Biomechanics of the arterial wall under simulated flow conditions

Brant, Arthur; Shah, Sanjay S.; Rodgers, V.G.J.; Hoffmeister, Jeffrey W.; Herman, Ira M.; Kormos, Robert L.; Borovetz, Harvey S.

doi:10.1016/0021-9290(88)90004-8

Cited by 25 publications

(10 citation statements)

References 23 publications

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“…For example, because of the elevated pulse pressure, the change in internal vessel radius or vessel wall thickness (Fig. 4) measured during the simulation of tPP/tTP (7.1%) significantly exceeded that (2.7%) when normotension-t'TP conditions were imposed upon the test vessels (2,3). At the microscopic level, the increased motion of the vessel wall associated with these group III experiments may have "anchored" the EC to the underlying substratum as indicated by the EC shifting to a more polygonal shape ( Fig.…”

Section: Discussionmentioning

confidence: 93%

Hemodynamics and the vascular endothelial cytoskeleton.

Herman¹,

Brant²,

Warty³

et al. 1987

The Journal of Cell Biology

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Abstract, Although there is considerable evidence to suggest that hemodynamics play an important role in vascular disease processes, the exact mechanisms are unknown. With this in mind, we have designed a pulsatile perfusion apparatus which reproducibly delivers pulsatile hemodynamics upon freshly excised canine carotid arteries in vitro. Quantifiable simulations included (a) normotension with normal or lowered flow rates (120/80 mmHg, 120 and 40 ml/min), (b) normotension with lowered or elevated transmural pressures (40-170 mmHg), and (c) elevated pulse pressure (120 and 80 mmHg) with normal (150 ml/min) or elevated rates of flow (300 and 270 ml/min). Arterial biomechanical stresses and cellular behaviors were characterized biochemically and morphologically under all these simulations which continued for 2-24 h. We found that increased pulse pressure alone had little effect on the total amount of radiolabeled [4-J4C]cholesterol present within the medial compartment. However, normotension when coupled with altered transmural pressure yielded a three-to fourfold increase.Combinations of increased pulse pressure and flow potentiated cholesterol uptake by a factor of 10 when compared with normotension control values. Simulations that enhanced carotid arterial cholesterol uptake also influenced the endothelial cytoskeletal array of actin. Stress fibers were not present within the carotid endothelial cells of either the sham controls or the normotension and increased pulse pressure (normal flow) simulations. Endothelial cells lining carotids exposed to elevations in flow or those present within vessels perfused as per simulation b above assembled stress fibers (x = 4 and 10 per cell, respectively) within the time course of these studies. When endothelial cells were subjected to hemodynamic conditions that potentiated maximally cholesterol transport, no diffuse or stress fiber staining could be seen, but the cortical array of actin was intact. These results suggest that those biomechanical stresses that alter endothelial permeability and intimal integrity may do so via cytoskeletal actin signaling.ECENT experimental evidence indicates that endothelial cells (EC), 1 which line the blood vascular systems of higher vertebrates, are actively involved in maintenance of intimal integrity. This stabilization against the blood shearing forces and biomechanical wall stresses at the luminal-EC interface may be directly related to the intimal cells' ability to synthesize and organize (a) junctional elements, (b) materials of the basal laminae that promote EC adhesion to the extracellular matrix, and (c) an intricate cytoskeleton composed of contractile and structural proteins needed to modulate the luminal-abluminal shear zone.Early work in vitro revealed that vascular EC possessed linear cytoplasmic fibrils (16). Naming the structures "tension striae" the Lewises proposed that these elements (later renamed "stress fibers") promoted adhesion of cells to the underlying substrate. A structural rather than motile role for stress fi...

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Section: Discussionmentioning

confidence: 93%

Hemodynamics and the vascular endothelial cytoskeleton.

Herman¹,

Brant²,

Warty³

et al. 1987

The Journal of Cell Biology

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“…Immediately after euthanasia, the intact esophagus from seven animals in groups 3 and 4 was isolated and a custom clamping device [42] was used to maintain the in vivo length. The esophagus was excised in its entirety and was placed in lactated Ringer's solution at 4°C until time for testing (2Ϫ4 h).…”

Section: Pressure-diameter Responsesmentioning

confidence: 99%

Esophageal Reconstruction with ECM and Muscle Tissue in a Dog Model

Badylak

Vorp

Spievack

et al. 2005

Journal of Surgical Research

271

178

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“…The EVPS used in this study has gone through several design iterations to improve its functionality and diversity [3,39,[244][245][246][247]. The previous generation EVPS, upon which the current design was based, is shown schematically in Several other groups have designed specialized EVPSs for studying biochemical responses of blood vessel segments to imposed biomechanical stresses.…”

Section: The Concept Of Ex Vivo Perfusion Was Originally Investigatedmentioning

confidence: 99%

“…Our laboratory's well established, validated EVPS has been used for over two decades to study the mechanopathobiological responses of intact blood vessel segments to accurately simulated physiologic biomechanical signals [3,39,[244][245][246][247][248][249]. The EVPS used in this study has gone through several iterations to improve its functionality and is described in detail below.…”

Section: History Of Ex Vivo Vascular Perfusionmentioning

confidence: 99%

“…Vein segments with and without the wrap were mounted in our well established, validated earlier version EVPS (not the version described in Chapter 2.0) [3,39,245,246,248,249,273,275]. Hz as described in Section 2.3.3. pO 2 , pCO 2 , pH, perfusate temperature, and bathing media temperature were measured within each loop of the paired EVPS every hour.…”

Section: Ex Vivo Perfusion Conditionsmentioning

confidence: 99%

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In Situ Bioengineering of Arterial Vein Grafts

El-Kurdi

Morelli

Hong

et al. 2008

ASME 2008 Summer Bioengineering Conference, Parts a and B

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The autogenous saphenous vein remains the graft of choice for both coronary (500,000 annually in the US) and peripheral (80,000 annually) arterial bypass procedures. Failure of arterial vein grafts (AVGs) remains a major problem, and patients with failed grafts will die or require reoperation. Intimal hyperplasia (IH) accounts for 20% to 40% of all AVG failures. It is believed that this adverse pathological response by AVGs is largely due to their abrupt exposure to the significantly elevated circumferential wall stress (CWS) associated with the arterial system. We believe that if an AVG is given an ample opportunity to adapt and remodel to the stresses of its new environment, cellular injury may be reduced, thus limiting the initiating mechanisms of IH.The goal of this work was to develop a new mechanical conditioning paradigm, in the form of a peri-adventitially placed, biodegradable polymer wrap, to safely and functionally "arterialize" AVGs in situ. The polymer wrap was tuned so that as it degraded over a desired period of time, the mechanical support offered by it was reduced and the vein was exposed to gradually increasing levels of CWS in situ.To investigate the effects of mechanical conditioning on AVGs, we utilized both our well established, validated ex vivo vascular perfusion system (EVPS) as well as an appropriate preclinical animal model. The "engineering" component of this bioengineering study was to enhance our EVPS capabilities. Enhancements were made in the form of rigorous mathematical modeling, via subspace system identification, and automatic feedback control, via proportional iv integral and derivative control, of the arterial CWS and shear stress waveform generation capabilities of the EVPS. Pairs of freshly harvested porcine internal jugular veins (PIJVs) were perfused ex vivo under several biomechanical conditions. The acute hyperplastic response of PIJVs abruptly exposed to arterial hemodynamic conditions was compared to PIJVs perfused under normal venous conditions. In an attempt to attenuate this acute hyperplastic response, an ex vivo mechanical conditioning paradigm was imposed onto the PIJVs both via manual adjustment of EVPS parameters and via an adventitially placed tuned electrospun biodegradable polymer wrap. Early markers of IH were evaluated post-perfusion, and they included vascular smooth muscle cell apoptosis, proliferation, and phenotypic modulation. Quantification of these markers via immunohistochemical techniques provided the foundation for the final stage of this work. To assess the efficacy of the tuned electrospun biodegradable polymer wrap in attenuating the development of intimal hyperplasia in AVGs, a series of preclinical studies was performed in a pig model. PIJVs abruptly exposed to arterial levels of CWS showed a significant increase in apoptosis and in the number of synthetic smooth muscle cells, as well as a decrease in proliferation. Mechanical conditioning, via both manual adjustment of the EVPS parameters and placement of the biodegradable adventitial wra...

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Biomechanics of the arterial wall under simulated flow conditions

Cited by 25 publications

References 23 publications

Hemodynamics and the vascular endothelial cytoskeleton.

Hemodynamics and the vascular endothelial cytoskeleton.

Esophageal Reconstruction with ECM and Muscle Tissue in a Dog Model

In Situ Bioengineering of Arterial Vein Grafts

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