Organoids are three-dimensional tissue structures, generated from tissue resident or pluripotent stem cells, which self-organize and recapitulate complex aspects of their organ counterparts. They represent a substantial advance in structural and functional complexity over traditional in vitro cell culture models that are often non-physiological and transformed. Over the last 9 years we have successfully worked on organoids and have established organoid cultures of various murine tissues such as liver, gallbladder, pancreas, stomach and intestine and also develop a variety of technologies such as genome editing, transfection, freezing, microinjection, co-culturing and a broad spectrum of functional assays. We use organoids to study the molecular and cellular features of various diseases, to develop new drugs and for clinical applications in regenerative therapy and personalized medicine.
Interferons (IFNs) on the one hand are potent immune-modulatory cytokines that are strongly expressed by intestinal epithelial cells (IECs) and mucosal immune cells in response to viral and bacterial infections. On the other hand IFNs promote intestinal inflammation by triggering epithelial cell death and influencing tight junction biology. Accordingly, we discovered a correlation between IFN expression (particularly IFN-λ) and disease activity in human Crohn’s disease patients. In addition, we have identified a previously undescribed type of regulated necrosis that is strongly dependent on IFN signaling and that was executed by a mixed lineage kinase domain-like protein (MLKL)-dependent pathway but independent of RIPK3 and Caspase-8. Since IFN-λ-dependent non-apoptotic epithelial cell death is associated with strong MLKL up-regulation, our hypothesis is that IFN-λ induces MLKL-dependent programmed necrosis in the gut and that this pathway drives intestinal inflammation in mice and in human IBD patients. We address the question if and by which pathways interferon-regulated necrosis of epithelial cells contributes to intestinal inflammation and how these mechanisms could be targeted for future therapeutic intervention.
Intestinal epithelial cells form a physical barrier to separate the commensal and pathogenic microorganisms from the underlying immune system. Specialized intestinal epithelial cells (e.g. Paneth cells, Goblet cells) secreting mucus and antimicrobial peptides, which hamper access and survival of bacteria. Given these fundamental and diverse functions of intestinal epithelial cells, it is obvious that proliferation, differentiation and cell death of these cells need to be tightly controlled in order to maintain intestinal homeostasis. Our studies already identified a critical role of necroptosis in the regulation of intestinal homeostasis and intestinal barrier which strongly contributes to intestinal inflammation. But little is known about the impact of the intestinal microbiota on this particular form of cell death and the effect of epithelial necroptosis on the gut microbiota. The aim of the proposed project is to define the bi-directional cross-talk between the intestinal microbiota and the host cell death machinery under physiological and pathophysiological conditions. A better understanding of the host-microbial interaction in the context of establishing and maintaining intestinal barrier function is essential for the development of novel strategies for the management of intestinal inflammatory disorders and of gastrointestinal infections.
Intestinal inflammation and dysbiosis have been linked to autoimmune diseases such as rheumatoid arthritis (RA); however, the underlying mechanisms remain not fully understood. Our own published and preliminary data suggest that expression of caspase-8 and hypoxia-inducing factors (HIF) have a crucial influence on mucosal immunity and the composition of the intestinal microbiota. Further, our preliminary data suggest that both factors might additionally control systemic Th17-driven (auto-) immunity and the onset of arthritis. With a multidisciplinary approach we want to characterize the link between intestinal epithelial cell (IEC) death and the initiation as well as progression of joint inflammation. In particular, we aim to dissect host-microbial interaction and determine the influence of this interaction (epithelium-microbiota) on systemic immunity and the onset of autoimmune arthritis.
Hepatocellular death plays a fundamental role in almost all hepatic diseases and thus, detailed knowledge about molecular mechanisms that mediate cell death responses in the liver is essential to advance therapeutic strategies. In this project, we aim to analyze the role of the mixed lineage kinase domain-like protein (MLKL)-mediated necrosis in liver diseases. We now found that MLKL is upregulated in hepatitis C patients. In order to investigate the contribution of MLKL to viral induced hepatitis, we established a new mouse model which is characterized by acute, cell death mediated liver dysfunction. Accordingly, we identified that transgenic expression of the viral cell death regulator vFLIP (Caspase-8 inhibitor) causes severe liver injury through MLKL-mediated necrosis finally culminating in an early death of mice.