精原干细胞自我更新和分化的调控

精原干细胞（spermatogonial stem cells,SSCs）是体内自然状态下惟一能将遗传信息传至子代的成体干细胞,它们能通过维持自我更新和分化的稳定从而保证雄性生命过程中精子发生的持续进行。了解SSCs自我更新和分化的调节机制有助于阐明精子发生机理,并为探究其他组织中成体干细胞增殖分化的调节机制提供依据。然而目前对于SSCs自我更新和分化的调控机制所知甚少。SSCs的更新与分化遵循特定模式,受以睾丸支持细胞为主要成分的微环境及各种内分泌因素如胶质细胞源神经营养因子（GDNF）、维生素、Ets转录因子ERM/Etv5等的调控。本文评述了SSCs更新与分化的模式以及上述因素对其更新、分化的调控,探讨了其中可能涉及的信号通路,以期为本领域及其他成体干细胞相关研究提供借鉴。     

哺乳动物精原干细胞的分子标记及调控

精原干细胞(spermatogonial stem cells,SSCs)是一群生活在睾丸特殊微环境中并能自我更新和具有多向分化潜能的细胞,是精子发生的基础。近年来,通过对SSCs表面的α6-和β1-整合素、CD9、GFRA1等主要标记分子,以及对GDNF、Plzf、泛素、LIF等决定SSCs自我更新和分化的多种细胞因子和基因的研究发现,目前在SSCs的分离、鉴定和生物学特性方面已获得新的成果。本文简述了目前哺乳动物SSCs主要的标记分子及自我更新与分化的调控机理,以期为该领域及其他干细胞研究提供一定的借鉴。     

哺乳动物精原干细胞的增殖分化及其移植技术的应用

精原干细胞(spermatogonial stem cells,SSCs)是指位于睾丸生精小管基膜上既能自我更新以维持自身群体数量恒定,又能定向分化形成精母细胞,最终形成精子的一类成体干细胞.鉴于其独具的生物学特性,SSCs的研究在干细胞生物学、医学、畜牧业等领域均具有重要意义.通过其建立转基因动物模型,对研究精子的发生机制、重建不育个体的生精功能等都有着重要意义.综述了哺乳动物SSCs的形态特性,增殖分化特性及其调控因素,简述了SSCs移植技术的应用.     

精原干细胞微环境研究进展

精原干细胞(spermatogonia stem cells, SSCs)是一类在睾丸中具有长期自我更新和分化潜能的生殖细胞(germ cells, GCs),即位于基底膜上的组织干细胞,其自我更新和分化受到周围微环境的调控。近年来对SSCs的研究取得了一系列重要进展,为临床治疗部分男性不育患者带来了曙光。其中,微环境对SSCs的调节功能的研究尤为重要,微环境负责整合不同类型的细胞成分、细胞外基质、细胞外调节分子及激素等对SSCs的作用,从而调节SSCs命运。关于SSCs微环境的研究已开始逐步成为干细胞研究的主要内容之一。本文主要对小鼠(Mus musculus)SSCs微环境的细胞组成、调控因子以及特点等研究现状进行了综述,为深入研究SSCs微环境的结构和功能提供背景资料,希望在未来能够通过多种研究模式复用,发现更为丰富的细胞表型和微环境因子。     

精原干细胞的生物学特性

精原干细胞(spermatogonialstemcells,SSCs)是雄性生殖系干细胞,位于睾丸曲细精管基膜上,既具有自我更新潜能,又具有定向分化潜能,是自然状态下出生后动物体内在整个生命期间进行自我更新并能将基因传递至子代的唯一成体干细胞。自SSCs移植技术建立以来,有关其分离、鉴定、培养、冻存、转基因操作及移植等方面均已取得长足进步,使人们对其生物学特性有了更深入的了解。根据最近的相关进展,系统评述了SSCs的相关生物学特性,以期为该领域及其他干细胞研究提供借鉴。     

KnockoutTM SR无血清培养基支持小鼠精原干细胞的短期存活(简报)

精原干细胞(spermatogonial stem cells,SSCs)是睾丸内具有自我复制和分化为精子潜能的干细胞,它的体外培养是精子发生机理研究和制作转基因动物等的新途径[1,2].近几年的研究表明,SSCs在体外的自我增殖需要GDNF(glial cell line-derived neu-rotrophie factor)因子和饲养层细胞等的支持[3-10].并且睾丸支持细胞(Sertoli's cells)和血清都导致培养的SSCs分化[1,6].因此,使用无血清培养基培养高度纯化的SSCs是培养成败的关键之一.     

精原干细胞niche的研究进展

精原干细胞(spermatogonial stem cells,SSCs)是指睾丸内位于曲精细管基膜上既能自我更新维持自身适量恒定,又能定向分化产生精母细胞的一类原始精原细胞。随着干细胞深入的研究,人们发现了一种控制着干细胞可塑性与命运的微环境,此微环境被称为干细胞niche,干细胞niche由niche细胞、细胞外基质、细胞因子等构成。精原干细胞niche是由黏附因子、生长因子、支持细胞、间质细胞以及小管周肌肉细胞组成。大量的研究表明支持细胞在睾丸中是主要的成体细胞,通过分泌可溶性的因子来影响精原干细胞niche的结构与功能,同时支持细胞还能够间接的影响其他的成体细胞。随着年龄的增长使得精原干细胞niche的功能下降。精原干细胞数量以及精原干细胞niche为我们研究组织特异性干细胞生物学以及保持再生组织平衡提供了很宝贵的线索,精原干细胞对于保持组织的自我更新具有很重要的作用,并且受到人们大量的关注,然而精原干细胞niche也起到很重要的作用,它为治疗一些疾病提供新途径.本文将综述精原干细胞niche及其变化对精原干细胞功能调节的相关研究进展。     

过表达水牛睾丸FGF2基因维持水牛精原细胞的体外培养

水牛睾丸支持细胞(Sertoli cells)是环绕在精原干细胞(spermatogonial stem cells,SSCs)周围的一类体细胞,为SSCs增殖提供物理支持及稳定的环境,同时参与血睾屏障形成.支持细胞可分泌FGF2,从而提高SSCs存活和增殖.至今为止,水牛SSCs培养体系仍然面临许多挑战,推测内源性的...     

胶质细胞源性神经营养因子引发精原干细胞自我更新的信号通路

胶质细胞源性神经营养因子(glial cell line-derived neurotrophic factor,GDNF)是TGF-β超家族的一个相关成员。哺乳动物睾丸曲细精管内支持细胞分泌的GDNF,能促进精原干细胞(spermatogonial stem cells,SSCs)的自我更新与增殖。SSCs去分化诱导产生的多能干细胞已被广泛应用于再生医学领域,且SSCs在制作转基因动物、男性不育治疗和体外实施精子发生过程等方面,具有极大的应用价值。所以,GDNF引发SSCs自我更新的作用机理非常值得探索。通过对GDNF引发SSCs自我更新的信号通路进行系统梳理,我们发现了如下的作用过程:GDNF与GFR-α1特异性结合,活化Ret蛋白酪氨酸激酶,随后激活Ras/ERK1/2、PI3K-Akt和SFK信号通路,促进SSCs的自我更新;同时,在该过程中还存在信号通路间的交联对话现象。     

山羊精原干细胞的鉴定及培养体系优化的研究

该研究优化了山羊精原干细胞(goat spermatogonial stem cells,g SSCs)培养体系,使山羊精原干细胞能在体外长期培养,维持自我更新的能力并保持未分化状态。取3~5月龄山羊睾丸,采用两步酶消法结合差速贴壁方法得到山羊精原干细胞悬液,分别通过形态学观察、碱性磷酸酶(alkaline phosphatase,AKP)染色、特异基因表达及蛋白质水平的分析对培养的细胞进行鉴定;并以山羊睾丸支持细胞(goat sertoli cells,g SCs)、小鼠胚胎成纤维细胞(mouse embryonic fibroblasts,MEFs)和层黏连蛋白(laminin,L)为饲养层,观察饲养层对山羊精原干细胞体外增殖的影响。结果表明,山羊精原干细胞体外增殖形成克隆簇,AKP染色呈阳性。经RT-PCR检测,Oct-4、C-myc、Cyclin D1、Ngn3和TERT等干细胞特异基因均有表达。细胞免疫组化结果显示,Oct-4、SSEA-1、α6-integrin、Vasa和Thy-1蛋白质呈阳性。克隆簇统计显示,在山羊睾丸支持细胞上形成的山羊精原干细胞(goat spermatogonial stem cells,g SSCs)克隆数与其他两组比较差异显著(P0.05)。山羊睾丸支持细胞饲养层上的精原干细胞可在体外传3~4代,培养时间为2个月。结果证明,通过两步酶消法和差速贴壁法可以分离获得山羊精原干细胞,且山羊睾丸支持细胞能够促进g SSCs的增殖。     

颌下腺导管细胞与胶原海绵细胞相容性的实验研究

为探讨胶原海绵对颌下腺 (submandibulargland ,SMG)导管细胞的细胞相容性 ,采用HE染色光镜观察及免疫组化观察SMG导管细胞接种于胶原海绵后 ,细胞的生长情况。光镜下可见接种后第 1d细胞数量较少 ,分散于胶原海绵支架中间 ,第 7d细胞数量明显增加 ,免疫组织化学染色抗IV型胶原抗体染色呈阳性 ,说明细胞与支架材料之间已经有细胞外基质产生。胶原海绵具有良好的细胞相容性 ,是一种理想的支架材料。与胶原海绵复合培养 ,颌下腺导管细胞仍可保持良好的增殖能力。     

Determination of Mammalian Cell Counts,Cell Size and Cell Health Using the Moxi Z Mini Automated Cell Counter

Particle and cell counting is used for a variety of applications including routine cell culture, hematological analysis, and industrial controls^1-5. A critical breakthrough in cell/particle counting technologies was the development of the Coulter technique by Wallace Coulter over 50 years ago. The technique involves the application of an electric field across a micron-sized aperture and hydrodynamically focusing single particles through the aperture. The resulting occlusion of the aperture by the particles yields a measurable change in electric impedance that can be directly and precisely correlated to cell size/volume. The recognition of the approach as the benchmark in cell/particle counting stems from the extraordinary precision and accuracy of its particle sizing and counts, particularly as compared to manual and imaging based technologies (accuracies on the order of 98% for Coulter counters versus 75-80% for manual and vision-based systems). This can be attributed to the fact that, unlike imaging-based approaches to cell counting, the Coulter Technique makes a true three-dimensional (3-D) measurement of cells/particles which dramatically reduces count interference from debris and clustering by calculating precise volumetric information about the cells/particles. Overall this provides a means for enumerating and sizing cells in a more accurate, less tedious, less time-consuming, and less subjective means than other counting techniques⁶.Despite the prominence of the Coulter technique in cell counting, its widespread use in routine biological studies has been prohibitive due to the cost and size of traditional instruments. Although a less expensive Coulter-based instrument has been produced, it has limitations as compared to its more expensive counterparts in the correction for "coincidence events" in which two or more cells pass through the aperture and are measured simultaneously. Another limitation with existing Coulter technologies is the lack of metrics on the overall health of cell samples. Consequently, additional techniques must often be used in conjunction with Coulter counting to assess cell viability. This extends experimental setup time and cost since the traditional methods of viability assessment require cell staining and/or use of expensive and cumbersome equipment such as a flow cytometer.The Moxi Z mini automated cell counter, described here, is an ultra-small benchtop instrument that combines the accuracy of the Coulter Principle with a thin-film sensor technology to enable precise sizing and counting of particles ranging from 3-25 microns, depending on the cell counting cassette used. The M type cassette can be used to count particles from with average diameters of 4 - 25 microns (dynamic range 2 - 34 microns), and the Type S cassette can be used to count particles with and average diameter of 3 - 20 microns (dynamic range 2 - 26 microns). Since the system uses a volumetric measurement method, the 4-25 microns corresponds to a cell volume range of 34 - 8,180 fL and the 3 - 20 microns corresponds to a cell volume range of 14 - 4200 fL, which is relevant when non-spherical particles are being measured. To perform mammalian cell counts using the Moxi Z, the cells to be counted are first diluted with ORFLO or similar diluent. A cell counting cassette is inserted into the instrument, and the sample is loaded into the port of the cassette. Thousands of cells are pulled, single-file through a "Cell Sensing Zone" (CSZ) in the thin-film membrane over 8-15 seconds. Following the run, the instrument uses proprietary curve-fitting in conjunction with a proprietary software algorithm to provide coincidence event correction along with an assessment of overall culture health by determining the ratio of the number of cells in the population of interest to the total number of particles. The total particle counts include shrunken and broken down dead cells, as well as other debris and contaminants. The results are presented in histogram format with an automatic curve fit, with gates that can be adjusted manually as needed.Ultimately, the Moxi Z enables counting with a precision and accuracy comparable to a Coulter Z2, the current gold standard, while providing additional culture health information. Furthermore it achieves these results in less time, with a smaller footprint, with significantly easier operation and maintenance, and at a fraction of the cost of comparable technologies.     

Transformations of the Cell Center during Cell Differentiation

A question was posed as to how the multicomponent and polyfunctional organelle dynamically changes during metazoan ontogenesis. The centrosome structure is gradually formed and its functions are switched on during early embryogenesis, one of which is the cell center formation. During cell differentiation, the condition of the cell center and surrounding structures may be different: first, the cell center is quite distinct; second, the cell center is absent due to redistribution of the microtubule organizing centers; third, the cell center disappears due to reversible or irreversible inactivation of the centrosome and other centers of microtubule organization. The assembly of the Golgi complex does not depend directly to the cell center presence. In some cell types, the Golgi complex is topologically associated with the cell center, while in others it exists as individual dictyosomes despite the cell center presence. In some other cell types, the common Golgi complex is assembled without the cell center, but in the presence of microtubules that are formed by noncentrosome centers of microtubule organization. In still others, degradation of both the cell center and the common Golgi complex takes place in the case of centrosome inactivation.     

Determining Cell Number During Cell Culture using the Scepter Cell Counter

Counting cells is often a necessary but tedious step for in vitro cell culture. Consistent cell concentrations ensure experimental reproducibility and accuracy. Cell counts are important for monitoring cell health and proliferation rate, assessing immortalization or transformation, seeding cells for subsequent experiments, transfection or infection, and preparing for cell-based assays. It is important that cell counts be accurate, consistent, and fast, particularly for quantitative measurements of cellular responses.Despite this need for speed and accuracy in cell counting, 71% of 400 researchers surveyed¹ who count cells using a hemocytometer. While hemocytometry is inexpensive, it is laborious and subject to user bias and misuse, which results in inaccurate counts. Hemocytometers are made of special optical glass on which cell suspensions are loaded in specified volumes and counted under a microscope. Sources of errors in hemocytometry include: uneven cell distribution in the sample, too many or too few cells in the sample, subjective decisions as to whether a given cell falls within the defined counting area, contamination of the hemocytometer, user-to-user variation, and variation of hemocytometer filling rate².To alleviate the tedium associated with manual counting, 29% of researchers count cells using automated cell counting devices; these include vision-based counters, systems that detect cells using the Coulter principle, or flow cytometry¹. For most researchers, the main barrier to using an automated system is the price associated with these large benchtop instruments¹.The Scepter cell counter is an automated handheld device that offers the automation and accuracy of Coulter counting at a relatively low cost. The system employs the Coulter principle of impedance-based particle detection³ in a miniaturized format using a combination of analog and digital hardware for sensing, signal processing, data storage, and graphical display. The disposable tip is engineered with a microfabricated, cell- sensing zone that enables discrimination by cell size and cell volume at sub-micron and sub-picoliter resolution. Enhanced with precision liquid-handling channels and electronics, the Scepter cell counter reports cell population statistics graphically displayed as a histogram.     

Cell Physician: Reading Cell Motion

Cell motility is an essential phenomenon in almost all living organisms. It is natural to think that behavioral or shape changes of a cell bear information about the underlying mechanisms that generate these changes. Reading cell motion, namely, understanding the underlying biophysical and mechanochemical processes, is of paramount importance. The mathematical model developed in this paper determines some physical features and material properties of the cells locally through analysis of live cell image sequences and uses this information to make further inferences about the molecular structures, dynamics, and processes within the cells, such as the actin network, microdomains, chemotaxis, adhesion, and retrograde flow. The generality of the principals used in formation of the model ensures its wide applicability to different phenomena at various levels. Based on the model outcomes, we hypothesize a novel biological model for collective biomechanical and molecular mechanism of cell motion.