Nicholas Constantine Zachos, Ph.D.

The regulation of luminal surveillance and antigen sampling across mucosal surfaces remains an important and fundamental area of investigation. This is particularly true for the intestinal epithelium, which is constantly challenged to maintain homoeostasis with the complex microbiome while protecting the mucosa from pathogenic organisms. Microfold (M) cells of the Peyer’s patch (PP) play a crucial role in immune surveillance of the gut environment by transporting luminal antigens to underlying immune cells. This process is necessary to instruct appropriate immune responses; however, emerging evidence suggests a correlation between dysregulated microbiota and the development of GI diseases. Thus, there remains a need to understand the mechanisms responsible for mucosal responses to gut antigens in human disease. In addition, there is a need to investigate these mechanisms in primary models of the human intestinal mucosa. 

Human intestinal stem cell-derived epithelial cultures, or enteroids, provide a precision medicine-based approach to dissect the heterogeneity in GI diseases. Human intestinal enteroids (HIEs) are derived from LGR5+ actively dividing stem cells located at the base on the intestinal crypt. These stem cells give rise to all epithelial lineages including absorptive enterocytes, secretory cells (goblet, enteroendocrine, Paneth), as well as specialized epithelial cells including tuft and M cells. Advances in stem cell culture technology allow for the indefinite propagation of HIEs without changes in karyotype, genotype, or phenotype. Intestinal stem cells have defined epigenetic profiles that allows HIEs to mimic not only the intestinal segment from which they are derived, but also recapitulate patient-specific disease phenotypes of the donor at the time of specimen collection. 

Since the intestinal mucosa is a complex collection of multiple cell types in addition to the epithelium, our goal is to create co-culture models that include all human innate immune cells (e.g. antigen-presenting cells and innate lymphocytes) that normally reside in the intestinal mucosa. 

The proposed research program will define how gut antigens affect the integrity and surveillance functions of the intestinal epithelium and stimulate immune responses in novel co-culture models of the human intestinal mucosa, including PPs. These studies will be performed using HIEs from healthy donors and from patients with documented GI diseases since disease phenotypes are preserved in HIEs. Our research program will lead to the identification of the molecular mechanisms responsible for GI diseases in human models and the development of novel therapeutic strategies to treat them.