NFAT5 dictates crosstalk between intestinal epithelial regenerative capacity and microbiota in murine colitis models.

Hypertonic and hyperosmolar stimuli frequently pose challenges to the intestinal tract. Therefore, a resilient epithelial barrier is essential for maintaining gut homeostasis in the presence of osmotic perturbations. NFAT5, an osmosensitive transcription factor, primarily maintains cellular homeostasis under hypertonic conditions. However, the osmoprotective role of NFAT5 in enterocyte homeostasis is poorly understood. Here, we demonstrate that NFAT5 is critical for the survival and proliferation of intestinal epithelial cells (IECs) and that its deficiency accelerates chemically induced or spontaneous colitis in mice. Mechanistically, NFAT5 promotes the survival of IECs and the renewal of intestinal stem cells, thereby regulating the production of mucus and antimicrobial compounds, including RegIII and lysozyme, which consequently shape the gut microbial composition to prevent colitis. Transcriptome analysis identifies HSP70 as a key downstream target of NFAT5 in epithelial regeneration. Loss- and gain-of-function experiments of HSP70 revealed that NFAT5 mitigates experimental colitis through IEC Hsp70, which protected stem cells from inflammation-induced injury and maintained barrier function. In conclusion, our study demonstrates a previously unknown role for NFAT5 in dictating the crosstalk between intestinal stem cells and the microbiota, underscoring the importance of the NFAT5-HSP70 axis in maintaining epithelial regeneration related to gut barrier function, balancing microbial composition, and subsequently preventing colitis progression.