The combined effects of transmural pressure and axial strain on arterial remodeling ex vivo
The roles of blood pressure and flow-induced shear stress in regulating vascular function and pathologies have been extensively studied. In addition to these forces applied to the luminal surface, vessels are typically subjected to significant axial tensile forces due to the tethering of their adventitial surface to surrounding tissue. These axial loads result in significant axial strains; arteries in vivo are normally at a stretch ratio (λ=actual length/length with no axial load) significantly greater than 1.0. The stretch ratio varies along the vascular tree, diminishes with age, and is reduced to ∼1.0 in grafted vessels. Results from our laboratory as well as those of others have shown that arteries exposed to increased axial stretch grow and remodel in an apparent effort to restore normal stretch ratios. Yet the role of normal stretch ratios, as occurs in normal arteries in vivo, and the effects of the removal of this axial stretch, as occurs in grafted vessels, has until now remained unknown. A better understanding of these possibly interactive mechanical stimuli and the mechanisms responsible for both physiological and pathological changes may suggest therapeutic interventions. To investigate the contribution of axial strain to arterial function and remodeling, we cultured porcine carotid arteries at normal and reduced axial stretch ratios in the presence of normotensive and hypertensive pressures. It was found that an in vivo level of axial stretch was necessary to obtain similar changes in wall structure comparable to those found in vivo. It was also observed that arterial contractility was at least in part dependent upon the level of axial stretch to which the arteries were subjected. Last, through multiple linear regression analysis it was found that stresses in the axial direction (when employing levels of axial stretch similar to those found in vivo) actually have a greater effect than circumferential stresses on changes in wall structure and composition, warranting further investigation into the role of axial strain reduction on arterial remodeling. ^
Amanda Renee Lawrence,
"The combined effects of transmural pressure and axial strain on arterial remodeling ex vivo"
(January 1, 2006).
Dissertations available from ProQuest.