Angiogenesis is regulated by a novel mechanism: pro- and antiangiogenic proteins are organized into separate platelet α granules and differentially released

Platelets, in addition to their function in hemostasis, play an important role in wound healing and tumor growth. Because platelets contain angiogenesis stimulators and inhibitors, the mechanisms by which platelets regulate angiogenesis remain unclear. As platelets adhere to activated endothelium, their action can enhance or inhibit local angiogenesis. We therefore suspected a higher organization of angiogenesis regulators in platelets. Using double immunofluorescence and immunoelectron microscopy, we show that pro- and antiangiogenic proteins are separated in distinct subpopulations of alpha-granules in platelets and megakaryocytes. Double immunofluorescence labeling of vascular endothelial growth factor…