In vitro study of monocyte viability during the initial adhesion to albumin- and fibrinogen-coated surfaces

Surface adherent monocytes and macrophages play a central role in the infla mmatory response to biomaterials. In the present study the adhesion, viabil ity and apoptotic changes in material surface adherent monocytes during the first hours of cell-surface interactions in vitro were studied, using tiss ue culture polystyrene surfaces coated with human albumin and fibrinogen. H uman peripheral blood monocytes were enriched by a two-step gradient centri fugation and resuspended (1 x 10(6)/ml) in RPMI with 10% fetal bovine serum . The cells were added to polystyrene surfaces coated with human fibrinogen or albumin and incubated in 37 degreesC (5% CO2, 100% humidity) for 30 min , 1, 2, 3 and 24 h. The adherent cells were stained for early apoptotic cha nges (exposed phosphatidylserine) and cell death using Annexin-V-fluorescei n and propidium iodide staining, respectively. A bi-phasic adhesion was obs erved on the fibrinogen coated surface, having the highest number of adhere nt cells after 30 min and 24 h, while the cell number was markedly reduced after 1-3 h. The number of adherent cells on albumin was relatively low aft er all short time incubations but had reached a high level after 24 h. The number of adherent dead cells was highest after 1 h on both albumin (simila r to 30%) and fibrinogen (similar to 15%). In the 24 h cultures, the viabil ity of adherent cells was high on both surfaces (95-100%). Viable cells sta ining positive for early apoptotic changes could only be clearly observed o n the albumin coated surface, after 30 min of cell-material surface interac tion. Cell death, including apoptotic death, thus seems to play an importan t role during the initial interactions between monocytes and a foreign surf ace. (C) 2001 Elsevier Science Ltd. All rights reserved.