Neutrophil-endothelial interactions in a cell-column model of the microvasculature: effects of fMLP.

Abstract

The purpose of this study was to develop an in vitro model which, compared to stagnant two-chamber systems, is more analogous to the rheological conditions found in the vasculature and permits near simultaneous measurement of polymorphonuclear leukocytes (PMN) entrapment and endothelial, monolayer permeability. A previously described cell-column model of the vasculature was perfused with 2 x 10(6) PMN/ml at an average fluid velocity of 0.09 cm/s and an average estimated endothelial surface shear stress of 4.5 dyne/cm2 for a total of 60 min. PMN entrapment was estimated from counts of PMN in this recirculating system. Bovine endothelial permeability was estimated from an indicator dilution analysis of the three co-injected dyes: blue dextran (molecular weight [MW]) 2 x 10(6), sodium fluorescein (MW 342) and cyanocobalamin (MW 1355). Circulation of PMN through cell-columns did not activate PMN, although the number of circulating PMN decreased at a rate of 14% per 65 cm2 of endothelial surface in the first 15 min. Endothelial cell monolayer permeability did not change within 60 min. Addition of formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-5) M) activated PMN and significantly increased entrapment of circulating PMN to 27% per 65 cm2 in the first 15 min. Although the percentage of circulating PMN entrapped increased, endothelial monolayer permeability was not increased by either the addition of 10(-5)M fMLP or PMN + fMLP to the cell-column perfusate. Over the 60-min period studied, entrapment of PMN within a recirculating model of the microvasculature was not associated with an increase in endothelial permeability even after PMN stimulation with fMLP.