Regulation of vasculogenesis by platelet-mediated recruitment of bone marrow-derived cells
Bone marrow-derived cells contribute to physiological and pathological vascular remodeling throughout ontogenesis and adult life. During tissue regeneration and tumor growth, the release of cytokines and chemokines mediates the recruitment of hematopoietic and endothelial progenitor cells that contribute to the assembly of neovessels. Current evidence implies that platelets contribute structurally and instructively to vascular remodeling. Platelets adhere almost immediately to exposed or activated endothelium, and they are major storage and delivery vehicles for pro- and antiangiogenic growth factors including VEGF-A and thrombospondin (TSP), and cytokines and chemokines, such as stromal-derived factor 1 (SDF-1). By site-specific deployment of these factors, platelets orchestrate the local angiogenic stimulus within a tissue and direct the recruitment and differentiation of circulating bone marrow-derived cells. These insights have profound clinical implications; inhibition of platelet-deployed growth factors or their receptors may be an effective strategy to block tumor growth, whereas activation of these pathways may be used to accelerate revascularization and tissue regeneration.