Lattice Boltzmann simulation of cell adhesion in microcirculation

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Lattice Boltzmann simulation of cell adhesion in microcirculation

 

Author: Yan, Weiwei
Title: Lattice Boltzmann simulation of cell adhesion in microcirculation
Degree: Ph.D.
Year: 2011
Subject: Cell adhesion.
Cell interaction.
Cells -- Mechanical properties
Lattice Boltzmann methods.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xiv, 165 leaves : ill. (some col.) ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2456219
URI: http://theses.lib.polyu.edu.hk/handle/200/6150
Abstract: Cell adhesion under blood flow conditions is a common and very important phenomenon in microcirculation. In this thesis, the fluid dynamics was solved by the lattice Boltzmann method (LBM), the cells dynamics was implemented by the Newton's law of translation and rotation, and the adhesive dynamics models were involved to take into account the effect of receptor-ligand bonds on cell adhesion. Firstly, the effects of vessel curvature and cell-cell interaction on cell adhesion in both the straight and curved micro-vessels were numerically studied. The results indicated that the curved vessels would increase the simultaneous bonds number, and the probability of cell adhesion is increased consequently. In addition, the cell-cell interactions would also affect the cell adhesion greatly. For two-cell case, the simultaneous bonds number of the rear cell is increased significantly in both the straight and curved vessels. The results would be helpful to explain the mechanical mechanism of the strange biological phenomena why the circulating blood cells and tumor cells are more easily gathering near the bent of vessels. Secondly, the effects of wall shear stress/gradient on tumor cell adhesion in the curved micro-vessels were investigated both experimentally and numerically. Our in vivo experiments revealed that the tumor cells preferred to adhere to the curved vessels and initiated at the inner side of the curved vessels. In simulation cases, two refined adhesive dynamics models were developed to consider the effects of wall shear stress/gradient on receptor-ligand bindings. The numerical results indicated that the wall shear stress/gradient, over a threshold, had significant contribution to tumor cell adhesion by activating or inactivating cell adhesion molecules. This work not only would help us to understand the quantitative relationship between wall shear stress and tumor cell adhesion, but also elucidate why the tumor cell adhesion always occurs at the inner side of the curved vessels. Finally, the effects of divalent cations on neutrophil adhesion in both the straight and curved micro-vessels were computationally investigated. The LFA-1/ICAM-1 adhesion in Mg²⁺ plus EGTA and the VLA-4/VCAM-1 adhesion in Mg²⁺ plus EGTA, Mn²⁺ and Ca²⁺ were simulated under flow conditions. The results suggested that the LFA-1/ICAM-1 adhesion acted as a primary role in neutrophils adhesion. For VLA-4/VCAM-1 adhesion, it was found the affinity state of VLA-4 for endothelial ligand VCAM-1 was highest in Mn²⁺, higher in Ca²⁺, and lowest in Mg²⁺ plus EGTA. This would help us to understand the mechanical mechanisms of integrin-mediated neutrophils adhesion in the presence of different divalent cations under dynamic flow conditions.

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