Aging and telomere dysfunction in the intestinal stem cell niche - intestinal stem cell (ISC) activity declines with age, contributing to malabsorption and loss of intestinal barrier function

The National Institute on Aging (NIA) awarded the University of Pennsylvania a Project Grant of $333,116 under the Aging Research program (CFDA 93.866) effective September 1, 2025, through August 31, 2026. This award supports biomedical research directed toward understanding aging processes and age-related diseases. The research project investigates the relationship between telomere dysfunction, aging, and intestinal stem cell (ISC) niche function, with the goal of understanding how both natural aging and acute telomere failure suppress stromal niche support for intestinal stem cells. The research team will utilize a novel mouse model to directly visualize and isolate telocytes (stromal niche cells) that supply Wnt ligands to the stem cell compartment, examining how disruption of the canonical Wnt/β-catenin signaling pathway contributes to intestinal dysfunction in aging and telomeropathies such as dyskeratosis congenita.

The research will advance understanding of mechanisms underlying malabsorption and loss of intestinal barrier function associated with aging. By establishing causal links between telomere uncapping and intestinal stem cell defects through examination of both aged and telomereopathic intestinal tissue in mice and human subjects, this project contributes to the NIA's mission of supporting research to prevent and treat age-related diseases. The research takes place at the University of Pennsylvania in Pennsylvania and represents a one-year intensive study period designed to characterize the role of the mesenchymal stem cell niche in maintaining intestinal homeostasis during aging.

ISC aging is accompanied by telomere uncapping, and the ISC defects in humans and mice with prematurely uncapped telomeres (e.g. dyskeratosis congenita patients and mterc KO mice) demonstrate that telomere uncapping is a cause of ISC dysfunction. Remarkably, both aging and telomere uncapping inhibit the canonical WNT/β-catenin pathway, which is normally required for iscs to support the tissue's rapid cell turnover. Moreover, experimental restoration of WNT pathway activity rescues ISC defects in both settings. Although we and others have found WNT defects in both aged and telomereopathic intestinal epithelium and underlying stroma of mice and humans, the identities of key cellular players RE poorly understood. Recently, populations of mesenchymal cells in the lamina propria directly underlying the epithelium have been identified as a critical source of WNT ligands required for ISC proliferative self- renewal. In the context of telomere dysfunction (or normal aging), iscs exhibit a loss of self-renewal activity and a broad downregulation of WNT target gene expression, corresponding to the downregulation of WNT ligands now known to be secreted from this subepithelial mesenchyme. The goal of this proposal is to understand the consequences of telomere dysfunction and aging on ISC niche function. We hypothesize that both natural aging and acute telomere failure suppress stromal niche support for iscs, contributing to the intestinal phenotypes associated with aging and telomeropathies such as dyskeratosis congenita. To address this hypothesis, we developed a novel mouse line that allows for direct in situ visualization and prospective isolation of stromal niche cells (telocytes) which supply WNT ligands to the stem cell compartment. We will examine telocytes, along with additional niche components, in the context of temporal aging and acute telomere failure in mterc-/- mice lacking the telomerase RNA component (mterc), which leads to progressive telomere dysfunction. We will determine how aging and telomere defects alter niche function using a combination of in situ assays, single-cell transcriptomics, and organotypic CO-culture assays in which primary stroma and intestinal organoids from either aged (VS. Young) or telomereopathic (VS. Control) epithelium are isolated and CO-cultured in heterochronic or genotype admixed contexts, respectively. We will also pursue provocative preliminary observations that wildtype bone marrow transplantation restores ISC activity in mterc-/- mice to address the hypothesis that marrow-derived cells can engraft into the subepithelial stroma and rescue failing epithelium. Ultimately, this proposal will elucidate how aging and telomere dysfunction alter the ISC niche, and will begin to evaluate novel strategies to ameliorate niche dysfunction.