Involvement of the VEGF receptor VEGFR2 in OPG mediated endothelial tube formation. HuDMECs were cultured on growth factor reduced matrigel for 8 hours and branch point number counted as described in materials and methods. (a) Untreated control, (b) VEGF 10 ng/ml, (c) VEGF 10 ng/ml and VEGFR2 neutralising antibody (1 μg/ml), (d) OPG 100 ng/ml, (e) OPG 100 ng/ml and VEGFR2 neutralising antibody (1 μg/ml). (f) Quantification of tube formation through measurement of branch point number. Data represented as mean ± S.E.M. from three independent experiments performed in triplicate. ***, p < 0.001 compared to VEGF in combination with VEGFR2 antibody; NS, no significant difference.