Expression of cell-cell and cell-matrix adhesion proteins by sinusoidal endothelial cells in the normal and cirrhotic human liver

We compared the expression of cell-cell and cell-matrix adhesion proteins by sinusoidal endothelial cells in normal human liver, in which the endothetial lining of hepatic sinusoids is discontinuous and devoid of basement membrane, and in cirrhosis, during which sinusoids might undergo a process of capillarization and acquire a continuous lining and a typical basement membrane. In normal liver, sinusoidal endothelial cells displayed a very restricted repertory of cell-adhesion molecules: the intercellular adhesion molecules PECAM-1 and CD34 were undetectable and only two integrins, α₁β₁ and α₅β₁, were present, whereas the laminin receptors α₆β₁ and α₂β₁ were undetectable and the β₃ integrins were faintly expressed. In capillarized sinusoids, sinusoidal endothelial cells displayed striking changes in their repertory of cell-adhesion molecules, including the expression of PECAM-1 protein and messenger RNAs and the induction of the laminin receptors α₆β₁ and α₂β₁. Such changes co-localized with subendothelial laminin deposits. In conclusion, normal sinusoidal endothelial cells express a distinctive set of cell-adhesion molecules, adapted to their structural and microenvironmental characteristics, and this repertory is dramatically modified during sinusoidal capillarization, possibly as a consequence of the concomittant matrix changes.