Differential monocytic cell adherence to specific anatomic regions of the canine aorta

Circulating monocytes and vascular endothelial cells (EC) interact in a complex and dynamic manner that varies between vascular beds. The objective of this study was twofold: to ascertain if monocytic cell adhesion to vascular endothelium differed between specific anatomic regions of the canine aorta, and to investigate the effect of known EC stimulators on monocytic cell adhesion to cells from these regions. Initial in vitro studies measuring adherence of U937 cells, a human monocytic cell line, to canine jugular vein and aortic EC monolayers revealed a dose-dependent increase in adhesion to EC stimulated with interleukin-1 (IL-1), lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate (PMA), or thrombin. While there was no regional difference in monocytic cell adherence to unstimulated EC in tissue culture, studies demonstrated greater monocytic cell adhesion to stimulated EC cultured from the distal versus proximal aorta. In organ culture, unstimulated adhesion of U937 cells or autologous monocytes was significantly greater to the distal aorta than the proximal aorta. Although monocytic cell adhesion to both the proximal and distal aorta increased with stimulation, the percentage increase in the proximal aorta, 1,086% with IL-1, 237% with PMA, 209% with LPS, and 174% with thrombin, was greater than in the distal aorta, demonstrating a significant functional difference in the endothelium from separate anatomic regions of a single vessel. This may have a direct relevance to the regional specificity of vascular disease.