| Abstract: | Endothelial progenitor cell (EPC) therapy represents a novel strategy for a variety of diseases. Interestingly, spleen acts an important reservoir during EPC trafficking. Therefore, we investigated the involvement of stromal cell-derived factor-1 (SDF-1)/CXCR4 in EPC settlement in the spleen. EPC were cultured and characterized as previous methods. Then, 1?×?106 EPC were labeled with DiI-LDL and intravenously infused into C57/BL6 mice. Immunohistochemical staining showed homing of transplanted EPC in the spleen 24?h later, indicating recruitment of transplanted EPC into the spleen. The distribution of EPC in different organs was evaluated by fluorescence-activated cell sorting of Sca-1/Flk-1+ cells, which demonstrated settlement of EPC in the spleen. Removal of the splenic niche by splenectomy augmented circulating EPC 12 and 24?h later, indicating an important role of spleen on modulation of EPC-circulating dynamics. Expressions of SDF-1 in the spleen and CXCR4 in EPC were revealed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR). A modified Boyden chamber assay showed that SDF-1 (10 or 100?ng/mL) induced EPC migration in vitro. Injection of the SDF-1 protein into the spleen increased the number of splenic EPC. In contrast, injection of a SDF-1 antibody or AMD3100 (SDF-1/CXCR4 axis antagonist) attenuated their settlement and did not induce EPC apoptosis. These results indicate that the SDF-1/CXCR4 axis is involved in recruitment of EPC to the spleen, and enhances our understanding of EPC-circulating kinetics. |
