Abstract
Damage to the gastrointestinal (GI) tract by pretransplant conditioning regimen plays a critical role in amplifying graft-versus-host disease (GVHD). Thus protection of the GI tract from conditioning may represent a novel approach to prevent GVHD. R-Spondin1 (R-Spo1) is a novel class of soluble activator for Wnt/□-catenin signaling, and has potent and specific proliferative effects on the intestinal crypt cells; injection of R-Spo1 protects mice from chemotherapy-induced intestinal mucositis. We therefore hypothesized that administration of R-Spo1 could modulate GVHD by reducing the GI tract damage and improve outcome of allogeneic bone marrow transplantation (BMT). Lethally irradiated B6D2F1 (H-2b/d) mice were injected with 5 × 106 BM and 2 × 106 T cells from MHC-mismatched B6 (H-2b) donors on day 0. Mice were intravenously injected with 200 μg of R-Spo1 or diluent from days −3 to −1 and +1 to +3 after BMT. In vivo labeling assay of mitotic cells with BrdU demonstrated that the proliferative index, as determined by the percentages of BrdU-positive cells among crypt epithelial cells, was significantly greater in the small intestine of R-Spo1 treated mice than controls 4 days after BMT (57% ± 3% vs 48% ± 1%, P<0.05). Analysis of the mesenteric lymph nodes and spleens on day +7 demonstrated significantly reduced expansion of donor T cells in R-Spo1 treated recipients in association with reduced serum levels of IFN-□ and TNF-□ on day +7 when compared to controls (Table). GVHD was severe in allogeneic controls, with 12.5% survival by day +40, whereas 62.5% of R-Spo1-treated animals survived this period (Table). Histopathologic examination of the small and large bowel and liver showed significantly reduced GVHD pathology in R-Spo1 treated animals than in controls (Table). A flowcytometric analysis of the spleen and thymus after BMT showed that administration of R-Spo1 did not impair donor cell engraftment and T and B cell immune reconstitution. We next evaluated the impact of R-Spo1 on graft-versus-leukemia (GVL) effects. BMT was performed similarly as above with the addition of 5 × 104 host-type P815 leukemia cells (H-2d). All recipients of T cell-depleted BM died from leukemia by day +20 after BMT, while no leukemia death was observed in R-Spo1 treated allogeneic animals. Overall, R-Spo1 treatment improved outcome of allogeneic BMT by reducing GVHD, while maintaining immune reconstitution and GVL effects. Thus, administration of R-Spo1 reduces the GI tract damage and suppresses donor T cell activation and systemic GVHD, supporting a hypothesis that the GI tract plays a major role in the amplification of systemic GVHD. Brief treatment with R-Spo1 may serve as an effective adjunct to clinical regimens of GVHD prophylaxis.
Pathology Scores Group Survivals on day+40 (%) Small bowel Large bowel Liver INF □ (ng/ml) TNF □ (pg/ml) TCD: T cell-depleted BMT, +T: T cell-repleted BMT, ND: not detected Data are expressed as mean ± SD. *P<0.01 vs control, **P<0.05 vs control TCD diluent 100 2.4± 0.9 3.5± 1.0 0.3± 0.3 ND ND +T diluent 12.5 8.3± 2.7 7.3± 1.9 2.0± 0.8 6.0 ± 2.4 103.7 ± 9.9 +T R-Spo1 62.5* 3.4±1.9** 3.9± 0.3** 0.8± 0.7** 2.3 ± 1.5** 55.4 ± 6.6**
The Wnt agonist R-spondin1 regulates systemic graft-versus-host disease by protecting intestinal stem cells
