Hayase et al. show that R-Spondin1 stimulates intestinal stem cells to differentiate to Paneth cells and enhances luminal secretion of α-defensins. Administration of R-Spondin1 or recombinant α-defensin prevents dysbiosis mediated by graft-versus-host disease, representing a novel approach to restore intestinal ecosystems and homeostasis.

Paneth cells contribute to small intestinal homeostasis by secreting antimicrobial peptides and constituting the intestinal stem cell (ISC) niche. Certain T cell-mediated enteropathies are characterized by extensive Paneth cell depletion coincident with mucosal destruction and dysbiosis. In this study, mechanisms of intestinal crypt injury have been investigated by characterizing responses of mouse intestinal organoids (enteroids) in coculture with mouse T lymphocytes. Activated T cells induced enteroid damage, reduced Paneth cell and Lgr5+ ISC mRNA levels, and induced Paneth cell death through a caspase-3/7-dependent mechanism. IFN-γ mediated these effects, because IFN-γ receptor-null enteroids were unaffected by activated T cells. In mice, administration of IFN-γ induced enteropathy with crypt hyperplasia, villus shortening, Paneth cell depletion, and modified ISC marker expression. IFN-γ exacerbated radiation enteritis, which was ameliorated by treatment with a selective JAK1/2 inhibitor. Thus, IFN-γ induced Paneth cell death and impaired regeneration of small intestinal epithelium in vivo, suggesting that IFN-γ may be a useful target for treating defective mucosal regeneration in enteric inflammation.

This study demonstrated the beneficial effects of adding weekend 1 g 5-ASA enema to daily 3 g oral 5-ASA as maintenance therapy for UC.

Graft-versus-host disease (GVHD) and infection are major obstacles to successful allogeneic hematopoietic stem cell transplantation (HSCT). Intestinal goblet cells form the mucus layers, which spatially segregate gut microbiota from host tissues. Although it is well known that goblet cell loss is one of the histologic features of GVHD, effects of their loss in pathophysiology of GVHD remain to be elucidated. In mouse models of allogeneic HSCT, goblet cells in the colon were significantly reduced, resulting in disruption of the inner mucus layer of the colon and increased bacterial translocation into colonic mucosa. Pretransplant administration of interleukin-25 (IL-25), a growth factor for goblet cells, protected goblet cells against GVHD, prevented bacterial translocation, reduced plasma concentrations of interferon-γ (IFN-γ) and IL-6, and ameliorated GVHD. The protective role of IL-25 was dependent on Lypd8, an antimicrobial molecule produced by enterocytes in the colon that suppresses motility of flagellated bacteria. In clinical colon biopsies, low numbers of goblet cells were significantly associated with severe intestinal GVHD, increased transplant-related mortality, and poor survival after HSCT. Goblet cell loss is associated with poor transplant outcome, and administration of IL-25 represents an adjunct therapeutic strategy for GVHD by protecting goblet cells.

Key Points Mn stimulates macrophages via Dectin-2 to induce donor Th17 differentiation after allogeneic bone marrow transplantation. Mn-induced Th17 cells accumulate in the lungs to cause pulmonary GVHD.

Plant virus expression vectors provide a powerful tool for basic research as well as for practical applications. Here, we report the construction of an expression vector based on plantago asiatica mosaic virus (PlAMV), a member of the genus Potexvirus. Modification of a vector to enhance the expression of a foreign gene, combined with the use of the foot-and-mouth disease virus 2A peptide, allowed efficient expression of the foreign gene in two model plant species, Arabidopsis thaliana and Nicotiana benthamiana. Comparison with the widely used potato virus X (PVX) vector demonstrated that the PlAMV vector retains an inserted foreign gene for a longer period than PVX. Moreover, our results showed that the GFP expression construct PlAMV-GFP exhibits stronger RNA silencing suppression activity than PVX-GFP, which is likely to contribute to the stability of the PlAMV vector.

The R-Spondin (R-Spo) family regulates WNT signaling and stimulates the proliferation and differentiation of intestinal stem cells (ISCs). R-Spo plays a critical role in maintaining intestinal homeostasis, but endogenous producers of R-Spo in the intestine remain to be investigated. We found that R-Spo3 was the major R-Spo family member produced in the intestine and it was predominantly produced by CD45−CD90+CD31+ lymphatic endothelial cells (LECs) in the lamina propria of the intestinal mucosa. Transcriptome analysis demonstrated that LECs highly expressed R-Spo receptor, Lgr5, suggesting an autocrine stimulatory loop in LECs. LECs were significantly reduced in number, and their R-Spo3 production was impaired in intestinal graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation. The impaired production of R-Spo3 in the intestine may be a novel mechanism of delayed tissue repair and defective mucosal defense in intestinal GVHD. We demonstrate a novel role of intestinal LECs in producing R-Spondin3 to maintain intestinal homeostasis.

Graft-versus-host disease (GVHD) is the major complication after allogeneic stem cell transplantation (SCT). Emerging evidence indicates that GVHD leads to injury of intestinal stem cells. However, it remains to be investigated whether skin stem cells could be targeted in skin GVHD. Lgr5 hair follicle stem cells (HFSCs) contribute to folliculogenesis and have a multipotent capacity to regenerate all epithelial cells in repair. We studied the fate of Lgr5 HFSCs after SCT and explored the novel treatment to protect Lgr5 HFSCs against GVHD using murine models of SCT. We found that GVHD reduced Lgr5 HFSCs in association with impaired hair regeneration and wound healing in the skin after SCT. Topical corticosteroids, a standard of care for a wide range of skin disorders including GVHD, damaged HFSCs and failed to improve skin homeostasis, despite of their anti-inflammatory effects. In contrast, JAK1/2 inhibitor ruxolitinib significantly ameliorated skin GVHD, protected Lgr5 HFSCs, and restored hair regeneration and wound healing after SCT. We, for the first time, found that GVHD targets Lgr5 HFSCs and that topical ruxolitinib represents a novel strategy to protect skin stem cells and maintain skin homeostasis in GVHD.