Keywords

Paper information

Kozaburo Hayashi and Takeru Naiki, “Preface”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 4 (2010), pp.280-280 . doi:10.1299/jbse.5.280

Monocyte accumulation in the arterial intima is a hallmark in early atherosclerosis. Monocyte extravasation involves sequential processes including rolling, adhesion, and transmigration across vascular endothelial cells (ECs), where abundant mechanical interactions between these two cells exist. Platelet-endothelial cell adhesion molecule-1 (PECAM-1) is a junctional protein expressed on both cells, and participates in paracellular transmigration via homophilic binding between these cells, while PECAM-1 binds homophilically between neighboring ECs in the absence of monocytes. During monocyte transmigration, PECAM-1-bearing membrane can be recruited to the transmigration spot from intracellular pools. The mechanism by which PECAM-1 binding between ECs in control state is switched to that between monocytes and ECs during transmigration, and its relationship with recruited PECAM-1 remain unclear. In this study, we built an experimental model in vitro for studying molecular behavior of PECAM-1 during monocyte transmigration. A plasmid vector containing PECAM-1 tagged with green (GFP) or red (DsRed) fluorescent protein was constructed, and separately transfected into ECs. The mixture of both transfectants in culture achieved a monolayer that contains an intercellular PECAM-1 boundary between PECAM-1-GFP- and PECAM-1-DsRed-expressing cells which is visualized as yellow in merged image. Using this model together with confocal laser scanning microscope-based system, molecular behavior of PECAM-1 on neighboring ECs during monocyte transmigration was observed in live cells. This model can be essential to directly visualize binding/dissociation state of PECAM-1 between neighboring ECs during monocyte trans-endothelial migration in relation to mechanical monocyte-EC interactions.

Keywords

Monocyte, Endothelial Cell, PECAM-1, Transmigration, Atherosclerosis

Paper information

Ken HASHIMOTO, Noriyuki KATAOKA, Emi NAKAMURA, Takeaki OKAMOTO, Hiroaki KANOUCHI, Yohsuke MINATOGAWA, Satoshi MOHRI, Katsuhiko TSUJIOKA and Fumihiko KAJIYA, “An Experimental Model for Studying Molecular Behavior of Platelet-Endothelial Cell Adhesion Molecule-1 during Mechanical Interactions between Monocytes and Vascular Endothelial Cells”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 4 (2010), pp.281-290 . doi:10.1299/jbse.5.281

We evaluated mechanical states in an atheromatous artery and correlated these values with both lipoprotein retention in a regionally thickened wall and the rupture of a luminal plaque. We used two specimens of common carotid arteries dissected at autopsy; one specimen had diffuse intimal thickening and the other had an atherosclerotic plaque. Mechanical properties were identified by cyclic inflation tests. Stress-released geometries were obtained ring specimens via a radial cut. Finite element (FE) analyses were performed on the stress-released geometry, postulating two incompressible isotropic hyperelastic models for the vascular tissues and a lipid pool. Stress/strain values and their variations were obtained under a constant axial stretch of 1.07 and intraluminal pressures ranging from 10 to 16 kPa. Light microscopy was also performed on stained specimens. Results from the FE analysis showed that the variation in maximum principal stress was ‹ 10 kPa in the deep intimal layer of a regionally thickened wall. Maximum principal stress and variation concentrated at 655 kPa and 281 kPa, respectively, at a shoulder in the plaque cap region. Maximum principal strain variation in the region of the atheromatous plaque was much lower than in the corresponding region of the artery with intimal thickening. Low stress/strain variations are likely to retain the lipid pool after formation in the thickened wall region, where the convection force seems to be very low. Both concentrations of stress and variations in stress are likely to cause a rupture at the plaque cap shoulders, which are one of the reported sites.

Keywords

Atherosclerotic Plaque, Carotid Artery, Finite Element Analysis, Plaque Rupture, Residual Strain, Retention of Lipoprotein

Paper information

Hiroshi YAMADA, Kazuhiro YURI and Noriyuki SAKATA, “Correlation between Stress/Strain and the Retention of Lipoproteins and Rupture in Atheromatous Plaque of the Human Carotid Artery: A Finite Element Study”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 4 (2010), pp.291-302 . doi:10.1299/jbse.5.291

Coronary arterial flow can be described in terms of an intramyocardial pump that displaces blood backward and forward during systole and diastole, which is termed diastolic predominant flow. When the diastolic predominant flow runs through the stenotic arteries, the geometric characteristics and mechanical properties of these arteries may influence the flow. We have developed an experimental system to represent this diastolic predominant flow phenomenon. To produce a stenosis model, polyvinyl alcohol hydrogel was shaped into various forms of diseased coronary stenosis. The mechanical properties of this stenosis model are similar to human coronary arteries. We then examined the effects of stenosis severity, stiffness, and curvature on flow and pressure. A change in curvature had only a minimal affect on flow, while stenosis severity and the stiffness parameter significantly influenced diastolic predominant pulsatile flow.

Keywords

Atherosclerosis, Stenosis, Diastolic Predominant Flow, Pulsatile Flow, Biomechanics

Paper information

Jie JI, Shunichi KOBAYASHI, Hirohisa MORIKAWA, Dalin TANG and David N. KU, “Diastolic Predominant Flow in Compliant Coronary Stenosis Model”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 4 (2010), pp.303-313 . doi:10.1299/jbse.5.303