Host-microbe interaction in the upper respiratory tract : development of a polymicrobial model of the sinonasal microenvironment

Mechanistic research to unravel the aetiology and pathology of chronic rhinosinusitis and to find innovative treatment methods requires models of the affected tissues and their resident microbiota. A co-culture model of the upper respiratory tract with a representative epithelial structure, immune cells and representative microbial communities from healthy individuals was established. Preliminary testing led to the development of a static co-culture model of differentiated airway epithelial cells at air-liquid interface and a natural microbial community. Host cell cytotoxicity, assessed by lactate dehydrogenase release, tight junction functionality, measured as transepithelial electrical resistance, and IL-10 and IL-8 release, measured using ELISA, did not differ significantly between sterile controls and bacteria-inoculated cell layers during 3 days of co-culture. Microbial community profiling, using Illumina MiSeq NGS and phenotypic fingerprinting using flow cytometry 1, indicated that a representative sinonasal microbial community, retaining richness and diversity comparable to that of the original sample, was maintained during co-culture. In a further stage, non-activated THP-1 derived macrophages were included in the co-culture model. Applying the same methodology, it was shown that cytotoxicity remained below 10 % and epithelial resistance was maintained. Analysis of the microbial community proved that bacterial growth and representative community composition were preserved in the triple co-culture model. This polymicrobial, immunocompetent model enables steering of the inflammatory state to investigate host-microbe interactions in healthy and inflammatory upper respiratory tract conditions. The use of individual-derived samples can help to personalize the in vitro model and better predict the response to therapeutics, considering the microbiome as key factor in modulating the inflammatory response at sinonasal level.