Biology subjects

Espenschied, S. T.

Publications and source records attributed to Espenschied, S. T..

3 recordsLinked to original sources

bioRxiv2024

Intestinal stem cells enhance local mucosal immunity through apoptotic body phagocytosis

Modulation of immune tone at mucosal surfaces is critical to maintain homeostasis while facilitating the handling of emerging threats. One dynamic component of immune modulation is the phagocytosis and clearance of apoptotic bodies known as efferocytosis that inhibits inflammation by promoting its resolution. Here, we evaluated the effects of apoptotic body phagocytosis by intestinal epithelial stem and progenitor cells (ISCs). Unexpectedly, instead of immunomodulation through efferocytosis, this process elevated local immune system activity. To achieve this result, ISCs actively engaged apoptotic bodies in a unique fashion, leading to their engulfment and ultimate delivery to lysosomes for processing. We found that ISCs were capable of actively recruiting inert material such as apoptotic bodies by using actin-based intrinsic biomechanical processes. Uptake of apoptotic bodies was facilitated by complement factor C3 produced by apoptotic bodies themselves. ISCs in turn generated signals heightening T cell activity that was driven in part by ISC-generated TNF. Taken together, uptake of apoptotic bodies by ISCs produced a local inflammatory alert to specific immune cells. This altered paradigm for the response to phagocytosed apoptotic bodies fits the needs of active mucosal surfaces and demonstrates that efferocytosis as currently defined is not a universal response of all cell types.

cell biology↗

bioRxiv2024

Long-Term Monolayer Cultivation Captures Homeostatic and Regenerative Features of Human Colonic Epithelial Cells

Primary intestinal epithelial stem cell culture methods have significantly advanced understanding of mammalian intestinal development and disease. However, progress has been hampered by inconsistent methodological reporting and challenges comparing in vitro systems with in vivo observations. We previously established a unique method for long-term 2{-}dimensional (2D) cultivation of mouse lECs using an air-liquid interface (ALI) technique which appears to faithfully recapitulate homeostatic and regenerative features in vitro. Here, we further refined these methods and optimized protocols for long-term, self-organizing 2D cultivation of human lECs. During the culture, we observed that epithelial cells undergo a dynamic morphological transition from squamous to columnar shape. Using single cell transcriptomics, we identified both major lineages and minor populations, including enteroendocrine cells, tuft cells, and BEST4/CA7+ cells. Leveraging the power and scalability of a biomedical foundation model (BMFM) trained on single cell RNA sequencing data, we performed classification tasks to identify cell types across sample sources and to quantitatively benchmark our in vitro differentiated cells against cells collected from patient biopsies. We observed a striking degree of similarity between our in vitro differentiated cells and the corresponding cell types in vivo for multiple differentiated lineages. This novel approach using BMFM holds promise to expand our understanding of the regulatory mechanisms including gene-gene regulation underlying homeostasis and regeneration as well as the functions of rare and poorly understood lineages within the human intestinal epithelia. Moreover, these methods are generalizable to other organs and can be used to assess the correspondence of cells across experimental modalities. SignificanceThis manuscript addresses challenges in quantitative comparisons of cell types grown in vitro vs their in vivo counterparts. Here we use the intestinal epithelium as a model system to address this challenge. We devised an in vitro culture platform that supports multipotent intestinal epithelial stem cells and their numerous differentiated progeny. This system gives rise to all known rare and abundant lineages in correct proportions. Novel use of biomedical foundation models pre-trained on publicly available data and then fine-tuned to data from this platform enabled demonstration of high concordance of multiple in vitro differentiated lineages with the corresponding cells in vivo.

cell biology↗

bioRxiv2018

Intestinal Serum Amyloid A suppresses systemic neutrophil activation and bactericidal activity in response to microbiota colonization

The intestinal microbiota influence diverse aspects of host physiology, including the development and function of myeloid lineages. Numerous host and microbial factors are known to poise neutrophils and other granulocytes for response to pathogens and danger signals, yet the mechanisms by which the intestinal microbiota regulate this process are largely unknown. Using gnotobiotic zebrafish, we identified the immune effector Serum amyloid A (Saa) as one of the most highly induced transcripts in digestive tissues following microbiota colonization. Saa is a conserved secreted protein produced in the intestine and liver with described effects on neutrophils in vitro, however its in vivo functions are poorly defined. We engineered saa mutant zebrafish to test requirements for Saa on innate immunity in vivo. Zebrafish mutant for saa displayed impaired neutrophil responses to wounding but augmented clearance of pathogenic bacteria. At baseline, saa mutants exhibited moderate neutrophilia and altered neutrophil tissue distribution. Molecular and functional analyses of isolated neutrophils revealed that Saa suppresses expression of pro-inflammatory mRNAs and bactericidal activity. Saas effects on neutrophils depends on microbiota colonization, suggesting this protein mediates the microbiotas influence on host innate immunity. To test tissue-specific roles of Saa on neutrophil function, we generated transgenic zebrafish over-expressing saa in the intestine. Transgenic intestinal saa expression was sufficient to partially complement the neutrophil phenotypes in saa mutants. These results indicate Saa produced by the intestine in response to microbiota serves as a systemic signal to neutrophils to restrict aberrant activation, decreasing inflammatory tone and bacterial killing potential while simultaneously enhancing their ability to migrate to wounds.

immunology↗