小鼠胚胎干细胞自我更新的信号调控机制

小鼠胚胎干细胞是一种全能干细胞，具有体内体外全能分化特性。体外培养时能够进行自我更新，即细胞通过对称分裂在维持全能性不丢失的情况下细胞数目增多。全能性维持受多条信号通路的调控，其中gp130下游的JAK-STAT3及P13K通路的活化能维持胚胎干细胞的自我更新，而SHP2-Ras-ERK的激活则促使胚胎干细胞分化。无血清条件下BMP4激活的通路与JAK-STAT3联合作用可保持胚胎干细胞的全能性。此外，Wnt信号通路的活化也参与对胚胎干细胞的自我更新的调控。总之，多种信号通路形成的网络精确调控小鼠胚胎干细胞的自我更新与分化。本文主要综述gp130在小鼠ES细胞增殖过程中作用，包括JAK-STAT3通路活化抑制小鼠ES细胞分化，P13K通路活化维持ES细胞的自我更新和SHP-2-Ras通路活化促进ES细胞分化，以及其他信号通路对小鼠ES细胞自我更新的影响，包括无血清条件下BMP联合LIF能维持ES细胞的高度自我更新，Wnt信号通路活化促进ES细胞自我更新。     

Inactivation of Wnt/β-catenin signaling in human adipose-derived stem cells is necessary for chondrogenic differentiation and maintenance

The Wnt/β-catenin signaling pathway plays critical roles in self-renewal and differentiation of mesenchymal stem cells. However, very little is known about its role in the chondrogenesis of human adipose-derived stem cells (hADSCs). In this study, we analyzed protein expression of several key components of the Wnt/β-catenin signaling pathway using a 21-day in vitro model of hADSC chondrogenesis. Wnt1, β-catenin, and GSK3β levels increased sharply at day 12, peaked at day 18, and then declined. Expression of TCF1, a target gene of Wnt/β-catenin signaling, closely followed that of Wnt1. These results were consistent with changes in endonuclear β-catenin levels. Gene expression of the chondrocyte-specific markers, collagen type II (COL II), SOX9, and aggrecan, increased during hADSC chondrogenesis, peaked at day 12, and then declined. Adding a Wnt inhibitor (days 0–21) resulted in consistently elevated levels of COL II, SOX9, and aggrecan mRNA. In contrast, adding Wnt1 (days 0–21) to cultures led to sustained Wnt/β-catenin signaling over the 21 days and suppressed expression of chondrocyte-specific markers. Moreover, adding Wnt1 at late stages of differentiation (day 18) further diminished chondrocyte-specific marker expression. Together, these results showed that inactivation of Wnt/β-catenin signaling is needed for the progression of chondrogenesis and the maturation and phenotype maintenance of chondroid cells.     

Derivation of sarcomas from mesenchymal stem cells via inactivation of the Wnt pathway

Malignant fibrous histiocytoma (MFH), now termed high-grade undifferentiated pleomorphic sarcoma, is a commonly diagnosed mesenchymal tumor, yet both the underlying molecular mechanisms of tumorigenesis and cell of origin remain unidentified. We present evidence demonstrating that human mesenchymal stem cells (hMSCs) are the progenitors of MFH. DKK1, a Wnt inhibitor and mediator of hMSC proliferation, is overexpressed in MFH. Using recombinant proteins, antibody depletion, and siRNA knockdown strategies of specific Wnt elements, we show that DKK1 inhibits hMSC commitment to differentiation via Wnt2/beta-catenin canonical signaling and that Wnt5a/JNK noncanonical signaling regulates a viability checkpoint independent of Dkk1. Finally, we illustrate that hMSCs can be transformed via inhibition of Wnt signaling to form MFH-like tumors in nude mice, and conversely, MFH cells in which Wnt signaling is appropriately reestablished can differentiate along mature connective tissue lineages. Our results provide mechanistic insights regarding the cell of origin of MFH, establish what we believe is a novel tumor suppressor role for Wnt signaling, and identify a potential therapeutic differentiation strategy for sarcomas.     

杜仲醇提取物诱导骨髓间充质干细胞成骨分化中的Wnt信号途径

背景：近年来,中药及中药有效部分对骨质疏松的干预和治疗作用的报道较多,但涉及细胞成骨分化调控的信号途径的报道较少。目的：观察杜仲诱导大鼠骨髓问充质干细胞成骨分化过程中Wnt信号途径相关基因表达的变化。方法：将第3代SD大鼠骨髓间充质干细胞,接种到6孔培养板中,每孔1×10^3个细胞,24h后更换诱导培养基（含体积分数为7.5％胎牛血清的DMEM／F12（1：1）加1／1000浓度的杜仲醇提取物）。阴性对照组仍为正常培养基培养。诱导8h,1d,3d和7d时采用RT-qPCR法测定Wnt信号途径巾Fzd和LRP受体系列、β-catenin、核内Wnt调控靶基因系列及Wnt抑制因予（WIF1）等表达变化。结果与结论：与阴性对照组比较,诱导3d后Fzd2表达升高11．86倍,Fzd3升高达到2倍;诱导7d后,Fzd2表达升高5．12倍,Fzd3恢复到正常水平：β-catenin在诉导3d时表达升高达2倍：WIF1在诱导3d和7d后表达显著下降。结果提示Wnt信号途径可能参与了杜仲促骨髓间充质干细胞成骨分化过程。     

Small molecules in stem cell self-renewal and differentiation

The use of stem cells in regenerative medicine is a promising approach to the treatment of disease and injury. Natural and synthetic small molecules have been shown to be useful chemical tools for controlling and manipulating the fates of cells. Small molecules can target signaling transduction pathways (for example, tyrosine kinase receptors) and affect DNA replication, cell differentiation, tumor metastasis and apoptosis. Stem cells share many properties with cancer cells and these similarities can provide insights to control and direct cell behavior; small molecules are already standard chemotherapeutics in the treatment of cancer. Libraries of small molecules have been examined for anticancer behavior (especially apoptosis), and, more recently, for stem cell self-renewal and differentiation capabilities in potential approaches to regenerative medicine. Differentiation therapy for cancer is based on the idea that cancer cells are undifferentiated embryonic-like cells and proposes to promote the differentiation and hence block cell proliferation. For example, retinoids have a role in stem cell differentiation to several lineages and have also been used to promote differentiation of acute promyeloic leukemic cells. Small molecules are also important tools for understanding mechanistic and developmental processes. Strategies for generating functional small molecule libraries have been outlined previously. In this review, we will look at several small molecules that have been described in the recent literature as effectors of stem cell self-renewal or differentiation as associated with the Wnt, Hedgehog or NF-kappaB pathways.     

葛根素干预激素诱导骨髓间充质干细胞成脂分化的Wnt信号途径

背景：国内外学者研究证明,激素性股骨头缺血性坏死的发病机制与体内脂质代谢紊乱,尤其是大剂量激素诱导下骨髓间充质干细胞的成脂分化有关。目前葛根素抑制激素诱导骨髓间充质干细胞成脂分化的Wnt信号转导途径还未经证实。〈br〉 目的：观察葛根素干预激素诱导大鼠骨髓间充质干细胞成脂分化过程中 Wnt 信号途径相关基因及关键蛋白β-catenin表达的变化。〈br〉 方法：第3代SD大鼠骨髓间充质干细胞随机分为空白组、激素组、葛根素低、中、高剂量组,5组干预6 d后RT-PCR法检测Wnt/β-catenin信号通路主要成员Wnt10b mRNA、GSK3β mRNA、β-catenin mRNA的表达,Western blot法对β-catenin蛋白的表达进行检测分析。〈br〉 结果与结论：与激素组比较,葛根素各干预组Wnt10b mRNA、β-catenin mRNA及β-catenin蛋白的表达水平均显著升高;GSK3βmRNA的表达水平显著降低。提示葛根素对激素诱导骨髓间充质干细胞成脂分化的抑制作用可能是通过调节信号通路的Wnt10b mRNA、GSK3βmRNA、β-catenin mRNA及β-catenin蛋白的表达来实现的。葛根素防治激素性股骨头缺血坏死的机制不仅是改善股骨头局部的微循环,同时还与其抑制激素诱导下骨髓间充质干细胞的成脂分化有关。     

Wnt/β-catenin signaling may be involved with the maturation,but not the differentiation,of insulin-producing cells

Wnt/β-catenin signaling (WNT) has widespread roles during stem cell differentiation. Whether WNT suppresses or promotes insulin-producing cell (IPC) differentiation and function is still not known. In this study, we investigated the role of WNT signaling during human adipose-derived stem cell (hADSC) differentiation into IPCs. Western blot analysis revealed that several key components of WNT were dynamically regulated in a 12-day IPC differentiation assay. Specifically, protein levels of Wnt1, β-catenin, and GSK3β steadily increased from day 0 to day 9 and rapidly decreased by day 12 of differentiation. Similarly, endonuclear β-catenin levels peaked at day 9 and then, fell to pre-differentiation levels. The expression of two WNT pathway targets, TCF-1 and cyclin D1, closely followed the same pattern of regulation, confirming that WNT signaling was transiently activated during IPC differentiation. Interestingly, the inhibition of WNT signaling did not block IPC differentiation; instead, it resulted in the upregulation of IPC-specific markers, including PDX-1, insulin, IRS-1, and IRS-2. Notably, another IPC marker, glucokinase, remained downregulated since it is a direct target of WNT signaling. Next, we examined the effect of maintaining active WNT signaling from day 9 to day 12 of IPC differentiation. Differentiating cells were treated with Wnt1 on day 9, when WNT signaling is typically turned off, and subjected to gene expression analysis on day 12. Remarkably, Wnt1 treatment resulted in reduced expression of IPC-specific markers. Taken together, these data indicate that WNT may not be necessary for IPC differentiation but may be involved in IPC maturation.     

体外培养大鼠骨髓间充质干细胞向神经元样细胞分化:Wnt3a信号分子的诱导作用

背景:Wnt信号通路是细胞增殖分化的关键调控环节.已有证据显示此通路参与了对神经前体细胞增殖、分化以及决定细胞命运的调控.目前有关Wnt信号通路对间充质干细胞向神经元样细胞分化的作用还少见报道.目的:寻找促进间充质干细胞向神经元样细胞分化的Wnt信号分子.方法:采用密度梯度离心法在体外分离培养SD大鼠股骨间充质干细胞并培养.传代后通过形态学和流式细胞学检测细胞表面标志物CD29、CD44、CD34、CD45,筛选并鉴定培养细胞.采用神经营养因子碱性成纤维细胞生长因子分别联合Wnt3a和Wnt5a诱导方案,通过免疫组化和RT-PCR的方法比较Wnt3a、Wnt5a在间充质干细胞向神经元样细胞分化过程中的作用,以碱性成纤维细胞生长因子单独培养为对照.结果与结论:间充质干细胞经培养、传代后,细胞贴壁生长,形态均一,呈长梭形,流式细胞学检测细胞表面标志物CD29、CD44高表达,CD34、CD45低表达.Wnt3a诱导后细胞巢蛋白、神经元特异性烯醇化酶呈阳性,胶质纤维酸性蛋白无明显表达,诱导后细胞的活力良好;Wnt5a诱导组及对照组巢蛋白呈弱阳性表达,神经元特异性烯醇化酶及胶质纤维酸性蛋白阴性.RT-PCR结果显示,Wnt3a诱导组巢蛋白在诱导前后均有表达,神经元特异性烯醇化酶在诱导后5d可见明显的扩增条带,10d后更加明显;胶质纤维酸性蛋白在诱导10d后有比较弱的扩增条带出现.结果说明Wnt3a分子能够促进体外培养的间充质干细胞向神经元样细胞分化.     

持续 Wnt 信号通路激活促进胚胎干细胞源造血干细胞的增殖简

背景：如何提高胚胎干细胞诱导效率、促进胚胎干细胞源造血干细胞体外增殖成为目前急需解决的课题。目的：以外源性Wnt3a作为诱导剂,激活培养中的小鼠胚胎干细胞Wnt/β-catenin信号通路,观察该通路的激活是否促进胚胎干细胞向造血祖细胞的定向分化。方法：用外源性wnt3a（100μg/L）持续作用ES-E14TG2a小鼠胚胎干细胞21 d,通过细胞免疫荧光及蛋白免疫印迹检测细胞内β-catenin蛋白含量,QRT-PCR检测Wnt下游靶标基因的表达量来确定经典Wnt/β-catenin信号通路是否被激活,然后采用单层贴壁培养法诱导其向造血干细胞分化,流式细胞仪检测造血发育相关表面标志CD34＋/Sca-1＋,同时以QRT-PCR法检测造血相关基因的表达情况。结果与结论：ES-E14TG2a小鼠胚胎干细胞经wnt3a（100μg/L）连续培养21 d后发现β-catenin蛋白在细胞内积累;Wnt信号通路的下游靶标基因Pitx2、Frizzled、Sox17、Oct4的表达量均出现不同程度的增加,可见经典 Wnt/β-catenin 信号通路有被激活;单层贴壁培养法诱导其向造血干细胞分化的过程中检测到CD34＋/Sca-1＋细胞含量在14 d时占总细胞量高达20.2%,而对照组的仅占11.9%。造血相关基因骨形态发生蛋白4、FLK2及CD34的表达量均增加,而Smad5的表达则明显受到抑制。说明Wnt3a持续作用可激活Wnt/β-catenin信号通路,并促进ES-E14TG2a小鼠胚胎干细胞向造血干细胞的定向分化。     

高压氧对大鼠骨髓间充质干细胞分化和Wnt3表达的影响

背景:高压氧治疗可以促进缺氧缺血性脑损伤新生大鼠内源性神经干细胞的增殖和分化,且其机制与Wnt信号通路的活化有关,但在体外高压氧对干细胞分化的影响是否也通过Wnt信号通路起作用目前尚未见相关报道.目的:观察高压氧对大鼠骨髓间充质干细胞分化的影响,认识其相关机制.方法:全骨髓法分离培养大鼠骨髓间充质干细胞,贴壁纯化,取传至第3～5代细胞,加入含bFGF,EGF,B27的DMEM/F12培养基诱导培养24 h.诱导后细胞随机分为2组,对照组未做任何处理,高压氧组给予0.10 MPa的压力治疗,稳压时间60min,稳压期间平均氧浓度不低于90%.免疫荧光染色检测巢蛋白、NSE,GFAP,04等抗体的表达,Western-blot法检测Wnt3蛋白的表达.结果与结论:骨髓间充质干细胞用神经干细胞经典培养基诱导后巢蛋白呈阳性表达.与对照组比较,高压氧组NSE,04阳性细胞分化率均最著增加(P＜0.01),GFAP阳性细胞分化率无明显差异(P＞0.05),Wnt3蛋白的表达明显升高(P＜0.05).高压氧可以促进骨髓间充质干细胞向神经元细胞和少突胶质细胞分化,但对星形胶质细胞的分化无明显影响,其机制可能与Wnt3蛋白的活化有关.     

阿尔茨海默病现Wnt信号通路及神经干细胞的关系

背景：阿尔茨海默病的病因涉及遗传、环境、免疫等多种因素和机制,大量研究表明Wnt信号通路与之密切相关,也有研究表明,Wnt信号通路对神经干细胞的增殖发挥着决定性作用.目的：对阿尔茨海默病的病理过程与Wnt 信号通路的关系以及 Wnt 信号通路与神经干细胞增殖分化进行综述,为阿尔茨海默病的治疗提供理论依据.方法：通过Pubmed数据库检索有关阿尔茨海默病病理过程与Wnt信号通路及Wnt信号通路与神经干细胞关联的相关文献,检索词为“Alzheimer’s disease、Wnt signaling pathway、NSCs、stem cel differentiation、amyloid-βprotein、Protein Tau”.纳入与阿尔茨海默病和Wnt信号通路相关的文献,排除重复性研究,保留50篇文献进行综述.结果与结论：目前通过神经干细胞移植来治疗以神经元的缺失为特征的神经退行性疾病已成为研究的热点,而如何调控神经干细胞向特定神经元分化成为了研究的难点,信号转导在神经干细胞的分化中起重要的作用,其中Wnt信号通路是调节神经干细胞增殖及分化的细胞外的重要因素.Wnt信号通路的失活可以促进阿尔茨海默病的病理过程,相反激活Wnt信号通路可以保护海马神经元,同时促进神经干细胞的分化,为阿尔茨海默病的治疗提供新的思路.     

Characterization of a GSK-3 inhibitor in culture of human cord blood primitive hematopoietic cells

Wnt signaling pathway plays important roles in the biology of stem cells in maintaining their self-renewal property. Glycogen synthase kinase-3 (GSK-3) inhibitors, the Wnt signaling agonists, maintain the pluripotency of embryonic stem cells. We report here that a synthetic GSK-3 inhibitor, 6-bromoindirubin-3′-oxime (BIO), showed opposite effects on the expansion of human primitive hematopoietic cells isolated from umbilical cord blood (UCB). In combination with human c-kit ligand (KL), BIO at low concentration (0.2 μM) enhanced the expansion of UCB CD34⁺ cells, which was BIO structure and exposure time dependent; however, at high concentration (2 μM) it inhibited the expansion of the cells. Furthermore, hematopoietic stem cells (HSCs) were exhausted when the UCB CD34⁺ cells were exposed to 0.2 μM BIO and KL longer than 2 days. In conclusion, the use of BIO in expansion of UCB HSCs remains a significant challenge.     

Musashi-1在妇科恶性肿瘤发生发展中的作用

妇科恶性肿瘤严重威胁女性健康,尽管目前治疗策略相对有效,但复发及耐药仍是影响整体生存率的重要因素。研究表明肿瘤的复发及耐药与具有自我更新、无限增殖、多向分化潜能及高致瘤性的肿瘤干细胞(cancer stem cells,CSCs)亚群密切相关。Musashi-1是一种最新研究报道的CSCs标志物,多数研究认为其通过Notch、Wnt等信号通路发挥作用,在多种肿瘤组织中异常表达,在妇科恶性肿瘤中高表达,且与肿瘤的分期、分化、血管浸润及化学药物治疗耐药等密切相关。深入研究其在妇科恶性肿瘤中的作用机制,可为妇科恶性肿瘤的临床治疗提供新思路。现就Musashi-1在妇科恶性肿瘤中的表达情况及作用机制进行综述。     

Phosphatase WIP1 regulates adult neurogenesis and WNT signaling during aging

The number of newly formed neurons declines rapidly during aging, and this decrease in neurogenesis is associated with decreased function of neural stem/progenitor cells (NPCs). Here, we determined that a WIP1-dependent pathway regulates NPC differentiation and contributes to the age-associated decline of neurogenesis. Specifically, we found that WIP1 is expressed in NPCs of the mouse subventricular zone (SVZ) and aged animals with genetically enhanced WIP1 expression exhibited higher NPC numbers and neuronal differentiation compared with aged WT animals. Additionally, augmenting WIP1 expression in aged animals markedly improved neuron formation and rescued a functional defect in fine odor discrimination in aged mice. We identified the WNT signaling pathway inhibitor DKK3 as a key downstream target of WIP1 and found that expression of DKK3 in the SVZ is restricted to NPCs. Using murine reporter strains, we determined that DKK3 inhibits neuroblast formation by suppressing WNT signaling and Dkk3 deletion or pharmacological activation of the WNT pathway improved neuron formation and olfactory function in aged mice. We propose that WIP1 controls DKK3-dependent inhibition of neuronal differentiation during aging and suggest that regulating WIP1 levels could prevent certain aspects of functional decline of the aging brain.     

A genome-wide RNAi screen in mouse embryonic stem cells identifies Mp1 as a key mediator of differentiation

Despite intense investigation of intrinsic and extrinsic factors that regulate pluripotency, the process of initial fate commitment of embryonic stem (ES) cells is still poorly understood. We used a genome-wide short hairpin RNA screen in mouse ES cells to identify genes that are essential for initiation of differentiation. Knockdown of the scaffolding protein Mek binding protein 1 (Mp1, also known as Lamtor3 or Map2k1ip1) stimulated self-renewal of ES cells, blocked differentiation, and promoted proliferation. Fibroblast growth factor 4 (FGF4) signaling is required for initial fate commitment of ES cells. Knockdown of Mp1 inhibited FGF4-induced differentiation but did not alter FGF4-driven proliferation. This uncoupling of differentiation and proliferation was also observed when oncogenic Ras isoforms were overexpressed in ES cells. Knockdown of Mp1 redirected FGF4 signaling from differentiation toward pluripotency and up-regulated the pluripotency-related genes Esrrb, Rex1, Tcl1, and Sox2. We also found that human germ cell tumors (GCTs) express low amounts of Mp1 in the invasive embryonic carcinoma and seminoma histologies and higher amounts of Mp1 in the noninvasive carcinoma in situ precursor and differentiated components. Knockdown of Mp1 in invasive GCT cells resulted in resistance to differentiation, thereby showing a functional role for Mp1 both in normal differentiation of ES cells and in germ cell cancer.     

Progesterone signaling/miR-200a/zeb2 axis regulates self-renewal of mouse embryonic stem cells

Progesterone is a steroid hormone and plays an important role during pregnancy. But the regulation mechanisms of progesterone-progesterone receptor (P4-PR) signaling during pregnancy remain largely unknown. In this study, we used medroxyprogesterone 17-acetate (MPA) which is a synthetic variant of progesterone and has 20–30 times the activity of progesterone to find that at the same physiological concentration as progesterone during early pregnancy MPA had no significant influence on ES cells self-renewal. But with the increasing of dosage, MPA can inhibit the self-renewal capacity of mouse embryonic stem cells (ES cells) and promote differentiation untimely. We further determined that MPA can influence the miR-200a/zeb2 pathway by down regulating the level of miR-200a. miR-200a significantly higher expressed in ES cells to down-regulate the expression of zeb2 to inhibit the self-renewal and promote differentiation of ES cells. Then we found that the function of MPA can be rescued by over-expression of miR-200a or down-regulation of zeb2. Our findings revealed the progesterone signaling/miR-200a/zeb2 axis regulating the progesterone signaling to insure the balance of self-renewal and differentiation of ES cells. Our study also provided new insight into the dosage of progesterone and it's derivant in the hormone replacement therapy for pregnant woman.