Han Z C, Zhang X J, Xi X D, Lu M, Jiang S, Jiang L Z, Wang X M, Gu G L, Caen J P
Shanghai Institute of Cell Biology, Academia Sinica.
Shi Yan Sheng Wu Xue Bao. 1995 Dec;28(4):415-26.
We have previously shown that platelet factor 4 (PF 4) is a potent inhibitor of megakaryocytopoiesis and that it may protect stem cells from 5-fluorouracil (5-FU) cytotoxicity. In the present work, the effects of human PF 4 on megakaryocyte (MK) growth from human CD34+ cord blood (CB) cells were studied in comparison with transforming growth factor beta 1 (TGF-beta 1). Development of MK from CD34+ cells in both plasma clot culture and liquid culture was significantly inhibited by PF 4 (5 micrograms/ml) and TGF beta 1 (1 ng/ml). Inhibition of cell growth by PF 4 was reversible judging from the fact that the CD34+ cells preincubated with PF 4 could regenerate colonies after washing and replating into the cultures. By contrast, TGF-beta 1 pretreated CD34+ cells gave rise to few colonies following replating. Moreover, incubation of CD34+ cells with PF 4 in liquid culture caused an increase in the number of both stem cell factor (SCF)-binding cells and CD34 antigen-bearing cells, and exhibited greater capacity to form MK colonies than control after the treatment of 5-FU. In vivo in mice, twice injections of PF 4 at 40 micrograms/kg with an interval of 6 h followed by one injection of 5-FU at 150 mg/kg resulted in a significant increase in the number of colony-forming cells with high proliferative potential (HPP-CFC) and colony-forming unit-megakaryocyte (CFU-MK) in bone marrow. In exponentially growing human erythroleukemia cells (HEL), the addition of PF 4 prolonged cell cycle progression and therefore resulted in an increased cell population in S phase, as determined by flow cytometric analysis. Different from PF 4, TGF-beta 1 blocked more cells in G 1 phase. These results demonstrate that PF 4 and TFG-beta 1 inhibit MK development from CD34+ CB cells by different mechanisms and suggest that PF 4, unlike TGF-beta 1, exerts its inhibitory effect on cell growth in a reversible and S phasespecific manner by which it protects stem cells and MK progenitor cells from 5-FU cytotoxicity.
我们之前已经表明，血小板因子4（PF4）是巨核细胞生成的强效抑制剂，并且它可能保护干细胞免受5-氟尿嘧啶（5-FU）的细胞毒性作用。在本研究中，将人PF4与转化生长因子β1（TGF-β1）相比较，研究了其对源自人CD34+脐血（CB）细胞的巨核细胞（MK）生长的影响。在血浆凝块培养和液体培养中，PF4（5微克/毫升）和TGF-β1（1纳克/毫升）均显著抑制了CD34+细胞向MK的发育。从用PF4预孵育的CD34+细胞在洗涤并重新接种到培养物中后能够再生集落这一事实判断，PF4对细胞生长的抑制作用是可逆的。相比之下，用TGF-β1预处理的CD34+细胞重新接种后形成的集落很少。此外，在液体培养中用PF4孵育CD34+细胞会导致干细胞因子（SCF）结合细胞和携带CD34抗原的细胞数量增加，并且在5-FU处理后，其形成MK集落的能力比对照更强。在小鼠体内，以40微克/千克的剂量两次注射PF4，间隔6小时，随后以150毫克/千克的剂量注射一次5-FU，导致骨髓中具有高增殖潜能的集落形成细胞（HPP-CFC）和巨核细胞集落形成单位（CFU-MK）的数量显著增加。在指数生长的人红白血病细胞（HEL）中，通过流式细胞术分析确定，添加PF4会延长细胞周期进程，因此导致S期细胞群体增加。与PF4不同，TGF-β1使更多细胞停滞在G1期。这些结果表明，PF4和TFG-β1通过不同机制抑制CD34+ CB细胞向MK的发育，并表明PF4与TGF-β1不同，它以可逆和S期特异性的方式对细胞生长发挥抑制作用，借此保护干细胞和MK祖细胞免受5-FU的细胞毒性作用。
