Wnt信号通路调控造血干细胞自我更新的研究进展

造血干细胞是一类具有自我更新能力和分化成所有种类血细胞能力的多潜能干细胞,该类群细胞来源于中胚层细胞,最终定植于骨髓中。造血干细胞的增殖分化由多个信号通路精细调控,其中,Wnt信号通路在调控其自我更新的过程中具有重要作用。该文综述了多年来关于Wnt信号通路在脊椎动物(小鼠)造血干细胞自我更新中的研究,有助于了解Wnt信号通路的作用机制,也有望为改善体外增殖造血干细胞的效果提供理论支持。     

Wnt/β-catenin信号通路与癌症发生发展及其免疫治疗

经典的Wnt/β-catenin信号通路参与调控机体的多种生物学功能,包括干细胞自我更新,细胞的增殖、分化、凋亡以及胚胎早期发育和组织再生等,与癌症发生发展紧密相关.此外,该信号通路在胸腺T细胞的发育和分化过程中发挥重要作用,影响抗肿瘤免疫效应的多个环节.异常激活的Wnt/β-catenin信号通路可诱导恶性肿瘤的形成...     

骨髓间充质干细胞向肝细胞分化的相关细胞因子及信号通路的研究进展

骨髓干细胞包括造血干细胞（HSCs）和间充质干细胞（MSCs）,骨髓间充质干细胞（BMSCs）是一类具有自我更新、增殖和多向分化能力的细胞,具有不对称分裂和无限增殖的特点。在肝细胞生长因子（HGF）的作用下,BMSCs可以分化为肝细胞,参与诱导这一分化过程的相关信号通路包括NF-kB信号通路、Notch信号通路、MAPK信号通路、Wnt信号通路和STAT3信号通路。文章主要就BMSCs分化为肝细胞的相关信号通路进行了综述。     

经典饲养层细胞Wnt表达的差异及其对人胚胎干细胞Wnt/β-Catenin信号通路的影响

目的:研究比较三种经典饲养层体系使用的成纤维细胞中Wnt基因的表达,及其对共培养的人胚胎干细胞的影响。方法:PCR验证19种Wnt基因在三种不同来源饲养层细胞中的表达情况,q PCR验证各组共培养人胚胎干细胞的Wnt/β-Catenin信号通路相关基因表达水平,流式检测其在不同密度饲养层条件下的增殖分化情况。结果:在全部19种Wnt基因(Wnt1,Wnt2,Wnt2b,Wnt3,Wnt3a,Wnt4,Wnt5a,Wnt5b,Wnt6,Wnt7a,Wnt7b,Wnt8a,Wnt8b,Wnt9a,Wnt9b,Wnt10a,Wnt10b,Wnt11,Wnt16)的表达检测中,昆明白小鼠来源饲养层细胞表达其中的16种,ICR小鼠来源饲养层细胞表达其中的10种,人成纤维细胞来源饲养层细胞表达其中的10种;增加饲养层细胞密度能够不同程度活化Wnt/β-Catenin信号通路下游基因的表达,并激活人胚胎干细胞中的负反馈机制;高密度小鼠饲养层条件促进人胚胎干细胞的分化,高密度人饲养层条件促进人胚胎干细胞的增殖和分化。结论:不同经典饲养层体系提供的Wnt环境不同,其培养的人胚胎干细胞状态也有差异。     

Zfx基因与干细胞自我更新

干细胞具有自我更新保持不分化状态的特性,不同的干细胞具有不同的自我更新机制. Zfx基因(zinc fin ger-X gene)在部分胚胎干细胞和造血干细胞中高表达,该基因高表达有利于胚胎干细胞和造血干细胞自我更新; Zfx基因表达不足或缺乏的胚胎干细胞和造血干细胞自我更新的能力下降,细胞凋亡明显增加.在胚胎干细胞和造血干细胞中发现一些Zfx基因直接调控的靶基因,Zfx 基因可能是控制各种干细胞自我更新的共同的分子机制. Zfx基因表达不足不影响胚胎干细胞和造血干细胞的分化,缺乏 Zfx基因的胚胎干细胞和造血干细胞能够正常分化为各自的功能细胞.     

人胚胎干细胞和拟胚体基因表达谱的初步分析

利用人类全基因组Affymetrix芯片检测人胚胎干细胞与其自发分化7d的拟胚体之间的差异表达基因.结果显示:与未分化的人胚胎干细胞相比.在分化7d的拟胚体中表达下调2倍及以上的已知和未知基因共有1100个,表达上调2倍及以上的已知或未知基因共有2283个.利用Gostat对这些差异表达基因进行功能分析,发现它们分别与细胞的生物代谢过程、信号传导通路、系统发育、细胞分化、分子功能及亚细胞组分相关.胚胎干细胞具有自我更新能力,是研究早期胚胎发育理想的细胞模型,因此对差异表达基因的功能研究有助于了解维持人胚胎干细胞自我更新的分子机制以及胚胎发育早期的分子事件.     

同源域蛋白Nanog与胚胎干细胞的自我更新研究进展

胚胎干细胞作为一种具有自我更新能力的细胞,可以在体外无限对称性分裂,同时保持未分化状态,具有向各种类型细胞分化的潜能.基于这一特性,胚胎干细胞（embryonic stem cell,ES细胞）有着极其广阔的应用前景。维持ES细胞自我更新的机制至今尚未阐明,推测ES细胞的自我更新机制是一个包括细胞外刺激、细胞内多种因子共同参与的复杂的网络调节系统。近年来发现同源域蛋白Nanog在这个网络调节系统中处于中心地位,对ES细胞自我更新的维持起着关键作用。本文就近年来关于Nanog在ES细胞自我更新维持中的作用,以及它与其他信号通路之间的对话,阐明ES细胞自我更新的维持机制。     

针对肿瘤干细胞的抗体靶向治疗——靶向部分信号通路及细胞表面标志分子

肿瘤干细胞是指肿瘤细胞群体中的未分化细胞,能够自我更新及无限增殖;通常具有正常干细胞样的多潜能性,可以分化产生异质性的肿瘤细胞及组织,对于传统的化疗药物具有耐药性。肿瘤干细胞与正常干细胞有一定的差异,如某些信号通路异常活化、细胞表面表达特异的分子等。针对肿瘤干细胞的这些特性,科学家们提出新的肿瘤治疗策略,即通过设计特异的抗体药物靶向信号通路或者细胞表面分子等,从根源上杀死肿瘤起始细胞,从而达到彻底治愈恶性肿瘤的目的。该文介绍了针对不同信号通路(如Notch和Wnt)或肿瘤细胞表面标志分子(如Ep CAM和CD44等)的抗体药物,并且探讨了抗体药物的优点以及面临的问题。     

Wnt3a诱导小鼠胚胎干细胞向心肌细胞分化的研究

目的：研究Wnt3a在诱导小鼠胚胎干细胞心肌细胞分化中的作用和原理。方法：设计不同浓度,不同成分的Wnt3a条件培养基对小鼠胚胎干细胞诱导分化,对分化细胞进行形态学鉴定,通过免疫细胞化学检测心肌肌钙蛋白-T（cTnT）的表达,通过RT．PCR检测肌球蛋白重链（ot．MHC）和肌球蛋白轻链（MLC．2v）的表达。结果：Wnt3a诱导小鼠胚胎干细胞分化为心肌样细胞,分化细胞具有自动收缩性,免疫细胞化学检测心肌肌钙蛋白．T（cTllT）表达阳性,RT．PCR检测肌球蛋白重链（d—MHC）和肌球蛋白轻链（MLC-2v）表达阳性。经典Wnt信号途径的抑制剂Frizzled一8／Fc,能够抑制Wnt3a的诱导分化作用。结论：Wnt3a通过经典Wnt信号途径诱导小鼠胚胎干细胞向心肌细胞分化。     

巨噬细胞与Wnt通路在肿瘤发生发展中的作用

巨噬细胞作为机体固有免疫的重要成员,具有高度异质性,在肿瘤发生发展过程中的多个方面发挥重要作用。Wnt信号通路分子广泛表达于胚胎和成年个体组织,在胚胎/成体干细胞分化、发育和功能调控中发挥重要作用,而且参与多种肿瘤的发生发展过程。近年来越来越多研究表明,Wnt信号通路参与调控巨噬细胞的分化及功能。本文就巨噬细胞与Wnt信号通路对肿瘤发生发展作用的研究进展作一综述。     

Construction of a cultivation system of a yeast single cell in a cell chip microchamber

A novel single cell screening system was constructed using a yeast cell chip in combination with the yeast cell surface engineering [NanoBiotechnology 2005, 1, 105-111]. Enzymes or functional proteins displayed on a yeast cell surface can be used as a protein cluster. To achieve high-throughput screening of protein libraries on the cell surface, a catalytic reaction by a single cell-surface-engineered yeast cell was successfully carried out in the microchamber on the yeast cell chip. After screening, to replicate a target cell for use in measuring of activity, DNA sequencing, and preservation, a novel single cell cultivation system in the yeast cell chip was constructed. To avoid damage of the rapid dry up of medium in the microchamber array, the yeast cell chip was modified with a protection sheet, so that the modified chip was like a micro-culture tank constructed on the yeast cell chip microchamber. As a result, single yeast cell cultivation in the yeast cell chip microchamber was observed, and the modified yeast cell chip was evaluated to be good for a single cell selection. The improvement showed that the single cell screening system coupled with the single cell cultivation using the modified yeast cell chip may be superior to that by a cell sorter for the isolation of a target cell and its practical use.     

Manipulation of leaf shape by modulation of cell division

The role of cell division as a causal element in plant morphogenesis is debatable, with accumulating evidence supporting the action of cell division-independent mechanisms. To directly test the morphogenic function of cell division, we have utilised a microinduction technique to locally and transiently manipulate the expression in transgenic plants of two genes encoding putative effectors of the cell cycle, a tobacco A-type cyclin and a yeast cdc25. The results show that local expression of these genes leads to modulation of cell division patterns. Moreover, whereas altered cell division in the apical meristem had no influence on organogenesis, local induction of cell proliferation on the flanks of young leaf primordia led to a dramatic change in lamina development and, thus, leaf shape. These data indicate that the role of cell division in plant morphogenesis is context dependent and identify cell division in the leaf primordium as a potential target for factors regulating leaf shape.     

Rheological characteristics of cell suspension and cell culture of Perilla frutescens

Physical properties such as viscosity, fluid dynamic behavior of cell suspension, and size distribution of cell aggregates of a plant, Perilla frustescens, cultured in a liquid medium were studied. As a result of investigations using cells harvester after 12 days of cultivation in a flask, it was found that the apparent viscosity of the cell suspension did not change with any variation of cell concentration below 5 g dry cell/L but markedly increased when the cell concentration increased over 12.8 g dry cell/L. The cell suspension exhibited the characteristics of a Bingham plastic fluid with a small yield stres. The size of cell aggregates in the range 74 to 500 mum did not influence the rheological characteristics of the cell suspension. The rheological characteristics of cultivation mixtures of P. frutescens cultivated in a flask and in a bioreactor were also investigated. The results showed that the flow characteristics of the cell culture could be described by a Bingham plastic model. At the later stage of cultivation, the apparent viscosity increased steadily, even though the biomass concentration (by dry weight) decreased, due to the increase of individual cell size. (c) 1992 John Wiley & Sons, Inc.     

樟子松大孢子的发生和雌配子体的形成过程

樟子松大孢子母细胞经一系列变化,发育成雌配子体。在哈尔滨地区樟子松大孢子母细胞于每年6月8～14日形成,接着进行减数分裂,于6月16～20日形成大孢子。随着大孢子核的分裂,进入游离核时期,并于次年5月28日～6月4日形成细胞壁,幼雌配子体中出现颈卵器原始细胞,它分裂一次形成颈细胞和中央细胞。6月7～9日中央细胞分裂成卵细胞和腹沟细胞,6月13～15日颈卵器发育成熟。成熟的颈卵器含有颈细胞、腹沟细胞和卵细胞,但颈细胞和腹沟细胞已经退化。     

Effect of the distance between adherent mesenchymal stem cell and the focus of irradiation of femtosecond laser on cell replication capacity

The effect of femtosecond laser irradiation on adherent mesenchymal stem cell was investigated with the aim to develop a novel noninvasive cell purification system. A single mesenchymal stem cell was irradiated with a femtosecond laser on the center of the cell using several energy values and the cell lost its replication capacity with one time irradiation with an energy of 2.0 μJ. Besides at a neighbor point in the major axis, when irradiated in the minor axis at a distance shorter than 10 μm, the cell stopped its replication capacity. The accumulation effect of cell damage caused by multiple laser shots at a neighbor point in the minor axis was correlated with the critical distance at which the cell lost its replication capacity. Finally, a novel equation of laser cell damage as a function of laser pulse energy and laser shot number is proposed.     

东亚飞蝗Locusta migratoria manilensis（Mey．）膝下器中具橛感器的附属细胞和附属结构的超微结构

东亚飞蝗膝下器的具橛感器主要由三类细胞组成．即：感觉细胞、感橛细胞和冠细胞。感觉细胞为具橛感器的主要结构和功能细胞,其超微结构已在其他的文章中描述。感橛细胞是具橛感器的主要支持细胞,从近端到远端依次与神经胶质细胞、感觉细胞的远端树突部分和感觉纤毛部以及顶端细胞外结构——冠、冠细胞直接接触．感橛细胞内最明显的结构为感概,另外,感橛细胞质被高度“空化”。冠细胞紧密包围着感橛细胞和冠,冠细胞中含有大量的纵行微管．并将整个具橛感器连接到体壁上。     

Influence of individual cell motility on the 2D front roughness dynamics of tumour cell colonies

The dynamics of in situ 2D HeLa cell quasi-linear and quasi-radial colony fronts in a standard culture medium is investigated. For quasi-radial colonies, as the cell population increased, a kinetic transition from an exponential to a constant front average velocity regime was observed. Special attention was paid to individual cell motility evolution under constant average colony front velocity looking for its impact on the dynamics of the 2D colony front roughness. From the directionalities and velocity components of cell trajectories in colonies with different cell populations, the influence of both local cell density and cell crowding effects on individual cell motility was determined. The average dynamic behaviour of individual cells in the colony and its dependence on both local spatio-temporal heterogeneities and growth geometry suggested that cell motion undergoes under a concerted cell migration mechanism, in which both a limiting random walk-like and a limiting ballistic-like contribution were involved. These results were interesting to infer how biased cell trajectories influenced both the 2D colony spreading dynamics and the front roughness characteristics by local biased contributions to individual cell motion. These data are consistent with previous experimental and theoretical cell colony spreading data and provide additional evidence of the validity of the Kardar-Parisi-Zhang equation, within a certain range of time and colony front size, for describing the dynamics of 2D colony front roughness.     

Biophysical factors in the regulation of asymmetric division of stem cells

Stem cells are a promising cell source for regenerative medicine due to their characteristics of self‐renewal and differentiation. The intricate balance between these two cell fates is maintained by precisely controlled symmetric and asymmetric cell divisions. Asymmetric division has a fundamental importance in maintaining tissue homeostasis and in the development of multi‐cellular organisms. For example, during development, asymmetric cell divisions are responsible for the formation of the body axis. Mechanistically, mitotic spindle dynamics determine the assembly and separation of chromosomes and regulate the orientation of cell division. Interestingly, symmetric and asymmetric cell division is not mutually exclusive and a range of factors are involved in such cell‐fate decisions, the measurement of which can provide efficient and reliable information on the regenerative potential of a cell. The balance between self‐renewal and differentiation in stem cells is controlled by various biophysical and biochemical cues. Although the role of biochemical factors in asymmetric stem cell division has been widely studied, the effect of biophysical cues in stem‐cell self‐renewal is not comprehensively understood. Herein, we review the biological relevance of stem‐cell asymmetric division to regenerative medicine and discuss the influences of various intrinsic and extrinsic biophysical cues in stem‐cell self‐renewal. This review particularly aims to inform the clinical translation of efforts to control the self‐renewal ability of stem cells through the tuning of various biophysical cues.     

Ultrastructural and Cytochemical Study on Mature Pollen of Pinus tabulaeformis

The pollen of Pinus tabulaeformis Cart. comprised two prothallial cells, a generative cell and a tube cell which degenerated at pollen maturation. The generative cell had its own cell wall, seperating from the intine of pollen, but with its side wall attached to the infine. Cytoplasmic channels were present on the side of the generative cell wall, which faced to the tube cell cytoplasm. The generative cell differed conspicuously from the tube cell. The main differences include: ( 1 ) The chromatin in the generative cell nucleus was condensed, but was dispersed and had numerous nueleare pores in the tube cell nucleus; (2)There was no microbody in the generative cell but many microbodies were present in the tube cell cytoplasm; (3)More inclusions were present in the tube cell than in the generative cell. Both the generative cell and the tube cells contained lipid bodies and amyloplasts in the cytoplasm, but there were more amyloplasts in the former. The tube cell also contained a few proteins which was absent in the generative cell. In addition, there were numerous mitochondria, polyribosomes, and a few endoplasmic reticulums and dictyosomes in the generative and tube cells. DAPI staining demonstrated numerous cytoplasmic DNA in both generative cell and tube cell. The mode of cytoplasmic inheritance, and the composition, structure and the nature of the pollen wall of P. tabulaefonnis are also discussed in this paper.     

Three-Dimensional Numerical Model of Cell Morphology during Migration in Multi-Signaling Substrates

Cell Migration associated with cell shape changes are of central importance in many biological processes ranging from morphogenesis to metastatic cancer cells. Cell movement is a result of cyclic changes of cell morphology due to effective forces on cell body, leading to periodic fluctuations of the cell length and cell membrane area. It is well-known that the cell can be guided by different effective stimuli such as mechanotaxis, thermotaxis, chemotaxis and/or electrotaxis. Regulation of intracellular mechanics and cell’s physical interaction with its substrate rely on control of cell shape during cell migration. In this notion, it is essential to understand how each natural or external stimulus may affect the cell behavior. Therefore, a three-dimensional (3D) computational model is here developed to analyze a free mode of cell shape changes during migration in a multi-signaling micro-environment. This model is based on previous models that are presented by the same authors to study cell migration with a constant spherical cell shape in a multi-signaling substrates and mechanotaxis effect on cell morphology. Using the finite element discrete methodology, the cell is represented by a group of finite elements. The cell motion is modeled by equilibrium of effective forces on cell body such as traction, protrusion, electrostatic and drag forces, where the cell traction force is a function of the cell internal deformations. To study cell behavior in the presence of different stimuli, the model has been employed in different numerical cases. Our findings, which are qualitatively consistent with well-known related experimental observations, indicate that adding a new stimulus to the cell substrate pushes the cell to migrate more directionally in more elongated form towards the more effective stimuli. For instance, the presence of thermotaxis, chemotaxis and electrotaxis can further move the cell centroid towards the corresponding stimulus, respectively, diminishing the mechanotaxis effect. Besides, the stronger stimulus imposes a greater cell elongation and more cell membrane area. The present model not only provides new insights into cell morphology in a multi-signaling micro-environment but also enables us to investigate in more precise way the cell migration in the presence of different stimuli.