Canadian Blood Services, Centre for Innovation, Ottawa, Ontario, Canada.
Department of Cell Therapy and Applied Genomics, King Hussein Cancer Center, Amman, Jordan.
Stem Cells. 2019 Mar;37(3):345-356. doi: 10.1002/stem.2956. Epub 2018 Dec 24.
Ex vivo expansion of hematopoietic stem cell (HSCs) and progenitors may one day overcome the slow platelet engraftment kinetics associated with umbilical cord blood transplantation. Serum-free medium conditioned with osteoblasts (i.e., osteoblast-conditioned medium [OCM]) derived from mesenchymal stromal cells (MSC) was previously shown to increase cell growth and raise the levels of human platelets in mice transplanted with OCM-expanded progenitors. Herein, we characterized the cellular and molecular mechanisms responsible for these osteoblast-derived properties. Limiting dilution transplantation assays revealed that osteoblasts secrete soluble factors that synergize with exogenously added cytokines to promote the production of progenitors with short-term platelet engraftment activities, and to a lesser extent with long-term platelet engraftment activities. OCM also modulated the expression repertoire of cell-surface receptors implicated in the trafficking of HSC and progenitors to the bone marrow. Furthermore, OCM contains growth factors with prosurvival and proliferation activities that synergized with stem cell factor. Insulin-like growth factor (IGF)-2 was found to be present at higher levels in OCM than in control medium conditioned with MSC. Inhibition of the IGF-1 receptor, which conveys IGF-2' intracellular signaling, largely abolished the growth-promoting activity of OCM on immature CD34 subsets and progenitors in OCM cultures. Finally, IGF-1R effects appear to be mediated in part by the coactivator β-catenin. In summary, these results provide new insights into the paracrine regulatory activities of osteoblasts on HSC, and how these can be used to modulate the engraftment properties of human HSC and progenitors expanded in culture. Stem Cells 2019;37:345-356.
体外扩增造血干细胞（HSCs）和祖细胞也许有一天能够克服与脐带血移植相关的血小板植入动力学缓慢的问题。先前的研究表明，成骨细胞（即间充质基质细胞衍生的成骨细胞条件培养基[OCM]）的无血清培养基能够增加细胞生长并提高移植有 OCM 扩增祖细胞的小鼠中的人血小板水平。在此，我们对这些成骨细胞衍生特性的细胞和分子机制进行了特征描述。有限稀释移植分析显示，成骨细胞分泌的可溶性因子与外源性添加的细胞因子协同作用，促进具有短期血小板植入活性的祖细胞的产生，并在较小程度上促进具有长期血小板植入活性的祖细胞的产生。OCM 还调节了细胞表面受体的表达谱，这些受体涉及 HSC 和祖细胞向骨髓的迁移。此外，OCM 还包含具有生存和增殖活性的生长因子，这些因子与干细胞因子协同作用。发现 IGF-2 在 OCM 中的水平高于 MSC 条件培养基中的水平。IGF-1 受体抑制剂可阻断 IGF-2 的细胞内信号传导，该抑制剂可大大降低 OCM 对不成熟 CD34 亚群和 OCM 培养物中祖细胞的促生长活性。最后，IGF-1R 的作用似乎部分是通过共激活子β-catenin 介导的。总之，这些结果为成骨细胞对 HSC 的旁分泌调节活性提供了新的见解，以及如何利用这些活性来调节体外培养的人类 HSC 和祖细胞的植入特性。《干细胞》2019 年；37:345-356。
