Gut/Liver-on-a-chip models

The length of an experiment will depend on the application, for example, drug metabolism studies are typically shorter than studies focussing on organ crosstalk. The gut model is pre-cultured in static conditions to achieve a fully differentiated monolayer, then added to the dual-organ plate in co-culture with primary human hepatocytes. For ADME applications drugs are dosed for between 48- and 72-hours with periodic media sampling taken to quantify drug concentration.

Our Caco-2/HT-29 gut microtissues display similar tight junction formation, mucus secretion and metabolic function to in vivo gut tissue. The microtissues in perfused culture mimic the 3D shape of in vivo gut villi, but they are not recreated to the same depth.

For the primary Gut/Liver-on-a-chip model, intestinal epithelial stem cells are expanded and then differentiated to form a polarized monolayer that expresses tight junction proteins. All major cell lineages are achieved including goblet cells that are mucus-producing.

The permeability of barriers can be assessed in several ways, measuring the transepithelial electrical resistance (TEER) is a common one. This provides a quantitative estimation of the barrier strength and integrity. We can also measure the permeability of molecules of different sizes, to estimate the extent of passive diffusion allowed by the cell barrier. Whereas TEER measurements are taken throughout the experiment to monitor cell barrier growth and differentiation, permeability tests are carried out at the end, to confirm the stability of the barrier post drug dosing.

For the co-culture of primary gut and liver tissues, we have developed a specialized/proprietary media that maintains the functionality of both cell types during crosstalk and ADME studies. This will be one of the components of a future ‘in-a-box’ kit that will contain all media, cells, OOC plates and assays to enable Gut/Liver studies in your lab.

Media in the gut apical compartment is separated by the gut barrier with media that circulates between the gut basolateral and liver compartment. Nutrients and drug compounds can diffuse through the gut barrier by either passive or active diffusion. Liver microtissue will be exposed to drugs absorbed by gut tissue, likewise, the gut tissue will be exposed to metabolites released by the liver tissue, reproducing an in vivo-like crosstalk between the two organs.

Yes, we have adopted a programmable approach which enables flow rates and profiles (pulsatile or continuous) to be individually tuned within the gut and liver chambers to mimic each organ’s exposure to the fluid shear forces and dynamic mechanical stresses that occur in vivo. This is achieved through robust materials, tightly controlled pneumatics and micropumps embedded into the Multi-chip Dual-organ plates which accurately and reliably move media around tissue structures or between organ mimics for weeks to maintain the performance of that culture over extended periods of culture. Please watch the on-demand webinar: The Rhythm of Life for a detailed explanation.

Altis Biosystems source and expand region-specific intestinal epithelial stem cells from human tissue. Biobanked cells are seeded onto a semi-permeable membrane (Transwell^®) coated with a biomimetic scaffold. Within seven to eight days of culture, you get a fully differentiated, polarized jejunum epithelium with basal and apical cell access. The tissue is then inserted into the barrier compartment/chamber of our Multi-chip Dual-organ plate. For more info on their model, please visit the Altis Biosystems website.

We are currently developing an in-a-box solution complete with a fully validated SOP, common media, Multichip Dual-organ plates and all the 3D validated cells required so that you can recreate our fully human multi-organ model in your laboratory with ease. Whilst we work on a commercialized kit, you can access the model/submit molecules for testing via our ADME Contract Research Services. In the interim, the Caco-2 immortalized gut in vitro model, in combination with our primary hepatocyte liver model, enables you to get started within your laboratory, validate the approach and benefit from insights into the contribution to drug metabolism by the gut and liver when these two organs are connected to better inform in vivo studies.

Mucus can be visualised by histology of the gut barrier or immunofluorescence staining of mucin proteins. For quantification, there are commercially available ELISA kits to quantify mucus production.

Tissue-specific readouts can be obtained during the pre-culture of gut barrier and liver tissue. Once the two organs are connected into a fluidically-linked system, additional readouts enable the effects of crosstalk to be measured (please visit the Bioavailability and Drug Metabolism Application pages for more info). For liver tissue, the main readouts are CYP3A4 activity and albumin. For gut tissue, the main readouts are TEER and permeability to assess barrier integrity. When in co-culture there is >2mL of circulating media, which provides plenty of material to quantify protein concentration using ELISA or other metabolomic-based assays. RNA from both tissue types can be extracted for transcriptomic studies.

For the gut tissue, cells are pre-seeded on Transwells and then expanded and differentiated before addition to the dual-organ plate. Primary human hepatocytes are seeded directly onto collagen-coated scaffolds in the liver compartments of the Dual organ plate.

Visit the Bioavailability Application page to visualize the timeline