Mononuclear cell chemoattractant activity from cultured arterial smooth muscle cells

Conditioned media from cultures of baboon aortic endothelial and medial smooth muscle cells (SMC) were assayed for effects on human peripheral blood mononuclear cell migration in vitro using blind well chambers with 5-μm-pore polycarbonate membranes. Media from serum-containing endothelial cell and serum-free SMC cultures had no significant influence on migration, but mononuclear cell migration was significantly enhanced by serum-containing SMC-conditioned media, an increase which was due to chemotaxis and not merely activated random migration. A chemotactic dose response was demonstrated, with activity diminishing with increasing dilution. The diminished activity was, however, not proportional to the level of dilution, possibly indicating the presence of an inhibitor. Chemoattractant activity was heat stable at 56 and 80°C for 30 min, but was largely abolished upon boiling. Addition to the conditioned media of antisera to C5 and C3 did not diminish the chemoattractant activity, making these components of complement an unlikely source of the activity. The possible nature of the SMC-generated chemoattractant(s) has been discussed. It is suggested that this SMC-derived chemoattractant for blood mononuclear cells may play a role in arterial monocyte-macrophage recruitment to the normal or atheromatous arterial intima.