宿主因子影响生发细胞自我更新及泡球蚴生长发育的分子机制

The germinative cells, similar to the neoblasts of free living flatworms，is the only source of cell proliferation throughout the life cycle of Echinococcus multilocularis, and only the germinative cells proliferate in the larval vesicles and in primary cell cultures that undergo complete vesicle regeneration.Recent evidence suggests that parasites can exploit the hormonal microenvironment within the host to favor their establishment, growth and reproduction and the self-renewal of neoblast. A series of evolutionarily conserved signaling molecules of the insulin, EGF and TGF-beta pathways that are able to functionally interact with corresponding host fators have been described in Echinococcus multilocularis (Em) and most likely play a crucial role in self-renewal of the germinative cells and parasite development. Our previous in vitro studies found that host EGF can induce phosphorylation of Em ERK and promote self-renewal of the germinative cells and larval development through a unknown mechanism. In this study, we will use the established in vitro system of Em to confirm the effect of host insulin, EGF and TGF-beta on the in self-renewal of the germinative cells and larval development of Em. The role of important downstream signaling components of insulin, EGF and TGF-beta signal pathways in in self-renewal of the germinative cells and the development and differentiation of Em and the underlying mechanism will be identified and characterized. Furthermore, we will analyze the feasibility and validity of protein kinases inhibitors as the promising drug candidates for treatment of AE. We also wish the study will deep our understanding in the mechanism of host-parasite interaction.

近期研究表明泡球蚴中存在与成体全能干细胞(neoblast)类似的干细胞（生发细胞），并证明这些生发细胞是泡球蚴生长发育的关键因素。大量研究表明寄生虫可利用宿主因子调控自身的生长发育，泡球蚴细胞中不但存在可与EGF、TGF-β及胰岛素等宿主因子相互作用的受体，而且还存在相关信号通路中关键分子的同源物。我们前期工作也发现，宿主EGF等因子可上调泡球蚴细胞ERK磷酸化水平，并促进生发细胞的自我更新和泡球蚴生长。本项目将以体外泡球蚴培养系统作为实验模型，研究宿主因子对生发细胞自我更新和泡球蚴生长发育的影响；分析探讨宿主因子相关信号通路关键分子在生发细胞的自我更新和泡球蚴生长发育过程中的作用及其机制，同时为进一步研究复杂的寄生虫-宿主相互作用提供新的视野和思路。我们还将在此基础上研究上述信号通路中关键蛋白激酶抑制剂作为治疗泡球蚴病候选药物的可行性及有效性，为治疗泡球蚴新药物靶点的发现提供帮助。

多房棘球绦虫幼虫泡球蚴寄生于人体可引起危害严重的致死性寄生虫病——泡球蚴病。泡球蚴在人体内类似肿瘤样生长发育、侵润和转移，均依赖其体内一类具有无限增殖能力和分化潜能的成体干细胞——生发细胞。但是目前对泡球蚴生发细胞的功能调控机制知之甚少。.本项目中我们的研究发现，宿主生长因子EGF和TGF-β可促进体外培养的泡球蚴生长发育。进一步研究发现，泡球蚴内存在的EGF受体分子可以感受宿主EGF信号而被激活，进而激活下游MEK/ERK信号途径，促进泡球蚴生发细胞增殖/自我更新，影响泡球蚴生长发育。同时我们发现，PI3K/AKT并未在EGF介导的生发细胞增殖过程中发挥重要作用。另外，宿主EGF介导的EGFR/ERK途径可影响泡球蚴EmSOX2的表达，而后者可能进一步参与调控生发细胞的增殖和维持。利用小分子药物CI-1033、BIBW2992和U0126阻抑EGFR/ERK途径可显著抑制生发细胞增殖以及泡球蚴的生长发育。这些药物可引起泡球蚴超微结构的显著变化。BIBW2992和CI-1033还可诱导泡球蚴生发细胞发生凋亡，但是U0126并未显著诱导细胞凋亡，提示其他信号途径参与了这一过程。最后，我们的研究结果还表明，BIBW2992和U0126在小鼠感染模型中表型出较好的抑虫效果。.本项目从泡球蚴生长发育过程中微环境里的宿主生长因子的角度入手，重点分析了宿主EGFR介导的泡球蚴EGFR/ERK信号通路在生发细胞增殖/自我更新中的作用机制，有助于阐明泡球蚴在宿主体内生长发育的机理。同时我们发现小分子药物阻断EGFR/ERK信号通路，可引起生发细胞增殖受阻，体外培养和小鼠体内的泡球蚴生长发育均受到抑制，提示相关信号分子或可成为极具潜力的药物靶点。这些结果为复杂的寄生虫-宿主相互作用研究提供新的视野和思路，同时也为今后新型泡球蚴病的药物研发提供理论基础。