Biorheology - Volume 48, issue 5-6

Authors: Nebelung, Sven | Gavenis, Karsten | Rath, Björn | Tingart, Marcus | Ladenburger, Andreas | Stoffel, Marcus | Zhou, Bei | Mueller-Rath, Ralf

Article Type: Research Article

Abstract: Purpose: This study investigated the potential of cyclic compressive loading in the generation of in vitro engineered cartilaginous tissue with the aim of contributing to a better understanding of mechanical preconditioning and its possible role in further optimizing existing matrix-associated cartilage replacement procedures. Methods: Human chondrocytes were harvested from 12 osteoarthritic knee joints and seeded into a type I collagen (col-I) hydrogel at low density (2×105 cells/ml gel). The cell-seeded hydrogel was condensed and cultivated under continuous cyclic compressive loading (frequency: 0.3 Hz; strain: 10%) for 14 days under standardized conditions. After retrieval, specimens were subject to staining, …histomorphometric evaluation, gene expression analysis and biomechanical testing. Results: Cellular morphology was altered by both stimulation and control conditions as was staining for collagen II (col-II). Gene expression measurements revealed a significant increase for col-II under either cultivation condition. No significant differences in col-I, aggrecan and MMP-13 gene expression profiles were found. The col-II/col-I mRNA ratio significantly increased under stimulation, whereas the biomechanical properties deteriorated under either cultivation method. Conclusions: Although the effects observed are small, mechanical preconditioning has demonstrated its potential to modulate biological properties of collagen hydrogels seeded with human chondrocytes. Show more

Keywords: Human chondrocytes, cell-seeded scaffold, bioreactor cultivation, collagen hydrogel, dynamic loading

DOI: 10.3233/BIR-2012-0597

Citation: Biorheology, vol. 48, no. 5-6, pp. 247-261, 2011

Authors: Finelli, Ivana | Chiessi, Ester | Galesso, Devis | Renier, Davide | Paradossi, Gaio

Article Type: Research Article

Abstract: A novel partially hydrophobized derivative of hyaluronic acid (HYADD® 4), containing a low number of C16 side-chains per polysaccharide backbone, provides injectable hydrogels stabilized by side-chain hydrophobic interactions. The rheological properties of Hymovis® , a physical hydrogel based on the hyaluronic acid derivative HYADD® 4, were evaluated using as reference a solution of the parent natural polysaccharide, hyaluronic acid. The rheological measurements were performed both in flow and oscillation regimes at the physiological frequency values of the knee, typically spanning the range from 0.5 Hz (walking frequency) to 3 Hz (running frequency). Moreover, the viscoelastic features of Hymovis® were …compared with the market-available viscosupplementation products in view of its use in joint diseases. The different behavior of the investigated materials in crossover frequency measurements and in structure recovery experiments can be explained on the basis of the structural and dynamic properties of the polymeric systems. Show more

Keywords: Hyaluronic acid, rheology, hydrogels, elastic modulus, viscosupplement, osteoarthritis

DOI: 10.3233/BIR-2011-0596

Citation: Biorheology, vol. 48, no. 5-6, pp. 263-275, 2011

Authors: Yalcin, Ozlem | Wang, Qi | Johnson, Paul C. | Palmer, Andre F. | Cabrales, Pedro

Article Type: Research Article

Abstract: The objective of the study was to investigate the effects of plasma viscosity after hemodilution on the thickness of the erythrocyte cell free layer (CFL) and on the interface between the flowing column of erythrocytes and the vascular endothelium. The erythrocyte CFL thickness was measured in the rat cremaster muscle preparation. Plasma viscosity was modified in an isovolemic hemodilution, in which the systemic hematocrit (Hctsys ) was lowered to 30%. The plasma expanders (PE) of similar nature and different viscosities were generated by glutaraldehyde polymerization of human serum albumin (HSA) at various molar ratios glutaraldehyde to HSA: (i) unpolymerized HSA; …(ii) PolyHSA24:1 , molar ratio = 24 and (iii) PolyHSA60:1 , molar ratio = 60. The HSA viscosities determined at 200 s−1 were 1.1, 4.2 and 6.0 dyn·cm−2 , respectively. CFL thickness, vessel diameter and blood flow velocity were measured, while volumetric flow, shear rate and stress were calculated. Hemodilution with PolyHSA60:1 increased plasma viscosity and the blood showed marked shear thinning behavior. CFL thickness decreased as plasma viscosity increased after hemodilution; thus the CFL thickness with HSA and PolyHSA24:1 increased compared to baseline. Conversely, the CFL thickness of PolyHSA60:1 was not different from baseline. Blood flow increased with both PolyHSA's compared to baseline. Wall shear rate and shear stress increased for PolyHSA60:1 compared to HSA and PolyHSA24:1 , respectively. In conclusion, PE viscosity determined plasma viscosity after hemodilution and affected erythrocyte column hydrodynamics, changing the velocity profile, CFL thickness, and wall shear stress. This study relates the perfusion caused by PolyHSA60:1 to hemodynamic changes induced by the rheological properties of blood diluted with PolyHSA60:1 . Show more

Keywords: Hematocrit, endothelium, human serum albumin, polymerized human serum albumin

DOI: 10.3233/BIR-2012-0598

Citation: Biorheology, vol. 48, no. 5-6, pp. 277-291, 2011

Authors: Simmonds, Michael J. | Meiselman, Herbert J. | Marshall-Gradisnik, Sonya M. | Pyne, Michael | Kakanis, Michael | Keane, James | Brenu, Ekua | Christy, Rhys | Baskurt, Oguz K.

Article Type: Research Article

Abstract: The present study was designed to investigate the oxidant susceptibility of red blood cells (RBC) from four species (echidna, human, koala, Tasmanian devil) based on changes in cellular deformability. These species were specifically chosen based on differences in lifestyle and/or biology associated with varied levels of oxidative stress. The major focus was the influence of superoxide radicals generated within the cell (phenazine methosulfate, PMS, 50 μM) or in the extracellular medium (xanthine oxidase–hypoxanthine, XO–HX, 0.1 U/ml XO) on RBC deformability at various shear stresses (SS). RBC deformability was assessed by laser-diffraction analysis using a “slit-flow ektacytometer”. Both superoxide-generating treatments resulted …in significant increases of methemoglobin for all species (p<0.01), with Tasmanian devil RBC demonstrating the most sensitivity to either treatment. PMS caused impaired RBC deformability for all species, but vast interspecies variations were observed: human and koala cells exhibited a similar sigmoid-like response to SS, short-beaked echidna values were markedly lower and only increased slightly with SS, while Tasmanian devil RBC were extremely rigid. The effect of XO–HX on RBC deformability was less when compared with PMS (i.e., smaller increase in rigidity) with the exception of Tasmanian devil RBC which exhibited essentially no deformation even at the highest SS; Tasmanian devil RBC response to XO–HX was thus comparable to that observed with PMS. Our findings indicate that ektacytometry can be used to determine the oxidant susceptibility of RBC from different species which varies significantly among mammals representing diverse lifestyles and evolutionary histories. These differences in susceptibility are consistent with species-specific discrepancies between observed and allometrically-predicted life spans and are compatible with the oxidant theory of aging. Show more

Keywords: RBC deformability, superoxide, mammalian species

DOI: 10.3233/BIR-2012-0599

Citation: Biorheology, vol. 48, no. 5-6, pp. 293-304, 2011

Authors: Chen, Chia-Yuan | Patrick, Michael J. | Corti, Paola | Kowalski, William | Roman, Beth L. | Pekkan, Kerem

Article Type: Research Article

Abstract: In the developing cardiovascular system, hemodynamic vascular loading is critical for angiogenesis and cardiovascular adaptation. Normal zebrafish embryos with transgenically-labeled endothelial and red blood cells provide an excellent in vivo model for studying the fluid-flow induced vascular loading. To characterize the developmental hemodynamics of early embryonic great-vessel microcirculation in the zebrafish embryo, two complementary studies (experimental and numerical) are presented. Quantitative comparison of the wall shear stress (WSS) at the first aortic arch (AA1) of wild-type zebrafish embryos during two consecutive developmental stages is presented, using time-resolved confocal micro-particle image velocimetry (μPIV). Analysis showed that there was significant WSS difference …between 32 and 48 h post-fertilization (hpf) wild-type embryos, which correlates with normal arch morphogenesis. The vascular distensibility of the arch wall at systole and the acceleration/deceleration rates of time-lapse phase-averaged streamwise blood flow curves were also analyzed. To estimate the influence of a novel intermittent red-blood cell (RBC) loading on the endothelium, a numerical two-phase, volume of fluid (VOF) flow model was further developed with realistic in vivo conditions. These studies showed that near-wall effects and cell clustering increased WSS augmentation at a minimum of 15% when the distance of RBC from arch vessel wall was less than 3 μm or when RBC cell-to-cell distance was less than 3 μm. When compared to a smooth wall, the WSS augmentation increased by a factor of ~1.4 due to the roughness of the wall created by the endothelial cell profile. These results quantitatively highlight the contribution of individual RBC flow patterns on endothelial WSS in great-vessel microcirculation and will benefit the quantitative understanding of mechanotransduction in embryonic great vessel biology, including arteriovenous malformations (AVM). Show more

Keywords: Confocal microscopy, time-resolved particle image velocimetry (PIV), zebrafish, mechanotransduction, wall shear stress, volume of fluid (VOF) method

DOI: 10.3233/BIR-2012-0600

Citation: Biorheology, vol. 48, no. 5-6, pp. 305-321, 2011

Article Type: Other

Citation: Biorheology, vol. 48, no. 5-6, pp. 323-326, 2011