Abstract

Microengineering a Physiologic Colon Replica

Nancy Allbritton, Frank and Julie Jungers Dean of the College of Engineering and Professor of Bioengineering, University of Washington in Seattle

Organ-on-chips are miniaturized devices that arrange living cells to simulate functional subunits of tissues and organs. These microdevices provide exquisite control of tissue microenvironment for the investigation of organ-level physiology and disease. A 3D polarized epithelium using primary human gastrointestinal stem cells was developed to fully recapitulate gastrointestinal epithelial architecture and physiology. A planar monolayer comprised of stem/proliferative and differentiated primary cells is cultured on a shaped hydrogel scaffold with an array of crypt-like structures replicating the intestinal architecture. These planar layers display physiologic drug transport and metabolism and immunologically appropriate responses. Facile co-culture with other cell types such as immune cells or myofibrolasts is readily achieved. A dense mucus layer is formed on the luminal epithelial surface that is impermeable to bacteria and acts a barrier to toxins. The in vitro mucus has remarkably similar in its biophysical properties to that produced in vivo. Imposition of chemical gradients across the crypt long axis yields a polarized epithelium with a stem-cell niche and differentiated cell zone. The stem cells proliferate, migrate and differentiate along the crypt axis as they do in vivo. An oxygen gradient across the tissue mimic permits luminal culture of anaerobic bacteria while maintaining an oxygenated stem cell niche. This in vitro human colon crypt array replicates the architecture, luminal accessibility, tissue polarity, cell migration, and cellular responses of in vivo intestinal crypts. This bioanalytical platform is envisioned as a next-generation system for assay of microbiome-behavior, drug-delivery and toxin-interactions with the intestinal epithelia.