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 inflammatory response to biomaterials. In the present study the adhesion, viability and apoptotic changes in material surface adherent monocytes during the first hours of cell-surface interactions in vitro were studied, using tissue culture polystyrene surfaces coated with human albumin and fibrinogen. Human peripheral blood monocytes were enriched by a two-step gradient centrifugation and resuspended (1×10 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°C (5% CO 2, 100% humidity) for 30 min, 1, 2, 3 and 24 h. The adherent cells were stained for early apoptotic changes (exposed phosphatidylserine) and cell death using Annexin-V-fluorescein and propidium iodide staining, respectively. A bi-phasic adhesion was observed on the fibrinogen coated surface, having the highest number of adherent 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 after 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 (∼30%) and fibrinogen (∼15%). In the 24 h cultures, the viability of adherent cells was high on both surfaces (95–100%). Viable cells staining positive for early apoptotic changes could only be clearly observed on the albumin coated surface, after 30 min of cell–material surface interaction. Cell death, including apoptotic death, thus seems to play an important role during the initial interactions between monocytes and a foreign surface.