Effect Of Hydrodynamic Shear Research Articles

Rotary orbital suspension culture of embryonic stem cell-derived neural stem/progenitor cells: impact of hydrodynamic culture on aggregate yield, morphology and cell phenotype.

Embryonic stem (ES)-derived neural stem/progenitor cells (ES-NSPCs) constitute a promising cell source for application in cell therapies for the treatment of central nervous system disorders. In this study, a rotary orbital hydrodynamic culture system was applied to single-cell suspensions of ES-NSPCs, to obtain homogeneously-sized ES-NSPC cellular aggregates (neurospheres). Hydrodynamic culture allowed the formation of ES-NSPC neurospheres with a narrower size distribution than statically cultured neurospheres, increasing orbital speeds leading to smaller-sized neurospheres and higher neurosphere yield. Neurospheres formed under hydrodynamic conditions (72 h at 55 rpm) showed higher cell compaction and comparable percentages of viable, dead, apoptotic and proliferative cells. Further characterization of cellular aggregates provided new insights into the effect of hydrodynamic shear on ES-NSPC behaviour. Rotary neurospheres exhibited reduced protein levels of N-cadherin and β-catenin, and higher deposition of laminin (without impacting fibronectin deposition), matrix metalloproteinase-2 (MMP-2) activity and percentage of neuronal cells. In line with the increased MMP-2 activity levels found, hydrodynamically-cultured neurospheres showed higher outward migration on laminin. Moreover, when cultured in a 3D fibrin hydrogel, rotary neurospheres generated an increased percentage of neuronal cells. In conclusion, the application of a constant orbital speed to single-cell suspensions of ES-NSPCs, besides allowing the formation of homogeneously-sized neurospheres, promoted ES-NSPC differentiation and outward migration, possibly by influencing the expression of cell-cell adhesion molecules and the secretion of proteases/extracellular matrix proteins. These findings are important when establishing the culture conditions needed to obtain uniformly-sized ES-NSPC aggregates, either for use in regenerative therapies or in in vitro platforms for biomaterial development or pharmacological screening. Copyright © 2016 John Wiley & Sons, Ltd.

Role of fluid shear stress in regulating VWF structure, function and related blood disorders.

Von Willebrand factor (VWF) is the largest glycoprotein in blood. It plays a crucial role in primary hemostasis via its binding interaction with platelet and endothelial cell surface receptors, other blood proteins and extra-cellular matrix components. This protein is found as a series of repeat units that are disulfide bonded to form multimeric structures. Once in blood, the protein multimer distribution is dynamically regulated by fluid shear stress which has two opposing effects: it promotes the aggregation or self-association of multiple VWF units, and it simultaneously reduces multimer size by facilitating the force-dependent cleavage of the protein by various proteases, most notably ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type repeats, motif 1 type 13). In addition to these effects, fluid shear also controls the solution and substrate-immobilized structure of VWF, the nature of contact between blood platelets and substrates, and the biomechanics of the GpIbα–VWF bond. These features together regulate different physiological and pathological processes including normal hemostasis, arterial and venous thrombosis, von Willebrand disease, thrombotic thrombocytopenic purpura and acquired von Willebrand syndrome. This article discusses current knowledge of VWF structure–function relationships with emphasis on the effects of hydrodynamic shear, including rapid methods to estimate the nature and magnitude of these forces in selected conditions. It shows that observations made by many investigators using solution and substrate-based shearing devices can be reconciled upon considering the physical size of VWF and the applied mechanical force in these different geometries.

Effect of Hydrodynamic Shear on Agglomerated Ground Calcium Carbonate Filler after Surface Modification with Starch and its Effects on Paper Properties

Ground calcium carbonate (GCC) was modified with starch, sodium stearate, and sodium hexametaphosphate prior to the papermaking process. This paper is focused on the effect of shear on the modified GCC and considers the impact of adding modified GCC into paper. The coating efficiency of starch on GCC was investigated in terms of the shear-tolerance of the agglomerated filler. Experimental results showed that the precipitation temperature and the amount of crosslinking agent, sodium hexametaphosphate, both were important relative to shear tolerance. Lower precipitation temperature was beneficial for the starch coating. Within a certain range, more sodium hexametaphosphate led to a stronger complex. The results showed that 1.5% (based on MGCC) of sodium hexametaphosphate and a precipitation temperature of 60 °C were the optimum conditions for shear tolerance.

The Filtration Properties of Atropa belladonna Plant Cell Suspensions; Effects of Hydrodynamic Shear and Elevated Carbon Dioxide Levels on Culture and Filtration Parameters

The Filtration Properties of Atropa belladonna Plant Cell Suspensions; Effects of Hydrodynamic Shear and Elevated Carbon Dioxide Levels on Culture and Filtration Parameters