Intestinal Epithelial Heat Shock Protein 25/27 integrates host immune and microbial drivers required for mucosal restitution following inflammatory injury of the gut - Project Summary/Abstract Mucosal healing is an essential physiological response to inflammatory and injurious diseases of the bowel, including ischemic colitis, radiation-induced mucosal injury, and inflammatory bowel diseases (IBD). In fact, successful and complete mucosal healing in IBD is associated with better clinical outcomes, longer remission, and lower risk of complications like fibrosis, bleeding, and colorectal cancer1. Yet, few therapies in current use are designed to target this important aspect of patient care in large part because of gaps in knowledge about the mediators and mechanisms underlying intestinal epithelial cell (IEC) restitution following injury. We recently discovered that the poorly understood small molecular weight heat shock protein, Hsp25 (the human form is Hsp27) which is highly regulated by colonic anaerobic microbiota, is essential for intestinal mucosal restitution following mucosal injury. We show scientific merit for the hypothesis that IEC Hsp25/27 is key to two essential events necessary for wound healing, (1) promoting IEC restitution through changes in gene transcription that promote IEC proliferation and maturation, and (2) ensuring directional cell movement to injured areas. The former is highly dependent on the interactions of phospho-STAT3 and Hsp25/27 and the latter appears to involve Hsp25/27-dependent formation of actin-stress filaments and assembly and stabilization of focal adhesion plaque (FAP) complexes necessary for directional cell movement. Whether the Hsp25/27- dependent mucosal restitution and directional cell movement are dependent or independent will also be addressed. To better understand the intricacies and mechanistic basis of these pathways, three specific aims are proposed: (1) to test the hypothesis that IEC Hsp25/27 is essential for gut mucosal healing using multiple in vitro and in vivo models of colonic injury and to disentangle the potential role of Hsp25 in mitigation of mucosal inflammation from a direct role in promoting mucosal restitution; (2) to define the role of pSTAT3-Hsp25 interaction in the assemblage and stabilization of nuclear transcriptional complexes and their genetic programs that promote IEC proliferation, differentiation and function; and (3) to determine the mechanisms underlying IL- 22 stimulated, Hsp25-dependent directional cell movement and if they are independent of Hsp25-dependent activation of pSTAT3. The studies will employ unique conditional and inducible murine models and organoid lines derived from them where IEC Hsp25 gene expression has either been deleted, constitutively expressed, or induced to provide mechanistic insights into the organismal, cellular, molecular, and genetic bases that are essential to the mucosal healing response in chronic inflammatory diseases of the bowel. The insights gained will create opportunities to restore elements of the host-microbe mucosal healing circuitry that can lead to better and sustained clinical outcomes and opportunities for wound healing drug discovery and interventions.
