Steady Flow Preconditioning of Endothelial Outgrowth Cells on Ex Vivo and In Vivo ePTFE Grafts

2013 ◽  
Author(s):  
D. E. J. Anderson ◽  
J. J. Glynn ◽  
M. T. Hinds
Keyword(s):  
Shear Stress ◽  
Steady Flow ◽  
Fluid Shear Stress ◽  
Ex Vivo ◽  
Vascular Grafts ◽  
Small Diameter ◽  
Fluid Shear ◽  
Cell Source

Endothelialization of vascular graft materials is a promising approach for improving the in vivo performance of vascular grafts, particularly for small diameter applications of less than 4 mm. The ability to incorporate a native endothelium onto a graft may reduce the thrombosis and intimal hyperplasia that limits long-term clinical success of these small diameter grafts. Endothelial outgrowth cells (EOCs), which are isolated from whole blood and expand rapidly in vitro, provide an autologous cell source capable of developing into a biologically active endothelial layer. A preconditioning step may enhance EOCs’ performance on vascular grafts. Mature endothelial cells, isolated from vascular walls, are known to decrease expression of pro-thrombotic and pro-inflammatory markers when exposed to steady fluid shear stress, compared to cells under disturbed flow conditions or static culture. This study examined the hypothesis that steady flow preconditioning of EOCs reduces their in vitro markers of thrombosis and inflammation, reduces platelet and fibrin accumulation on EOC–coated ePTFE grafts in an ex vivo shunt, and reduces initial hyperplasia on EOC–coated ePTFE grafts in an in vivo graft implant. This work was performed using well-established, non-human primate models for testing EOC-coated ePTFE grafts ex vivo and in vivo. These conditions represent a clinically-relevant cell source and biomaterial for determining the effects of fluid shear stress preconditioning on graft performance.

scholarly journals ShearFAST: a user-friendly in vitro toolset for high throughput, inexpensive fluid shear stress experiments.

2020 ◽  
Author(s):  
Thomas Brendan Smith ◽  
Alessandro Marco De Nunzio ◽  
Kamlesh Patel ◽  
Haydn Munford ◽  
Tabeer Alam ◽  
...  
Keyword(s):  
Shear Stress ◽  
High Throughput ◽  
Fluid Shear Stress ◽  
Tracking System ◽  
Frequency Measurement ◽  
Camera Motion ◽  
Fluid Shear ◽  
Mean Frequency

Fluid shear stress is a key modulator of cellular physiology in vitro and in vivo, but its effects are under-investigated due to requirements for complicated induction methods. Herein we report the validation of ShearFAST; a smartphone application that measures the rocking profile on a standard laboratory cell rocker and calculates the resulting shear stress arising in tissue culture plates. The accuracy with which this novel approach measured rocking profiles was validated against a graphical analysis, and also against measures reported by an 8-camera motion tracking system. ShearFASTs angle assessments correlated well with both analyses (r ≥0.99, p ≤0.001) with no significant differences in pitch detected across the range of rocking angles tested. Rocking frequency assessment by ShearFAST also correlated well when compared to the two independent validatory techniques (r ≥0.99, p ≤0.0001), with excellent reproducibility between ShearFAST and video analysis (mean frequency measurement difference of 0.006 ± 0.005Hz) and motion capture analysis (mean frequency measurement difference of 0.008 ± 0.012Hz). These data make the ShearFAST assisted cell rocker model make it an attractive approach for economical, high throughput fluid shear stress experiments. Proof of concept data presented reveals a protective effect of low-level shear stress on renal proximal tubule cells submitted to simulations of pretransplant storage.

Nanoparticle localization in blood vessels: dependence on fluid shear stress, flow disturbances, and flow-induced changes in endothelial physiology

Nanoscale ◽  
2018 ◽  
Vol 10 (32) ◽  
pp. 15249-15261 ◽  
Author(s):  
M. Juliana Gomez-Garcia ◽  
Amber L. Doiron ◽  
Robyn R. M. Steele ◽  
Hagar I. Labouta ◽  
Bahareh Vafadar ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Fluid Shear ◽  
Nanoparticle Distribution ◽  
Flow Models ◽  
Flow Disturbances ◽  
Induced Changes ◽  
Stress Flow

Hemodynamic factors drive nanoparticle distribution in vivo and in vitro in cell-based flow models.

scholarly journals CD44 regulates blood-brain barrier integrity in response to fluid shear stress

2020 ◽  
Author(s):  
Brandon J. DeOre ◽  
Paul P. Partyka ◽  
Fan Fan ◽  
Peter A. Galie
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Blood Brain Barrier ◽  
Fluid Shear Stress ◽  
Small Gtpase ◽  
Brain Barrier ◽  
Fluid Shear ◽  
Blood Brain

AbstractFluid shear stress is an important mediator of vascular permeability, yet the molecular mechanisms underlying the response of the blood-brain barrier to shear have yet to be studied in cerebral vasculature despite its importance for brain homeostasis. The goal of this study is to probe components of shear mechanotransduction within the blood-brain barrier to gain a better understanding of pathologies associated with changes in cerebral blood flow including ischemic stroke. Interrogating the effects of shear stress in vivo is complicated by the complexity of factors in the brain parenchyma and the difficulty associated with modulating blood flow regimes. Recent advances in the ability to mimic the in vivo microenvironment using three-dimensional in vitro models provide a controlled setting to study the response of the blood-brain barrier to shear stress. The in vitro model used in this study is compatible with real-time measurement of barrier function using transendothelial electrical resistance as well as immunocytochemistry and dextran permeability assays. These experiments reveal that there is a threshold level of shear stress required for barrier formation and that the composition of the extracellular matrix, specifically the presence of hyaluronan, dictates the flow response. Gene editing to modulate the expression of CD44, a receptor for hyaluronan that previous studies have identified to be mechanosensitive, demonstrates that the receptor is required for the endothelial response to shear stress. Manipulation of small GTPase activity reveals CD44 activates Rac1 while inhibiting RhoA activation. Additionally, adducin-γ localizes to tight junctions in response to shear stress and RhoA inhibition and is required to maintain the barrier. This study identifies specific components of the mechanosensing complex associated with the blood-brain barrier response to fluid shear stress, and therefore illuminates potential targets for barrier manipulation in vivo.

scholarly journals PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1

2021 ◽  
Author(s):  
Shashi Kant ◽  
Khanh-Van Tran ◽  
Miroslava Kvandova ◽  
Amada D. Caliz ◽  
Hyung-Jin Yoo ◽  
...  
Keyword(s):  
Shear Stress ◽  
Reverse Transcriptase ◽  
Heme Oxygenase ◽  
Fluid Shear Stress ◽  
Heme Oxygenase 1 ◽  
Telomerase Reverse Transcriptase ◽  
Fluid Shear ◽  
Flow Alignment

Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow that is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. Here we have identified peroxisome proliferator gamma coactivator-1α (PGC-1α) as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared to oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) increased PGC-1α expression and its transcriptional co-activation. PGC-1α was required for laminar FSS-induced expression of telomerase reverse transcriptase (TERT) in vitro and in vivo via its association with ERRα and KLF4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status was heme oxygenase-1 (HMOX1), a gene required for endothelial alignment to laminar FSS. Thus, these data suggest an important role for a PGC-1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

scholarly journals Fluid Shear Stress Induction of the Tissue Factor Promoter In Vitro and In Vivo Is Mediated by Egr-1

1999 ◽  
Vol 19 (2) ◽  
pp. 281-289 ◽  
Author(s):  
Parul Houston ◽  
Marion C. Dickson ◽  
Valerie Ludbrook ◽  
Brian White ◽  
Jean-Luc Schwachtgen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Tissue Factor ◽  
Fluid Shear Stress ◽  
Fluid Shear ◽  
Stress Induction

scholarly journals Fluid Shear Stress Induces Heat Shock Protein 60 Expression in Endothelial Cells In Vitro and In Vivo

2000 ◽  
Vol 20 (3) ◽  
pp. 617-623 ◽  
Author(s):  
Boris-Wolfgang Hochleitner ◽  
Elisabeth-Olga Hochleitner ◽  
Peter Obrist ◽  
Thomas Eberl ◽  
Albert Amberger ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Fluid Shear Stress ◽  
Heat Shock Protein 60 ◽  
Fluid Shear

Experimental Technique of Measuring Dynamic Fluid Shear Stress on the Aortic Surface of the Aortic Valve Leaflet

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Choon Hwai Yap ◽  
Neelakantan Saikrishnan ◽  
Gowthami Tamilselvan ◽  
Ajit P. Yoganathan
Keyword(s):  
Shear Stress ◽  
Aortic Valve ◽  
Steady Flow ◽  
Fluid Shear Stress ◽  
Shear Stresses ◽  
Straight Tube ◽  
Valve Leaflet ◽  
Fluid Shear ◽  
Valve Model

Aortic valve (AV) calcification is a highly prevalent disease with serious impact on mortality and morbidity. The exact cause and mechanism of the progression of AV calcification is unknown, although mechanical forces have been known to play a role. It is thus important to characterize the mechanical environment of the AV. In the current study, we establish a methodology of measuring shear stresses experienced by the aortic surface of the AV leaflets using an in vitro valve model and adapting the laser Doppler velocimetry (LDV) technique. The valve model was constructed from a fresh porcine aortic valve, which was trimmed and sutured onto a plastic stented ring, and inserted into an idealized three-lobed sinus acrylic chamber. Valve leaflet location was measured by obtaining the location of highest back-scattered LDV laser light intensity. The technique of performing LDV measurements near to biological surfaces as well as the leaflet locating technique was first validated in two phantom flow systems: (1) steady flow within a straight tube with AV leaflet adhered to the wall, and (2) steady flow within the actual valve model. Dynamic shear stresses were then obtained by applying the techniques on the valve model in a physiologic pulsatile flow loop. Results show that aortic surface shear stresses are low during early systole (<5dyn/cm2) but elevated to its peak during mid to late systole at about 18–20 dyn/cm2. Low magnitude shear stress (<5dyn/cm2) was observed during early diastole and dissipated to zero over the diastolic duration. Systolic shear stress was observed to elevate only with the formation of sinus vortex flow. The presented technique can also be used on other in vitro valve models such as congenitally geometrically malformed valves, or to investigate effects of hemodynamics on valve shear stress. Shear stress data can be used for further experiments investigating effects of fluid shear stress on valve biology, for conditioning tissue engineered AV, and to validate numerical simulations.

scholarly journals Myofiber stretch induces tensile and shear deformation of muscle stem cells in their native niche

2020 ◽  
Author(s):  
Mohammad Haroon ◽  
Jenneke Klein-Nulend ◽  
Astrid D. Bakker ◽  
Jianfeng Jin ◽  
Carla Offringa ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Stem Cells ◽  
Shear Stress ◽  
Fluid Shear Stress ◽  
Ex Vivo ◽  
Mechanical Forces ◽  
Fluid Shear ◽  
Muscle Stem Cells ◽  
Pulsating Fluid

ABSTRACTBackgroundMuscle stem cells (MuSCs) are requisite for skeletal muscle regeneration and homeostasis. Proper functioning of MuSCs, including activation, proliferation, and fate decision, is determined by an orchestrated series of events and communication between MuSCs and their niche consisting of the host myofiber and neighbouring cells. A multitude of biochemical stimuli are known to regulate fate and function of MuSCs. However, in addition to biochemical factors, it is conceivable that MuSCs residing between basal lamina and sarcolemma of myofibers are subjected to mechanical forces during muscle stretch-shortening cycles due to myofascial connections between MuSCs and myofibers. MuSCs have been shown to respond to mechanical forces in vitro but it remains to be proven whether physical forces are also exerted on MuSCs in their native niche and whether they contribute to the functioning and fate of MuSCs.MethodsMuSCs deformation in their native niche resulting from mechanical loading of ex vivo myofiber bundles were visualized utilizing mT/mG double-fluorescent Cre-reporter mouse and multiphoton microscopy. MuSCs were subjected to 1 hour pulsating fluid shear stress with a peak shear stress rate of 8.8 Pa/s. After treatment, nitric oxide and mRNA expression levels of genes involved in regulation of MuSC proliferation and differentiation were determined.ResultsEx vivo stretching of extensor digitorum longus and soleus myofiber bundles caused compression as well as tensile and shear deformation of MuSCs in their niche. MuSCs responded to pulsating fluid shear stress in vitro with increased nitric oxide production and an upward trend in iNOS mRNA levels, while nNOS expression was unaltered. Pulsating fluid shear stress enhanced gene expression of c-Fos, Cdk4, and IL-6, while expression of Wnt1, MyoD, Myog, Wnt5a, COX2, Rspo1, Vangl2, Wnt10b, and MGF remained unchanged.ConclusionsWe conclude that MuSCs in their native niche are subjected to force-induced deformations due to myofiber stretch-shortening. Moreover, MuSCs are mechanoresponsive as evident by pulsating fluid shear stress-mediated expression of factors by MuSCs known to promote proliferation.

scholarly journals PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1

2021 ◽  
Author(s):  
Shashi Kant ◽  
Khanh-Van Tran ◽  
Miroslava Kvandova ◽  
Amada D. Caliz ◽  
Hyung-Jin Yoo ◽  
...  
Keyword(s):  
Shear Stress ◽  
Reverse Transcriptase ◽  
Heme Oxygenase ◽  
Fluid Shear Stress ◽  
Heme Oxygenase 1 ◽  
Telomerase Reverse Transcriptase ◽  
Fluid Shear ◽  
Flow Alignment

Objective: Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow, which is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. In this study, we determine the role of PGC1α (peroxisome proliferator gamma coactivator-1α)-TERT (telomerase reverse transcriptase)-HMOX1 (heme oxygenase-1) during shear stress in vitro and in vivo. Approach and Results: Here, we have identified PGC1α as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared with oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) showed increased PGC1α expression and its transcriptional coactivation. PGC1α was required for laminar FSS-induced expression of TERT in vitro and in vivo via its association with ERRα(estrogen-related receptor alpha) and KLF (Kruppel-like factor)-4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status, HMOX1 was required for endothelial alignment to laminar FSS. Conclusions: These data suggest an important role for a PGC1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

scholarly journals Cell spinpods are a simple inexpensive suspension culture device to deliver fluid shear stress to renal proximal tubular cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timothy G. Hammond ◽  
Corey Nislow ◽  
Ivan C. Christov ◽  
Vecihi Batuman ◽  
Pranay P. Nagrani ◽  
...  
Keyword(s):  
Shear Stress ◽  
Suspension Culture ◽  
Fluid Shear Stress ◽  
Industrial Applications ◽  
Specific Pattern ◽  
Fluid Shear ◽  
Cellular Functions ◽  
Renal Proximal Tubular Cells

AbstractRotating forms of suspension culture allow cells to aggregate into spheroids, prevent the de-differentiating influence of 2D culture, and, perhaps most importantly of all, provide physiologically relevant, in vivo levels of shear stress. Rotating suspension culture technology has not been widely implemented, in large part because the vessels are prohibitively expensive, labor-intensive to use, and are difficult to scale for industrial applications. Our solution addresses each of these challenges in a new vessel called a cell spinpod. These small 3.5 mL capacity vessels are constructed from injection-molded thermoplastic polymer components. They contain self-sealing axial silicone rubber ports, and fluoropolymer, breathable membranes. Here we report the two-fluid modeling of the flow and stresses in cell spinpods. Cell spinpods were used to demonstrate the effect of fluid shear stress on renal cell gene expression and cellular functions, particularly membrane and xenobiotic transporters, mitochondrial function, and myeloma light chain, cisplatin and doxorubicin, toxicity. During exposure to myeloma immunoglobulin light chains, rotation increased release of clinically validated nephrotoxicity cytokine markers in a toxin-specific pattern. Addition of cisplatin or doxorubicin nephrotoxins reversed the enhanced glucose and albumin uptake induced by fluid shear stress in rotating cell spinpod cultures. Cell spinpods are a simple, inexpensive, easily automated culture device that enhances cellular functions for in vitro studies of nephrotoxicity.

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