Time Course of Gene Expression Profiling in the Liver of Experimental Mice Infected with Echinococcus multilocularis

BackgroundAlveolar echinococcosis (AE) is a severe chronic parasitic disease which behaves like a slow-growing liver cancer. Clinical observations suggest that the parasite, Echinococcus multilocularis (E. multilocularis) influences liver homeostasis and hepatic cell metabolism. However, this has never been analyzed during the time course of infection in the common model of secondary echinococcosis in experimental mice.Methodology/Principal FindingsGene expression profiles were assessed using DNA microarray analysis, 1, 2, 3 and 6 months after injection of E. multilocularis metacestode in the liver of susceptible mice. Data were collected at different time points to monitor the dynamic behavior of gene expression. 557 differentially expressed genes were identified at one or more time points, including 351 up-regulated and 228 down-regulated genes. Time-course analysis indicated, at the initial stage of E. multilocularis infection (month 1–2), that most of up-regulated pathways were related to immune processes and cell trafficking such as chemokine-, mitogen-activated protein kinase (MAPK) signaling, and down-regulated pathways were related to xenobiotic metabolism; at the middle stage (month 3), MAPK signaling pathway was maintained and peroxisome proliferator-activated receptor (PPAR) signaling pathway emerged; at the late stage (month 6), most of up-regulated pathways were related to PPAR signaling pathway, complement and coagulation cascades, while down-regulated pathways were related to metabolism of xenobiotics by cytochrome P450. Quantitative RT-PCR analysis of a random selection of 19 genes confirmed the reliability of the microarray data. Immunohistochemistry analysis showed that proliferating cell nuclear antigen (PCNA) was increased in the liver of E. multilocularis infected mice from 2 months to 6 months.ConclusionsE. multilocularis metacestode definitely exerts a deep influence on liver homeostasis, by modifying a number of gene expression and metabolic pathways. It especially promotes hepatic cell proliferation, as evidenced by the increased PCNA constantly found in all the experimental time-points we studied and by an increased gene expression of key metabolic pathways.背景 泡型棘球蚴病（Alveolar echinococcosis, AE）是一类致死性慢性寄生虫病，其临床表型类似生长缓慢的肝癌。临床观察表明，多房棘球绦虫（Echinococcus multilocularis, E. multilocularis）可影响肝脏稳态与肝细胞代谢，但此前尚未有研究在实验小鼠继发性棘球蚴病这一常用模型中，针对感染进程中的该效应展开系统分析。 方法与主要结果 本研究在易感小鼠肝脏内注射多房棘球蚴后，分别于1、2、3、6个月采用DNA微阵列（DNA microarray）分析检测基因表达谱，通过多时间点采样监测基因表达的动态变化。最终在至少一个时间点中共鉴定出557个差异表达基因，其中351个基因上调、228个基因下调。时序分析结果显示：在多房棘球绦虫感染初期（1~2个月），上调富集通路多与免疫过程及细胞转运相关，包括趋化因子通路、丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）信号通路；而下调通路则与外源性物质代谢有关。感染中期（3个月），MAPK信号通路持续激活，过氧化物酶体增殖物激活受体（peroxisome proliferator-activated receptor, PPAR）信号通路出现显著富集。感染晚期（6个月），上调富集通路主要为PPAR信号通路、补体与凝血级联反应，而下调通路则与细胞色素P450介导的外源性物质代谢相关。本研究随机选取19个基因进行定量实时聚合酶链反应（quantitative RT-PCR, qRT-PCR）验证，结果证实了微阵列数据的可靠性。免疫组织化学分析显示，感染小鼠肝脏中的增殖细胞核抗原（proliferating cell nuclear antigen, PCNA）表达水平在感染后2~6个月均显著升高。 结论 多房棘球蚴确实通过改变大量基因表达与代谢通路，对肝脏稳态造成显著影响。本研究中各实验时间点持续升高的PCNA表达，以及关键代谢通路的基因表达上调均证实，该寄生虫可促进肝细胞增殖。