Characterization of novel clonal murine endothelial cell lines with an extended life span

A murine endothelial cell line was recently established from microvessels t hat had invaded a subcutaneous sponge implant (Dong, Q. G.; Bernasconi, S.; Lostaglio, S., et al. Arterioscl. Thromb. Vase. Biol. 17:1599-1604; 1997). From these sponge-induced endothelial (SIE) cells, we have isolated two su bpopulations endowed with different phenotypic properties. Clone SIE-F cons ists of large, highly spread cells that have a relatively slow growth rate, form contact-inhibited monolayers, do not grow under anchorage-independent conditions, express elevated levels of thrombospondin-1 (TSP-1) and are no t tumorigenic in vivo. In contrast, clone SIE-S2 consists of small, spindle -shaped cells that have a high proliferation rate, do not show contact-inhi bition, grow under anchorage-independent conditions, express very low level s of TSP-1 and are tumorigenic in vivo. Both clones express the endothelial markers vascular endothelial-cadherin and vascular intercellular adhesion molecule-1, but do not express CD31 and E-selectin. In addition, SIE-S2 cel ls, but not SIE-F cells, express the alpha-smooth muscle actin isoform. SIE -SE cells, but not SIE-F cells, are able to form branching tubes in fibrin gels. The SIE-F and SIE-S2 clones, which have properties of nontransformed and transformed cells, respectively, should provide useful tools to investi gate physiological and pathological processes involving Vascular endotheliu m.