UREMIC MEDIUM CAUSES ENDOTHELIAL-CELL DYSFUNCTION CHARACTERIZED BY ANALTERATION OF THE PROPERTIES OF ITS SUBENDOTHELIAL MATRIX

Uraemic patients suffer from haemorrhagic disorders and accelerated at herosclerosis. To evaluate the possible role of the vessel wall in the se haemostatic alterations associated with uraemia, we investigated th e effect of a uraemic milieu on human endothelial cell (EC) cultures a nd the reactivity of the extracellular matrices (ECM) generated by the se cells towards platelets. EC cultures were exposed to a pool of sera (20% in the culture medium) obtained either from uraemic patients or from normal donors, and the following parameters were evaluated: (1) E C viability (trypan blue exclusion test); (2) von Willebrand factor (v WF) levels in supernatants and associated with ECM; (3) the reactivity of EC and EC-derived ECM towards platelets, measured 'ex vivo' under flow conditions (5 min, wall shear rate 800 s(-1)); and (4) ultrastruc ture of the ECM. The viability of EC cultured in the presence of uraem ic sera was similar to controls. Platelet interaction with ECM generat ed by EC exposed to uraemic sera was significantly reduced (P<0.05). T his decrease was mainly related to a reduction in platelet adhesion (9 .8 +/- 1.9% vs 16.7 +/- 1.8% in controls, P<0.02). VWF levels in super natants and associated with ECM were similar to controls. Ultrastructu ral analysis of the ECM generated by EC exposed to uraemic sera reveal ed a deficient matrix. An increased removal of EC was observed in expe riments in which EC cultured in the presence of uraemic sera were perf used with citrated blood. These results indicate that a uraemic milieu induces quantitative and qualitative changes in the vascular subendot helium, characterized by a less intrincate network of fibrils, as well as a decreased attachment of EC and reduced thrombogenicity to the EC M. These changes may represent another mechanism which contributes to the haemostatic dysfunction observed in uraemic patients.