scholarly journals A cell-based sensor of fluid shear stress for microfluidics

Lab on a Chip ◽  
2015 ◽  
Vol 15 (6) ◽  
pp. 1563-1573 ◽  
Author(s):  
Sarvesh Varma ◽  
Joel Voldman
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Flow Conditions ◽  
Fluid Shear ◽  
Nih3t3 Cells ◽  
A Cell ◽  
The Impact

We present a cell-based sensor embedded in NIH3T3 cells that fluoresces upon the application of fluid shear stress (FSS), as a simple and versatile method to assess the impact of various microsystem flow conditions on cell health.

ADAMTS-13 Has a Disulfide Bond Reduction Activity on Von Willebrand Factor

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3934-3934
Author(s):  
Zhou Zhou ◽  
Hiuwan Choi ◽  
Zhenyin Tao ◽  
Khatira Aboulfatova ◽  
Leticia Nolasco ◽  
...  
Keyword(s):  
Shear Stress ◽  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Fluid Shear Stress ◽  
Flow Conditions ◽  
Fluid Shear ◽  
Disulfide Exchange ◽  
High Fluid ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Von Willebrand factor (VWF) multimers tether platelets to subendothelium exposed at the site of vessel injury to initiate the bleeding arrest. Upon synthesized, VWF multimers are either constitutively secreted or packed into the storage granules, where they are enriched in ultra-large (UL) multimers that are active in forming spontaneous high strength bonds with the GP Ib-IX-V complex on platelets. This hyper-reactivity of ULVWF multimers is in contrast to VWF multimers circulating in plasma (pVWF) that need to be activated by modulators or high fluid shear stress to aggregate platelets. The biochemical and structural bases for the functional difference between ULVWF and pVWF multimers are not known. We have recently shown that a portion of pVWF, but not ULVWF multimers contain surface exposed free thiols in the D3 and C domains. High fluid shear stress promotes the formation of new disulfide bonds utilizing the thiols to enhance VWF binding to platelets, suggesting that the shear-induced thiol-disulfide exchange may serve as a mechanism for the shear-induced activation of pVWF multimers. ULVWF freshly secreted from endothelial cells forms string-like structures that can be elongated by pVWF multimers through a covalent means. The different thiol distribution between ULVWF and its plasma counterpart may be caused by the former being cleaved by the zinc metalloprotease ADAMTS-13 at a single peptide bond of Y1065-M1606 in the A2 domain. Here, we provide several lines of evidence to demonstrate that ADAMTS-13 also contains a reductase-like activity that plays a role in cleaving ULVWF strings under flow conditions and maintaining circulating VWF multimers in an inactive (thiol) state. First, more than 90% of pVWF non-specifically adhered to the surface of a cone-plate viscometer when pVWF was exposed to a pathological high shear stress of 100 dyn/cm2 for 3 min at 37°C. The adhesion was prevented by recombinant (r) ADAMTS-13 or a truncation mutant that lacked the catalytic domain. Second, rADAMTS-13 prevented the shear-induced thiol-disulfide exchange so that free thiols remained in pVWF after shear exposure. This activity was not blocked by 5 mM of EDTA and was detectable with the N-terminal truncated mutant, suggesting that it is independent of the VWF-cleaving activity. We further found that rADAMTS-13 was able to reduce disulfide bonds, converting the disulfide forms of sheared pVWF to the thiol forms, suggesting that ADAMTS-13 prevents the thiol-disulfide exchange by disulfide bond reduction, not a steric hindered effect. Third, ADAMTS-13 contains the surface exposed thiol(s) that is necessary for the metalloprotease to attack and break a disulfide bond. Unlike VWF multimers, these thiols remained after the metalloprotease was exposed to a pathological high shear stress of 100 dyn/cm2. Fourth, using a series of N- and C-terminal truncation mutants, we located the thiol(s) potentially involved in VWF reduction to the 2nd to 8th TSP-1 motifs and CUB-1 domain of ADAMTS-13. Finally, ethylmaleimide (NEM), which blocks free thiols, did not inhibit rADAMTS-13 to cleave pVWF multimers under static conditions and in the presence of urea and barium. NEM-treated rADAMTS-13 retained only 27.5±4.9% activity in cleaving ULVWF strings under flow conditions as compared to untreated enzyme. These data characterizes a novel mechanism that plays a regulatory role in cleaving ULVWF strings and maintaining the circulating pVWF multimers in inactive forms.

scholarly journals Coupled CFD-DEM modelling to predict how EPS affects bacterial biofilm deformation, recovery and detachment under flow conditions

2021 ◽  
Author(s):  
YUQING XIA ◽  
Pahala Jayathilake ◽  
Bowen Li ◽  
Paolo Zuliani ◽  
David Deehan ◽  
...  
Keyword(s):  
Shear Stress ◽  
Extracellular Polymeric Substances ◽  
Fluid Shear Stress ◽  
Mechanical Stability ◽  
Fluid Dynamic ◽  
Bacterial Biofilm ◽  
Flow Conditions ◽  
Fluid Shear ◽  
Biofilm Detachment ◽  
Cleaning Cycle

The deformation and detachment of bacterial biofilm are related to the structural and mechanical properties of the biofilm itself. Extracellular polymeric substances (EPS) play an important role on keeping the mechanical stability of biofilms. The understanding of biofilm mechanics and detachment can help to reveal biofilm survival mechanisms under fluid shear and provide insight about what flows might be needed to remove biofilm in a cleaning cycle or for a ship to remove biofilms. However, how the EPS may affect biofilm mechanics and its deformation in flow conditions remains elusive. To address this, a coupled computational fluid dynamic – discrete element method (CFD-DEM) model was developed. The mechanisms of biofilm detachment, such as erosion and sloughing have been revealed by imposing hydrodynamic fluid flow at different velocities and loading rates. The model, which also allows adjustment of the proportion of different functional group of microorganisms in the biofilm, enables the study of the contribution of EPS towards biofilm resistance to fluid shear stress. Furthermore, the stress-strain curves during biofilm deformation have been captured by loading and unloading fluid shear stress to study the viscoelastic properties of the biofilm.

Glutathione regulates integrin αIIbβ3-mediated cell adhesion under flow conditions

2008 ◽  
Vol 100 (05) ◽  
pp. 857-863 ◽  
Author(s):  
Chalmette Ball ◽  
K. Vinod Vijayan ◽  
Trung Nguyen ◽  
Kim Anthony ◽  
Paul F. Bray ◽  
...  
Keyword(s):  
Shear Stress ◽  
Platelet Aggregation ◽  
Fluid Shear Stress ◽  
Platelet Rich Plasma ◽  
Early Observation ◽  
Flow Conditions ◽  
Fluid Shear ◽  
Physical Force ◽  
Integrin Αiibβ3 ◽  
Static Conditions

SummaryThe platelet integrin αIIbβ3 mediates the final step of platelet aggregation that requires pre-activation through an inside-out signal initiated by agonists. Experiments conducted under static conditions using platelet-rich plasma show that platelet activation and adhesion activity of αIIbβ3 are regulated by glutathione (GSH-GSSG) redox potential.However,it remains unclear as to whether GSH-GSSG exerts its regulatory role in platelets by direct targeting of αIIbβ3 or intracellular signals that activate the integrin. A role of fluid shear stress is also not known. We examined the effects of GSH-GSSG on the adhesion of CHO cells expressing two HPA variants of human αIIbβ3 to the immobilized fibrinogen and von Willebrand factor (VWF) under flow conditions. GSH-GSSG dose-dependently reduced the number of adherent cells to fibrinogen and VWF under 2.5 dyn/cm2 of shear stress, a physical force calculated to be 110 dyne on platelets. GSH treatment also abolished the hyperadhesion activity of cells expressing the Pro33 variant of αIIbβ3.The inhibition was also observed with washed platelets. The data differ from the early observation that GSH enhanced platelet aggregation induced by sub-threshold concentrations of platelet agonists. The results suggest that GSH may have distinct effects on agonist-induced αIIbβ3 activation and on the αIIbβ3-fibrinogen or αIIbβ3-VWF bonds when exposed to fluid shear stress. They further suggest that the HPA phenotype may be redox-regulated.

scholarly journals The Cycling of Intracellular Calcium Released in Response to Fluid Shear Stress Is Critical for Migration-Associated Actin Reorganization in Eosinophils

Cells ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 157
Author(s):  
Kiho Son ◽  
Amer Hussain ◽  
Roma Sehmi ◽  
Luke Janssen
Keyword(s):  
Shear Stress ◽  
Calcium Signaling ◽  
Intracellular Calcium ◽  
Actin Polymerization ◽  
Calcium Release ◽  
Fluid Shear Stress ◽  
Morphological Changes ◽  
Calcium Flux ◽  
Fluid Shear ◽  
The Impact

The magnitude of eosinophil mobilization into respiratory tissues drives the severity of inflammation in several airway diseases. In classical models of leukocyte extravasation, surface integrins undergo conformational switches to high-affinity states via chemokine binding activation. Recently, we learned that eosinophil integrins possess mechanosensitive properties that detect fluid shear stress, which alone was sufficient to induce activation. This mechanical stimulus triggered intracellular calcium release and hallmark migration-associated cytoskeletal reorganization including flattening for increased cell–substratum contact area and pseudopodia formation. The present study utilized confocal fluorescence microscopy to investigate the effects of pharmacological inhibitors to calcium signaling and actin polymerization pathways on shear stress-induced migration in vitro. Morphological changes (cell elongation, membrane protrusions) succeeded the calcium flux in untreated eosinophils within 2 min, suggesting that calcium signaling was upstream of actin cytoskeleton rearrangement. The inhibition of ryanodine receptors and endomembrane Ca2+-ATPases corroborated this idea, indicated by a significant increase in time between the calcium spike and actin polymerization. The impact of the temporal link is evident as the capacity of treated eosinophils to move across fibronectin-coated surfaces was significantly hampered relative to untreated eosinophils. Furthermore, we determined that the nature of cellular motility in response to fluid shear stress was nondirectional.

scholarly journals Three dimensional modeling of biologically relevant fluid shear stress in human renal tubule cells mimics in vivo transcriptional profiles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emily J. Ross ◽  
Emily R. Gordon ◽  
Hanna Sothers ◽  
Roshan Darji ◽  
Oakley Baron ◽  
...  
Keyword(s):  
Gene Expression ◽  
Shear Stress ◽  
Proximal Tubule ◽  
Fluid Shear Stress ◽  
Renal Diseases ◽  
Genome Wide Association Studies ◽  
Fluid Shear ◽  
Biologically Relevant ◽  
Tubule Cells ◽  
The Impact

AbstractThe kidney proximal tubule is the primary site for solute reabsorption, secretion and where kidney diseases can originate, including drug-induced toxicity. Two-dimensional cell culture systems of the human proximal tubule cells (hPTCs) are often used to study these processes. However, these systems fail to model the interplay between filtrate flow, fluid shear stress (FSS), and functionality essential for understanding renal diseases and drug toxicity. The impact of FSS exposure on gene expression and effects of FSS at differing rates on gene expression in hPTCs has not been thoroughly investigated. Here, we performed RNA-sequencing of human RPTEC/TERT1 cells in a microfluidic chip-based 3D model to determine transcriptomic changes. We measured transcriptional changes following treatment of cells in this device at three different fluidic shear stress. We observed that FSS changes the expression of PTC-specific genes and impacted genes previously associated with renal diseases in genome-wide association studies (GWAS). At a physiological FSS level, we observed cell morphology, enhanced polarization, presence of cilia, and transport functions using albumin reabsorption via endocytosis and efflux transport. Here, we present a dynamic view of hPTCs response to FSS with increasing fluidic shear stress conditions and provide insight into hPTCs cellular function under biologically relevant conditions.

scholarly journals Epigenetic Changes During Mechanically Induced Osteogenic Lineage Commitment

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Julia C. Chen ◽  
Mardonn Chua ◽  
Raymond B. Bellon ◽  
Christopher R. Jacobs
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Shear Stress ◽  
Fluid Shear Stress ◽  
Methylation Status ◽  
Lineage Commitment ◽  
Fluid Shear ◽  
Osteogenic Lineage ◽  
Osteogenic Markers ◽  
Heterochromatin Structure

Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epigenetic regulation, is stable and heritable. Therefore, analyzing methylation status may be less temporally dependent and more informative for evaluating lineage commitment. Here we analyzed the effect of mechanical stimulation on osteogenic differentiation by applying fluid shear stress for 24 hr to osteocytes and then applying the osteocyte-conditioned medium (CM) to progenitor cells. We analyzed gene expression and changes in DNA methylation after 24 hr of exposure to the CM using quantitative real-time polymerase chain reaction and bisulfite sequencing. With fluid shear stress stimulation, methylation decreased for both adipogenic and osteogenic markers, which typically increases availability of genes for expression. After only 24 hr of exposure to CM, we also observed increases in expression of later osteogenic markers that are typically observed to increase after seven days or more with biochemical induction. However, we observed a decrease or no change in early osteogenic markers and decreases in adipogenic gene expression. Treatment of a demethylating agent produced an increase in all genes. The results indicate that fluid shear stress stimulation rapidly promotes the availability of genes for expression, but also specifically increases gene expression of later osteogenic markers.

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