Microvascular Endothelial Cells Differ in Their Basal and Tumour Necrosis Factor-α-Regulated Expression of Adhesion Molecules and Cytokines

We recently located a rare cytokeratin-positive (CK+) type of microvascular endothelial cell (MVEC) in the corpus luteum and aorta. Bovine corpus luteum MVEC are known to be involved in the cyclic accumulation of eosinophils and macrophages. Since leukocyte migration is specifically mediated by adhesion molecules and the release of cytokines, we compared the expression of these factors in basal and TNF-α-stimulated CK+ MVEC and in common cytokeratin-negative (CK–) MVEC in order to obtain an initial insight into the functional capacities of CK+ MVEC. CK– MVEC revealed significantly higher basal RANTES mRNA expression than CK+ MVEC, and TNF- α up-regulated RANTES mRNA in both types of MVEC. Only resting and stimulated CK– MVEC expressed granulocyte-macrophage colony-stimulating factor mRNA. Both MVEC types expressed monocyte colony-stimulating factor mRNA, but remained negative for eotaxin and interleukin (IL)-5 mRNA even after stimulation. Resting CK+ MVEC were positive for CD29, CD31, CD49a and CD49e, but expressed most of these antigens at a significantly lower density than did CK– MVEC. In contrast to CK– MVEC, CK+ MVEC failed to express CD49b or MHC class II. The activation of CK+ MVEC with TNF-α induced the expression of CD62P, but not of CD49b or MHC class II. In summary, phenotypically variable MVEC derived from the microvascular bed of one organ differ in their TNF-α-regulated expression of cytokine mRNA and adhesion molecules. Morphological heterogeneity is related to a particular specialisation of functional MVEC.