Biorheology - Volume 47, issue 3-4

Authors: Park, Joong Yull | Yoo, Sung Ju | Patel, Lalit | Lee, Soon Hyuck | Lee, Sang-Hoon

Article Type: Research Article

Abstract: Slow interstitial flow can lead to large changes in cell morphology. Since conventional biological assays are adapted to two-dimensional culture protocols, there is a need to develop a microfluidic system that can generate physiological levels of interstitial flow. Here we developed a system that uses a passive osmotic pumping mechanism to generate sustained and steady interstitial flows for two-dimensional cultures. Two different cell types, fibroblasts and mesenchymal stem cells, were selected because they are generally exposed to interstitial flow. To quantify the cellular response to interstitial shear flow in terms of proliferation and alignment, 4 rates of flow were applied. …We found that the proliferation rate of fibroblasts varied linearly with wall shear stress. In addition, alignment of fibroblast cells depended linearly on the magnitude of the shear stress, whereas mesenchymal stem cells were aligned regardless of the magnitude of shear stress. This suggested that mesenchymal stem cells are very sensitive to shear stresses, even at levels generated by interstitial flow. The results presented here emphasize the need to consider the mechanosensitivity and the natural role of different cell types when evaluating their responses to fluid flow. Show more

Keywords: Mechanosensitivity, fibroblast, mesenchymal stem cell, interstitial flow, shear stress

DOI: 10.3233/BIR-2010-0567

Citation: Biorheology, vol. 47, no. 3-4, pp. 165-178, 2010

Authors: van der Meer, A.D. | Li, Y. | Duits, M.H.G. | Poot, A.A. | Feijen, J. | Vermes, I.

Article Type: Research Article

Abstract: Vascular endothelial cells form the inner lining of all blood vessels and play a central role in vessel physiology and disease. Endothelial cells are highly responsive to the mechanical stimulus of fluid shear stress that is exerted by blood flowing over their surface. In this study, the immediate micromechanical response of endothelial cells to physiological shear stress was characterized by tracking of ballistically injected, sub-micron, fluorescent particles. It was found that the mean squared displacement (MSD) of the particles decreases by a factor 1.5 within 10 min after the onset of shear stress. This decrease in particle motion is transient, …since the MSD returns to control values within 15–30 min after the onset of shear. The immediate micromechanical stiffening is dependent on activation of the vascular endothelial growth factor receptor (VEGFR)-2, because inhibition of the receptor abrogates the micromechanical response. This work shows that the cytoskeleton is actively involved in the acute, functional response of endothelial cells to shear stress. Show more

Keywords: Particle tracking, actin, cytoskeleton, microfluidic

DOI: 10.3233/BIR-2010-0569

Citation: Biorheology, vol. 47, no. 3-4, pp. 179-192, 2010

Authors: Zhao, R. | Marhefka, J.N. | Antaki, J.F. | Kameneva, M.V.

Article Type: Research Article

Abstract: The accumulation of platelets near the blood vessel wall or artificial surface is an important factor in the cascade of events responsible for coagulation and/or thrombosis. In small blood vessels and flow channels this phenomenon has been attributed to the blood phase separation that creates a red blood cell (RBC)-poor layer near the wall. We hypothesized that blood soluble drag-reducing polymers (DRP), which were previously shown to lessen the near-wall RBC depletion layer in small channels, may consequently reduce the near-wall platelet excess. This study investigated the effects of DRP on the lateral distribution of platelet-sized fluorescent particles (diam. = …2 μm, 2.5 × 108 /ml) in a glass square microchannel (width and depth = 100 μm). RBC suspensions in PBS were mixed with particles and driven through the microchannel at flow rates of 6–18 ml/h with and without added DRP (10 ppm of PEO, MW = 4500 kDa). Microscopic flow visualization revealed an elevated concentration of particles in the near-wall region for the control samples at all tested flow rates (between 2.4 ± 0.8 times at 6 ml/h and 3.3 ± 0.3 times at 18 ml/h). The addition of a minute concentration of DRP virtually eliminated the near-wall particle excess, effectively resulting in their even distribution across the channel, suggesting a potentially significant role of DRP in managing and mitigating thrombosis. Show more

Keywords: Drag-reducing polymers, platelet margination, microchannels, red blood cell traffic

DOI: 10.3233/BIR-2010-0570

Citation: Biorheology, vol. 47, no. 3-4, pp. 193-203, 2010

Authors: Bingöl, A.Ö. | Lohmann, D. | Püschel, K. | Kulicke, W.-M.

Article Type: Research Article

Abstract: The focus of this work is on a comparative rheological characterization of sodium hyaluronate (NaHA) samples from fermentative production (NaHA-1, Mw = 1.7 × 106 g/mol) and from rooster comb (NaHA-2, Mw = 4.6 × 106 g/mol) with synovial fluid (SF) taken post mortem from different patients above 60 years. Steady state shear flow and uniaxial extension experiments were carried out for different concentrations of NaHA in 0.01 M phosphate-buffered saline (PBS) and on several SF samples. The synovial fluid of older patients was found to have a viscoelasticity comparable to that of younger patients …investigated in earlier studies. Comparison of steady state shear experiments revealed a comparable progression for the viscosity curves of NaHA-2 and SF. This behavior was also observed in extensional flow, where comparable results for NaHA-2 and different SF samples were obtained. Show more

Keywords: Rheology, viscoelastic properties, CaBER, light scattering

DOI: 10.3233/BIR-2010-0572

Citation: Biorheology, vol. 47, no. 3-4, pp. 205-224, 2010

Authors: Chatpun, Surapong | Cabrales, Pedro

Article Type: Research Article

Abstract: The purpose of this study was to investigate how plasma viscosity affects cardiac and vascular function during moderate hemodilution. Twelve anesthetized hamsters were hemodiluted by 40% of blood volume with two different viscosity plasma expanders. Experimental groups were based on the plasma expander viscosity, namely: high viscosity plasma expander (HVPE, 6.3 mPa · s) and low viscosity plasma expander (LVPE, 2.2 mPa · s). Left ventricular (LV) function was intracardiacally measured with a high temporal resolution miniaturized conductance catheter and concurrent pressure–volume results were used to calculate different LV indices. Independently of the plasma expander, hemodilution decreased hematocrit to 28% in both groups. LVPE …hemodilution reduced whole blood viscosity by 40% without changing plasma viscosity, while HVPE hemodilution reduced whole blood viscosity by 23% and almost doubled plasma viscosity relative to baseline. High viscosity plasma expander hemodilution significantly increased cardiac output, stroke volume and stroke work compared to baseline, whereas LVPE hemodilution did not. Furthermore, an increase in plasma viscosity during moderate hemodilution produced a higher energy transfer per unit volume of ejected blood. Systemic vascular resistance decreased after hemodilution in both groups. Counter-intuitively, HVPE hemodilution showed lower vascular resistance and vascular hindrance than LVPE hemodilution. This result suggests that geometrical changes in the circulatory system are induced by the increase in plasma viscosity. In conclusion, an increase in plasma viscosity after moderate hemodilution directly influenced cardiac and vascular function by maintaining hydraulic power and reducing systemic vascular resistance through vasodilation. Show more

Keywords: Cardiac function, anemia, volume expansion, plasma viscosity, conductance catheter

DOI: 10.3233/BIR-2010-0574

Citation: Biorheology, vol. 47, no. 3-4, pp. 225-237, 2010

Authors: Hsiu, Hsin | Huang, Shih-Min | Hsu, Tse-Lin

Article Type: Research Article

Abstract: Objective: We aimed to verify whether microcirculatory blood flow variability (MBFV) parameters calculated from beat-to-beat laser Doppler flowmetry (LDF) waveforms can be used instead of microcirculatory blood flow (MBF) as an index to discriminate different local microcirculatory regulation in terms of the opening condition of arteriolar openings (AO) at different sites. Methods: Angiotensin II (Ang-II) was administered to nine healthy male rats. LDF probes were placed on their renal cortex and plantar palm. The pulse width (PW) and coefficient of variance of the flux (ϕ) for all the pulses within a data sequence was calculated to evaluate the AO's …opening condition. Results: Monitoring and prediction linear-regression analyses revealed significant positive ϕ-vs-μ (mean flux) and PW-vs-μ slopes at renal cortex for their changes relative to the baseline values. Conclusion: The present results suggest that these parameters calculated from the beat-to-beat LDF waveform could be useful for monitoring MBF by administering Ang-II. Moreover, possible time-domain causal relation between changes in μ and these parameters was revealed, which may allow the prediction of changes in MBF that occur 10–30 min thereafter. Deeper understanding of MBFV parameters could be useful in monitoring of progression of cardiovascular diseases and in predicting the efficacy of specific therapies. Show more

Keywords: Microcirculatory blood flow, variability, angiotensin II

DOI: 10.3233/BIR-2010-0573

Citation: Biorheology, vol. 47, no. 3-4, pp. 239-253, 2010