E prostanoid receptor 4 expressing macrophages promote the regeneration of the intestinal epithelial barrier upon inflammation

Dysfunctional resolution of intestinal inflammation and altered mucosal healing are essential features in the pathogenesis of inflammatory bowel disease (IBD). Intestinal macrophages are vital in the process of resolution of inflammation but the mechanisms underlying their mucosal healing capacity remains elusive. Here, we describe a subset of E prostanoid receptor 4 (EP4) expressing intestinal macrophages with mucosal healing properties both in human and mice. Notably, Csf1r-iCre EP4-fl/fl mice showed defective mucosal healing and intestinal epithelial barrier regeneration in a dextran sodium sulfate-induced colitis model. Mechanistically, an increased mucosal level of prostaglandin E2 (PGE2) triggers the secretion of chemokine (C-X-C motif) ligand 1 (CXCL1) in monocyte-derived EP4+ macrophages via MAPKs. Subsequently, CXCL1 drives epithelial cell differentiation and proliferation from regenerating crypts during the resolution phase of colitis. Thus, EP4+ intestinal macrophages are essential for the support of the intestinal stem cell niche and for the regeneration of the injured epithelium.