ORCID

http://orcid.org/0000-0003-1304-2616

Date of Award

Spring 5-15-2023

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Immunology)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Millions of finger-like structures called villi line the small intestine, providing an enormous surface area for rapid and efficient nutrient absorption. Collapse of the villus architecture, known as villus atrophy, is often observed in response to pathogen invasion, inflammation, medications, and ischemia due to loss of intestinal epithelial cells, resulting in symptoms of diarrhea and malabsorption. Though removal of the inciting agent generally allows for near complete tissue recovery, some individuals take longer to restore their villi, a condition known as persistent villus atrophy, for reasons that are unknown. How intestinal villi cope with tissue damage and re-establish their structure remains poorly understood, yet their capacity to do so is vital for survival. Here, I developed a robust and highly reproducible injury-repair model that specifically targets the villus compartment of the small intestine. This system, which entails a single intraperitoneal injection of the double-stranded RNA analog poly(I:C) in mice, mimics key aspects of acute viral gastroenteritis and displays a consistent repair and regeneration pattern following injury. Using this model, I identified a transient, damage-induced epithelial cell type covering the surface of atrophic villi. Intriguingly, these atrophy-induced villus epithelial cells (aVECs) possessed a fetal-like transcriptional profile, yet were terminally differentiated and lineage-committed. The primary function of aVECs was to quickly re-establish the intestinal barrier after villus damage. I further determined yes-associated protein (YAP), one of the major transcriptional mediators of the Hippo signaling pathway, as a crucial regulator of aVEC function. In the absence of YAP, aVECs were unable to properly restore the intestinal barrier post-injury. As a result, villus regeneration was markedly hampered in YAP-deficient mice. Finally, I found evidence of aVEC-like cells in human disease states with villus injury, such as Crohn’s and celiac disease. Given that aVECs were derived from progenitor cells in the crypt, I defined a key repair mechanism involving the activation of a fetal-like program during injury-induced differentiation, a process I term “adaptive differentiation”. Thus, I propose adaptive differentiation as an important healing mechanism in high turnover tissues such as the intestine.

Language

English (en)

Chair and Committee

Thaddeus S. Stappenbeck Marco Colonna

Committee Members

Maxim N. Artyomov, Samantha A. Morris, David M. Ornitz, Steven J. Van Dyken,

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