Aging of the Colon - A Mechanistic View

The colon is one of the gastrointestinal organs most profoundly affected by aging. Recent advances in our understanding of both colonic physiology and the general mechanisms of aging have significantly expanded our knowledge of the types and underlying processes of colonic aging. In this review, we summarize current insights into the cellular and molecular mechanisms that drive physiological aging of the human colon. We examine the unique structural and functional features of key components of the colon, including the epithelium, local immune system, microbiome, enteric neurons, and smooth muscle cells, and explore how aging affects each of these cell populations, ultimately impacting overall colonic function. In the epithelium, increased mutational burden does not appear to be the primary driver of age-related dysfunction. Instead, dysregulation of signaling pathways such as EGF and Wnt is likely responsible for key phenotypic changes. Aged colonic neurons display protein misfolding and axonal dysfunction reminiscent of aging processes observed in the central nervous system. Similarly, smooth muscle cells exhibit impaired contractility, which is associated with disruptions in calcium homeostasis and deficits in cholinergic signaling. At the same time, age-related activation of the local immune system mirrors broader immunosenescence and may be further influenced by shifts in the gut microbiome, although a consistent aging-associated microbiome signature has yet to be identified. These multifaceted changes, combined with the colon's inherent regional and cellular complexity and the challenges of modeling human colonic aging, continue to fascinate but also pose substantial obstacles for research. Emerging experimental models and clinical strategies offer promising avenues for improving the prevention and treatment of age-associated colonic dysfunction.