Failure Properties of Healthy and Diabetic Rabbit Thoracic Aortas and Their Potential Correlation with Mass Fractions of Collagen.

Abstract

Diabetes Mellitus (DM) plays an important role in aortic remodeling and alters the wall mechanics. The purpose of this study is to investigate and compare multi-directional failure properties of healthy and diabetic thoracic aortas. Thirty adult rabbits (1.6-2.2 kg) were collected and type 1 diabetic rabbit model was induced by injection of alloxan. A total of 10 control and 20 diabetic (with different time exposure to diabetic condition) rabbit descending thoracic aortas were harvested. Uniaxial tensile (UT) and radial tension (RT) tests were performed to determine circumferential, axial and radial failure stresses of the control and diabetic aortas, which were further correlated with mass fractions (MFs) of collagen. Throughout the UT test, there was a clear indication of anisotropic mechanical responses for some diabetic aorta specimens in the high loading domain. There was a trend towards an increase in the mean circumferential and axial failure stresses for the diabetic aortas when compared to the control aortas. However, differences were not statistically significant. The quantified failure stresses in the circumferential direction were, in general, higher than the stress values in the axial direction for both control and diabetic groups. For the RT test, the radial failure stresses of the diabetic aortas (in 8 weeks) were significantly higher than those of the control aortas (95 ± 17 vs. 63 ± 15 kPa, p = 0.01). Strong correlations were identified between the circumferential failure stresses and the MFs of collagen for both control and diabetic aortas. Nevertheless, this correlation was not present in the axial and radial directions. The results suggest that there is a lower propensity of radial tear occurrence within the diabetic aortic wall. More importantly, time exposure to diabetic condition is not a factor that may change failure properties of the rabbit descending thoracic aortas in the circumferential and axial directions.