人鼠嵌合肝模型的建立与鉴定

动物模型在肝病学的发展中起重要作用。近几年，在了解特异基因功能、代谢通路和疾病进程方面，啮齿类动物模型发挥了巨大作用。人鼠嵌合肝是利用人肝细胞异种移植到受体鼠肝内建立的新型动物模型。受体鼠可分为免疫缺陷小鼠或诱导免疫耐受大鼠^[1,2]，两者均能初步建立HBV感染的人鼠嵌合肝动物模型。本文主要介绍人鼠嵌合肝相关内容，包括移植细胞来源、建立途径、     

L02细胞人鼠嵌合肝模型的建立

目的 研究正常人L02肝细胞移植到具有正常免疫活性的大鼠肝内的存活情况，建立稳定的人鼠嵌合肝动物模型。方法 SD大鼠出生前宫内腹腔注射L02肝细胞，诱导胎鼠对人L02肝细胞产生免疫耐受，出生2周后经脾移植DiI染色后的人L02肝细胞，建立人鼠嵌合肝动物模型。采用免疫荧光、免疫组织化学、DiI荧光示踪等方法，在不同时相分别检测人白蛋白和特异性人增殖细胞核抗原，在荧光显微镜下观察人L02肝细胞在鼠肝内的分布。结果 于移植后1、2、4、6、8、10周在荧光显微镜下观察到人L02肝细胞在鼠肝内的动态分布，移植后2、4、6、8周大鼠均检测出人白蛋白，移植后2、4、6周检测出特异性人增殖细胞核抗原。结论 移植的人L02肝细胞在具有正常免疫活性的免疫耐受鼠体内能够存活、增殖，并产生人白蛋白。     

抗CD+4人-鼠嵌合抗体对哮喘患者淋巴细胞增殖和凋亡的影响

目的　观察抗 Ｃ Ｄ＋４ 人鼠嵌合抗体对哮喘发作期患者外周血淋巴细胞体外增殖及凋亡的作用。方法　取哮喘患者外周血淋巴细胞,分别加入５０ ｍｇ／ Ｌ、１００ ｍｇ／ Ｌ 抗 Ｃ Ｄ＋４ 人鼠嵌合抗体, 采用流式细胞仪及原位末端标记法观察其对经抗 Ｃ Ｄ＋３ 单抗诱导的体外培养０ 、２４ 、４８ 小时淋巴细胞凋亡的影响,同时采用四甲基偶氮唑盐（ Ｍ Ｔ Ｔ） 微量比色法观察其对淋巴细胞增殖的影响。结果　哮喘患者淋巴细胞经抗 Ｃ Ｄ＋３ 单抗诱导培养２４ 小时（３３ ±０７） ％ 及４８ 小时（５２ ±１５） ％ 凋亡细胞阳性率与正常人２４ 小时（６５ ±３３） ％ 、４８ 小时（８９ ±３０） ％ 比较,差异有显著性（ Ｐ＜ ００５） ; 淋巴细胞增殖反应（０２９０ ±００１３） 与正常组（０２２０ ±００１５） 比较差异有显著性（ Ｐ＜ ００５） ;５０ ｍｇ／ Ｌ、１００ ｍｇ／ Ｌ 抗 Ｃ Ｄ＋４人鼠嵌合抗体均可显著增加哮喘患者淋巴细胞凋亡数量［５０ ｍｇ／ Ｌ：２４ 小时为（１４２０ ±２２０） ％ ,４８ 小时为（３３ ±４） ％ ;１００ ｍｇ／ Ｌ：２４ 小时为（２１ ±５） ％ ,４８ 小时为（４００ ±２７） ％ ］ ,两者比较     

L02细胞建立人鼠嵌合肝动物模型

目的:研究L02细胞移植到具有正常免疫活性的大鼠肝内的存活情况.方法:SD大鼠出生前宫内腹腔注射正常人L02肝细胞,诱导胎鼠对人L02肝细胞产生免疫耐受,出生2wk时经脾移植DiI染色后的人L02肝细胞,建立人鼠嵌合肝动物模型.采用免疫荧光、SP免疫组化、DiI荧光示踪等方法,分别检测人白蛋白、特异性人增殖细胞核抗原PCNA(proliferatingcellnuclearantigen)以及在荧光显微镜下观察人L02肝细胞在鼠肝内的分布.结果:于移植后1,2,4,6,8,10wk在荧光显微镜下观察到人L02肝细胞在鼠肝内的动态分布;移植后2,4,6,8wk大鼠均检测出人白蛋白,4wk时分泌最多;移植后2,4,6wk检测出特异性人增殖细胞核抗原PCNA,以4wk发现PCNA阳性细胞最多.结论:移植的人L02肝细胞在具有正常免疫活性的免疫耐受鼠体内能够存活、增殖,并产生人白蛋白.     

倒千里光碱增强L02细胞在人鼠嵌合肝中的增殖能力

建立稳定持久的人鼠嵌合肝动物模型,必须提高移植细胞的增殖能力。倒千里光碱与部分肝切除术(RtS/PH)联合应用,是移植肝细胞增殖常用模式。我们对诱导免疫耐受的大鼠腹腔注射倒千里光碱,2周后行2/3肝切除术,同时经脾移植1,1’2双十八烷23,2,3’,3’2四甲基吲哚羧花2高氯酸盐(Dil,美国Sigma公司)染色后的L02细胞,建立Rts/PH肝细胞增殖模型。采用免疫荧光、Dil荧光示踪     

人鼠嵌合肝小鼠模型的建立及在HBV致病研究中的应用

病毒性肝炎一直是全球范围内一个沉重的肝病负担,其中以乙型肝炎最为严重。由于HBV仅感染灵长类动物,因此其所致肝病很难在动物模型中被复制。人鼠嵌合肝小鼠模型是指将人源肝细胞移植入免疫缺陷的肝损伤小鼠肝内而形成的嵌合体小鼠。由于小鼠肝内嵌合有人肝细胞,可以在其体内模拟HBV的感染,利于进行进一步的机制研究。目前该模型主要以白蛋白启动子调控尿激酶(Alb-uPA)小鼠模型和延胡索酰乙酰乙酸水解酶(Fah~(-/-))小鼠模型为基础,在人源肝组织和外周血中均可检测到HBV,并已应用于HBV突变、HBV基因功能、抗病毒药物效果以及HBV与免疫系统的相互作用等方面的研究。本文就传统HBV感染动物模型的利弊、人鼠嵌合肝小鼠模型的研究进展和改进方法进行综述。     

白细胞介素-10对肝星状细胞增殖及表达Fas/Fas配体的影响

研究拟通过观察外源性血小板衍生生长因子(PDGF)和白细胞介素-10(IL-10)干预后肝星状细胞(HSC)增殖及凋亡相关基因Fas/FasL表达的变化,进一步探讨PDGF致纤维化和IL-10抗肝纤维化的机制。     

肝再生刺激因子、胰岛素和胰高血糖素对体外肝细胞增殖的作用

本研究采用体外细胞培养分组对比法检测肝再生刺激因子（HSS），胰岛素或／胰高血糖素对大鼠原代培养肝细胞和人肝肿瘤细胞株HEPg2DNA合成（肝细胞再生）的作用。结果发现，HSS无论对大鼠肝细胞成人肝肿瘤细胞均具有较强的刺激DNA合成的作用（与对照组相比分别增加1．14和1．05倍，P＜0．01）。而对人纤维母细胞则无促进DNA的合成的作用。低浓度胰岛素或／和胰高血糖素对肝细胞DNA合成无作用。高浓度胰岛素（10^-5M)具有中等度促进肝再生的作用（与对照组相比增加40％，P＜0．05）。两者联合应用（G＋1）似无协同作用。据此，我们认为：HSS是一种潜在的促进肝再生的有效因素，可能具有临床实用价值。体外应用优于现在临床广泛应用的胰岛素加胰高血糖素（G＋I）疗法。     

Repopulation of adult and neonatal mice with human hepatocytes: a chimeric animal model

We report the successful transplantation of human hepatocytes in immunodeficient, fumarylacetoacetate hydrolase-deficient (fah(-/-)) mice. Engraftment occurs over the entire liver acinus upon transplantation. A few weeks after transplantation, increasing concentrations of human proteins (e.g., human albumin and human C3a) can be measured in the blood of the recipient mouse. No fusion between mouse and human hepatocytes can be detected. Three months after transplantation, up to 20% of the mouse liver is repopulated by human hepatocytes, and sustained expression of lentiviral vector transduced gene can be observed. We further report the development of a hepatocyte transplantation method involving a transcutaneous, intrahepatic injection in neonatal mice. Human hepatocytes engraft over the entire injected lobe with an expansion pattern similar to those observed with intrasplenic transplantation.     

Repopulation of mouse liver with human hepatocytes and in vivo infection with hepatitis B virus

Mice containing livers repopulated with human hepatocytes would provide excellent in vivo models for studies on human liver diseases and hepatotropic viruses, for which no permissive cell lines exist. Here, we report partial repopulation of the liver of immunodeficient urokinase-type plasminogen activator (uPA)/recombinant activation gene-2 (RAG-2) mice with normal human hepatocytes isolated from the adult liver. In the transplanted mice, the production of human albumin was demonstrated, indicating that human hepatocytes remained functional in the mouse liver for at least 2 months after transplantation. Inoculation of transplanted mice with human hepatitis B virus (HBV) led to the establishment of productive HBV infection. According to human-specific genomic DNA analysis and immunostaining of cryostat liver sections, human hepatocytes were estimated to constitute up to 15% of the uPA/RAG-2 mouse liver. This is proof that normal human hepatocytes can integrate into the mouse hepatic parenchyma, undergo multiple cell divisions, and remain permissive for a human hepatotropic virus in a xenogenic liver. This system will provide new opportunities for studies on etiology and therapy of viral and nonviral human liver diseases, as well as on hepatocyte biology and hepatocellular transplantation.     

Repopulation of rat liver by fetal hepatoblasts and adult hepatocytes transduced ex vivo with lentiviral vectors

Recent studies have shown that nondividing primary cells, such as hepatocytes, can be efficiently transduced in vitro by human immunodeficiency virus-based lentivirus vectors. Other studies have reported that, under certain conditions, the liver can be repopulated with transplanted hepatocytes. In the present study, we combined these procedures to develop a model system for ex vivo gene therapy by repopulating rat livers with hepatocytes and hepatoblasts transduced with a lentivirus vector expressing a reporter gene, green fluorescent protein (GFP). Long-term GFP expression in vivo (up to 4 months) was achieved when the transgene was driven by the liver-specific albumin enhancer/promoter but was silenced when the cytomegalovirus (CMV) enhancer/promoter was used. Transplanted cells were massively amplified ( approximately 10 cell doublings) under the influence of retrorsine/partial hepatectomy, and both repopulation and continued transgene expression in individual cells were documented by dual expression of a cell transplantation marker, dipeptidyl peptidase IV (DPPIV), and GFP. In this system, maintenance or expansion of the transplanted cells did not depend on expression of the transgene, establishing that positive selection is not required to maintain transgene expression following multiple divisions of transplanted, lentivirus-transduced hepatic cells. In conclusion, fetal hepatoblasts (liver stem/progenitor cells) can serve as efficient vehicles for ex vivo gene therapy and suggest that liver-based genetic disorders that do not shorten hepatocyte longevity or cause liver damage, such as phenylketonuria, hyperbilirubinemias, familial hypercholesterolemia, primary oxalosis, and factor IX deficiency, among others, might be amenable to treatment by this approach.     

Tumor radioimmunoimaging of chimeric antibody in nude mice with hepatoma xenograft

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Antirheumatic effects of humanized anti-Fas monoclonal antibody in human rheumatoid arthritis/SCID mouse chimera

OBJECTIVE: Anti-Fas monoclonal antibodies (Mab) are considered to be a potential therapeutic agent for rheumatoid arthritis (RA). However, Fas mediated liver and chondrocyte damage is a serious problem in its clinical application. m-HFE7A, a novel anti-Fas Mab, selectively induces apoptosis in inflammatory cells. We succeeded in humanizing m-HFE7A to obtain h-HFE7A. We investigated the therapeutic effects of h-HFE7A Mab in RA. METHODS: We investigated the apoptosis-inducing activities of h-HFE7A on human Fas ligand transfected cells and cultured human activated lymphocytes (human peripheral blood mononuclear cells and isolated human RA synovial lymphocytes), synoviocytes, and chondrocytes. We then examined the effects of h-HFE7A Mab in vivo using SCID-HuRAg mice implanted with human RA tissue. RESULTS: Administration of h-HFE7A Mab alone did not induce apoptosis in cultured human Fas ligand transfected cells and activated lymphocytes. However, apoptosis-inducing activities were noted by this Mab crosslinking with a secondary antibody or Fcgamma receptor positive cells. In contrast, no apoptosis induction by h-HFE7A was observed on cultured synoviocytes and chondrocytes with or without crosslinking. Thus the crosslinking with Fcgamma receptor positive cells is essential for the efficacy of this Mab in vivo. In the implanted tissue of the SCID-HuRAg mice, the number of inflammatory cells was significantly decreased in the h-HFE7A Mab treated group compared to the IgG treated control group. Moreover, there were only negligible effects in synoviocytes and chondrocytes with the h-HFE7A Mab. CONCLUSION: Administration of this novel humanized anti-Fas Mab may provide a new treatment for RA by inducing Fas mediated apoptosis in inflammatory cells.     

L02细胞在2-乙酰氨基芴处理大鼠肝中的增殖

目的:应用2-乙酰氨基芴(2-acetaminofluorene, 2-AAF),研究L02细胞移植到具有正常免疫性的大鼠肝内的存活与增殖情况．方法:SD大鼠出生前宫内ip正常人L02肝细胞,诱导胎鼠对L02肝细胞产生免疫耐受,出生2 wk时分别ip小(1．2 mg／kg)、中(13 mg／kg)、大剂量(30 mg／kg)2-乙酰氨基芴或生理盐水,隔日行2／3肝切除术,同时经脾移植DiI染色后的人L02肝细胞,建立2-AAF／PH肝细胞增殖模型．采用免疫荧光、RT-PCR、免疫组化、DiI荧光示踪等方法,在不同时相分别检测人白蛋白、人白蛋白mRNA、增殖细胞核抗原(PCNA)以及在荧光显微镜下观察人L02肝细胞在鼠肝内的分布,并采用计算机图像分析系统分析不同时相PCNA阳性细胞的数密度和面积密度．结果:2-乙酰氨基芴实验组(小、中、大剂量)的各项检测,均与对照组无明显区别;于移植后1,2,4,6,8,10 wk在荧光显微镜下观察到人L02肝细胞在鼠肝内的动态分布;移植后2, 4,6,8 wk大鼠均检测出人白蛋白及人白蛋白mRNA;移植后2,4,6 wk检测出特异性人增殖细胞核抗原PCNA,移植后1,2,4,6,8 wk检测出非特异性PCNA．结论:2-AAF／PH模型中,2-乙酰氨基芴对移植L02细胞无明显增殖作用;L02细胞在2-乙酰氨基芴处理人鼠嵌合肝动物模型中存活10 wk,产生白蛋白功能持续8 wk．     

Human liver chimeric mouse model based on diphtheria toxin-induced liver injury

AIM To establish an inducible liver injury mouse model and transplant human hepatocytes to obtain liverhumanized mice.METHODS We crossed three mouse strains,including albumin(Alb)-cre transgenic mice,inducible diphtheria toxin receptor(DTR) transgenic mice and severe combined immune deficient(SCID)-beige mice,to create Alb-cre/DTR/SCID-beige(ADSB) mice,which coincidentally harbor Alb-cre and DTR transgenes and are immunodeficient. As the Cre expression is driven by the liver-specific promoter Alb(encoding ALB),the DTR stop signal flanked by two lox P sites can be deleted in the ADSB mice,resulting in DTR expression in the liver. ADSB mice aged 8-10 wk were injected intraperitoneally(i.p.) with diphtheria toxin(DT) and liver damage was assessed by serum alanine aminotransferase(ALT) level. Two days later,mouse livers were sampled for histological analysis,and human hepatocytes were transplanted into the livers on the same day. A human ALB enzyme-linked immunosorbent assay was performed 7,14,21 and 28 d after transplantation. Human CD68 immunohistochemistry was performed 30 and 90 d after transplantation.RESULTS We crossed Alb-cre with DTR and SCID-beige mice to obtain ADSB mice. These mice were found to have liver damage 4 d after i.p. injection of 2.5 ng/g bodyweight DT. Bodyweight began to decrease on day 2,increased on day 7,and was lowest on day 4(range,10.5%-13.4%). Serum ALT activity began to increase on day 2 and reached a peak value of 289.7 ± 16.2 IU/m L on day 4,then returned to background values on day 7. After transplantation of human liver cells,peripheral blood human ALB level was 1580 ± 454.8 ng/m L(range,750.2-3064.9 ng/m L) after 28 d and Kupffer cells were present in the liver at 30 d in ADSB mice.CONCLUSION Human hepatocytes were successfully repopulated in the livers of ADSB mice. The inducible mouse model of humanized liver in ADSB mice may have functional applications,such as hepatocyte transplantation,hepatic regeneration and drug metabolism.     

A tamoxifen-inducible chimeric Cre recombinase specifically effective in the fetal and adult mouse liver

The spatiotemporal control of somatic mutagenesis in mice is considered a promising step to determine the function of a given gene product in a defined population of cells at any given time during animal life and also to generate better mouse models of human diseases. To introduce defined mutations in a temporally controlled manner in the liver, we established transgenic mice expressing a tamoxifen-inducible Cre recombinase under the control of the transthyretin promoter (TTR-Cre ind). The recombinase activity was examined on 2 different floxed alleles by crossing TTR-Cre ind mice with either the reporter strain ROSA 26 or with homozygous mice carrying floxed catalytic alpha2 subunit of the adenosine monophosphate (AMP)-activated protein kinase gene. By placing 2 mutated hormone-binding domains of murine estrogen receptor (Mer) at both termini of the Cre, we show that the fusion protein is active only on administration of the synthetic estrogen antagonist 4-hydroxytamoxifen (4-OHT) without any background in the absence of the inducing agent. The recombination is specific of the fetal and adult liver, and we show that the efficiency of recombination reached 80% to 100% after treatment with 4-OHT. In conclusion, TTR-Cre ind transgenic mice represent a valuable tool for temporally controlling the desired gene modifications in vivo in the fetal and adult liver. This would certainly help to understand the physiologic functions of genes in the liver, to create various mouse models mimicking human diseases, and to contribute to liver cancer-specific suicide gene therapy studies.