间充质干细胞增殖、衰老及分化:Wnt信号通路经典与非经典的调控作用

背景:间充质干细胞作为再生医学及组织工程领域中的重要种子细胞来源,对其不同生物学特性的调控机制一直是目前研究的热点。目的:综述Wnt信号通路调控间充质干细胞增殖、衰老及分化的研究进展。方法:应用计算机检索2002至2014年PubMed数据库及CNKI数据库,以"mesenchymal stem cells,Wnt signaling pathway,proliferation,senescence,differentiation"或"间充质干细胞,Wnt信号通路,增殖,衰老,分化"为关键词进行检索,重点对44篇文章进行分析。结果与结论:Wnt信号通路广泛参与调控间充质干细胞多种生物学特性。经典Wnt信号通路对间充质干细胞增殖及向成骨细胞分化具有双向调控作用,并能够促进其衰老及向神经细胞分化,抑制其向脂肪细胞分化;非经典Wnt信号通路则参与促进间充质干细胞衰老及向成骨细胞分化,抑制其增殖及向脂肪细胞分化,不参与其向神经细胞分化,为其应用于骨组织工程、神经损伤修复等领域提供了新的研究靶点。     

Rho GTPases与骨髓间充质干细胞的迁移和分化

Rho 家族小分子鸟苷三磷酸酶(small GTPases of Rho family, Rho GTPases)是调节细胞许多生理病理活动的关键分子开关,参与细胞骨架、基因转录、细胞周期进程、细胞黏附的调控及多条信号通路的调节.骨髓间充质干细胞(bone marrow-derived mesenchymal stem cells,MSCs)是一类具有自我更新和多向分化潜能的特殊细胞,通过增殖、迁移、分化等途径参与机体损伤组织的修复过程.研究表明,Rho GTPases在MSCs迁移、分化等过程中起着重要的调节作用.     

炎症转录因子C/EBPβ在间质细胞分化中作用与机制

免疫炎症性转录因子C/EBPβ在多种细胞的分化过程中起着重要作用.如在间充质细胞中,决定着间充质干细胞(MSCs)的分化方向,诱导脂肪细胞的分化,调节成骨细胞和软骨细胞分化.了解C/EBPβ及其不同亚型的在不同的间充质细胞中的作用,尤其是在成纤维细胞、脂肪细胞、软骨细胞和成骨细胞分化过程中的调控机制很有必要,随着间充质干细胞被再生医学重视,转录因子C/EBPβ有望成为未来研究的热点.     

经典Wnt信号通路对细胞成骨分化的调控作用

Wnt信号通路是参与体内多种器官发育和组织新陈代谢的保守性通路,可分为经典和非经典Wnt信号通路.其中,经典Wnt信号通路通过调节下游的成骨相关转录因子调控细胞成骨分化、骨基质形成和矿化,且在细胞分化的不同阶段发挥不同的调控作用.此外,经典Wnt信号通路还调控牙周组织干细胞成骨分化,该作用受外界微环境的影响.加深对经典Wnt信号通路的认识有助于治疗相关的骨疾病.     

Notch信号通路在感染过程中对免疫应答的调控作用

感染启动的先天性和适应性免疫应答依赖于巨噬细胞、树突状细胞以及T细胞等对病原体的识别与控制。Notch信号是一种高度保守的信号通路,通过相邻细胞间配受体结合被激活,进而协调细胞的重要生命过程。目前已证实Notch信号通路参与多种免疫细胞发育、分化、成熟和激活,并在感染性疾病中发挥重要作用。本文综述Notch信号通路在不同病原体感染过程中的免疫调控作用及其与其他通路的相互作用,并讨论在感染性疾病中以Notch信号为靶点的治疗方法及面临的挑战。     

骨化三醇通过PI3K/AKT促进BMP9诱导的间充质干细胞成骨分化作用

目的研究骨化三醇(calcitriol)对骨形态发生蛋白9(bone morphogenetic protein 9,BMP9)诱导的间充质干细胞(mesenchymal stem cells,MSCs)成骨分化作用的影响。方法实验分为4组:对照组、calcitriol组、BMP9组、calcitriol联合BMP9组。通过PNPP法检测各组碱性磷酸酶(alkaline phosphatase,ALP)活性;通过RT-PCR和Western blotting方法检测成骨分化标记物骨钙蛋白(osteocalcin,OCN)和骨桥蛋白(osteopontin,OPN)表达变化,同时检测AKT和β-catenin磷酸化水平以及和ALP活性水平;茜素红染色检测矿化结节形成。此外,用原子力显微镜测试MSCs成骨分化过程中细胞形态及细胞弹性模量改变。结果 calcitriol单独作用对MSCs成骨分化过程无明显作用,但是calcitriol可以增强BMP9诱导MSCs的ALP、OCN、OPN表达和矿化结节形成。同时,calcitriol和BMP9作用均不影响细胞弹性模量数值。BMP9和calcitriol联合作用可以增强AKT和β-catenin磷酸化水平,而PI3K抑制剂应用以后可以抑制这种磷酸化变化,并抑制联合作用后的ALP活性。calcitriol作用以后不影响BMP9诱导的BMP/Smad信号通路。结论 calcitriol通过激活PI3K/AKT信号通路从而协同BMP9促进MSCs成骨分化。研究不同调控因子对MSCs成骨分化的作用及机制对于骨质疏松等疾病的治疗和骨组织工程的发展有一定意义。     

Wnt/β-catenin信号通路与肝脏的发育及异常分化

Wnt/β-catenin信号通路在人类生物学的各个方面都发挥着重要作用,该通路在肝脏生物学中的作用也备受关注。Wnt/β-catenin信号通路在肝脏的生长、发育、再生、代谢等方面发挥重要作用,该通路也参与各种肝脏疾病进程,提示Wnt/β-catenin信号通路的正常调控是控制和影响肝脏生命活动的关键,其异常激活与肝脏的病理及肿瘤发生密切相关。本文对该通路与肝脏发育分化及疾病的关系研究作一综述。     

Notch信号通路与关节软骨发育及骨关节炎

背景:骨性关节炎时往往伴随软骨细胞间信号转导的异常,提示细胞间信号转导在骨性关节炎发生、发展过程中可能发挥重要作用。目的:综合分析Notch信号通路的最新进展,探讨Notch在调控骨髓间充质干细胞软骨相分化机制、调控软骨发育及软骨发生中的作用,分析Notch信号通路失调与骨关节炎的关系。方法:以Notch signaling pathway,osteoarthritis,chondrocytes,chondrogenesis,bone marrow stem cells为检索词,检索Pubmed数据库(1919-03/2009-02);以Notch信号通路,骨关节炎,软骨细胞,骨髓间充质干细胞为检索词,检索CNKI数据库(2004-02/2008-09)。文献检索语种限制为英文和中文。纳入与Notch信号通路有关的研究、Notch信号通路调控骨髓间充质干细胞软骨相分化机制的研究,以及Notch信号通路失调与骨关节炎的研究。排除重复性研究。以关节软骨的发育调控和软骨细胞的增殖胃评价指标。结果与结论:计算机初检得到632篇文献,根据纳入排除标准,对其中30篇文献进行分析。Notch信号通路是一个在进化过程中高度保守的信号通路,它通过Notch受体与配体的结合、Notch受体的酶切活化、可溶性Notch胞内区转移至细胞核并与CSLDNA结合蛋白相互作用,最终调控靶基因的表达,从而在细胞增殖、分化、凋亡及器官发育中发挥重要的调控作用。目前已证实,Notch信号参与并调控关节软骨的发育、软骨细胞增殖、分化,而Notch信号的失调在骨关节炎的发生、发展中扮演着十分重要的角色。提示深入研究Notch信号在骨性关节炎发病机制中的确切作用将有助于骨性关节炎的靶向治疗,从而为骨性关节炎的治疗开辟更加广阔的前景。     

Wnt信号通路调控免疫应答的研究进展

Wnt蛋白是一类分泌型糖蛋白,通过自分泌或旁分泌发挥作用,是一组调控胚胎形成期间细胞间信号传导、高度保守的分泌型信号分子。Wnt信号通路分为β-catenin依赖的经典信号通路以及非经典信号通路,广泛参与细胞的增殖、迁移和分化等过程。值得关注的是,Wnt信号通路调控巨噬细胞、T细胞、B细胞等多种免疫细胞的分化与发育,并通过多种机制调控免疫应答过程。此外,Wnt信号通路对肝星状细胞、内皮细胞等具有免疫特性细胞的生物学功能也发挥调控作用。本文对Wnt信号通路调控免疫应答的研究进展作一综述。     

骨髓间充质干细胞成脂和成骨分化过程中Wnt信号通路的调控效应

背景:骨髓间充质干细胞的成脂肪分化与成骨分化比例的失衡与许多骨疾病密切相关,而近些年发现Wnt信号通路在调控骨髓间充质干细胞的分化方向中起重要作用。目的:通过Wnt信号通路PCR基因芯片观察大鼠骨髓间充质干细胞分化为脂肪细胞和成骨细胞后相关基因表达的变化,寻找Wnt信号通路中调控骨髓间充质干细胞分化的靶基因。方法:采用大鼠第3代骨髓间充质干细胞分别进行成骨诱导和成脂诱导,7d后用Trizol萃取培养瓶中的细胞总RNA,倒置显微镜下观察骨髓间充质干细胞形态特征及成骨诱导后和成脂诱导后细胞形态特征。采用Wnt信号通路PCR芯片(大鼠)进行基因芯片检测,以未诱导组为对照,计算成脂肪诱导,成骨诱导后相关基因上调/下调的比值。结果与结论:①倒置显微镜下观察,传3代后可获得均一性较高的骨髓间充质干细胞,骨髓间充质干细胞经成骨诱导后向成骨细胞方向分化,经成脂诱导后向脂肪细胞方向分化。②与未诱导组相比,骨髓间充质干细胞成脂诱导后Wnt信号通路表达上调的基因(Dkk-1,kremen,FZD1,FZD7)等15个(ratio2),下调的基因(sFrp5,β-catenin,Dvl3,Tcf7)等16个(ratio0.5)。成骨诱导后,Wnt信号通路表达上调的基因(Dkk1,kremen,β-catenin,Wnt11)6个,表达下调的基因(sFrp5,sFRP4,Fzd1)等15个。提示Wnt信号通路在骨髓间充质干细胞成脂细胞分化和成骨细胞分化中发挥重要作用。     

Smad3-dependent nuclear translocation of beta-catenin is required for TGF-beta1-induced proliferation of bone marrow-derived adult human mesenchymal stem cells

Adult mesenchymal stem cells (MSCs) derived from bone marrow contribute to the regeneration of multiple types of mesenchymal tissues. Here we describe the functional role of a novel form of cross-talk between the transforming growth factor beta1 (TGF-beta1) and Wnt signaling pathways in regulating the activities of human MSCs. We show that TGF-beta1 induces rapid nuclear translocation of beta-catenin in MSCs in a Smad3-dependent manner. Functionally, this pathway is required for the stimulation of MSC proliferation and the inhibition of MSC osteogenic differentiation by TGF-beta1, likely through the regulation of specific downstream target genes. These results provide evidence for a new mode of cooperation between the TGF-beta and Wnt signaling pathways in this specific cellular context and suggest a potentially important role for this distinct signaling pathway in the control of self-renewal and differentiation of a specific type of MSCs.     

骨形态发生蛋白-2诱导心肌干细胞定向分化的信号转导机制

骨形态发生蛋白-2(BMP-2)对心肌干细胞(CSCs)的分化起重要作用,其信号通过受体激活并经Smads、p38MAPK和P1-3K等3条信号通路转导,调节多种心肌转录因子的表达,进而诱导CSCs的终末分化。细胞内的BMP-2信号途径与其它信号途径形成网络,调控机制精密而复杂。明确BMP-2在CSCs向心肌分化中的信号转导机制,将为临床应用CSCs治疗心肌梗塞等疾病提供理论基础。     

CD49f enhances multipotency and maintains stemness through the direct regulation of OCT4 and SOX2

CD49f (integrin subunit α6) regulates signaling pathways in a variety of cellular activities. However, the role of CD49f in regulating the differentiation and pluripotency of stem cells has not been fully investigated. Therefore, in this study, human mesenchymal stem cells (hMSCs) were induced to form spheres under nonadherent culture conditions, and we found that the CD49f-positive population was enriched in MSC spheres compared with MSCs in a monolayer. The expression of CD49f regulated the ability of hMSCs to form spheres and was associated with an activation of the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway. Furthermore, the forced expression of CD49f modulated the proliferation and differentiation potentials of hMSCs through prolonged activation of PI3K/AKT and suppressed the level of p53. We showed that the pluripotency factors OCT4 and SOX2 were recruited to the putative promoter region of CD49f, indicating that OCT4 and SOX2 play positive roles in the expression of CD49f. Indeed, CD49f expression was upregulated in human embryonic stem cells (hESCs) compared with hMSCs. The elevated level of CD49f expression was significantly decreased upon embryoid body formation in hESCs. In hESCs, the knockdown of CD49f downregulated PI3K/AKT signaling and upregulated the level of p53, inducing differentiation into three germ layers. Taken together, our data suggest that the cell-surface protein CD49f has novel and dynamic roles in regulating the differentiation potential of hMSCs and maintaining pluripotency.     

静水压刺激人骨髓间充质干细胞骨架的排列

背景：力学信号如何调节骨髓间充质干细胞分化的机制尚不清楚,细胞骨架结构变化可能在力学信号细胞内传导中起重要作用。 目的：分析静水压作用下人骨髓间充质干细胞骨架蛋白丝状肌动蛋白微丝的空间结构变化以及阻断ERK1/2信号通路或整合素α2β1后对这一过程的影响。 方法：利用加压容器对体外培养的人骨髓间充质干细胞施加40 kPa或80 kPa压强的静水压力刺激,加载时间为1 h或4 h,细胞培养也中分别加入10 mmol/LERK1/2信号通路抑制剂U0126或10 mg/L 整合素α2β1抗体以阻断细胞内ERK1/2信号通路或细胞表面整合素α2β1受体。 结果与结论：受压后骨髓间充质干细胞骨架微丝比不进行干预的细胞纤细,并且散乱分布于胞浆内、无方向性;与受压1 h相比,受压4 h的细胞骨架微丝形态、分布和排列更接近未受压组;U0126比整合素α2β1抗体更明显地阻断骨髓间充质干细胞在静水压刺激下的细胞骨架微丝重组现象。说明人骨髓间充质干细胞在静水压刺激下细胞骨架结构发生重组和重排,ERK1/2信号途径起重要作用。     

Extracellular matrix remodeling, integrin expression, and downstream signaling pathways influence the osteogenic differentiation of mesenchymal stem cells on poly(lactide-co-glycolide) substrates

The possibility of using multipotent adult bone marrow-derived mesenchymal stem cells (MSCs) for tissue-engineering applications hinges on the ability to predictably control their differentiation. Previously, we showed the osteogenic potential of adult bone marrow-derived MSCs cultured on thin films of poly(lactide-co-glycolide) (PLGA) depends in part on the identity of extracellular matrix (ECM) ligands initially deposited onto the material from serum in the culture medium. Here we have addressed the hypothesis that remodeling of the PLGA surface via the de novo synthesis of ECM proteins by the MSCs may also play an important role in governing their osteogenic differentiation. Supporting this hypothesis, increasing amounts of fibronectin and type-I collagen were synthesized and deposited onto thin-film PLGA substrates, whereas vitronectin levels diminished over a 28-day time course. Integrin expression profiles changed accordingly, with higher levels of alpha2beta1 and alpha5beta1 than alphavbeta3 at three different time points. The mitogen-activated protein kinase (MAPK) and phosphatidyl inositol-3-kinase (PI3K) pathways were also activated in MSCs cultured on these substrates, and their inhibition significantly inhibited osteogenic differentiation as assessed according to alkaline phosphatase activity and mineral deposition. These data indicate that initial ECM deposition, subsequent matrix remodeling, and corresponding integrin expression profiles influence osteogenesis in MSCs cultured on PLGA in part by engaging MAPK and PI3K signaling pathways. Understanding the mechanisms by which stem cells respond to different polymers will be critical in their eventual therapeutic use.     

Regulation of proliferation and chondrogenic differentiation of human mesenchymal stem cells by laminin-5 (laminin-332)

Laminin-5 (laminin-332) is an important basement membrane protein that regulates cell attachment and motility. Recent studies have shown that laminin-5 is expressed in human mesenchymal stem cells (MSCs) in culture and that the laminin gamma2 chain is transiently expressed in chondrocytes during development. These studies suggest that laminin-5 may be involved in the regulation of chondrogenic differentiation of MSCs. In this study, we examined a possible role of laminin-5 in the proliferation and differentiation of human MSCs. When MSCs were incubated in the presence of a coated or soluble form of laminin-5 in a growth medium, they proliferated more rapidly than nontreated cells, keeping their differentiation potential. On the other hand, laminin-5 potently suppressed the chondrogenic differentiation of MSCs. These activities were mediated mainly by integrin alpha3beta1. However, laminin-5 had no effect on the osteogenic differentiation of MSCs. These results suggest that laminin-5 may contribute to the development of bone tissues by promoting the proliferation and by suppressing the chondrogenic differentiation of MSCs.     

Uncoupling integrin adhesion and signaling: the betaPS cytoplasmic domain is sufficient to regulate gene expression in the Drosophila embryo

Integrin cell surface receptors are ideally suited to coordinate cellular differentiation and tissue assembly during embryogenesis, as they can mediate both signaling and adhesion. We show that integrins regulate gene expression in the intact developing embryo by identifying two genes that require integrin function for their normal expression in Drosophila midgut endodermal cells. We determined the relative roles of integrin adhesion versus signaling in the regulation of these integrin target genes. We find that integrin-mediated adhesion is not required between the endodermal cells and the surrounding visceral mesoderm for integrin target gene expression. In addition, a chimeric protein that lacks integrin-adhesive function, but maintains the ability to signal, can substitute for the endogenous integrin and regulate integrin target genes. This chimera consists of an oligomeric extracellular domain fused to the integrin betaPS subunit cytoplasmic domain; a control monomeric extracellular domain fusion does not alter integrin target gene expression. Therefore, oligomerization of the 47-amino-acid betaPS intracellular domain is sufficient to initiate a signaling pathway that regulates gene expression in the developing embryo.     

Notch和Wnt信号通路对神经干细胞增殖分化的影响

Notch和Wnt信号通路是调节神经干细胞(neural stem cells,NSCs)增殖、分化的重要通路,Notch信号通路的靶基因Hes1、Hes5及HES相关蛋白等分化抑制信号,通过旁侧抑制机制阻止NSCs的分化,并促进其自我更新;通过NICD与CSL DNA结合蛋白的直接结合,形成GFAP的转录激活复合物,上调GFAP的表达,从而促进NSCs向星形胶质细胞的分化。Wnt信号通过Wnt/β-catenin信号通路对细胞周期素D1和D2的转录调节,调控NSCs细胞周期的进程,使其量增殖;然而,过表达的Wnt3a和Wnt7a蛋白能够抑制NSCs的增殖,促进NSCs向神经元方向分化。     

VIP differentially activates beta2 integrins, CR1, and matrix metalloproteinase-9 in human monocytes through cAMP/PKA, EPAC, and PI-3K signaling pathways via VIP receptor type 1 and FPRL1

The neuropeptide vasoactive intestinal peptide (VIP) regulates the exocytosis of secretory granules in a wide variety of cells of neuronal and non-neuronal origin. In human monocytes, we show that the proinflammatory effects of VIP are associated with stimulation of exocytosis of secretory vesicles as well as tertiary (gelatinase) granules with, respectively, up-regulation of the membrane expression of the beta2 integrin CD11b, the complement receptor 1 (CD35), and the matrix metalloproteinase-9 (MMP-9). Using the low-affinity formyl peptide receptor-like 1 (FPRL1) antagonist Trp-Arg-Trp-Trp-Trp-Trp (WRW4) and the exchange protein directly activated by cAMP (EPAC)-specific compound 8CPT-2Me-cAMP and measuring the expression of Rap1 GTPase-activating protein as an indicator of EPAC activation, we found that the proinflammatory effect of VIP is mediated via the specific G protein-coupled receptor VIP/pituitary adenylate cyclase-activating protein (VPAC1) receptor as well as via FPRL1: VIP/VPAC1 interaction is associated with a cAMP increase and activation of a cAMP/p38 MAPK pathway, which regulates MMP-9, CD35, and CD11b exocytosis, and a cAMP/EPAC/PI-3K/ERK pathway, which regulates CD11b expression; VIP/FPRL1 interaction results in cAMP-independent PI-3K/ERK activation with downstream integrin up-regulation. In FPRL1-transfected Chinese hamster ovary-K1 cells lacking VPAC1, VIP exposure also resulted in PI-3K/ERK activation. Thus, the proinflammatory effects of VIP lie behind different receptor interactions and multiple signaling pathways, including cAMP/protein kinase A, cAMP/EPAC-dependent pathways, as well as a cAMP-independent pathway, which differentially regulates p38 and ERK MAPK and exocytosis of secretory vesicles and granules.