Remodeling of Blood Vessels

Abstract

Abstract-Vascular functions, including tissue perfusion and peripheral resistance, reflect continuous structural adaptation (remodeling) of blood vessels in response to several stimuli. Here, a theoretical model is presented that relates the structural and functional properties of microvascular networks to the adaptive responses of individual segments to hemodynamic and metabolic stimuli. All vessels are assumed to respond, according to a common set of adaptation rules, to changes in wall shear stress, circumferential wall stress, and tissue metabolic status (indicated by partial pressure of oxygen). An increase in vessel diameter with increasing wall shear stress and an increase in wall mass with increased circumferential stress are needed to ensure stable vascular adaptation. The model allows quantitative predictions of the effects of changes in systemic hemodynamic conditions or local adaptation characteristics on vessel structure and on peripheral resistance. Predicted effects of driving pressure on the ratio of wall thickness to vessel diameter are consistent with experimental observations. In addition, peripheral resistance increases by Ϸ65% for an increase in driving pressure from 50 to 150 mm Hg. Peripheral resistance is predicted to be markedly increased in response to a decrease in vascular sensitivity to wall shear stress, and to be decreased in response to increased tissue metabolic demand. This theoretical approach provides a framework for integrating available information on structural remodeling in the vascular system and predicting responses to changing conditions or altered vascular reactivity, as may occur in hypertension.

Aortic pulse pressure homeostasis emerges from physiological adaptation of systemic arteries to local mechanical stresses

“…The adaptive rules of the present work (Eq. 3) were first developed by Nguyen et al (46), who assumed that chronic adaptation is functionally similar to the acute shear stress-induced vasodilation and wall stress-induced vasoconstriction of muscular arteries (3,17,20,24,60) and microvessels (28,55,56,66). These adaptive rules were consistent with reported mechanisms of endothelial mechanotransduction (7) and observations from human clinical studies (9,37,39).…”

“…Chronic changes in blood pressure and flow have been correlated with structural remodeling of the arterial wall both in the young and elderly, involving changes in lumen radius, wall thickness, and stiffness of the arterial wall within weeks (7,13,20,36,38,55,64,74,83 …”

“…Adaptation-induced changes in radius, wall thickness, or stiffness affect mechanical stresses (9,17,37,39,75), even when luminal pressure and flow can be maintained (3,38,43,66). The inability to make mechanical stresses controlled, independent variables in vivo is an inescapable consequence of arterial growth and remodeling (22,55). Nonetheless, consensus is emerging that endothelial shear stress is the primary stimulus affecting arterial radius (20,55,60,82), and wall circumferential stress is the primary stimulus affecting wall thickness and stiffness (4,20,24).…”

MBEC special issue on microcirculation “engineering principles of vascular networks”

“…Also, the diversity of reactions at the biological level has to be represented in more detail in functional or engineering concepts. Examples are the discussion of the importance of vascular tone in the remodeling response of resistance arteries to hypertension in the present issue [8] and the earlier demonstration of the requirement for information transfer along vessel tress, e.g., by conduction of electrical signals [12]. The role of vasomotor control and its regulation is addressed by the studies of Duncker et al [1] and by Trzeciakowski and Chilian [16] in this issue.…”

“…Such observations show that in order to better understand the engineering principles of the vascular system more factors than shear stress alone have to be taken into account, most notably blood pressure (circumferential stress) and the metabolic state of the tissue [12]. Also, the diversity of reactions at the biological level has to be represented in more detail in functional or engineering concepts.…”