Dynamic flow and shear stress as key parameters for intestinal cells morphology and polarization in an organ-on-a-chip model.

Gut-on-a-chip microfluidic devices have emerged as versatile and practical systems for modeling the human intestine in vitro. Cells cultured under microfluidic conditions experience the effect of shear stress, used as a biomechanical cue to promote a faster cell polarization in Caco-2 cells when compared with static culture conditions. However, published systems to date have utilized a constant flow rate that fails to account for changes in cell shear stress ( $${\tau }_{c}$$ ) resulting from changes in cell elongation that occur with differentiation. In this study, computational fluid dynamics (CFD) simulations predict that cells with villi-like morphology experience a $${\tau }_{c}$$ higher than bulge-like cells at the initial growth stages. Therefore, we investigated the use of a dynamic flow rate to maintain a constant $${\tau }_{c}$$ across the experiment. Microscopic assessment of cell morphology and dome formation confirmed the initiation of Caco-2 polarization within three days. Next, adopting our dynamic approach, we evaluated whether the following decreased flow could still contribute to complete cell differentiation if compared with the standard constant flow methodology. Caco-2 cells polarized under both conditions, secreted mucin-2 and villin and formed tight junctions and crypt-villi structures. Gene expression was not impacted using the dynamic flow rate. In conclusion, our dynamic flow approach still facilitates cell differentiation while enabling a reduced consumption of reagents.