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Author ORCID Identifier

https://orcid.org/0000-0002-6273-0119

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

Year Degree Awarded

2020

Month Degree Awarded

September

First Advisor

Neil S. Forbes

Second Advisor

Jungwoo Lee

Subject Categories

Biochemical and Biomolecular Engineering | Biochemistry | Biological Engineering | Biomaterials | Biophysics | Biotechnology | Cell Biology | Food Microbiology | Immunology of Infectious Disease | Microbial Physiology | Molecular, Cellular, and Tissue Engineering | Transport Phenomena

Abstract

The mucosal barrier in the intestine is vital to maintain selective absorption of nutrients while protecting internal tissues and maintaining symbiotic relationship with luminal microbiota. This bio-barrier consists of a cellular epithelial barrier and an acellular mucus barrier. Secreted mucus regulates barrier function via in situ biochemical and biophysical interaction with luminal content that continually evolves during digestion and absorption. Increasing evidence suggests that a mucus barrier is indispensable to maintain homeostasis in the gastrointestinal tract. However, the importance of mucus barrier is largely underrated for in vitro mucosal tissue modeling. The major gap is the lack of experimental material (i.e. functional mucins) and platforms to integrate a relevant thickness of mucus layer with an epithelium under physiological conditions. Here we report our progress on developing humanized micro-physiological models of the intestines in static and dynamic settings by using natural mucins derived from porcine small intestines (PSI). To overcome limited availability of mucus, we developed a simple and scalable method for mucus extraction by directly solubilizing the luminal mucus layer from PSI that is readily accessible.The mucus barrier was successfully integrated with human epithelial cell layer (HT-29) co-cultured with immune cells (THP-1), which allowed the studies of bi-directional crosstalk between luminal content and tissue immune cells through a physiologically relevant mucosal interface. The applied mucus barrier did not cause any cytotoxic or immunogenic effects to human intestinal and immune cells. As expected, mucus prevents the transmigration of probiotic bacteria VSL#3. In the absence of mucus, these bacteria caused epithelial damage, immune cell differentiation and induced production of pro-inflammatory cytokines IL-8 and TNF-α. The most intriguing result from these studies was that mucus increased the transmigration of pathogenic Salmonella. Breach of the mucosal barrier by Salmonella induced production of IL-8 and TNF-α. Taking bioengineering approaches, we have developed mucosal barrier models of intestines under static (transwells) and dynamic conditions (microfluidics). Established models represent cellular and extracellular complexities in a controlled and accessible manner. We envision that in vitro mucosal barrier models will serve as an enabling tool for understanding basic biology and disease progression in the intestines.

DOI

https://doi.org/10.7275/9kst-3g07

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Available for download on Monday, March 01, 2021

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