# Cold Exposure Alleviates Colitis via Parallel Integration of Colonic Mucosal Regeneration and Ileal Antimicrobial Defense

## TL;DR

Cold exposure helps reduce colitis by boosting gut cell regeneration and improving antimicrobial defenses in the intestines.

## Contribution

The study reveals a novel mechanism where cold exposure integrates colonic regeneration and ileal antimicrobial defense to alleviate colitis.

## Key findings

- Cold exposure activates intestinal epithelial proliferation and stem cell markers like Lgr5 and Ascl2.
- Cold exposure induces a Paneth-like cell phenotype and enhances antimicrobial peptide gene expression in ileal Paneth cells.
- The gut microbiota in inflamed intestines is reshaped by cold exposure through improved antimicrobial defenses.

## Abstract

Background: Inflammatory bowel disease (IBD) involves chronic intestinal inflammation, epithelial barrier disruption, and dysbiosis, with environmental factors playing a significant role in its pathogenesis. Previous work revealed that cold exposure alleviates colitis in mice; this study extends that finding by demonstrating that cold exposure enhances intestinal regeneration even in healthy mice, upregulating proliferation markers (Mki67, PCNA, Cyclin D1). Methods: Applying this pro-regenerative effect to a colitis model, we investigated the underlying mechanisms through multi-omics analysis, transmission electron microscopy (TEM), immunofluorescence, and pathological staining as well as 16S rRNA sequencing. Results: We found that cold exposure activates intestinal epithelial proliferation pathways. Further analysis indicated that cold exposure induces colonic stem cell regeneration, upregulating stem cell markers Lgr5 and Ascl2. Notably, colonic transcriptomic profiling revealed the emergence of a Paneth-like cell phenotype, characterized by altered expression of specific lineage genes. Furthermore, cold exposure simultaneously promoted the accumulation of secretory granules and upregulated the expression of antimicrobial peptide genes (such as Lysozyme and Defa) in ileal Paneth cells. This enhanced ileal antimicrobial defense effectively reshaped the gut microbiota in inflamed intestines. Conclusions: This research elucidates a mechanism whereby cold adaptation promotes mucosal repair by integrating localized colonic epithelial regeneration with enhanced ileal Paneth cell-mediated antimicrobial defense. This offers compelling new perspectives on how environmental factors, such as cold exposure, could influence the pathophysiology of IBD and contribute to intestinal regeneration, which may provide foundational theoretical support for the future diagnosis and treatment of IBD.