Epithelial regeneration is critical for barrier maintenance and organ function after intestinal injury. The intestinal stem cell (ISC) niche provides Wnt, Notch, and epidermal growth factor (EGF) signals supporting Lgr5+ crypt base columnar ISCs for normal epithelial maintenance1,2. However, little is known about the regulation of the ISC compartment after tissue damage. Utilizing ex vivo organoid cultures, we provide evidence that innate lymphoid cells (ILCs), potent producers of Interleukin-22 (IL-22) after intestinal injury3,4, increased the growth of murine small intestine (SI) organoids in an IL-22-dependent fashion. Recombinant IL-22 directly targeted ISCs, augmenting the growth of both murine and human intestinal organoids, increasing proliferation, and promoting ISC expansion. IL-22 induced Stat3 phosphorylation in Lgr5+ ISCs, and Stat3 was critical for both organoid formation and IL-22-mediated regeneration. Treatment with IL-22 in vivo after murine allogeneic bone marrow transplantation (BMT) enhanced recovery of ISCs, increased epithelial regeneration, and reduced intestinal pathology and mortality from graft vs. host disease (GVHD). Atoh1-deficient organoid culture demonstrated that IL-22 induced epithelial regeneration independent of the Paneth cell niche. Our findings reveal a fundamental mechanism by which the immune system is able to support intestinal epithelium, activating ISCs to promote regeneration.

Despite the importance of intestinal stem cells (ISCs) for epithelial maintenance, there is limited understanding of how immune-mediated damage affects ISCs and their niche. We found that stem cell compartment injury is a shared feature of both alloreactive and autoreactive intestinal immunopathology, reducing ISCs and impairing their recovery in T cell–mediated injury models. Although imaging revealed few T cells near the stem cell compartment in healthy mice, donor T cells infiltrating the intestinal mucosa after allogeneic bone marrow transplantation (BMT) primarily localized to the crypt region lamina propria. Further modeling with ex vivo epithelial cultures indicated ISC depletion and impaired human as well as murine organoid survival upon coculture with activated T cells, and screening of effector pathways identified interferon-γ (IFNγ) as a principal mediator of ISC compartment damage. IFNγ induced JAK1- and STAT1-dependent toxicity, initiating a proapoptotic gene expression program and stem cell death. BMT with IFNγ–deficient donor T cells, with recipients lacking the IFNγ receptor (IFNγR) specifically in the intestinal epithelium, and with pharmacologic inhibition of JAK signaling all resulted in protection of the stem cell compartment. In addition, epithelial cultures with Paneth cell–deficient organoids, IFNγR-deficient Paneth cells, IFNγR–deficient ISCs, and purified stem cell colonies all indicated direct targeting of the ISCs that was not dependent on injury to the Paneth cell niche. Dysregulated T cell activation and IFNγ production are thus potent mediators of ISC injury, and blockade of JAK/STAT signaling within target tissue stem cells can prevent this T cell–mediated pathology.

Graft-versus-host disease (GVHD) and posttransplant immunodeficiency are frequently related complications of allogeneic hematopoietic transplantation. Alloreactive donor T cells can damage thymic epithelium, thus limiting new T-cell development. Although the thymus has a remarkable capacity to regenerate after injury, endogenous thymic regeneration is impaired in GVHD. The mechanisms leading to this regenerative failure are largely unknown. Here we demonstrate in experimental mouse models that GVHD results in depletion of intrathymic group 3 innate lymphoid cells (ILC3s) necessary for thymic regeneration. Loss of thymic ILC3s resulted in deficiency of intrathymic interleukin-22 (IL-22) compared with transplant recipients without GVHD, thereby inhibiting IL-22-mediated protection of thymic epithelial cells (TECs) and impairing recovery of thymopoiesis. Conversely, abrogating IL-21 receptor signaling in donor T cells and inhibiting the elimination of thymic ILCs improved thymopoiesis in an IL-22-dependent fashion. We found that the thymopoietic impairment in GVHD associated with loss of ILCs could be improved by restoration of IL-22 signaling. Despite uninhibited alloreactivity, exogenous IL-22 administration posttransplant resulted in increased recovery of thymopoiesis and development of new thymus-derived peripheral T cells. Our study highlights the role of innate immune function in thymic regeneration and restoration of adaptive immunity posttransplant. Manipulation of the ILC-IL-22-TEC axis may be useful for augmenting immune reconstitution after clinical hematopoietic transplantation and other settings of T-cell deficiency.

2016-11-02T18:49:00

55 years, range 4-72) with moderate-severe CGVHD following an allogeneic HCT for a primary hematologic malignancy. NIH consensus criteria (2015) were used for CGVHD grading. Patients were divided into 2 cohorts, a) those receiving an extended course of azithromycin (14 days) for CGVHD management (cohort 1, n=86) and b) those who did not (cohort 2, n=153). Patients in cohort 2 either did not receive any azithromycin (n=122) or had received an abbreviated (<14 day) course (n=31) of azithromycin post-HCT. For cohort 1, the median time to initiation of azithromycin therapy was 15 months post-HCT (range 3-68), with a 26 month median duration of azithromycin therapy (range 1-77). All patients in cohort 1 met NIH consensus criteria for BOS. Patients in cohort 2 did not exhibit BOS, but still met NIH criteria for moderatesevere CGVHD. Hematologic conditions included acute leukemia (n=139), MDS/MPD (n=44), malignant lymphomas (n=26), chronic leukemia (n=24), and multiple myeloma (n=6). Ninetyone patients exhibited moderate and 148 patients exhibited severe CGVHD. The two cohorts were balanced for CGVHD severity, with severe CGVHD noted in 69% and 63% of patients in cohorts 1 and 2 respectively. RESULTS: Decreased rates of relapse and improved survival were noted for patients treated with azithromycin for CGVHD. At 2 years, the cumulative incidence of relapse was 2% (95% CI:1-9%) for patients in cohort 1 vs 16% (95% CI: 11-23%) in cohort 2, p=0.001. Overall survival (2-year OS) in cohort 1 was 93% (95%CI: 88-99%) vs 78% (95% CI:72-85%) for cohort 2, p=0.003. Overall, 7 of 86 (8.1%) CGVHD patients treated with an extended course of azithromycin (cohort 1) have relapsed, the median time to relapse 876 days (range 379-1303) post-HCT. In comparison, 28 of 153 (18.3%) in cohort 2 have relapsed, a median 371 days (range 98-1252) post-HCT. CONCLUSION: The use of azithromycin for the management of moderate to severe CGVHD was not associated with an increased risk of relapse in patients undergoing HCT for a hematologic malignancy. Azithromycin therapy for patients with CGVHD should not be contra-indicated in this patient population.