(42a) A Microfluidics-Based in Vitro Model of Anterior-Posterior Gut Patterning

In this work, we demonstrate, for the first time, spatially controlled differentiation of human pluripotent stem cells (hPSCs) into the anterior foregut (AFG) and mid/hindgut (MHG) cell types within a single cell monolayer using chemical gradient-generating microfluidics. This result represents an advance in the ongoing efforts to harness the processes by which complex tissues arise during embryonic development in vitro—a long-standing goal of tissue engineering and regenerative medicine. In embryos, uniform populations of stem cells are exposed to spatial gradients of diffusible extracellular signaling proteins, known as morphogens. Varying levels of these signaling proteins induce stem cells to differentiate into distinct cell types at different positions along the gradient, thus creating spatially patterned tissues.

To accomplish this spatially controlled differentiation, or patterning, we combined principles of engineering and biology to develop a novel, reproducible, and easily accessible method for the anterior-posterior patterning of hPSCs. We performed a 6-day, on-chip differentiation protocol within a commercially available microfluidic chip. We used finite element analysis to model the distribution of morphogens within the microfluidic device and determined that the chip can generate two stable and opposing linear morphogen gradients. Quantitative analysis of immunofluorescence data showed that expression of AFG and MHG markers is localized to their respective morphogen sources and that both display a decreasing linear profile with increasing distance from their sources. This platform thus allows us to explore fundamental questions about how a single population of stem cells differentiate into multiple cell types along a body axis in response to exposure to morphogen gradients, such as whether the response in marker expression is graded or discretized as well as the influence of neighboring cells on cell fate decisions. Our in vitro model contributes to the stem cell and developmental biology toolkit and may eventually pave the way to create increasingly spatially patterned tissue-like constructs in vitro.