造血负调控因子对骨髓基质细胞的调控作用

目的:探讨血小板第4因子(platelet factor 4,PF4)对急性辐射损伤人骨髓基质细胞(human bone marrow stromal cells,hBMSCs)的保护作用及机理,揭示PF4对造血系统辐射保护机制.方法:原代培养的hBMSCs随机分为4组:①PF4+照射组(P+I),②PF4保护组(P),③单纯照射组(I),④正常对照组(N).照射前给予1μ g·mL-1PF4或等量PBS预孵育12h,5.0 Gy60Co-γ射线均匀照射,20 h后收集各组细胞.MTT法测定细胞活性,观察细胞生长状态,流式细胞术检测细胞周期.RT-PCR测定P21、PCNAmRNA表达.结果:①PF4对人正常骨髓基质细胞生长无明显抑制或促进作用;②与I组相比,PF4明显提高5.0Gy60Co-γ射线照射后骨髓基质细胞的存活率,存活细胞达60%以上(I组<40%);③与N组和I组相比,P组和P+I组S期比例显著增高有统计学意义(P<0.001),但P组与P+I组相比无统计学差异;④RT-PCR结果显示,I组(+0.84±0.03)P21 mRNA表达较之N组(0.00±0.00)显著上调(P<0.01);而与I组相比,P组(+0.17±0.09)P21 mRNA表达显著下调(P<0.05 ).结论:PF4具有减轻电离辐射对人骨髓基质细胞的损伤作用,其调控机理可能与S期阻滞和下调P21基因表达有关.     

HIV-1 Tat蛋白抑制骨髓间充质干细胞的造血支持功能

目的:通过研究人类免疫缺陷病毒1型(HIV-1)Tat蛋白对骨髓间充质干细胞(BMSC)造血支持功能的影响,进一步揭示HIV-1感染者造血损伤的机理。方法:原代培养BMSC,流式检测其表面标志,诱导分化鉴定其多向分化潜能;免疫磁珠分选造血干细胞(HSC),流式检测其纯度;HIV-1 Tat蛋白添加到培养基中培养20天的BMSC(BMSC_(Tat))与对照BMSC(BMSC_(Con))分别作为滋养层与HSC分6组进行共培养,随后计数各组造血细胞总数,诱导分化检测造血细胞集落形成能力;RT-PCR检测BMSC_(Tat)和BMSC_(Con)造血相关因子mRNA的表达强度,ELISA检测BMSC_(Tat)和BMSC_(Con)条件培养液中造血相关因子GM-CSF及IL-6的浓度。结果:经鉴定成功培养获得原代BMSC;免疫磁珠分选的HSC纯度可达95%以上;分6组共培养进行比较,以BMSC_(Tat)为滋养层培养的造血细胞总数及造血细胞形成的集落总数均明显少于以BMSC_(Con)为滋养层;BMSC_(Tat)的造血相关因子的mRNA的表达明显弱于BMSC_(Con),BMSC_(Tat)的条件培养液中GM-CSF和IL-6的浓度均明显低于BMSC_(Con)。结论:HIV-1 Tat蛋白对BMSC的造血支持功能有明显的抑制作用。     

Embryonic Hematopoietic Progenitor Cells Reside in Muscle before Bone Marrow Hematopoiesis

In mice, hematopoietic cells home to bone marrow from fetal liver prenatally. To elucidate mechanisms underlying homing, we performed immunohistochemistry with the hematopoietic cell marker c-Kit, and observed c-Kit(+) cells localized inside muscle surrounding bone after 14.5 days post coitum. Flow cytometric analysis showed that CD45(+) c-Kit(+) hematopoietic cells were more abundant in muscle than in bone marrow between 14.5 and 17.5 days post coitum, peaking at 16.5 days post coitum. CD45(+) c-Kit(+) cells in muscle at 16.5 days post coitum exhibited higher expression of Gata2, among several hematopoietic genes, than did fetal liver or bone marrow cells. Colony formation assays revealed that muscle hematopoietic cells possess hematopoietic progenitor activity. Furthermore, exo utero transplantation revealed that fetal liver hematopoietic progenitor cells home to muscle and then to BM. Our findings demonstrate that hematopoietic progenitor cell homing occurs earlier than previously reported and that hematopoietic progenitor cells reside in muscle tissue before bone marrow hematopoiesis occurs during mouse embryogenesis.     

中空纤维灌注培养模拟骨髓造血研究

采用细胞工程技术探索造血细胞体外扩增技术以维持其自我更新潜能,抑制过度分化。方法：首先建立微载体 基质细胞体外造血模型（G1组,即瓶培养模式）,设置单纯微载体 基质细胞培养（G2组）和单纯骨髓细胞液体悬浮培养（G3组）作对照。检测各组粒系 巨噬系造血祖细胞集落产率（CFU GM/105）。自行设计1对引物,以检测Balb/c小鼠原始造血细胞c kit基因mRNA表达水平。试用中空纤维模拟血管灌注功能（Gh组,即中空纤维灌注模式）,以G1、G2、G3作对照,并对各组培养效果进行评价。结果：微载体 基质细胞体外造血模型实验结果显示：小鼠骨髓细胞培养2周后,CFU GM/105检测G1组比G3组高7.7倍（P<0.05）,是2个对照组（G2+G3）集落产率总和的1.9倍。原始造血细胞c kit mRNA表达水平：模型G1组比G2组高3.7倍,比G3组高62.3倍,且差异均显著。在成功建立微载体 基质细胞体外造血模型基础上进行中空纤维灌注培养实验,CFU GM/105检测显示：Gh组比G3组高4.6倍,并且略高于G2组;Gh组与G1组集落产率差别不明显。在原始造血细胞c kit mRNA表达水平上Gh组最高,从Gh、G1、G2到G3依次呈下降趋势。结论：在没有外加细胞因子的条件下,微载体 基质细胞和中空纤维灌注造血模型可抑制造血干、祖细胞过度分化与耗竭,维持其c kit较高的表达水平。     

Mineralization of Adult Mouse Bone Marrow In Vitro

Abstract. Murine adult bone marrow exhibits mineralizing capacity in vitro as is demonstrated by the new in vitro assay we report here. In less than 2 weeks after the onset of the cultures, mineralization is obtained in more than 80% of the marrow cultures. Moreover, morphological studies reveal that during incubation phenotypic changes related to osteogenic differentiation occur at the extracellular matrix as well within cell populations. Well banded collagen is synthesized. Matrix vesicles and needles of hydroxy-apatite crystals are observed via transmission electron microscopy. Osteoblast-like cells are present with membrane-associated alkaline phosphatase activity. the mineralization is specific for cultured bone marrow and is not observed in cultured spleen fragments as is shown via ⁸⁵Sr uptake, calcein uptake and histomorphology. No inducing agent is added to the tissue culture medium except for 10% fetal calf serum, beta-glycerophosphate (10⁻² M) and ascorbic acid. However, the prerequisite for obtaining mineralization is the three-dimensional structure of the marrow in culture. the in vitro organ culture we developed may provide the opportunity to identify which marrow cells have osteogenic potential and to investigate the mechanisms triggering differentiation towards osteogenesis.     

Derepression of the Iroquois Homeodomain Transcription Factor Gene IRX3 Confers Differentiation Block in Acute Leukemia

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Transcription Factor GATA1 Is Dispensable for Mast Cell Differentiation in Adult Mice

Although previous studies have shown that GATA1 is required for mast cell differentiation, the effects of the complete ablation of GATA1 in mast cells have not been examined. Using conditional Gata1 knockout mice (Gata1^−/y), we demonstrate here that the complete ablation of GATA1 has a minimal effect on the number and distribution of peripheral tissue mast cells in adult mice. The Gata1^−/y bone marrow cells were capable of differentiating into mast cells ex vivo. Microarray analyses showed that the repression of GATA1 in bone marrow mast cells (BMMCs) has a small impact on the mast cell-specific gene expression in most cases. Interestingly, however, the expression levels of mast cell tryptases in the mouse chromosome 17A3.3 were uniformly reduced in the GATA1 knockdown cells, and GATA1 was found to bind to a 500-bp region at the 5′ end of this locus. Revealing a sharp contrast to that observed in the Gata1-null BMMCs, GATA2 deficiency resulted in a significant loss of the c-Kit⁺ FcεRIα⁺ mast cell fraction and a reduced expression of several mast cell-specific genes. Collectively, GATA2 plays a more important role than GATA1 in the regulation of most mast cell-specific genes, while GATA1 might play specific roles in mast cell functions.     

Selection of Apoptotic Cell Specific Human Antibodies from Adult Bone Marrow

Autoreactive antibodies that recognize neo-determinants on apoptotic cells in mice have been proposed to have protective, homeostatic and immunoregulatory properties, although our knowledge about the equivalent antibodies in humans has been much more limited. In the current study, human monoclonal antibodies with binding specificity for apoptotic cells were isolated from the bone marrow of healthy adults using phage display technology. These antibodies were shown to recognize phosphorylcholine (PC)-associated neo-determinants. Interestingly, three of the four identified apoptotic cell-specific antibody clones were encoded by VH3 region rearrangements with germline or nearly germline configuration without evidence of somatic hypermutation. Importantly, the different identified antibody clones had diverse heavy chain CDR3 and deduced binding surfaces as suggested by structure modeling. This may suggest a potentially great heterogeneity in human antibodies recognizing PC-related epitopes on apoptotic cells. To re-construct the postulated structural format of the parental anti-PC antibody, the dominant clone was also expressed as a recombinant human polymeric IgM, which revealed a substantially increased binding reactivity, with dose-dependent and antigen-inhibitable binding of apoptotic cells. Our findings may have implication for improved prognostic testing and therapeutic interventions in human inflammatory disease.     

The Loss of Cbl-Phosphatidylinositol 3-Kinase Interaction Perturbs RANKL-mediated Signaling,Inhibiting Bone Resorption and Promoting Osteoclast Survival

Cbl is an adaptor protein and an E3 ligase that plays both positive and negative roles in several signaling pathways that affect various cellular functions. Tyrosine 737 is unique to Cbl and is phosphorylated by Syk and Src family kinases. Phosphorylated Cbl Tyr⁷³⁷ creates a binding site for the p85 regulatory subunit of PI3K, which also plays an important role in the regulation of bone resorption by osteoclasts. To investigate the role of Cbl-PI3K interaction in bone homeostasis, we examined the knock-in mice (Cbl^YF/YF) in which the PI3K binding site in Cbl is ablated due to the mutation in the regulatory tyrosine. We report that in Cbl^YF/YF mice, despite increased numbers of osteoclasts, bone volume is increased due to defective osteoclast function. Additionally, in ex vivo cultures, mature Cbl^YF/YF osteoclasts showed an increased ability to survive in the presence of RANKL due to delayed onset of apoptosis. RANKL-mediated signaling is perturbed in Cbl^YF/YF osteoclasts, and most interestingly, AKT phosphorylation is up-regulated, suggesting that the lack of PI3K sequestration by Cbl results in increased survival and decreased bone resorption. Cumulatively, these in vivo and in vitro results show that, on one hand, binding of Cbl to PI3K negatively regulates osteoclast differentiation, survival, and signaling events (e.g. AKT phosphorylation), whereas on the other hand it positively influences osteoclast function.