Immortalisation of human bone marrow endothelial cells: characterisation of new cell lines

Background Adhesion of haematopoietic progenitor cells (HPC) to human bone marrow endothelial cells (HBMEC) plays a key role in homing of HPC to bone marrow. Here we describe four new HBMEC cell lines that can be used to stud y the (specific) adhesion of HPC to HBMEC. Design HBMEC were immortalised with a retroviral construct containing the h uman papilloma virus 16 E6/E7 genes. Four cell lines were characterised. Results The cell lines showed their endothelial nature by the expression of von Willebrand Factor and VE-cadherin (CD144). Electron microscopic analys is revealed normal endothelial-cell characteristics, including the presence of Weibel-Palade bodies and intercellular junction structures. An extensiv e phenotypic analysis of the cell-lines was performed, they were found to r esemble primary HBMEC. The only difference found was the absence of express ion of E-selectin (CD62e) and VCAM-1 (CD106) on resting HBMEC cell lines. U pon stimulation with IL-1 beta the expression of E-selectin, VCAM-1 and ICA M-1 (CD54) was upregulated. All resting cell lines bound CD34(+) HPC. Adhes ion was increased by addition of the phorbol ester PMA. Two cell lines show ed increased binding upon IL-1 beta prestimulation. Highest adhesion was ob served after the combination of IL-1 beta prestimulation of the endothelial cells and addition of PMA. Binding of CD34(+) HPC to HBMEC was compared wi th the binding to human umbilical vein endothelial cell lines and to a huma n dermal microvascular endothelial cell line (HMEC-1). So far, we have only found relatively less binding of HPC to IL-1 beta prestimulated HMEC-1 cel ls, which could be explained by a reduced induction of E-selectin and VCAM- 1 upon IL-1 beta stimulation of these cells. Conclusion The immortalised HBMEC cell lines have maintained their normal p henotype for the majority of characteristics examined. The expression of E- selectin and VCAM-1, which are not constitutively expressed on the cell lin es, can be induced by stimulation of the endothelial cells with IL-1 beta. The cell lines have furthermore maintained their capability to bind HPC. Th ey will therefore be useful to investigate the interactions between HPC and HBMEC involved in homing of HPC.