Effect of BMP4 on the angiogenic activity of Drm/gremlin. (A) The chemotactic activity of a suboptimal concentration of rDrm (5.0 ng/mL) was tested on MAE cells in a Boyden chamber assay in the presence of increasing concentrations of BMP4 (•); in parallel, the chemotactic activity of BMP4 alone was tested on the same cells (○). (B) Chick embryo CAM implants were loaded with vehicle, BMP4, rDrm, or rDrm plus BMP4 (both molecules were tested alone or in combination at 50 or 100 ng/implant). After 4 days, blood vessels converging versus the implant were counted. Data are expressed as mean ± SD.