Threshold Levels of Fluid Shear Promote Leukocyte Adhesion through Selectins (CD62L,P,E)

Leukocyte adhesion through L-selectin to peripheral node addressin (PNAd, also known as MECA-79 antigen), an L-selectin ligand expressed on high endothelial venules, has been shown to require a minimum level of fluid shear stress to sustain rolling interactions (Finger, E.B., K.D. Puri, R. Alon, M.B. Lawrence, V.H. von Andrian, and T.A. Springer. 1996. Nature (Lond.). 379:266–269). Here, we show that fluid shear above a threshold of 0.5 dyn/cm2 wall shear stress significantly enhances HL-60 myelocyte rolling on P- and E-selectin at site densities of 200/μm2 and below. In addition, gravitational force is sufficient to detach HL60 cells from P- and E-selectin substrates in the absence, but not in the presence, of flow. It appears that fluid shear–induced torque is critical for the maintenance of leukocyte rolling. K562 cells transfected with P-selectin glycoprotein ligand-1, a ligand for P-selectin, showed a similar reduction in rolling on P-selectin as the wall shear stress was lowered below 0.5 dyn/cm2. Similarly, 300.19 cells transfected with L-selectin failed to roll on PNAd below this level of wall shear stress, indicating that the requirement for minimum levels of shear force is not cell type specific. Rolling of leukocytes mediated by the selectins could be reinitiated within seconds by increasing the level of wall shear stress, suggesting that fluid shear did not modulate receptor avidity. Intravital microscopy of cremaster muscle venules indicated that the leukocyte rolling flux fraction was reduced at blood centerline velocities less than 1 mm/s in a model in which rolling is mediated by L- and P-selectin. Similar observations were made in L-selectin–deficient mice in which leukocyte rolling is entirely P-selectin dependent. Leukocyte adhesion through all three selectins appears to be significantly enhanced by a threshold level of fluid shear stress.

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Differential Responses of Endothelial Cells to Positive and Negative Wall Shear Stress Gradients

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19535 ◽

2010 ◽

Author(s):

Jennifer Dolan ◽

Sukhjinder Singh ◽

Hui Meng ◽

John Kolega

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Vessel Wall ◽

Fluid Shear Stress ◽

Cerebral Aneurysms ◽

In Vivo Studies ◽

Outer Side ◽

Fluid Shear ◽

Wall Shear

Cerebral aneurysms tend to develop at bifurcation apices or the outer side of curved vessels where the blood vessel wall experiences complex hemodynamics. In vivo studies have recently revealed that the initiation of cerebral aneurysms is confined to a well-defined hemodynamic microenvironment. Specifically aneurysms form where the vessel wall experiences high fluid shear stress (wall shear stress, WSS) and flow is accelerating, so that the wall is exposed to a positive spatial gradient in the fluid shear stress (wall shear stress gradient, WSSG)[1,2]. Closer examination of such in vivo studies reveals that exposure of the vessel wall to equally high WSS in the presence of decelerating flow, that is, negative WSSG, does not result in aneurysm-like remodeling.

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An In Vitro Comparative Study of Intracanal Fluid Motion and Wall Shear Stress Induced by Ultrasonic and Polymer Rotary Finishing Files in a Simulated Root Canal Model

ISRN Dentistry ◽

10.5402/2012/764041 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Jon Koch ◽

John Borg ◽

Abby Mattson ◽

Kris Olsen ◽

James Bahcall

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Root Canal ◽

High Speed ◽

Fluid Shear Stress ◽

Distilled Water ◽

Axial Motion ◽

Fluid Shear ◽

Wall Shear

Objective. This in vitro study compared the flow pattern and shear stress of an irrigant induced by ultrasonic and polymer rotary finishing file activation in an acrylic root canal model. Flow visualization analysis was performed using an acrylic canal filled with a mixture of distilled water and rheoscopic fluid. The ultrasonic and polymer rotary finishing file were separately tested in the canal and activated in a static position and in a cyclical axial motion (up and down). Particle movement in the fluid was captured using a high-speed digital camera and DaVis 7.1 software. The fluid shear stress analysis was performed using hot film anemometry. A hot-wire was placed in an acrylic root canal and the canal was filled with distilled water. The ultrasonic and polymer rotary finishing files were separately tested in a static position and in a cyclical axial motion. Positive needle irrigation was also tested separately for fluid shear stress. The induced wall shear stress was measured using LabVIEW 8.0 software.

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Enhanced wall shear stress prevents obstruction by astrocytes in ventricular catheters

Journal of The Royal Society Interface ◽

10.1098/rsif.2019.0884 ◽

2020 ◽

Vol 17 (168) ◽

pp. 20190884

Author(s):

S. Lee ◽

N. Kwok ◽

J. Holsapple ◽

T. Heldt ◽

L. Bourouiba

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Fluid Shear Stress ◽

Stellate Cell ◽

Critical Threshold ◽

Ventricular Catheter ◽

Fluid Shear ◽

Catheter Design ◽

Ventricular Catheters ◽

Wall Shear

The treatment of hydrocephalus often involves the placement of a shunt catheter into the cerebrospinal ventricular space, though such ventricular catheters often fail by tissue obstruction. While diverse cell types contribute to the obstruction, astrocytes are believed to contribute to late catheter failure that can occur months after shunt insertion. Using in vitro microfluidic cultures of astrocytes, we show that applied fluid shear stress leads to a decrease of cell confluency and the loss of their typical stellate cell morphology. Furthermore, we show that astrocytes exposed to moderate shear stress for an extended period of time are detached more easily upon suddenly imposed high fluid shear stress. In light of these findings and examining the range of values of wall shear stress in a typical ventricular catheter through computational fluid dynamics (CFD) simulation, we find that the typical geometry of ventricular catheters has low wall shear stress zones that can favour the growth and adhesion of astrocytes, thus promoting obstruction. Using high-precision direct flow visualization and CFD simulations, we discover that the catheter flow can be formulated as a network of Poiseuille flows. Based on this observation, we leverage a Poiseuille network model to optimize ventricular catheter design such that the distribution of wall shear stress is above a critical threshold to minimize astrocyte adhesion and growth. Using this approach, we also suggest a novel design principle that not only optimizes the wall shear stress distribution but also eliminates a stagnation zone with low wall shear stress, which is common to current ventricular catheters.

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The Relationship Between the Arterial Geometry and Wall Shear Stress in the Vertebrobasilar System

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2019-10866 ◽

2019 ◽

Author(s):

Fangjia Pan ◽

Hitomi Anzai ◽

Shunji Mugikura ◽

Ko Kitamura ◽

Makoto Ohta

Keyword(s):

Risk Factors ◽

Shear Stress ◽

Wall Shear Stress ◽

Fluid Shear Stress ◽

Arterial Disease ◽

Patient Specific ◽

Vertebrobasilar System ◽

Basilar Arteries ◽

Computational Fluid Dynamics Cfd ◽

Wall Shear

Abstract Vertebrobasilar atherosclerosis is an arterial disease; without successful treatment, it has a mortality rate approximately 80%–95%. Thus, predicting risk factors of vertebrobasilar atherosclerosis is of utmost importance. Previous studies have demonstrated that wall shear stress (WSS) contributes to atherosclerosis. In addition, geometry and WSS are correlated. The present study focuses on the description of equation using detailed relationship between arterial geometry and WSS in the vertebrobasilar system (VBS); magnetic resonance (MR) imaging with computational fluid dynamics (CFD) was used for the analysis. Using constructed patient-specific models, WSS of basilar arteries (BAs) was calculated and then analyzed with morphological parameters. According to the statistical results, both the area and curvature of BAs are associated with WSS. Based on the relations, a liner fitted equation can be proposed. As this study is underway, more precise evaluation of the correlation between morphology and fluid shear stress could help predict risk factors and select treatment methods for this arterial disease.

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Assessment with clinical data of a coupled bio-hemodynamics numerical model to predict leukocyte adhesion in coronary arteries

Scientific Reports ◽

10.1038/s41598-021-92084-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Umberto Ciri ◽

Ruth L. Bennett ◽

Rita Bhui ◽

David S. Molony ◽

Habib Samady ◽

...

Keyword(s):

Shear Stress ◽

Numerical Model ◽

Wall Shear Stress ◽

Coronary Arteries ◽

Clinical Data ◽

Leukocyte Adhesion ◽

Three Dimensional ◽

High Adhesion ◽

Wall Shear ◽

Stress Dependent

AbstractNumerical simulations of coupled hemodynamics and leukocyte transport and adhesion inside coronary arteries have been performed. Realistic artery geometries have been obtained for a set of four patients from intravascular ultrasound and angiography images. The numerical model computes unsteady three-dimensional blood hemodynamics and leukocyte concentration in the blood. Wall-shear stress dependent leukocyte adhesion is also computed through agent-based modeling rules, fully coupled to the hemodynamics and leukocyte transport. Numerical results have a good correlation with clinical data. Regions where high adhesion is predicted by the simulations coincide to a good approximation with artery segments presenting plaque increase, as documented by clinical data from baseline and six-month follow-up exam of the same artery. In addition, it is observed that the artery geometry and, in particular, the tortuosity of the centerline are a primary factor in determining the spatial distribution of wall-shear stress, and of the resulting leukocyte adhesion patterns. Although further work is required to overcome the limitations of the present model and ultimately quantify plaque growth in the simulations, these results are encouraging towards establishing a predictive methodology for atherosclerosis progress.

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Control of blood vessel structure: insights from theoretical models

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00752.2004 ◽

2005 ◽

Vol 288 (3) ◽

pp. H1010-H1015 ◽

Cited By ~ 46

Author(s):

A. R. Pries ◽

T. W. Secomb

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Fluid Shear Stress ◽

Circumferential Stress ◽

Wall Stress ◽

Functional Requirements ◽

Vascular Networks ◽

Structural Adaptation ◽

Local Conditions ◽

Wall Shear

Blood vessels are capable of continuous structural adaptation in response to changing local conditions and functional requirements. Theoretical modeling approaches have stimulated the development of new concepts in this area and have allowed investigation of the complex relations between adaptive responses to multiple stimuli and resulting functional properties of vascular networks. Early analyses based on a minimum-work principle predicted uniform wall shear stress in all segments of vascular networks and led to the concept that vessel diameter is controlled by a feedback system based on responses to wall shear stress. Vascular reactions to changes in transmural pressure suggested feedback control of circumferential wall stress. However, theoretical simulations of network adaptation showed that these two mechanisms cannot, by themselves, lead to stable and realistic network structures. Models combining reactions to fluid shear stress, circumferential stress, and metabolic status of tissue, with propagation of stimuli upstream and downstream along vascular segments, are needed to explain stable and functionally adequate adaptation of vascular structure. Such models provide a basis for predicting the response of vascular segments exposed to altered conditions, as, for example, in vascular grafts.

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