巨核细胞生成中的细胞因子和转录因子调节

巨核细胞生成包括巨核系祖细胞增殖、分化为未成熟的巨核细胞，再进一步分化为成熟巨核细胞并释放血小板的过程。在巨核系造血的早期阶段，主要由TPO、IL-1、IL-3和PDGF调控，在分化后期有TPO、IL-6和IL-11参与。多个转录因子也参与巨核细胞的分化过程，GATA-1、FOG-1和Fil-1调节早期及中期的巨核细胞生成，NFE2参与晚期巨核细胞分化和血小板的生成。本文综述有关细胞因子及转录因子在调控巨核细胞和血小板生成中的作用。     

巨核细胞生成中的细胞因子和转录因子调节

巨核细胞生成包括巨核系祖细胞增殖、分化为未成熟的巨核细胞,再进一步分化为成熟巨核细胞并释放血小板的过程.在巨核系造血的早期阶段,主要由TPO、IL-1、IL-3和PDGF调控,在分化后期有TPO、IL-6和IL-11参与.多个转录因子也参与巨核细胞的分化过程,GATA-1、FOG-1和Fil-1调节早期及中期的巨核细胞生成,NF-E2参与晚期巨核细胞分化和血小板的生成.本文综述有关细胞因子及转录因子在调控巨核细胞和血小板生成中的作用.     

巨核细胞生成负调控因子的研究进展

血小板的生成包括巨核细胞自造血干细胞分化、增殖、成熟及血小板产生的过程。巨核细胞生成的正调控因于主要有巨核细胞生长衍生因子（MGDF），即TPO；血小板衍生生长因于（PDGF）；白细胞介素IL-1，IL-3，IL-6，IL-11，IL-13等。     

巨核细胞发育和血小板生成的调控机制

巨核细胞发育是一个涉及多极信号的复杂生物过程,包括造血干细胞的增殖、巨核系祖细胞的分化和成熟的巨核细胞产生血小板.巨核细胞的发育和血小板的产生调控机制受多种造血生长因子、趋化因子及相应的信号转导通路和转录因子协同调控.从细胞的形态、血清中的细胞因子到RNA、DNA,巨核细胞的研究可谓发展迅速.现就目前所认识的调控巨核细胞成熟和促血小板生成的相关因子进行综述.     

体外诱导骨髓细胞分化成巨核细胞的方法学研究

目的:探讨体外将小鼠骨髓细胞诱导分化为巨核细胞的方案,用于中药活性评价。方法:从小鼠股骨和胫骨取骨髓细胞,在血小板生成素(TPO)及TPO和干细胞因子(SCF)或TPO、SCF、白介素-6(IL-6)和白介素-9(IL-9)联合诱导下,体外培养6 d。然后用倒置显微镜观察培养体系中的细胞生长情况,自动细胞计数仪检测细胞数量,流式细胞术分析培养体系中巨核细胞比例,并计算巨核细胞绝对数量。结果:单因子或多因子联合诱导方法均能体外促进骨髓细胞分化成巨核细胞,TPO轻微促进骨髓细胞分化成巨核细胞,TPO和SCF联合及TPO、SCF、IL-6和IL-9联合均显著促进骨髓细胞增殖和分化成巨核细胞,添加IL-6和IL-9可促进骨髓细胞分化成巨核细胞,减少非巨核细胞增殖。结论:TPO、SCF、IL-6和IL-9联合具有最强的促进骨髓细胞分化为巨核细胞的作用,可以用于促血小板形成中药活性筛选和评价。     

胺类神经递质对巨核细胞造血调控及血小板功能的作用简

作为宿主防御和机体修复机制的一部分,神经系统可能通过免疫细胞上的神经递质受体直接参与免疫功能的调控,而多种神经递质受体在血液细胞上表达的发现,为神经系统与血液系统之间直接联系提供了依据.我们课题组前期研究显示胺类神经递质中的5-HT与巨核系造血有紧密的联系.本文以胺类神经递质对巨核系造血的调控及巨核细胞、血小板功能的影响做为关注点作一综述,着重于其相关受体在造血干细胞、巨核细胞及血小板上的表达及相应的功能,探索神经系统与血液系统的内在联系.依据现有的研究结果,我们发现胺类神经递质参与了巨核细胞造血的调控,可影响血小板聚集及活化功能,且与巨核系特异调节因子TPO存在联系,也支持了一些研究者所提出的“脑-骨髓-血液轴”观点.目前,神经系统参与造血调控的研究尚处于起步阶段,其具体机制尚有待进一步研究.     

重组人血小板生长因子促进受照射小鼠巨核系和红系造血的恢复(英文)

血小板生长因子(TPO)是巨核细胞系唯一的特异性生理性正调控因子。它可诱导造血干、祖细胞向巨核细胞系分化,促进巨核细胞的发育成熟及血小板的生成和释放。为了研究TPO的生物活性,我们给~(60)Co照射小鼠腹腔注射重组入TPO (rhTPO),每天0.2mg/kg体重或0.3mg/kg体重,连续20天。检测了小鼠的外周血象及骨髓造血祖细胞的培养。结果rhTPO治疗组小鼠的外周血血小板计数下降较慢,并且提前恢复,尤其是在0.3mg/kg体重组(P<0.05-P<0.01)。骨髓造血祖细胞培养见rhTPO治疗组小鼠的骨髓CFU-MK和BFU-E(10天),较对照组明显增高(P<0.01)。骨髓GM-CFU与对照组比较无显著差别。因此,我们认为rhTPO可促进受照小鼠巨核细胞系和红细胞系造血的重建,是临床治疗骨髓抑制性血小板减少的有希望的生物治疗药物。     

慢性高原病患者骨髓TPO及其受体C-MPL水平测定

慢性高原病(CMS)是在高原低压性缺氧环境下发生的红细胞增殖性疾病,而红细胞的增殖与分化受多种造血生长因子、转录因子、骨髓造血微环境的共同调控.近年来的多项研究表明CMS的发生、发展是多种因素对造血细胞综合作用的结果,同时,在实际临床工作中,我们还发现部分患者体内血小板水平减低,并且未能发现其他引起血小板减低的原因,而TPO作为巨核系生长发育的特异性调节因子,已有研究表明其对早期骨髓造血及晚期红细胞生成均有促增殖及分化效应[1],在其受体C-MPL基因敲除小鼠体内红系的生长发育受到明显的抑制.因此,我们在研究中检测CMS患者骨髓单个核细胞(MNC)中C-MPL mRNA水平和骨髓细胞中的阳性表达,同时测定骨髓卜清中TPO水平,初步探讨TPO及C-MPL在CMS发生、发展中的作用.     

巨核细胞发育和血小板生成的调控

巨核细胞的主要生理功能是产生血小板,其发育、成熟和血小板生成是多因素参与的复杂调控过程。近年来研究发现,除骨髓之外,肺也是巨核细胞生成血小板的主要场所。本综述以近年的研究结果为基础,概述了巨核细胞发育、成熟及血小板生成的过程,重点解析了凋亡因子、miRNA、血小板生成素及其受体、白介素、转录因子及相应的信号转导通路对血小板生成的调控作用。了解血小板生成调控机制,可有助于了解血小板相关疾病的病理机制,为临床上血小板相关疾病的诊断及治疗提供新思路。     

5-羟色胺对巨核系造血的影响

5-羟色胺（5-HT）是一种细胞生长因子，主要结合到细胞表面的5-HT1受体、5-HT2受体，通过Ras、MAPK通路促进多种细胞的增殖。在巨核系造血的早期，5-HT通过5-HT2B受体促进造血干细胞及巨核系祖细胞增殖和分化，其具体机制尚未十分清楚；在巨核系造血晚期，5-HT与5-HT2A受体结合促进一氧化氮合成，可能对血小板的释放有一定的影响。另外，5-HT能够对抗血小板α颗粒内容物血小板反应蛋白-1（TPS-1）所引起的巨核细胞凋亡，协同另一内容物血小板源性生长因子（PDGF）引起的巨核细胞增殖，因此5-HT可能是血小板反馈调节中比较重要的物质。本文就5HT及其受体、5HT是细胞生长因子、5HT促进细胞增殖的途径及5HT对巨核系祖细胞的影响进行了综述。     

Physiological regulation of early and late stages of megakaryocytopoiesis by thrombopoietin

Thrombopoietin (TPO) has recently been cloned and shown to regulate megakaryocyte and platelet production by activating the cytokine receptor c-mpl. To determine whether TPO is the only ligand for c-mpl and the major regulator of megakaryocytopoiesis, TPO deficient mice were generated by gene targeting. TPO-/- mice have a >80% decrease in their platelets and megakaryocytes but have normal levels of all the other hematopoietic cell types. A gene dosage effect observed in heterozygous mice suggests that the TPO gene is constitutively expressed and that the circulating TPO level is directly regulated by the platelet mass. Bone marrow from TPO-/- mice have decreased numbers of megakaryocyte-committed progenitors as well as lower ploidy in the megakaryocytes that are present. These results demonstrate that TPO alone is the major physiological regulator of both proliferation and differentiation of hematopoietic progenitor cells into mature megakaryocytes but that TPO is not critical to the final step of platelet production.     

Preferential ex vivo expansion of megakaryocytes from human cord blood CD34+-enriched cells in the presence of thrombopoietin and limiting amounts of stem cell factor and Flt-3 ligand

The high proliferative potential of cord blood (CB) stem cells and the identification of the key factor of megakaryopoiesis, thrombopoietin (TPO), permit the ex vivo expansion of megakaryocytes (MKs) for possible use in early post-transplant support of patients and the production of functional platelets for transfusion. However, culture conditions for the generation of adequate MKs for this purpose are not yet optimized. Therefore, we sought to define the mixture of early-acting cytokines and TPO that would promote the expansion of MK progenitors over other lineages and result in overall better MK expansion and platelet yields. CB CD34(+)-enriched cells were cultured in serum-free medium for 17 days in presence of TPO alone or in various combinations with early-acting cytokines used at different concentrations and addition times. MK expansion and polyploidy and platelet production were monitored by flow cytometry analysis using specific surface markers (CD41 and CD42b) and propidium iodide labeling. Our results showed that the use of high concentrations of stem cell factor (SCF) and Flt-3 ligand (FL) in early CB TPO-supplemented cultures was more favorable to monocytic and granulocytic cell expansion. However, we observed that their presence in limiting amounts was required for the preferential expansion of MK progenitors. The addition of SCF, FL, TPO, and interleukin-6 (IL-6) at high concentrations in secondary cultures of these expanded MKs resulted in optimal MK proportion (approximately 25% of MKs) and expansion (>300 MK per seeded cell), highest proportions of polyploid MKs (22% of mature MKs > or = 8N), and best platelet yields. Our results indicate that TPO-induced MK progenitors are more sensitive to early-acting cytokines than non-MK cells. We propose that MKs generated in the optimized conditions, in combination with immature stem/progenitor cells, could prove useful for the short-term platelet recovery following CB transplantation.     

Human megakaryocytes. V. Changes in the phenotypic profile of differentiating megakaryocytes

Human megakaryocytes were studied for phenotypic changes occurring throughout differentiation using a panel of monoclonal antibodies raised against marrow megakaryocytes and blood platelets. 11 monoclonal antibody preparations were selected for restricted specificity against megakaryocytes and/or platelets after screening by immunofluorescence, complement-mediated cytolysis, and solid phase enzyme-linked immunosorbent assay. The expression of the cellular epitopes recognized by these reagents enabled the identification of three levels of megakaryocyte maturation characterized by distinct immunologic phenotypes. Based upon their reactivities against megakaryocytic cells at different ontogenetic levels, monoclonal antibodies were operationally categorized into three groups. Group A consisted of six different monoclonal antibodies that recognized antigens on the colony-forming unit-megakaryocyte (CFU-Mk), in vitro grown colony megakaryocytes, and early immature marrow megakaryocytes, only, and did not detect their respective epitopes on either mature megakaryocytes or platelets. A monoclonal antibody categorized in group B detected a cell antigen expressed by megakaryocytic cells at all maturational levels, but which is lost or suppressed during terminal differentiation and is not expressed on blood platelets. Group C included four different monoclonal antibodies raised against platelets that recognized antigenic determinants expressed on the CFU-Mk, colony megakaryocytes, early and mature megakaryocytes, and platelets. Three group C monoclonal antibodies (PC-1, PC-3, and PC-4) were specific for platelet glycoprotein IIb/IIIa. Additionally, group C monoclonal antibody PC-2 was unique in that it showed partial reactivity against the clonable progenitor for the erythroid series (BFU-E). Recognition of discrete phenotypic changes in differentiating megakaryocytes will enable multiparameter analyses of these cells as well as the study of factors regulating the dynamics of megakaryocytopoiesis in health and disease.     

Therapeutic cytokine stimulation of thrombocytopoiesis

Endogenous thrombopoietin (TPO) stimulates platelet production by inducing dose-dependent megakaryocyte development from early marrow hematopoietic progenitors and subsequent proliferation and endoreduplication. Recombinant human (rHu) TPO or pegylated recombinant human megakaryocyte growth and development factor (PEG-rHu MGDF) produce log-linear responses in experimental animals and humans when administered over the dose range of 0.05-25 micrograms/kg/day with respect to peak peripheral platelet counts (or peripheral platelet mass turnover) and marrow megakaryocyte volume, ploidy, number and mass. Other cytokines stimulating megakaryocytopoiesis in various species using different dosing regimens include Interleukin 1 (IL-1), Interleukin 3 (IL-3), Interleukin 6 (IL-6), Interleukin 11 (IL-11), stem cell factor (SCF), granulocytemacrophage colony stimulating factor, (GM-CSF), fusion proteins, such as promegapoietin, and a peptide agonist of TPO receptor. Whereas neither rHuTPO nor PEG-rHuMGDF induce platelet aggregation in vitro, they transiently enhance aggregatory responsiveness of platelets to physiologic agonists from several different experimental animals both in vitro and ex vivo. However, platelet recruitment into forming thrombus is not augmented by these agents when evaluated in quantitative rabbit or baboon models of platelet-dependent thrombus formation, except for the effect of platelet concentration per se. These findings indicate that appropriate dosing of these agents following marrow suppression prevents thrombocytopenia without increasing the risk of platelet-dependent thrombo-occlusive complications.     

Increase in endogenous thrombopoietin in healthy donors after automated plateletpheresis

BACKGROUND: Thrombopoietin (TPO) is a key cytokine involved in the regulation of megakaryocytopoiesis and platelet production. The aim of the present study was to test whether platelet donation is associated with changes in the serum TPO levels in healthy donors undergoing plateletpheresis. STUDY DESIGN AND METHODS: The study group consisted of 23 healthy donors undergoing single-donor plateletpheresis for the first time. Serum TPO levels and platelet counts were determined before platelet collection, at the end of apheresis, and for 4 days thereafter. Serum TPO levels were determined by a TPO-specific enzyme- linked immunosorbent assay. RESULTS: In relationship to platelet donation, serum TPO levels showed a temporary increase from baseline levels of 69.2 +/? 7.1 pg per mL to 117 +/? 6.8 pg per mL 2 days after plateletpheresis (p < 0.05). Further evaluation revealed a decline in serum TPO levels as platelet counts increased. Female donors showed a delayed normalization of circulating platelet numbers and serum TPO levels as compared to male donors. There was no significant correlation between serum TPO levels and the absolute platelet number during normalization of the donors' platelet counts after plateletpheresis. CONCLUSION: Single-donor plateletpheresis results in a temporary increase in serum TPO levels in healthy platelet donors, which may be part of a compensatory response-boosting megakaryocytopoiesis after platelet collection.     

Regulation of polymorphonuclear cell activation by thrombopoietin.

Thrombopoietin (TPO) regulates early and late stages of platelet formation as well as platelet activation. TPO exerts its effects by binding to the receptor, encoded by the protooncogene c-mpl, that is expressed in a large number of cells of hematopoietic origin. In this study, we evaluated the expression of c-Mpl and the effects of TPO on human polymorphonuclear cells (PMN). We demonstrate that PMN express the TPO receptor c-Mpl and that TPO induces STAT1 tyrosine phosphorylation and the formation of a serum inducible element complex containing STAT1. The analysis of biological effects of TPO on PMN demonstrated that TPO, at concentrations of 1-10 ng/ml, primes the response of PMN to n-formyl-met-leu-phe (FMLP) by inducing an early oxidative burst. TPO-induced priming on FMLP-stimulated PMN was also detected on the tyrosine phosphorylation of a protein with a molecular mass of approximately 28 kD. Moreover, we demonstrated that TPO by itself was able to stimulate, at doses ranging from 0.05 to 10 ng/ml, early release and delayed synthesis of interleukin 8 (IL-8). Thus, our data indicate that, in addition to sustaining megakaryocytopoiesis, TPO may have an important role in regulating PMN activation.     

Megakaryocytes derived from human embryonic stem cells: a genetically tractable system to study megakaryocytopoiesis and integrin function

BACKGROUND: The platelet fibrinogen receptor, a heterodimer consisting of integrin subunits alpha(IIb) and beta(3), is required for platelet aggregation, spreading, and hemostasis. Platelet agonists such as thrombin and adenosine diphosphate (ADP) lead to the activation of alpha(IIb)beta(3), thereby enhancing its affinity and avidity for binding fibrinogen (inside-out signaling). Furthermore, fibrinogen binding to alpha(IIb)beta(3) triggers cytoskeletal changes and granule release (outside-in signaling). AIM: Genetic approaches to characterize the molecular pathways involved in alpha(IIb)beta(3) signaling are not possible with anucleate blood platelets. Therefore, we have established an OP9 stromal cell co-culture system to generate megakaryocytes from human embryonic stem cells (hESCs). RESULTS: alpha(IIb)beta(3) activation, measured by soluble fibrinogen binding to hESC-derived megakaryocytes, /GPIbalpha(+) cells, is readily detectable following stimulation with known platelet agonists. Dose-response curves for peptide agonists specific for the two platelet thrombin receptors, protease-activated receptor 1 (PAR1) and PAR4, show a relative responsiveness that mirrors that of human platelets, and sub-maximal ADP responses are augmented by epinephrine. Moreover, hESC-derived megakaryocytes undergo lamellipodia formation, actin filament assembly, and vinculin localization at focal adhesions when plated on a fibrinogen-coated surface, characteristic of alpha(IIb)beta(3) outside-in signaling. Undifferentiated hESCs genetically modified by lentiviral infection can be cloned and maintained in an undifferentiated state and then differentiated into megakaryocytes capable of alpha(IIb)beta(3) activation. CONCLUSION: Using hESCs, we have developed a renewable source of human megakaryocytes, and a genetically tractable system for studying megakaryocytopoiesis and alpha(IIb)beta(3) signaling in the native cellular environment.