Angiogenic activity of MMEC CM in the CAM sponge assay. (A) The positive control (RPMI-1640 + bFGF) and (B) the CM were loaded onto gelatin sponges (^* and ^**) implanted on top of the CAM on day 8. Macroscopic view of the CAM on day 12, showing numerous new capillaries with a “spoked wheel” pattern around both sponges. (C) Histologic sections of the sponge shown in panel B, showing a collagenous matrix pierced by winding blood vessels (arrows) cut on different planes and containing blood cells. (D) Histologic section of a sponge loaded with the HUVEC CM, showing no vessels among the trabeculae. Similar results (not shown) were produced by the negative control (RPMI-1640 medium). Bar = 4mm (A-B) and 90 μm (C-D).