MiR-125a-5p靶向APC激活经典WNT信号通路促进hiPSCs分化为多巴胺能神经前体细胞

目的通过调节miR-125a-5p的表达实现人诱导性多能干细胞(hiPSCs)向多巴胺(DA)能神经前体细胞及DA能神经元的高效转化。方法应用MicroRNAs高通量测序与分析,miR-125a-5p的筛选、靶基因(APC)的预测与验证;miR-125a-5p前体miR-125a慢病毒载体的构建与包装,miR-125a-5p过表达hiPSCs细胞株的构建、筛选及其向多DA能神经前体细胞与DA能神经元的诱导分化;免疫细胞化学、实时定量PCR(qRT-PCR)及蛋白印迹(WB)法检测miR-125a-5p过表达hiPSCs与对照hiPSCs向DA能神经前体细胞及DA能神经元诱导分化过程中神经前体细胞标志物Nestin、底板细胞标志物Foxa2、DA能神经前体细胞标志物En1、DA能神经前体细胞分选标志物Corin、神经元标志物Tuj1及DA能神经元标志物TH的表达。结果 MiR-125a-5p在hiPSCs向DA能神经前体细胞及神经元诱导分化过程中的表达呈递增趋势,miR-125a-5p靶向调节经典WNT信号通路关键因子APC,稳定过表达miR-125a-5p的hiPSCs细胞株能向DA能神经前体细胞及DA能神经元分化,其诱导分化效率与对照hiPSCs相比在神经前体细胞(NPCs)阶段FOXA2、EN1、CORIN的表达明显增高,神经元阶段TH、DAT和Nurr1的表达明显增高,提示过表达miR-125a-5p的hiPSCs具有更好的向DA能神经前体细胞及DA能神经元的诱导分化潜能。结论 MiR-125a-5p能通过靶向下调APC的表达激活经典WNT信号通路活性,促进hiPSCs向DA能神经前体细胞及DA能神经元的诱导分化。     

干扰miR-31表达初期Notch和Hedgehog信号通路相关基因在神经干细胞中的表达变化

目的:研究干扰miR-31表达初期Notch和Hedgehog信号通路相关基因在神经干细胞(NSCs)中的表达变化。方法:利用荧光定量PCR对干扰miR-31表达初期Notch和Hedgehog信号通路相关基因在NSCs中的表达变化进行研究。结果:干扰与过表达miR-31后3 d,NSCs中的Notch信号通路相关基因Notch2的表达均增加,Jag2、Dll3和Hes1等的表达均降低;Hedgehog信号通路相关基因Wnt3的表达均增加,Bmp5与Wnt7a的表达均降低。结论:影响miR-31的表达可引发NSCs发生分化,在此过程中Notch与Hedgehog信号通路中几个基因的表达都产生相应改变,表明miR-31与NSCs分化过程相关。     

定向诱导人尿液细胞源性多能干细胞向多巴胺能神经元的分化

目的探讨定向诱导人尿液来源诱导性多能干细胞(U-iPS)向多巴胺(DA)能神经元分化。方法单层贴壁法体外培养U-iPS,通过时向性添加TGF-β及BMP信号通路抑制剂,SHH细胞因子,GSK3β抑制剂Chir99021将U-iPS诱导为DA能神经前体细胞(NPCs),通过添加BDNF/GDNF等细胞因子将其进一步分化为DA能神经元。在诱导分化的4个时间点(第0天、7天、14天及25天)采用RT-qPCR和免疫荧光检测多能干细胞标志物Oct4与Nanog的表达;NPCs标志物Nestin、Pax6和Foxa2的表达;DA神经前体细胞标志物Lmx1a和En1的表达;神经元标志物Tuj1的表达以及DA能神经元标志物TH的表达情况。以人皮肤成纤维细胞来源的iPS(F-iPS)向DA能神经元的诱导分化作为对照进行分化效率的比较。结果 U-iPS在第0天表达多能干标志物Oct4和Nanog;诱导第7天能转化为Nestin、Pax6及Foxa2阳性的NPCs;第14天转化为Lmx1a和En1阳性的DA能神经前体细胞;第25天分化得到的神经元样细胞表达神经元标志物Tuj1,其中部分细胞表达DA能神经元标志物TH。各时间点神经类细胞标志物的表达与F-iPS诱导分化得到的神经类细胞标志物的表达差异无统计学意义(P0.05)。结论 U-iPS细胞具有向DA能神经元分化的潜力,能在体外经过诱导分化得到TH阳性的DA能神经元,且与F-iPS向DA能神经元分化的效率无明显差异。     

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。     

小鼠脑皮质神经干细胞体外培养及miRNAs影响其分化能力

目的系统建立小鼠脑皮质神经干细胞(NSCs)体外培养的技术平台,并探索一组microRNA对NSCs分化能力的影响。方法胎鼠(E14)脑皮质分离NSCs进行体外培养;免疫荧光法检测NSCs向神经元和星型胶质细胞的自然分化;Real-time定量PCR筛选一组分化前后表达水平有显著性差异的microRNA;应用新一代脂质体高效转染NSCs,将该组microRNA或其抑制物导入NSCs;Western blot检测导入的RNA序列对NSCs分化能力的影响。结果基于小鼠NSCs体外培养模型,筛选出一组NSCs分化前后表达水平存在显著性差异的microRNA(miR-124,137,128)。Western blot结果显示miR-124的反义链能够明显下调β-tubulinⅢ的表达(P<0.01),过表达miR-137和miR-128后β-tubulinⅢ的表达量有所升高。结论脂质体转染技术能够将miRNAs高效导入NSCs中;microRNA-124,137,128能够影响NSCs的分化。     

小鼠胚胎干细胞来源的神经干细胞的稳定传代体系探索

目的探讨体外诱导、获取均一的神经干细胞群(NSCs)的有效方法,并建立神经干细胞体外稳定传代扩增体系。方法首先采用无血清的诱导培养基贴壁诱导mESCs形成神经上皮祖细胞(NPCs)。然后将经添加表皮生长因子(EGF)和成纤维细胞生长因子-2(FGF2)的无血清培养基短暂悬浮培养后的NPCs再贴壁培养,诱导形成NSCs。通过细胞系46C监测NPCs的形成,同时对分化细胞进行定量PCR和免疫荧光染色,在不同水平检测细胞分化效果。结果 mESCs神经诱导5 d出现大量Sox1+的NPCs;NPCs悬浮培养后,进一步诱导可得到形态均一的NSCs。第2代和第6代NSCs的神经干细胞标志定量PCR检测结果为:Pax6、Nestin、Mash1、BLBP高表达。第8代NSCs免疫荧光染色显示90%以上的细胞均为Nestin、RC2和Pax6阳性。结论成功诱导mESC生成神经干细胞群,并且可以在体外连续稳定的传代。     

颅脑手术患者废弃脑组织中神经干细胞的培养与鉴定

目的:研究颅脑手术患者废弃脑组织中神经干细胞的培养与鉴定,为立体定向自体神经干细胞移植治疗脑出血、脑梗塞及颅脑损伤后遗症提供临床前基础。方法:通过改进原代培养方法,从颅脑手术患者废弃脑组织中培养和鉴定神经干细胞(NSCs)。收集颅脑手术患者不同脑区废弃脑组织各约500 mg以上,按改良方法进行原代培养并传代,通过免疫荧光检测NSCs标志物巢蛋白(Nestin)的表达,传代培养5代时开始进行诱导分化。结果:培养约3～10 d后,多数患者废弃脑组织中均可见干细胞球生长,经Nestin免疫荧光检测均呈阳性表达。选取第6代诱导分化后的贴壁细胞分别经β-Tubulin(神经元标志物)、Sox10(少突胶质细胞标志物)与GFAP(星形胶质细胞标志物)免疫荧光检测,可见少量神经元、少突胶质细胞及星形胶质细胞阳性表达。取第3代与第6代细胞行免疫印迹鉴定,第3代细胞仅见Nestin与少量β-Tubulin表达,第6代细胞可见不同程度的Nestin、β-Tubulin、Sox10及GFAP等表达。结论:本研究成功从颅脑手术患者不同脑区废弃脑组织中分离培养获得成人NSCs,并可向神经元及神经胶质细胞分化,使立体定向自体神经干细胞移植促进神经功能修复从实验室到临床应用成为可能。     

人诱导性多能干细胞定向分化为神经干细胞的实验研究

目的 观察人诱导性多能干细胞（iPS细胞）定向分化为神经干细胞（NSCs）的潜能。方法 用维甲酸（RA）诱导人iPS细胞向NSCs分化。倒置显微镜下观察iPS细胞的形态变化,RT-PCR检测NANOG, OCT4, SOX2的表达;免疫组织化学方法检测NESTIN、SOX2、β-TUBULIN Ш和GFAP的表达。结果RA诱导后第4天,贴壁的拟胚体出现了早期神经祖细胞特有的神经管样结构并不断增多,细胞表达神经巢蛋白NESTIN,而对照组未观察到神经管样结构。神经管样结构内的细胞能分化为β-TUBULIN Ш阳性的神经元,但GFAP阳性的星形胶质细胞少见。结论 人iPS细胞具有定向分化为NSCs的潜能,并能模拟神经发育过程。     

体外诱导恒河猴骨髓基质细胞分化为神经细胞的分化条件

目的比较血清维甲酸(retinoic acid,RA)、胶质细胞源神经营养因子(glial cell line-derived neurotrophic factor,GDNF)及脑源性神经营养因子(brain derived neurotrophic factor,BDNF)等在不同浓度诱导条件下使恒河猴骨髓基质细胞(bone marrow stromal cells)诱导分化为神经干细胞(NSCs)及成熟神经细胞的分化条件。方法用Nestin、CD133抗体免疫细胞化学染色,鉴定NSCs;用NSE、β-tublin鉴定神经元;用GFAP鉴定神经胶质细胞,膜片钳检测分化成熟细胞的电生理特性。结果培养第8天多数细胞表现出Nestin及CD133抗原阳性,即为NSCs细胞;诱导后3天即有神经元样细胞出现,此后神经元样细胞逐渐增多,膜片钳检测发现这些细胞具有类似神经细胞的电生理特性。同时,与其他培养条件相比较,低浓度血清(2．5％) RA GDNF组诱导分化效能最高。结论应用RA GDNF及配合使用低浓度血清能够高效诱导骨髓源NSCs向成熟神经细胞分化。     

转化生长因子β1对缺氧诱导的神经干细胞损伤的保护作用

目的:观察转化生长因子β1(transforming growth factor beta 1,TGF-β1)对缺氧诱导的神经干细胞(neural stem cells,NSCs)损伤是否具有保护作用。方法:取新生1 d的大鼠大脑皮质,进行NSCs的分离、培养、传代、诱导分化和鉴定。以三气培养箱(94%N2、5%CO2、1%O2)制备NSCs的缺氧损伤模型。取传代细胞,随机分为4组:正常对照组、三气缺氧组、溶剂对照组、生长因子组。各组细胞在相应时间点用Hoechst33258进行荧光染色,镜下观察、拍照,计算Hoechst染色阳性细胞率,评估三气培养对NSCs的损伤情况以及TGF-β1对这种损伤的保护作用。结果:在未诱导分化前,传代培养的细胞呈Nestin免疫反应阳性;用胎牛血清(fetal bovie serum,FBS)诱导分化后则分别呈Ⅲ型β-微管蛋白(typeⅢbeta tubulin,Ⅲβ-tubulin)和胶质原纤维酸性蛋白(glial fibrillary acid protein,GFAP)免疫反应阳性,表明分离到的细胞是神经干细胞。Hoechst33258染色显示,凋亡细胞呈强亮蓝色荧光;正常细胞弥漫均匀着色,无强荧光。与正常对照组相比,三气缺氧组的凋亡阳性细胞显著增多(P0.05)。与三气缺氧组或溶剂对照组相比,生长因子组的Hoechst33258染色凋亡阳性细胞数显著减少(P0.05),但仍明显多于正常对照组(P0.05)。结论:TGF-β1能够显著减少三气培养法所诱导的NSCs的凋亡,提示TGF-β1对NSCs的缺氧损伤具有重要的保护作用。为深入研究TGF-β1在NSCs的相关临床应用中的潜在价值提供理论基础和实验依据。     

Immunology of stem cells and cancer stem cells

The capacity of pluri-potent stem cells to repair the tissues in which stem cells reside holds great promise in development of novel cell replacement therapeutics for treating chronic and degenerative diseases. However, numerous reports show that stem cell therapy, even in an autologous setting, triggers lymphocyte infiltration and inflammation. Therefore, an important question to be answered is how the host immune system responds to engrafted autologous stem cells or allogeneous stem cells. In this brief review, we summarize the progress in several related areas in this field, including some of our data, in four sections： （1） immunogenicity of stem cells; （2） strategies to inhibit immune rejection to allograft stem cells; （3） immune responses to cancer stem cells; and （4） mesenchymal stem cells in immune regulation. Improvement of our understanding on these and other aspects of immune system-stem cell interplay would greatly facilitate the development of stem cell-based therapeutics for regenerative purposes. Cellular ＆ Molecular Immunology.     

Mesenchymal-like stem cells derived from human parthenogenetic embryonic stem cells

Human parthenogenetic embryonic stem cells (hpESCs) established from artificially activated oocytes have a wider immune-matching ability because of their homozygosity in the major histocompatibility complex alleles. Whether these cells possess the differentiation capacity similar to regular human embryonic stem cells (hESCs) derived from fertilized eggs is unclear. The aims of this study were to determine whether hpESCs could be differentiated into multipotent mesenchymal stem cell (MSC)-like cells in vitro and then compare these cells with those derived from hESCs. MSC-like cells were obtained from both hpESCs and hESCs, which exhibited similar cell surface marker expression profiles. Further analyses revealed that cells derived from hpESCs possessed stronger osteogenic but weaker adipogenic potentials compared with cells derived from hESCs. This is the first work that demonstrates the differentiation of hpESCs into multipotent MSC-like cells. These hpESCs could be a potential source for cell-based therapies.     

表皮干细胞与毛囊干细胞生物学特性的比较

背景：获取更合适的组织工程皮肤种子细胞可使皮肤功能得到更好的修复。 目的：分离、培养表皮干细胞和毛囊干细胞,并比较两种细胞的生物学特性。 方法：体外分离培养2月龄新西兰兔表皮干细胞和毛囊干细胞,取生长良好的第2,3,6代细胞观察其生物学特性。 结果与结论：毛囊干细胞较表皮干细胞贴壁快,具有更高的增殖活性。免疫组化及荧光定量PCR检测显示毛囊干细胞β1整合素、角蛋白19蛋白及mRNA表达均明显高于表皮干细胞。提示作为皮肤组织工程的种子细胞,毛囊干细胞较表皮干细胞更具优势。     

Muscle stem cells

Since its discovery four decades ago, the satellite cell of skeletal muscle has been implicated as the major source of myogenic cells involved in growth and repair of muscle fibres. This review not only looks at the role of the satellite cell in these processes but discusses how cells derived from other sources and tissues have recently been implicated in muscle formation and regeneration. Muscle itself also yields cells that contribute to other cell lineages although it is currently debated as to whether these cells originate within muscle or have migrated there from other tissues. The reality of using cells from muscle or other tissues to repair diseased muscle fibres is also addressed.     

Gastrointestinal stem cells

Turnover of the epithelial cell lineages within the gastrointestinal tract is a constant process, occurring every 2-7 days under normal homeostasis and increasing after damage. This process is regulated by multipotent stem cells, which give rise to all gastrointestinal epithelial cell lineages and can regenerate whole intestinal crypts and gastric glands. The stem cells of the gastrointestinal tract are as yet undefined, although it is generally agreed that they are located within a 'niche' in the intestinal crypts and gastric glands. Studies of allophenic tetraparental chimeric mice and targeted stem cell mutations suggest that a single stem cell undergoes asymmetrical division to produce an identical daughter cell, and thus replicate itself, and a committed progenitor cell which further differentiates into an adult epithelial cell type. The discovery of stem cell plasticity in many tissues, including the ability of transplanted bone marrow to transdifferentiate into intestinal subepithelial myofibroblasts, provides a potential use of bone marrow cells to deliver therapeutic genes to damaged tissues, for example, in treatment of mesenchymal diseases in the gastrointestinal tract, such as fibrosis and Crohn's disease. Studies are beginning to identify the molecular pathways that regulate stem cell proliferation and differentiation into adult gastrointestinal cell lineages, such as the Wnt and Notch/Delta signalling pathways, and the importance of mesenchymal-epithelial interactions in normal gastrointestinal epithelium and in development and disease.     

Hepatic stem cells

The liver in an adult healthy body maintains a balance between cell gain and cell loss. Though normally proliferatively quiescent, hepatocyte loss such as that caused by partial hepatectomy, uncomplicated by virus infection or inflammation, invokes a rapid regenerative response to restore liver mass. This restoration of moderate cell loss and 'wear and tear' renewal is largely achieved by hepatocyte self-replication. Furthermore, hepatocyte transplants in animals have shown that a certain proportion of hepatocytes can undergo significant clonal expansion, suggesting that hepatocytes themselves are the functional stem cells of the liver. More severe liver injury can activate a potential stem cell compartment located within the intrahepatic biliary tree, giving rise to cords of bipotential so-called oval cells within the lobules that can differentiate into hepatocytes and biliary epithelial cells. A third population of stem cells with hepatic potential resides in the bone marrow; these haematopoietic stem cells can contribute to the albeit low renewal rate of hepatocytes, make a more significant contribution to regeneration, and even completely restore normal function in a murine model of hereditary tyrosinaemia. How these three stem cell populations integrate together to achieve a homeostatic balance is not known. This review focuses on two major aspects of liver stem cell biology: firstly, the identity of the liver stem cells, and secondly, their potential value in the treatment of major liver disease.