship with the coefficient of determination shown. All values are mean ± STD.

Fig 9. Basic histology of common carotid arteries.

Hematoxylin and Eosin (left) and Masson’s Trichrome (right) for (a-b) Bovine, (c-d) porcine, (e-f) ovine, (g-h) leporine, (i-j) murine-rat, and (j-k) murine-mouse. 0.1 mm scale bar.