Long-Term In Vitro Culture Systems to Study Human Microbiome.

Microbial communities are eubiotic ecosystems that interact dynamically and synergistically with the human body. Imbalances in these interactions may cause dysbiosis by enhancing the occurrence of inflammatory conditions, such as periodontal or inflammatory bowel diseases. However, the mechanisms that lie behind eubiosis-dysbiosis transitions are still unclear and constantly being redefined. While the societal impact of these diseases is steadily increasing, the lack of a clear understanding behind the onset of the inflammatory conditions prevents the proper clinical strategies from being formulated. Although preclinical and clinical models and short-term planar in vitro cultures represent superb research tools, they are still lacking human relevance and long-term use. Bioreactors and organs-on-a-chip have attracted interest because of their ability to recreate and sustain the physical, structural, and mechanical features of the native environment, as well as to support long-term coculture of mammalian cells and the microbiome through modulation of pH and oxygen gradients. Existing devices, however, are still under development to sustain the microbiome-host coculture over long periods of time. In this scenario, to understand disease triggers and develop therapeutics, research efforts should command the development of three-dimensional constructs that would allow the investigation of processes underlying the microbial community assembly and how microorganisms influence host traits in both acute and chronic conditions.