Study of the Biomechanical and Histological Properties of the Thoracic Aorta of Diabetic Rats and Exposed to Cigarette Smoke.

Abstract

Introduction: Aortic aneurysm (AA) carries significant clinical implications due to its prevalence and potential complications. However, its etiopathogenesis remains poorly understood. The association between smoking and AA development has been consistently confirmed. Although AA was initially attributed to atherosclerosis, a negative association between diabetes (a major risk factor for atherosclerosis) and vascular aneurysmal disease has been observed. Investigating the biomechanical and histological properties of the aortic wall may shed light on the etiopathogenesis of aneurysms.

Methods: This study involved 75 Wistar rats, divided into four groups: control (CG), smoker (SG), diabetic (DG), and diabetic plus smoker (DSG). Rats in the SG and DSG groups were exposed to cigarette smoke for 30 min daily, 5 days a week. Diabetes was induced by intravenous injection of streptozotocin. After 16 weeks, the animals were sacrificed to collect the thoracic aorta. Destructive uniaxial tensile tests were performed to obtain the following biomechanical failure properties: force, tension, stress, strain, and strain energy. Histological analysis of these fragments consisted of the percentage evaluation of collagen and elastic fibers and verification of the magnitude of the inflammatory process in the arterial wall. Metalloproteinase-9 activity in the aortic specimens was quantified through zymography.

Results: Valid biomechanical tests of 36 specimens were analyzed, with 8 belonging to CG, 9 to DG, 11 to SG, and 8 to DSG. Biomechanical analysis of the fragments revealed that the maximum force and stress until rupture were lower in the DSG than in the SG with statistical significance. Evaluations of the percentage of collagen and elastic fibers as well as the inflammatory process showed no statistically significant difference among the groups studied. MMP-9 activity did not present a statistically significant difference among the different groups.

Conclusions: The biomechanical properties related to resistance are lower in DSG than in SG while elasticity, histological changes related to collagen fiber, elastic fiber, and inflammatory process, and MMP-9 activity of the aortic wall of rats do not show differences between CG and DG, SG, and DSG. Based on the methodology employed in this study, it appears that the thoracic aorta is resilient against aneurysm development.