含光诱导片段定向滑动多肽水凝胶诱导胚胎干细胞的外胚层分化（英文）

由细胞内行为或外源力引起的干细胞龛中存在的机械信号对干细胞的自我恢复和分化等基本功能具有重要影响.然而,关于具有分子机械运动产生的内在机械信号的人工细胞外基质鲜有报道.在此,我们报道了含光诱导片段定向滑动的机械动态水凝胶的合成及其作为人工细胞外基质在调节胚胎干细胞(ESC)分化中的功能.通过引入光笼蔽的半胱氨酸残基调控亲疏水交替多肽的自组装制备机械动态水凝胶.光笼蔽多肽组装体在光照射下转化为热力学非平衡的非笼蔽多肽双分子层,其进一步发生热力学有利的疏水性塌陷转变诱导的片段定向滑动.在机械动态水凝胶上培养鼠胚胎干细胞,该片段定向滑动诱导干细胞向外胚层谱系定向分化.进一步揭示了机械动态水凝胶促进机械转导蛋白YAP进入细胞核,表明其用于ESCs定向分化的潜在机械转导机制.细胞定向分化结果表明了机械动态水凝胶作为潜在的生物材料,有望用于疾病治疗和组织再生.     

英科学家将利用胚胎干细胞3D打印人体器官

<正>据国外媒体报道,科学家离培育重要器官又近一步,不久可能使从人到人的移植成为历史。专家已研发出三维打印技术,可用胚胎干细胞制造人体组织。这种由爱丁堡赫瑞-瓦特大学开发出的方法意味着病入膏肓的病人可轻易获得肝脏、心脏和其他器官。科学家已用这种方法培育出骨髓和皮肤。但他们也开始努力研究可能变成一种新器官的更微妙胚胎细胞结构。他们在实验中用一个可调节"微型阀"制造多层人类胚胎干细胞。改变喷嘴直径可准确控制分配细胞的速度。这些新的打印胚胎细胞保留了变成其他任何细胞类型的能力。     

关于脂联素类药物研发的探讨

脂联素是脂肪细胞分泌的一种内源性生物活性多肽或蛋白质。脂肪细胞来源于胚胎干细胞，胚胎干细胞在多种激素和细胞因子刺激下首先分化为前脂肪细胞，然后进一步分化为成熟的脂肪细胞。干细胞向前脂肪细胞分化的过程目前尚不清楚，前脂肪细胞向成熟脂肪细胞分化的转录因子主要有两大类：     

中枢神经再生材料研究进展

首先介绍了目前中枢神经再生面临的问题和应对策略,然后系统地综述了脑再生和脊髓再生修复材料的发展。研究发现,成人中枢神经系统内存的神经干细胞和具有特定分化方向的前体细胞具有潜在的、巨大的修复功能;生物支架材料与神经干细胞的联合使用能够较好地控制细胞微环境,有望提高细胞移植后的存活状况,促进中枢神经再生。最后,结合现在中枢神经再生的研究热点——神经干细胞,阐述了中枢神经再生材料调控干细胞的研究进展和潜能,为联合应用生物材料与干细胞促进中枢再生提供了参考。     

干细胞研究现状与展望

介绍了人胚胎干细胞的建系与定向诱导分化，以及成年组织来源干细胞的多向分化潜能或分化方向的“可塑性”，并提出了干细胞研究的应用前景和存在的主要问题。     

花鲈胚胎干细胞移植及嵌合体的构建

旨在通过花鲈胚胎干细胞(LJES1)移植构建嵌合体,证实LJES1细胞的体内分化能力和发育全能性.采用脂质体介导法将线性化pCMV-EGFP质粒导入到长期培养的LJES1细胞内,细胞绿色荧光蛋白(GFP)的表达率为5%～10%,以此为供体,通过显微注射方法把20～50个LJES1细胞移植到花鲈囊胚中,共移植囊胚478枚,获得了20枚表达GFP的嵌合体胚胎,其中的15枚胚胎发育成鱼苗.荧光显微观察和PCR检测显示了LJES1细胞可在宿主胚胎内片状嵌合和单细胞分散嵌合,嵌合部位可分布于胚体的三个胚层;同时也证明GFP是一种优良的遗传标记.本实验结果为证实LJES1细胞的发育全能性提供了有力证据.     

表达绿色荧光蛋白基因的花鲈胚胎干细胞株的建立及其体外分化

以带有绿色荧光标记的基因(pCMV-EGFP)为报告基因,用Genejammer、Genejuice和Metafectene三种脂质体介导花鲈胚胎干细胞(LJES1)的基因转移.实验发现,Genejammer介导的细胞转化效率最高,高达27.3%,其余分别为12.1%和5.3%.转移绿色荧光蛋白(GFP)基因的LJES1细胞经过药物筛选和单克隆化培养,获得了表达GFP基因的阳性克隆细胞株,经PCR对GFP阳性细胞株的基因组DNA及提取的RNA扩增,获得了目的条带,证实了GFP基因已经整合到LJES1细胞的基因组中,并获得了正常的表达.通过体外诱导,GFP阳性细胞能够分化为神经细胞、肌肉细胞、成纤维细胞等,用悬滴法培养获得了GFP阳性细胞的拟胚体,证实了经过长期的药物筛选后,LJES1细胞仍然保持着发育的多能性.这一研究,为进一步利用海水鱼类胚胎干细胞进行遗传操作及基因工程的研究提供了方法上的探索.     

院士风采

姚鑫 实验生物学、肿瘤生物学家。江苏常熟人。1937年毕业于浙江大学生物系。1949年获英国爱丁堡大学哲学博士学位。中国科学院上海细胞生物学研究所研究员。从事实验肝癌等研究,建立了肝癌模型,发现化学物质诱发肝癌的发生率和肝癌组织学类型的性差别与营养因素有关。他和合作者建立了甲胎蛋白分离提纯和免疫检测方法,首先用于普查,为早期发现肝癌做出了贡献,并发现人体肝癌细胞还具有一种新的膜相关胚胎抗原。组织和主持了抗人肝癌单克隆抗体的研究,在国际上首次获得了具有较好选择性的抗人肝癌单抗,经用放射性点标记后已成功地用于临床肝癌患者定位诊断和治疗。开展对小鼠胚胎肝癌细胞和胚胎干细胞的研究,建立了许多克隆细胞株,进行体外诱导分化和转基因等研究。     

用于组织工程的去细胞化基质材料研究进展

细胞外基质在调节干细胞分化和诱导新的组织器官重建过程中扮演着重要的角色。在体外通过不同去细胞化方法获得不同来源的去细胞化基质材料,并研究它们在组织工程领域的应用,具有重要的理论意义和临床应用价值。总结了不同来源去细胞化基质材料的制备方法,并分析了其在诱导干细胞分化和组织修复过程中的作用,最后探讨了目前去细胞化基质材料存在的问题和面临的挑战。     

用于组织工程的去细胞化基质材料研究进展

细胞外基质在调节干细胞分化和诱导新的组织器官重建过程中扮演着重要的角色。在体外通过不同去细胞化方法获得不同来源的去细胞化基质材料,并研究它们在组织工程领域的应用,具有重要的理论意义和临床应用价值。总结了不同来源去细胞化基质材料的制备方法,并分析了其在诱导干细胞分化和组织修复过程中的作用,最后探讨了目前去细胞化基质材料存在的问题和面临的挑战。     

Self‐Assembling Proteins as High‐Performance Substrates for Embryonic Stem Cell Self‐Renewal

The development of extracellular matrix mimetics that imitate niche stem cell microenvironments and support cell growth for technological applications is intensely pursued. Specifically, mimetics are sought that can enact control over the self‐renewal and directed differentiation of human pluripotent stem cells (hPSCs) for clinical use. Despite considerable progress in the field, a major impediment to the clinical translation of hPSCs is the difficulty and high cost of large‐scale cell production under xeno‐free culture conditions using current matrices. Here, a bioactive, recombinant, protein‐based polymer, termed ZT^Fn, is presented that closely mimics human plasma fibronectin and serves as an economical, xeno‐free, biodegradable, and functionally adaptable cell substrate. The ZT^Fn substrate supports with high performance the propagation and long‐term self‐renewal of human embryonic stem cells while preserving their pluripotency. The ZT^Fn polymer can, therefore, be proposed as an efficient and affordable replacement for fibronectin in clinical grade cell culturing. Further, it can be postulated that the ZT polymer has significant engineering potential for further orthogonal functionalization in complex cell applications.     

Pipette-based Method to Study Embryoid Body Formation Derived from Mouse and Human Pluripotent Stem Cells Partially Recapitulating Early Embryonic Development Under Simulated Microgravity Conditions

The in vitro differentiation of pluripotent stem cells partially recapitulates early in vivo embryonic development. More recently, embryonic development under the influence of microgravity has become a primary focus of space life sciences. In order to integrate the technique of pluripotent stem cell differentiation with simulated microgravity approaches, the 2-D clinostat compatible pipette-based method was experimentally investigated and adapted for investigating stem cell differentiation processes under simulated microgravity conditions. In order to keep residual accelerations as low as possible during clinorotation, while also guaranteeing enough material for further analysis, stem cells were exposed in 1-mL pipettes with a diameter of 3.5 mm. The differentiation of mouse and human pluripotent stem cells inside the pipettes resulted in the formation of embryoid bodies at normal gravity (1 g) after 24 h and 3 days. Differentiation of the mouse pluripotent stem cells on a 2-D pipette-clinostat for 3 days also resulted in the formation of embryoid bodies. Interestingly, the expression of myosin heavy chain was downregulated when cultivation was continued for an additional 7 days at normal gravity. This paper describes the techniques for culturing and differentiation of pluripotent stem cells and exposure to simulated microgravity during culturing or differentiation on a 2-D pipette clinostat. The implementation of these methodologies along with -omics technologies will contribute to understand the mechanisms regulating how microgravity influences early embryonic development.     

Nanotechnology in the regulation of stem cell behavior

Abstract

Stem cells are known for their potential to repair damaged tissues. The adhesion, growth and differentiation of stem cells are likely controlled by the surrounding microenvironment which contains both chemical and physical cues. Physical cues in the microenvironment, for example, nanotopography, were shown to play important roles in stem cell fate decisions. Thus, controlling stem cell behavior by nanoscale topography has become an important issue in stem cell biology. Nanotechnology has emerged as a new exciting field and research from this field has greatly advanced. Nanotechnology allows the manipulation of sophisticated surfaces/scaffolds which can mimic the cellular environment for regulating cellular behaviors. Thus, we summarize recent studies on nanotechnology with applications to stem cell biology, including the regulation of stem cell adhesion, growth, differentiation, tracking and imaging. Understanding the interactions of nanomaterials with stem cells may provide the knowledge to apply to cell–scaffold combinations in tissue engineering and regenerative medicine.     

Fluorescent nanoswitch for monitoring specific pluripotency-related microRNAs of induced pluripotent stem cells: Development of polyethyleneimine-oligonucleotide hybridization probes

The isolation of high-grade (i.e.high-pluripotency) human induced pluripotent stem cells (hiPSCs) is a decisive factor for enhancing the purity of hiPSC populations or differentiation efficiency.A non-invasive imaging system that can monitor microRNA (miRNA) expression provides a useful tool to identify and analyze specific cell populations.However,previous studies on the monitoring/isolation of hiPSCs by miRNA expression have limited hiPSCs' differentiation system owing to long-term incubation with miRNA imaging probe-nanocarriers.Therefore,we focused on monitoring high-grade hiPSCs without influencing the pluripotency of hiPSCs.We reduced nanoparticle transfection time,because hiPSCs are prone to spontaneous differentiation under external factors during incubation.The fluorescent nanoswitch ("ON" with target miRNA),which can be applied for either imaging or sorting specific cells by fluorescence signals,contains an miRNA imaging probe (miP) and a PEI-PEG nanoparticle (miP-P).Consequently,this nanoswitch can sense various endogenous target miRNAs within 30 min in vitro,and demonstrates strong potential for not only imaging but also sorting pluripotent hiPSCs without affecting pluripotency.Moreover,miP-P-treated hiPSCs differentiate well into endothelial cells,indicating that miP-P does not alter the pluripotency of hiPSCs.We envisage that this miRNA imaging system could be valuable for identifying and sorting high-grade hiPSCs for improved practical applications.     

Delayed self-regulation and time-dependent chemical drive leads to novel states in epigenetic landscapes

The epigenetic pathway of a cell as it differentiates from a stem cell state to a mature lineage-committed one has been historically understood in terms of Waddington''s landscape, consisting of hills and valleys. The smooth top and valley-strewn bottom of the hill represent their undifferentiated and differentiated states, respectively. Although mathematical ideas rooted in nonlinear dynamics and bifurcation theory have been used to quantify this picture, the importance of time delays arising from multistep chemical reactions or cellular shape transformations have been ignored so far. We argue that this feature is crucial in understanding cell differentiation and explore the role of time delay in a model of a single-gene regulatory circuit. We show that the interplay of time-dependent drive and delay introduces a new regime where the system shows sustained oscillations between the two admissible steady states. We interpret these results in the light of recent perplexing experiments on inducing the pluripotent state in mouse somatic cells. We also comment on how such an oscillatory state can provide a framework for understanding more general feedback circuits in cell development.     

Microfluidic‐Nanofiber Hybrid Array for Screening of Cellular Microenvironments

Cellular microenvironments are generally sophisticated, but crucial for regulating the functions of human pluripotent stem cells (hPSCs). Despite tremendous effort in this field, the correlation between the environmental factors—especially the extracellular matrix and soluble cell factors—and the desired cellular functions remains largely unknown because of the lack of appropriate tools to recapitulate in vivo conditions and/or simultaneously evaluate the interplay of different environment factors. Here, a combinatorial platform is developed with integrated microfluidic channels and nanofibers, associated with a method of high‐content single‐cell analysis, to study the effects of environmental factors on stem cell phenotype. Particular attention is paid to the dependence of hPSC short‐term self‐renewal on the density and composition of extracellular matrices and initial cell seeding densities. Thus, this combinatorial approach provides insights into the underlying chemical and physical mechanisms that govern stem cell fate decisions.