Measurement of plaque-forming macrophages activated by lipopolysaccharide in a micro-channel chip.
OBJECTIVE
In the present study, micro-channel arrays were fabricated on the surface of plastic-based disposable chips. The cell adhesion process and the detection of plaque-forming macrophages were observed. Further, we evaluated cell adhesion in a fluid system in vitro.


METHODS
Features of the micro-channel (1.4 mm wide and 10 mm long) included twenty micro-pillars (with a projection of 200 microm diameter and 250 microm high) coated in a 50 microm thick silicon rubber layer, which were regularly arranged at the bottom of each channel. The efficiency of cell capture was expected to increase by arrangement of micro-pillars in a micro-channel. Mouse macrophage RAW264.7 cells, stimulated for 24 h with lipopolysaccharide (LPS) derived from periodontopathic bacteria, were circulated continuously for 2 h at room temperature by the pump in a chip.


RESULTS
Control cells had not formed plaques on micro-pillars 20 min into the experiment. By contrast, LPS-activated macrophages produced plaques at the side walls of micro-pillars after 20 min. The plaques grew during the flow test, and image shading became clearer with increasing flow time for 120 min. The maximal adhesion rate per unit area appeared at 20% for control cells, whereas the peak was shifted to 30% for LPS-activated macrophages (n = 20). The average adhesion rate was 3.0 +/- 2.0% for control cells and 5.0 +/- 3.9% for LPS-activated macrophages (n = 100).


CONCLUSIONS
These findings indicate that LPS-activated macrophages accumulate in micro-channel arrays, and suggest that macrophage plaque formation is a two-step procedure: (1) LPS-activated macrophages adhere physically to the silicon rubber layer on micro-pillars; and (2) consequently, the cells adhere to the activated macrophage layer.
Isoda
T
T
Department of Life and Environment Engineering, Faculty of Environmental Engineering, University of Kitakyushu, Wakamatsu, Kitakyushu, 808-0135, Japan.
Tsutsumi
T
T
Yamazaki
K
K
Nishihara
T
T
D016976:Aggregatibacter actinomycetemcomitans / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement; D004867:Equipment Design; D007091:Image Processing, Computer-Assisted; D056656:Lab-On-A-Chip Devices; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects*; D051379:Mice; D012212:Rheology; D012826:Silicone Elastomers; D013499:Surface Properties; D013997:Time Factors
D008070:Lipopolysaccharides; D012826:Silicone Elastomers