Open Research Projects, Research

Unraveling the role of a macrophage-B cell loop in the immune microenvironment in chronic liver disease using spatial proteomics and intravital imaging

Prinicipal Investigator

Dr. Moritz Peiseler
Dr. Felix Heymann

Scientific interest within the context of the graduate college

Chronic liver disease is among the most prevalent causes of organ failure and death worldwide, yet the molecular and cellular mechanisms that drive its progression remain incompletely understood and are driven by different etiologies. Metabolic dysfunction-associated steatotic liver disease (MASLD) and alcoholic liver disease (ALD) account for the majority of cases with liver cirrhosis in Germany. Our group investigates how the hepatic immune microenvironment is reshaped during chronic inflammation, with a particular focus on the spatial organization of innate immune cells. Kupffer cells and monocyte-derived macrophages occupy defined tissue niches within the liver, and their function is strongly influenced by the local molecular environment. Similarly, B cells accumulate in diseased liver tissue and produce immunoglobulin, however this relationship in the pathogenesis of chronic liver disease remains unexplored. This project sits at the heart of the Re-Thinking Health mission: by mapping the spatial protein landscape of the inflamed and fibrotic liver and linking it to the real-time behavior of immune cells, we aim to define the molecular hallmarks that distinguish healthy from diseased hepatic tissue neighborhoods. The findings will provide a foundation for understanding how immune dysregulation is spatially organized – and how it might be interrupted to preserve or restore liver health.

Project description

Liver cirrhosis is the shared endpoint of most chronic liver diseases and is characterized by progressive fibrosis, sustained immune infiltration, and a fundamental remodeling of the hepatic tissue architecture. Despite its clinical importance, the spatial protein landscape of the fibrotic liver and the molecular neighborhoods occupied by innate immune cells has not been systematically characterized. Our group has generated preliminary data using laser-microdissection followed by protein mass spectrometry, revealing striking enrichment of immunoglobulin subunits and complement proteins (including C1q, C3, and C3b) in fibrotic and inflammatory lesion areas. These findings suggest that B cell-derived antibodies and the downstream complement cascade are spatially concentrated in regions of active liver damage, where they likely amplify macrophage activation and perpetuate tissue injury. This project will characterize these processes from two complementary angles: first, by generating a spatially resolved protein atlas of the fibrotic liver using MALDI imaging mass spectrometry; and second, by observing the behavior of macrophages and B cells in the liver by intravital multiphoton microscopy, with particular attention to complement-dependent interactions.

Aim 1: Spatial proteomics atlas of the complement-immune landscape in liver cirrhosis. We will begin by analyzing an existing dataset of spatially resolved protein mass spectrometry data generated from murine liver tissue across key disease stages: healthy controls, chronic inflammation with fibrosis, and disease regression. This analysis will identify proteins and protein networks enriched in specific tissue compartments – including periportal infiltrates, fibrotic septa, and sinusoidal regions – with a particular focus on immunoglobulins, complement components (C1q, C3, C3b, C5), and complement receptors expressed on macrophages (CD11b, CD16, CRIg). Building on these findings, we will perform MALDI imaging mass spectrometry on tissue sections from patients with liver cirrhosis and from mice after chronic CCl4-induced liver injury. MALDI imaging will provide high-resolution spatial maps of protein and lipid distributions across intact tissue sections without the need for prior region selection, allowing an unbiased comparison of molecular neighborhoods between species and disease stages. Together, the two approaches will generate a spatially resolved atlas linking immunoglobulin deposition and complement activation to defined inflammatory microenvironments in the diseased liver..

Aim 2: Intravital imaging of B cell and macrophage dynamics in the context of complement activation. The spatial protein maps generated in Aim 1 will be complemented by real-time imaging of immune cell behavior in the living liver. Using multiphoton intravital microscopy in fluorescent reporter mice together with antibody labeling, we will characterize how macrophages and B cells localize within the tissue, interact with one another, and respond to the local complement-rich environment. Complement receptor-dependent macrophage activation will be assessed by measuring phagocytic uptake of C3b-opsonized fluorescent particles in vivo, allowing direct comparison between healthy and chronically injured livers. B cell–macrophage contact events will be quantified by measuring interaction frequency and duration. These experiments will be performed in healthy controls and at defined stages of CCl4-induced liver injury, including active inflammation and the regression phase. By anchoring the dynamic cellular observations to the spatial proteomic maps from Aim 1, the project will reveal an integrated map of how complement deposition organizes the macrophage–B cell inflammatory axis in different stages of chronic liver disease.

Application details

References

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