Notch信号通路对神经干细胞增殖分化的作用

神经干细胞作为一种具有自我更新能力和多向分化潜能的细胞,它的增殖和分化受到多种源于自身或外在、邻近或远程细胞信号通路的调控,各种细胞因子及胞间通讯在神经干细胞的增殖和分化中发挥着重要的作用。近年来的多种研究表明,Notch信号通路正是这样一种可以通过相邻细胞的配体与受体相互作用,从而传递信号,进一步发挥其生物学功能的重要信号通路。该通路参与了神经干细胞维持自我形态及向多种具有不同功能的神经细胞分化的过程．对于研究神经干细胞的增殖和分化具有巨大的意义。该文将就当前Notch信号通路对神经干细胞增殖分化影响的相关研究进行简要综述。     

Wnt信号通路与神经干细胞

神经干细胞增殖、分化机制的研究为神经系统疾病治疗提供了新的途径,具有巨大的潜在应用价值和理论研究意义。业已发现,Wnt信号通路对神经干细胞的增殖发挥着决定性作用,但新近的研究却表明Wnt信号能够明显促进神经干细胞向神经元分化,这种不同的表现可能与神经干细胞的内在特点、周围环境及靶基因的不同有关。本文试从Wnt信号通路及其在调控神经干细胞的增殖、分化中的作用加以综述。     

巨核细胞生成调控相关细胞因子及其作用研究进展

造血干细胞分化生成巨核细胞是一个十分复杂的过程,包括造血干细胞动员及其向巨核系祖细胞分化,巨核系祖细胞增殖、分化生成未成熟巨核细胞,巨核细胞的成熟和血小板释放等过程。研究发现,造血干细胞动员及其向各系细胞分化的大部分过程都在一种称为"龛"的结构中进行,多种龛内信号分子参与了造血干细胞的动员和分化调控。该文对造血干细胞龛内参与造血干细胞动员和分化生成巨核细胞的几种重要细胞因子及其调控作用进行综述。     

中医药与脑缺血后海马神经干细胞增殖与分化

单味中药、中医复方和针灸等中医疗法对神经干细胞的增殖、分化研究是当前的研究热点。本文对脑缺血后单味中药、中医复方和针灸中药促进海马神经干细胞增殖、分化作用研究进行综述,通过对notch和wnt信号通路调控脑缺血后海马神经干细胞增殖、分化机制研究进行总结,为中医药在脑缺血后海马神经干细胞增殖、分化及相关机制的研究提供科学理论依据和参考。     

人嗅黏膜神经干细胞体外培养及氟西汀对其增殖和神经发生的影响

人嗅黏膜神经干细胞是新近发现的可用于神经精神疾病研究的良好材料,同时,抗抑郁治疗促进脑部神经干细胞增殖及向神经细胞转化。然而,嗅黏膜神经干细胞体外培养方法及抗抑郁药对其增殖及神经发生的影响尚不清楚。该研究采用组织块培养获取嗅细胞,神经球培养法纯化神经干细胞,Nestin免疫荧光验证神经干细胞特异性。加入促神经分化培养基诱导神经干细胞向神经细胞分化,MAP2(microtubule associated protein 2)、TUJ1(β3-tubulin)免疫荧光验证神经细胞特异性。采用CCK-8和蛋白质分子印记技术分别检测抗抑郁药对嗅黏膜神经干细胞增殖及分化的影响。结果显示,体外培养嗅黏膜神经干细胞呈球状聚集;Nestin、MAP2、TUJ1免疫荧光阳性;抗抑郁药促进嗅黏膜神经干细胞增殖、促进其向神经细胞转化,TUJ1表达上升。综上所述,抗郁药能够促进神经干细胞增殖及神经发生,可能为其抗抑郁治疗的机制之一。     

LincRNA1230抑制小鼠胚胎干细胞向神经前体细胞分化

胚胎干细胞是一类具有多向分化潜能的细胞.胚胎干细胞可以模拟体内发育过程,在无外界信号分子刺激的情况下,自发向神经前体细胞分化.有研究表明,这一体外发育过程受神经分化相关转录因子和表观遗传修饰的共同调控,然而该过程中的分子机制尚不清楚.本研究发现长链非编码RNA1230(LincRNA1230)参与了小鼠(Mus musculus)胚胎干细胞向神经前体细胞的分化过程.在小鼠的胚胎干细胞中过表达LincRNA1230可以显著抑制其神经分化效率;反之,干扰LincRNA1230可以提高分化效率.进一步研究表明,LincRNA1230通过结合Wdr5,降低神经分化相关基因启动子区H3K4me3的修饰水平,从而抑制相关基因的表达活性.这些发现揭示了LincRNA1230在小鼠胚胎干细胞神经分化过程中的重要作用.     

Notch信号转导通路对神经干细胞的调控

神经干细胞增殖、分化机制研究为神经系统疾病治疗提供了新的途径,具有巨大的潜在应用价值和理论研究意义。已发现Notch信号对神经干细胞的维持和抑制分化发挥着决定性作用,Notch信号由Notch受体、DSL(Delta／Serrate／LAG-2)配体,CSL(CBFl／Suppressor of Haidess(Su(H))／LAG-1)DNA结合蛋白和一些蛋白水解酶组成。本文主要综述了Notch信号通路及其在调控神经干细胞的增殖、分化中的作用。     

TWEAK/Fn14信号调控干细胞增殖与分化的作用与机制

肿瘤坏死因子样弱凋亡诱导蛋白(TWEAK)是肿瘤坏死因子(TNF)超家族成员,通过作用于唯一受体成纤维细胞生长因子14(Fn14)调控细胞的增殖、分化和迁移等多种生命活动。近来研究表明,TWEAK/Fn14信号可以作用于多种干细胞,如肝干细胞、神经干细胞和间充质干细胞等,通过影响其增殖与分化的能力,干预组织的修复与再生。对该领域的研究进行综述,将有助于揭示TWEAK/Fn14信号调控干细胞增殖与分化的作用与机制,并为干细胞在疾病发生机制等基础研究、细胞治疗和组织工程等临床医学研究提供新的方向。     

Notch信号通路对干细胞分化的影响

干细胞的增殖分化受到自身或外在、远程或近程多种信号通路的调控,而细胞之间的相互通讯在此过程中起到重要作用。Notch通路就是通过相邻细胞之间相互通讯调控细胞分化的重要信号通路之一,众多研究显示,该通路的活化在干细胞分化过程中发挥了重要调节作用,本文就此相关研究进展作一简要综述。     

细胞外基质硬度调控间充质干细胞分化

新近研究表叽细胞外基质（extracellularmatrix,ECM）的物理性质,特别是硬度或弹性,能对细胞的黏附、铺展、迁移、增殖、分化和凋亡等多种功能和行为产生重要影响。间充质干细胞（mesenchymalstemcells,MSCs）是组织工程和细胞治疗的理想种子细胞。ECM硬度可诱导MSCs向脂肪、软骨、神经、肌肉和骨等方向分化。该文综合论述了ECM硬度对干细胞分化的影响,涵盖了构建ECM硬度的测量、调控与表征等,不同培养条件下干细胞对硬度的响应和分化以及硬度和其他因素的联合作用;在此基础上,进一步论述了干细胞分化过程中细胞感应ECM硬度并转化为生物学信号的机制和信号通路。该文还总结了在ECM硬度调控干细胞分化行为领域最新的研究进展情况,较为系统地分析了材料学、细胞生物学、分子生物学水平的主要影响因素,并对本领域未来需要重点研究的问题进行了展望。     

Arachidonic acid-induced Ca2+ entry is involved in early steps of tumor angiogenesis

Growth factor-induced intracellular calcium signals in endothelial cells regulate cytosolic and nuclear events involved in the angiogenic process. Among the intracellular messengers released after proangiogenic stimulation, arachidonic acid (AA) plays a key role and its effects are strictly related to calcium homeostasis and cell proliferation. Here, we studied AA-induced intracellular calcium signals in endothelial cells derived from human breast carcinomas (B-TEC). AA promotes B-TEC proliferation and organization of vessel-like structures in vitro. The effect is directly mediated by the fatty acid without a significant contribution of its metabolites. AA induces Ca(2+)(i) signals in the entire capillary-like structure during the early phases of tubulogenesis in vitro. No such responses are detectable in B-TECs organized in more structured tubules. In B-TECs growing in monolayer, AA induces two different signals: a Ca(2+)(i) increase due to Ca(2+) entry and an inhibition of store-dependent Ca(2+) entry induced by thapsigargin or ATP. An inhibitor of Ca(2+) entry and angiogenesis, carboxyamidotriazole, significantly and specifically decreases AA-induced B-TEC tubulogenesis, as well as AA-induced Ca(2+) signals in B-TECs. We conclude that (a) AA-activated Ca(2+) entry is associated with the progression through the early phases of angiogenesis, mainly involving proliferation and tubulogenesis, and it is down-regulated during the reorganization of tumor-derived endothelial cells in capillary-like structures; and (b) inhibition of AA-induced Ca(2+) entry may contribute to the antiangiogenic action of carboxyamidotriazole.     

TAM Receptors Support Neural Stem Cell Survival,Proliferation and Neuronal Differentiation

Tyro3, Axl and Mertk (TAM) receptor tyrosine kinases play multiple functional roles by either providing intrinsic trophic support for cell growth or regulating the expression of target genes that are important in the homeostatic regulation of immune responses. TAM receptors have been shown to regulate adult hippocampal neurogenesis by negatively regulation of glial cell activation in central nervous system (CNS). In the present study, we further demonstrated that all three TAM receptors were expressed by cultured primary neural stem cells (NSCs) and played a direct growth trophic role in NSCs proliferation, neuronal differentiation and survival. The cultured primary NSCs lacking TAM receptors exhibited slower growth, reduced proliferation and increased apoptosis as shown by decreased BrdU incorporation and increased TUNEL labeling, than those from the WT NSCs. In addition, the neuronal differentiation and maturation of the mutant NSCs were impeded, as characterized by less neuronal differentiation (β-tubulin III⁺) and neurite outgrowth than their WT counterparts. To elucidate the underlying mechanism that the TAM receptors play on the differentiating NSCs, we examined the expression profile of neurotrophins and their receptors by real-time qPCR on the total RNAs from hippocampus and primary NSCs; and found that the TKO NSC showed a significant reduction in the expression of both nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), but accompanied by compensational increases in the expression of the TrkA, TrkB, TrkC and p75 receptors. These results suggest that TAM receptors support NSCs survival, proliferation and differentiation by regulating expression of neurotrophins, especially the NGF.     

未成熟钠通道调控大鼠胚胎神经干细胞分化

钠通道在各类神经元上高表达,参与细胞多种生理功能的调节,是神经元实现功能活动的基本单位．未成熟神经元上钠/钙通道所诱发和自发的电位活动对后期的发育成熟至关重要．然而,发育中的钠通道是否参与神经干细胞(neural stem cells, NSCs)分化的调控尚不清楚．本研究证明,未成熟的钠通道参与NSCs分化调控．Western印迹结果显示,在分化第1,3,5,7 d的NSCs上钠通道和胞外信号调节激酶（ERK）的蛋白表达与分化时间正相关.免疫组化结果发现,与对照组比较,加入电压门控钠通道阻断剂TTX可明显下调NeuN、GFAP和Gal-c在NSCs中的表达（P＜0.05）,提示钠通道参与NSCs分化的调控.当采用veratridine激动钠通道后,激光共聚焦检测到细胞内Ca2+浓度明显升高,免疫组化和Western印迹结果显示细胞内Ca2+浓度明显升高,p-ERK表达量明显上调;相反,TTX可明显阻断Veratridine所引起的细胞内Ca2+浓度上调,并使p-ERK峰值明显降低和延后（P＜0.05）．研究结果表明,未成熟钠通道可通过激活ERK信号途径促进NSCs的分化．钠通道的这种作用可能是由钙离子介导的,其详尽机制有待进一步研究．     

Muscarinic acetylcholine receptors involved in the regulation of neural stem cell proliferation and differentiation in vitro

Neural stem cells (NSCs) are currently considered powerful candidates for cell therapy in neurodegenerative disorders such as Parkinson's disease. However, it is not known when and how NSCs begin to differentiate functionally. Recent reports suggest that classical neurotransmitters such as acetylcholine (Ach) are involved in the proliferation and differentiation of neural progenitor cells, suggesting that neurotransmitters play an important regulatory role in development of the central nervous system (CNS). We have shown by calcium imaging and immunochemistry that proliferation and differentiation are enhanced by M2 muscarinic Ach receptors (mAchR) expressed on the NSC surface and on their neural progeny. Moreover, atropine, an mAchR antagonist, blocks the enhancement and inhibits the subsequent differentiation of NSCs. Further understanding of this neural-nutrition role of Ach might elucidate fetal brain development, the brain's response to injury, and learning and memory.     

Chondroitin sulfate glycosaminoglycans control proliferation, radial glia cell differentiation and neurogenesis in neural stem/progenitor cells

Although the local environment is known to regulate neural stem cell (NSC) maintenance in the central nervous system, little is known about the molecular identity of the signals involved. Chondroitin sulfate proteoglycans (CSPGs) are enriched in the growth environment of NSCs both during development and in the adult NSC niche. In order to gather insight into potential biological roles of CSPGs for NSCs, the enzyme chondroitinase ABC (ChABC) was used to selectively degrade the CSPG glycosaminoglycans. When NSCs from mouse E13 telencephalon were cultivated as neurospheres, treatment with ChABC resulted in diminished cell proliferation and impaired neuronal differentiation, with a converse increase in astrocytes. The intrauterine injection of ChABC into the telencephalic ventricle at midneurogenesis caused a reduction in cell proliferation in the ventricular zone and a diminution of self-renewing radial glia, as revealed by the neurosphere-formation assay, and a reduction in neurogenesis. These observations suggest that CSPGs regulate neural stem/progenitor cell proliferation and intervene in fate decisions between the neuronal and glial lineage.     

Nucleoplasmic calcium is required for cell proliferation

Ca(2+) signals regulate cell proliferation, but the spatial and temporal specificity of these signals is unknown. Here we use selective buffers of nucleoplasmic or cytoplasmic Ca(2+) to determine that cell proliferation depends upon Ca(2+) signals within the nucleus rather than in the cytoplasm. Nuclear Ca(2+) signals stimulate cell growth rather than inhibit apoptosis and specifically permit cells to advance through early prophase. Selective buffering of nuclear but not cytoplasmic Ca(2+) signals also impairs growth of tumors in vivo. These findings reveal a major physiological and potential pathophysiological role for nucleoplasmic Ca(2+) signals and suggest that this information can be used to design novel therapeutic strategies to regulate conditions of abnormal cell growth.     

Upregulation of FIk-1 by bFGF via the ERK pathway is essential for VEGF-mediated promotion of neural stem cell proliferation

Neural stem cells (NSCs) constitute the cellular basis for embryonic brain development and neurogenesis.The processis regulated by NSC niche including neighbor cells such as vascular and glial cells.Since both vascular and glial cellssecrete vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF),we assessed the effect ofVEGF and bFGF on NSC proliferation using nearly homogeneous NSCs that were differentiated from mouse embryonicstem cells.VEGF alone did not have any significant effect.When bFGF was added,however,VEGF stimulated NSCproliferation in a dose-dependent manner,and this stimulation was inhibited by ZM323881,a VEGF receptor (Flk-1)-specific inhibitor.Interestingly,ZM323881 also inhibited cell proliferation in the absence of exogenous VEGF,suggestingthat VEGF autocrine plays a role in the proliferation of NSCs.The stimulatory effect of VEGF on NSC proliferationdepends on bFGF,which is likely due to the fact that expression of Flk-1 was upregulated by bFGF via phosphoryla-tion of ERK1/2.Collectively,this study may provide insight into the mechanisms by which mieroenvironmental nichesignals regulate NSCs.     

Upregulation of Flk-1 by bFGF via the ERK pathway is essential for VEGF-mediated promotion of neural stem cell proliferation

Neural stem cells （NSCs） constitute the cellular basis for embryonic brain development and neurogenesis. The process is regulated by NSC niche including neighbor cells such as vascular and glial cells. Since both vascular and glial cells secrete vascular endothelial growth factor （VEGF） and basic fibroblast growth factor （bFGF）, we assessed the effect of VEGF and bFGF on NSC proliferation using nearly homogeneous NSCs that were differentiated from mouse embryonic stem cells. VEGF alone did not have any significant effect. When bFGF was added, however, VEGF stimulated NSC proliferation in a dose-dependent manner, and this stimulation was inhibited by ZM323881, a VEGF receptor （Flk-1）- specific inhibitor. Interestingly, ZM323881 also inhibited cell proliferation in the absence of exogenous VEGF, suggesting that VEGF autocrine plays a role in the proliferation of NSCs. The stimulatory effect of VEGF on NSC proliferation depends on bFGF, which is likely due to the fact that expression of Flk-1 was upregulated by bFGF via phosphorylation of ERK1/2. Collectively, this study may provide insight into the mechanisms by which microenvironmental niche signals regulate NSCs.