USE OF AN INTEGRATED FLOW-CHAMBER ADHESION ASSAY FOR MEASURING LEUKOCYTE ADHESION PROPERTIES IN SIMULATED AND ACTUAL MICROGRAVITY

Microgravity can modify host cell-cell and cell-matrix interactions, and thereby exert potentially deleterious effects on human vascular and immune functions and regeneration processes. To better understand these effects, many investigators have used rotating wall vessels (RWV) to simulate microgravity on the ground. However, adhesion assays as currently conducted require that rotation be stopped, a sample removed, and cells prepared before an adhesion assay can be performed. The entire process from cell sampling to completion of an adhesion assay can take hours, giving the cells time to recover at 1g and complicating interpretation of results. Our integrated RWV/flow chamber adhesion assay system can assay adhesion of cells experiencing simulated microgravity within seconds of returning to 1g, without stopping rotation of the chamber. We have assayed both integrin- and selectin-mediated adhesion with this system and compared it to results obtained using a conventional shear-flow adhesion assay system. Our data show that the new integrated assay can detect defects in both rolling and firm adhesion with sensitivity equal to that of large, microscope-based flow chamber adhesion assays. In addition, this system has now been adapted to measure acute effects of actual microgravity in parabolic flight experiments. Lessons learned from development of this Earth-based system can form the basis for a future instrumentation to allow NASA to monitor microgravity-inducible immune-system function during space flights.