Evaluation of dynamic response and biomechanical properties of isolated blood vessels

Transport of Low-Density Lipoprotein Into the Blood Vessel Wall During Atherogenic Diet in the Isolated Rabbit Carotid Artery

BACKGROUND

Atherosclerosis is a chronic fibroproliferative disease that includes accumulation of cholesterol-rich lipids in the arterial wall. Though numerous studies have investigated atherosclerosis, not enough is known about the exact mechanisms of low-density lipoprotein (LDL) transport into the blood vessel wall. Therefore, we explored the (125)I-LDL transport into the arterial wall under constant perfusion flow and pressure as well as the influence of duration of atherogenic diet on (125)I-LDL transport and biomechanical properties of carotid artery.

METHODS AND RESULTS

The isolated segment of rabbit carotid artery was used under constant perfusion flow and pressure-induced (0 mmHg and 140 mmHg) blood vessel distension, with the possibility to change and precisely calculate shear stress during the experiment. Obtained results indicate the influence of atherogenic diet duration and consequent variation of shear stress on (125)I-LDL transport into the blood vessel wall. (125)I-LDL transport into the blood vessel wall at low pressure-induced blood vessel distension decreases by the increase of the shear stress and in relation to the atherogenic diet duration. At high pressure-induced blood vessel distension, (125)I-LDL transport increases in relation to the atherogenic diet duration and the increase of shear stress.

CONCLUSIONS

The influence of shear stress is a more dominant parameter on LDL uptake at low pressure-induced blood vessel distension; however, the atherogenic diet duration has more of a dominant influence on LDL uptake at high pressure-induced vessel distension.

Computer simulation and experimental analysis of LDL transport in the arteries

Atherosclerosis develops from oxidized low-density lipoprotein molecules (LDL). When oxidized LDL evolves in plaque formations within an artery wall, a series of reactions occur to repair the damage to the artery wall caused by oxidized LDL. Macrophages accumulate inside arterial intima, they started to collect oxidized LDL and form foam cells. Smooth muscle cells accumulate in the atherosclerotic arterial intima, where they proliferate and secrete extracellular matrix to form a fibrous cap. In this study, experimental model of LDL transport on the isolated blood vessel from rabbit on high fat diet after 8 weeks is simulated numerically by using a specific model and histological data. The 3D blood flow is governed by the Navier-Stokes equations, together with the continuity equation. Mass transfer within the blood lumen and through the arterial wall is coupled with the blood flow by the convection-diffusion equation. LDL transport in lumen of the vessel is described by Kedem-Katchalsky equations. The inflammatory process is solved using three additional reaction-diffusion partial differential equations. Matching of histological rabbit data is performed using 3D histological image reconstruction and 3D deformation of elastic body. Computed concentrations of labeled LDL of 5.2 % and macrophages distribution of 4.2% inside the media are found to be in good agreement with experimental results. This simulation study provides a useful tool for understanding and prediction of LDL transport through the arterial wall and evolution of atherosclerotic plaques.

Glucagon effects on ischemic vasodilatation in the isolated rat heart

The myocardial reperfusion following ischemia leads to the ischemic vasodilation by affecting the release of various vasoactive substances, such as free radicals, NO, and histamine. In addition, some evidences suggest that glucagon itself may alter the release of those substances. In this study, we investigated the ischemic vasodilation of the isolated rat heart, as well as the concentrations of NO, TBARS, and histamine in the coronary venous effluent either in the presence or in the absence of glucagon. Our results showed that in the presence of glucagon, there was a faster restoration of coronary perfusion pressure during ischemic vasodilation compared to the absence of glucagon (124 +/- 5.6 versus 81 +/- 5.2 s) with no apparent changes in TBARS concentration. The glucagon's administration leads to the decreased release of histamine by approximately 35%. Biphasic release of NO in the presence of glucagon initially showed augmentation by 60%, followed by the significant attenuation of 45%.