Hemodynamics and the vascular endothelial cytoskeleton

Area of Science:

• Cardiovascular Biology
• Biomedical Engineering
• Cellular Physiology

Background:

• Hemodynamics are implicated in vascular disease, but precise mechanisms remain unclear.
• Understanding these mechanisms requires controlled in vitro models of blood flow.
• Canine carotid arteries offer a suitable model for studying hemodynamic effects on vascular tissue.

Purpose of the Study:

• To investigate the impact of specific hemodynamic forces on cholesterol transport in canine carotid arteries.
• To characterize cellular responses, particularly endothelial actin cytoskeletal changes, under varied hemodynamic conditions.
• To elucidate the role of biomechanical stress in endothelial permeability and vascular integrity.

Main Methods:

• Developed a pulsatile perfusion apparatus to simulate various hemodynamic conditions in excised canine carotid arteries.
• Applied controlled simulations including normotension with varied flow rates, altered transmural pressures, and elevated pulse pressure with different flow rates.
• Analyzed arterial biomechanical stresses and cellular behaviors (cholesterol content, actin cytoskeleton) over 2-24 hours.

Main Results:

• Increased pulse pressure alone had minimal effect on medial cholesterol levels.
• Altered transmural pressure significantly increased cholesterol uptake (3-4 fold).
• Combined elevated pulse pressure and flow potentiated cholesterol uptake 10-fold compared to controls.
• Hemodynamic conditions promoting cholesterol uptake altered endothelial actin stress fibers, with maximal uptake correlating with intact cortical actin.

Conclusions:

• Biomechanical stresses, particularly those involving transmural pressure and flow, are critical drivers of cholesterol accumulation in arterial walls.
• Changes in endothelial cytoskeletal actin signaling are linked to altered endothelial permeability and intimal integrity under specific hemodynamic conditions.
• These findings suggest cytoskeletal actin plays a key role in mediating vascular responses to hemodynamic forces, potentially contributing to vascular disease pathogenesis.