Induction of type B synoviocyte-like cells from plasmacytoid dendritic cells of the bone marrow in rheumatoid arthritis and osteoarthritis

We examined the capacities of bone marrow (BM) plasmacytoid dendritic cells (pDC) to differentiate into type B synoviocyte-like cells. BM aspiration samples were obtained from 24 rheumatoid arthritis (RA) patients and 19 osteoarthritis (OA) patients during joint operations from the iliac crest. CD34+ cells and pDC purified from BM mononuclear cells were cultured with or without SCF, GM-CSF, and TNF-α for 2-4 weeks. RA BM pDC as well as OA BM pDC comparably differentiated into fibroblast-like cells (FLC), expressing cadherin-11 and producing MMP-1, especially in the presence of TNF-α. Of note, depletion of BDCA4+ pDC from RA BM CD34+ cells significantly diminished their capacities to differentiate into FLC, which were restored by addition of BDCA4+cells in a dose-response manner. These results indicate that pDC is one of the progenitors of type B synoviocytes, suggesting that BM pDC might be involved in the pathogenesis of RA and OA.     

Bone marrow CD34+ progenitor cells stimulated with stem cell factor and GM-CSF have the capacity to activate IgD- B cells through direct cellular interaction

Recent studies have suggested the involvement of bone marrow in the pathogenesis of rheumatoid arthritis (RA), in which proliferation of monocyte-lineage cells (MLC) as well as local B cell activation in the synovium play an important role. Here, we show that bone marrow-derived MLC have the capacity to activate human peripheral blood IgD- B cells. Bone marrow CD34+ cells from RA patients that had been stimulated with stem cell factor and GM-CSF for 3-4 weeks (>90% CD14+ HLA-DR+ cells, <0.5% CD19+ B cells, and <0.5% CD3+ T cells; MLC) induced the production of IgG much more effectively than that of IgM by highly purified B cells from healthy donors in the presence of IL-2 and IL-10. CD34+ cells from cord blood or from bone marrow of osteoarthritis patients also displayed the capacity to induce IgG production. The induction of IgG production by the bone marrow-derived MLC was markedly decreased when they were separated from B cells by a membrane filter. The bone marrow-derived MLC interacted preferentially with IgD- B cells to induce IgG production. These results indicate that upon stimulation with stem cell factor and GM-CSF, CD34+ progenitor cells differentiate into MLC that activate preferentially IgD- B cells through direct cellular interactions to produce IgG. Therefore, the data suggest that the accelerated recruitment of MLC from the bone marrow to the synovium might play a role in the local B cell activation in RA.     

Suppressive influences of methotrexate on the generation of CD14(+) monocyte-lineage cells from bone marrow of patients with rheumatoid arthritis

An adequate supply of peripheral blood monocytes, granulocytes, and platelets is necessary for an optimal inflammatory process. We have previously demonstrated that the generation of CD14(+) monocyte lineage cells from the bone marrow is accelerated in patients with rheumatoid arthritis (RA). The current studies examined the influences of methotrexate (MTX), a potent disease modifying antirheumatic drug (DMARD), on the capacity of bone marrow progenitor cells to generate CD14(+) cells in patients with RA, in order to delineate its mechanism of action. CD14(-) cells purified from bone marrow specimens of 14 patients with active RA were cultured in the presence or the absence of pharmacologically attainable concentrations of MTX (0.2 microM). After incubation for 14 days, the cells were analyzed by flow cytometry for expression of CD14 and HLA-DR. The generation of CD14(+) cells from RA bone marrow CD14(-) progenitor cells was significantly suppressed by MTX. However, the expression of HLA-DR on bone marrow-derived CD14(+) cells was not significantly influenced by MTX. There was no significant difference in the effect of MTX on the generation of CD14(+) cells between patients with prednisolone and those without prednisolone. The production of IL-12 in bone marrow cell cultures was not inhibited, but was rather enhanced, by MTX, suggesting that the suppression of the generation of CD14(+) cells might not be due to the inhibition of cytokine production. The results are consistent with the hypothesis that one of the effects of DMARDs may involve the interference with monocyte differentiation in the bone marrow. Moreover, the data suggest that the generation of CD14(+) cells and the expression of HLA-DR on such marrow-derived CD14(+) cells are regulated by different mechanisms.     

Generation of dendritic cells from bone marrow progenitors using GM-CSF, TNF-alpha, and additional cytokines: antagonistic effects of IL-4 and IFN-gamma and selective involvement of TNF-alpha receptor-1.

We report the generation of dendritic cells (DC) starting from CD34+ bone marrow (BM) progenitor cells, using a two-stage culture system in which, besides granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumour necrosis factor-alpha (TNF-alpha), stem-cell factor (SCF) was added during the first 5 days, while interleukin-4 (IL-4) and/or interferon-gamma (IFN-gamma) were added during the secondary culture period of 9 days. Addition of IL-4 favoured the outgrowth of CD1a+, HLA-DR+, CD4+, CD40+, CD80+ but CD14- cells with dendritic morphology and strong antigen-presenting capacity. Addition of IFN-gamma selectively induced HLA-DR and CD86 but did not up-regulate CD1a expression or antigen-presenting capacity of the differentiated cells. An antagonism between IL-4 and IFN-gamma could further be confirmed in that, as compared with IL-4 alone, the simultaneous addition of IL-4 and IFN-gamma to GM-CSF plus TNF-alpha during maturation reduced both the phenotypical (CD1a, CD4, CD40) and functional characteristics of DC. Using receptor-specific TNF-alpha mutants, we investigated the relative involvement of TNF-alpha receptors R1 and R2 in the generation of DC. The induction of CD1a and HLA-DR, as well as the increase in allostimulatory capacity were dependent on TNF-R1 triggering, whereas triggering through TNF-R2 had no measurable effect. We conclude first, that the expansion of DC from BM progenitors could most effectively be enhanced in a two-stage culture assay using SCF, GM-CSF, TNF-alpha and IL-4; second, that the effect of TNF-alpha in DC generation involves signalling via the TNF-R1 receptor; and third, that IFN-gamma counteracts some of the effects of IL-4 in DC generation.     

猕猴骨髓干细胞动员后外周血干细胞、免疫细胞亚群及细胞因子变化

目的:观察GM-CSF动员猕猴骨髓干细胞后外周血干细胞、免疫细胞亚群和细胞因子含量的动态变化,为临床干细胞动员及用于治疗疾病提供参考依据.方法:健康猕猴连续5 d,皮下注射GM-CSF 8 μg/(kg·d),分别于0、2、4、6、8、10 d采集外周血,血细胞分析仪计数白细胞(WBC)总数、淋巴细胞和中性粒细胞比例,流式细胞术(FCM)测定CD34 、CD133 、CD3 、CD4 、CD8 、CD56 细胞比例,酶联免疫分析法测定血清TNF-α、IL-1β、IL-2含量.结果:WBC、中性粒细胞、CD34 、CD133 细胞数量和比例均同步升高(P＜0.01),到动员第6天时达到高峰,细胞数量分别为正常水平的6.4、9.1、117和163.3倍,其中CD34 、CD133 第8天时恢复正常,而WBC、中性粒细胞仍高于正常水平(P＜0.05).CD3 、CD4 、CD8 、CD56 细胞的数量增加,细胞数在第6天时分别为动员前的4.1、4.0、2.9和4.3倍,但比例下降(P＜0.01),到第6天达到最低(P＜0.001),随后逐渐升高至正常以上水平并持续至第10天(P＜0.05).TNF-α、IL-1β、IL-2浓度于动员后6 d内明显升高(P＜0.01),其中TNF-α、IL-1β浓度至8 d恢复正常(P＞0.05),IL-2浓度升高幅度较大并至少持续至第10天(P＜0.01).结论:连续5 d动员猕猴骨髓干细胞可使外周血中CD34 、CD133 细胞比率短暂升高,WBC、中性粒细胞比例持续升高,使CD3 、CD4 、CD8 、CD56 细胞绝对数增加,TNF-α、IL-1β、IL-2浓度升高,表明GM-CSF动员猕猴骨髓干细胞可在细胞和免疫调节因子水平提高免疫功能.     

Selective generation of different dendritic cell precursors from CD34+ cells by interleukin-6 and interleukin-3

There is a growing interest in generating dendritic cells (DCs) for using as vaccines. Several cytokines, especially stem cell factor (SCF) and FLT3-ligand (FL), have been identified as essential to produce large numbers of myeloid precursors and even to increase DC yield obtained by the action of granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF-alpha). However, there are few studies on the effect of the early-acting cytokines, commonly used to expand CD34+ progenitor cells, on DC generation. We report here that in the absence of serum, SCF, FL, and thrombopoietin (TPO) plus interleukin-6 (IL-6) and SCF, FL, and TPO plus IL-3 were able to generate CD14+CD1a- and CD14- CD1a+ myeloid DC precursors from CD34+ cells, but IL-6 had an inhibitory effect on the generation of CD14- CD1a+ cells. Both DC precursors differentiated into mature DCs by GM-CSF, IL-4, and TNF-alpha, and DCs obtained from both types of culture exhibited equal allostimulatory capacity. CD1a+ DCs generated could be identified on the basis of DC-specific intracellular adhesion molecule-grabbing nonintegrin (DC-SIGN) expression, a novel C-type lectin receptor expressed on dermal DCs but not on Langerhans cells. In addition, the inclusion of IL-3 to the culture medium induced the appearance of CD13- cells that differentiated into plasmacytoid DC (DC2) on the addition of TNF-alpha, allowing the identification of developmental stages of DC2. Like true plasmacytoid DCs, these cells secreted interferon-alpha after TLR9-specific stimulation with a specific CpG nucleotide.     

Characterization of the adherent cells developed in Dexter-type long-term cultures from human umbilical cord blood

We have previously shown that when human umbilical cord blood (UCB) cells are cultured in standard Dexter-type long-term cultures (D-LTC), adherent cells develop forming a discrete net on the bottom of the culture flask. The identity of such cells, however, has not been defined. Accordingly, the major goal of the present study was to characterize the adherent cells developed in standard UCB D-LTC. Cultures were established from 14 UCB samples and from nine bone marrow (BM) samples, as controls. Both UCB and BM cultures were initiated with the same number of mononuclear cells (MNC) (2.5 x 10(6) MNC/ml). After three weeks in culture, adherent cell numbers in UCB D-LTC were 24%-30% of the numbers found in BM cultures. More than 90% of the adherent cells in UCB D-LTC expressed the acid phosphatase enzyme, whereas no alkaline phosphatase-positive cells were observed. This was in contrast to BM D-LTC, in which alkaline and acid phosphatase were expressed by 60%-75% and 20%-45% of the adherent cells, respectively. Immunochemical analysis showed that CD61 (osteoclast marker) and Factor VIII (endothelial cell marker) were not expressed by the adherent cells developed in UCB cultures. Interestingly, the majority of such cells expressed CD1a (dendritic cell marker), CD14, CD68 and CD115 (antigens mainly expressed by macrophagic cells). When the cultures were supplemented with the recombinant cytokines epidermal growth factor, basic fibroblast growth factor, platelet-derived growth factor or granulocyte-macrophage colony-stimulating factor (GM-CSF), only GM-CSF had a significant positive effect on adherent cell number. In order to test for some functional properties of the adherent cells developed in culture, production of stem cell factor (SCF), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) was assessed. IL-6 and TNF-alpha showed elevated levels in UCB D-LTC, whereas SCF levels were always below detection. Finally, analysis of fibroblast progenitors (fibroblast colony-forming units [CFU-F]) showed that these cells were present in BM samples (6 CFU-F/10(5) MNC) and were totally absent in UCB samples. Taken together, the results of the present study indicate that the vast majority of the adherent cells developed in standard UCB D-LTC belong to the macrophage lineage and that fibroblasts seem to be absent. Interestingly, the high proportion of CD1a+ cells suggests that dendritic cells are also present in these cultures.     

Allergen stimulates bone marrow CD34+ cells to release IL‐5 in vitro; a mechanism involved in eosinophilic inflammation?

The specific mechanisms that alter bone marrow (BM) eosinophilopoiesis in allergen-induced inflammation are poorly understood. The aims of this study were to evaluate (a) whether the number of BM CD34(+) cells is altered due to allergen sensitization and exposure in vivo and (b) whether BM CD34(+) cells produce and release interleukin (IL)-5, IL-3 and granulocyte macrophage-colony stimulating factor (GM-CSF) after stimulation in vitro. A mouse model of ovalbumin (OVA)-induced airway inflammation was used. Bone marrow CD34(+) cells were cultured in vitro and the cytokine release was measured by enzyme-linked immunosorbent assay. The IL-5-production from CD34(+) cells was confirmed by immunocytochemistry. Airway allergen exposure increased the number of BM CD34(+) cells (P = 0.01). Bone marrow CD34(+) cells produced IL-5 when stimulated with the allergen OVA in vitro, but not IL-3 or GM-CSF. Nonspecific stimulus with calcium ionophore and phorbol-myristate-acetate of BM CD34(+) cells caused release of IL-5, IL-3 and GM-CSF. The induced release of IL-5 was increased in alum-injected vs naive mice (P = 0.02), but was not affected by allergen sensitization and exposure. The release of IL-3 and GM-CSF was increased after allergen sensitization and exposure (P < 0.02). In conclusion, allergen can stimulate BM CD34(+) cells to produce IL-5 protein. It is likely that the CD34(+) cells have autocrine functions and thereby regulate the early stages of BM eosinophilopoiesis induced by airway allergen exposure. Alum, a commonly used adjuvant, enhances the release of IL-5 and may thereby enhance eosinophilopoiesis.     

Flt-3 ligand, in combination with bovine granulocyte-macrophage colony-stimulating factor and interleukin-4, promotes the growth of bovine bone marrow derived dendritic cells

Culture of bone marrow precursor cells with cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-4 (IL-4) and the tyrosine kinase receptor binding proteins Flt-3 ligand (Flt-3L) and stem-cell factor (SCF), has previously been shown, in both mouse and human, to result in the generation of large numbers of dendritic cells. We extend these findings to bovine dendritic cells. Culture of bovine bone marrow cells with GM-CSF, IL-4 and either Flt-3L or SCF enhanced the generation of low buoyant-density dendritic cells. However, only the addition of Flt-3L to cells cultured with GM-CSF and IL-4 was shown to increase the number of dendritic cells and induce the differentiation of dendritic cells with potent capacity to stimulate allogeneic T cells and resting CD4+ memory T cells. The effective ability to stimulate T cells was associated with the expression of major histocompatibility complex (MHC) class II molecules and CD80/86 by dendritic cells. Bovine bone marrow derived dendritic cells appeared to be exclusively of myeloid origin because they expressed the myeloid-related antigens CD14, MyD-1 and CD11b.     

Expansion of dendritic cell precursors from human CD34(+) progenitor cells isolated from healthy donor blood; growth factor combination determines proliferation rate and functional outcome

CD34(+) haematopoietic progenitor cells, which circulate at extremely low frequencies in peripheral blood, are used to generate dendritic cells (DC) in vitro. Here, we describe a method to grow large numbers of DC precursors from these low frequent cells. Different combinations of early acting haematopoietic growth factors supported expansion of CD34(+) cells. CD1a(+) DC derived from precursors, expanded in fms-like tyrosine kinase-3 ligand (Flt3-L), stem-cell factor (SCF), interleukin (IL)-3, and IL-6, were less potent antigen-presenting cells (APC) compared to CD1a(+) DC derived from precursors expanded in Flt3-L, trombopoietine (TPO), and SCF. Furthermore, the latter produced high levels of IL-12 and low levels of IL-10, a cytokine profile favorable for the priming cytotoxic T cells. In contrast, a mean increase of total cell number of 453-fold was obtained with Flt3-L, SCF, IL-3, and IL-6, and this increase was only 38-fold with Flt3-L, TPO, and SCF. Sequential cultures of both cocktails resulted in high numbers of potent APC, which can be useful DC-based cancer vaccines.     

Generation of functional and mature dendritic cells from cord blood and bone marrow CD34+ cells by two-step culture combined with calcium ionophore treatment

The object of this study is to explore a culture method to generate a large number of functional and mature dendritic cells (DC) from human CD34+ hematopoietic progenitor cells. In the present study, we used a two-step method combined with calcium ionophore to induce DC from cord blood (CB) or normal human bone marrow (BM) CD34+ progenitor cells. The two-step method consists of 10 days of first step culture for the expansion and proliferation of CD34+ hematopoietic progenitor cells in the presence of SCF, IL-3, IL-6, G-CSF, and 7--11 days of second step culture for the induction of DC in the presence of GM-CSF, IL-4 and TNF-alpha. By the two-step culture, total nucleated cells were increased 208+/-66 (+/-SD, n=13), or 94+/-29 (n=5)-fold in the culture of CB or BM cells, respectively, compared with the number of CD34+ cells at the time of starting culture. Out of the total nucleated cells, 23 +/-10.4% of cells in CB cell culture and 25 +/-5% of cells in the BM cell culture acquired DC characteristic phenotypes, which were marked expressions of CD1a, HLA-DR, co-stimulatory molecules such as CD80, CD40, and adhesion molecule such as CD58. In allogeneic mixed leukocyte reaction (MLR), two-step cultured cells showed potent allo-stimulatory capacity. With this two-step culture, the absolute number of CD1a+ cells that co-expressed HLA-DR, CD80, CD40 and CD58 was enhanced approximately 3 times in CB cell culture and 1.9 times in BM cell culture, compared with the commonly used one-step culture method for the generation of DC from CD34+ cells using SCF, GM-CSF and TNF-alpha. However, on these DC generated in the two-step culture, the expressions of co-stimulatory molecule CD86 and mature DC marker CD83 were not sufficient. By the treatment of two-step cultured cells with calcium ionophore agent (A23187), the expression of co-stimulatory molecules such as CD86 and CD80 (especially CD86) was up-regulated. Besides, the expression of mature DC marker CD83 was remarkably induced by treatment with A23187 for a short duration (24 h). Consistent with the up-regulation of surface molecules CD86, CD80 and CD83, the two-step cultured cells treated with A23187 also showed a stronger allo-stimulatory capacity compared with the cells without A23187 treatment. In conclusion, the present study demonstrated that the two-step culture method effectively improved the yield of CD1a+ DC generated from CD34+ cells, and the phenotypes and functions of these CD1a+ DC could be enhanced efficiently by treatment with a calcium ionophore agent.     

The generation of dendritic-like cells with increased allostimulatory function from acute myeloid leukemia cells of various FAB subclasses

To increase the immunogenicity of leukemic cells, attempts were made to generate dendritic-like antigen presenting cells (DC) from AML blasts from 14 patients with AML FAB classifications M0-M5. Leukemic cells were cultured in the presence or absence of various cytokines including GM-CSF, SCF, TNF-alpha, IL-4, and gamma-interferon. After various intervals recovery of viable cells was measured and expression of CD80, CD86, CD40, CD54, CD58, and CD11a was analyzed by flow cytometry. Functionally, DC derived from six AML samples were tested in a mixed lymphocyte response (MLR) using HLA-DR mismatched donor T cells as responder cells. Proliferation (5/14) or increased survival (7/14) of AML cells was observed in the presence of GM-CSF, SCF, and TNF-alpha. Only in the AML M2, M3, and M4 FAB subtypes proliferation was found. GM-CSF, SCF, and TNF-alpha induced morphologic changes typical for DC and increased the expression of costimulatory and adhesion molecules. No significant effect of IL-4 or gamma-interferon was observed. The day of maximal expression of these molecules varied. In cases with minor upregulation of CD80 or CD86, no further stimulation using CD40-L activation was observed. In the three cases tested, the DC-like cells retained the chromosomal abnormalities present in the original AML cells. In five out of six cases tested an increase in allostimulatory capacity was found at the day of maximal expression of costimulatory and adhesion molecules. In two patients a decrease in stimulatory capacity was found at day 7 compared with day 2 correlating with a decreased expression of these molecules. In conclusion, AML cells can be induced to increase their stimulatory capacity by upregulating costimulatory and adhesion molecules.     

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.     

Differential kinetics of primitive hematopoietic cells assayed in vitro and in vivo during serum-free suspension culture of CD34+ blood progenitor cells.

So far, blood progenitor cells (BPC) expanded ex vivo in the absence of stromal cells have not been demonstrated to reconstitute hematopoiesis in myeloablated patients. To characterize the fate of early hematopoietic progenitor cells during ex vivo expansion in suspension culture, human CD34(+)-enriched BPC were cultured in serum-free medium in the presence of FLT3 ligand (FL), stem cell factor (SCF) and interleukin 3 (IL-3). Both CD34 surface expression levels and the percentage of CD34+ cells were continuously downregulated during the culture period. We observed an expansion of colony-forming units granulocyte-macrophage (CFU-GM) and BFU-E beginning on day 3 of culture, reaching an approximate 2-log increase by days 5 to 7. Limiting dilution analysis of primitive in vitro clonogenic progenitors was performed through a week 6 cobblestone-area-forming cell (CAFC) assay, which has previously been shown to detect long-term bone marrow culture-initiating cells (LTC-IC). A maintenance or a slight (threefold) increase of week 6 CAFC/LTC-IC was found after one week of culture. To analyze the presence of BPC mediating in vivo engraftment, expanded CD34+ cells were transplanted into preirradiated NOD/SCID mice at various time points. Only CD34+ cells cultured for up to four days successfully engrafted murine bone marrow with human cells expressing myeloid or lymphoid progenitor phenotypes. In contrast, five- and seven-day expanded human BPC did not detectably engraft NOD/SCID mice. When FL, SCF and IL-3-supplemented cultures were performed for seven days on fibronectin-coated plastic, or when IL-3 was replaced by thrombopoietin, colony forming cells and LTC-IC reached levels similar to those of control cultures, yet no human cell engraftment was recorded in the mice. Also, culture in U-bottom microplates resulting in locally increased CD34+ cell density had no positive effect on engraftment. These results indicate that during ex vivo expansion of human CD34+ cells, CFC and LTC-IC numbers do not correlate with the potential to repopulate NOD/SCID mice. Our results suggest that ex vivo expanded BPC should be cultured for limited time periods only, in order to preserve bone-marrow-repopulating hematopoietic stem cells.     

4种细胞因子组合方式对小鼠树突状细胞分化发育的影响

目的观察在体外培养时4种细胞因子(CK)组合方式对小鼠骨髓源树突状细胞(DC)分化、增殖、发育的影响.方法用不同的CK定向诱导小鼠骨髓细胞分化为DC,通过流式细胞仪(荧光抗体双标记法)测定CD11c+细胞比例、MHC-Ⅱ类分子的表达及在脂多糖(LPS)刺激后CD86表达的变化.结果GM-CSF+IL-3+SCF促进DC分化、增殖的能力明显高于其他3组(P＜0.05).该组CK所诱导的DC在LPS刺激后,CD86表达增加的幅度明显低于GM-CSF+IL-4组(P＜0.01).结论GM-CSF、IL-3和SCF对于促进小鼠骨髓细胞向DC定向分化、增殖有协同作用,分化后的DC多数处于发育早期,DC前体所占的比例较大.     

The expansion of megakaryocyte progenitors from CD34+-enriched mobilized peripheral blood stem cells is inhibited by Flt3-L.

This study aimed to determine the optimal growth factor combination for expansion of megakaryocyte (Mk) progenitors with clonogenic potential from CD34+-enriched mobilized peripheral blood stem cells (PBSC). Mobilized PBSC were monocyte depleted and CD34+ enriched, then cultured with various combinations of interleukin-3 (IL-3), IL-6, IL-11, Flt3 ligand (Flt3-L), stem cell factor (SCF), granulocyte-macrophage colonystimulating factor (GM-CSF), and erythropoietin (EPO), using a 2(7-3) IV fractional factorial design. Expansion of Mk committed progenitors (CD41+) and primitive precursors (CD61+ CD34+) was determined using FACS and colony-forming assays. Amplification of Mk progenitor production was attributed to IL-3 (p < 0.002), SCF (p < 0.001), and GM-CSF (p < 0.05). Flt3-L inhibited the production of total CD61+ cells (p < 0.05), CD61+CD34+ cells (p < 0.03), and total CD41a+ cells (p < 0.01). Addition of Flt3-L to the optimum growth factor combination of megakaryocyte growth and development factor (MGDF), SCF, IL-3, and GM-CSF caused the greatest increase in total nucleated cells but reduced Mk progenitor expansion. There was also a 20% reduction in Mk+ colonies from cells expanded in the presence of Flt3-L. Factorial analysis identified the optimal combination of growth factors required to expand Mk precursors with clonogenic potential. The addition of Flt3-L to the optimal combination of MGDF, SCF, IL-3, and GM-CSF reduced both the fold expansion of Mk progenitors and Mk colony numbers.     

Evidence of peripheral blood-derived, plastic-adherent CD34(-/low) hematopoietic stem cell clones with mesenchymal stem cell characteristics

The hematopoietic system of vertebrates can be completely reconstituted with hematopoietic stem cells derived from the bone marrow, fetal liver, or cord blood, or even from peripheral-blood-derived cells. A cellular marker to identify those cells is the proteoglycan CD34, although we have shown that the earliest identifiable hematopoietic stem cell is a CD34(-) fibroblast-like cell which can differentiate into CD34(+) hematopoietic precursors. Peripheral blood mononuclear cells were isolated from the heparinized blood of a dog and incubated in tissue culture in the presence of interleukin 6. After 10-14 days, an adherent layer of fibroblast-like cells had developed and cells were immortalized using the SV-40 large T antigen. Cells were cloned and subcloned by measures of limiting dilution, and various fibroblast-like clones were established. These fibroblast-like cells either do not express the CD34 antigen or express CD34 on a low level, although transcribing CD34. The CD34(-/low) cells express osteocalcin as a mesenchymal cell marker. The fibroblast-like cells eventually differentiate spontaneously in vitro into CD34(+) precursors and show colony formation. Prior to autologous stem cell transplantation, one clone of choice (IIIG7) was transfected with a retroviral construct containing the green-fluorescence protein (GFP). The recipient dog was totally irradiated with 300 cGy and received a stem cell transplant with GFP-containing, immortalized, fibroblast-like monoclonal autologous stem cells (0.5 x 10(8)/kg dog). No additional growth factors were applied. The peripheral blood counts recovered after 23 days (WBC >500; platelets >10,000). A peripheral blood smear showed some dim but definite, although timely, limited expression of the GFP protein in nucleated peripheral blood cells just five weeks after transplantation. A bone marrow biopsy showed GFP-positive cells in the marrow cavity predominantly as "bone-lining cells."