Executive Summary
Cell
adhesion to the microvascular endothelium is recognized as a crucial initial
step in the extravasation of leukocytes in the inflammatory response and
tumor cells in metastasis processes. The process of adhesion involves a
complex balance of forces resulting from hydrodynamic shear forces and the
adhesive bonds between the adhering cells and the endothelium. Experimental
models that mimic the flow conditions in microcapillaries have suggested
that the local shear stresses and shear rates can mediate the ability of
tumor cells and leukocytes to arrest on the endothelium and sustain
adhesion. However, further investigation has been limited by the lack of
experimental models that allow quantitative measurement of the hydrodynamic
environment over adherent cells.
To aid
Professor Cheng Dong’s research in extravasation, a system has been designed
that that is capable of acquiring quantitative flow profiles over adherent
cells. By combining the techniques of side-view imaging and particle image
velocimetry (PIV), an in vitro model was constructed that is capable
of obtaining quantitative flow data over cells adhering to the endothelium.
Velocity profiles have been generated with the side-view PIV system over
adherent 16 μm-diameter fluorescent beads and adherent leukocytes and
analysis has been useful in comparing the shear rates over a leukocyte
adhering to the endothelium under low and high upstream wall shear. This
device provides a means for future study of the forces underlying adhesion
by permitting characterization of the local hydrodynamic conditions over
adherent cells.
