An Apparatus to Study the Response of Cultured Endothelium to Shear Stress

1986 ◽  
Vol 108 (4) ◽  
pp. 332-337 ◽  
Author(s):  
R. F. Viggers ◽  
A. R. Wechezak ◽  
L. R. Sauvage
Keyword(s):  
Finite Element ◽  
Endothelial Cells ◽  
Shear Stress ◽  
Laminar Flow ◽  
Fluid Shear Stress ◽  
Shear Stresses ◽  
Parallel Plates ◽  
Dimensional Flow ◽  
Wide Range ◽  
Wall Shear

An apparatus which has been developed to study the response of cultured endothelial cells to a wide range of shear stress levels is described. Controlled laminar flow through a rectangular tube was used to generate fluid shear stress over a cell-lined coverslip comprising part of one wall of the tube. A finite element method was used to calculate shear stresses corresponding to cell position on the coverslip. Validity of the finite element analysis was demonstrated first by its ability to generate correctly velocity profiles and wall shear stresses for laminar flow in the entrance region between infinitely wide parallel plates (two-dimensional flow). The computer analysis also correctly predicted values for pressure difference between two points in the test region of the apparatus for the range of flow rates used in these experiments. These predictions thus supported the use of such an analysis for three-dimensional flow. This apparatus has been used in a series of experiments to confirm its utility for testing applications. In these studies, endothelial cells were exposed to shear stresses of 60 and 128 dynes/cm2. After 12 hr at 60 dynes/cm2, cells became aligned with their longitudinal axes parallel to the direction of flow. In contrast, cells exposed to 128 dynes/cm2 required 36 hr to achieve a similar reorientation. Interestingly, after 6 hr at 128 dynes/cm2, specimens passed through an intermediate phase in which cells were aligned perpendicular to flow direction. Because of its ease and use and the provided documentation of wall shear stress, this flow chamber should prove to be a valuable tool in endothelial research related to atherosclerosis.

scholarly journals Fluid shear stress modulates surface expression of adhesion molecules by endothelial cells

Blood ◽  
1995 ◽  
Vol 85 (7) ◽  
pp. 1696-1703 ◽  
Author(s):  
M Morigi ◽  
C Zoja ◽  
M Figliuzzi ◽  
M Foppolo ◽  
G Micheletti ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Laminar Flow ◽  
Fluid Shear Stress ◽  
Leukocyte Adhesion ◽  
Interleukin 1 ◽  
Static Condition ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Interleukin 1 Beta

We investigated the effect of hemodynamic shear forces on the expression of adhesive molecules, E-selectin, and intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells (HUVEC) exposed to laminar (8 dynes/cm2) or turbulent shear stress (8.6 dynes/cm2 average), or to a static condition. Laminar flow induced a significant time-dependent increase in the surface expression of ICAM-1, as documented by flow cytometry studies. Endothelial cell surface expression of ICAM-1 in supernatants of HUVEC exposed to laminar flow was not modified, excluding the possibility that HUVEC exposed to laminar flow synthetize factors that upregulate ICAM-1. The effect of laminar flow was specific for ICAM-1, while E-selectin expression was not modulated by the flow condition. Turbulent flow did not affect surface expression of either E-selectin or ICAM-1. To evaluate the functional significance of the laminar-flow-induced increase in ICAM-1 expression, we studied the dynamic interaction of total leukocyte suspension with HUVEC exposed to laminar flow (8 dynes/cm2 for 6 hours) in a parallel-plate flow chamber or to static condition. Leukocyte adhesion to HUVEC pre-exposed to flow was significantly enhanced, compared with HUVEC maintained in static condition (233 +/- 67 v 43 +/- 16 leukocytes/mm2, respectively), and comparable with that of interleukin-1 beta treated HUVEC. Mouse monoclonal antibody anti-ICAM-1 completely blocked flow-induced upregulation of leukocyte adhesion. Interleukin-1 beta, which upregulated E-selectin expression, caused leukocyte rolling on HUVEC that was significantly lower on flow- conditioned HUVEC and almost absent on untreated static endothelial cells. Thus, laminar flow directly and selectively upregulates ICAM-1 expression on the surface of endothelial cells and promotes leukocyte adhesion. These data are relevant to the current understanding of basic mechanisms that govern local inflammatory reactions and tissue injury.

Effects of Fluid Shear Stress on Endothelial Cell Invasion Into Three-Dimensional Matrices

2007 ◽  
Author(s):  
Hojin Kang ◽  
Kayla J. Bayless ◽  
Roland Kaunas
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Endothelial Cell ◽  
Cell Invasion ◽  
Fluid Shear Stress ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Shear Stresses ◽  
Collagen Gels ◽  
Fluid Shear

We have previously developed a cell culture model to study the effects of angiogenic factors, such as sphingosine-1-phosphate (S1P), on the invasion of endothelial cells into the underlying extracellular matrix. In addition to biochemical stimuli, vascular endothelial cells are subjected to fluid shear stress due to blood flow. The present study is aimed at determining the effects of fluid shear stress on endothelial cell invasion into collagen gels. A device was constructed to apply well-defined fluid shear stresses to confluent human umbilical vein endothelial cells (HUVECs) seeded on collagen gels. Fluid shear stress induced significant increases in cell invasion with a maximal induction at ∼5 dyn/cm2. These results provide evidence that fluid shear stress is a significant stimulus for endothelial cell invasion and may play a role in regulating angiogenesis.

Analysis of Flow Disturbance in a Stenosed Carotid Artery Bifurcation Using Two-Equation Transitional and Turbulence Models

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
F. P. P. Tan ◽  
G. Soloperto ◽  
S. Bashford ◽  
N. B. Wood ◽  
S. Thom ◽  
...  
Keyword(s):  
Shear Stress ◽  
Carotid Artery ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Turbulence Models ◽  
Carotid Bifurcation ◽  
Patient Specific ◽  
Shear Stresses ◽  
Zone Length ◽  
Wall Shear

In this study, newly developed two-equation turbulence models and transitional variants are employed for the prediction of blood flow patterns in a diseased carotid artery where the growth, progression, and structure of the plaque at rupture are closely linked to low and oscillating wall shear stresses. Moreover, the laminar-turbulent transition in the poststenotic zone can alter the separation zone length, wall shear stress, and pressure distribution over the plaque, with potential implications for stresses within the plaque. Following the validation with well established experimental measurements and numerical studies, a magnetic-resonance (MR) image-based model of the carotid bifurcation with 70% stenosis was reconstructed and simulated using realistic patient-specific conditions. Laminar flow, a correlation-based transitional version of Menter’s hybrid k‐ϵ∕k‐ω shear stress transport (SST) model and its “scale adaptive simulation” (SAS) variant were implemented in pulsatile simulations from which analyses of velocity profiles, wall shear stress, and turbulence intensity were conducted. In general, the transitional version of SST and its SAS variant are shown to give a better overall agreement than their standard counterparts with experimental data for pulsatile flow in an axisymmetric stenosed tube. For the patient-specific case reported, the wall shear stress analysis showed discernable differences between the laminar flow and SST transitional models but virtually no difference between the SST transitional model and its SAS variant.

Wall Shear Stress Measurements in an Arterial Flow Bioreactor

2011 ◽  
Author(s):  
Elizabeth Voigt ◽  
Cara Buchanan ◽  
Jaime Schmieg ◽  
M. Nichole Rylander ◽  
Pavlos Vlachos
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Vascular System ◽  
Vascular Endothelial Cells ◽  
Shear Stresses ◽  
Bulk Flow Rate ◽  
Wall Shear ◽  
Endothelial Cell Response ◽  
And Function

Physiological flow parameters such as pressure and stress inside the vascular system strongly influence the physiology and function of vascular endothelial cells [1]. Variations in the shear stress experienced by endothelial cells affect morphology, alignment with the flow, mechanical strength, rate of proliferation, and gene expression [2]. Although it is known that these factors are dependent on the hemodynamics of the flow, the relationship has not been accurately quantified. In vitro bioreactor flow loops have been developed to simulate vascular flow for tissue conditioning and measurement of the endothelial cell response to varying shear [3–5]; however, wall shear stresses (WSS) have been estimated from the bulk flow rate by assuming Poiseuille flow [2, 6]. Due to the pulsatility of the flow, biochemical interactions, and the typically short vessel length, this assumption is fundamentally incorrect; however, the level of inaccuracy has not been quantified.

Wall Pressure and Shear Stress Variations in a 90-Deg Bifurcation During Pulsatile Laminar Flow

1991 ◽  
Vol 113 (1) ◽  
pp. 111-115 ◽  
Author(s):  
J. M. Khodadadi
Keyword(s):  
Shear Stress ◽  
Laminar Flow ◽  
Wall Shear Stress ◽  
Cross Sections ◽  
Adverse Pressure Gradient ◽  
Wall Pressure ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Navier Stokes Equation ◽  
Wall Shear

Wall pressure distribution and shear stress fields for pulsatile laminar flow in a 90-degree bifurcation with rectangular cross sections are evaluated using the results of the numerical solution of the Navier-Stokes equation. The extent of the adverse pressure gradient on the bottom wall of the main duct and the upstream wall of the branch closely correlate to the behavior of the two dynamic recirculation zones which are formed on these two walls. Multiple zones of high and low shear stresses at various sites in the bifurcation are observed. The extent of the fluctuations of the maximum and minimum shear stress is identified. Next-to-the-wall laser Doppler anemometer velocity measurements are used to estimate the shear stress distribution on the walls. In general, qualitative agreement between the experimental and computed wall shear stress values is observed. The variation of the wall shear stress in the vicinity of the branch is discussed in light of the highly perturbed flow field.

Development of Microfluidic Chips to Study the Effects of Shear Stress on Cell Functions

2010 ◽  
Author(s):  
Jianbin Wang ◽  
Jinseok Heo ◽  
Susan Z. Hua
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Cellular Systems ◽  
Shear Stresses ◽  
Microfluidic Chips ◽  
Fluid Shear ◽  
Cell Functions ◽  
Culture Cells ◽  
Wide Range ◽  
On Chip

Fluid shear stress has profound effect on many cell functions, including proliferation, migration, transport, and gene expression. Cellular systems such as endothelial cells in heart artery and epithelial cells in kidney tubule are constantly subject to fluid flow. We have developed a series of microfluidic chips that generate a wide range and modes of shear stresses within a perfusion chamber, enabling us to culture cells on chip and examine the effects of shear stress on cell growth and cell functions.

Exposure to fluid shear stress modulates the ability of endothelial cells to recruit neutrophils in response to tumor necrosis factor-α: a basis for local variations in vascular sensitivity to inflammation

Blood ◽  
2003 ◽  
Vol 102 (8) ◽  
pp. 2828-2834 ◽  
Author(s):  
Sajila Sheikh ◽  
G. Ed Rainger ◽  
Zoe Gale ◽  
Mahbub Rahman ◽  
Gerard B. Nash
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Fluid Shear Stress ◽  
Vascular Endothelial Cells ◽  
Shear Stresses ◽  
Factor Α ◽  
Necrosis Factor

Abstract Vascular endothelial cells are able to sense changes in the forces acting on them and respond, for instance, by modifying expression of a range of genes. However, there is little information on how such responses are integrated to modify homeostatic functions. We hypothesized that different shear stresses experienced in different regions of the circulation might influence endothelial sensitivity to inflammatory stimuli. We cultured human endothelial cells in tubes and exposed them for varying periods to shear stresses ranging from those typically found in postcapillary venules to those in arteries. When tumor necrosis factor-α was included in the flow cultures, we found startling differential effects of shear stress on the ability of endothelial cells to induce adhesion and migration of flowing neutrophils. Compared with static cultures, endothelial cells cultured at low shear stress (0.3 Pa) captured similar numbers of neutrophils but failed to induce their transendothelial migration. After exposure of endothelial cells to high shear stress (1.0 or 2.0 Pa), capture of neutrophils was largely ablated. The modification in response was detectable after 4 hours of exposure to flow but was much greater after 24 hours. From analysis of gene expression, loss of capture or migration was attributable to reduction in tumor necrosis factor–induced expression of selectins or CXC-chemokines, respectively. Thus, conditioning of endothelial cells by different flow environments may underlie variations in susceptibility to inflammation between different tissues or parts of the vascular tree.

The Dynamic Response of Vascular Endothelial Cells to Fluid Shear Stress

1981 ◽  
Vol 103 (3) ◽  
pp. 177-185 ◽  
Author(s):  
C. F. Dewey ◽  
S. R. Bussolari ◽  
M. A. Gimbrone ◽  
P. F. Davies
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Endothelial Cell ◽  
Dynamic Response ◽  
Fluid Shear Stress ◽  
Vascular Endothelial Cells ◽  
Shear Stresses ◽  
Vascular Endothelial ◽  
Fluid Shear ◽  
Cell Functions

We have developed an in-vitro system for studying the dynamic response of vascular endothelial cells to controlled levels of fluid shear stress. Cultured monolayers of bovine aortic endothelial cells are placed in a cone-plate apparatus that produces a uniform fluid shear stress on replicate samples. Subconfluent endothelial cultures continuously exposed to 1–5 dynes/cm2 shear proliferate at a rate comparable to that of static cultures and reach the same saturation density (≃ 1.0–1.5 × 105 cells/cm2). When exposed to a laminar shear stress of 5–10 dynes/cm2, confluent monolayers undergo a time-dependent change in cell shape from polygonal to ellipsoidal and become uniformly oriented with flow. Regeneration of linear “wounds” in confluent monolayer appears to be influenced by the direction of the applied force. Preliminary studies indicate that certain endothelial cell functions, including fluid endocytosis, cytoskeletal assembly and nonthrombogenic surface properties, also are sensitive to shear stress. These observations suggest that fluid mechanical forces can directly influence endothelial cell structure and function. Modulation of endothelial behavior by fluid shear stresses may be relevant to normal vessel wall physiology, as well as the pathogenesis of vascular diseases, such as atherosclerosis.

scholarly journals Finite Element Modelling of Pulsatile Blood Flow in Idealized Model of Human Aortic Arch: Study of Hypotension and Hypertension

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Paritosh Vasava ◽  
Payman Jalali ◽  
Mahsa Dabagh ◽  
Pertti J. Kolari
Keyword(s):  
Finite Element ◽  
Blood Flow ◽  
Shear Stress ◽  
Aortic Arch ◽  
Human Aorta ◽  
Shear Stresses ◽  
Pulsatile Blood Flow ◽  
Increased Risk ◽  
Pulsatile Pressure ◽  
Wall Shear

A three-dimensional computer model of human aortic arch with three branches is reproduced to study the pulsatile blood flow with Finite Element Method. In specific, the focus is on variation of wall shear stress, which plays an important role in the localization and development of atherosclerotic plaques. Pulsatile pressure pulse is used as boundary condition to avoid flow entry development, and the aorta walls are considered rigid. The aorta model along with boundary conditions is altered to study the effect of hypotension and hypertension. The results illustrated low and fluctuating shear stress at outer and inner wall of aortic arch, proximal wall of branches, and entry region. Despite the simplification of aorta model, rigid walls and other assumptions results displayed that hypertension causes lowered local wall shear stresses. It is the sign of an increased risk of atherosclerosis. The assessment of hemodynamics shows that under the flow regimes of hypotension and hypertension, the risk of atherosclerosis localization in human aorta may increase.

Shear Stress Induced Increase in the Forced (UL)VWF Domain Unfolding Is Non-Proteolytically Regulated by ADAMTS-13

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3929-3929
Author(s):  
Ching-Hwa Kiang ◽  
Eric Botello ◽  
Hiuwan Choi ◽  
Jing-fei Dong
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Proteolytic Activity ◽  
Fluid Shear Stress ◽  
Peak Force ◽  
Shear Stresses ◽  
Fluid Shear ◽  
Platelet Receptor ◽  
High Fluid ◽  
Adhesion Activity

Abstract Hemostasis is initiated by tethering platelets to the site of vessel injury, a process mediated by the interaction of the GP Ib-IX-V complex on platelets and von Willebrand Factor (VWF) in the subendothelial matrix. The adhesion activity of VWF depends on the multimer size: those freshly secreted from activated endothelial cells are ultra-large (UL) and overly adhesive, capable of forming spontaneous high strength bonds with the platelet receptor. In contrast, VWF multimers circulating in blood (pVWF) is required to be activated by high fluid shear stress or modulators in order to bind and aggregate platelets. Shear stress has previously been demonstrated to convert globular shape VWF multimers to elongated rope-like structures, but whether this structural change correlates with VWF adhesion activity remains largely unknown. We have showed that, upon secretion, ULVWF multimers form long string-like structures on activated endothelial cells that can be viewed under a regular light microscope, suggesting laterally association between ULVWF multimers. Furthermore, pVWF multimers can be induced to laterally associate with each other by shear stress, potentially resulting in the formation of VWF fibrils. We hypothesize that by forming laterally associated strings, ULVWF multimers require a greater physical force to unfold as compared to pVWF, which can be induced to form fibrillar structures that become more resistant to force-induced unfolding. Here, we present experimental data to support this hypothesis. First, we found that shear stress covalently aggregated pVWF multimers and the process was prevented rADAMTS-13 or disulfide reducing agents. VWF multimers were not cleaved by ADAMTS-13 under this experimental condition, suggesting a non-proteolytic activity. Second, when pVWF multimers are captured and subjected to physical pulling force on an atomic force microscope, the length of VWF multimers extended sequentially in response to increasing force. Plasma VWF multimers were unfolded at the peak forces of 115 pN, which increased to 153 pN after they were exposed to a pathological level of shear stress (100 dyn/cm2) for 3 min at 37°C. The peak force required to unfold pVWF after shear exposure (153 pN) was very similar to that of ULVWF multimers (152 pN). Third, recombinant (r) ADAMTS-13 did not reduce the peak force for unfolding pVWF multimers (115 pN) before but it lessened the increase in magnitude in the peak force required to unfold pVWF exposed to shear stress. This ADAMTS-13 activity was not inhibited by 5 mM of EDTA. Similarly, the peak force for unfolding ULVWF multimers was reduced from 152 pN to 127 pN when ULVWF was pulled in the presence of an equal molar concentration of rADAMTS-13. Taken together, these data demonstrate that shear stress significantly increases the peak force required to unfold pVWF multimers to the levels similar to ULVWF multimers, likely by promoting the formation of laterally associated VWF fibrils. ADAMTS-13 prevents the shear-induced increase in the peak force for unfolding sheared pVWF multimers, independent of the VWF proteolytic activity of the metalloprotease. The results reveal a mechanism for shear-induced VWF activation. They also suggest that ADAMTS-13 contains a non-proteolytic activity that plays a role in cleaving ULVWF strings and preventing pVWF multimers to be activated by lateral association induced by high fluid shear stresses.

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