ABSTRACT
Tissue injury is inevitably accompanied by disruption of the endothelium and exposure of the subendothelial matrix. To generate a guidance molecule directing progenitor cells to sites of vascular lesions, we designed a bifunctional protein. The protein consists of the soluble platelet collagen receptor glycoprotein VI and an antibody to CD133 (hereafter called GPVI-CD133). In vitro and in vivo, this construct substantially mediates endothelial progenitor cell (EPC) homing to vascular lesions. Exposure of EPCs to GPVI-CD133 did not impair their capability to differentiate toward mature endothelial cells as verified by the formation of colony-forming units, the upregulation of endothelial markers CD31 and CD146 analyzed by flow cytometry or von Willebrand factor and endoglin assessed by immunofluorescence microscopy, as well as the presence of Weibel-Palade bodies using transmission electron microscopy. In vivo, GPVI-CD133 augments reendothelialization of vascular lesions. Thus, this bifunctional protein could be a potential new therapeutic option for cardiovascular diseases.
Subject(s)
Antibodies, Monoclonal/metabolism , Blood Vessels/pathology , Endothelial Cells/metabolism , Endothelium, Vascular , Neovascularization, Physiologic , Stem Cells/metabolism , AC133 Antigen , Animals , Antigens, CD/genetics , Antigens, CD/metabolism , Antigens, CD34/genetics , Antigens, CD34/metabolism , Biomarkers/metabolism , Blood Vessels/physiology , Cell Adhesion/physiology , Endothelial Cells/cytology , Endothelium, Vascular/cytology , Endothelium, Vascular/pathology , Endothelium, Vascular/physiology , Glycoproteins/genetics , Glycoproteins/metabolism , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Inbred NOD , Mice, SCID , Peptides/genetics , Peptides/metabolism , Platelet Membrane Glycoproteins/genetics , Platelet Membrane Glycoproteins/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Regeneration/physiology , Stem Cells/cytologyABSTRACT
BACKGROUND: Peripheral homing of progenitor cells in areas of diseased organs is critical for tissue regeneration. The chemokine stromal cell-derived factor-1 (SDF-1) regulates homing of CD34+ stem cells. We evaluated the role of platelet-derived SDF-1 in adhesion and differentiation of human CD34+ cells into endothelial progenitor cells. METHODS AND RESULTS: Adherent platelets express substantial amounts of SDF-1 and recruit CD34+ cells in vitro and in vivo. A monoclonal antibody to SDF-1 or to its counterreceptor, CXCR4, inhibits stem cell adhesion on adherent platelets under high arterial shear in vitro and after carotid ligation in mice, as determined by intravital fluorescence microscopy. Platelets that adhere to human arterial endothelial cells enhance the adhesion of CD34+ cells on endothelium under flow conditions, a process that is inhibited by anti-SDF-1. During intestinal ischemia/reperfusion in mice, anti-SDF-1 and anti-CXCR4, but not isotype control antibodies, abolish the recruitment of CD34+ cells in microcirculation. Moreover, platelet-derived SDF-1 binding to CXCR4 receptor promotes platelet-induced differentiation of CD34+ cells into endothelial progenitor cells, as verified by colony-forming assays in vitro. CONCLUSIONS: These findings imply that platelet-derived SDF-1 regulates adhesion of stem cells in vitro and in vivo and promotes differentiation of CD34+ cells to endothelial progenitor cells. Because tissue regeneration depends on recruitment of progenitor cells to peripheral vasculature and their subsequent differentiation, platelet-derived SDF-1 may contribute to vascular and myocardial regeneration.
