Hematopoietic Stem Cells Can Be CD34+ or CD34-

Until recently, it was thought that the most primitive HSC have a fixed phenotype within a hierarchical differentiation system, and that changes in engraftment and renewal potential occur in a stepwise fashion linked with differentiation. In this review, we summarize the data from several different species and different animal models of hematopoietic stem cell function. Taking into account all of the published data, it becomes clear that the hematopoietic stem cell compartment contains more than one phenotypically identifiable population capable of self-renewal and long term pluripotent engraftment. It is clear that some stem cells express CD34, and others do not. The exact phenotypic progression between these cells needs to be further defined, because different in vivo and ex vivo manipulations may shift the stem cells from one phenotype to another, and this can complicate interpretation of experimental transplant data.     

rhIL-17对小鼠造血前体细胞和人脐血CD34+干细胞分化发育的影响 *

目的:探讨重组人白细胞介素-17(Interleukin-17,IL-17)对小鼠骨髓造血前体细胞和人脐血来源的CD34~ 干细胞生长发育的影响.方法:采用常规方法采集小鼠造血前体细胞;采用Mini-MACS分离技术,从正常人脐血分离人CD34~ 干细胞.体外加入IL-17和/或GM-CSF、IL-4培养分离的前体细胞,应用流式细胞仪检测其表型,采用ELISA法检测了其分泌的IL-12水平,通过[~3H]-TdR掺入法测定其刺激同种异体T淋巴细胞增殖的能力.结果:IL-17促进了小鼠骨髓来源的未成熟DC表达Ia,B7-2等免疫分子,促使其分泌较高水平的IL-12,该细胞也能刺激同种异体T细胞有效增殖,表现出了成熟DC的特征.IL-17单独培养9d促使人脐血CD34~ 干细胞扩增了2倍,部分细胞高表达CD1a及B7-2,低表达HLA-DR,未检测到CD83的表达.该细胞能促使同种异体T细胞增殖,但作用较弱;而rhIL-17与GM-CSF联合培养后扩增了14倍,培养细胞中CD1a、B7-2阳性细胞的比例明显升高,且此细胞刺激同种异体T细胞增殖的能力较强.结论:IL-17体外可促进小鼠骨髓造血前体细胞来源的DC成熟;与GM-CSF联合培养既能促进CD34~ 干细胞增殖,又能使之获得DC特征,初步提示IL-17与GM-CSF联合作用可促进CD34~ 干细胞向DC分化.     

Multipotent and Committed CD34+ Cells in Bone Marrow Transplantation

In order to study the role of CD34⁺ cells in hematological recovery following bone marrow transplantation (BMT), bone marrow cells stained with HPCA-1 (CD34) and MY-9 (CD33) monoclonal antibodies were analyzed by using a fluorescence-activated cell sorter on or about days 14 and 28, as well as at later times, following BMT in 6 recipients. Single cell cultures of CD34⁺ cells were also performed to evaluate their in vitro hematopoietic function. CD34⁺ cells were detectable in bone marrow cells on day 14. More than 80% of CD34⁺ cells co-expressed the CD33 antigen, and macrophage (Mac) colony-forming cells predominated among total colony-forming cells of CD34⁺ cells. In normal bone marrow cells, CD34⁺, CD33⁺ cells amounted to about 40% of CD34⁺ cells, and the incidences of erythroid bursts, granulocyte/macrophage (GM) colonies, and Mac colonies were similar to each other. After more than 10 weeks, CD34⁺, CD33⁻ cells gradually recovered, as erythroid burst colony-forming cells increased following GM colony-forming cells. This phenomenon was well-correlated with the time course of peripheral blood cell recovery. CD34⁺, CD33⁺ cells as committed progenitors and CD34⁺, CD33⁻ cells as multipotent stem cells have distinctive biological behaviors in BMT.     

血管内皮生长因子促进小鼠胚胎干细胞生成CD34+细胞的研究

目的：研究血管内皮生长因子(vascular endothelial growth factor, VEGF)体外促进小鼠胚胎干细胞系ESD3生成CD34+细胞的能力。方法将ESD3形成拟胚体，将拟胚体细胞转入含不同浓度的VEGF和VEGF+干细胞因子（stem cell factor, SCF)的培养基中。实验分6组，分别为VEGF 5 μg/L组、VEGF 10 μg/L 组、VEGF 20 μg/L组、VEGF 5 μg/L＋SCF组、VEGF 10 μg/L＋SCF组、VEGF 20 μg/L＋SCF组，同时设不加因子的自发分化对照组。RTPCR检测CD34 mRNA的表达，流式细胞仪检测CD34+细胞的比例，甲基纤维素半固体培养法检测生成造血集落的能力。结果：经过1周的诱导培养，实验组生成的细胞可以表达CD34 mRNA，CD34＋细胞的比例也升高，并可形成造血祖细胞的集落。从CD34 mRNA的表达水平、诱导生成CD34＋细胞的比例和生成的集落数量看，VEGF 20 μg/L＋SCF组和VEGF 10 μg/L＋SCF组的诱导效率最高。结论：VEGF能够促进ESC生成CD34＋细胞，尤以与SCF合用时，其诱导效率更高。     

Ultrastructural Features of CD34+ Hematopoietic Progenitor Cells from Bone Marrow, Peripheral Blood and Umbilical Cord Blood

Hematopoietic progenitor cells from different sources have been widely characterized, but their ultrastructural morphology has never been described in detail. In this study, imunomag-netically separated CD34⁺ cells from normal bone marrow (BM), mobilized peripheral blood (PBSC) and human umbilical cord blood (CB) were studied by transmission electron microscopy (TEM) using a cytochemical method which reveals endogenous myelo-peroxidase (MPO) activity. This technique is particularly suited for detecting early signs of the myeloid commitment. The CD34⁺ cells from PBSC were morphologically very homogeneous and 94.7 ± 4.5% of these cells were MPO^-: these ultrastructural features are generally considered typical of immature cells. The CD34⁺ BM cells were instead more heterogeneous, with 24.6 ± 7.4% showing intense MPO activity. The ultrastructural characteristics of CB cells fell between those observed in PBSC and BM, but there was a high percentage of morphologically immature cells with no evidence of MPO activity (about 83%). The number of apoptotic cells within samples from different sources was also examined both by TEM and flow cytometry. The percentage of apoptotic cells was 0.7% in PBSC, 2.3% in BM, 2.9% in CB from vaginal delivery and 11.6% in CB from cesarean section. These observations confirm the relative phenotypic immaturity of CB in comparison with BM cells; they also suggest that CB collected after cesarean section may be associated with reduced stem cells viability.     

Reduced Mobilisation of Hematopoietic Stem Cells After Hepatic Resection for Malignant Liver Disease

Recent studies have demonstrated that hematopoietic stem cells (HSCs) can mobilize following liver resection, thus contributing to the repair of hepatic damage. Aim of this study has been to determine whether the nature of the hepatic lesion (benign vs. malignant disease) can give rise to a different degree of mobilisation of HSCs. Two groups of patients were selected: the first included seven patients undergoing hepatic resection (five major and two minor) for a benign liver disease (focal nodular hyperplasia, hemangioma cavernosa, angioma, biliary adenofibroma) and the second included seven patients undergoing hepatic resection (five major and two minor) for a malignant (either primary or secondary) liver disease. White blood cell count and CD34+ (percentage and total number) at time T₀ (basal value before surgery) and at time T₁ (value on the sixth–eighth day after surgery) have been evaluated by standard methods. In the group undergoing hepatic resection for a benign liver disease, a significant increase of CD34+ cells, both in percentage (0.082 ± 0.043 vs. 0.048 ± 0,026, p = 0.041) and in absolute number (8.14 ± 5.95 vs. 3.26 ± 2.63, p = 0.018) have been documented, as opposed to the group of patients affected with a malignant liver disease, where no significant variation has been observed (CD34+ %: 0.044 ± 0.033 vs. 0.041 ± 0.031, p: n.s.; CD34+ total number: 3.52 ± 2.56 vs. 2.27 ± 2.01, p = n.s.) These results show a different bone marrow response to the surgical liver resection depending on the nature of the lesion, thus emphasizing a reduced mobilisation of HSCs in the malignant diseases. Since it has been documented that the type of the hepatic lesion can induce a different regenerative response, it has to be explained how the neoplastic lesions can negatively influence the mobilization of HSCs. It can be hypothesized that a variety of humoral factors, including stromal cell-derived factor, matrix metalloproteinases, hepatocyte growth factor and interleukin-8 can influence the process of mobilization of HSCs after liver resection surgery. These substances are also involved in the mechanisms of development and metastasising of many tumours. It is probably in this context that a reason may be found for the different mobilisation of hematopoietic stem cells, depending on the nature of the hepatic lesion treated, that was encountered in this study.     

纯化的自体CD34~+细胞移植治疗恶性血液病临床对照观察

 目的　分析CD34+ 纯化自体造血干细胞移植治疗恶性血液病的临床疗效。方法　 11例病人进行了CD34+ 纯化自体造血干细胞移植 ,8例患者进行了未分选的自体造血干细胞移植 ,动员方案为CTX+Vp 16联合G CSF。CD34+ 细胞分选采用CliniMACS系统。结果　分选后CD34+ 细胞纯度达到(88.99± 6 .88) % ,回收率达到 (6 9.0 6± 17.0 7) %。 11例分选患者感染率为 (5 / 11例 ) ,复发率为 (1/ 11例 ) ,死亡率为 (3/ 11例 )。外周血中性粒细胞 >0 .5× 10 9/L时间为 (11± 1)天 ,血小板 >2 0× 10 9/L为(13± 3)天 ,8例未行CD34+ 分选患者的感染率 (4/ 8例 ) ,复发率为 (3/ 8例 ) ,死亡率为 (5 / 8例 )。外周血中性粒细胞 >0 .5× 10 9/L时间 (11± 1)天和血小板 >2 0× 10 9/L(14± 4 )天。结论　利用CliniMACs系统体外进行外周血CD34+ 细胞的富集与纯化纯度、回收率均满意 ,自体移植后造血功能重建顺利 ;与对照相比造血重建时间、感染率...     

Short-Term Effects of Early-Acting and Multilineage HematoPoietic Growth Factors on the Repair and Proliferation of Irradiated Pure Cord Blood (CB) CD34 Hematopoietic Progenitor Cells

Purpose: Hematopoietic growth factor(s) (GF) may exert positive effects in vitro or in vivo on the survival of hematopoietic stem and progenitor cells after accidental or therapeutic total body irradiation.

Methods and Materials: We studied the clonogenic survival and DNA repair of irradiated (0.36, 0.73, and 1.46 Gy) CD34⁺ cord blood (CB) cells after short-term incubation (24 h) with GFs. CD34⁺ cells were stimulated with basic fibroblast growth factor (bFGF), stem cell factor/c-kit ligand (SCF), interleukin-3 (IL-3), IL-6, leukemia inhibitory factor (LIF), and granulocyte-monocyte colony stimulating factor (GM-CSF) alone or in combination in short-term serum-free liquid suspension cultures (LSC) immediately after irradiation and then assayed for clonogenic progenitors. DNA repair was evaluated by analysis of DNA strand breaks using the comet assay. Survival of CFU-GM, BFU-E, and CFU-Mix was determined and dose–response curves were fitted to the data.

Results: The radiobiological parameters (D₀ and n) showed significant GF(s) effects. Combination of IL-3 with IL-6, SCF or GM-CSF resulted in best survival for CFU-GM BFU-E and CFU-Mix, respectively. Combinations of three or more GFs did not increase the survival of clonogenic CD34⁺ cells compared to optimal two-factor combinations. The D₀ values for CFU-GM, BFU-E, and CFU-Mix ranged between 0.56–1.15, 0.41–2.24, and 0.56–1.29 Gy, respectively. As for controls, the curves remained strictly exponential, i.e., all survival curves were strictly exponential without any shoulder (extrapolation numbers n = 1 for all tested GF(s). DNA repair capacity of CD34⁺ cells determined by comet assay, was measured before, immediately after irradiation, as well as 30 and 120 min after irradiation at 1 Gy. Notably, after irradiation the 2-h repair of cytokine-stimulated and unstimulated CD34⁺ cells was similar.

Conclusion: Our data indicate that increased survival of irradiated CB CD34⁺ cells after short-term GF treatment is mediated through proliferative GF effects on the surviving fraction but not through improved DNA repair capacity.     

Caspase-3在脐血CD34+造血干/祖细胞中的表达及其意义

目的 为了探讨脐血CD34~+干/祖细胞在不同细胞因子支持下体外扩增过程中Caspase-3表达及意义,我们采用了RT-PCR、Western blot和流式细胞仪技术测定了脐血CD34~+细胞在体外扩增过程中的生物学特性及Caspase-3的表达。检测结果显示,Caspase-3mRNA在新鲜分离的脐血CD34~+细胞中低水平表达,在细胞因子支持下体外培养3天,扩增的CD34~+细胞中Caspase-3mRNA和蛋白质水平表达上调,但在这两种细胞中仅能检测到分子量为32KDa的非活性酶原形式的Caspase-3;随着体外培养时间的延长,在IL-3,IL-6和GM-CSF组合条件下,Caspase-3被激活,可检测到分子量力20KDa的裂解片段。本研究表明,虽然造血干细胞的凋亡是个复杂的过程,但在脐血CD34~+干/祖细胞体外扩增过程中,Caspase-3参与了凋亡事件并发挥着重要的作用。     

自体外周血造血干细胞移植过程中淋巴细胞亚群和CD34+细胞变化的动态研究

目的动态观察动员、采集过程中外周血及造血干细胞中的淋巴细胞亚群和造血干细胞含量变化,及时指导临床选择最佳采集时机。方法 采用流式细胞术(FCM)测定大剂量化疗(HDC)联合重组人粒细胞集落刺激因子(rhG-CSF)对47例恶性实体瘤患者自体外周血造血干细胞移植(APBSCT)过程中,外周血和外周血造血干细胞(PBPC)中的淋巴细胞亚群CD3、CD4、CD8、NK、CD19和造血干细胞CD34+及其亚群CD34+CD38-、CD34+ Thy1+、AC133+细胞含量的变化,同时用体外集落培养的方法评价干细胞克隆形成能力。结果 动员后外周血淋巴细胞亚群CD3、CD4、CD8、NK和CD19细胞含量均低于动员前,其中CD3、CD8含量明显低于基础状态(P=0.007,P=0.016),而动员后外周血中的CD34及其亚群含量均明显高于动员前(P<0.05)。动员后中位时间第16天(15～17 d)外周血中的CD34含量达到最高峰,且第1次采集物中的造血干细胞含量最高。PBPC中除CD4、CD4/CD8明显低于外周血外(P<0.000 5),其他淋巴细胞亚群含量与外周血比较无明显改变。外周血单个核细胞中CD34+细胞含量与PBPC中CD34+细胞、CD34+CD38-及粒/单系集落形成单位(CFU-GM)、红系爆式集落形成单位(BFU—E)均存在显著相关性(P<0.05),而与采集的单个核细胞(MNC)总数、CD34+Thy1+、AC133+细胞含量间无相关关     

Homing-Associated Cell Adhesion Molecule (H-CAM/CD44) on Human CD34+ Hematopoietic Progenitor Cells

Human CD34⁺ hematopoietic progenitor cells (HPCs) express CD44 and can directly adhere to hyaluronate (HA) via CD44. Furthermore, CD44 may also be involved in the regulation of CD34⁺ HPC proliferation and development. The expression of CD44 molecules on CD34⁺ hematopoietic progenitor cells is significantly lower on bone marrow (BM) CD34⁺ cells compared with circulating CD34⁺ cells in cord blood and peripheral blood. Myeloid and erythroid progenitor cells are found predominantly in CD34⁺CD44^- cell fractions. More interestingly, CD34⁺CD44⁺ cells expressing B-lymphocyte-associated CD10 and CD19 would represent unique B-lymphocyte committed precursors in the BM, which might undergo apoptotic cell death in the early steps of B-cell differentiation.     

Comparison of Two Methods for Concentrating CD34 + Cells from Patients with Acute Non-Lymphocytic Leukemia

The aim of the present study was to compare two different methods for obtaining CD34 + cells from the peripheral blood or the bone marrow of patients with acute non-lymphocytic leukemia (ANLL). Twenty-two samples, obtained from 19 patients, were density cut (Ficoll-Hypaque 1.077) and, after incubation with My10 antibody, separated by panning or by immunomagnetic beads. Immunomagnetic beads provided a significantly better separation than panning, either in terms of concentration of CD34+ cells (85.5 ± 11.6% vs. 55.7±25.0%, p = 0.003) or in terms of depletion of CD34+ cells (3.9 ± 8.0% vs. 30.9 ± 26.3%, p = 0.008). This was consistent with the virtually complete depletion of colony forming cells (CFC) in the CD34 negative fraction and the recovery of virtually all the CFC in the positive fraction in the samples separated by immunomagnetic beads. In conclusion, separation by immunomagnetic beads can allow collection of nearly pure CD34+ and CD34—cell populations from patients with ANLL, thereby facilitating the study of the biological characteristics of these cell populations. Moreover the method is less time consuming than panning and is not toxic to the CFC.     

CD133作为胶质瘤干细胞标志物应用的局限性

胶质瘤是神经外科最常见的恶性肿瘤,临床尚缺乏有效的治疗手段。肿瘤干细胞被认为是胶质瘤发生、发展的源头而受到越来越多的关注。干细胞标志物CD133广泛表达于人体多种肿瘤中,同时,它也是研究得最多且应用最广的胶质瘤干细胞表面标志物。然而,利用CD133进行胶质瘤干细胞的鉴定和筛选正逐渐受到质疑。本文将对近年来人们发现的CD133作为胶质瘤干细胞标志物应用的局限性进行综述。     

盐酸吉西他滨对非小细胞肺癌患者骨髓CD34+造血细胞的毒性研究

目的 探讨非小细胞肺癌患者骨髓CD34+前体造血细胞在细胞毒药物盐酸吉西他滨诱导下,发生细胞凋亡情况及DNA损伤修复信号通路上相关基因表达的变化.方法 采用免疫磁珠法分选出80例非小细胞肺癌患者骨髓单个核细胞中的CD34+细胞,并应用流式细胞术检测其纯度.用盐酸吉西他滨(终末浓度为10μg/ml)诱导CD34+细胞凋亡,检测诱导不同时间点的细胞凋亡率的差异.提取细胞RNA,利用基因芯片技术,将药物诱导前后的CD34+细胞在DNA损伤修复信号通路的相关基因表达情况进行检测,并分析比较.结果 80份骨髓样本CD34阳性率为(6.06±1.61)%;TNM分期不同的患者样本间CD34的表达无统计学差异,P>0.05.免疫磁珠法分选后,流式细胞术检测CD34+细胞的纯度为(88.63±7.29)%;CD34+细胞在经过盐酸吉西他滨诱导0 h、4 h、8 h、12 h后,凋亡率分别为(5±1.37)%、(18±4.76)%、(39±8.15)%、(56±9.64)%,各时间点细胞的凋亡率之间有统计学差异,P<0.05.基因芯片结果显示,骨髓CD34+细胞在盐酸吉西他滨诱导凋亡0 h与诱导12 h后相比,表达差异2倍以上的基因有13种,其中9种基因表达是升高的,4种基因表达降低.结论 盐酸吉西他滨可以诱导非小细胞肺癌患者骨髓前体CD34+细胞发生凋亡,随着药物作用时间延长,细胞凋亡率上升;DNA损伤修复系统中,部分基因表达水平出现变化.     

Evaluation of residual CD34+Ph+ progenitor cells in chronic myeloid leukemia patients who have complete cytogenetic response during first‐line nilotinib therapy

BACKGROUND:

Compared with imatinib, nilotinib is a potent breakpoint cluster region/v‐abl Abelson murine leukemia viral oncogene (bcr‐abl) kinase inhibitor, and it induces higher rate and rapid complete cytogenetic response (CCyR), yet no clinical data are available regarding its efficacy against chronic myeloid leukemia (CML) stem cells. Earlier studies demonstrated that clusters of differentiation 34–positive, Philadelphia chromosome–positive (CD34⁺Ph⁺) cells are detectable in about 45% of patients with CML, despite being on long‐term imatinib therapy and having achieved sustained CCyR.

METHODS:

CD34⁺ cells from bone marrow of de novo CML patients in the chronic phase (n = 24) treated with nilotinib (median duration of therapy, 22 months) were isolated and scored for BCR‐ABL by fluorescent in situ hybridization (FISH) analysis. Similar analysis was also performed in 5 de novo CML chronic phase patients who achieved CCyR within 3 months of nilotinib therapy.

RESULTS:

FISH evaluation of a median of 100 CD34⁺ nuclei per patient revealed that only 1 of 20 (5%) evaluable patients showed residual Ph⁺ progenitor cells. In this patient, just 1 of 140 (0.7%) CD34⁺ interphase nuclei was found to be positive for BCR‐ABL. Surprisingly, no CD34⁺Ph⁺ cells were found even in those 5 patients evaluated after 3 months of nilotinib treatment.

CONCLUSIONS:

This study assessed for the first time the persistence of CD34⁺Ph⁺ cells during nilotinib first‐line treatment. Preliminary results showed that in patients in CCyR, even after short‐term nilotinib therapy, residual leukemic progenitors are very rarely detected compared with imatinib‐treated CCyR patients. It is yet to be determined if these findings will have an impact in the path to a cure of CML with tyrosine kinase inhibitors. Cancer 2012. © 2012 American Cancer Society.     

脐血CD34~+细胞扩增中系特异性分化抗原的变化

目的：探讨CB CD34^ 细胞扩增的最佳HGF组合及移植时机。方法：CB CD34^ 细胞培养于无血清培养液中,分别加入下列HGF,A组：对照组（无HGF）;B组：SCF,IL－3,IL－6;C组：SCF,IL－3,IL－6,G－CSF,Epo;D组：SCF,IL－3,IL－6,TPO,Flt3-L;E组：SCF,IL－3,IL－6,TPO,Flt3-L,G-CSF,Epo。培养22d,对不同培养时间的细胞进行NC数量及系特异性CD动态观察。结果：同对照组相比,扩增组NC和CD34^ 细胞均有不同程度的扩增。NC和CD34^ 细胞扩增高峰分别在第10天和第6天。E组的扩增效果最佳。CD检测显示,各组CD34^ 及CD34^ CD^38-细胞的比例逐渐减少,但B,D2组的CD34^ CD38^-细胞的比例在第6天有一过性回升,CD154^ ,CD13^ ,CD61^ 及Gly-A^ 细胞的比例则逐渐升高,D组CD34^ 及CD34^ ,CD38^-细胞的比例明显地高于E组（P＜0．01）,CD3^ 和CD19^ 细胞的比例在扩增中呈下降趋势,结论：HSPC分化程度与HGF组合及培养时间有关。就细胞总数而言,E组HGF组合最佳,但就HSPC含量来说,以D组为优,第1周扩增产物中HSPC含量较高,移植时间以扩增的第6－10天为宜。     

High levels of circulating CD34+ cells at autologous stem cell collection are associated with favourable prognosis in multiple myeloma

Background:

High-dose chemotherapy with autologous stem cell transplantation is a cornerstone in the first-line treatment of multiple myeloma patients. However, only few factors have been identified affecting the outcome in such patients. We hypothesised that varying levels of mobilised CD34+ cells confer prognostic information in myeloma patients undergoing high-dose chemotherapy.

Methods:

We determined circulating CD34+ cells at the day of peripheral stem cell collection in 158 consecutive myeloma patients between January 2001 and August 2010. Patients were stratified into two groups (super vs normal mobilisers) with a cutoff of 100 000 peripheral CD34+ cells per ml.

Results:

We found that patients with more than 100 000 peripheral CD34+ cells per ml had a better overall survival (P=0.005) and a prolonged time to progression (P=0.0398) than patients with CD34+ cell counts below 100 000 CD34+ cells per ml. High levels of CD34+ cells were an independent marker for better overall survival and time to progression in a multivariate analysis that included disease stage, response at transplant, light-chain subtype, age, sex, and height.

Conclusion:

Our results suggest that high levels of mobilised peripheral CD34+ cells are associated with favourable outcome in myeloma patients undergoing autologous transplantation.     

脐带血CD+34细胞体外扩增优化条件的研究

 目的　分析比较不同细胞饲养层、不同刺激因子、脐血CD+34 细胞的纯度和含量等因素对脐血CD+34 细胞在体外扩增的影响,以筛选其体外扩增的优化方案。方法　采用正交实验,通过MTT法、细胞计数法及流式细胞分析技术测定脐血CD+34 细胞的增生情况;并采用以上方法及半固体培养体系对该细胞优化条件下的增生情况及集落形成能力进行检测。结果　优化条件下脐血CD+34细胞增生10倍,明显高于对照组的2.8倍（P＜0.01）,集落形成（CFU-C 36.67±6.11）也较对照组强（CFU-C 16.33±1.53）（P＜0.01）。结论　该培养系统能促进脐血CD+34 细胞体外扩增并能较好保持脐血CD+34 细胞的干细胞性质。