CHARACTERIZATION OF A NEWLY ESTABLISHED HUMAN BONE-MARROW ENDOTHELIAL-CELL LINE - DISTINCT ADHESIVE PROPERTIES FOR HEMATOPOIETIC PROGENITORS COMPARED WITH HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS

Human bone marrow endothelial cells (HBMEC) are intimately involved in the homing of hematopoietic progenitor cells (HPC) to the bone marrow and in the regulation of proliferation and differentiation of these c ells. Because availability of primary HBMEC and their capacity to be c ultured in vitro are limited, we used isolated HBMEC to establish a cl oned cell line by microinjection of a recombinant plasmid expressing s imian virus 40 early genes under the control of a deletion mutant of t he human vimentin promoter. Serum requirements for growth of a transfo rmed HBMEC line (TrHBMEC) were markedly decreased compared with those of primary cells, and added growth factors were not required for proli feration. Cells took up acetylated low-density lipoprotein normally, b ound to Ulex europaeus lectin, and stained positively for von Willebra nd factor, P-selectin, CD31, CD34, CD44, very late antigen-5, and inte rcellular adhesion molecule-2 (ICAM-2). After treatment with TNF-alpha or lipopolysaccharide, TrHBMEC increased surface expression of E-sele ctin, vascular cell adhesion molecule-1 (VCAM-1), and ICAM-1 in a mann er similar to primary HBMEC. In contrast, IL-1 beta elicited much less up-regulation of these adhesion molecules than in primary cells. In p revious work, we reported that, in a flow adhesion model, rolling of p eripheral blood CD34(+) cells on primary HBMEC was E-selectin-dependen t, whereas VCAM-1 and ICAM-1 contributed to firm adhesion. In the pres ent study, we show that HPC adhere in a similar way to TrHBMEC. A less -pronounced role for VCAM-1 and ICAM-1 was found in the adhesion of HP C to human umbilical vein endothelial cells. Furthermore, significantl y more CD34(+) cells adhered to TNF-alpha-stimulated HBMEC and TrHBMEC than to similarly stimulated human umbilical vein endothelial cells. These data emphasize the importance of using microvessel HBMEC for stu dying the homing of HPC to the bone marrow, and indicate the usefulnes s of the above-described bone marrow endothelial cell line.