Human dermal microvascular endothelial cells express the 140-kda isoform of neural cell adhesion molecule

It has only recently been appreciated that the level of gene expression of cell surface markers can be different in endothelial cells derived from different anatomical sites, and that these differences can persist in vitro. In this study, we identify an immunoglobulin gene superfamily member, neural cell adhesion molecule (NCAM), that is expressed on the cell surface of human dermal microvascular endothelial cells but not on umbilical vein, pulmonary vein, aorta, or pulmonary artery derived endothelial cells. By western blot analysis, we identified the 140 kD isoform of NCAM on the surface of human dermal microvascular endothelial cells (HDMEC) derived from dermis. Isolates of HDMEC from human foreskin reproducibly expressed high levels of cell surface immunoreactive protein. In contrast, endothelial cells from large vessels never expressed NCAM constitutively and could not be induced to express NCAM by three proinflammatory cytokines. Western blot analysis of membrane preparations of HDMEC indicated that NCAM protein migrated as a single species with a molecular mass of 140 kD. RT-PCR identified NCAM mRNA in HDMEC cells. The potential for expression of NCAM on small vessels in skin can be interpreted in different ways. Members of the immunoglobulin gene family, including ICAM-1, ICAM-2, and VCAM-1, can be expressed on the cell surface of all endothelial cells and serve as adhesion molecules for leukocytes. It is also possible that, by analogy, NCAM serves as a ligand for a receptor on leukocytes, particularly those that also express NCAM (e.g., natural killer cells). Alternatively, it is possible that NCAM expression permits endothelial cell-cell adhesion, enhancing the structural integrity of microvessels or facilitates neural interactions with microvascular endothelium.