Megakaryothrombopoiesis during ex vivo expansion of human cord blood CD34+ cells using thrombopoietin

Thrombopoietin (TPO) is one of the most promising stimulants for ex vivo expansion of haematopoietic stem cells. Previously, we have found that TPO induces a characteristic pattern of apoptosis during ex vivo expansion of human cord blood (CB) CD34+ cells and that the TPO-induced apoptotic cells belong to megakaryocyte (MK) lineage. In this study, we have examined the maturation of MK and platelet production in association with the TPO-induced apoptosis. CD34+ cells, purified from human CB, were expanded in serum-free conditions stimulated with TPO. Apoptosis was confirmed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) assay and electron microscopy (EM). Simultaneous measurement of DNA content and immunophenotyping revealed that the cells with higher DNA content (>8 N) constituted less than 5% of the CD41+ fractions until day 14, implying premature apoptosis of MKs before full polyploidization. Nevertheless, EM observation showed not only platelet territories but also newly produced platelets in which granules and microfilaments could be identified. Furthermore, flow cytometry demonstrated that the platelet fraction expressed P-selectin and an activation motif on GPIIb/IIIa recognized by monoclonal antibody PAC-1 upon stimulation with adenosine diphosphate (ADP). In addition, periodic acid-Schiff (PAS)-positive materials and nonspecific esterase activities could be demonstrated. Therefore, it is suggested that platelet production and the accompanying processes, rather than apoptosis only, be hastened during the ex vivo expansion of CB CD34+ cells when using TPO.     

Cytokine-induced expansion of human CD34+ stem/progenitor and CD34+CD41+ early megakaryocytic marrow cells cultured on normal osteoblasts

Thrombocytopenia remains a significant cause of morbidity in cancer patients undergoing allogeneic bone marrow transplantation (BMT), which consumes millions each year for frequent platelet transfusions. Using a novel culture system containing appropriate cytokine(s) on a layer of normal human osteoblasts, we investigated the expansion of early megakaryocytic progenitor cells while maintaining the number of CD34+ stem/progenitor marrow cells in an attempt to provide an effective solution for the problem of post-transplant thrombocytopenia. After seven days of culture, normal human osteoblasts alone without cytokines significantly increased the number of CD34+ and CD34+CD41+ marrow cells. Among the various cytokine combinations tested, both stem cell factor (SCF), interleukin 3 (IL-3)+IL-11 and SCF+IL-3+IL-11+thrombopoietin (TPO) emerged as the most effective in expanding early CD34+CD41+ megakaryocytic cells. Early CD34+CD41+ megakaryocytic cells have increased by 3.1- and 4.7-fold compared with day 7 control cultures, and by 62- and 94-fold, respectively, compared with day 0 input, respectively. Also, late CD41+ megakaryocytic cells have increased by 15.4- and 27.5-fold compared with day 7 control cultures in the presence of the same two combinations. In addition, the same cytokine combinations achieved 17.6- and 13.3-fold increases in the number of CD34+ marrow cells after the same seven days of culture on a layer of human osteoblasts. The combination (SCF+IL-3+IL-11+TPO) achieved the highest expansion of CD34+CD41+ early megakaryocytic cells from human marrow CD34+ cells reported so far in the literature. Recently, transplantation of SCF+IL-1+IL-3+TPO ex vivo expanded megakaryocytic progenitor cells as a supplement has been shown to accelerate platelet recovery by three to five days in mice. Therefore, the clinical use of the combination (SCF+IL-3+IL-11+TPO) for ex vivo expansion of CD34+ and megakaryocytic progenitor cells from a portion of the donor's marrow harvest is warranted in allogeneic BMT. Such a protocol would accelerate platelet recovery and shorten the period of hospitalization after allogeneic BMT. The present study has confirmed the role of human osteoblasts in supporting the proliferation and maintenance of human CD34+ stem/progenitor marrow cells. Given the facilitating role of osteoblasts shown previously in several allogeneic BMT studies in mice, it is possible to envisage a future role for donor osteoblasts in clinical BMT. Transplantation of the cultured donor osteoblasts together with the ex vivo expanded CD34+ marrow cells as a supplement might not only accelerate platelet recovery but also prevent acute graft-versus-host disease in allogeneic BMT. The present novel culture system should have useful clinical application in allogeneic BMT.     

Effect of tresperimus on ex vivo expansion of CD34+CD38(-)-enriched cord blood cells

Tresperimus, an analogue of 15-deoxyspergualine (15-DSG), has been found, in rodents, to induce a potent state of tolerance after organ and bone marrow allografts. In a previous study, we have reported that tresperimus at the optimal concentration of 0.5 microgram/ml supports the clonogenic potential of human cord blood CD34+ cells. Dose dependent inhibition of clonogenesis was also observed with complete reversibility following drug withdrawal. In this study, we tested the effect of 0.5 microgram tresperimus/ml on ex vivo expansion of primitive human cord blood CD34+CD38- cells. Our findings revealed that the total number of expanded cells was decreased in the presence of tresperimus. However, the multipotential and erythroid colonies were significantly increased in the presence of tresperimus compared with control cultures done without the test drug. Progenitor cell morphology was comparable in both test and control cultures. The telomerase activity was consistently lower in tresperimus-treated hematopoietic progenitors than in control cultures. These results suggest that tresperimus preserves primitive CD34+CD38- cells in a state of high potentiality while limiting the total number of their differentiated progeny. Bearing in mind that the test drug supports the clonogenic potential of CD34+ cells, the overall findings emphasize the importance of assessing the effect of tresperimus on in vivo long-term hematopoiesis which could predict the potential clinical use of tresperimus in the prevention of graft-versus-host disease in recipients of allogeneic bone marrow.     

Surface-immobilization of adhesion peptides on substrate for ex vivo expansion of cryopreserved umbilical cord blood CD34+ cells

The interaction between integrins and extracellular matrix proteins play an important role in the regulation of hematopoiesis. Human hematopoietic progenitor cells express very late antigen-4 (VLA-4) and VLA-5, which mediate their interaction with fibronectin by recognizing the connecting segment-1 (CS-1 and RGD motifs, respectively. In this study, we investigated the ex vivo expansion of human umbilical cord blood (UCB) CD34+ cells on synthetic substrates surface-immobilized with peptides containing the CS-1 binding motif (EILDVPST) and the RGD motif (GRGDSPC). These peptides were covalently conjugated to poly(ethylene terephthalate) (PET) film at a surface density of 2.0-2.3 nmol/cm2. UCB CD34+ cells were cultured for 10 days in serum-free medium supplemented with recombinant human thrombopoietin, stem cell factor, flt3-ligand and interleukin 3. The highest cell expansion fold was observed on the CS-1 peptide-modified surface, where total nucleated cells, total colony forming unit, and long-term culture initiating cells were expanded by 589.6+/-58.6 (mean+/-s.d.), 76.5+/-8.8, and 3.2+/-0.9-fold, respectively, compared to unexpanded cells. All substrates surface-immobilized with peptides, including the control peptides, were more efficient in supporting the expansion of CD34+, CFU-GEMM and LTC-ICs than tissue culture polystyrene surface. Nevertheless, after 10-days of ex vivo expansion from 600 CD34+ cells, only cells cultured on CS-1-immobilized surface yielded positive engraftment, even though the frequency was low. PET surface immobilized with RGD peptide was less efficient than that with CS-1 peptide. Our results suggest that covalently immobilized adhesion peptides can significantly influence the proliferation characteristics of cultured UCB CD34+ cells.     

使用抗氧化剂调控胞内的ROS对脐血CD34^＋细胞体外扩增特性的影响

目的:使用抗氧化剂调控胞内活性氧物质(ROS)水平, 考察其对脐血CD34 细胞体外扩增特性的影响.方法:在体外培养过程中, 分别采用超氧化物歧化酶(SOD)、过氧化氢酶(CAT)或N-乙酰半胱氨酸(NAC)3种抗氧化剂降低脐血CD34 细胞内的ROS水平, 研究了CD34 细胞在抗氧化剂清除ROS后的体外扩增特性.结果:体外培养时细胞因子的应用会使细胞内的ROS水平显著上升.3种抗氧化剂均能有效地清除细胞内ROS, 且清除程度随使用剂量的改变而变化.在培养体系中添加2 000 U/mL SOD、 200 U/mL CAT 或2 mmol/L NAC, 扩增后培养物中CD34 细胞及CD34 CD38-细胞的比例、 集落生成细胞的密度均有明显提高, 但对CD34 细胞扩增倍数影响不大; 而加入8 000 U/mL SOD、 1 000 U/mL CAT 或5 mmol/L NAC, 抑制CD34 细胞的扩增能力.结论:采用细胞因子体外扩增脐血CD34 细胞时, 使用低剂量的抗氧化剂适度清除细胞内的ROS, 明显提高培养物中造血干/祖细胞的含量, 同时并不影响扩增后CD34 细胞的再扩增能力.     

转FL、GM-CSF基因的人骨髓基质细胞促进脐血CD34+细胞体外扩增

研究转FL、GM-CSF基因的基质细胞对脐血CD34+细胞的扩增效应.将转FL、GM-CSF基因的入骨髓基质细胞系与脐血CD34+细胞共培养,观察细胞总数、CD34+细胞数、CFU-GM的变化情况.培养到第4周时,第(4)组(SCF+IL-3+IL-6+GM-CSF+FL)和第(8)组(HFCL/hGM-CSF+HFCL/hFL+SCF+IL-3+IL-6)的细胞总数增加到最大,分别扩增了717±24.47和709±63.63,第1周,第(5)组(HFCL+SCF+IL-3+IL-6)扩增了10.5±2.08倍,较第(8)组减少(P＜0.05).第1周时,CD34+细胞总数第(4)组和第(8)组分别扩增了8.44倍和11.5倍(P＜0.05),CD34+细胞百分率第(7)组(FCL/hFL+SCF+IL-3+II,-6)为50.2%,第(6)组(HFCL/hGM-CSF+SCF+IL-3+IL-6)为28.95%(P＜0.01).第2周,各组CFU-GM增加显著,以第(4)组和第(8)组增加最为明显,以后随扩增时间延长,造血细胞集落数、集落体积逐渐减少.表明转FL、GM-CSF基因的基质细胞,能有效的协同其他细胞因子对脐血CD34+细胞产生明显的扩增作用,能显著改变基质细胞造血功能.     

Chromosome analysis after ex vivo expansion of CD34(+) cells from human cord blood

Ex vivo expansion of cord blood hematopoietic progenitors is an attractive way to prepare a sufficient number of transplantable cells for cord blood transplantation in adult patients. The expanded cells need to have genetic stability. Karyotypic analysis of the expanded cells from cord blood CD34(+) cells by 7-day culture with stem cell growth factor, interleukin (IL)-3, IL-6, granulocyte colony-stimulating factor, and erythropoietin was performed. Several-fold increases in total cell number and CFU-GM were 186.7 +/- 62.1 and 27.1 +/- 9.4 (mean +/- standard deviation of data from 6 samples), respectively. Karyotypes were analyzed in 600 expanded cells in total, and all of them showed normal karyotypes. This observation suggests that multifactor supported expansion of cord blood cells may not induce karyotypic abnormality, although a limited number of ex vivo expanded cells were tested.     

CD34+ testicular stromal cells support long-term expansion of embryonic and adult stem and progenitor cells

Stem cells reside in specialized microenvironments created by supporting stromal cells that orchestrate self-renewal and lineage-specific differentiation. However, the precise identity of the cellular and molecular pathways that support self-renewal of stem cells is not known. For example, long-term culture of prototypical stem cells, such as adult spermatogonial stem and progenitor cells (SPCs), in vitro has been impeded by the lack of an optimal stromal cell line that initiates and sustains proliferation of these cells. Indeed, current methods, including the use of mouse embryonic fibroblasts (MEFs), have not been efficient and have generally led to inconsistent results. Here, we report the establishment of a novel CD34-positive cell line, referred to as JK1, derived from mouse testicular stromal cells that not only facilitated long-term SPC culture but also allowed faithful generation of SPCs and multipotent stem cells. SPCs generated on JK1 maintained key features of germ line stem cells, including expression of PLZF, DAZL, and GCNA. Furthermore, these feeders also promoted the long-term cultivation of other types of primitive cells including multipotent adult spermatogonial-derived stem cells, pluripotent murine embryonic stem cells, and embryonic germ cells derived from primordial germ cells. Stem cells could be passaged serially and still maintained expression of characteristic markers such as OCT4 and NANOG in vitro, as well as the ability to generate all three germ layers in vivo. These results indicate that the JK1 cell line is capable of promoting long-term culture of primitive cells. As such, this cell line allows for identification of stromal-derived factors that support long-term proliferation of various types of stem cells and constitutes a convenient alternative to other types of feeder layers. Disclosure of potential conflicts of interest is found at the end of this article.     

转JAK2基因脐血CD34+细胞体外扩增与生物学特性研究

目的： 探讨转基因JAK2介导的脐血干祖细胞长期扩增调控的可行性和转基因细胞的生物学特征。方法: 构建逆转录病毒载体MGI-F₂JAK2，内含有JAK2基因的功能催化区和2个与小分子靶向基因合成药物(AP20187)结合的位点蛋白(F36v，F₂)。应用MiniMACS磁珠分选系统纯化分离脐血CD34⁺细胞，用含JAK2的逆转录病毒上清转染脐血CD34⁺细胞。转染后的CD34⁺细胞在IMDM培养体系中，将细胞分为AP20187组;FL组；TPO组；AP20187+FL+TPO (AFT) 组。对扩增后的细胞定期检测基因转移后GFP动态变化、细胞免疫标记、造血祖细胞集落培养、染色体核型分析和裸鼠致瘤实验。结果: 分选的CD34⁺细胞纯度>91%，基因转移率为49.32%±6.21%；只有AP20187+FL+TPO组可以使转基因的脐血CD34⁺细胞大量增殖，扩增至第8周时细胞数达10⁹，CD34⁺细胞GFP的阳性率由基线水平逐渐上升并于第8周时达到90%以上；细胞表型为CD33⁺、CD61⁺、Gly-A⁺部分阳性；CD38⁺、HLA-DR⁺强阳性；CD2、CD7、CD19接近阴性。扩增的CD34+细胞可分别形成BFU-E、CFU-GM、CFU-Mix并以CFU-GM集落为主。扩增后CD34⁺细胞检测染色体核型正常，裸鼠实验无致瘤特性。结论: 转染JAK2 基因的人脐血CD34⁺细胞协同FL和TPO细胞因子可以体外长期扩增脐血干祖细胞，对今后研究细胞信号转导、造血调控以及开展干细胞和基因治疗都有潜在的应用价值。     

Substance P and calcitonin gene-related neuropeptides as novel growth factors for ex vivo expansion of cord blood CD34+ hematopoietic stem cells

There is little evidence on roles of growth factors other than cytokines in expansion of cord blood (CB) stem cells. We aimed to explore a novel approach for expansion, using Substance P (SP) and calcitonin gene-related peptide (CGRP) neuropeptides.

CB CD34⁺ cells were cultured in different concentrations of SP and/or CGRP in combination with a cytokine cocktail. Phenotypic and functional analysis was performed by flowcytometry and colonogenic assay.

Our results show a significant improvement of total expansion of neuropeptide treated cells. There was a selective effect of CGRP on CD34⁺ CD133⁺ cells, SP on CD34⁺ CD45^dim cells, and 10^{? 9} M SP and/or CGRP on expansion of CD34⁺ CD38^? cells. There was also a tendency for erythroid and granulocyte–myeloid colony formation in SP and CGRP treated cultures, respectively.

Supplementation of cytokines with other growth factors, such as neuropeptides, might enable us to overcome the difficulties of ex vivo expansion of CB cells.     

骨髓间充质干细胞对骨髓CD34~+细胞增殖影响的体外研究

研究骨髓间充质干细胞(bone marrow mesenchymal stem cell,BMMSC)对骨髓CD34+细胞增殖的影响,为骨髓CD34+细胞体外扩增的深入研究提供依据。用MACS进行骨髓CD34+细胞的分选;用流式细胞术进行CD34+细胞纯度鉴定;用密度梯度离心法分离引产胎儿骨髓单个核细胞,结合贴壁法进行BMMSC的体外扩增培养;用流式细胞术进行BMMSC表面标志鉴定;用Transwell培养板培养CD34+细胞与BMMSC;用自动细胞计数仪计数有活性的CD34+细胞数量;用MTT比色法检测骨髓CD34+细胞增殖活性。流式细胞术检测结果显示分选所得的CD34+细胞纯度达到90%以上;流式细胞术检测显示传至第3代继续培养72h后的BMMSC高表达CD44、CD29,而HLA-DR、CD45、CD34表达阴性,说明所培养的BMMSC纯度很高;Transwell培养板培养CD34+细胞与BMMSC,在倒置显微镜下观察以及自动细胞计数仪计数发现,实验组有活性的CD34+细胞数量高于对照组(P<0.05);采用MTT比色法检测骨髓CD34+细胞的增殖活性,实验组高于对照组(P<0.05)。以上结果说明BMMSC有促进骨髓CD34+细胞增殖的作用,这种作用可能与其分泌的细胞因子有关。     

MHC基因反义RNA导入造血干/祖细胞的研究

目的：将ＨＬＡＤＲＢ１基因ｃＤＮＡ片段反向插入逆转录病毒质粒ＺＩＰｎｅｏＳＶ（×）ＢａｍＨＩ位点中,构建了ＨＬＡＤＲＢ１基因的逆转录病毒反义ＲＮＡ重组表达载体,用脂质体法导入ＰＡ３１７细胞。方法：用免疫磁珠法分离,富集ＣＤ３４＋脐血造血干／祖细胞。含编码人ＨＬＡＤＲＢ１基因的ｐｃＤＶ１质粒,用ＢａｍＨＩ酶解,回收ＨＬＡＤＲＢ１ｃＤＮＡ片段,将ｃＤＮＡ片段反向插入ｐＺＩＰｎｅｏＳＶ（×）逆转录病毒载体,经扩增、抽提、酶切鉴定,用脂质体将反义ＲＮＡ重组体导入到ＰＡ３１７细胞,用含Ｇ４１８３００μｇ／ｍｌ培养液筛选,获抗性克隆,流式细胞仪检测ＨＬＡＤＲ抗原阳性细胞数。结果：重组质粒转染ＰＡ３１７细胞后,其病毒滴度达１×１０５ＣＦＵ／ｍｌ,脐血造血干／祖细胞经免疫磁珠富集后,ＣＤ３４＋细胞高达８５．０％～９０．０％,导入反义ＲＮＡ的脐血干细胞,其ＨＬＡＤＲ抗原表达从导入前的４５．０％降至２８．０％,抑制率达３８２％,而导入空载体后从５６．０％降至４５．０％,差异不显著。结论：ＨＬＡＤＲ的反义ＲＮＡ能导入脐血干细胞,降低ＨＬＡＤＲ抗原的表达     

造血干/祖细胞体外扩增的最新研究进展

造血干/祖细胞体外扩增方法的快速发展为造血干/祖细胞广泛应用于临床开辟了广阔的前景,就造血干/祖细胞体外扩增的方法和培养系统的最新进展做一综述。     

造血干/祖细胞体外扩增的最新研究进展

造血干/祖细胞体外扩增方法的快速发展为造血于/祖细胞广泛应用于临床开辟了广阔的前景,就造血干/祖细胞体外扩增的方法和培养系统的最新进展做一综述.     

骨髓CD34+细胞体外扩增诱导树突状细胞实验研究

目的探讨应用不同细胞因子组合方案从骨髓CD34+细胞体外扩增诱导树突状细胞(DC)的可行性及评价不同诱导方案诱导DC的效果.方法免疫磁珠法纯化骨髓CD34+细胞.在有血清条件下应用两步法SCF+FL+TPO+IL-3扩增2周,然后以GM-CSF+IL-4+TNF-α(GI方案)或GM-CSF+TNF-α(GT方案)诱导DC;或者一步法SCF+FL+TPO+IL-3+GM-CSF+TNF-α直接作用2周扩增诱导DC.通过相差显微镜、电子显微镜、流式细胞仪分析、异硫氰酸荧光素标记的葡聚糖(FITC-DX)内吞实验检测DC的生物学特性.结果诱导后细胞较0 d或诱导前细胞高表达DC相关标记(CD1a、CD80、CD86、CD40、CD54、HLA-DR).两步法GI方案诱导10 d,总细胞扩增倍数、CDla+DC扩增倍数分别为(198±178)倍和(122±129)倍,与GT方案比较无统计学意义,但诱导细胞CD1a、CD80、CD86的表达明显高于后者.一步法扩增诱导2周时总细胞数扩增(43±16)倍,CD1a+DC数是0 d接种细胞的(4±2)倍.结论两步法能从正常CD34+细胞诱导产生大量DC,GI方案优于GT方案.两者扩增效率均优于一步法.     

Adherent cells generated during long-term culture of human umbilical cord blood CD34+ cells have characteristics of endothelial cells and beneficial effect on cord blood ex vivo expansion

Hematopoiesis depends on the association of hematopoietic stem cells with stromal cells that constitute the hematopoietic microenvironment. The in vitro development of the endothelial cell from umbilical cord blood (UCB) is not well established and has met very limited success. In this study, UCB CD34(+) cells were cultured for 5 weeks in a stroma-free liquid culture system using thrombopoietin, flt3 ligand, and granulocyte-colony stimulating factor. By week 4-5, we found that firmly adherent fibroblast-like cells were established. These cells showed characteristics of endothelial cells expressing von Willebrand factor, human vascular cell adhesion molecule-1, human intracellular adhesion molecule-1, human CD31, E-selectin, and human macrophage. Furthermore, when comparing an ex vivo system without an established endothelial monolayer to an ex vivo system with an established endothelial monolayer, better expansion of total nucleated cells, CD34(+) cells, and colony-forming units (CFUs)-granulocyte-macrophage and CFUs-granulocyte-erythroid-megakaryocyte-macrophage were found during culture. This phenomenon was in part due to the fact that a significant reduction of apoptotic fractions was found in the CD34(+) cells, which were cultured on the adherent monolayer for up to 5 weeks. To gather quantitative data on the number of endothelial cells derived from a given number of CD34 cells, we performed limiting dilution assay by using Poisson distribution: the number of tested cells (linear scale) producing a 37% negative culture (logarithmic scale) is the number of cells containing one endothelial cell. By this method, one endothelial cell may be found from 314 CD34(+) cells after 5 weeks of culture. These results suggest that the UCB CD34(+) cell fraction contains endothelial cell precursors, establishing the hematopoietic microenvironment and providing the beneficial effects through downregulating apoptosis on UCB expansion protocols. These observations may provide insight for future cellular therapy or graft engineering.     

脐血CD34+CD19-造血干/祖细胞体外B细胞分化条件研究

目的:研究体外脐血造血干/祖细胞向B细胞分化的条件.方法:体外免疫磁珠分离纯化脐血CD34+CD19-造血干/祖细胞;在小鼠S-17基质细胞支持下,脐血CD34+CD19-造血干/祖细胞、T3、各种细胞因子共培养建立体外B细胞分化发育培养体系,诱导脐血CD34+CD19-造血干/祖细胞向B细胞分化;用流式细胞仪检测培养的B细胞.结果:T3、IL-7与小鼠S-17基质细胞共培养诱导CD34+CD19-造血干/祖细胞28天时,分化形成的B细胞数可达初始培养细胞的198倍,诱导细胞大部分表达CD10、CD19.结论:在选用的实验条件下,T3、IL-7与小鼠S-17基质细胞体外能诱导脐血造血干/祖细胞的B细胞分化.