Isolation of hepatocyte-like cells from mouse embryoid body cells

We previously reported that embryoid body (EB) cells derived from embryonic stem (ES) cells are capable of differentiating into functional hepatocyte-like cells both in vitro and in vivo. Because transplantation of EB-derived cells into the liver via the spleen resulted in a low incidence of teratoma formation, purification of hepatocyte-like cells is required to prevent teratoma formation. The aim of this study was to purify hepatocyte-like cells from cultured EBs. For the isolation of hepatocyte-like cells, EBs cultured for 15 days were treated with trypsin-EDTA. The disaggregated cells were plated on a gelatin-coated dish as a monolayer. These cells were separated by Percoll gradient centrifugation, enriched by magnetic cell sorting, and purified by FACS. The purified hepatocyte-like cells in monolayer cultures were positive for immunostaining for albumin and expressed albumin mRNA, but not Oct3/4 mRNA. Transplantation of the purified hepatocyte-like cells derived from mouse ES cells might be an effective treatment for liver failure.     

Enrichment of hepatocytes differentiated from mouse embryonic stem cells as a transplantable source

BACKGROUND: We previously reported that hepatocytes can be differentiated from embryonic stem (ES) cells by way of embryoid body (EB) formation and are transplantable into the mouse liver. However, the transplantation of EB-derived cells frequently resulted in teratoma formation in the recipient liver. In the present study, we eliminated the tumorigenic cells from EB outgrowths and examined the effects of enriched ES-cell-derived hepatocyte transplantation into an injured liver. METHODS: On day 15 in culture, the EBs were partially disaggregated and subcultured. Hepatocytes in the subcultured cells were examined by the expression of hepatocyte markers. Undifferentiated cells contaminating in the EB-derived cells were eliminated by Percoll discontinuous gradient centrifugation. Furthermore, undifferentiated cells, endothelial cells, and macrophages were eliminated by magnetic cell sorting using platelet/endothelial cell adhesion molecule (PECAM)-1 and Mac-1 antibodies. These enriched ES-cell-derived hepatocytes were then transplanted into the injured mouse liver. RESULTS: Percoll centrifugation and PECAM-1 antibodies eliminated the undifferentiated cells expressing Oct-3/4 from the EB-derived cells. ES-cell-derived hepatocytes showed expression of liver-related genes, synthesis of urea and glycogen, and structural characteristics during subculture. A transplantation study showed that the enriched ES-cell-derived hepatocytes integrated into the injured mouse liver and produced no teratomas. When the ES-cell-derived hepatocytes were transplanted into a CCl4-injured liver, the liver function was subsequently improved. CONCLUSIONS: Functional hepatocytes can be differentiated from mouse ES cells by way of EB formation. The elimination of undifferentiated cells from the EBs provides transplantable cells for liver failure without tumorigenicity.     

共培养诱导小鼠ES细胞向软骨细胞分化的初步研究

目的 探讨软骨共培养体系诱导小鼠ES细胞向软骨细胞分化的可行性.方法 GFP标记的小鼠ES细胞初步分化为EB后,将EB消化为单个细胞,同猪关节软骨细胞按一定比例(1∶3)昆合后接种于PGA材料,体外培养1周后植入裸鼠皮下3周取材.对照组为EB细胞接种组及软骨细胞接种组.取材后行连续冰冻切片,切片分别做荧光拍照,HE染色及甲苯胺蓝染色.结果 组织学结果显示,EB细胞接种组形成畸胎瘤;软骨细胞对照组形成软骨组织;实验组形成软骨组织和畸胎瘤的混合体.甲苯胺蓝染色结果和荧光照片对照结果显示,部分软骨组织GFP阳性,由小鼠ES细胞分化而来.结论 软骨共培养体系可以诱导小鼠ES细胞向软骨细胞分化,但得到的软骨组织不纯,混有畸胎瘤组织.     

胚胎干细胞源性肝细胞的获得及体内移植研究

目的 探讨体外定向诱导小鼠胚胎干细胞(ES细胞)分化为肝细胞的方法及肝损伤模型肝内移植的可行性.方法 常规培养ES细胞后,继续悬浮培养4 d以形成拟胚体(EBs),转移EBs到铺有明胶的6孔板中贴壁培养,并添加3 mmol/L丁酸钠开始诱导分化,7 d后加入淤胆血清筛选、纯化ES源性肝细胞,分化过程中用光学显微镜和电子显微镜观察细胞形态及超微结构的改变;用逆转录-聚合酶链反应(RT-PCR)方法检测肝细胞特异性标志基因:白蛋白(ALB)、甲胎蛋白(AFP)、甲状腺素运载蛋白(TTR)、α1抗胰蛋白酶(AAT)、葡萄糖6磷酸酶(G6P)、酪氨酸转氨酶(TAT)mRNA水平的表达;以荧光示踪剂CFDA-SE标记诱导获得的肝细胞,并移植到肝损伤小鼠肝内,观察移植细胞在肝内的定居、增殖情况.结果 诱导分化过程中,ES细胞形态逐渐出现肝细胞样改变,其超微结构与小鼠肝细胞超微结构十分相似;RT-PCR结果显示,随着诱导时间的推进,标志肝细胞发育过程的ALB、AFP、TTR、AAT、G6P、TAT mRNA顺序表达;肝内移植实验结果显示:ES源性肝细胞可在肝损伤小鼠肝内定居并增殖.结论 丁酸钠联合淤胆血清可以诱导ES细胞分化为肝细胞,ES源性肝细胞肝损伤模型体内移植是可行的,这有可能为细胞移植治疗难治性肝病提供一种新的细胞来源.     

Differentiation of embryonic stem cells after transplantation into peritoneal cavity of irradiated mice and expression of specific germ cell genes in pluripotent cells

Permanent embryonic stem cell lines (ES cells) are considered as one of the most promising cellular sources for regenerative medicine. ES cells have a high proliferative potency and ability to differentiate into all kinds of somatic and germ cells. However, transplantation of undifferentiated ES cells into adult recipient tissue results in the formation of teratomas. To understand the mechanisms underlying self-renewal and determination of pluripotent cells, we investigated differentiation potencies of undifferentiated ES cells and differentiating embryoid bodies (EB). ES cells and EBs growing on acetate-cellulose membranes were transplanted into the peritoneal cavity of irradiated mice. Behavior and differentiation of transplanted cells were studied within 1, 2, 3, and 6 weeks after transplantation. No differences in the cell composition were found in the teratomas formed by ES cells and differentiating EBs. The pattern of expression of the genes specific for pluripotent and germ cells was studied in all types of experimental teratomas. The expression of oct4, stella, fragilis was detected in the teratomas, but nanog was not expressed. We conclude that pluripotent cells are retained in the experimental teratomas formed after transplantation of ES cells and EBs but the pattern of expression of the studied genes underwent changes.     

Murine embryonic stem cell-derived hepatic progenitor cells engraft in recipient livers with limited capacity of liver tissue formation

Directed endodermal differentiation of murine embryonic stem (ES) cells gives rise to a subset of cells with a hepatic phenotype. Such ES cell-derived hepatic progenitor cells (ES-HPC) can acquire features of hepatocytes in vitro, but fail to form substantial hepatocyte clusters in vivo. In this study, we investigated whether this is due to inefficient engraftment or an immature phenotype of ES-HPC. ES cells engrafted into recipient livers of NOD/SCID mice with a similar efficacy as adult hepatocytes after 28 days. Because transplanted unpurified ES-HPC formed teratomas in the spleen and liver, we applied an albumin promoter/enhancer-driven reporter system to purify ES-HPC by cell sorting. RT-PCR analyses for hepatocyte-specific genes showed that the cells exhibited a hepatic phenotype, lacking the expression of the pluripotency marker Oct4, comparable to cells of day 11.5 embryos. Sorted ES-HPC derived from beta-galactosidase transgenic ES cells were injected into fumaryl-acetoacetate-deficient (FAH(-/-)) SCID mice and analyzed after 8 to 12 weeks. Staining with X-gal solution revealed the presence of engrafted cells throughout the liver. However, immunostaining for the FAH protein indicated hepatocyte formation at a very low frequency, without evidence for large hepatocyte cluster formation. In conclusion, the limited repopulation capacity of ES-HPC is not caused by a failure of primary engraftment, but may be due to an immature hepatic phenotype of the transplanted ES-HPC.     

Comparative analysis of endoderm formation efficiency between mouse ES cells and iPS cells

Definitive endoderm (DE) derived from stem cells holds potential to differentiate into hepatocytes. Stem cell therapy using those cells has potential for a treatment of liver disease. To date, various ways of inducing hepatocytes from embryonic stem (ES) cells have been reported by researchers. However, it has not been proved enough that induced pluripotent stem (iPS) cells behave in the same manner as ES cells in endoderm differentiation. The purpose of this study was to establish an efficient method to induce DE from iPS cells, through comparatively analyzing the efficacy of endoderm formation from mouse ES cells. Furthermore, the efficiency of a serum-free medium in the differentiation into DE was investigated. Mouse ES cells and iPS cells were floated in culture medium for 2 or 5 days and embryoid bodies (EB) were formed. Subsequently, DE was induced with 100 ng/ml activin A and 100 ng/ml basic fibroblast growth factor (bFGF). RT-PCR and real-time PCR analyses were carried out at each step to determine the gene expression of EB markers. The difference in cellular proliferation between serum-containing and serum-free media was examined by an MTS assay in EB and DE induction. iPS cells showed the paralleled mRNA expression to ES cells in each step of differentiation into EB, but the levels of expression of Sox17 and Foxa2 were relatively higher in ES cell-derived DE, whereas Cxcr4 expression was higher in iPS cell-derived DE. The utilization of serum-free medium for iPS cells showed significantly favorable cellular proliferation during EB formation and subsequent DE induction. Forming EB for 5 days and subsequently DE induction with activin A and bFGF with serum-free medium was an appropriate protocol in iPS cells. This may represent an important step for generating hepatocytes from iPS cells for the development of cell therapy.     

Hepatocyte differentiation from embryonic stem cells and umbilical cord blood cells

With the development of regeneration medicine, many researchers have attempted hepatic differentiation from nonhepatic-origin cell sources. The differentiation of embryonic stem (ES) cells into hepatocyte-like cells has been reported in several papers. Mouse ES cells have shown a potential to develop into hepatocyte-like cells in vitro on the basis of hepatic gene expression after adding several growth factors. We transplanted cultured embryoid body (EB) cells (male) into female mice. A liver specimen of the recipient was examined by immunohistochemical staining for albumin and fluorescence in situ hybridization for the Y chromosome after transplantation. Both Y chromosome- and albumin-positive cells were recognized in the recipient female liver, and were considered to be hepatocyte-like cells derived from ES cells containing the Y chromosome. Many groups, including ourselves, have studied hepatocyte-like cell differentiation from umbilical cord blood cells (UBCs). We cultured nucleated cells isolated from UBCs. Using immunostaining, ALB-positive and CK-19-positive cells were recognized in the culture. Dual staining of ALB and CK-19 demonstrated that ALB was coexpresed with CK-19, suggesting the existence of hepatic progenitors. In this review, we consider recent studies of the differentiation of hepatocytes from nonhepatic origins, especially ES cells and umbilical cord blood.     

Isolation of mouse hepatocytes for transplantation: a comparison between antegrade and retrograde liver perfusion

We compared antegrade with retrograde liver perfusion when isolating mouse hepatocytes for hepatocyte transplantation. Male mouse hepatocytes were isolated by different perfusion methods and transplanted into the spleen of congeneic female mice. Retrograde perfusion yielded a larger number of cells (4.90 x 10(7)) than antegrade (4.09 x 10(7), p < 0.05), but hepatocytes obtained by antegrade perfusion gave higher engraftment efficiency (p < 0.05). More of the transplanted hepatocytes could be recovered from recipient liver with antegrade perfusion than with retrograde perfusion (p < 0.05). Our results indicate that hepatocytes isolated by antegrade perfusion gave a higher engraftment efficiency.     

Partial hepatectomy and subsequent radiation facilitates engraftment of mouse embryonic stem cells in the liver

For liver-targeted regenerative medicine, embryonic stem (ES) cell-derived hepatocyte-like cells proffer great expectation. In vitro exposure to a combination of various growth factors, such as hepatocyte growth factor and fibroblast growth factor-4, as well as cytokines, leads to differentiation of ES cells into hepatocyte-like cells. We sought to determine the in vivo environment that allowed engraftment of ES cells transplanted to the liver. Thus, we examined the effect of partial hepatectomy (50%) (PHT) and subsequent radiation (RT) of the male Balb/c mouse host liver on ES cell engraftment. ES cells (5 x 10(6)) derived from 129Sv mice were transplanted into the residual liver. The controls were ES cells transplanted into a normal liver. Bromo-deoxy-residine (BrdU)-uptake was performed to evaluate the effect of hepatectomy and RT on hepatocyte regeneration. Mouse ES cells engrafted, forming teratomas in the normal liver without showing any mononuclear infiltration. A liver modified by PHT and RT facilitated engraftment of mouse ES cells compared with a normal liver. Hepatic RT significantly suppressed hepatocytic uptake of BrdU.     

以PECAM-1为标志去除残留未分化胚胎干细胞的研究

目的以血小板内皮细胞黏附分子-1(Platelet endothelial cell adhesion molecule-1,PECAM-1)为标志,去除小鼠胚胎干细胞(Embryonic stem cells,ESCs)中残留未分化的细胞,以去除其致瘤性,为ESCs在研究中的安全应用提供思路。方法将小鼠R1胚胎干细胞株在撤去白血病抑制因子的培养基中悬浮培养6 d,体外自发分化形成类胚体,消化打散后,以PECAM-1为标志进行磁珠分选,得到阳性与阴性细胞群体,分别以2×106个/点注射入裸鼠背部皮下,6~8周后观察畸胎瘤形成情况,组织学分析瘤体构成。结果裸鼠背部成瘤结果显示,PECAM-1+细胞群注射8个点中7个成瘤,成瘤率87.5%;而PECAM-1-细胞群注射8个点中1个成瘤,成瘤率12.5%。PECAM-1+细胞群与PECAM-1-细胞群成瘤率具有统计学差异(P=0.01)。结论应用PECAM-1可去除体外分化过程中的残留未分化ESCs,并去除其致瘤性。     

A simple and effective method to improve intrasplenic rat hepatocyte transplantation

Transplanted hepatocytes integrate, survive, and express their specific functions in the liver parenchyma. The aim of this study was to determine whether a large number of hepatocytes could move from the spleen to the liver when the cells are injected together with sodium nitroprusside, and if the improved hepatocyte migration may be related with portal vein dilatation. Wistar rats were transplanted in the spleen with fluorescent-labeled hepatocytes alone or together with sodium nitroprusside. At 1, 3, 6, and 24 h after the transplant, the liver from recipient animals was removed and morphometric analyses were performed. Portal and arterial pressures were also measured immediately after intrasplenic injection of a solution of sodium nitroprusside, hepatocytes alone, or hepatocytes plus sodium nitroprusside. Intrasplenically injected sodium nitroprusside produced a transient drop in arterial pressure and a sustained reduction in portal pressure. During hepatocyte transplantation it increased the number of transplanted cells migrating to the liver after 3 h. Sodium nitroprusside simultaneously injected with hepatocytes in the spleen allowed more cells to migrate into the liver of the host animal without risk in animal survival.     

Transplantation of osteogenically differentiated mouse iPS cells for bone repair

Induced pluripotent stem (iPS) cells are a type of undifferentiated cell that can be obtained from differentiated cells and have the pluripotent potential to differentiate into the musculoskeletal system, the myocardium, vascular endothelial cells, neurons, and hepatocytes. We therefore cultured mouse iPS cells in a DMEM containing 15% FBS, 10(-7) M dexamethasone, 10 mM β-glycerophosphate, and 50 μg/ml ascorbic acid for 3 weeks, in order to induce bone differentiation, and studied the expression of the bone differentiation markers Runx2 and osteocalcin using RT-PCR in a time-dependent manner. Osteocalcin, a bone differentiation marker in bone formation, exhibited the highest expression in the third week. In addition, the deposition of calcium nodules was observed using Alizarin red S staining. iPS cells cultured for bone differentiation were transplanted into severe combined immunodeficiency (SCID) mice, and the osteogenic potential exhibited after 4 weeks was studied. When bone differentiation-induced iPS cells were transplanted into SCID mice, bone formation was confirmed in soft X-ray images and tissue specimens. However, teratoma formation was confirmed in 20% of the transplanted models. When mouse iPS cells were treated with irradiation of 2 Gray (Gy) prior to transplantation, teratoma formation was inhibited. When mouse iPS cells treated in a likewise manner were xenotransplanted into rats, bone formation was confirmed but teratoma formation was not observed. It is believed that irradiation before transplantation is an effective way to inhibit teratoma formation.     

非接触状态下小鼠胚胎干细胞在小鼠肝癌细胞H22诱导下分化的动态观察

目的 观察小鼠源性肿瘤细胞分泌的细胞因子对小鼠胚胎干细胞(ES cells)的诱导分化.方法 将 ES细胞形成的拟胚体分为诱导组和对照组.诱导组在加入小鼠肝癌细胞H22上清液制成的条件培养基中生长,对照组在去除白血病抑制因子(LIF)的ES细胞培养液中生长.于诱导分化的第7、9、12、15天在倒置显微镜下动态观察两组分化情况,并分别测量上清液中AFP的含量.结果 诱导分化的第7天观察到诱导组拟胚体细胞群落的中心和周边有较为典型的小鼠肝癌样细胞形成,第9、12、15天肝癌样细胞数量逐渐增加.对照组拟胚体向三胚层细胞分化,未见肝癌细胞形成.第9,12,15天诱导组和对照组AFP含量经方差分析,差异有统计学意义(P<0.05).结论 小鼠胚胎干细胞在小鼠肝癌细胞H22分泌的细胞因子的诱导下可以分化为肝癌细胞.     

肝特异性非病毒基因治疗载体介导增强型绿色荧光蛋白基因在小鼠肝细胞及肝脏中的表达

目的观察肝细胞特异性基因治疗载体蛋白介导增强型绿色荧光蛋白(EGFP)在体外培养小鼠肝细胞和小鼠肝脏中表达。方法将基因工程制备的肝细胞特异载体蛋白与真核表达质粒以所带电荷比为1：1的比例混合，两者结合形成蛋白-DNA复合物，将该复合物加入体外培养的小鼠肝细胞培养基中或经门静脉注射小鼠体内，用激光共聚焦显微镜观察EGFP在体外培养小鼠肝细胞及活体小鼠肝脏组织中的表达。结果在体外培养的小鼠肝细胞和小鼠肝脏切片中均可以观察到明显的绿色荧光，而对照组未能观察到绿色荧光蛋白。结论构建的肝细胞特异性载体蛋白可以有效的将真核表达质粒载体pcDNA3-EGFP带入肝细胞和活体肝脏组织。可能为肝细胞基因治疗提供有效载体。     

Hepatic differentiation of embryonic stem cells in HF/organoid culture

OBJECTIVE: The use of embryonic stem cells (ES cells) has recently received much attention as a novel cell source for various hybrid artificial organs. To use ES cells, it is necessary to be able to produce functional mature cells from ES cells in large quantities. We applied HF/organoid culture, where cultured cells formed cylindrical multicellular aggregates (organoids) in the lumen of hollow fibers, to mouse and cynomolgus monkey ES cells for hepatic differentiation. MATERIALS AND METHODS: ES cells were injected into hollow fibers. The hollow fibers were centrifuged to induce organoid formation and cultured in medium including factors for hepatic differentiation. To determine the characteristics of cells in the bundle, we evaluated gene expression and liver-specific functions. RESULTS: ES cells immobilized inside hollow fibers proliferated and formed cylindrical organoids. In mouse ES cell cultures, the expression of mRNAs of hepatocyte-specific genes increased with culture time. Ammonia removal activity detected at 15 days increased with culture time. Albumin secretion activity detected at 12 days increased by 21 days. In cynomolgus monkey ES cell cultures, ES cells showed spontaneous ammonia removal functions. The maximum levels of these functions per unit volume of the hollow fibers were roughly comparable to those of primary hepatocyte-organoids. CONCLUSIONS: ES cells differentiated into hepatocyte-like cells using the organoid culture technique. The results indicated that the combination of ES cells and an organoid culture technique was useful to obtain mature hepatocytes.     

Lentivirus-based gene delivery in mouse embryonic stem cells

BACKGROUND: Embryonic stem (ES) cells are widely used in therapeutic research as an unlimited source of cell therapy. Therefore, it is of great value to find a way to efficiently manipulate ES cells. HIV-1-derived lentiviral vectors are now considered to be an efficient vehicle for delivering genes into a variety of cells. In this study, we examined the efficacy of lentivirus-based gene delivery into mouse ES (mES) cells. MATERIALS AND METHODS: Recombinant HIV-I-based lentiviral vectors Lt-GFP, expressing green fluorescent protein (GFP), and Lt-LacZ, expressing E. coli LacZ gene in conjunction with neomycin resistance gene, were generated using a FuGENE 6 transduction method and used for transducing ES cells derived from 129Sv mice. Lentiviral transduction efficacy was evaluated by GFP expression assay using flow cytometry and by X-gal staining. The in vivo potential of developing teratoma of such transduced mES cells was examined in severe combined immunodeficiency (SCID) mice. RESULTS: FuGENE 6 showed no considerable transduction-associated cytotoxicity. The expression rate of GFP and LacZ of mES cells increased on a multiplicity of infection (MOI)-dependent manner with the amount of Lt-GFP and Lt-LacZ used. Approximately 42% of mES cells were positive for GFP after infection of Lt-GFP at an MOI of 30. Notably, after G418 selection, nearly 100% of Lt-LacZ-transduced mES cells were positive for LacZ and formed teratomas in SCID mice. CONCLUSIONS: This work demonstrates that HIV-I-based lentiviral vectors are capable of transducing mES cells. Lentiviral vectors may facilitate an advance in the field of gene transfer and expression in various types of ES cells, including human ES cells.     

Hepatic differentiation of mouse iPS cells in vitro

Induced pluripotent stem (iPS) cells are pluripotent and are able to unlimitedly proliferate in vitro. This technical breakthrough in creating iPS cells from somatic cells has noteworthy implications for overcoming the immunological rejection and the ethical issues associated with the derivation of embryonic stem cells from embryos. In the current work, we present an efficient hepatic differentiation of mouse iPS cells in vitro. iPS cells were cultured free floating to induce the formation of embryoid bodies (EB) for 5 days. EB were transferred to a gelatin-coated plate and treated with 100 ng/ml activin A and 100 ng/ml basic fibroblast growth factor (bFGF) for 3 days to induce definitive endoderm. Cells were further cultured for 8 days with 100 ng/ml hepatocyte growth factor (HGF) to generate hepatocytes. Characterization was performed by RT-PCR assay. Functional analysis for albumin secretion and ammonia removal was also carried out. iPS cell-derived hepatocyte-like cells (iPS-Heps) were obtained at the end of the differentiation program. Expression levels of a gestational hepatocyte gene and lineage-specific hepatic genes intensified in iPS-Heps. The production of albumin increased in a time-dependent manner. iPS-Heps were capable of metabolizing ammonia. We present here instant hepatic differentiation of mouse iPS cells using combined 3-day treatments of activin A and bFGF with subsequent 8-day HGF. Our study will be an important step to generate hepatocytes from human iPS cells as a new source for liver-targeted cell therapies.     

Differentiation of human and mouse embryonic stem cells along a hepatocyte lineage

Embryonic stem (ES) cells may differentiate along a hepatocyte lineage; however, currently there are no reports of culture conditions yielding high levels of hepatocyte-specific gene expression in these cells. We investigated culture conditions for differentiating ES cells into hepatocyte-like cells in vitro. Various combinations of culture media, growth and differentiation factors, and substratum precoatings were evaluated, and it was determined that a combination of Iscove's modified Dulbecco's medium with 20% fetal bovine serum, human insulin, dexamethasone. and collagen type I precoating was optimal for directing mouse ES cells along a hepatocyte lineage. Treatment of mouse ES cell with the optimal condition led to prealbumin gene expression 20% as high, and albumin synthesis 7% as high, as in mouse liver. The optimal culture condition also induced albumin gene expression in differentiated human ES cells 1% as high as in normal human hepatocytes as shown by Western blot analysis, and cells were positive for human albumin by immunocytochemistry. In addition, our optimal condition led to high levels of albumin gene expression in primary mouse hepatocytes after 35 days of culture, levels 10-fold higher than with other hepatocyte differentiation media. In conclusion, our optimal condition directed both mouse and human ES cells along a hepatocyte lineage. This represents the initial step in establishing cell lines that can be employed in cell-based therapeutics in humans and for toxicology and pharmacology studies.