Aerobic-anaerobic interface in a colon chip to study host microbe interaction
Not many systems can mimic the Aerobic-Anaerobic interface of the large intestine. A not-so-old paper from the Wyss institute creates a hypoxic gradient across their intestine-on-a-chip. In this study, the chip comprised epithelial cells on top of a porous membrane and bacteria cultured above the epithelium under a hypoxia gradient created by flowing oxygenated medium through the basal channel while maintaining the entire chip in an anaerobic chamber.
Results
In the intestine-microbiome-on-a-chip model, infection with the bacterium, Salmonella typhimurium (S. typhimurium), brought about epithelial detachment, decreased tight junction staining, and increased release of chemokines that mimicked changes already seen in mice. On the other hand, Enterococcus faecium (E. faecium) prevented epithelial cell detachment and promoted host tolerance to infection. However, E. faecium also caused small regions of epithelial detachment.
DigesTable of the paper Gazzaniga, F.S., et al., Harnessing colon chip technology to identify commensal bacteria that promote host tolerance to infection. Frontiers in Cellular and Infection Microbiology, 2021. 11: p. 638014. This paper is reproduced under https://creativecommons.org/licenses/by/4.0/. The image of the chip was edited for better clarity, data in the table and text were compiled and interpreted by AZAR Innovations.
Method
Barrier-model intestine chips were made from PDMS and lined by epithelial cells isolated from duodenum, ileum, jejunum, or colon. E. faecium was isolated from human microbiome and resuspended in antibiotic free bacterial mouse organoid media.
Fabrication: commercially available, Emulate, Inc
Sterilization: ready to use
Cell incorporation: organoids were seeded onto the top channel
Perfusion/refreshing: peristaltic pumps
Treatment:
On-chip read-outs: real-time microscopy, end-point microscopy
Off-chip read-outs: RT-qPCR, ELISA
Strong points
+ A typical two-compartment Wyss/Emulate barrier chip with a monolayer of intestinal cells (focus on colon, demo of different parts of small intestine)
+ Double perfusion Aerobic-Anaerobic interface
+ Data in the graphs show good yield from the experiments (>75%)
Nothing is perfect! The system can also improve:
– The system seems to be quite complex to work with, and anaerobic farms, demonstrated by their previous paper, definitely limits the throughput.
– Although characterized in their previous work, they do not measure the oxygen concentration in the luminal channel, and do not indicate how they sample aerobically from the outlet of the chip.
Conclusion and outlook
The colon-on-a-chip of this study supported co-culture of gut microbiome with differentiated intestinal epithelium. This model can be utilized to investigate specific host-microbe interactions under controlled conditions in vitro.
