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.     

Differentiation of human embryonic stem cells to hepatocytes using deleted variant of HGF and poly-amino-urethane-coated nonwoven polytetrafluoroethylene fabric

Human embryonic stem (hES) cells have recently been studied as an attractive source for the development of a bioartificial liver (BAL). Here we evaluate the differentiation capacity of hES cells into hepatocytes. hES cells were subjected to suspension culture for 5 days, and then cultured onto poly-amino-urethane (PAU)-coated, nonwoven polytetrafluoroethylene (PTFE) fabric in the presence of fibroblast growth factor-2 (bFGF) (100 ng/ml) for 3 days, then with deleted variant of hepatocyte growth factor (dHGF) (100 ng/ml) and 1% dimethyl sulfoxide (DMSO) for 8 days, and finally with dexamethasone (10(-7) M) for 3 days. The hES cells showed gene expression of albumin in a time-dependent manner of the hepatic differentiation process. The resultant hES-derived hepatocytes metabolized the loaded ammonia and lidocaine at 7.8% and 23.6%, respectively. A million of such hepatocytes produced albumin and urea at 351.2 ng and urea at 7.0 microg. Scanning electron microscopy showed good attachment of the cells on the surface of the PTFE fabric and well-developed glycogen rosettes and Gap junction. In the present work we have demonstrated the efficient differentiation of hES cells to functional hepatocytes. The findings are useful to develop a BAL.     

Instant hepatic differentiation of human embryonic stem cells using activin A and a deleted variant of HGF

Human embryonic stem (hES) cells have the ability to differentiate into a variety of different cell lineages and potentially provide a source of differentiated cells for many therapeutic uses. Here we investigated an efficient method of hepatic differentiation from hES cells. A human ES cell line, KhES-1, was used and maintained by a nonfeeder method. KhES-1 cells were cultured for 5 days in the presence of human activin A (50 ng/ml) and then treated with a deleted variant of hepatocyte growth factor (dHGF) at 0, 100, or 500 ng/ml for 7 days. The resultant cells were biologically analyzed. The expression of the endodermal genes SOX17 and FOXA2 increased in KhES-1 cells after activin A treatment. In contrast, Oct4, a self-renewal undifferentiated marker, decreased in a time-dependent manner in KhES-1 cells. Following a 7-day treatment of the resultant cells with dHGF, especially at 500 ng/ml, KhES-1 cells showed an expression of the hepatic makers albumin, AFP, and CK18. Transitional electron microscopy showed well-developed glycogen rosettes and a gap junction in KhES-1 cells treated with 500 ng/ml of dHGF. We developed an efficient method to differentiate KhES-1 cells into hepatocyte-like cells in vitro using 50 ng/ml of activin A and 500 ng/ml of dHGF.     

Transplantation of human hepatocytes cultured with deleted variant of hepatocyte growth factor prolongs the survival of mice with acute liver failure

BACKGROUND: Considering the scarcity of donor livers, it is extremely important to establish a functional culture method for isolated hepatocytes. As a tool for maintaining hepatocyte functions in vitro, dHGF, a variant of HGF (hepatocyte growth factor) with a deletion of five amino acids, attracted our attention because it is less cytotoxic compared with HGF. METHODS: We evaluated growth, albumin production, metabolizing abilities of ammonia, lidocaine, and diazepam of human hepatocytes in the presence of dHGF (10-1000 ng/ml). The gene expression of liver markers was comparatively analyzed. The effect of intrasplenic transplantation of dHGF-treated human hepatocytes into severe combined immunodeficient (SCID) mice was evaluated in an acute liver failure (ALF) model induced by D-galactosamine (D-gal). RESULTS: When 100 ng/ml of dHGF was utilized, metabolism rates of ammonia, lidocaine, and diazepam and albumin production per unit cell significantly increased. The gene expression analysis demonstrated the enhanced expression of albumin, HNF-4alpha, and C/EBPalpha in the hepatocytes treated with 100 ng/ml of dHGF. Transplantation of such hepatocytes prolonged the survival of the SCID mice with ALF induced by D-gal. CONCLUSIONS: The present work clearly demonstrates the usefulness of dHGF (100 ng/ml) for maintaining the differentiated functions of human hepatocytes in tissue culture.     

Highly efficient generation of definitive endoderm lineage from human induced pluripotent stem cells

Background

Although hepatocytes can be an option for liver transplantation, the shortage of donor organs continues to worsen. Since the development of induced pluripotent stem (iPS) cell technology, it is eagerly anticipated to produce functional elements from pluripotent stem cells. These functional cells differentiated from iPS cells could be used for transplantation, drug screening, and in vitro toxicology.

Methods

Human iPS cells are maintained on Mitomycin C-treated mouse embryonic fibroblast layers in DMEM-Ham F12-based medium supplemented with Knockout Serum Replacement, nonessential amino acids, 2-mercaptoethanol, and Glutamax. Differentiation of human iPS cells into a definitive endodermal lineage was induced with PRMI 1640 medium supplemented with B27 and 100 ng/mL human activin A. Two B27 supplements were examined with and without insulin. Furthermore, the PI3 kinase inhibitor LY294002 was used to examine the effect of inhibiting insulin signaling.

Results and Discussion

We established efficient induction of definitive endodermal differentiation from iPS cells. Quantitative analysis revealed efficient (93.03 ± 2.74%) differentiation of human iPS cells into definitive endoderm cells using B27 minus insulin. This protocol may contribute as a fundamental technique to promote human iPS studies to develop cellular sources for transplantation.     

肝细胞生长因子诱导骨髓间充质干细胞向肝细胞分化的实验研究

目的探讨成年大鼠骨髓间充质干细胞(MSCs)在体外是否可定向诱导分化为肝细胞及其方法。方法采用梯度离心法,分离纯化SD大鼠的MSCs,流式细胞仪检测和碱性磷酸酶染色鉴定细胞类型。根据培养基中肝细胞生长因子(HGF)浓度不同,将MSCs分为4组进行诱导分化：A组0 ng／ml,B组10ng／ml,C组20ng／ml,D组40ng／ml。倒置显微镜连续观察细胞分化过程的形态学变化。于培养的1,3,7,14,21,28 d,分别以逆转录聚合酶链反应(RT-PCR)和细胞免疫组化检测各组细胞甲胎蛋白(AFP)、细胞角蛋白18(CK18)和白蛋白的基因和蛋白表达。结果分离纯化的SD大鼠MSCs的表面标志为CD29^ ,CD44^ ,CD34^-,CD45^-和CD90^ ,细胞的碱性磷酸酶染色阴性,细胞纯度达98％以上。C组与D组的MSCs,于培养第7天出现AFP基因表达,第14天表达增强,第28天表达减弱;第14天始出现白蛋白、CK18基因表达,而后持续。B组和A组在培养过程中,未出现AFP、CK18和白蛋白的表达。C组与D组MSCs的AFP细胞免疫组化染色培养第7天即出现阳性,第14天白蛋白和CK18免疫组化染色阳性。A组和B组的MSCs的AFP、白蛋白和CK18的免疫组化染色均阴性。结论成年大鼠MSCs在较高浓度的HGF的诱导下,可分化为肝细胞。     

细胞因子诱导小鼠骨髓间充质干细胞跨越分化肝细胞的研究

目的 探索骨髓问充质干细胞(MSCs)体外跨越分化为肝细胞的诱导体系.方法 从单核细胞中分离间充质干细胞,用添加20 ng/ml HGF、10 ng/ml FGF-4、10 ng/ml OSM和10%NBS的IMDM培养液诱导间充质干细胞向肝细胞分化.结果 经细胞因子诱导的细胞出现肝细胞样变化,随诱导时间延长体积逐渐增大、形态往上皮样转变,胞浆丰富,出现双核或多核细胞.RT-PCR和免疫荧光检测结果显示,AFP在诱导初期表达,在诱导后期表达下降;CKl8、ALB和TAT的表达与诱导时间呈线性关系.第20天达到表达高峰;诱导20 d后免疫荧光检测,AFP、CKl8、ALB和TAT均为阳性;诱导20 d细胞的PAS糖原合成反应呈阳性,即具备糖原合成和储存的肝细胞特有功能.结论 HGF、FGF-4和OSM三种细胞因子组合,可诱导小鼠间充质干细胞向肝细胞分化,该结果为间充质干细胞跨越分化肝细胞的分子机制探讨和临床应用打下了基础.     

Establishment of an immortalized porcine liver cell line JSNK-1 with retroviral transduction of SV40T

Maintenance of freshly isolated porcine liver cells in vitro is limited for a short period of time. Therefore, establishment of easy handling cell lines is extremely important for in vitro study for liver cells and their possible utilization for cell differentiation and growth of stem cells. Porcine liver cells were transduced with a retroviral vector SSR#69 expressing SV40T, one of SSR#69-immortalized porcine liver cell lines, JSNK-1, was established and characterized. Morphology of JSNK-1 cells was spindle shaped. When the cells became confluent, JSNK-1 cells revealed hills-and-valleys pattern. In the presence of vitamin A, JSNK-1 cells showed big droplets inside the cytoplasm, which were positive with PAS staining. JSNK-1 cells showed the gene expression of collagen type 1α1, collagen type 1α2, FLT-1, β-actin, and SV40T. Immunostaining study revealed that JSNK-1 cells produced collagen, vimentin, and α-smooth muscle actin. JSNK-1 cells possessed the characteristics of the liver stellate cells. JSNK-1 cells produced hepatocyte growth factor (HGF) in a time-dependent manner. When cocultured with iPS cells towards the hepatic differentiation, JSNK-1 cells facilitated their hepatic differentiation in terms of albumin production. In conclusion, JSNK-1 cells would be valuable in the study of liver stellate cell pathophysiology and contribute to the optimization of hepatic differentiation of iPS cells.     

人骨髓基质干细胞向肝细胞分化过程中白蛋白的表达研究

目的观察在体外诱导人骨髓基质干细胞向肝细胞分化过程中自蛋白的表达特征。方法从手术切除弃置的人肋骨骨髓中分离基质细胞,在含有肝细胞生长因子(HGF)、淋巴细胞抑制因子(UF)、纤维母细胞生长因子(FGF)等条件培养基中培养细胞。应用免疫荧光方法在共聚焦显微镜下观察肝细胞特异性白蛋白染色;同时,于诱导培养后多时间点测定培养细胞产生的白蛋白水平。结果人骨髓来源的基质干细胞在条件培养基中经诱导后,分化为成熟附壁细胞;细胞胞浆内肝细胞特异性标志物白蛋白呈阳性染色;已分化细胞合成并分泌白蛋白,其表达水平随细胞分化显示时间依赖性变化特征。结论人骨髓基质干细胞经诱导培养后可向成熟肝细胞分化并具有合成和分泌白蛋白功能,可以作为临床肝细胞移植及生物人工肝等治疗终末期肝病的重要肝细胞来源。     

骨髓间质干细胞培养上清液调控肝细胞的体外研究

目的探讨骨髓间质干细胞(bone marrow mesenchymal stem cells,BMSC)培养上清液对肝细胞增殖、凋亡的影响,初步探讨BMSC治疗肝纤维化的旁分泌机制。方法采用密度梯度离心及贴壁细胞分离相结合提取BMSC。培养48h的BMSC细胞培养上清液按BMSC不同处理(培养)时间和含量两种方法建组。不同处理时间建组:取培养48hBMSC上清液处理肝细胞(完全培养),分为处理24h、48h、72h组,对照组为1640培养基处理24h的肝细胞。不同含量BMSC建组:实验1组为完全BMSC培养上清液(含肝细胞的6孔板中每孔加入BMSC上清液2ml)处理肝细胞;实验2组为部分BMSC培养上清液(每孔加BMSC上清液1ml+1640培养基1ml)处理肝细胞;对照组为完全细胞培养基(每孔加1640培养基2ml)处理肝细胞。用酶联免疫吸附试验(ELISA)试剂盒检测BMSC旁分泌肝细胞生长因子(hepatocyte growth factor,HGF)情况及培养时间对其的影响;用流式细胞仪观察肝细胞细胞分期和检测凋亡细胞数;用蛋白免疫印迹法(Western-blot)检测样本上清液中白蛋白的表达。结果 BMSC分泌HGF,其含量变化具有时间依赖性。加入BMSC培养上清液后,与对照组相比,实验1组中的培养上清液可以明显促进肝细胞增殖、抑制其凋亡,并随着处理时间的延长而增加(处理72h>处理48h>处理24h,均为P<0.05);实验组(1组、2组)的白蛋白分泌较对照组上调,且随着处理时间的延长白蛋白含量增加。结论 BMSC有可能通过分泌HGF促进肝细胞增殖、抑制凋亡,促进白蛋白分泌,从而抑制肝脏纤维化。     

人脐血间充质干细胞在体外向肝样细胞的诱导分化

目的 探讨脐血间充质干细胞(MSCs)在体外能否分化成肝细胞.方法 分离人脐血MSCs,培养传代,流式细胞仪进行细胞表面标志检测.取培养至第三代的细胞,接种于六孔板内,分两个阶段进行细胞分化的诱导,第一阶段采用含地塞米松(终浓度为0.5 μmol/L,下同)、肝细胞生长因子(HGF,10 ng/ml)、表皮生长因子(10 ng/ml)及1×ITS(胰岛素-转铁蛋白-硒)的F12培养基诱导2周,第二阶段用含地塞米松(0.5 μmol/L)、HGF(10 ng/ml)、抑瘤素M(10 ng/ml)及1×ITS的F12培养基继续诱导2周.诱导期间于倒置显微镜下观察细胞的形态变化;采用逆转录聚合酶链反应检测分化细胞的甲胎蛋白(AFP)、白蛋白、人细胞角蛋白18(CK-18)及酪氨酸氨基转移酶(TAT)基因的表达,以免疫荧光染色法检测分化细胞胞浆中AFP、白蛋白、CK-18的表达;用电子显微镜观察分化细胞的超微结构.结果 培养的脐血MSCs不表达CD14、CD34及CD45,也不表达CD49f、CD54及HLA-DR;部分表达CD106;强表达CD13、CD29及CD44.未分化的脐血MSCs不表达AFP、TAT及白蛋白基因,弱表达CK-18基因;诱导分化1周后可检测到AFP基因的表达,诱导分化4周后,不仅表达AFP、CK-18和白蛋白基因,还表达TAT基因.免疫荧光染色显示,未分化的MSCs胞浆中无AFP、白蛋白及CK-18的表达;分化细胞则可以检测到上述物质的表达.诱导至第4周的分化细胞,可见核仁大且明显,细胞核周围有板层状的内质网,胞浆中可见脂滴及簇状糖原,线粒体丰富,细胞表面有微绒毛.结论 脐血MSCs在合适的诱导条件下可以分化为肝样细胞.     

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.     

诱导多能干细胞体外向生精细胞自发分化潜能的研究

目的:探讨诱导多能干细胞(iPS)体外培养自发分化过程中生精细胞相关基因的表达,评估iPS体外向生精细胞自发分化的潜能。方法:经类胚体(EB)形成,体外诱导iPS向生精细胞分化,实时定量PCR和PCR检测生精细胞相关基因的表达。结果:实时定量PCR和PCR结果显示iPS经EB形成诱导分化后生精细胞不同时期的相关基因均有不同程度表达。iPS体外培养自发分化后生精细胞相关基因出现4种时间表达特征:Oct4基因表达量呈波浪状上升;Dppa3和Stra8基因表达量随诱导时间延长而下降;Dazl基因表达量呈波浪状下降;减数分裂前期基因Tex14、Msy2,减数分裂期基因Scp1、Scp3以及单倍体基因Akap3随着诱导时间延长先表达增加,而后表达下降。结论:iPS在经EB自发分化过程中表达生精细胞不同时期的相关基因,并且表达雄性配子单倍体基因,具有向雄性配子的分化潜能。     

小鼠骨髓干细胞体外定向诱导为肝细胞样细胞的实验研究

目的来源于骨髓干细胞的有功能的干细胞,可能成为生物人工肝和肝细胞移植的细胞来源。我们建立恰当的体外诱导培养体系,促使骨髓干细胞转化为肝细胞。方法获取骨髓干细胞,建立以FGF、HGF、OSM、EGF为主的细胞诱导培养体系。在细胞分化过程中,观察细胞形态和数量的变化,RT-PCR检测基因表达的变化,免疫荧光染色技术在蛋白水平检测ALB和CK18表达情况。PAS染色检测其糖代谢功能。结果在诱导过程中,多极性的肝细胞样细胞在12 d内可以观察到,且其随着细胞分化过程逐渐增多、集落增大。诱导细胞在7 d内表达AFPmRNA并维持到第21天,但后期表达减弱;在7天内表达ALBmRNA和CK18mRNA,随着分化时间的延长,其表达不断增强;在14 d内表达TTRmRNA,随着分化时间的延长,其表达不断增强。免疫荧光染色进行定位:在诱导组,诱导21 d的细胞表达ALB和CK18,其中ALB表达于胞浆和胞膜,而CK18表达于胞浆。糖原染色发现诱导组中,细胞胞浆内出现大小不等的红染的糖原颗粒。结论我们建立的以细胞因子FGF、HGF、OSM、EGF为主的细胞诱导培养体系是有效的,通过诱导骨髓干细胞,我们获得了有部分肝细胞形态结构和功能的肝细胞样细胞。     

Propagation of adult rat bone marrow-derived hepatocyte-like cells by serial passages in vitro

Previously, we found that hepatocyte growth factor receptor (c-Met)-and alpha-fetoprotein (AFP)-expressing cells were present in adult rat bone marrow, and that these cells also expressed hematopoietic stem cell markers, such as CD34, Thy-1, and c-Kit. When bone marrow cells were cultured in a hepatocyte growth medium (HGM) with HGF and EGF, colonies composed of polygonal cells resembling mature hepatocytes appeared by 2 weeks and grew very slowly because of overgrowth of stromal cells. At days 34-41, 2-mm2 sheets of hepatocyte-like cells were cut out of their colonies by scratching with an injection needle under observation with a phase contrast microscope, transferred into wells of 24-well plates, and cultured in the HGM medium in the presence or absence of HGF and EGF. When cells reached confluence, cells were detached with trypsin and EDTA and transferred step by step into bigger culture vessels. Thus, hepatocyte-like cells were expanded 1000-fold during less than 4 months. These cells were immunocytochemically stained for albumin and also for AFP and the hematopoietic stem cell markers described above, showing characteristics of oval cells. By RT-PCR, we detected mRNAs of tryptophan-2,3-dioxygenase and tyrosine aminotransferase, markers of hepatocytes at a terminal differentiation stage. The present culture system may be useful for supply of hepatocyte resources for cell transplantation therapy.     

Serum Hyaluronate Level for Predicting Subclinical Liver Dysfunction after Hepatectomy

The serum hyaluronate (HA) level reflects sinusoidal endothelial cell function correlated with liver function. We have reviewed multiple liver function indicators from 37 patients who underwent hepatectomy for various liver diseases. The serum HA level was well correlated with the indocyanine green retention rate at 15 minutes (ICGR₁₅), lectin-cholesterol (LCAT), hepatocyte growth factor (HGF), liver uptake ratio of technetium-99m galactosyl human serum albumin (^99mTc-GSA) at 15 minutes (HH15), prealbumin, and hepatic uptake ratio of ^99mTc-GSA at 15 minutes (LHL15). In addition, the model for end-stage liver disease (MELD) score at 7 days after operation was well correlated with serum HA, ICGR₁₅, HH15, and LHL15. In patients who showed serum an HA level of = 100 ng/ml before hepatectomy, the MELD score had significantly deteriorated by 7 days after hepatectomy. Of the 20 patients who showed a serum HA level < 100 ng/ml before hepatectomy, 11 had high serum HA after hepatectomy. The bilirubin level 7 days after operation in this group was much higher than that for patients who maintained a serum HA level < 100 ng/ml after hepatectomy. In addition, the serum HGF level before hepatectomy in this group was significantly lower. We concluded that the serum HA level is a reliable indicator when evaluating liver function and predicting liver dysfunction after hepatectomy. Furthermore, patients with a significantly low HGF level who have a normal HA level are susceptible to liver dysfunction after hepatectomy.     

骨形成蛋白-2诱导脊髓神经干细胞分化的实验研究

目的：研究不同浓度的骨形成蛋白-2(bone norphogenetic protein-2，BMP-2)对脊髓源性神经干细胞(neural stem cells，NSCs)诱导分化成为神经细胞(神经元和神经胶质细胞)的影响。方法：取孕14d的胚胎小鼠脊髓，原代培养出脊髓NSCs。培养四代后，分别在碱性成纤维细胞生长因子(bFGF)存在与否的不同条件下，加入不同浓度的BMP-2．观察细胞的增殖、分化情况，用免疫组织化学的方法进行鉴定，并进行统计学分析：结果：低浓度的BMP-2(1～10ng／ml)与bFGF(20ng／ml)联合作用，可促进脊髓NSCs向神经元和星形胶质细胞分化，抑制其向少突胶质细胞分化。较高浓度BMP-2(100ng／ml)可抑制脊髓NSCs的增殖甚至导致细胞死亡。结论：脊髓NSCs在低浓度BMP和bFGF联合作用下能有效地分化成具有多种特性的神经样细胞，并与脊髓具有良好的同源性，可为脊髓损伤的修复研究提供良好的细胞学基础。