REG3γ-deficient mice have altered mucus distribution and increased mucosal inflammatory responses to the microbiota and enteric pathogens in the ileum

Objective: Reg3g has been proposed to have a protective role against infection due to its bactericidal effect on Gram-positive bacteria, but evidence from in vivo studies is lacking. Therefore we generated a Reg3g-/- mouse, to determine its role in intestinal homeostasis and protection against experimental infection. Methods: Reg3g-/- mice were phenotyped using histological methods and a range of innate and immune markers. To investigate the antimicrobial role of Reg3g we experimentally infected mice with Gram-positive Listeria monocytogenes and Gram-negative Salmonella entertitidis and measured translocated bacteria, mucosal and systemic markers of infection. Results: Reg3g-/- mice display altered ileal mucus distribution and increased bacterial contact with the epithelium. , concomitant with This increased the inflammatory status in of the ileal mucosa and increased expression of Il-22, myeloperoxidase (MPO) and serum chemokines in serum. In response to infection, Reg3g-/- mice showed transcriptome changes and elevated levels of mucosal MPO in the ileum, but no increased bacterial translocation to the organs. Conclusions: Reg3g is equally distributed throughout the mucus of wild type (wt) mice and its absence results in an altered distribution of the ileal mucus. Reg3g deficiency also results resulted in increased bacterial contact with the epithelium and heightened inflammatory responses in the ileal mucosa. We propose that Reg3g binds pathogens suggesting it and contributes to mucus barrier function by ensnaring bacteria. Compared to wt mice, Reg3g-/- mice infected with S. enteritidis and L. monocytogenes show an increase of mucosal inflammatory markers indicating the protective, anti-microbial roles of Reg3g in defence against both Gram-positive and -negative bacteria. This study was set up according to a one-treatment, one-control design; treatments were inoculation with either Listeria monocytogenes or Salmonella enteritidis bacterial pathogens. The study results contain transcriptional profiles from infected and sham-infected control C57Bl/6 mice. In total, this study includes data from 2 treatments and 1 control of (pooled) wild-type C57Bl/6 mice and Reg3g-/- KO mutant C57Bl/6 mice = 6 arrays.

【研究目的】鉴于Reg3g对革兰氏阳性菌具有杀菌活性，被认为在抗感染过程中发挥保护作用，但目前尚缺乏体内研究证据。为此，本研究构建了Reg3g基因敲除（Reg3g-/-）小鼠模型，以明确其在肠道稳态及实验性感染防御中的作用。
【研究方法】本研究通过组织学方法及一系列先天免疫与免疫相关标志物，对Reg3g-/-小鼠进行表型分析。为探究Reg3g的抗菌功能，我们分别以革兰氏阳性菌单核细胞增生李斯特菌（Listeria monocytogenes）与革兰氏阴性菌肠炎沙门氏菌（Salmonella enteritidis）构建小鼠感染模型，检测移位细菌数量、黏膜及全身感染标志物水平。
【研究结果】Reg3g-/-小鼠回肠黏液分布出现异常，细菌与上皮细胞的接触增多；同时伴随回肠黏膜炎症状态加剧，血清中IL-22、髓过氧化物酶（myeloperoxidase, MPO）及血清趋化因子的表达水平升高。感染状态下，Reg3g-/-小鼠的转录组发生显著改变，回肠黏膜MPO水平升高，但未观察到细菌向外周器官的移位增加。
【研究结论】Reg3g在野生型（wild type, wt）小鼠的全层黏液中均匀分布，其缺失会导致回肠黏液分布异常。Reg3g缺乏还会增加细菌与上皮细胞的接触，并加剧回肠黏膜的炎症反应。我们推测Reg3g可通过捕获病原体发挥作用，其有助于维持黏液屏障功能。与野生型小鼠相比，感染肠炎沙门氏菌与单核细胞增生李斯特菌的Reg3g-/-小鼠黏膜炎症标志物水平升高，提示Reg3g对革兰氏阳性菌与革兰氏阴性菌均具有抗感染保护作用。本研究采用单处理单对照设计，处理组分别为单核细胞增生李斯特菌或肠炎沙门氏菌病原菌接种组。研究结果包含感染组与假感染对照C57BL/6小鼠的转录组谱。本研究总计纳入6张芯片数据，对应2种处理组与1种对照组的野生型C57BL/6小鼠及Reg3g基因敲除（Reg3g-/-）突变型C57BL/6小鼠的混合样本。