Microfluidic tools for studying epithelial tissues under shear flow with vasculature and microstructures
Doctor of Philosophy
Cells are subject to a wide range of mechanical stimulation and structural elements that affect their function. There is a need for platforms and methods that better model the physiology of complex tissues, such as the small intestine. In this thesis, I present tools for studying cells under laminar shear flow as well as micropatterning techniques for easily generating microvascular networks and crypt-villus microarchitecture. I have divided this research into three specific aims, discussing flow, microvascular networks, and crypt villus microarchitecture each in turn. Existing research tools to mimic these three aspects of physiology are often difficult to fabricate and set up. The techniques and devices that I present make use of various types of 3D printing to simplify fabrication, lower cost, and increase usability. In my first specific aim, I will discuss a device that is used to apply flow to a cell monolayer. In the small intestine, the epithelial cell monolayer is subjected to flow as fluids are moved the small intestine. I present a microfluidic device that simplifies the application of flow to cells. As a proof of concept, I demonstrate that bacterial and viral infections can be performed on monolayers cultured in this device under flow and static conditions. The results indicate that this device may allow monolayers to be cultured under infected conditions for longer than they can in static well plates and allow us to perform infections under more physiological conditions. In my second specific aim, I discuss a platform for rapidly forming microvascular structures. Vasculature is a critical microstructure present in most tissue and has important clinical relevance. For example, the gut-blood barrier regulates the passage of nutrients, drugs, and pathogens from the intestine into the blood. Here I present a simple technique for establishing networks of microvessel-like structures using sacrificial, alginate structures that can be conveniently frozen without a significant drop in viability. In my third specific aim, I present two methods for micropatterning crypt-villus structures, one compatible with photocrosslinkable materials and another compatible with physical crosslinking materials such as collagen. Crypt-villus architecture is critical to small intestinal function as it creates the stem cell niche and serves as the scaffold upon which differentiating cells migrate from the stem cell niche in the crypts to their terminal positions at the tips of the villi. These techniques and devices lay the groundwork for improved, physiological models of vascularized, mechanically stimulated, and micropatterned models of tissues.
small intestine; gut-on-a-chip; microfluidic; vasculature