Data_Sheet_1_A Model System for Feralizing Laboratory Mice in Large Farmyard-Like Pens.zip

Laboratory mice are typically housed under extremely clean laboratory conditions, far removed from the natural lifestyle of a free-living mouse. There is a risk that this isolation from real-life conditions may lead to poor translatability and misinterpretation of results. We and others have shown that feral mice as well as laboratory mice exposed to naturalistic environments harbor a more diverse gut microbiota and display an activated immunological phenotype compared to hygienic laboratory mice. We here describe a naturalistic indoors housing system for mice, representing a farmyard-type habitat typical for house mice. Large open pens were installed with soil and domestic animal feces, creating a highly diverse microbial environment and providing space and complexity allowing for natural behavior. Laboratory C57BL/6 mice were co-housed in this system together with wild-caught feral mice, included as a source of murine microbionts. We found that mice feralized in this manner displayed a gut microbiota structure similar to their feral cohabitants, such as higher relative content of Firmicutes and enrichment of Proteobacteria. Furthermore, the immunophenotype of feralized mice approached that of feral mice, with elevated levels of memory T-cells and late-stage NK cells compared to laboratory-housed control mice, indicating antigenic experience and immune training. The dietary elements presented in the mouse pens could only moderately explain changes in microbial colonization, and none of the immunological changes. In conclusion, this system enables various types of studies using genetically controlled mice on the background of adaptation to a high diversity microbial environment and a lifestyle natural for the species.

实验室小鼠通常饲养于极度洁净的实验环境中，与自由生活的野生小鼠的自然生存模式相去甚远。这种脱离真实生存环境的饲养方式，可能导致研究结果的可外推性不佳，甚至出现结果解读偏差。此前我们与其他团队的研究均已证实，相较于洁净环境饲养的实验室小鼠，野生小鼠以及暴露于自然化环境的实验室小鼠拥有更为多样的肠道菌群，并呈现激活的免疫表型。本研究描述了一种小鼠自然化室内饲养系统，其模拟了家鼠典型的农家院落型栖息环境。该系统设置大型开放式饲养栏，内置土壤与家畜粪便，以此构建高度多样化的微生物环境，并为小鼠提供了可展现自然行为的空间与环境复杂度。我们将实验室C57BL/6小鼠与野生捕获的野生小鼠共同饲养于该系统中，以野生小鼠作为小鼠微生物群的来源。研究发现，经此方式驯化的野生化小鼠，其肠道菌群结构与共饲养的野生小鼠相似——例如厚壁菌门（Firmicutes）相对丰度更高，变形菌门（Proteobacteria）富集。此外，野生化小鼠的免疫表型趋近于野生小鼠：与实验室饲养的对照组小鼠相比，其记忆T细胞与晚期自然杀伤（NK）细胞水平升高，这提示其经历了抗原暴露与免疫训练。小鼠饲养栏内提供的膳食元素仅能适度解释菌群定植的变化，却无法解释任何免疫表型的改变。综上，该系统可支持各类研究：在适应高多样性微生物环境以及该物种自然生活方式的背景下，使用遗传背景可控的小鼠开展实验。