A new experimental anaerobic microfluidic intestine-on-a-chip system has been developed that includes control of physiologically relevant oxygen gradients. This system enabled sustained co-culture of living human intestinal epithelium with a complex microbiota and led to improved intestinal barrier function compared with aerobic conditions.

Donald Ingber and colleagues have been developing organ chip technology for over 10 years. After noticing obstacles in the co-culture of microbial and human cells, they turned their expertise to developing a system that could recapitulate the dynamic host–microbiota interface.

The authors had previously described a two-channel microfluidic device lined with human intestinal cells that enabled stable co-culture of mucus-producing epithelium with human gut microbiota. However, culturing a fully typical human gut microbiota, including aerobic and anaerobic bacteria, required establishing the physiologically relevant oxygen gradients that are found in the large intestine.

“We leveraged our organ chip technology to recreate an oxygen gradient across a living human endothelial–epithelial interface that we reconstructed in vitro inside the chip,” explains Ingber. The previous device was modified to include microscale oxygen sensors and then the chips, lined by Caco2 cells or human organoid-derived epithelial cells, were housed in an anaerobic chamber. A complex microbiota community derived from human stool samples was then added. “This system enabled us to keep >200 different human commensal aerobic and anaerobic microorganisms alive in direct contact with patient-derived human intestinal epithelium for at least 5 days,” reports Ingber. “This has never been done before.”

In comparisons with aerobic chips, microbial diversity was found to be substantially improved with the anaerobic chips and the range of species abundances were in line with those reported by the Human Microbiome Project. The researchers also examined intestinal barrier function by quantifying permeability. “The integrity of the intestinal barrier was actually better under these more in vivo-like conditions with a hypoxia gradient,” says Ingber.

this tool could facilitate discovery and development of microbiome-related therapeutics

Through improved modelling of the human intestine, this tool could facilitate discovery and development of microbiome-related therapeutics. “We are now using this system to model the contributions of the microbiome to malnutrition and to develop therapeutics to ameliorate this disease,” concludes Ingber. “We also are integrating immune cells into the model.”