R-Spondin 1 expands Paneth cells and prevents dysbiosis induced by graft-versus-host disease

3507 IntroductIon Trillions of microbes inhabit mammals, with the largest population in the intestinal tract, and play vital roles in a host’s metabolism and immunity (Qin et al., 2010). Composition of intestinal microbiota is mainly maintained by luminal secretion of antimicrobial peptides (AMPs) from Paneth cells. α-Defensins are the most bactericidal AMPs released from Paneth cells (Ayabe et al., 2000; Salzman et al., 2010). Emerging evidence demonstrates that Paneth cell functions are impaired in various inflammatory and metabolic disorders, resulting in unfavorably altered intestinal microbiota (dysbiosis; Salzman and Bevins, 2013). Dysbiosis, however, exacerbates the underlying diseases, thus creating a vicious cycle between the host and microbiota. Graft-versus-host disease (GVHD) is an alloreactive, donor T cell–mediated inflammatory disease that occurs after allogeneic hematopoietic stem cell transplantation (SCT), involving the skin, liver, and gastrointestinal tract (Ferrara et al., 2009). We and others have shown that GVHD leads to a loss of Paneth cells and mediates intestinal dysbiosis (Eriguchi et al., 2012; Jenq et al., 2012). The dysbiosis that occurs in MHC-mismatched mouse models of GVHD is remarkable and thus represents a feasible tool to test novel strategies to modulate dysbiosis (Eriguchi et al., 2012). Current strategies to restore the gut ecosystem are bacteriotherapy, using diet, prebiotics/probiotics, and fecal microbiota transplantation; however, no physiological approach has been developed so far. Here, we demonstrate a novel approach to restore intestinal microbial ecology and prevent dysbiosis by Wnt agonist R-Spondin1 (R-Spo1; Kim et al., 2005; Takashima et al., 2011) or recombinant α-defensin (Tomisawa et al., 2015) in mice. The Wnt agonist R-Spo1, which binds to leucine-rich repeat–containing G protein–coupled receptor (Lgr) 5, is one of the essential factors to build intestinal villus-crypt units from a single Lgr5 intestinal stem cell (ISC; Sato et al., 2009; de Lau et al., 2011; Farin et al., 2016). We found that R-Spo1 stimulates ISCs to differentiate to Paneth cells and enhanced luminal secretion of α-defensins. In adthe intestinal microbial ecosystem is actively regulated by Paneth cell–derived antimicrobial peptides such as α-defensins. Various disorders, including graft-versus-host disease (GVHd), disrupt Paneth cell functions, resulting in unfavorably altered intestinal microbiota (dysbiosis), which further accelerates the underlying diseases. current strategies to restore the gut ecosystem are bacteriotherapy such as fecal microbiota transplantation and probiotics, and no physiological approach has been developed so far. In this study, we demonstrate a novel approach to restore gut microbial ecology by Wnt agonist r-Spondin1 (r-Spo1) or recombinant α-defensin in mice. r-Spo1 stimulates intestinal stem cells to differentiate to Paneth cells and enhances luminal secretion of α-defensins. Administration of r-Spo1 or recombinant α-defensin prevents GVHd-mediated dysbiosis, thus representing a novel and physiological approach at modifying the gut ecosystem to restore intestinal homeostasis and host–microbiota cross talk toward therapeutic benefits. R-Spondin1 expands Paneth cells and prevents dysbiosis induced by graft-versus-host disease