Functional role of the alveolar epithelial glycocalyx in pulmonary defense and inflammation

Epithelial
and endothelial cells carry a hydrogel-like surface layer, including a glycocalyx, putatively regulating the interaction with other cells and particles including pathogens. Whilst the importance of the endothelial glycocalyx in vascular homeostasis, endothelial barrier integrity and leukocyte transmigration is well established, only
recently the lung epithelial glycocalyx has been shown to be relevant in regulating lung barrier function. The precise architecture as well as the role of the epithelial glycocalyx in steady state and pathological conditions, such as lung infections, remains virtually undescribed. We hypothesize that the epithelial alveolar lining layer, and particularly its glycocalyx is of utmost relevance for pathogen defense. By means of beneficially contributing to lung barrier function on the one hand and detrimentally providing nutrients/metabolites and anchoring structures for pathogens on the other, the glycocalyx may thus provide novel targets for prophylactic and therapeutic strategies in order to reduce bacterial colonization and infection.
For the planned work program, we established novel methods, generated important data sets and started cooperations within this CRC consortium. Our complementary expertise will allow us to a) elucidate the role of fucosylated blood group glycans that are part of the glycocalyx and b) characterize the biological role of the
glycocalyx in defense against respiratory pathogens. We will prepare a series of fucosylated oligosaccharides that will be printed onto glycan microarrays to screen the interaction with respiratory pathogens, e.g. Streptococcus pneumoniae and relevant mutants. Glycans recognized by pathogens will be incorporated into peptide and polymer scaffolds to create neo-glycoconjugates and neoglycopolymers. Complementary, we will employ a wide array of different methods ranging from advanced molecular analyses in cultured primary cells and cell lines to studies in isolated mouse lung, human lung tissue and complex in vivo murine model of pneumonia experiments. As we are aiming at mechanistic insights into defense properties of the epithelial surface layer against respiratory bacterial pathogens, in-depth analysis of molecular regulation in cell culture models is necessary, while lung barrier function and alveolar interaction need to be analyzed in the context of the intact lung, given the need for anatomically correct alveolo-capillary interfaces with intact cellular interactions. We have extensive experience with cellular and isolated perfused lung models as well as a range of different in vivo models of pneumonia in mice, which will be used to understand the potential impact of the epithelial hydrogels in infection and inflammation. To pave the way for translational endeavors, we will provide our collaboration partners with murine experimental models of high clinical relevance. Our preclinical murine pneumonia models range from infections with classical, as well as multidrug resistant bacteria. We are able to manipulate the clinical course of murine pneumonia to mimic a hospitalized setting, including antibiotic treatment and mechanical ventilation in murine intensive care unit settings.