骨髓间充质干细胞向肝细胞分化的研究

骨髓间充质干细胞(MSC)是一类具有自我增殖和分化潜能的细胞.在特定条件诱导下可向多系细胞分化.近年来,MSC向肝系细胞分化的研究越来越受到人们的关注.一系列实验证明MSC在一定条件下可向肝细胞分化.其向肝细胞分化的机理以及诱导分化条件的优化还在进一步研究之中.     

Functional melanocytes derived from human pluripotent stem cells engraft into pluristratified epidermis

Melanocytes are essential for skin homeostasis and protection, and their defects in humans lead to a wide array of diseases that are potentially extremely severe. To date, the analysis of molecular mechanisms and the function of human melanocytes have been limited because of the difficulties in accessing large numbers of cells with the specific phenotypes. This issue can now be addressed via a differentiation protocol that allows melanocytes to be obtained from pluripotent stem cell lines, either induced or of embryonic origin, based on the use of moderate concentrations of a single cytokine, bone morphogenic protein 4. Human melanocytes derived from pluripotent stem cells exhibit all the characteristic features of their adult counterparts. This includes the enzymatic machinery required for the production and functional delivery of melanin to keratinocytes. Melanocytes also integrate appropriately into organotypic epidermis reconstructed in vitro. The availability of human cells committed to the melanocytic lineage in vitro will enable the investigation of those mechanisms that guide the developmental processes and will facilitate analysis of the molecular mechanisms responsible for genetic diseases. Access to an unlimited resource may also prove a vital tool for the treatment of hypopigmentation disorders when donors with matching haplotypes become available in clinically relevant banks of pluripotent stem cell lines.     

Embryoid-body cells derived from a mouse embryonic stem cell line show differentiation into functional hepatocytes

Embryonic stem (ES) cells have a potential to differentiate into various progenitor cells. Here we investigated the differentiation capacity of mouse ES cells into hepatocytes both in vitro and in vivo. During the culture of embryoid bodies (EBs) derived from ES cells, albumin (ALB) messenger RNA (mRNA) was expressed within 12 days after removal of leukemia inhibitory factor, and alpha-fetoprotein (AFP) mRNA was observed within 9 days without additional exogenous growth factors. In ES cells and early EBs, by contrast, neither ALB mRNA nor AFP mRNA was observed. ALB protein was first detected at day 15 and the level increased with the culture period. The differentiation of EBs facilitated the synthesis of urea with the culture period, whereas early EBs and ES cells produced no urea. These results suggest that cultured EBs contain hepatocytes capable of producing ALB and urea. ES cells and the isolated cells from EBs were transplanted through portal vein to the liver after 30% partial hepatectomy of female mice pretreated with 2-acetylaminofluorene. Four weeks after transplantation with isolated cells from day-9 EBs, ES-derived cells containing Y-chromosome in the liver were positive for ALB (0.2% of total liver cells), whereas teratoma was found in mice transplanted with ES cells or EBs up to day 6. The incidence of teratoma was decreased with the culture duration and no teratoma was observed in the liver transplanted with isolated cells from day-9 EBs. In conclusion, our in vitro and in vivo experiments revealed that cultured EBs contain functional hepatocytes or hepatocyte-like cells.     

脐血干细胞转化为肝细胞的研究进展

自进行第1例脐血干细胞移植以来,各国科研机构相继开展对于脐血干细胞的研究,脐血库也纷纷建立．随着再生医学的发展,众多国内外学者在尝试进行非肝源性细胞向肝细胞分化方面的研究,并已经证实脐血干细胞在特定的微环境下可以在体内和体外转化为肝样细胞,为脐血干细胞在肝脏疾病中的应用奠定了基础．本文就脐血干细胞向肝细胞转化的最新研究进展作一综述．     

Fate of extrahepatic human stem and precursor cells after transplantation into mouse livers

In recent years, a large number of groups studied the fate of human stem cells in livers of immunodeficient animals. However, the interpretation of the results is quite controversial. We transplanted 4 different types of human extrahepatic precursor cells (derived from cord blood, monocytes, bone marrow, and pancreas) into livers of nonobese diabetic/severe combined immunodeficiency mice. Human hepatocytes were used as positive controls. Tracking of the transplanted human cells could be achieved by in situ hybridization with alu probes. Cells with alu-positive nuclei stained positive for human albumin and glycogen. Both markers were negative before transplantation. However, cells with alu-positive nuclei did not show a hepatocyte-like morphology and did not express cytochrome P450 3A4, and this suggests that these cells represent a mixed cell type possibly resulting from partial transdifferentiation. Using antibodies specific for human albumin, we also observed a second human albumin-positive cell type that could be clearly distinguished from the previously described cells by its hepatocyte-like morphology. Surprisingly, these cells had a mouse and not a human nucleus which is explained by transdifferentiation of human cells. Although it has not yet been formally proven, we suggest horizontal gene transfer as a likely mechanism, especially because we observed small fragments of human nuclei in mouse cells that originated from deteriorating transplanted cells. Qualitatively similar results were obtained with all 4 human precursor cell types through different routes of administration with and without the induction of liver damage. CONCLUSION: We observed evidence not for transdifferentiation but instead for a complex situation including partial differentiation and possibly horizontal gene transfer.     

损伤肝脏条件培养液体外诱导小鼠骨髓间充质干细胞分化为肝细胞

目的探索损伤肝脏条件培养液体外诱导小鼠骨髓间充质干细胞（MSCs）分化为肝细胞的可行性及方法。方法培养注射CCl4所致的损伤小鼠肝脏组织块,收集条件培养液,进行MSCs诱导分化。通过形态学观察、RT-PCR、免疫荧光反应和过碘酸Schiff反应鉴定分化细胞。结果诱导组细胞呈肝细胞样变化。RT-PCR检测显示：AFP基因第5天开始表达,第10天表达增强,此后表达减弱；细胞角蛋白18和Alb基因第10天开始表达,持续到第20天；第20天检测到酪氨酸氨基转移酶基因表达。免疫荧光反应显示诱导20 d的细胞AFP、细胞角蛋白18、Alb表达阳性,诱导20 d细胞过碘酸Schiff反应呈阳性。结论MSCs在损伤肝脏条件培养液诱导下可分化为肝细胞。     

脐带间充质干细胞体外诱导分化为肝细胞样细胞的研究

目的探讨人脐带间充质干细胞（UC-MSCs）体外诱导分化为肝细胞的可行性和方法,观察分化后的细胞白细胞表面抗原表达的改变。方法采用酶学法从脐带全层组织中分离UC-MSCs,采用改良的肝分化培养体系体外诱导UC-MSCs向肝细胞分化。诱导后2、4周,观察细胞形态,免疫荧光细胞化学染色法检测甲胎蛋白（AFP）、白蛋白（ALB）;RT-PCR检测肝细胞标志性基因AFP、ALB和CK19 mRNA。ELISA法检测诱导后的细胞培养液中ALB水平。流式细胞仪检测诱导后细胞白细胞表面抗原HLA-Ⅰ和HLA-Ⅱ。结果从人脐带基质中分离培养的UC-MSCs在向肝细胞诱导分化培养体系的培养下,细胞形态由长梭形逐渐转化成为多角形或类圆形,并且表达AFP、ALB mRNA和蛋白,诱导后的UC-MSCs以时间依赖方式产生ALB,诱导后的细胞不表达HLA-DR。结论UC-MSCs具有向肝细胞分化的潜能,分化后的M细胞仍具有低免疫原性。     

胎肝来源间充质干细胞的分离、培养与多向分化

目的从胎肝中分离培养间充质下细胞，并研究其牛物学特性。方法用优化的方法从胎肝中分离获得间充质干细胞。利用流式细胞仪分析细胞表型和细胞周期分布，并体外诱导成骨、成脂肪和成肝组织细胞分化。并用染色方法鉴定成骨、成脂肪分化结合形态学方法和RT-PCR方法鉴定成肝组织分化结果。结果从胎肝中分离培养的细胞为成纤维样，贴壁生长．表型相对均一，表面标志为CD90，CD44，CD147，而CD34，CD45，HLA-DR，具有向肝组织分化的潜能，并可向成骨和成脂肪分化。结论从胎肝中可分离培养得到具有多向分化潜能的间充质干细胞。     

骨形态发生蛋白2在骨髓间充质干细胞向肝细胞分化中的作用

目的：观察骨形态发生蛋白2（BMP2）在骨髓间充质干细胞（BMSCs）向肝细胞分化中的作用。方法采用贴壁法分离培养大鼠股骨BMSCs ,将体外扩增的第3代BMSCs制作细胞爬片,并行肝细胞定向诱导。根据诱导因子不同分为：肝细胞生长因子（ HGF）组、HGF＋BMP2组、BMP2组及空白对照组。培养10 d左右收集细胞,观察各组细胞形态的变化,并采用ELISA法检测培养液上清中肝细胞特异性标志物甲胎蛋白（ AFP）、白蛋白（ ALB）,免疫细胞化学法检测诱导分化后细胞CK-18的表达。结果 HGF组和HGF＋BMP2组可检测到ALB、AFP及CK-18,且HGF＋BMP2组ALB、AFP及CK-18明显高于HGF组（P均＜0．05）。结论 BMP2不能单独诱导BMSCs向肝细胞分化,但能增强HGF诱导BMSCs向肝细胞分化的作用。     

利用共培养法诱导人胎盘间充质干细胞向成骨细胞分化

目的观察体外人足月胎盘间充质干细胞(h PMSCs)和成骨细胞共培养体系条件下成骨细胞对h PMSCs分化的影响。方法采用胶原酶消化法从人足月胎盘中分离纯化间充质干细胞(MSCs),检测细胞表面标志物、生长曲线、细胞超微结构及成骨能力并对h PMSCs进行鉴定。共培养组将成骨细胞接种于Transwell双层培养皿底层,h PMSCs接种于上层;对照组上层与底层均接种h PMSCs。对诱导后细胞进行碱性磷酸酶染色鉴定。结果胎盘分离细胞经形态、生长速度、细胞表面标志物(CD44和CD29阳性表达为99%,CD34和CD106为1%),确定为胎盘间充质干细胞;头盖骨分离细胞经碱性磷酸酶染色确定为成骨细胞。采用Transwell共培养h PMSCs和成骨细胞组碱性磷酸酶活性染色阳性率为(21.7±5.3)%,表现成骨细胞特性,对照组染色呈阴性。结论人足月胎盘含MSCs,与其他来源MSCs生物学特性相似,成骨细胞生长过程提供的微环境对h PMSCs分化为成骨细胞具有诱导促进作用。     

磁标记大鼠间充质干细胞肝脏移植的磁共振成像活体示踪

目的探讨1.5 T MRI活体示踪磁标记干细胞经门静脉肝脏移植的可行性。方法大鼠间充质干细胞以菲立磁和DAPI标记后,经门静脉注入大鼠肝脏,分别于移植前及移植后1 h、3 d、7 d和14 d行MRI扫描,并与组织荧光显像和铁染色对照。结果移植后1 h、3 d、7 d及14 d肝脏信噪比分别为1.10±0.26、8.18±1.55、11.08±1.30、14.15±1.02,7 d以内肝脏信噪比与移植前比较均有明显降低(P<0.05)。各时相肝组织铁染色与荧光显像的空间分布一致。结论1.5 T MRI活体示踪经门静脉移植的磁标记干细胞是可行的,MRI示踪时间可持续7 d。     

Rat bone marrow mesenchymal stem cells differentiate into hepatocytes in vitro

AIM: To investigate the mechanism and regulation of differentiation from bone marrow mesenchymal stem cells (MSCs) into hepatocytes and to find a new source of cell types for therapies of hepatic diseases. METHODS: MSCs were isolated by combining gradient density centrifugation with plastic adherence. The cells were cultured in osteogenic or adipogenic differentiation medium and determined by histochemical staining. MSCs were plated in plastic culture flasks that were not coated with components of extracellular matrix (ECM). When MSCs reached 70% confluence, they were cultured in low glucose Dulbecco's modified Eagle's medium supplemented with 10 mL/L fetal bovine serum, 20 ng/mL hepatocyte growth factor (HGF) and 10 ng/mL fibroblast growth factor-4 (FGF-4). The medium was changed every 3 d and stored for albumin, alpha-fetoprotein (AFP) and urea assay. Glycogen store of hepatocytes was determined by periodic acid-Schiff staining. RESULTS: By combining gradient density centrifugation with plastic adherence, we isolated a homogeneous population of cells from rat bone marrow and differentiated them into osteocytes and adipocytes. When MSCs were cultured with FGF-4 and HGF, approximately 56.6% of cells became small round and epithelioid on d 24 by morphology. Compared with the control, levels of AFP increased significantly from d 12 to 15.5±1.4 μg/L (t = 2.31,P<0.05) in MSCs cultured with FGF-4 and HGF, and were higher (46.2±1.5 μg/L) on d 21 (t = 41.926, P<0.01), then decreased to 24.8±2.2 μg/L on d 24 (t = 10.345, P<0.01). Albumin increased significantly on d 21 (t = 3.325,P<0.01) to 1.4±0.2 μg/mL, and to 2.1±0.7 μg/mL on d 24 (t= 3.646, P<0.01). Urea (2.3±0.4 mmol/L) was first detected on d 21 (t= 6.739, P<0.01), and continued to increase to 2.6±0.9 mmol/L on d 24 (t = 4.753, P<0.01). Glycogen storage was first seen on d 21. CONCLUSION: The method combining gradient density centrifugation with plastic adherence can isolate MSCs. Rat MSCs may be differentiated into hepatocytes by FGF-4 and HGF. Cytokines may play a more important role in differentiation from rat MSCs into hepatocytes.     

Adipose tissue-derived mesenchymal stem cells as a source of human hepatocytes

Recent observations indicate that several stem cells can differentiate into hepatocytes; thus, cell-based therapy is a potential alternative to liver transplantation. The goal of the present study was to examine the in vitro hepatic differentiation potential of adipose tissue-derived mesenchymal stem cells (AT-MSCs). We used AT-MSCs from different age patients and found that, after incubation with specific growth factors (hepatocyte growth factor [HGF], fibroblast growth factor [FGF1], FGF4) the CD105(+) fraction of AT-MSCs exhibited high hepatic differentiation ability in an adherent monoculture condition. CD105(+) AT-MSC-derived hepatocyte-like cells revealed several liver-specific markers and functions, such as albumin production, low-density lipoprotein uptake, and ammonia detoxification. More importantly, CD105(+) AT-MSC-derived hepatocyte-like cells, after transplantation into mice incorporated into the parenchyma of the liver. CONCLUSION: Adipose tissue is a source of multipotent stem cells that can be easily isolated, selected, and induced into mature, transplantable hepatocytes. The fact that they are easy to procure ex vivo in large numbers makes them an attractive tool for clinical studies in the context of establishing an alternative therapy for liver dysfunction.     

MSCs分化为功能性肝细胞的研究进展

间充质干细胞(mesenchymal stemcells,MSCs)来源于中胚层间充质,广泛存在于骨髓、脐带组织、脐血、外周血、脂肪等组织中.在特定条件下,可以分化为骨、脂肪、神经细胞及肝细胞等多种细胞,进而作为一种替代器官移植的新的治疗方法.近年来,肝硬化等终末期肝病的发病率日益上升,成为影响人类健康的重大疾病之一.肝源紧张、免疫排斥限制了肝移植的临床应用,然而众多研究证实MSCs对肝纤维化、肝硬化等肝病的治疗作用可能与其分化为功能性肝细胞有关,但具体机制尚不十分清楚.本文就MSCs的分化能力及其分化的调控、分子机制和不同来源干细胞对肝纤维化的治疗作用作一综述.     

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。     

大鼠脂肪间充质干细胞在部分肝切除模型中向肝细胞分化的研究

目的探讨脂肪间充质干细胞（ADMSCs）在部分肝切除模型中向肝细胞的分化。方法从大鼠脂肪组织中分离出干细胞，并进行体外扩增、传代，取第2代ADMSCs用PKH26标记，制作部分肝切除模型，将标记细胞经门静脉自体植入体内。2周后切下肝脏制成冰冻切片，荧光显微镜下观察标记细胞在肝脏的定位，进行免疫荧光染色检测标记细胞白蛋白的表达。结果从脂肪组织中分离出的ADMSCs能在体外大量扩增，PKH26标记后细胞在荧光显微镜下发红色荧光，细胞标记率约95％；荧光显微镜下可见肝脏冰冻切片中散在分布红色标记细胞，免疫荧光染色显示大多数标记细胞白蛋白染色阳性。结论 大鼠脂肪间充质干细胞在肝再生环境中能向肝细胞分化，有可能在肝部分切除后参与肝再生。