Colonic spermidine promotes the proliferation and migration of intestinal epithelial cells.

The gut microbiome, comprising trillions of diverse microorganisms, profoundly influences the efficient development and maintenance of the intestinal barrier. While shifts in microbial composition are observed in Inflammatory Bowel Disease (IBD) and Colorectal Cancer (CRC), the causal relationship between these changes and resolution of inflammation remains elusive. Notably, IBD is not only marked by shifts in microbial composition but also by changes in microbial metabolites. Polyamines, produced by both gut bacteria and human cells, have emerged as potential regulators of gut pathology, cancer and mucosal repair. Investigating how elevated polyamine levels influence intestinal epithelial cells (IEC) can provide insights into their role in the regeneration of mucosal epithelia and restoration of gut barrier functions. To dissect the complex interplay between the gut microbiome, polyamines, and IEC, we focused on the overrepresented bacterium B. uniformis and its primary metabolite, spermidine. Here, we show that B. uniformis, a dominant member of gut microbiota, expands during the repair & resolution phase of the chemically induced chronic murine colitis. Furthermore, we found that the abundance of colonic polyamines was also altered, with spermidine being the abundant polyamine. Our RNA sequencing and transcriptomic analysis of cultured colonic epithelial cells demonstrate that spermidine regulates the expression of genes and pathways involved in different cellular functions, including proliferation, differentiation, adhesion, lipid metabolism, migration, chemotaxis, and receptor expression. We also found that spermidine stimulates the proliferation of cultured colonic epithelial cells in vitro. Additionally, our findings indicate that spermidine enhances the migrations of enterocytes. Our study emphasizes the crucial functions of the gut microbiome and polyamines in governing the functions of intestinal epithelial cells. Thus, these microorganisms and their metabolic byproducts hold promise as prospective therapeutic agents.