鼠拟胚体来源细胞向肝细胞及心肌细胞分化的初步观察

目的观察微重力生物反应器内拟胚体（EBs）的形成及其EBs来源细胞的肝细胞与心肌细胞分化。方法将未分化鼠胚胎干细胞（Es细胞）以1×10^6／mL移人微重力反应器内旋转培养，6d后取出反应器内形成的EBs接种于培养板培养，使用含DMSO、地塞米松等IMDM培养液继续培养10d。动态观察EBs形成和EBs来源细胞分化细胞形态特征，采用Western blot、免疫荧光染色方法检测EBs来源细胞肝细胞及心肌细胞标志物的表达。结果生物反应器旋转培养6d形成均一的拟胚体，接种后移行细胞中出现肝细胞特征样细胞和自发性搏动细胞，Western blot检测到EBs来源细胞肝细胞标志物Alb表达，免疫荧光染色分别检测出肝细胞标志物Alb、AFP和心肌细胞标志物GATA4的表达。结论微重力生物反应器可加快EBs的形成。EBs来源细胞可有效地向肝细胞及心肌细胞分化，两种细胞之间可能存在相互作用。     

ES细胞的三维培养与肝细胞分化的初步研究

目的 探索用生物材料三维培养胚胎干细胞(embryonic stem cell,ES细胞)并向肝细胞分化的可行性.方法 胰酶消化悬滴法形成5 d的鼠拟胚胎,将1×106/mL鼠ES细胞与细胞外基质MatrigelTM1:1混合接种于聚乳酸(poly-L-lactic acid,PLLA)和聚乙醇酸(polyglycolic acid,PGA)共聚合三维支架内,用DMSO、地塞米松、HGF、FGF4、胰岛素等诱导ES细胞向肝细胞分化,动态观察ES细胞的培育和生长情况,并用RT-PCR、免疫荧光染色检测其肝细胞标志物白蛋白(ALB)和甲胎蛋白(AFP)的表达.结果 立体显微镜见ES细胞及分化细胞在聚合支架材料上呈三维立体状态生长,并保持细胞活力,随培养时间延长不断增殖.RT-PCR检出分化细胞表达ALB mRNA和AFP mRNA,同样免疫荧光染色也证实表达ALB和AFP.结论 ES细胞可在生物材料聚合三维可降解支架及MatrigelTM上生长,并在诱导剂的作用下向肝细胞分化.     

原代骨髓基质细胞联合细胞因子体外诱导ES-D3细胞造血分化的研究

目的：研究原代骨髓基质细胞联合细胞因子（VEGF，SCF和TPO）体外诱导ES-D3细胞造血分化的效率，探讨体外高效诱导胚胎干细胞生成造血干／祖细胞的方法。方法：取6～8周昆明鼠骨髓制备小鼠骨髓基质细胞（BMSC）饲养层。采用二步诱导法，先将ES-D3细胞诱导分化为拟胚体（EB），再将EB置于4种体系下诱导分化造血干／祖细胞；第1组：自发分化对照组；第2组：细胞因子组（VEGF加SCF加TPO）；第3组：BMSC饲养层组；第4组：BMSC饲养层加细胞因子组（BMSC加VEGF加SCF加TPO）。诱导分化1周的部分细胞行造血祖细胞集落培养。流式细胞仪检测诱导培养7d和14d的各组细胞中干细胞特异抗原（CD34）、祖细胞特异抗原（c-kit）、粒细胞表面抗原（CD11b）、红系细胞特异抗原（Ter119）阳性表达率。间接免疫荧光染色法显示CD34、c-kit、CD11b、Te〉119阳性细胞。RT-PCR检测造血转录因子GATA-2、FIk-1、SCL、p-H1和p-major珠蛋白的表达。结果：诱导7d生成的细胞均表达造血CD34和Pkit，诱导14d生成的细胞表达单核巨噬细胞、CD11b和Te〉119，且诱导细胞表达造血转录因子（GATA-2、SCL、β-H1、β-major）基因mRNA，培养在特定条件下可形成造血祖细胞集落。从生成造血细胞和造血集落的数量分析，骨髓基质细胞饲养层与细胞因子合用时诱导效率明显高于单用组和对照组（P〈0．05或0．01）。结论：骨髓基质细胞饲养层与细胞因子合用，体外可以促进ES-D3细胞的早期造血分化，产生的造血前体细胞可进一步形成造血集落并分化成熟，表达与造血转录和早期造血分化相关的基因。     

肝脏功能重建的细胞来源

生物人工肝、肝细胞移植、组织工程等技术的开展,为肝病的治疗开辟了新的途径.然而,肝细胞来源短缺已经逐渐成为一个突出的问题.本文着重论述了目前肝脏细胞的分化来源研究进展情况,并对各种肝源性和非肝源性干细胞的优缺点进行了讨论,以期为肝组织工程选择细胞来源提供参考,为生物人工肝、肝细胞移植提供充足、合适的细胞来源,协助治疗肝脏疾病.     

人骨髓间充质干细胞体外分化为肝细胞样细胞

目的 探讨人骨髓间充质干细胞(MSCs)的体外培养及特异性诱导为肝细胞样细胞的能力。方法 骨髓标本来源于健康志愿者的胸骨,年龄2～35岁,采用淋巴细胞分离液(密度1.077)分离人MSCs,并分别采用HGF、FGF4、HGF FGF4以及无生长因子四种处理因素体外诱导第三代人MSC向肝细胞样细胞分化。通过流式细胞术分析鉴定.MSCs的纯度,于诱导培养的0、7、14、21、28天时留取细胞检测CK18、AFP和白蛋白的表达情况,同时进行糖原染色验证细胞功能。结果 用淋巴细胞分离液分离出的人MSCs纯度可达90％,采用HGF、FGF4及HGF FGF4三种处理因素均可在体外诱导人MSCs特异分化为具有肝细胞样细胞表型和功能的细胞。结论 人MSCs能在体外扩增并定向诱导为肝细胞样细胞。     

旋转生物反应器内微载体大规模扩增肝细胞

目的 评估旋转生物反应器(RCCS)内肝细胞微载体大规模培养的可行性.方法 为获取足够数量活性良好的肝细胞种子细胞.本实验探索在RCCS内应用微载体技术快速扩增肝细胞的方法 .将cL-1细胞和HepFMMU应用Cytodex-3微载体在RCCS内进行动态培养,观测肝细胞的生长情况和细胞代谢率.结果肝细胞在Cytodex-3微载体上生长迅速、生长倍增时间缩短,并保持很高的生物活性.培养至第5天,细胞数量可达最初接种的23倍.细胞的数量在第5天左右达到最高,然后开始下降.功能学检查、倒置显微镜、扫描电镜及MTT均提示细胞功能良好.结论 RCCS微载体肝细胞大规模培养是一种可行的细胞快速扩增方法 ,但对于人工肝庞大的细胞数量和功能需求,应进一步研究,通过优化营养和废物排除,模拟肝脏生理结构,提高细胞培养规模和功能.     

人肝细胞L02诱导MSCs分化为肝样细胞的观察

目的 探讨骨髓间充质干细胞(MSCs)在与肝细胞L02在体外共培养条件下诱导分化为肝细胞的可行性.方法 密度梯度离心联合贴壁筛选法获取MSCs.将接种于盖玻片上的MSCs和人肝细胞L02共置于培养皿中.在2、4、6、8 d时分别用免疫细胞化学检测AFP、细胞角蛋白(CK18),同时检测染色体核型.结果 成功分离培养出MSCs,其表型为CD29阳性,CD34阴性.共培养的MSCs可在2～8 d时,形态变为三角形、多角型或类圆形.第2天时,共培养细胞AFP表现为强阳性表达,以后减弱,第8天AFP的阳性表达很少.第2、4天检测出CK18均为阴性表达,第6、8天CK18为阳性表达.阳性对照组细胞CK18有较强的阳性表达,AFP弱阳性表达.阴性对照组均为阴性表达.共培养细胞染色体核型无融合现象.结论 人肝细胞L02能够诱导MSCs分化为肝样细胞.     

肝细胞条件培养液对人脂肪问充质干细胞向肝细胞分化和增殖的作用

目的 探讨人脂肪间充质干细胞在改良的诱导体系下向肝细胞的分化和增殖情况,为肝组织工程提供新的种子细胞来源.方法 从人脂肪组织分离出脂肪间充质干细胞,用含有碱性成纤维细胞生长因子、肝细胞生长因子、成纤维细胞生长因子-4的肝细胞诱导液进行诱导,并于诱导7 d后加入抑瘤素M.用细胞计数试剂盒-8法检测整个诱导过程细胞的增殖情况;通过光学显微镜观察诱导细胞的形态变化;用RT-PCR法和免疫荧光法分别检测肝细胞特异性基因和蛋白的表达;并对多种肝细胞特异性功能进行检测.组间比较采用t-test检验.结果 用改良肝细胞诱导液培养的人脂肪间充质干细胞在培养第5、7、14、21天时,细胞数均明显多于用对照培养液培养的细胞(f值分别为6.59、8.69、15.94和24.64,P值均＜0.05).诱导细胞表现出上皮样肝细胞形态,表达肝细胞特异性基因和蛋白;具有多种肝细胞特异性功能,如靛青绿摄取/排泌、糖原合成以及白蛋白分泌功能.结论 人脂肪间充质干细胞在含碱性成纤维细胞生长因子、肝细胞生长因子、成纤维细胞生长因子-4和抑瘤索M的诱导体系中能够分化为更加成熟的具有多种肝细胞特异性功能的细胞,且此诱导体系同时具有促进细胞增殖的作用.     

不同来源干细胞向肝细胞分化研究进展

干细胞是一类具有自我更新和分化潜能的细胞,包括胚胎干细胞和成体干细胞.干细胞的发育受多种内在机制和微环境因素的影响.干细胞的应用是目前生命科学领域的研究热点.现就不同来源干细胞向肝细胞的分化研究进展情况综述如下.     

脂肪间充质干细胞向肝细胞横向分化的研究

目的探讨脂肪源性间充质干细胞（AMSC）向肝细胞横向分化的可能性。方法胶原酶消化脂肪组织,贴壁培养,体外扩增后以流式细胞仪鉴定其表面标志。取扩增3代的AMSC分为2组,诱导分化组在含有2％FBS的DMEM-F12培养基中加入肝细胞生长因子20 ng/ml和成纤维细胞生长因子4 10 ng/ml、1×ITS和地塞米松0．1μmol/L,培养14 d；空白对照组则不加任何细胞因子。RT-PCR检测诱导分化过程中肝细胞核因子1、GATA4等基因转录水平的变化。2周后,采用流式细胞术检测AFP和Alb阳性细胞在两组细胞中的比例,检测肝细胞特异性细胞角蛋白（CK） 18、CK19的表达。结果分离、培养的AMSC呈成纤维细胞样生长,可以稳定传代。流式细胞术检测结果显示第3代脂肪间充质干细胞高表达表面CD29、CD44；不表达CD34、CD45。RT-PCR检测诱导5、8、11、14 d的细胞,显示有肝细胞特异性转录因子GATA4和肝细胞核因子1A基因的表达,并随时间延长而逐渐增多。流式细胞术检测诱导14 d的细胞,发现30．0％的细胞表达Alb,17．8％细胞表达AFP,双阳性的细胞为6．9％；免疫荧光检测发现诱导细胞表达CK18、CK19。空白对照组脂肪间充质干细胞则未见上述各项变化。结论在低血清培养体系中,采用细胞因子联合诱导,显示脂肪间充质细胞在体外能定向分化为肝细胞样细胞。     

Trophoblast differentiation in embryoid bodies derived from human embryonic stem cells

Trophoblast differentiation and early placental development are essential for the establishment of pregnancy, yet these critical events are not readily investigated in human pregnancy. We used embryoid bodies (EBs) prepared from human embryonic stem (hES) cells as an in vitro model of early human development. The levels of human chorionic gonadotropin (hCG), progesterone, and estradiol-17beta in medium from hES cell-derived EBs grown in suspension culture for 1 wk were higher than unconditioned culture medium or medium from undifferentiated hES cells or spontaneously differentiated hES cell colonies. EBs were explanted into Matrigel (MG) "rafts" and cultured for up to 53 d. During the first 7-10 d of three-dimensional growth in MG, small protrusions appeared on the outer surface of EBs, some of which subsequently extended into multicellular outgrowths. The secretion of hCG, progesterone, and estradiol-17beta began to increase on approximately d 20 of MG culture and remained dramatically elevated over the next 30 d. EBs maintained in suspension culture failed to demonstrate this elevation in hormone secretion. Suspension-cultured and MG-embedded EBs exhibited widespread expression of cytokeratins 7/8, demonstrating extensive epithelial differentiation as well as consistent hCG expression. We propose that hES cell-derived EBs may be a useful model for investigation of human trophoblast differentiation and placental morphogenesis.     

Induction of lymphatic endothelial cell differentiation in embryoid bodies

The molecular mechanisms that regulate the formation of the lymphatic vascular system remain poorly characterized. Whereas studies in embryonic stem (ES) cells have provided major new insights into the mechanisms of blood vessel formation, the development of lymphatic endothelium has not been previously observed. We established embryoid bodies (EBs) from murine ES cells in the presence or absence of lymphangiogenic growth factors. We found that lymphatic endothelial cells develop at day 18 after EB formation. These cells express CD31 and the lymphatic lineage markers Prox-1 and Lyve-1, but not the vascular marker MECA-32, and they frequently sprout from preexisting blood vessels. Lymphatic vessel formation was potently promoted by VEGF-A and VEGF-C but not by bFGF. Our results reveal, for the first time, that ES cells can differentiate into lymphatic endothelial cells, and they identify the EB assay as a powerful new tool to dissect the molecular mechanisms that control lymphatic vessel formation.     

Hydrophobic surfaces for enhanced differentiation of embryonic stem cell-derived embryoid bodies

With their unique ability to differentiate into all cell types, embryonic stem (ES) cells hold great therapeutic promise. To improve the efficiency of embryoid body (EB)-mediated ES cell differentiation, we studied murine EBs on the basis of their size and found that EBs with an intermediate size (diameter 100–300 μm) are the most proliferative, hold the greatest differentiation potential, and have the lowest rate of cell death. In an attempt to promote the formation of this subpopulation, we surveyed several biocompatible substrates with different surface chemical parameters and identified a strong correlation between hydrophobicity and EB development. Using self-assembled monolayers of various lengths of alkanethiolates on gold substrates, we directly tested this correlation and found that surfaces that exhibit increasing hydrophobicity enrich for the intermediate-size EBs. When this approach was applied to the human ES cell system, similar phenomena were observed. Our data demonstrate that hydrophobic surfaces serve as a platform to deliver uniform EB populations and may significantly improve the efficiency of ES cell differentiation.     

Forced aggregation of defined numbers of human embryonic stem cells into embryoid bodies fosters robust, reproducible hematopoietic differentiation

To realize the therapeutic potential of human embryonic stem cells (hESCs), it is necessary to regulate their differentiation in a uniform and reproducible manner. We have developed a method in which known numbers of hESCs in serum-free medium were aggregated by centrifugation to foster the formation of embryoid bodies (EBs) of uniform size (spin EBs). These spin EBs differentiated efficiently and synchronously, as evidenced by the sequential expression of molecular markers representing stem cells, primitive streak, and mesoderm. In the presence of hematopoietic growth factors, reproducible differentiation was achieved with blood cells formed in more than 90% of EBs. Using chimeric EBs generated from mixtures of green fluorescence protein-positive (GFP(+)) and GFP(-) hESCs in a clonogenic assay, hematopoietic precursor frequency was estimated to be approximately 1:500 input cells. This method of EB formation provides a generally applicable means for modulating and objectively monitoring the directed differentiation of hESCs.     

利用小鼠胚胎干细胞贴壁制备拟胚体的新方法研究

目的为改进拟胚体制备过程中分化不同步等问题,探讨建立小鼠胚胎干细胞贴壁制备拟胚体的新方法。方法沈阳军区总医院心内科于2004年10月至2006年1月对小鼠进行研究,当小鼠胚胎干细胞R1生长至70%～80%亚融合时,将其消化成单细胞,以1×106的细胞数接种到直径100mm组织培养皿中,用含低浓度白血病抑制因子(LIF)1μg/L的胚胎干细胞培养液连续贴壁培养3d后,收集贴壁细胞团继续悬浮培养。对悬浮培养的拟胚体及其冰冻切片行形态学观察,对悬浮及贴壁分化的拟胚体行甲胎蛋白(AFP)、血小板内皮细胞粘附分子-1(PECAM-1)及神经丝蛋白68KD(NF-68)免疫荧光染色。结果形态学观察用本法得到的拟胚体大小均一,分化同步,能展示从简单拟胚体到成熟囊性拟胚体的典型发育过程。免疫荧光染色显示,AFP、PECAM-1及NF-68三种标志物表达均为阳性。结论与传统方法相比,该法操作简便、拟胚体形成率高、分化阶段同步,具有分化为3个胚层来源细胞的能力,可作为胚胎早期发育和胚胎干细胞分化等研究的理想工具。     

Differentiation of clonal lines of teratocarcinoma cells: formation of embryoid bodies in vitro.

The differentiation in vitro of clonal pluripotent teratocarcinoma cells is reported. The first stage of this process is the formation of simple embryoid bodies which are identical to those found in animals bearing intraperitoneal teratocarcinomas. They consist of an inner core of embryonal carcinoma cells surrounded by a layer of endodermal cells which produce Reichert's membrane. The endodermal cells become apparent shortly after the embryonal carcinoma cells have formed aggregates which are loosely attached to the substratum. One clonal teratocarcinoma line was found to produce complex cystic embryoid bodies in vitro. Following formation of the endodermal cells, extensive differentiation to a wide variety of cell types occurs. There are similarities between the process of embryoid body formation and the early events of differentiation of the mouse embryo.     

Vascular endothelial growth factor promotes proliferation and function of hepatocyte-like cells in embryoid bodies formed from mouse embryonic stem cells

BACKGROUND/AIMS: Embryoid bodies (EBs) formed from embryonic stem cells (ESCs) differentiate into hepatocyte-like cells (HLCs), and are thus thought to be a useful cell source for drug testing and bioartificial liver. The aim of this study was to induce proliferation and function of ESC-derived HLCs in EBs using HLC-endothelial cell interaction. METHODS: EBs were cultured in the presence of vascular endothelial growth factor (VEGF) and/or VEGF receptor (VEGFR) inhibitors. To reproduce HLC-endothelial cell interaction, we overexpressed VEGF in ESC-derived HLCs under the control of Cyp7a1 gene in EBs. RESULTS: VEGF added to the cultured EBs increased the proliferation of ESC-derived endothelial cells, resulting in the promotion of proliferation and function of ESC-derived HLCs. In EBs, the VEGFR2 inhibitor suppressed expression of albumin and endothelial cell marker genes, whereas the inhibitor for both VEGFR1 and VEGFR2 suppressed expression of Cyp7a1 and hepatocyte growth factor (Hgf) genes. Upon exposure to VEGF, the endothelial cells in EBs increased Hgf mRNA expression. Forced VEGF expression in ESC-derived HLCs in EBs induced angiogenesis around the HLCs and resulted in an increase in the amount of HLCs. CONCLUSIONS: VEGF indirectly induces the proliferation and function of ESC-derived HLCs through VEGFR1 and VEGFR2 signaling in endothelial cells.     

Cryobanking of embryoid bodies to facilitate basic research and cell-based therapies

Pluripotent stem cells offer unique opportunities for curing debilitating diseases. However, further comprehensive research is needed to better understand cell signaling during the differentiation of pluripotent cells into different cell lineages and accordingly to develop clinically applicable protocols. One of the limiting steps for differentiation studies is proper culture and expansion of pluripotent stem cells, which is labor intensive, expensive, and requires a great deal of expertise. This limiting step can be overcome by successful banking and distribution of embryoid bodies (EBs), which are aggregates of pluripotent stem cells and typically the starting point of differentiation protocols. The objective of this study was to investigate the feasibility of EB banking by studying survival and functionality of cryopreserved EBs. To this end, EBs were formed by culturing mouse 129 embryonic stem (ES) cells in the absence of leukemia inhibitory factor (LIF) in hanging drops and then subjected to different cryopreservation protocols. In a series of experiments, we first tested the postthaw survival of EBs as a function of dimethylsulfoxide (DMSO) and extracellular trehalose concentrations and cooling rates. Next, we studied the functionality of cryopreserved EBs by assessing their postthaw attachment, growth, and differentiation into various cell types. Higher (≥5%) DMSO concentrations alone or in combination with trehalose (0.1?M and 0.2?M) yielded good postthaw survival rates of >80%, whereas cooling of EBs at 1°C/min in the presence of 5% DMSO +0.1?M trehalose gave the best attachment and growth rates, with differentiation into cell lineages of three germ layers. Taken together, our results suggest that EBs are tolerant to cryopreservation-associated stresses and retain their differentiation potential after freezing and thawing. Furthermore, our experiments with dissociated EB cells and nondissociated EBs suggest that the extracellular matrix may play a beneficial role in the cryotolerance of EBs. Overall, our data support the feasibility of EB banking, which would facilitate advancement of cell-based therapies.