De Bruyn C, Delforge A, Martiat P, Bron D
Experimental Hematology, Jules Bordet Institute, 1000 Brussels, Belgium.
Stem Cells Dev. 2005 Aug;14(4):415-24. doi: 10.1089/scd.2005.14.415.
Thrombocytopenia is a problematic and potentially fatal occurrence after transplantation of cord blood stem cells. This problem may be alleviated by infusion of megakaryocyte progenitor cells. Here, we compared the ability of hematopoietic progenitor cells obtained from cord blood and expanded in culture to that of mobilized peripheral blood cells. The CD34(+) cells were plated for 10 days in presence of thrombopoietin (TPO) alone and combined with stem cell factor (SCF), Flt3-ligand (FL), interleukin-3 (IL-3), IL-6, and IL-11. Cells were analyzed for the CD41 and CD42b expression and for their ploidy status. Ex vivo produced platelets were enumerated. We show that (1) TPO alone was able to induce differentiation of CD34(+) cells into CD41(+) cells, with limited total leucocyte expansion; (2) the addition of SCF to TPO decreased significantly CD41(+) cell percentage in CB, but not in MPB; and (3) in CB, the addition of FL, IL-6, and IL-11 to TPO increased the leukocyte expansion with differentiation and terminal maturation into MK lineage. In these conditions, high numbers of immature CD34(+)CD41(+) MK progenitor cells were produced. Our results thereby demonstrate a different sensitivity of CB and MPB cells to SCF, with limited CB MK differentiation. This different sensitivity to SCF (produced constitutively by BM stromal cells) could explain the longer delay of platelet recovery after CB transplant. Nevertheless, in CB, the combination of TPO with FL, IL-6, and IL-11 allows generation of a suitable number of immature MK progenitor cells expressing both CD34 and CD41 antigens, which are supposed to be responsible for the platelet recovery after transplantation.
血小板减少症是脐血干细胞移植后出现的一个问题，且具有潜在致命性。输注巨核细胞祖细胞或许可以缓解这一问题。在此，我们比较了取自脐血并经体外培养扩增的造血祖细胞与动员外周血细胞的能力。将CD34(+)细胞单独置于血小板生成素（TPO）存在的条件下培养10天，或与干细胞因子（SCF）、Flt3配体（FL）、白细胞介素-3（IL-3）、IL-6及IL-11共同培养。分析细胞的CD41和CD42b表达情况及其倍性状态。对体外产生的血小板进行计数。我们发现：（1）单独使用TPO能够诱导CD34(+)细胞分化为CD41(+)细胞，白细胞总体扩增有限；（2）在TPO中添加SCF可显著降低脐血中CD41(+)细胞百分比，但对动员外周血中的细胞无此作用；（3）在脐血中，向TPO添加FL、IL-6及IL-11可增加白细胞扩增，并使其分化并最终成熟为巨核细胞系。在这些条件下，可产生大量未成熟的CD34(+)CD41(+)巨核细胞祖细胞。我们的结果由此证明脐血细胞和动员外周血细胞对SCF的敏感性不同，脐血巨核细胞分化有限。对SCF（由骨髓基质细胞组成性产生）的这种不同敏感性可能解释了脐血移植后血小板恢复延迟时间更长的原因。然而，在脐血中，TPO与FL、IL-6及IL-11联合使用可产生适量表达CD34和CD41抗原的未成熟巨核细胞祖细胞，这些细胞被认为是移植后血小板恢复的原因。
