Mouse Models of Sepsis

Abstract

Human sepsis is a complex disease that manifests with a diverse range of phenotypes and inherent variability among individuals, making it hard to develop a comprehensive animal model. Despite this difficulty, numerous models have been developed that capture many key aspects of human sepsis. The robustness of these models is vital for conducting pre-clinical studies to test and develop potential therapeutics. In this article, we describe four different models of murine sepsis that can be used to address different scientific questions relevant to the pathology and immune response during and after a septic event. Basic Protocol 1 details a non-synchronous cecal ligation and puncture (CLP) model of sepsis, where mice are subjected to polymicrobial exposure through surgery at different time points within 2 weeks. This variation in sepsis onset establishes each mouse at a different state of inflammation and cytokine levels that mimics the variability observed in humans when they present in the clinic. This model is ideal for studying the long-term impact of sepsis on the host. Basic Protocol 2 is also a type of polymicrobial sepsis, where injection of a specific amount of cecal slurry from a donor mouse into the peritoneum of recipient mice establishes immediate inflammation and sepsis without any need for surgery. Basic Protocol 3 describes infecting mice with a defined gram-positive or -negative bacterial strain to model a subset of sepsis observed in humans infected with a single pathogen. Basic Protocol 4 describes administering LPS to induce sterile endotoxemia. This form of sepsis is observed in humans exposed to bacterial toxins from the environment. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Non-synchronous cecal ligation and puncture Basic Protocol 2: Cecal slurry model of murine sepsis Basic Protocol 3: Monomicrobial model of murine sepsis Basic Protocol 4: LPS model of murine sepsis.

Keywords: CLP; cecal slurry sepsis; microbial sepsis; mouse models; sepsis.

Figure 1.

Summary of studies published using mouse models of sepsis over time. PubMed was conducted on Aug 9 2023, to search for different mouse models of sepsis, where the “search terms” used are mentioned as the graph title. The indexing Information was downloaded from the “Results by year” filter to generate the graphs. A. Summary of publications focusing on “Mouse models of sepsis” are listed by year in the bar graphs, with the pie chart showing the number of publications of each model that make up the total publication count. B, C, D, E, F. Summary of publications listed by year, focusing on “Mouse cecal ligation and puncture”, “LPS sepsis in mouse”, “E. coli sepsis in mouse”, “P. aeruginosa sepsis in mouse”, and “Cecal slurry sepsis in mouse” respectively. All the bar graphs show the fold change in the number of publications between 2013–2023. Bars indicating the datapoints for 2013 and 2023 are filled in Black for ease of identification.

Figure 2.

Using non-synchronous CLP in mouse to achieve the heterogeneity of immune system states of human sepsis patients. A. Serum collected from septic patients shortly after admission into the hospital(n=14), and serum from human healthy control (HC, n=12) are used to assay for IL-6, IL-1β, and IL-10 cytokine levels. B. Mice are subjected to sham surgery(n=20) at −7D, or CLP surgery at −7D, −3D, −1D, or −6hrs. Serum was collected from all the mice(n=67) at 3,6,12,24,48, and 72 hours post CLP. The serum from all the time points is pooled to show the levels of IL-6, IL-1β, and IL-10. C. Kinetics of the serum cytokines (IL-6, IL-1β, and IL-10) at different times post CLP. D. A model describing the non-synchronous CLP sepsis in mice. Unpaired t-test was performed between groups in 2A, 2B, where * p< 0.05, ** p<0.01, and error bar represents SEM. LOD- Limit of detection.

Figure 3.

Cecal slurry (CS) model readout of sepsis. Female mice were injected with 1.3mg/g, 0.975mg/g, 0.65mg/g or vehicle of cecal slurry prepared from 12-week-old female donor mice. Administration of antibiotics and saline fluids were given at 10hrs. A. Rectal temperatures were recorded at baseline (0hr), 4hr, 10hr, 22hr, and 46hrs. B. White blood cell counts from ACK lysed peripheral blood were counted via hemacytometer. Comparisons were made between vehicle treated (n=6) and 1.3mg/g CS treated (n=6). C. Serum from vehicle or 1.3 mg/g CS treated mice at the baseline (0hr) and 10hr were analyzed for cytokine contents. Ordinary One-way ANOVA was used in 3B, where ** p< 0.01; and error bar represents SEM. LOD- Limit of detection.

Figure 4.

A. Sepsis readouts using uropathogenic E. coli (UPEC) monomicrobial model. A. Serum levels of IL-1β, IL-6, TNFα, and IL-10/CXCL10 were measured at 0hr (baseline), 3hr, 24hr. Data were combined from two experiments using a total of n=6 mice, where each symbol represents a mouse and bars indicate means with SEM. B. Number of CD4 T cells, CD8 T cells, B cells, and NK cells in the blood of mice prior to infection (baseline), 3hrs, and 24hrs after systemic UPEC infection. Unpaired t-test was performed between groups in 2B, where ** p<0.01, *** p< 0.001; and error bar represents SEM. LOD- Limit of detection.