OBJECTIVETo investigate endothelial cell adhesion molecule expression and leucocyte adhesion to endothelial cells isolated from the microvasculature of rheumatoid arthritic synovial tissue (SMEC) in comparison with similar cells isolated from healthy subcutaneous adipose tissue (ADMEC) or from umbilical veins (HUVEC).
METHODSCultured endothelial cells were treated with tumour necrosis factor  (TNF) for 2-24 hours before the assessment of cell surface E-selectin, vascular (VCAM-1) or intercellular cell adhesion molecule-I (ICAM-1) expression. Neutrophil and T lymphocyte adhesion to TNF treated endothelial cells was assessed using static and shear dependent assay systems.
RESULTSVCAM-1 expression by SMEC was significantly less sensitive to TNF stimulation than HUVEC or ADMEC. E-selectin expression by SMEC appeared to be more sensitive to TNF stimulation and maximal expression was about 30% greater in comparison with HUVEC or ADMEC. Sensitivity to TNF induction and maximal ICAM-1 expression was similar in all three endothelial cell types. Static neutrophil adhesion to TNF stimulated SMEC was significantly increased in comparison with HUVEC, however this phenomenon was dependent on the presence of neutralising antibodies to ICAM-1. At shear rates in excess of 2.4 dynes/cm² significantly more neutrophils and, predominantly CD45RO+, T lymphocytes adhered to TNF stimulated SMEC than HUVEC.
CONCLUSIONRheumatoid synovial endothelial cells differentially regulate E-selectin and VCAM-1. The increased ability of TNF stimulated synovial endothelial cells to support leucocyte adhesion may help to explain the leucocyte, in particular CD45RO+ T-lymphocyte, recruitment observed in the rheumatoid synovium.