Abstract 986: Platelets Secrete SDF-1Alpha and Recruit Bone Marrow-derived Progenitor Cells to Arterial Thrombi in vivo
The accumulation of smooth muscle and endothelial cells is essential for remodeling and repair of injured blood vessel walls. Bone marrow-derived progenitor cells have been implicated in vascular repair and remodeling; however, the mechanisms underlying their recruitment to the site of injury remain elusive. Here, we show using real-time in vivo fluorescence microscopy that platelets provide the critical signal that recruits CD34+ bone-marrow cells and Sca-1+ c-Kit+ Lin− bone marrow-derived progenitor cells to sites of vascular injury. Correspondingly, specific inhibition of platelet adhesion virtually abrogated the accumulation of both CD34+ and Sca-1+ c-Kit+ Lin− bone marrow-derived progenitor cells at sites of endothelial disruption. Binding of bone-marrow cells to platelets involves both P-selectin and GPIIb integrin on platelets. Unexpectedly, we found that activated platelets secrete the chemokine SDF-1alpha, thereby supporting further primary adhesion and migration of progenitor cells. These findings establish the platelet as a major player in the initiation of vascular remodeling, a process of fundamental importance for vascular repair and pathological remodeling after vascular injury.