Poster BB13 - Evaluating Immune Responses in Different Murine Liver Disease Models

Introduction: Liver disease affects a substantial portion of the population, with 4.5 million diagnosed cases in the U.S. alone, and an alarming estimate of 80-100 million adults living with undiagnosed conditions.1 Despite its prevalence, the intricate mechanisms underlying liver disease, whether acute or chronic, remain elusive. This knowledge gap hampers the development of successful clinical therapies, leaving patients and healthcare providers with few therapeutic options. Effective and targeted therapeutics hinge upon a comprehensive understanding of disease mechanisms, particularly the roles of inflammation and the immune system. These factors are recognized as pivotal players in liver disease, yet their dynamics and full impact remain inadequately understood. Murine models stand as powerful tools to bridge this gap, offering reproducible and controlled platforms to simulate disease states. In this context, our study develops and utilizes murine models that faithfully recapitulate acute and chronic liver disease states. By doing so, we have begun to dissect the intricate differences of inflammatory and immune factors across these models. Through this investigation, we aspire to shed light on the nuanced dynamics of immune responses in liver disease.

Materials and

Methods: Liver fibrosis, indicative of chronic liver disease, was induced in C57BL/6 mice via twice-weekly intraperitoneal injections of carbon tetrachloride (CCl4) at 0.5 mL/kg for six weeks. The extent of fibrosis was quantified using qPCR and histology. Flow cytometry was employed to compare immune cell populations in healthy and diseased liver tissues. Acute liver damage was induced in C57BL/6 mice by single injection of a toxic substance at responsible for high acute liver disease-related mortality. The dosage was comparable to that which would be acutely damaging to humans. Gene expression analysis (qPCR) evaluated inflammatory markers, while histological examination assessed hepatocyte damage.

Results, Conclusions, and Discussions: In murine models, the administration of serial CCL4 injections effectively instigated liver fibrosis, characterized by a notable upregulation in the expression of fibrotic gene markers (Fig. 1A). Induction of acute liver disease appeared to be effective as marked by the increase in expression of metabolic liver enzymes (Fig. 1B). Flow cytometry data (Fig. 2) comparing cell percentages in fibrotic and healthy livers revealed an increase in CD68-positive cells and a decrease in B cells, suggesting a significant role for macrophage recruitment in liver fibrosis. To discern acute and chronic immunological responses, expression of a representative fibrotic marker in both liver damage contexts was conducted (Fig. 3). A significant ~15-fold disparity in marker expression levels between acute and chronic liver damage states suggests distinct responses. Further investigation into the differential roles of macrophage subsets was undertaken through gene expression of CD68 and F4/80 markers (Fig. 4). Intriguingly, while CD68 expression increased in the chronic model, F4/80 expression remained relatively unchanged. Conversely, acute liver damage seems to augment F4/80 expression. This data suggests potential differences in macrophage. The data focuses on gene expression and flow cytometry, limiting the understanding of the functional implications of immune cells. Future studies incorporating functional assays and characterization of immune cell phenotypes will further elucidate the mechanistic immunology of liver disease. The present study establishes an induction model for acute and chronic liver damage. These models elucidate the intricate distinctions between immune responses in different liver diseases. Our findings show the significant involvement of immune cells, particularly macrophages, in the progression of liver disease. Further exploration is warranted to delineate the nuanced immunological responses in acute liver damage models. Understanding the differential immune dynamics between acute and chronic liver damage holds promise for identifying novel therapeutic targets tailored. By unraveling the complex immune mechanisms underlying liver fibrosis, we pave the way for the development of targeted therapies aimed at alleviating the burden of liver-related morbidity and mortality.

Acknowledgements (Optional):

References: [1]Sharma, A. & Nagalli, S. Chronic Liver Disease., 2024, StatPearls [2] Robinson, M. W., et al,. 2016, Cell Mol Immunol.