Recently we have shown that G6-31, a monoclonal antibody that blocks VEGF, had unexpected pro-angiogenic effects, reversing the rarefied peripheral lung microvasculature and restoring the tissue TSP-1 and Ang-2 levels in Eng+/- and Alk1+/- mouse models of HHT, respectively (Ardelean et al., 2014a; Table 1). This evidence concerns the gene THBS1 and hereditary hemorrhagic telangiectasia.