Spondyloarthritis (SpA) encompasses several inflammatory rheumatic diseases that frequently harbor overt or subclinical intestinal inflammation. Dysbiosis, characterized by an overabundance of the Ruminococcus gnavus species, has recently been demonstrated in the intestinal microbiota of patients affected by SpA and correlates positively with disease activity. A thorough understanding of the microbiota-host interaction mechanisms in SpA is lacking due to the intrinsic limitations of standard cellular models. Organ-on-Chip systems have been recently developed thanks to the integration of nanotechnologies and microfluidics. The application of a laminar flux in two separate channels adjacent to a cell culture patch would allow the prolonged interaction between bacteria (including anaerobes) and patient-derived intestinal epithelium, closely mimicking interactions that occur in vivo.
One of the primary steps for developing a Gut-on-Chip microphysiological platform is obtaining a reliable source of patient-derived epithelial cells. During the last year, we validated a robust protocol to derive organoids from adult stem cells of SpA patients' standard colonic biopsies. The proliferative potential of these organoids allows the expansion and biobanking needed for the extensive characterization of each epithelial line. Epithelial differentiation appears to be a critical step to increase the physiological relevance. Thus, an IGF1+ FGF2+ medium was optimized in-house to obtain reproducible expression of differentiated epithelial subtypes. Several strategies to model relevant host-microbes interaction, including an "apical out" organoids model, a Transwell-type culture system, and ultimately a microfluidic Gut-on-Chip platform, began to be optimized to lay the groundwork for their reproducible use. Preliminary data based on stimulation of epithelial monolayer with SpA-derived strains of Ruminococcus gnavus suggest a pro-inflammatory effect of the bacteria.
Intestinal inflammation and microbiota are implicated in Spondyloarthritis. Their detailed characterization could significantly improve Spondyloarthritis treatment, but it is challenging.
This project involved significant steps to develop innovative experimental models for studying the connection between intestinal inflammation, microbiota, and Spondyloarthritis.
Organoids are tiny, 3D structures grown from cells that act like a miniature, simplified version of an organ. Firstly, we developed intestinal organoids using biopsies taken from Spondyloarthritis patients and healthy controls during colonoscopies.
Throughout this project, organoids were successfully used to simulate a state of intestinal inflammation, providing a foundation for a better understanding of what happens in the gut of Spondyloarthritis patients and potentially for testing treatments.
Furthermore, exploiting the proliferative nature of these mini-organs, we obtained a large number of patient-derived cells. These cells have been used to prepare a system complementary to organoids called Gut-on-Chip. This system simulates intestinal physiology by applying flows to cells. Due to its complexity, it will require further optimization before it can be effectively utilized.
At the current stage, it has been possible to begin studying one of the most critical gut microbiota bacteria in Spondyloarthritis, called Ruminococcus gnavus, to measure its effect on epithelial cells derived from patients.
Our work paves the way for a better understanding of the connection between intestinal inflammation, microbiota, and Spondyloarthritis and could foreseeably be used for personalized medicine applications and drug testing to improve the treatment of patients affected by Spondyloarthritis.