Bovine tracheal organoids for studying Mycoplasma bovis respiratory infections

In vitro three-dimensional organoid models simulate key aspects of the structure and function of in vivo organs and have been used to study physiology, host-pathogen interactions, pathogenesis and pharmacodynamics. Although most organoid studies have been developed using human or mouse tissues, recent advancements have enabled the establishment of intestinal and respiratory tract organoids from domestic animal samples. Mycoplasma bovis causes chronic respiratory tract infections in cattle with significant health and economic consequences. The pathogenesis and virulence factors of M. bovis have been studied in several in vitro infection models, but the use of organoids has not been examined previously. In this study, we assessed the feasibility of using a matrix-embedded bovine tracheal organoid system to study respiratory infections with M. bovis. Bovine tracheal organoids were inoculated with M. bovis strain MbovMil and incubated for 72 hours to investigate the ability of M. bovis to proliferate, attach and invade the organoids. M. bovis was able to infect the organoids, resulting in a mean 260-fold increase in the titre of viable M. bovis by 72 hours post-inoculation. Examination of the infected organoids using transmission electron microscopy revealed the presence of mycoplasmas within the organoid cells and membrane bound clusters of M. bovis inside the intercellular junctions. Our findings indicate that bovine tracheal organoids can be used as a model system for studying respiratory tract infections caused by M. bovis.