Dextran sulfate and stromal cell derived factor-1 enhance the expression of CXCR4 and improve the homing efficiency of hematopoletic stem cells in bone marrow

造血干细胞（hsc）在骨髓中的归巢是造血发育和骨髓再生的重要步骤。假设循环造血干细胞与骨髓内皮细胞相互作用，外渗，最终到达称为“壁龛”的专门骨髓微环境。虽然多种趋化因子、细胞因子和粘附分子可能参与其中，但HSC归巢的机制尚不完全清楚。最近的研究表明，趋化因子受体CXCR4及其配体基质衍生因子1 （SDF-1）的相互作用在HSC归巢的多个步骤中起着关键作用。此外，据报道，硫酸葡聚糖（DEX）增加了小鼠和非人灵长类动物血浆中SDF1和hsc的水平。在这项研究中，我们检测了SDF1和DEX预处理对骨髓移植过程中造血干细胞归巢效率的影响。将SDF-1 （100ng/kg）、DEX （100mg/kg）或PBS注射到供体GFP转基因小鼠体内4次，共4次。定量RP-PCR分析显示，SDF-1和DEX处理小鼠GFP+BM细胞中CXCR4的表达均升高。DEX预处理还增加了供体小鼠BM细胞中MMP9、e -选择素、VEGF、VLA5和LFA1等归巢相关分子的水平。流式细胞术分析显示，与对照组（35.2±1.6%）相比，SDF-1处理小鼠（45.1±10.1%）和DEX6处理小鼠（72.3±7.1%）BM细胞移植后7天的重构效率显著提高（n=3）。在外周血、胸腺和脾脏中也观察到DEX介导的早期重建增强。然而，在骨髓移植后30天，差异变得不显著。这些结果表明，SDF-1和DEX都能增强HSC的归巢，SDF-1可能直接上调HSC上CXCR4的表达，而DEX则具有诱导SDF-1及其他归巢所需分子的多种功能。DEX预处理可能为改善造血干细胞的归巢和植入提供了一种新的临床方法。少

Homing of hematopoietic stem cells (HSCs) in bone marrow (BM) is an important step of hematopoietic development and bone marrow repopulation. It is postulated that the circulating HSCs interact with BM endothelial cells, extravasate, and finally reach the specialized BM micrenvironment called "niches'. Although various kinds of chemokines, cytokines, and adhesion molecules supposed to be involved, the mechanism of HSC homing is not fully understood. Recent studies suggested that interaction of the chemokine receptor CXCR4 and its ligand, stromnal derived factor 1 (SDF-1) plays critical roles in multiple steps of HSC homing. In addition, it was reported that dextran sulfate (DEX) increased plasma levels of SDF1 and HSCs in mice and non-human primates. In this study, we examined the effects of preconditioning with SDF1 and DEX on the homing efficiency of HSCs during BM transplantation. SDF-1 (100ng/kg), DEX (100mg/kg), or PBS was injected into donor GFP transgenic mice 4 times for 4 cons … More ecutive days before harvesting BM cells. Quantitative RP-PCR analysis showed CXCR4 expression on GFP+BM cells was increased in both SDF-1 and DEX treated mice. DEX pretreatment also increased the levels of homing related molecules including MMP9, E-selectin, VEGF, VLA5, and LFA1 in BM cells harvested from the donor mice. Flow cytometry analysis demonstrated that the reconstitution efficiencies at 7 days after BM transplantation were significantly higher with BM cells from SDF-1 treated (45.1±10.1%) and DEX6 treated mice (72.3±7.1%) comnpored to control mice (35.2±1.6%)(n=3). The DEX mediated enhancement of reconstitution at an early stage was also observed in peripheral blood, thymus and spleen. However, the differences became not significant 30 days after BM transplantation. These results indicate that both SDF-1 and DEX are capable of enhancement of HSC homing SDF-1 may directly upregulate CXCR4 expression on HSCs, widle DEX appears to multiple functions including induction of SDF-1 and other molecules required for homing. Preconditioning with DEX may offer a novel clinical approach to improve homing and engraftment of HSCs. Less