Eto Tetsuya, Winkler Ingrid, Purton Louise E, Lévesque Jean-Pierre
Cell Adhesion and Trafficking Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
Exp Hematol. 2005 Feb;33(2):232-42. doi: 10.1016/j.exphem.2004.10.018.
The two endothelial selectins, P- and E-selectin, are critically important for adhesion and homing of hematopoietic progenitor cells (HPC) into the bone marrow. Little is known, however, about the roles of these two selectins in hematopoiesis. Here, we demonstrate that the most primitive HPC capable of long-term in vivo repopulation express P-selectin glycoprotein ligand-1/CD162 (PSGL-1), a receptor common to both P- and E-selectin. In addition, we demonstrate that P-selectin delays the differentiation of HPC whereas E-selectin enhances their differentiation along the monocyte/granulocyte pathway, describing different roles for these selectins in the regulation of hematopoiesis.
Murine bone marrow HPC were isolated according to their expression of c-kit and PSGL-1, transplanted into lethally irradiated congenic recipients, and chimerism analyzed 6 months posttransplant. Bone marrow lineage-negative (Lin(-)) Sca-1(+)c-kit(+) cells were then cultured on immobilized P- or E-selectin for 4 weeks in the presence of cytokines. Hematopoietic potential was assessed using in vitro phenotyping and colony-forming assays and in vivo spleen colony-forming unit (CFU-S) and long-term competitive repopulation assays.
Long-term competitive repopulating HSCs were Lin(-)c-kit(bright) and expressed intermediate levels of PSGL-1. Both P- and E-selectin slowed the proliferation of Lin(-)Sca-1(+)c-kit(+) cells during the first two weeks of liquid culture. After two weeks, however, cells cultured on immobilized P-selectin showed increased proliferation with increased production of both colony-forming cells (CFC) and CFU-S(12) compared to the other cultures. In contrast, E-selectin enhanced the differentiation of Lin(-)Sca-1(+)c-kit(+) cells into cells that expressed the granulocyte maturation marker, Gr-1, accompanied by loss of CFC potential from these cultured cells. Finally, the long-term repopulation potential of these cells was not maintained following culture on either selectin.
These results suggest that the two endothelial selectins, E-selectin and P-selectin, have very different effects on HPC. E-selectin accelerates the differentiation of maturing HPC towards granulocyte and monocyte lineages while maintaining the production of more immature CFU-S(12) in ex vivo liquid suspension culture. In marked contrast, P-selectin delays the differentiation of Lin(-)Sca-1(+)c-kit(+) cells, allowing enhanced ex vivo expansion of CFC and CFU-S(12) but not HSCs.
两种内皮细胞选择素，即P选择素和E选择素，对于造血祖细胞（HPC）黏附并归巢至骨髓至关重要。然而，关于这两种选择素在造血过程中的作用，人们了解甚少。在此，我们证明能够在体内长期重建的最原始HPC表达P选择素糖蛋白配体-1/CD162（PSGL-1），这是一种P选择素和E选择素共有的受体。此外，我们证明P选择素延缓HPC的分化，而E选择素增强其沿单核细胞/粒细胞途径的分化，揭示了这些选择素在造血调节中的不同作用。
根据c-kit和PSGL-1的表达分离小鼠骨髓HPC，将其移植到经致死性照射的同基因受体中，并在移植后6个月分析嵌合情况。然后将骨髓谱系阴性（Lin(-)）Sca-1(+)c-kit(+)细胞在细胞因子存在的情况下，在固定化的P选择素或E选择素上培养4周。使用体外表型分析和集落形成试验以及体内脾集落形成单位（CFU-S）和长期竞争性重建试验评估造血潜能。
长期竞争性重建造血干细胞为Lin(-)c-kit(明亮)，并表达中等水平的PSGL-1。在液体培养的前两周，P选择素和E选择素均减缓了Lin(-)Sca-1(+)c-kit(+)细胞的增殖。然而，两周后，与其他培养物相比，在固定化P选择素上培养的细胞显示增殖增加，集落形成细胞（CFC）和CFU-S(12)的产生均增加。相反，E选择素增强了Lin(-)Sca-1(+)c-kit(+)细胞向表达粒细胞成熟标志物Gr-1的细胞的分化，同时这些培养细胞的CFC潜能丧失。最后，在任一种选择素上培养后，这些细胞的长期重建潜能均未得到维持。
这些结果表明，两种内皮细胞选择素，即E选择素和P选择素，对HPC具有非常不同的作用。E选择素加速成熟HPC向粒细胞和单核细胞谱系的分化，同时在体外液体悬浮培养中维持更多未成熟CFU-S(12)的产生。与之形成鲜明对比的是，P选择素延缓Lin(-)Sca-1(+)c-kit(+)细胞的分化，使CFC和CFU-S(12)在体外得到增强扩增，但不能使造血干细胞扩增。
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