Complement C3a-C3aR signaling in the colon epithelium 4117

Abstract Description The liver-derived complement system has been considered the body’s main source for the complement cascade. Recently, complement C3 was found to be expressed in the gut under steady-state conditions and during inflammatory conditions. However, a major gap in knowledge exists regarding C3aR expression in the colon epithelium and how C3a-C3aR signaling affects intestinal stem cells (ISC) differentiation. We generated human colonic organoids derived from endoscopic biopsies to assess the C3 pathway. Organoids were kept in a stem state or allowed to differentiate via the removal of Wnt3a. Recombinant human complement C3a was used to stimulate organoids. Organoids were assessed for C3, C3aR, Chromogranin A, and GLP-1 expression by immunofluorescence. We found the levels of C3 and C3aR increased in colonic organoids upon differentiation and in the absence of C3a stimulation. In mature colonic epithelium, C3aR was also expressed on the mitochondria. Additionally, we found C3a stimulation increased the number of enteroendocrine cells, specifically, L cells upon differentiation. Our data demonstrates C3a-C3aR signaling may be critical for enteroendocrine cell differentiation. In addition, the localization of C3aR on the mitochondria suggest C3a signaling may play a critical role in colonic epithelial mitochondrial metabolism. These studies highlight a novel interaction between the gut complement system and mucosal surfaces. Funding Sources Institutional Research Grant, IRG-21-146-25 from the American Cancer Society Topic Categories Mucosal and Regional Immunology (MUC)