Hydrogel properties on intestinal surfaces in health and disease

The human intestine forms a highly dynamic barrier consisting of a constantly renewing epithelial cell monolayer covered by a mucus layer. This hydrogel barrier dynamically contributes to tissue homeostasis and prevents pathogen invasion physically, as well as through antimicrobial peptides. Changes in mucus composition and viscoelastic properties are neglected parameters in the understanding of human intestinal disease. Distinct changes of the mucus have previously been described for patients suffering from inflammatory bowel disease. However, data for the terminal ileum, a critical intestinal area due to the increase in bacterial load, are scarce. Furthermore, the impact of biophysical and biochemical triggers contained in the mucus layer has not been studied yet, mostly due to a lack of model systems. The introduction of infinitively self-replicating human intestinal organoids generated from stem cells that comprise all major intestinal cell types allow for performing these analyses.

To biofabricate a small intestine tissue model, we developed and characterized an extracellular matrix (ECM)-based resin and optimized it for 3D printing small intestinal submucosa-derived hydrogel scaffolds. Human small intestinal organoid-derived adult stem cells grew as 2D monolayers on Matrigel^TM-coated filter membranes and the printed scaffolds. In intestinal cell lines and stem cells, culture under dynamic conditions resulted in faster functional differentiation of the cells and higher mucus production than in static conditions. RNAseq is currently applied to perform a more in-depth characterization of static and dynamic conditions and the impact of the scaffold. In parallel to the model studies, we established in collaboration with Z02|Duerr/Siegmund/Weinhart a mucus and organoid biobank and provided a human mucin expression atlas for health and Crohn’s disease (CD). In collaboration with A01|Mall/Gradzielski, we acquired the first rheology data for small intestinal mucus and observed specific changes in CD, where the elastic and viscous modulus was increased and the calculated mesh size was smaller than in mucus from healthy persons. Furthermore, the mucus microbiota composition was compared to intestinal biopsies and fecal samples and showed a distinct enrichment (B05|Fulde/Forslund/Schaupp). Disease-specific changes are currently analyzed. Last, the proteome in health and CD was evaluated with Z01|Mertins/Ludwig/Pigaleva.