Gore S D, Amin S, Weng L J, Civin C I
Johns Hopkins Oncology Center, Baltimore, MD 21287-8963, USA.
Exp Hematol. 1995 May;23(5):413-21.
Steel factor (SF) acts synergistically with other hematopoietic growth factors to support the proliferation of progenitor cells in a variety of culture systems. To determine whether SF alone could directly stimulate proliferation of early hematopoietic progenitor cells, isolated CD34+ cells from adult bone marrow and umbilical cord blood were studied in a short-term suspension culture in serum-free medium. Numbers of CD34+ and proliferating cells were quantified by flow cytometry; proliferation was assessed by simultaneous measurement of expression of the nuclear antigen Ki67 and DNA content (propidium iodide [PI]). In the absence of growth factors, the numbers of CD34+ and cycling cells declined over 2 days. Cells cultured in the presence of SF alone maintained the number of CD34+ and cycling cells at levels equal to the starting population. Withdrawal of growth factors led to a dramatic decrease in the number of cells in G1. Compared to cells grown in the absence of growth factors, cells grown in the presence of SF had significantly higher numbers of CD34+ and cycling cells (mean fold increase = 1.3 and 2; p < 0.05 and 0.01, respectively). SF increased the numbers of cells in both G1 and later phases of the cell cycle. Addition of interleukin-3 (IL-3) to SF led to further significant increases in CD34+ and cycling cells. The effects of SF could not be attributed to inhibition of apoptosis. CD34+ cells isolated from peripheral blood (PB) from patients with chronic myelogenous leukemia (CML) displayed similar characteristics. As assessed by binding of phycoerythrin (PE)-labeled ligand and flow cytometry, c-kit was expressed on 65 +/- 6% of isolated CD34+ cells and was detected on HLA-DRlow, CD38low, and Thy1+ subsets, as well as on more mature progenitor cells. Thus, while the effects of SF are most marked in combination with other growth factors, SF appears to bind to and directly maintain the active cell-cycle characteristics of isolated CD34+ cells.
Steel因子（SF）与其他造血生长因子协同作用，在多种培养系统中支持祖细胞的增殖。为了确定单独的SF是否能直接刺激早期造血祖细胞的增殖，我们在无血清培养基的短期悬浮培养中研究了从成人骨髓和脐带血中分离出的CD34+细胞。通过流式细胞术对CD34+细胞和增殖细胞的数量进行定量；通过同时测量核抗原Ki67的表达和DNA含量（碘化丙啶[PI]）来评估增殖情况。在没有生长因子的情况下，CD34+细胞和循环细胞的数量在2天内下降。单独在SF存在下培养的细胞将CD34+细胞和循环细胞的数量维持在与起始群体相等的水平。生长因子的撤除导致G1期细胞数量急剧减少。与在没有生长因子的情况下生长的细胞相比，在SF存在下生长的细胞中CD34+细胞和循环细胞的数量显著更高（平均增加倍数分别为1.3和2；p分别<0.05和0.01）。SF增加了G1期和细胞周期后期的细胞数量。向SF中添加白细胞介素-3（IL-3）导致CD34+细胞和循环细胞进一步显著增加。SF的作用不能归因于对细胞凋亡的抑制。从慢性粒细胞白血病（CML）患者外周血（PB）中分离出的CD34+细胞表现出相似的特征。通过藻红蛋白（PE）标记的配体结合和流式细胞术评估，c-kit在65±6%的分离出的CD34+细胞上表达，并在HLA-DRlow、CD38low和Thy1+亚群以及更成熟的祖细胞上检测到。因此，虽然SF与其他生长因子联合使用时效果最为显著，但SF似乎能结合并直接维持分离出的CD34+细胞的活跃细胞周期特征。
