Single-cell RNA-seq profiles of colonic intestinal mucosa in IBS-D rats to explore the mechanism of immune barrier regulation in pathogenesis.

Imbalance of intestinal mucosal immune regulation is a key mechanism in diarrhea-predominant irritable bowel syndrome (IBS-D). We aimed to characterize this dysregulation in the intestinal mucosa at single-cell resolution. Intestinal mucosal cells from control and neonatal maternal separation-induced IBS-D rats were isolated and subjected to single-cell RNA sequencing (scRNA-seq). Bioinformatics analyses included clustering, differential expression, trajectory inference, and cell-cell communication assessment. We obtained transcriptomes from 4572 high-quality cells, identifying epithelial, stromal, immune, and endothelial lineages. In IBS-D rats, we observed a significant remodeling of the immune compartment, characterized by an increase in monocytes, mast cells, and cycling immune cells, alongside a decrease in T and B lymphocyte subsets. Epithelial cells showed upregulated expression of Krt7 and Foxa3, and downregulated expression of Cst6, Elapor1, and Kcnma1. Cell-cell communication analysis revealed enhanced interactions between epithelial and innate immune cells, involving ligands such as TIGIT. Regulon activity analysis highlighted key transcription factors, including Pax5 in B cells and Mafb in monocytes. Single-cell RNA sequencing reveals that immune barrier dysregulation in the intestinal mucosa of rats with IBS-D is associated with altered immune cell composition, dysregulated expression of epithelial function-related genes, and disrupted intercellular communication, providing novel insights into the pathogenesis of IBS-D. Our high-resolution scRNA-seq atlas delineates the cellular and molecular landscape of intestinal mucosal immune barrier dysfunction in IBS-D, pinpointing novel potential therapeutic targets for this disorder.