Fluid Shear Stress Exposure Research Articles

Parallel-plate Flow Chamber and Continuous Flow Circuit to Evaluate Endothelial Progenitor Cells under Laminar Flow Shear Stress

The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses. Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs. This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts. The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (> 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12).

せん断応力負荷下で内皮細胞を培養した疑似血管マイクロデバイスの開発と形態変化の計測(流体工学,流体機械)

せん断応力負荷下で内皮細胞を培養した疑似血管マイクロデバイスの開発と形態変化の計測(流体工学,流体機械)

The Change of F-actin Distribution and Morphology of Cultured Bovine Aortic Endothelial Cells in the Early Stage of Fluid Shear Stress Exposure.

The time course changes of F-actin distribution and morphology of cultured bovine aortic endothelial cells under shear flow conditions were analyzed. Fully confluent endothelial cells cultured on glass were subjected to fluid shear stress of 2 Pa. Experiments were performed for one-way flow for 20, 40 min, 1, 3 and 6 hours. After the flow exposure F-actin filaments were stained with rhodamine-phalloidin. The morphological parameters of endothelial cells (shape index and angle of cell orientation), the appearance frequency of the stress fibers and the angle of stress fiber orientation were measured. F-actin filaments were mainly localized at periphery of the cells, although some filaments were seen as star-like configurations in the center portion under no-flow conditions. In some cells (16%) exposed to shear stress for 20 min, stress fibers which were aligned with cell axes were partly observed. In this stage, however, cell morphological changes were not observed. In many cells (64%) exposed to shear stress for 1 hour, the star-like structure of filaments disappeared in the center portion, and stress fibers appeared. After 6 hours, stress fibers were observed in the most cells (91%) and began to align with flow direction. The cells in which stress fibers appeared significantly elongated, but the cells without stress fibers had kept their polygonal shape. From these results, it is expected that F-actin filaments may play a major role for sensing the level and direction of shear stress and for changing morphology of endothelial cells.

Modulation of secretion of vasoactive materials from human and bovine endothelial cells by cyclic strain

The effects of cyclical expansion and elaxation of the vessel wall on endothelial cell metabolism have been modeled using a uniaxial strain device and cultured endothelial cell monolayers. Also, the effects of stopping and then restarting cyclic strain on metabolite secreation rates were determined. Secretion rates of prostacyclin (PGI(2)), endothelin, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor-type 1 (PaI-1) by endothelial cells were constant over24-h periods The secreation of both PGI(2) and endothelin was enhanced in cells exposed to high physiological levels of cyclical strain (10% at 1Hz) compared with controls, while tPA production was unaltered. These results were true for both human and bovine endothelial cells. Characterization of the response of human endothelial cells to cyclical strain made evaluation of stretch effects on PAl-1 secretion possible. A nearly twofold increase in PAl-1 secretion by cells exposed to arterial levels of strain was observed. Endothelin secretion remained elevated even after strain was stopped for 12 h, while PGl(2) secretion returned to control values upon cessation of cyclic stretch. These results indicate that physiological levels of cyclic mechanical strain ca significantly modulate secretion of vasoactive metabolited form endothelial cells. The changes sen secretion are, in some cases, quite different from those caused by arterial levels of fluid shear stress exposure. (c) 1994 John Wiley & Sons, Inc.