大鼠骨髓基质细胞向Schwann细胞分化后蛋白表达变化的研究

近年来很多研究报道大鼠骨髓基质细胞（bone marrow stromal cells,MSCs）可以向神经细胞或神经胶质细胞分化,其中多数研究观察了细胞形态以及几种神经相关蛋白的免疫反应,也有报道用基因组学方法分析MSCs诱导过程中基因谱的表达变化.尚未见报道用蛋白质组学方法分析MSCs在诱导过程中蛋白谱的表达变化.本研究利用蛋白质组学技术分析MSCs向Schwann细胞样细胞诱导分化过程中蛋白谱的表达变化.从成年SD大鼠的股骨和胫骨中分离培养MSCs,应用复合诱导因子体外连续诱导MSCs向Schwann细胞样细胞分化.采用2-DE技术分离未诱导和诱导分化后MSCs总蛋白,应用基质辅助激光解吸电离飞行时间质谱得到相应的肽质量指纹图谱,搜索数据库分析差异蛋白质点.所得到的MSCs蛋白谱有792个蛋白点,通过PDQuest软件分析诱导前后MSCs的蛋白谱,初步分析发现有74个蛋白质的表达发生了明显的变化,其中43个蛋白表达上调,31个蛋白表达下调.本研究通过质谱分析并进行网上数据库搜索匹配,初步分析发现这些蛋白主要包括骨架和结构蛋白、生长因子类的蛋白、代谢相关蛋白及酶类、伴侣蛋白、受体类蛋白、细胞周期蛋白、钙结合蛋白以及其他蛋白等.研究表明,MSCs体外条件诱导分化过程中有较多蛋白表达发生变化;其中与神经细胞和神经胶质细胞相关蛋白：BDNF,CNTF,GFAP等在MSCs体外条件诱导分化后中表达明显上调;本研究从蛋白质水平为MSCs体外向Schwann细胞样细胞条件诱导提供了新的研究资料。     

p38对骨髓间充质干细胞成肌分化作用的研究

目的:以5-氮杂胞苷(5-Aza-CR)诱导骨髓间充质干细胞(MSCs)成肌分化,探讨生肌调控因子中Myf5的表达及信号转导通路p38在此分化过程中的作用.方法:分离、纯化MSCs,以10 μmol/L 5-Aza-CR诱导其向成肌细胞分化,RT-PCR测定Myf5的表达,免疫组化检测肌球蛋白(myosin)的表达,Western-blot检测p38信号通路特异抑制剂SB203580作用前后磷酸化p38的变化.结果:SB203580作用后,Myf5表达由6 h延迟至9 h,诱导12 d部分MSCs表达myosin,18 d表达的数量及程度明显增加;5-Aza-CR诱导后,磷酸化p38蛋白水平较作用前增强,但在SB203580抑制后明显受抑.结论:5-Aza-CR诱导后,MSCs表达生肌调控因子并向成肌细胞分化,p38在此分化过程中起着正向信号转导作用.     

人参皂甙Rb1减轻冈田酸诱导的大鼠海马神经元Tau蛋白过度磷酸化

为研究人参皂甙Rb1(ginsenoside Rb1)对冈田酸(okadaic acid,OA)诱导的大鼠海马神经元Tau蛋白过度磷酸化的影响及其可能机制,实验随机分为正常组、溶媒对照组、OA模型组和Rb1预处理组。正常组不作任何处理;Rb1预处理组大鼠分别用5、10、20 mg/kg的Rb1预处理,每天一次,共14 d,于第13天向海马背侧注射1.5μl OA[0.483 μl,溶于10% 二甲基亚砜(dimethysulphoxide,DMSO)];OA模型组大鼠于第13天时海马背侧注射OA,溶媒对照组则注射等体积的生理盐水。各组均于第15天收取标本。通过Biescbowski’s染色、免疫组化和Western blot,分别观察大鼠海马神经元胞体和突起内神经原纤维的改变和磷酸化Tau蛋白的表达水平,同时检测蛋白磷酸酯酶2A(protein phosphatase-2A,PP2A)活性以探讨其作用机制。结果显示:(1)OA模型组与溶媒对照组及正常组比较,海马神经元胞体和突起着色较深,染色不均匀;神经元中Thr231和Sei396位点磷酸化的Tau蛋白和总Tau含量增多;PP2A活性则明显下降(P<0.01):(2)Rb1预处理组大鼠海马神经元胞体和突起染色均匀,神经原纤维走行规则;海马神经元中Thr231和Ser396位点磷酸化的Tau蛋白和总Tau 含量较OA模型组减少,而PP2A活性明显增高(P<0.01)。以上观察结果表明,人参皂甙Rb1可以减轻OA诱导的大鼠海马神经元Tau蛋白过度磷酸化,其机制可能与提高PP2A活性有关。     

人脐血间充质干细胞诱导分化为神经细胞的研究

目的探讨体外诱导人脐血间充质干细胞(MSCs)向神经细胞分化的条件,为治疗中枢神经系统损伤提供实用的干细胞来源。方法体外分离、纯化、扩增脐血MSCs,流式细胞仪检测细胞表面标志。采用脑源性神经营养因子BDNF 10ng/ml 维甲酸RA0.5μM 碱性成纤维生长因子bFGF 20ng/ml协同诱导脐血MSCs定向分化。免疫荧光染色检测诱导后细胞的星形胶质细胞特异标志GFAP及神经元特异标志MAP2的表达情况。建立大鼠脊髓横断损伤模型,将BrdU标记的诱导后的细胞移植入损伤的脊髓中,采用BBB运动功能评分标准在术后24h及1、2、3、4、5周各时间点对大鼠进行运动功能评分。用组织学和免疫组化方法检测移植到大鼠脊髓中的BrdU阳性细胞的存活、迁移、分化情况。结果脐血MSCs体外培养三代后,细胞表面CD11b、CD34、CD45和CD44表达阴性。诱导分化7d后,大部分细胞的形态类似神经元,免疫荧光染色检测MAP2阳性细胞占大多数,明显多于GFAP阳性细胞。5周后,细胞移植组大鼠的后肢运动功能恢复情况较对照组好。免疫组织化学结果显示植入的细胞可长时间在宿主脊髓中存活,并向损伤处两端迁移。结论人脐血MSCs于体外在特定的条件下可以诱导分化为神经元样细胞。移植脐血MSCs诱导后的神经细胞可在损伤的脊髓中存活、迁移,并能促进脊髓损伤后行为和功能恢复。     

骨髓间充质干细胞源神经细胞移植治疗帕金森病大鼠模型

目的探讨骨髓间充质干细胞（mesenchymal stemcells,MSCs）源神经细胞脑内移植对帕金森病（Parkinson s disease,PD）大鼠的治疗作用。方法贴壁培养法分离、培养大鼠骨髓MSCs,脑匀浆上清诱导第3代MSCs向神经细胞分化,采用免疫细胞化学法鉴定诱导分化后细胞的性质,激光共聚焦显微镜检测诱导前后细胞Ca2＋浓度变化,6只PD大鼠行纹状体内MSCs源神经细胞移植作为细胞移植组,6只PD大鼠作为对照组。细胞移植术后4周检测PD大鼠的行为变化,观察移植细胞在脑内的分布情况。结果倒置显微镜下可见MSCs呈纺锤形和多角形,有1～2个核仁,MSCs经脑匀浆上清诱导后其胞体折光性增强,发出数个细长突起,互相交织成网,有的似轴突。诱导后细胞表达神经元特异性标志物神经元特异性烯醇化酶（NSE）和神经丝蛋白（NF）,胞质Ca2＋荧光强度显著增强,可推测诱导后的细胞为MSCs源神经细胞,将BrdU标记的MSCs源神经细胞移植到PD大鼠纹状体治疗4周后,可见细胞散在分布于注射侧脑组织,有少量细胞可迁移到对侧脑组织,PD大鼠的旋转行为得到显著改善。结论MSCs源神经细胞移植治疗帕金森病大鼠可使其旋转行为得到改善。     

雌激素削弱同型半胱氨酸诱导的N2a细胞Tau和NgR共表达

目的探讨雌激素对神经细胞的保护作用。方法实验采用免疫荧光技术检测高同型半胱氨酸(Hcy)诱导N2a细胞后Tau蛋白和NgR蛋白表达的变化。实验分成四组:对照组;Hcy诱导0.5小时组;Hcy诱导5小时组;用外源性17β-雌二醇预处理2小时后再用Hcy诱导5小时组。结果与对照组(15.85±1.56和9.93±0.86)相比,同型半胱氨酸诱导5h组Tau蛋白和NgR蛋白的共表达(39.91±10.05和31.98±5.45)明显增加(P<0.01);雌激素预处理组与对照组相比N2a细胞Tau蛋白和NgR的表达(15.32±2.62和9.76±1.79)无差异(P>0.05)。结论雌激素能够下调NgR和Tau蛋白的表达,对N2a细胞神经元具有保护作用。雌激素可能主要通过抑制糖原合成酶激酶-3并与雌激素受体、-βcatenin作用减少Tau蛋白的过度磷酸化,从而减轻了神经细胞的损伤,引起NgR表达下调。     

综述:Tau蛋白过度磷酸化机制及其在阿尔茨海默病神经元变性中的作用

Tau蛋白是神经元中含量最高的微管相关蛋白,其经典生物学功能是促进微管组装和维持微管的稳定性．在阿尔茨海默病(Alzheimer's disease,AD)患者,异常过度磷酸化的Tau蛋白以配对螺旋丝结构形成神经原纤维缠结并在神经元内聚积．大量研究提示,Tau蛋白异常在AD患者神经变性和学习记忆障碍的发生发展中起重要作用．本课题组对Tau蛋白异常磷酸化的机制及其对细胞的影响进行了系列研究,发现Tau蛋白表达和磷酸化具有调节细胞生存命运的新功能,并由此对AD神经细胞变性的本质提出了新见解．本文主要综述作者实验室有关Tau蛋白的部分研究结果．     

大鼠骨髓间充质干细胞向心肌细胞分化的研究

目的：研究体外不同诱导条件下大鼠骨髓间充质干细胞（MSCs）向心肌细胞分化的潜能。方法：取Wistar大鼠股骨和胫骨骨髓,分离培养MSCs,采用第二代或第三代MSC8,以5-氮杂胞苷（5-aza）、碱性成纤维细胞生长因子（bFGF）及两者联合作用,作为分化诱导剂,连续观察三周,相差显微镜下观察其形态变化。免疫细胞化学方法鉴定心肌特异性蛋白T（Troponin T,cTnT）、连接蛋白43（Connexin43）、α-横纹肌动蛋白（α-Sarcomevic Actin）的表达,应用半定量RT—PCR技术分析Nkx2．5、GATA-4、TGF-？等相关调控基因在分化过程中的表达。结果：免疫细胞化学显示cTnT、Connexin43、α-Sarcomeric Actin诱导前无表达,单纯bFGF诱导组及对照组未发现cTnT、Connexin43、α-Sarcomevic Actin染色阳性细胞,单纯5-aza诱导组诱导后上述三种蛋白阳性细胞表达比例分别为22％、28％、32％,5-aza与bFGF联合诱导组诱导后上述三者阳性细胞表达比例分别为28％、33％、40％,联合诱导组诱导后细胞阳性率明显高于单纯5-aza诱导组,两组相比较差异有显著性意义（P〈0．05）。RT—PCR检测结果显示,GATA-4、Nkx2．5、TGF—β在诱导前的MSCs有低表达,单纯5-aza诱导组及5-aza与bFGF联合诱导组诱导后3周,这三种基因有较强的表达,单纯5-aza诱导组诱导检测结果显示,GATA-4、Nkx2．5、TGF—β在诱导前的MSCs有低表达,单纯5-aza诱导组及5-aza与bFGF联合诱导组诱导后3周,这三种基因有较强的表达,单纯5-aza诱导组诱导前后相比较,差异有显著性意义（P〈0．05）,5-aza与bFGF联合诱导组诱导前后相比较,差异也有显著性意义（P〈0．05）,单纯5-aza诱导组与5-aza和bFGF联合诱导组诱导后两组之间相比较,差异亦有显著性意义（P〈0．05）,表明单纯5-aza诱导及5—aza与bFGF联合诱导均可使MSCs向心肌细胞转化,联合诱导可以使更多的MSCs向心肌细胞方向转化。单纯bFGF诱导组诱导前后无显著性差异。结论：5-aza及bFGF联合诱导,可以作为更好的促进MSCs向心肌细胞分化的条件。     

红花黄色素B对冈田酸致SH-SY5Y神经元损伤的保护作用

本研究目的是考察红花黄色素B(SYB)对冈田酸(OA)致SH-SY5Y神经元损伤的保护作用。采用全反式维甲酸(ATRA)诱导SH-SY5Y细胞分化为成熟神经元,OA诱导神经元损伤,建立Tau蛋白过度磷酸化的神经元突触萎缩模型;Giemsa染色法观察SH-SY5Y细胞形态学变化;Western Blot检测Tau蛋白262位点磷酸化水平;流式细胞术检测细胞总活性氧(ROS)和线粒体源ROS水平,以及线粒体膜电位的变化。结果表明,ATRA可诱导SH-SY5Y细胞分化为成熟神经元;OA可致神经元突触萎缩和Tau蛋白在262位点过度磷酸化;SYB能够改善OA所致成熟神经元损伤,降低Tau蛋白在262位点的磷酸化水平,其保护作用机制可能与减少胞内及线粒体源ROS产生,提高线粒体膜电位有关。     

RNAi靶向抑制p65基因对大鼠骨髓间充质干细胞向神经元分化的影响

目的:探讨RNAi靶向抑制p65基因对骨髓间充质干细胞(MSCs)向神经元分化中的影响。方法:采用RNAi干扰技术,Rn-p65-siRNA转染体外培养的大鼠MSCs,用盐酸法舒地尔诱导MSCs向神经元分化,并以未转染组及Cy3标记的negative control siRNA为对照组。在倒置荧光显微镜下观察经negative control siRNA转染24 h、48h及72 h后MSCs的荧光表达变化;采用MTT比色法检测转染前、转染24 h、48 h及72 h后MSCs的存活率;RTPCR检测p65 mRNA的表达;Western blot法检测3组MSCs中p65蛋白的表达;细胞免疫组化法检测p65蛋白、神经元特异性烯醇化酶(NSE)、神经元微管结合蛋白(MAP-2)和胶质细胞原纤维酸性蛋白(GFAP)的表达。结果:Negative control siRNA转染72 h,MSCs荧光表达最强,转染率可达83.3%±3.8%;Rn-p65-siRNA转染组MSCs的p65 mRNA转录下降,p65蛋白表达减少;Rn-p65-siRNA转染组的MSCs存活率也显著减少,显著高于对照组(P0.05)。转染72 h后,诱导转染组MSCs向神经元分化的诱导效果最佳,可高效表达NSE、MAP-2等,而不表达胶质纤维酸性蛋白(GFAP),与对照组比较有统计学差异(P0.05)。结论:靶向抑制p65基因表达可促进骨髓间充质干细胞(MSCs)向神经元分化。     

Production of hematopoietic cells from ES cells

Murine embryonic stem (ES) cells are cell lines established from blastocyst which can contribute to all adult tissues, including the germ-cell lineage, after reincorporation into the normal embryo. ES cell pluripotentiality is preserved in culture in the presence of LIF. LIF withdrawal induces ES cell differentiation to nervous, myocardial, endothelial and hematopoietic tissues. The model of murine ES cell hematopoietic differentiation is of major interest because ES cells are non transformed cell lines and the consequences of genomic manipulations of these cells are directly measurable on a hierarchy of synchronized in vitro ES cell-derived hematopoietic cell populations. These include the putative hemangioblast (which represents the emergence of both hematopoietic and endothelial tissues during development), myeloid progenitors and mature stages of myeloid lineages. Human ES cell lines have been recently derived from human blastocyst in the USA. Their manipulation in vitro should be authorized in France in a near future with the possibility of developing a model of human hematopoietic differentiation. This allows to envisage in the future the use of ES cells as a source of human hematopoietic cells.     

Homing of annexin-labeled stem cells to apoptotic cells

Ischemic diseases are characterized by the presence of pro-apoptotic stimuli, which initiate a cascade of processes that lead to cell injury and death. Several molecules and events represent detectable indicators of the different stages of apoptosis. Among these indicators is phosphatidylserine (PS) translocation from the inner to the outer leaflet of the plasma membrane, which can be detected by annexinV (ANXA5) conjugation. This is a widely used in vivo and in vitro assay marking the early stages of apoptosis. We report here on an original method that employs PS-ANXA5 conjugation to target stem cells to apoptotic cells. Mesenchymal stem cells (MSCs) from GFP-positive transgenic rats were biotinylated on membrane surfaces with sulfosuccinimidyl-6-(biotinamido) hexanoate (sulfo-NHS-LC-biot) and then bound to avidin. The avidin-biotinylated MSCs were labeled with biotin conjugated ANXA5. Bovine aortic endothelial cells (BAE-1 cells) were exposed to UVC to induce caspasedependent apoptosis. Finally, we tested the ability of ANXA5-labeled MSCs to bind BAE-1 apoptotic cells: suspended ANXA5-labeled MSCs were seeded for 1 hour on a monolayer of UV-treated or control BAE-1 cells. After washing, the number of MSCs bound to BAE-1 cells was evaluated by confocal microscopy. Statistical analysis demonstrated a significant increase in the number of MSCs tagged to apoptotic BAE-1 cells. Therefore, stem cell ANXA5 tagging via biotin-avidin bridges could be a straightforward method of improving homing to apoptotic tissues. A. Gerasimou, R. Ramella and A. Brero contributed equally to this paper.     

Separation of mitogen-induced suppressor cells of human antibody-producing cells

Human antibody-forming cells were demonstrated by a plaque in agar technique following in vitro stimulation with either pokeweed mitogen or Cowan I strain of protein A-positive Staphylococcus aureus bacteria. We evaluated the effects on this antibody formation caused by the addition of cells which had been stimulated with PH A or Con A. Both Con A and PHA cells harvested after 3 days showed strong inhibition of pokeweed-induced plaque formation. The majority of the suppression could be accounted for by a blast fraction separated on 1g sedimentation gradients from the Con A or PHA cultures. Small cells from such cultures showed inhibition of PFC when added at high ratios (1:2), but this suppressive activity diluted out much more rapidly than that of the blast cells. No helper activity was noted with either small cells or blasts. Our studies indicate a T-cell blast as the suppressive fraction in Con A- or PHA-stimulated human lymphoid cells. While this T-cell suppression applies to T-dependent responses such as antibody stimulation with pokeweed mitogen, it does not have a substantial effect on Cowan I-induced plaque-forming responses. The finding that Cowan I-induced plaques could not be inhibited by Con A or PHA blasts indicates the T independence of this response.     

胚胎干细胞向造血细胞分化研究

胚胎干（embryonic stem,ES）细胞是来源于囊胚的内细胞团（inner cell mass,ICM）,具有发育的全能性或多能性,能嵌合到早期胚胎,在体内可以参与各种组织发育甚至包括生殖细胞;在体外分化培养条件下,可以顺序分化出各种组织细胞,与体内完整胚胎发育过程相符合,而且可以通过调节ES细胞某些基因的表达而调节其分化。因此,ES细胞是研究哺乳动物早期胚胎发育、细胞分化及其关键基因鉴定的理想模型。另外,胚胎生殖脊（embryonic germ,EG）细胞系也具有同样的生物学特性,它是由早期胚胎的原始生殖脊（primordial germ,PG）细胞建株而来。最近研究显示：ES细胞在体外不但可以分化为所有造血细胞系,而且还可以分化为具有长期增殖能力的造血干细胞。作者就胚胎干细胞向造血细胞和造血干细胞分化及其诱导因子和调控基因的表达作一综述。     

Transdifferentiation of mouse BM cells into hepatocyte-like cells

BACKGROUND: During the past few years multiple studies have revealed that adult stem cells, including BM origin stem cells, can be transdifferentiated into various cell types, including hepatocyte-like cells, under proper treatments or in a suitable microenvironment. However, little is known about the mechanism of the transdifferentiation, and the treatments employed seem to be very complicated and require simplification. It is important to determine the suitable conditions in which BM cells would be efficiently differentiated into hepatocytes. METHODS: Mouse BM cells were isolated from femurs and tibias and cultured in IMDM supplemented with 10% FBS. Hepatic differentiation was induced in a differentiation medium containing 20 ng/mL HGF, 10 ng/mL FGF-4, 10 ng/mL Oncostatin M (OSM) and different concentrations of liver-injured mouse sera. The differentiated hepatic cells were characterized by the expression of liver-associated mRNA and proteins and morphologic and functional features. RESULTS: BM cell-derived polygonal cell colonies appeared after several days of culture, and these hepatocyte-like cells expressed AFP, HNF-3beta, CK19, CK18, ALB, TAT and G-6-Pase at mRNA and protein levels, and the cells also had some hepatic cellular functions, such as glycogen storage and urea production. Interestingly, suitable concentrations of sera from liver-injured mice added to this system showed strong stimulation on the in vitro transdifferentiation of mouse BM cells into hepatocytes. DISCUSSION: In the present study we have established an effective hepatic differentiation system by a combination of HGF, FGF-4, OSM and liver-injured mouse sera in vitro. Accordingly, it will be a useful resource not only for understanding the mechanisms of transdifferentiation but also for efficient amplification of hepatocyte progenitor cells of BM origin.     

Progenitor cells of the testosterone-producing Leydig cells revealed

The cells responsible for production of the male sex hormone testosterone, the Leydig cells of the testis, are post-mitotic cells with neuroendocrine characteristics. Their origin during ontogeny and regeneration processes is still a matter of debate. Here, we show that cells of testicular blood vessels, namely vascular smooth muscle cells and pericytes, are the progenitors of Leydig cells. Resembling stem cells of the nervous system, the Leydig cell progenitors are characterized by the expression of nestin. Using an in vivo model to induce and monitor the synchronized generation of a completely new Leydig cell population in adult rats, we demonstrate specific proliferation of vascular progenitors and their subsequent transdifferentiation into steroidogenic Leydig cells which, in addition, rapidly acquire neuronal and glial properties. These findings, shown to be representative also for ontogenetic Leydig cell formation and for the human testis, provide further evidence that cellular components of blood vessels can act as progenitor cells for organogenesis and repair.     

Phosphatidylserine-dependent adhesion of T cells to endothelial cells

Phosphatidylserine (PS) was exposed at the surface of human umbilical vein endothelial cells (HUVECs) and cultured cell lines by agonists that increase cytosolic Ca(2+), and factors governing the adhesion of T cells to the treated cells were investigated. Thrombin, ionophore A23187 and the Ca(2+)-ATPase inhibitor 2, 5-di-tert-butyl-1,4-benzohydroquinone each induced a PS-dependent adhesion of Jurkat T cells. A23187, which was the most effective agonist in releasing PS-bearing microvesicles, was the least effective in inducing the PS-dependent adhesion of Jurkat cells. Treatment of ECV304 and EA.hy926 cells with EGTA, followed by a return to normal medium, resulted in an influx of Ca(2+) and an increase in adhering Jurkat cells. Oxidised low-density lipoprotein induced a procoagulant response in cultured ECV304 cells and increased the number of adhering Jurkat cells, but adhesion was not inhibited by pretreating ECV304 cells with annexin V. PS was not significantly exposed on untreated Jurkat cells, as determined by flow cytometry with annexin V-FITC. However, after adhesion to thrombin-treated ECV304 cells for 10 min followed by detachment in 1 mM EDTA, there was a marked exposure of PS on the Jurkat cells. Binding of annexin V-FITC to the detached cells was inhibited by pretreating them with unlabelled annexin V. Contact with thrombin-treated ECV304 cells thus induced the exposure of PS on Jurkat cells and, as Jurkat cells were unable to adhere to thrombin-treated ECV304 cells in the presence of EGTA, the adhesion of the two cell types may involve a Ca(2+) bridge between PS on both cell surfaces. The number of T cells from normal, human peripheral blood that adhered to ECV304 cells was not increased by treating the latter with thrombin. However, findings made with several T cell lines were generally, but not completely, consistent with the possibility that adhesion to surface PS on endothelial cells may be a feature of T cells that express both CD4(+) and CD8(+) antigens. Possible implications for PS-dependent adhesion of T cells to endothelial cells in metastasis, and early in atherogenesis, are discussed.     

Recognition of virus infected cells by NK cells

NK cells show cytotoxicity against virus-infected cells and tumor cells and play an important role in host defense. Although mecheanism of target cell recognition by NK cells have been unclear for a long time, it has recently been elucidated that certain NK cell receptors specifically recognize virus products. Furthermore, expression pattern of NK cell receptors, which consist of activating and inhibitory receptors, determines susceptibility to virus-infection. Here, we review recent progress of mechanism of recognition of virus-infected by NK cells.