Human Pharmacogenetics and Human Liver Regeneration

描述（由申请人提供）：我们已经开发出一种新的方法来生产具有完全成熟和功能的人类肝脏组织的嵌合小鼠，该嵌合小鼠在没有任何持续的肝脏病理和持续的药物治疗的情况下保持。该模型系统克服了严重限制现有模型效用的实质问题（肾脏和肝脏病理、寿命短、肝脏置换不完全）。为此，研究人员对一只免疫功能高度低下（NOG）的小鼠进行基因工程改造，使其在肝脏中表达胸苷激酶转基因，从而在给药一种无毒药物（更昔洛韦）后，对小鼠肝脏组织进行暂时控制和组织特异性消融。注射人肝细胞后，受体小鼠具有高水平的人肝原位重建，存活时间比其他任何模型都要长（约8个月）；并具有成熟人肝脏的基因表达谱和三维结构特征。首先，该平台将用于开发新的移植方法，使人类肝脏干细胞、人类诱导多能上皮细胞（hiPS）或人类脂肪细胞来源的干细胞能够重建人类肝脏。如果成功，这将使治疗终末期肝病的范式发生彻底转变：“肝移植”可以使用自体细胞进行，而不需要免疫抑制。其次，通过对供体人类肝细胞进行基因分型，将产生一组具有“人源化肝脏”的小鼠，这些小鼠具有用于I期药物代谢的特定等位基因。然后，将分析至少3种药物的人类特异性药物代谢物的形成速率，这些药物的代谢依赖于人类CYP450酶的活性。如果成功，这一创新的模型系统将使药物遗传学分析能够在完全人类环境下有效地进行，并控制所有混杂的环境变量，这将克服表征药物代谢个体间差异的重大障碍。

DESCRIPTION (provided by applicant): We have developed a novel method for producing chimeric mice with fully mature and functional human liver tissue, which is maintained in the absence of any ongoing liver pathology and without continued drug treatment. This model system overcomes the substantial problems (kidney and liver pathology, short lifespan, incomplete liver replacement) that have significantly limited the utility of existing models. To do this, a highly immunocompromised (NOG) mouse was genetically engineered to express a thymidine kinase transgene in the liver, which enabled the temporally controlled and tissue-specific ablation of mouse liver tissue after administration of a non-toxic drug (gancyclovir). After injection of human liver cells, the recipient mice were shown to have a high level of human liver reconstitution in situ, which survived for a more prolonged period (>8 months) than could be attained in any other model; and to have a gene expression profile and 3-dimensional architecture characteristic of mature human liver. First, this platform will be used to develop novel transplantation methods that enable human liver stem cells, human induced pluripotent epithelial cells (hiPS), or human adipocyte-derived stem cells to reconstitute a human liver. If successful, this would enable a complete paradigm-shift for treatment of end-stage liver disease: 'liver transplantation' could be performed using autologous cells without immunosuppression. Secondly, by genotyping the donor human liver cells, a panel of mice with 'humanized livers' with specified alleles for phase I drug metabolizing will be produced. Then, the rate of formation of human-specific drug metabolites for at least 3 drugs, whose metabolism is dependent upon human CYP450 enzyme activity, will be analyzed. If successful, this innovative model system will enable pharmacogenetic analyses to be efficiently performed within an entirely human context in vivo with all confounding environmental variables controlled, which would overcome a significant roadblock for characterizing inter-individual variation in drug metabolism. PUBLIC HEALTH RELEVANCE: This project will produce chimeric mice with human livers in situ from progenitor cells. If successful, this revolutionary experimental platform will enable: 'liver transplantation' to be performed using autologous cells without immunosuppression; and will provide a revolutionary platform for human pharmacogenetic analysis, which will overcome a significant roadblock for understanding inter-individual variation in drug metabolism.