Gastrointestinal organoid structure and transport
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Organoids are three-dimensional (3D) self-assembled, mammalian tissue cultures derived from stem cells that differentiate to contain multiple cell types. These cells spatially organize within the 3D structure and are capable of recapitulating the structure and function of a particular organ. Organoids offer a variety of existing and potential applications in medicine and biotechnology, including drug formulation testing, regenerative medicine, and microbiome research. Despite their value, knowledge of how organoid structure impacts dynamics, mechanics, and transport is lacking. This is particularly true for gastrointestinal organoids, which are composed of a monolayer-thick epithelial sheet wrapped into a closed sphere. The primary goals of this dissertation are to understand the impact of gastrointestinal organoid structure on organoid function, develop a millifluidic chip platform to improve their viability and reliability as a model system and to explore their uses as model co-culture systems. To achieve this, we use a combination of time-lapse microscopy, image analysis, modeling, and fluidics fabrication techniques to develop an understanding of organoid growth and development in addition to expanding current uses as model systems. Our observations revealed that human gastric organoid growth was associated with cyclic rupture of the epithelial shell, rotational movement around their axes within the Matrigel matrix and luminal fusion by adjacent organoids. Furthermore, the rupture events are an indirect result of osmotic swelling carried out by the diffusion of water due to osmolyte concentration regulation by the epithelial shell. To overcome the advection limitation due to the topologically closed spherical structure of the organoids, we developed a millifluidic device called the Gut Organoid Flow Chip (GOFlowChip). This represents the first demonstration of established liquid flow through the luminal space of a gastrointestinal organoid. Given that organoids show great potential as model systems, established co-culture system consisting of dendritic cells (DC) with infected human gastric organoids shows the gastric epithelium actively recruits DCs for immunosurveillance with increased recruitment upon active Helicobacter pylori infection. Finally, investigation on CD103 attachment protein in gastric DCs revealed that CD103 engages in DC-epithelial cell interactions upon contact with epithelial E-cadherin but is not a significant driver of DC adhesion to gastrointestinal epithelia.