Metabolic-epigenetic nexus in regulation of stem cell fate

Stem cell fate determination is one of the central questions in stem cell biology,and although its regulation has been studied at genomic and proteomic levels,a variety of biological activities in cells occur at the metabolic level.Metabolomics studies have established the metabolome during stem cell differentiation and have revealed the role of metabolites in stem cell fate determination.While metabolism is considered to play a biological regulatory role as an energy source,recent studies have suggested the nexus between metabolism and epigenetics because several metabolites function as cofactors and substrates in epigenetic mechanisms,including histone modification,DNA methylation,and microRNAs.Additionally,the epigenetic modification is sensitive to the dynamic metabolites and consequently leads to changes in transcription.The nexus between metabolism and epigenetics proposes a novel stem cell-based therapeutic strategy through manipulating metabolites.In the present review,we summarize the possible nexus between metabolic and epigenetic regulation in stem cell fate determination,and discuss the potential preventive and therapeutic strategies via targeting metabolites.

Regulation of neural stem cell fate decisions by mitochondrial dynamics

Stem cells possess the ability to divide symmetrically or asymmet- rically to allow for maintenance of the stem cell pool or become committed progenitors and differentiate into various cell lineages. The unique self-renewal capabilities and pluripotency of stem cells are integral to tissue regeneration and repair （Oh et al., 2014）. Mul- tiple mechanisms including intracellular programs and extrinsic cues are reported to regulate neural stem cell （NSC） fate （Bond et al., 2015）. A recent study, published in Cell Stern Cell, identified a novel mechanism whereby mitochondrial dynamics drive NSC fate （Khacho et al., 2016）.

MicroRNAs as novel regulators of stem cell fate

Mounting evidence in stem cell biology has shown that microRNAs(miRNAs) play a crucial role in cell fate specification, including stem cell self-renewal, lineagespecific differentiation, and somatic cell reprogramming.These functions are tightly regulated by specific gene expression patterns that involve miRNAs and transcription factors. To maintain stem cell pluripotency, specific miRNAs suppress transcription factors that promote differentiation, whereas to initiate differentiation, lineagespecific miRNAs are upregulated via the inhibition of transcription factors that promote self-renewal. Small molecules can be used in a similar manner as natural miRNAs, and a number of natural and synthetic small molecules have been isolated and developed to regulate stem cell fate. Using miRNAs as novel regulators of stem cell fate will provide insight into stem cell biology and aid in understanding the molecular mechanisms and crosstalk between miRNAs and stem cells.Ultimately, advances in the regulation of stem cell fate will contribute to the development of effective medical therapies for tissue repair and regeneration. This review summarizes the current insights into stem cell fate determination by miRNAs with a focus on stem cell self-renewal, differentiation, and reprogramming. Small molecules that control stem cell fate are also highlighted.

JAK/STAT signaling regulates tissue outgrowth and male germline stem cell fate in Drosophila

In multicellular organisms, biological activities are regulated by cell signaling. The various signal transduction path- ways regulate cell fate, proliferation, migration, and polarity. Miscoordination of the communicative signals will lead to disasters like cancer and other fatal diseases. The JAK/STAT signal transduction pathway is one of the pathways, which was first identified in vertebrates and is highly conserved throughout evolution. Studying the JAK/STAT signal transduc- tion pathway in Drosophila provides an excellent opportunity to understand the molecular mechanism of the cell regu- lation during development and tumor formation. In this review, we discuss the general overview of JAK/STAT signaling in Drosophila with respect to its functions in the eye development and stem cell fate determination.

Orchestrating stem cell fate: Novel tools for regenerative medicine

Mesenchymal stem cells are undifferentiated cells able to acquire different phenotypes under specific stimuli. In vitro manipulation of these cells is focused on understanding stem cell behavior, proliferation and pluripotency. Latest advances in the field of stem cells concern epigenetics and its role in maintaining self-renewal and differentiation capabilities. Chemical and physical stimuli can modulate cell commitment, acting on gene expression of Oct-4, Sox-2 and Nanog, the main stemness markers, and tissue-lineage specific genes. This activation or repression is related to the activity of chromatin-remodeling factors and epigenetic regulators, new targets of many cell therapies. The aim of this review is to afford a view of the current state of in vitro and in vivo stem cell applications, highlighting the strategies used to influence stem cell commitment for current and future cell therapies. Identifying the molecular mechanisms controlling stem cell fate could open up novel strategies for tissue repairing processes and other clinical applications.

Small molecules for mesenchymal stem cell fate determination

Mesenchymal stem cells(MSCs)are adult stem cells harboring self-renewal and multilineage differentiation potential that are capable of differentiating into osteoblasts,adipocytes,or chondrocytes in vitro,and regulating the bone marrow microenvironment and adipose tissue remodeling in vivo.The process of fate determination is initiated by signaling molecules that drive MSCs into a specific lineage.Impairment of MSC fate determination leads to different bone and adipose tissue-related diseases,including aging,osteoporosis,and insulin resistance.Much progress has been made in recent years in discovering small molecules and their underlying mechanisms control the cell fate of MSCs both in vitro and in vivo.In this review,we summarize recent findings in applying small molecules to the trilineage commitment of MSCs,for instance,genistein,medicarpin,and icariin for the osteogenic cell fate commitment;isorhamnetin,risedronate,and arctigenin for pro-adipogenesis;and atractylenolides and dihydroartemisinin for chondrogenic fate determination.We highlight the underlying mechanisms,including direct regulation,epigenetic modification,and post-translational modification of signaling molecules in the AMPK,MAPK,Notch,PI3K/AKT,Hedgehog signaling pathways etc.and discuss the small molecules that are currently being studied in clinical trials.The target-based manipulation of lineage-specific commitment by small molecules offers substantial insights into bone marrow microenvironment regulation,adipose tissue homeostasis,and therapeutic strategies for MSC-related diseases.

Biomaterial property-controlled stem cell fates for cardiac regeneration

Myocardial infarction(MI)affects more than 8 million people in the United States alone.Due to the insufficient regeneration capacity of the native myocardium,one widely studied approach is cardiac tissue engineering,in which cells are delivered with or without biomaterials and/or regulatory factors to fully regenerate the cardiac functions.Specifically,in vitro cardiac tissue engineering focuses on using biomaterials as a reservoir for cells to attach,as well as a carrier of various regulatory factors such as growth factors and peptides,providing high cell retention and a proper microenvironment for cells to migrate,grow and differentiate within the scaffolds before implantation.Many studies have shown that the full establishment of a functional cardiac tissue in vitro requires synergistic actions between the seeded cells,the tissue culture condition,and the biochemical and biophysical environment provided by the biomaterials-based scaffolds.Proper electrical stimulation and mechanical stretch during the in vitro culture can induce the ordered orientation and differentiation of the seeded cells.On the other hand,the various scaffolds biochemical and biophysical properties such as polymer composition,ligand concentration,biodegradability,scaffold topography and mechanical properties can also have a significant effect on the cellular processes.

Genome-wide Analysis of Smad Targets Reveals the Role of BMP Signaling in Embryonic Stem Cell Fate Determination

Embryonic stem (ES) cells are under precise control of both intrinsic self-renewal gene regulatory network and extrinsic growth factor-triggered signaling cascades.

Biotechnology smart control over stem cell fate commitment at nanoscale

In the landscape of desirable stem-cell-based regeneration,the fate of cell is directed by orchestrated dialog between nanoscale subcellular receptors and biointerfacial niches^([1]).This bottom-up development manner has inspired a great many nanogeometric^([2])and nanotopographic^([3])material-based biointerfaces promising for regenerative medicine.These previous studies shed

Regulation of intestinal stem cell fate specification

The remarkable ability of rapid self-renewal makes the intestinal epithelium an ideal model for the study of adult stem cells. The intestinal epithelium is organized into villus and crypt, and a group of intestinal stem cells located at the base of crypt are responsible for this constant self-renewal throughout the life. Identification of the intestinal stem cell marker Lgr5, isolation and in vitro culture of Lgr5+ intestinal stem cells and the use of transgenic mouse models have significantly facilitated the studies of intestinal stem cell homeostasis and differentiation, therefore greatly expanding our knowledge of the regulatory mechanisms underlying the intestinal stem cell fate determination. In this review, we summarize the current understanding of how signals of Wnt, BMP, Notch and EGF in the stem cell niche modulate the intestinal stem cell fate.

Imprinted Zac1 in neural stem cells

Neural stem cells(NSCs) and imprinted genes play an important role in brain development. On historical grounds, these two determinants have been largely studied independently of each other. Recent evidence suggests, however, that NSCs can reset select genomic imprints to prevent precocious depletion of the stem cell reservoir. Moreover, imprinted genes like the transcriptional regulator Zac1 can fine tune neuronal vs astroglial differentiation of NSCs. Zac1 binds in a sequence-specific manner to pro-neuronal and imprinted genes to confer transcriptional regulation and furthermore coregulates members of the p53-family in NSCs. At the genome scale, Zac1 is a central hub of an imprinted gene network comprising genes with animportant role for NSC quiescence, proliferation and differentiation. Overall, transcriptional, epigenomic, and genomic mechanisms seem to coordinate the functional relationships of NSCs and imprinted genes from development to maturation, and possibly aging.

Notch信号通路调控间充质干细胞的增殖与分化

背景:研究发现,Notch的配体和受体都是细胞膜表面蛋白,是介导细胞间通讯的一种重要蛋白,Notch信号通路在间充质干细胞增殖与分化过程中起着至关重要的调控作用。目的:就Notch信号通路对间充质干细胞增殖与分化过程的调节机制进行综述,总结和阐述Notch信号通路如何调控间充质干细胞的增殖与分化相关研究进展,为未来利用干细胞治疗各种相关疾病提供理论支持。方法:由第一作者应用计算机在中国知网、万方、维普、PubMed、Web of Science和Nature数据库检索涉及Notch信号通路调控间充质干细胞增殖与分化的相关文献,中文检索词为“间充质干细胞,Notch,Notch信号通路,增殖,分化”,英文检索词为“mesenchymal stem cells,MSC,Notch,Notch signaling pathway,proliferation,differentiation”,结合文献追溯法查找部分文献,最终纳入87篇文献进入综述分析。结果与结论:①Notch信号通路是一条存在于多细胞生物中保守的信号通路,通过受体与配体结合介导相邻细胞间的通信,在调节细胞分化、增殖、凋亡和细胞周期中发挥重要作用。②间充质干细胞是一类具有自我增殖和多向分化潜能的成体干细胞,可受外界信号通路的调控从而影响其增殖与分化,而Notch信号通路作为其中之一,当Notch配体被激活后,Notch蛋白会经历2次蛋白水解裂解,释放出Notch细胞内结构域NICD随后进入细胞核,进而促进靶基因的转录以达到调控骨髓、脂肪和脐带等不同来源的间充质干细胞增殖与分化的作用,但是调控同物种不同组织来源间充质干细胞在增殖与分化过程中的具体机制有所不同。③Notch信号通路可以调控间充质干细胞分化成不同的靶细胞,但是由于分化的靶细胞不同,Notch信号通路的受体或配体表达水平有差异。④临床上以Notch信号通路为靶点,促进间充质干细胞治疗各种难治性疾病,如再生障碍性贫血症、严重的关节损伤、缺血性脑卒中和心肌梗死等都有很好的应用前景。⑤通过探究Notch信号通路调控大鼠、小鼠和人的骨髓间充质干细胞受体及配体的表达水平,不同物种来源的间充质干细胞其Notch信号通路在增殖与分化的过程中的调控作用也有所不同。⑥间充质干细胞因其安全、免疫排斥性低及治疗前景广等优势在组织工程中的作用逐渐凸显,Notch信号通路调控间充质干细胞增殖与分化的影响因素繁多,后续研究应进一步优化影响因素变量,探索调控间充质干细胞增殖与分化的标准化研究。

The role of the microenvironment on the fate of adult stem cells

Adult stem cells(SCs) exist in all tissues that promote tissue growth, regeneration, and healing throughout life. The SC niche in which they reside provides signals that direct them to proliferate, differentiate, or remain dormant; these factors include neighboring cells, the extracellular matrix, soluble molecules, and physical stimuli. In disease and aging states, stable or transitory changes in the microenvironment can directly cause SC activation or inhibition in tissue healing as well as functional regulation. Here, we discuss the microenvironmental regulation of the behavior of SC and focus on plasticity approaches by which various environmental factors can enhance the function of SCs and more effectively direct the fate of SCs.

Hsp83 regulates the fate of germline stem cells in Drosophila ovary

In adult tissues,stem cells are defined by their unique capacity to self-renew and produce differentiated cells to maintain tissue homeostasis.Drosophila ovarian germline stem cells（GSCs）provide a powerful model for investigating the regulatory mechanisms underlying stem cell fate determination in vivo（Chen and Mckearin.

干细胞研究中的化学生物学:学科交叉的新前沿

化学生物学(chemical biology)是利用小分子化合物干预和解析生物系统,认识生物系统的本质和内在规律的学科,在包括干细胞研究在内的多个领域得到应用。近年来,干细胞研究取得了引人瞩目的进步,这些基础研究的进步也正在推动着干细胞技术在再生医学中的应用。对细胞命运转换分子基础的认识以及精确操控是干细胞研究的核心问题。小分子化合物因其在使用的便捷性、可控性和功能多样性等方面的显著优势,正越来越多地被用于干预和研究干细胞的增殖、分化和重编程等生物学行为。利用化学分子调控体内干细胞的生物学行为、促进其体内再生和修复将有望成为再生医学领域极具潜力的发展方向。

高镁对体外培养原代神经干细胞分化命运的影响及其机制

目的探索高镁对神经发生过程中神经干细胞分化命运的影响及其潜在机制。方法从C57／BL6胎鼠大脑中分离神经干细胞，通过添加硫酸镁（MgSO4）调节培养基镁离子浓度并诱导分化，第6天通过免疫细胞化学荧光染色观察成熟神经元标记物β-Ⅲtubulin（Tuj1）和胶质细胞标记物胶质原纤维酸性蛋白（GFAP）的阳性细胞比例，Westernblot检测ERK1／2表达，qPCR检测Tujl、GFAP的mRNA水平。结果高镁组（0．8mM和1．0mM）相比于对照组（0．6mM），Tuj1阳性细胞的比例增加，GFAP阳性细胞比例减少，Tuj1表达上调，GFAP表达下调，pERK／ERK上调，差异具有统计学意义（P〈0．05），高镁组添加ERK抑制剂PD0325901后，以上指标与对照组比较差异无统计学意义（P〉0．05）。结论高镁可促进神经干细胞向神经元分化，抑制其向神经胶质细胞分化，其作用可能与ERK1／2的激活有关。

右归饮干预激素性股骨头坏死大鼠骨髓间充质干细胞的自噬及命运

背景:右归饮是临床治疗激素性股骨头坏死的经验方,文献表明激素性股骨头坏死的发病机制与激素诱导骨髓间充质干细胞自噬下调及命运改变相关。。目的:探讨右归饮对激素性股骨头坏死模型大鼠骨髓间充质干细胞自噬及命运的干预作用。方法:采用肠杆菌内毒素联合较大剂量地塞米松制作早期股骨头坏死模型。将40只自发性高血压大鼠随机分为5组:空白对照组、模型组、高剂量右归饮组、中剂量右归饮组、低剂量右归饮组。经过6周干预,取各组大鼠股骨近端髓腔组织行苏木精-伊红染色并对自噬蛋白LC3Ⅱ、P53及beclin-1进行免疫组化染色定位;分离培养各组大鼠骨髓间充质干细胞,成骨诱导后行茜素红染色、骨碱性磷酸酶定量,成脂诱导后行油红O染色,MTT检测骨髓间充质干细胞生长活性,Western blot检测股骨头组织中LC3Ⅱ、P53及beclin-1蛋白表达。结果与结论:①免疫组化及Western blot显示右归饮组显著上调了自噬蛋白LC3Ⅱ、P53及beclin-1表达,且上调作用呈剂量依赖性;②茜素红染色、油红O染色和骨碱性磷酸酶定量提示右归饮能显著干预骨髓间充质干细胞命运,上调其成骨分化,下调成脂分化,作用呈剂量依赖性;③MTT提示右归饮显著提高了骨髓间充质干细胞增殖能力,但各剂量无明显差异;④结果表明,右归饮能显著提高激素性股骨头坏死模型大鼠骨髓间充质干细胞自噬表达,改变骨髓间充质干细胞命运,使其成骨分化上调,成脂分化下调,为阐释右归饮治疗激素性股骨头坏死的作用机制提供了一定依据。

神经干细胞的命运决定机制及其靶点调控研究进展

神经干细胞(neural stem cells,NSCs)是哺乳动物神经系统中神经元、星形胶质细胞、少突胶质细胞的分化来源,近年来对于NSCs的增殖与分化机制及其在临床治疗神经退行性疾病的研究在世界范围内引起了学者们的极大兴趣。多种细胞调节因子存在于微环境中共同调节NSCs的自我更新、迁移及分化,其中Notch通路,NF-κB通路与Wnt通路尤其作为NSCs发育中的"命运决定者"而受到广泛的关注,它们中的每条通路均具有独自控制分化与增殖的能力。针对Notch通路、Wnt通路以及NF-κB通路对NSCs增殖与分化的作用机制进行了归纳与阐述,对其中潜在的药物作用靶点与目前最新的内、外源化合物对NSCs增殖与分化的作用进行了总结,希望对今后神经再生方面的研究提供理论指导。

CG6015基因在果蝇睾丸生殖干细胞生命维持中的功能研究

目的CG6015基因作为RNA剪接体的调控因子,是否参与调控果蝇睾丸生殖干细胞(GSCs)尚不明确。文中旨在探讨CG6015基因在果蝇睾丸GSCs生命维持中的功能,并探索其中潜在的调控机制。方法利用UAS-Gal4系统实现CG6015基因在果蝇睾丸GSCs中的特异性敲减。以W1118品系为对照组,Nos>CG6015 RNAi为实验组,采用免疫荧光染色技术分别观察2组睾丸的形态和GSCs的改变情况。在果蝇S2细胞中,应用基因沉默技术分别敲减阴性对照(NC)与CG6015基因,作为NC组与CG6015 siRNA组,利用qRT-PCR检测CG6015基因及RNA剪接体亚基Prp8、SmG和U2A的mRNA表达水平。结果与对照组小睾丸的比例(0)比较,实验组(100%)明显升高(P<0.001)。与对照组睾丸中的生殖融合体数量比较,实验组明显减少[(19.67±0.88)个vs(0.00±0.00)个,P<0.001]。与对照组比较,实验组Eya阳性细胞数量明显增加[(9.67±0.67)个vs(25.67±5.21)个,P<0.05]。与NC组Prp8、SmG基因的mRNA相对表达水平(1.00±0.00)比较,CG6015 siRNA组Prp8基因(0.39±0.03)明显下调,SmG基因(1.60±0.07)明显上调(P<0.05)。结论CG6015基因在果蝇睾丸中可以通过介导RNA剪接体来调控GSCs的生命维持,为男性不育症的致病机理提供了新思路。

ELF5在正常乳腺发育和乳腺肿瘤发生中的作用

ELF5(E74-like factor 5)也被称为ESE2,属于ETS(E-twenty-six)转录因子家族成员之一,它在调控胚胎发育以及乳腺组织发育中起到重要作用。在桑椹胚时期,ELF5在调控胚胎内细胞团向胚胎形成过程中或是在胎盘发育的细胞命运决定中起到关键作用。在哺乳动物正常乳腺发育中,ELF5可通过诱导细胞定向分化而获得孕期乳腺分泌细胞类型,从而调控乳腺干/祖细胞的命运。在人类乳腺癌中,ELF5是诱导乳腺肿瘤细胞由表达雌激素受体阳性(ER+)的luminal亚型向表达雌激素受体阴性(ER-)的basal亚型转化的一个关键调控因子,并抑制细胞获得雌激素敏感表型。现主要综述了ELF5的结构特点、功能以及其在哺乳动物乳腺发育中的调控作用。