scholarly journals Shear stress and aneurysms: a review

2019 ◽  
Vol 47 (1) ◽  
pp. E2 ◽  
Author(s):  
Brittany Staarmann ◽  
Matthew Smith ◽  
Charles J. Prestigiacomo
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Wall Shear Stress ◽  
Smooth Muscle Cells ◽  
Frictional Force ◽  
Vessel Wall ◽  
Risk Of Rupture ◽  
Aneurysm Growth

Wall shear stress, the frictional force of blood flow tangential to an artery lumen, has been demonstrated in multiple studies to influence aneurysm formation and risk of rupture. In this article, the authors review the ways in which shear stress may influence aneurysm growth and rupture through changes in the vessel wall endothelial cells, smooth-muscle cells, and surrounding adventitia, and they discuss shear stress–induced pathways through which these changes occur.

scholarly journals Focal irregularities in 7-Tesla MRI of unruptured intracranial aneurysms as an indicator for areas of altered blood-flow parameters

2019 ◽  
Vol 47 (6) ◽  
pp. E7
Author(s):  
Matthias Millesi ◽  
Engelbert Knosp ◽  
Georg Mach ◽  
Johannes A. Hainfellner ◽  
Gerda Ricken ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Field Strength ◽  
Vessel Wall ◽  
Intracranial Aneurysms ◽  
7 Tesla ◽  
Risk Of Rupture ◽  
Wall Shear ◽  
Cfd Analyses

OBJECTIVEIn the last several decades, various factors have been studied for a better evaluation of the risk of rupture in incidentally discovered intracranial aneurysms (IAs). With advanced MRI, attempts were made to delineate the wall of IAs to identify weak areas prone to rupture. However, the field strength of the MRI investigations was insufficient for reasonable image resolution in many of these studies. Therefore, the aim of this study was to analyze findings of IAs in ultra–high field MRI at 7 Tesla (7 T).METHODSPatients with incidentally found IAs of at least 5 mm in diameter were included in this study and underwent MRI investigations at 7 T. At this field strength a hyperintense intravascular signal can be observed on nonenhanced images with a brighter “rim effect” along the vessel wall. Properties of this rim effect were evaluated and compared with computational fluid dynamics (CFD) analyses.RESULTSOverall, 23 aneurysms showed sufficient image quality for further evaluation. In 22 aneurysms focal irregularities were identified within this rim effect. Areas of such irregularities showed significantly higher values in wall shear stress and vorticity compared to areas with a clearly visible rim effect (p = 0.043 in both).CONCLUSIONSA hyperintense rim effect along the vessel wall was observed in most cases. Focal irregularities within this rim effect showed higher values of the mean wall shear stress and vorticity when compared by CFD analyses. Therefore, these findings indicate alterations in blood flow in IAs within these areas.

Thrombin Inhibition and Thrombin Generation by Cultured Aortic Endothelial and Smooth Muscle Cells from Minipig

1982 ◽  
Vol 48 (01) ◽  
pp. 101-103 ◽  
Author(s):  
B Kirchhof ◽  
J Grünwald
Keyword(s):  
Endothelial Cells ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vessel Wall ◽  
Thrombin Generation ◽  
Muscle Cells ◽  
Thrombin Inhibition ◽  
Generating Capacity ◽  
Wall Interaction ◽  
Cells Cultured

SummaryEndothelial and smooth muscle cells cultured from minipig aorta were examined for their inhibitory activity on thrombin and for their thrombin generating capacity.Endothelial cells showed both a thrombin inhibition and an activation of prothrombin in the presence of Ca++, which was enhanced in the presence of phospholipids. Smooth muscle cells showed an activation of prothrombin but at a lower rate. Both coagulation and amidolytic micro-assays were suitable for studying the thrombin-vessel wall interaction.

Surface Engineering in Microfluidic Devices for the Isolation of Smooth Muscle Cells and Endothelial Cells

2007 ◽  
Vol 1004 ◽  
Author(s):  
Shashi Murthy ◽  
Brian Plouffe ◽  
Milica Radisic
Keyword(s):  
Tissue Engineering ◽  
Endothelial Cells ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Cell Adhesion ◽  
Smooth Muscle Cells ◽  
Cell Sorting ◽  
Microfluidic Devices ◽  
Muscle Cells ◽  
Small Sample

AbstractMicrofluidic cell separation systems have emerged as attractive alternatives to traditional techniques in recent years. These systems offer the advantages of being able to handle small sample volumes and at the same time achieve highly selective separation. Conventional separation techniques, including both fluorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS), typically require a pre-processing incubation step to attach ligated tags (such as fluorescent dyes or magnetic beads) to cell surfaces prior to separation. These techniques are also constrained by infrastructure and high cost. Microfluidic devices with surface-immobilized adhesion molecules eliminate the need for pre-processing incubation and are a low cost alternative.We describe the selective adhesion of smooth muscle cells and endothelial cells in microfluidic devices coated with adhesion peptides. The device geometry is such that the shear stress varies linearly as a function of flow channel length, allowing simultaneous evaluation of the effects of surface chemistry and fluid shear on cell adhesion. The adhesion peptides, val-ala-pro-gly (VAPG) and arg-glu-asp-val (REDV), are known to bind selectively to smooth muscle cells and endothelial cells, respectively. These peptides were tethered to the device surface using silane chemistry and NHS-ester coupling. Cell adhesion was examined in a shear stress range of 1.3-4.0 dyn/cm2. Under these conditions, endothelial cells show significantly higher adhesion to REDV-coated devices compared to smooth muscle cells and fibroblasts. Correspondingly, smooth muscle cell adhesion in VAPG-coated devices is much greater than that of endothelial cells and fibroblasts. This selective binding behavior is also observed when mixed suspensions of the three cell types are flowed into both types of peptide-coated microfluidic devices. These results suggest that microfluidic devices coated with REDV and VAPG can be used as effective separation tools in various applications, such as tissue engineering. Specific examples of applications in cardiac and skin tissue engineering will be discussed.

Microvascular dilation in response to occlusion: a coordinating role for conducted vasomotor responses

2000 ◽  
Vol 279 (1) ◽  
pp. H279-H284 ◽  
Author(s):  
Kim A. Dora ◽  
David N. Damon ◽  
Brian R. Duling
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Third Order ◽  
Vasomotor Responses ◽  
Vasodilatory Response ◽  
Flow Through ◽  
Stress Dependent ◽  
Dependent Mechanism

In rat cremasteric microcirculation, mechanical occlusion of one branch of an arteriolar bifurcation causes an increase in flow and vasodilation of the unoccluded daughter branch. This dilation has been attributed to the operation of a shear stress-dependent mechanism in the microcirculation. Instead of or in addition to this, we hypothesized that the dilation observed during occlusion is the result of a conducted signal originating distal to the occlusion. To test this hypothesis, we blocked the ascending spread of conducted vasomotor responses by damaging the smooth muscle and endothelial cells in a 200-μm segment of second- or third-order arterioles. We found that a conduction blockade eliminated or diminished the occlusion-associated increase in flow through the unoccluded branch and abolished or strongly attenuated the vasodilatory response in both vessels at the branch. We also noted that vasodilations induced by ACh (10−4 M, 0.6 s) spread to, but not beyond, the area of damage. Taken together, these data provide strong evidence that conducted vasomotor responses have an important role in coordinating blood flow in response to an arteriolar occlusion.

Devlopment of a Cell Coculture Microfluidic Shear Device for Mechano-Transmission Study

2007 ◽  
Author(s):  
Devon Scott ◽  
Aaron Richman ◽  
Craig Lanning ◽  
Robin Shandas ◽  
Wei Tan
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Pulmonary Vascular Disease ◽  
Interstitial Tissue ◽  
Endothelial Lining ◽  
Flow Shear ◽  
Flow Shear Stress

We have developed a microfluidic shear device that allows for the study of cell communication in a dynamically controlled biochemical and biomechanical environments simulating cells’ living environments in vivo. Such study may help to improve our understanding in the effects of hypertension-relevant and vascular development-relevant flow shear stress on cell behaviors. Endothelial cells may be a key factor for transmitting the blood flow conditions from the endothelial lining to interstitial layers and smooth muscle cells. The interstitial flow stress and the shear stress induced signaling factors may greatly alter vascular biology of these deep layers. Endothelial cells act as a mechano-transducer by converting shear stress into biochemical signaling factors. The biochemical factors diffuse to smooth muscle cells and further alter the biological structure of vascular tissues. Also, the flow shear stress will be transmitted to the interstitial tissue layer through the pores resulted from the pores in the fenestrated endothelial lining. Studies in both the mechano-transduction process and the mechano-transmission process will benefit from a biomimetic flow shear device with co-cultured cells. Our device will allow the co-culture of endothelial cells and smooth muscle cells to study these biomechanical processes. The pulmonary arterial cells are used as a model in the study. The microfluidic device developed here will be used to enhance the understanding of pulmonary vascular disease pathogenesis due to the variations in the flow shear stress.

A Numerical Multiscale Study of the Haemodynamics in an Image-Based Model of Human Carotid Artery Bifurcation

2009 ◽  
Author(s):  
Diego Gallo ◽  
Raffaele Ponzini ◽  
Filippo Consolo ◽  
Diana Massai ◽  
Luca Antiga ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Cardiovascular System ◽  
Vessel Wall ◽  
3D Model ◽  
Carotid Bifurcation ◽  
Wall Shear ◽  
Flow Division

The initiation and progression of vessel wall pathologies have been linked to disturbances of blood flow and altered wall shear stress. The development of computational techniques in fluid dynamics, together with the increasing performances of hardware and software allow to routinely solve problems on a virtual environment, helping to understand the role of biomechanics factors in the healthy and diseased cardiovascular system and to reveal the interplay of biology and local fluid dynamics nearly intractable in the past, opening to detailed investigation of parameters affecting disease progression. One of the major difficulties encountered when wishing to model accurately the cardiovascular system is that the flow dynamics of the blood in a specific vascular district is strictly related to the global systemic dynamics. The multiscale modelling approach for the description of blood flow into vessels consists in coupling a detailed model of the district of interest in the framework of a synthetic description of the surrounding areas of the vascular net [1]. In the present work, we aim at evaluating the effect of boundary conditions on wall shear stress (WSS) related vessel wall indexes and on bulk flow topology inside a carotid bifurcation. To do it, we coupled an image-based 3D model of carotid bifurcation (local computational domain), with a lumped parameters (0D) model (global domain) which allows for physiological mimicking of the haemodynamics at the boundaries of the 3D carotid bifurcation model here investigated. Two WSS based blood-vessel wall interaction descriptors, the Time Averaged WSS (TAWSS), and the Oscillating Shear Index (OSI) were considered. A specific Lagrangian-based “bulk” blood flow descriptor, the Helical Flow Index (HFI) [2], was calculated in order to get a “measure” of the helical structure in the blood flow. In a first analysis the effects of the coupled 0D models on the 3D model are evaluated. The results obtained from the multiscale simulation are compared with the results of simulations performed using the same 3D model, but imposing a flow rate at internal carotid (ICA) outlet section equal to the maximum (60%) and the minimum (50%) flow division obtained out from ICA in the multiscale model simulation (the presence of the coupled 0D model gives variable internal/external flow division ratio during the cardiac cycle), and a stress free condition on the external carotid (ECA).

Effects of Cyclic Motion on Coronary Blood Flow

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Mahmudul Hasan ◽  
David A. Rubenstein ◽  
Wei Yin
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Blood Vessel ◽  
Coronary Blood Flow ◽  
Vessel Wall ◽  
Wall Stress ◽  
Blood Vessel Wall ◽  
Flow Parameters ◽  
Cyclic Motion

The goal of this study was to establish a computational fluid dynamics model to investigate the effect of cyclic motion (i.e., bending and stretching) on coronary blood flow. The three-dimensional (3D) geometry of a 50-mm section of the left anterior descending artery (normal or with a 60% stenosis) was constructed based on anatomical studies. To describe the bending motion of the blood vessel wall, arbitrary Lagrangian–Eularian methods were used. To simulate artery bending and blood pressure change induced stretching, the arterial wall was modeled as an anisotropic nonlinear elastic solid using the five-parameter Mooney–Rivlin hyperelastic model. Employing a laminar model, the flow field was solved using the continuity equations and Navier–Stokes equations. Blood was modeled as an incompressible Newtonian fluid. A fluid–structure interaction approach was used to couple the fluid domain and the solid domain iteratively, allowing force and total mesh displacement to be transferred between the two domains. The results demonstrated that even though the bending motion of the coronary artery could significantly affect blood cell trajectory, it had little effect on flow parameters, i.e., blood flow velocity, blood shear stress, and wall shear stress. The shape of the stenosis (asymmetric or symmetric) hardly affected flow parameters either. However, wall normal stresses (axial, circumferential, and radial stress) can be greatly affected by the blood vessel wall motion. The axial wall stress was significantly higher than the circumferential and radial stresses, as well as wall shear stress. Therefore, investigation on effects of wall stress on blood vessel wall cellular functions may help us better understand the mechanism of mechanical stress induced cardiovascular disease.

The role of stem cells in vein graft remodelling

2007 ◽  
Vol 35 (5) ◽  
pp. 895-899 ◽  
Author(s):  
Q. Xu
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Progenitor Cells ◽  
Vein Graft ◽  
Vessel Wall ◽  
Muscle Cells ◽  
Vein Segment ◽  
Graft Remodelling

The vessel wall is a dynamic tissue that undergoes positive remodelling in response to altered mechanical stress. A typical example is vein graft remodelling, because veins do not develop arteriosclerosis until a vein segment is grafted on to arteries. In this process, it was observed that vascular endothelial and smooth muscle cells of vein grafts die due to suddenly elevated blood pressure. This cell death is followed by endothelial regeneration. Central to this theme is the essential role played by EPCs (endothelial progenitor cells) in regenerating the lost endothelium. The mechanisms by which EPCs attach to the vessel wall and differentiate into mature endothelial cells involve increased chemokine production and laminar shear flow stimulation on the vessel wall. It seems that neo-endothelial cells derived from EPCs lack mature cell functions and express high levels of adhesion molecules resulting in LDL (low-density lipoprotein) penetration and mononuclear cell infiltration into the sub-endothelial space. Among infiltrated mononuclear cells, there are smooth muscle progenitors that proliferate and differentiate into smooth muscle cells. Meanwhile, stem cells present in the media and adventitia may also migrate into arteriosclerotic lesions via the vasa vasorum that are abundant in the diseased vessels. However, the molecular events leading to the homing, differentiation and maturation of stem/progenitor cells still needs elucidation. The present review attempts to update the progress in stem cell research related to the pathogenesis of vein graft arteriosclerosis or remodelling, focusing on the mechanisms by which stem/progenitor cells participate in the development of lesions, and to discuss the controversial issues and the future perspectives surrounding this research area.

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