Ruxolitinib protects skin stem cells and maintains skin homeostasis in murine graft-versus-host disease

[Janus kinase inhibitors for skin disorders]

Immune factors such as interferon‑ɣ and interleukin 4 belong to the group of cytokines that are dependent on type I/II receptors for their signal transmission. Upon activation, these receptors transmit their signal to the cell nucleus and, thus, modulate gene transcription via a signaling cascade consisting of Janus kinases (JAK). This family of four kinases (JAK 1, JAK 2, JAK 3, and tyrosine kinase 2 (TYK2)) subsequently activate members of the signal transducer and activator of transcription (STAT). This finding turned the JAK/STAT signaling pathway into a pharmacological target for the treatment of inflammatory diseases in which cytokines using type I/II receptors play a pathogenic role. In 2018, the European Medicines Agency (EMA) approved tofacitinib for the treatment of psoriatic arthritis. This was the first approval of a JAK/STAT pathway inhibitor for patients treated by dermatologists and rheumatologists. Since then, several new JAK inhibitors have been approved for dermatologic diseases such as atopic dermatitis, alopecia areata, vitiligo, and plaque-type psoriasis. In addition, JAK inhibitors are being investigated for the treatment of many other skin diseases. Thus, systemic JAK inhibitors complete the spectrum of immunotherapeutics with a broader immunological approach compared to monoclonal antibodies. The low molecular weight of JAK inhibitors enables the preparation of these drugs for both systemic and topical administration. Their utilization could represent a valuable alternative to topical steroids. The safety profile of JAK inhibitors must be taken into account. Possible long-term effects may become apparent in the next few years. This article describes both approved JAK inhibitors and relevant new JAK inhibitors that are promising candidates for approval as therapeutics in dermatology.

GVHD targets organoid-forming bile duct stem cells in a TGF-β-dependent manner

ABSTRACT

Graft-versus-host disease (GVHD) is a major life-threatening complication that occurs after allogeneic hematopoietic cell transplantation (HCT). Although adult tissue stem cells have been identified as targets of GVHD in the skin and gut, their role in hepatic GVHD is yet to be clarified. In the current study, we explored the fate of bile duct stem cells (BDSCs), capable of generating liver organoids in vitro, during hepatic GVHD after allogeneic HCT. We observed a significant expansion of biliary epithelial cells (BECs) on injury early after allogeneic HCT. Organoid-forming efficiency from the bile duct was also significantly increased early after allogeneic HCT. Subsequently, the organoid-forming efficiency from bile ducts was markedly decreased in association with the reduction of BECs and the elevation of plasma concentrations of bilirubin, suggesting that GVHD targets BDSCs and impairs the resilience of BECs. The growth of liver organoids in the presence of liver-infiltrating mononuclear cells from allogeneic recipients, but not from syngeneic recipients, was significantly reduced in a transforming growth factor-β (TGF-β)-dependent manner. Administration of SB-431542, an inhibitor of TGF-β signaling, from day 14 to day 28, protected organoid-forming BDSCs against GVHD and mitigated biliary dysfunction after allogeneic HCT, suggesting that BDSCs are a promising therapeutic target for hepatic GVHD.

Decreasing the steroid rapidly may help to improve the clinical outcomes of patients with intestinal steroid-refractory acute graft-versus-host disease receiving basiliximab treatment

Intestinal steroid refractory acute graft-versus-host disease (SR-aGVHD) is the major cause of mortality in allogeneic hematopoietic stem cell transplantation (allo-HSCT). This retrospective cohort study aimed to identify the relationship between different steroid decreasing velocity and therapeutic response in patients with intestinal SR-aGVHD receiving basiliximab treatment, and also aimed to propose a reasonable steroid decreasing regimen for these patients. The median time for steroid dose decreasing to the 50% of initial dose and decreasing to the low-dose steroid for patients achieving ORR was 5 days and 12 days, respectively, which was both shorter than patients without achieving ORR. The ORR, NRM and survival in rapid and medium steroid decreasing group were all better than slow group. The cumulative incidence of ORR at any time was 90.4%, 78.1% and 62.3%, respectively, in rapid, medium, and slow group. The cumulative incidence of NRM at 1 year after basiliximab treatment was 18.7% (95% CI 11.3%-26.1%), 22.8% (95% CI 14.2%-31.4%) and 32.8% (95% CI 24.1%-41.5%), respectively, in rapid, medium, and slow group. The probability of OS at 1 year after basiliximab treatment was 76.9% (95% CI 68.9%-84.9%), 72.7% (95% CI 63.7%-81.7%), and 62.3% (95% CI 53.5%-71.1%), respectively, in rapid, medium, and slow group. Hence, it was helpful to decrease steroid to the 50% of initial dose ≤ 5 days and to the low-dose steroid ≤ 12 days after basiliximab treatment for intestinal SR-aGVHD patients, which may also be the reasonable steroid decrease protocol for these patients.

R-Spondin1 protects gastric stem cells and mitigates gastric GVHD in allogeneic hematopoietic stem cell transplantation

ABSTRACT

Graft-versus-host disease (GVHD) is the major obstacle to performing allogeneic hematopoietic cell transplantation (allo-HCT). We and others have shown that intestinal stem cells are targeted in lower gastrointestinal GVHD. A leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5)-expressing gastric stem cells (GSCs) reside at the base of the gastric glands in mice. After experimental allo-HCT, Lgr5+ GSCs significantly decreased. Parietal cells, which underwent continuous renewal by GSCs, were injured in gastric GVHD, leading to failure of gastric acidification and aerobic bacterial overgrowth in the duodenum. Fate-mapping analysis demonstrated that administration of R-Spondin1 (R-Spo1) that binds to Lgr5 for 6 days in naïve mice significantly increased proliferating epithelial cells derived from Lgr5+ GSCs. R-Spo1 administered on days -3 to -1 and from days +1 to +3 of allo-HCT protected GSCs, leading to amelioration of gastric GVHD and restoration of gastric acidification, and suppression of aerobic bacterial overgrowth in the duodenum. In conclusion, Lgr5+ GSCs were targeted by gastric GVHD, resulting in disruption of the gastric homeostasis, whereas R-Spo1 protected Lgr5+ GSCs from GVHD and maintained homeostasis in the stomach.

Corticosteroids impair epithelial regeneration in immune-mediated intestinal damage

Corticosteroid treatment (CST) failure is associated with poor outcomes for patients with gastrointestinal (GI) graft-versus-host disease (GVHD). CST is intended to target the immune system, but the glucocorticoid receptor (GR) is widely expressed, including within the intestines, where its effects are poorly understood. Here, we report that corticosteroids (CS) directly targeted intestinal epithelium, potentially worsening immune-mediated GI damage. CS administered to mice in vivo and intestinal organoid cultures ex vivo reduced epithelial proliferation. Following irradiation, immediate CST mitigated GI damage but delayed treatment attenuated regeneration and exacerbated damage. In a murine steroid-refractory (SR) GVHD model, CST impaired epithelial regeneration, worsened crypt loss, and reduced intestinal stem cell (ISC) frequencies. CST also exacerbated immune-mediated damage in organoid cultures with SR, GR-deficient T cells or IFN-γ. These findings correlated with CS-dependent changes in apoptosis-related gene expression and STAT3-related epithelial proliferation. Conversely, IL-22 administration enhanced STAT3 activity and overcame CS-mediated attenuation of regeneration, reducing crypt loss and promoting ISC expansion in steroid-treated mice with GVHD. Therefore, CST has the potential to exacerbate GI damage if it fails to control the damage-inducing immune response, but this risk may be countered by strategies augmenting epithelial regeneration, thus providing a rationale for clinical approaches combining such tissue-targeted therapies with immunosuppression.

Chronic graft-versus-host disease. Part II: Disease activity grading and therapeutic management

Chronic graft-versus-host disease (cGVHD) is a major complication of allogeneic hematopoietic cell transplantation and a leading cause of long-term morbidity, nonrelapse mortality, and impaired health-related quality of life. The skin is commonly affected and presents heterogeneously, making the role of dermatologists critical in both diagnosis and treatment. In addition, new clinical classification and grading schemes inform treatment algorithms, which now include 3 Federal Drug Administration-approved therapies, and evolving transplant techniques are changing disease epidemiology. Part I reviews the epidemiology, pathogenesis, clinical manifestations, and diagnosis of cGVHD. Part II discusses disease grading and therapeutic management.

Separation of GVL from GVHD -location, location, location

Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for various hematologic malignancies. However, alloimmune response is a double-edged sword that mediates both beneficial graft-versus-leukemia (GVL) effects and harmful graft-versus-host disease (GVHD). Separation of GVL effects from GVHD has been a topic of intense research to improve transplant outcomes, but reliable clinical strategies have not yet been established. Target tissues of acute GVHD are the skin, liver, and intestine, while leukemic stem cells reside in the bone marrow. Tissue specific effector T-cell migration is determined by a combination of inflammatory and chemotactic signals that interact with specific receptors on T cells. Specific inhibition of donor T cell migration to GVHD target tissues while preserving migration to the bone marrow may represent a novel strategy to separate GVL from GVHD. Furthermore, tissue specific GVHD therapy, promoting tissue tolerance, and targeting of the tumor immune microenvironment may also help to separate GVHD and GVL.

Double-edged sword of JAK/STAT signaling pathway in viral infections: novel insights into virotherapy

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) is an intricate signaling cascade composed of various cytokines, interferons (IFN, growth factors, and other molecules. This pathway provides a delicate mechanism through which extracellular factors adjust gene expression, thereby acting as a substantial basis for environmental signals to influence cell growth and differentiation. The interactions between the JAK/STAT cascade and antiviral IFNs are critical to the host's immune response against viral microorganisms. Recently, with the emergence of therapeutic classes that target JAKs, the significance of this  cascade has been recognized in an unprecedented way. Despite the functions of the JAK/STAT pathway in adjusting immune responses against viral pathogens, a vast body of evidence proposes the role of this cascade in the replication and pathogenesis of viral pathogens. In this article, we review the structure of the JAK/STAT signaling cascade and its role in immuno-inflammatory responses. We also highlight the paradoxical effects of this pathway in the pathogenesis of viral infections. Video Abstract.

Combined treatment of graft versus host disease using donor regulatory T cells and ruxolitinib

Donor derived regulatory T lymphocytes and the JAK1/2 kinase inhibitor ruxolitinib are currently being evaluated as therapeutic options in the treatment of chronic graft versus host disease (cGvHD). In this work, we aimed to determine if the combined use of both agents can exert a synergistic effect in the treatment of GvHD. For this purpose, we studied the effect of this combination both in vitro and in a GvHD mouse model. Our results show that ruxolitinib favors the ratio of thymic regulatory T cells to conventional T cells in culture, without affecting the suppressive capacity of these Treg. The combination of ruxolitinib with Treg showed a higher efficacy as compared to each single treatment alone in our GvHD mouse model in terms of GvHD incidence, severity and survival without hampering graft versus leukemia effect. This beneficial effect correlated with the detection in the bone marrow of recipient mice of the infused donor allogeneic Treg after the adoptive transfer.

CpG-Activated Regulatory B-Cell Progenitors Alleviate Murine Graft-Versus-Host-Disease

Development of Graft Versus Host Disease (GVHD) represents a major impediment in allogeneic hematopoietic stem cell transplantation (HSCT). The observation that the presence of bone marrow and circulating hematogones correlated with reduced GVHD risks prompted us to evaluate whether B-cell progenitors, which provide protection in various autoimmune disease models following activation with the TLR-9 agonist CpG (CpG-proBs), could likewise reduce this allogeneic disorder. In a murine model of GVHD that recapitulates an initial phase of acute GVHD followed by a phase of chronic sclerodermatous GVHD, we found that CpG-proBs, adoptively transferred during the initial phase of disease, reduced the diarrhea score and mostly prevented cutaneous fibrosis. Progenitors migrated to the draining lymph nodes and to the skin where they mainly differentiated into follicular B cells. CpG activation and IFN-γ expression were required for the protective effect, which resulted in reduced CD4+ T-cell-derived production of critical cytokines such as TGF-β, IL-13 and IL-21. Adoptive transfer of CpG-proBs increased the T follicular regulatory to T follicular helper (Tfr/Tfh) ratio. Moreover, CpG-proBs privileged the accumulation of IL-10-positive CD8+ T cells, B cells and dendritic cells in the skin. However, CpG-proBs did not improve survival. Altogether, our findings support the notion that adoptively transferred CpG-proBs exert immunomodulating effect that alleviates symptoms of GVHD but require additional anti-inflammatory strategy to improve survival.

Established and Emerging Treatments of Skin GvHD

Graft-versus-host disease (GvHD) of the skin is a severe allo-immune reaction and complication following allogeneic stem cell transplantation. Over the past years, intensive pre-clinical research has led to an improved understanding of the pathophysiology of acute and to a lesser extend chronic GvHD. This has translated into the approval of several new agents for the treatment of both forms of GvHD. This review summarizes the most recent advances in underlying pathomechanisms, clinical trials and newly approved agents for GvHD, with a special focus on skin involvement.

Anti-thymocyte globulin could potentially overcome an adverse effect of acute GVHD in matched-related PBSCT

BACKGROUND

Previous Japanese studies have shown that bone marrow transplantation (BMT) is associated with a better survival compared with peripheral blood stem cell transplantation (PBSCT) from matched related donors (MRDs). PBSCT recipients showed a higher incidence of severe graft-versus-host disease (GVHD) and non-relapse mortality (NRM) than BMT recipients. In recent years, the efficacy and safety of anti-thymocyte globulin (ATG) for PBSCT recipients has been reported from around the world.

OBJECTIVE

We aimed to compare BMT and PBSCT to identify current improvements and unmet needs among PBSCT recipients from MRDs. Moreover, we evaluated the impact of ATG administration on the outcomes for PBSCT recipients.

STUDY DESIGN

We retrospectively analyzed patients aged 16 years or older with acute leukemia, myelodysplastic syndrome, or chronic myeloid leukemia who received their first BMT or PBSCT from MRDs between 2009 and 2018 in Japan.

RESULTS

In total, 3599 transplantations were performed (BMT, 1218; PBSCT without ATG [PBSCT-ATG(-)], 2288; and PBSCT with ATG [PBSCT-ATG(+)], 93). The PBSCT-ATG(-) group had a higher NRM rate (hazard ratio [HR], 1.30; 95% confidence interval [CI], 1.08-1.57; p = 0.005) and lower overall survival (OS) rate (HR, 1.16; 95% CI, 1.04-1.30; p = 0.011) than the BMT group. Furthermore, the PBSCT-ATG(-) group had a higher incidence of grade III-IV, stage 2-4 gut, high-risk, and steroid-refractory acute GVHD than the BMT group. Acute GVHDs had a negative impact on NRM and OS rates. PBSCT-ATG(-) was also associated with a higher risk of chronic GVHD (HR: 1.89; 95% CI: 1.24-1.57; p < 0.001) and extensive chronic GVHD (HR: 1.44; 95% CI: 1.23-1.68; p < 0.001). The incidence of acute GVHD, chronic GVHD, and NRM and chronic GVHD-free relapse-free survival rates were comparable between the PBSCT-ATG(+) and BMT groups. The OS rate of patients with acute GVHD in the three donor groups was similar. Patients treated with reduced-intensity conditioning in the PBSCT-ATG(+) group had a higher relapse rate and lower OS rate than those in the BMT group.

CONCLUSIONS

In this Japanese cohort, standard calcineurin inhibitor-based GVHD prophylaxis was not sufficient for PBSCT recipients from MRDs because of the high incidence of severe acute GVHD. Moreover, prophylactic ATG was found to be a promising strategy against GVHD.

N-carboxymethyl chitosan/sodium alginate composite hydrogel loading plasmid DNA as a promising gene activated matrix for in-situ burn wound treatment

Improving the degree of vascularization through the regulation of wound microenvironment is crucial for wound repair. Gene activated matrix (GAM) technology provides a new approach for skin regeneration. It is a local gene delivery system that can not only maintain a moist environment, but also increase the concentration of local active factors. For this purpose, we fabricated the mVEGF165/TGF-β₁ gene-loaded N-carboxymethyl chitosan/sodium alginate hydrogel and studied its effect on promoting deep second degree burn wound repair. The average diameter of the hydrogel pores was 100 μm and the porosity was calculated as 50.9%. SEM and CLSM images showed that the hydrogel was suitable for cell adhesion and growth. The NS-GAM could maintain continuous expression for at least 9 days in vitro, showing long-term gene release and expression effect. Deep second-degree burn wound model was made on the backs of Wistar rats to evaluate the healing effect. The wounds were healed by day 22 in NS-GAM group with the prolonged high expression of VEGF and TGF-β₁ protein. A high degree of neovascularization and high expression level of CD34 were observed in NS-GAM group in 21 days. The histological results showed that NS-GAM had good tissue safety and could effectively promote epithelialization and collagen regeneration. These results indicated that the NS-GAM could be applied as a promising local gene delivery system for the repair of deep second-degree burn wounds.

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The plasmids loaded in NS-GAM can achieve efficient gene delivery and expression in vitro and in vivo.

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The NS-GAM showed long-term controlled release function of the plasmids.

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The NS-GAM played a significant effect on neovascularization by means of gene delivery.

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The NS-GAM could achieve efficient in situ repair on deep second degree burn wounds.

Novel Insights Into the Mechanism of GVHD-Induced Tissue Damage

Prophylaxis for and treatment of graft-versus-host disease (GVHD) are essential for successful allogeneic hematopoietic stem cell transplantation (allo-SCT) and mainly consist of immunosuppressants such as calcineurin inhibitors. However, profound immunosuppression can lead to tumor relapse and infectious complications, which emphasizes the necessity of developing novel management strategies for GVHD. Emerging evidence has revealed that tissue-specific mechanisms maintaining tissue homeostasis and promoting tissue tolerance to combat GVHD are damaged after allo-SCT, resulting in exacerbation and treatment refractoriness of GVHD. In the gastrointestinal tract, epithelial regeneration derived from intestinal stem cells (ISCs), a microenvironment that maintains healthy gut microbiota, and physical and chemical mucosal barrier functions against pathogens are damaged by conditioning regimens and/or GVHD. The administration of growth factors for cells that maintain intestinal homeostasis, such as interleukin-22 (IL-22) for ISCs, R-spondin 1 (R-Spo1) for ISCs and Paneth cells, and interleukin-25 (IL-25) for goblet cells, mitigates murine GVHD. In this review, we summarize recent advances in the understanding of GVHD-induced tissue damage and emerging strategies for the management of GVHD.

The Pathophysiology and Treatment of Graft-Versus-Host Disease: Lessons Learnt From Animal Models

Allogeneic hematopoietic cell transplantation (HCT) is a curative treatment for hematologic malignancies, bone marrow failure syndromes, and inherited immunodeficiencies and metabolic diseases. Graft-versus-host disease (GVHD) is the major life-threatening complication after allogeneic HCT. New insights into the pathophysiology of GVHD garnered from our understanding of the immunological pathways within animal models have been pivotal in driving new therapeutic paradigms in the clinic. Successful clinical translations include histocompatibility matching, GVHD prophylaxis using cyclosporine and methotrexate, posttransplant cyclophosphamide, and the use of broad kinase inhibitors that inhibit cytokine signaling (e.g. ruxolitinib). New approaches focus on naïve T cell depletion, targeted cytokine modulation and the inhibition of co-stimulation. This review highlights the use of animal transplantation models to guide new therapeutic principles.

Graft-versus-host disease: a disorder of tissue regeneration and repair

Regenerative failure at barrier surfaces and maladaptive repair leading to fibrosis are hallmarks of graft-versus-host disease (GVHD). Although immunosuppressive treatment can control inflammation, impaired tissue homeostasis leads to prolonged organ damage and impaired quality of life. In this Spotlight article, we review recent research that addresses the critical failures in tissue regeneration and repair that underpin treatment-resistant GVHD. We highlight current interventions designed to overcome these defects and provide our assessment of the future therapeutic landscape.

Ruxolitinib, a JAK1/JAK2 selective inhibitor, ameliorates acute and chronic steroid-refractory GvHD mouse models

Aim: Graft-versus-host disease (GvHD) is a major complication arising in patients undergoing allogenic hematopoietic stem cell transplantation. Material & methods: We tested ruxolitinib (a selective JAK1/2 inhibitor) efficacy in three different preclinical models of GvHD. Results: Ruxolitinib, at doses that mimic clinically achievable human JAK/signal transducers and activators of transcription target inhibition, significantly reduced alloreactive T-cell activation and infiltration in the lung and skin, leading to improved outcomes in two experimental models of steroid-refractory acute and chronic GvHD. Additionally, we describe a novel humanized GvHD model in which immunodeficient NOG animals are engineered to produce human IL-15 to facilitate enhanced T- and NK cell engraftment, leading to severe GvHD. Conclusion: Ruxolitinib treatment ameliorated disease symptoms resulting from targeted immune modulation via JAK/signal transducers and activators of transcription signaling inhibition.

A phase 1 trial of itacitinib, a selective JAK1 inhibitor, in patients with acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) following allogeneic hematopoietic cell transplantation (HCT) is a primary cause of nonrelapse mortality and a major barrier to successful transplant outcomes. Itacitinib is a Janus kinase (JAK)1-selective inhibitor that has demonstrated efficacy in preclinical models of aGVHD. We report results from the first registered study of a JAK inhibitor in patients with aGVHD. This was an open-label phase 1 study enrolling patients aged ≥18 years with first HCT from any source who developed grade IIB to IVD aGVHD. Patients with steroid-naive or steroid-refractory aGVHD were randomized 1:1 to itacitinib 200 mg or 300 mg once daily plus corticosteroids. The primary endpoint was safety and tolerability; day 28 overall response rate (ORR) was the main secondary endpoint. Twenty-nine patients (200 mg, n = 14; 300 mg, n = 15) received ≥1 dose of itacitinib and were included in safety and efficacy assessments. One dose-limiting toxicity was reported (grade 3 thrombocytopenia attributed to GVHD progression in a patient receiving 300 mg itacitinib with preexisting thrombocytopenia). The most common nonhematologic treatment-emergent adverse event was diarrhea (48.3%, n = 14); anemia occurred in 11 patients (38%). ORR on day 28 for all patients in the 200-mg and 300-mg groups was 78.6% and 66.7%, respectively. Day 28 ORR was 75.0% for patients with treatment-naive aGVHD and 70.6% in those with steroid-refractory aGVHD. All patients receiving itacitinib decreased corticosteroid use over time. In summary, itacitinib was well tolerated and demonstrated encouraging efficacy in patients with steroid-naive or steroid-refractory aGVHD, warranting continued clinical investigations. This trial was registered at www.clinicaltrials.gov as #NCT02614612.

PD-1 antibody and ruxolitinib enhances graft-versus-lymphoma effect without increasing acute graft-versus-host disease in mice

Boosting T cell immune response posttransplant with checkpoint inhibitors increases graft-versus-lymphoma (GVL) effects at the cost of increasing acute graft-versus-host disease (aGVHD). A combined targeted therapy is needed to decrease checkpoint inhibitors-induced aGVHD without impairing GVL. We studied whether this competition could be avoided by giving concurrent anti-PD-1 antibody and ruxolitinib in allotransplant mouse models in which recipients were challenged with A20 or EL4 lymphoma cells. Given alone the PD-1 antibody increased GVL but did not improve survival of recipients challenged with A20 cells because of increased deaths from aGVHD. Adding ruxolitinib decreased levels of effector T cells and related cytokines. Tbx21^- T cells had higher PD-1 levels compared with Tbx21⁺ T cells. Ruxolitinib increased PD-1 levels on donor T cells by suppressing Tbx21 expression. Ruxolitinib increased apoptosis of T cells which was reversed by the PD-1 antibody. PD-1 antibody preserved expression of granzyme B and cytotoxicity of T cells which were decreased by ruxolitinib. The net result of combined therapy was increased GVL, no increase in aGVHD and increased survival. The combined therapy improved survival of recipients challenged by A20 cells which expressed high level of PD-L1, but not EL4 cells which do not express PD-L1.

Graft-versus-host disease reduces lymph node display of tissue-restricted self-antigens and promotes autoimmunity

Acute graft-versus-host disease (GVHD) is initially triggered by alloreactive T cells, which damage peripheral tissues and lymphoid organs. Subsequent transition to chronic GVHD involves the emergence of autoimmunity, although the underlying mechanisms driving this process are unclear. Here, we tested the hypothesis that acute GVHD blocks peripheral tolerance of autoreactive T cells by impairing lymph node (LN) display of peripheral tissue–restricted antigens (PTAs). At the initiation of GVHD, LN fibroblastic reticular cells (FRCs) rapidly reduced expression of genes regulated by DEAF1, an autoimmune regulator-like transcription factor required for intranodal expression of PTAs. Subsequently, GVHD led to the selective elimination of the FRC population, and blocked the repair pathways required for its regeneration. We used a transgenic mouse model to show that the loss of presentation of an intestinal PTA by FRCs during GVHD resulted in the activation of autoaggressive T cells and gut injury. Finally, we show that FRCs normally expressed a unique PTA gene signature that was highly enriched for genes expressed in the target organs affected by chronic GVHD. In conclusion, acute GVHD damages and prevents repair of the FRC network, thus disabling an essential platform for purging autoreactive T cells from the repertoire.

Ruxolitinib for treatment of steroid-refractory graft-versus-host disease in adults: a systematic review and meta-analysis

Objectives: Authors assessed the impact of ruxolitinib (RUX) on steroid-refractory graft-versus-host disease (SR-GVHD) patients.Methods: Studies published before January 2019 were identified by electronic search of MEDLINE, EMBASE, Cochrane Library, Clinical Trials.Gov and Web of Science databases.Results: Sixteen cohort studies (414 adults) were included whose methodological quality ranged from poor to good. Pooled outcomes such as the response rates, steroid dose reduction, 1-year overall survival, overall infection, and grade 3 to 4 cytopenia were calculated separately for adults with steroid-refractory acute GVHD (aGVHD) and chronic GVHD (cGVHD). Further, the overall response rates were analyzed according to the affected organ. Adults with aGVHD as well as cGVHD showed high response with RUX, and steroid dose reduction was observed in both cases. Infection rates and cytopenia were important safety concerns for both aGVHD and cGVHD.Conclusion: Notwithstanding the need of randomized controlled trials to confirm the effect of RUX on SR-GVHD, response rates among adults with aGVHD and cGVHD seem to be high with the use of RUX as a salvage treatment, particularly in cases with gastrointestinal and cutaneous involvement. However, high rates of myelosuppression and infection remain a cause for concern regardless of aGVHD or cGVHD.

Janus Kinase Inhibition for Graft-Versus-Host Disease: Current Status and Future Prospects

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is a curative treatment for many hematological malignant and non-malignant diseases. A major complication of the procedure is the donor T-cell-mediated graft-versus-host disease (GvHD). GvHD accounts for about 10% of early mortality after transplantation. GVHD is also the major cause of morbidity and disability in the late follow-up phase of transplanted patients, mainly because of the low response to first-line steroids, and the lack of efficient second-line standard treatments. The increasing knowledge regarding GVHD pathogenesis provides new pharmacological targets, potentially exploitable in clinical practice, in order to prevent and treat this complication. This review provides a description of GVHD pathogenesis, with a focus on the central role of the Janus kinase-related mechanisms. The first inflammatory innate-immunity response is triggered by a JAK/STAT dependent pathway, and JAK inhibition impairs antigen-presenting cell differentiation and activation and downregulates the expression of signals for T-cell triggering. The chronic evolution of alloreactivity, characterized by the long-term maintenance of inflammation and fibrosis, is also dependent on JAK/STAT activation. Based on preclinical data, we reviewed the rationale behind the clinical use of JAK-inhibitors in GVHD, presenting available results of clinical trials and reports, and looked at future implementation of this new promising treatment approach.

Biology-driven developments in the therapy of acute graft-versus-host disease

Allogeneic hematopoietic cell transplantation is a potentially curative treatment of different hematological malignancies. A major life-threatening complication is acute graft-versus-host disease (GVHD), in particular when the disease becomes steroid refractory. Based on the detection of pathogenic cytokines, chemokines, and T-cell subsets in individuals developing GVHD or experimental GVHD models, different therapeutic strategies have been developed. A potential cause why targeting individual receptors can lack efficacy could be that multiple cytokines, danger signals, and chemokine that have redundant functions are released during GVHD. To overcome this redundancy, novel strategies that do not target individual surface molecules like chemokine receptors, integrins, and cytokine receptors, but instead inhibit signaling pathways downstream of these molecules, have been tested in preclinical GVHD models and are currently being tested in clinical GVHD trials. Another important development is tissue regenerative approaches that promote healing of GVHD-related tissue damage as well as strategies that rely on microbiota modifications. These approaches are promising because they act very differently from conventional immunosuppression, instead aiming at reinstalling tissue homeostasis and microbiome diversity. This review discusses major novel developments in GVHD therapy that are based on a better understanding of GVHD biology, the repurposing of novel kinase inhibitors, microbiome modification strategies, and tissue-regenerative approaches.

Unraveling the Mechanisms of Cutaneous Graft-Versus-Host Disease

The skin is the most common target organ affected by graft-versus-host disease (GVHD), with severity and response to therapy representing important predictors of patient survival. Although many of the initiating events in GVHD pathogenesis have been defined, less is known about why treatment resistance occurs or why there is often a permanent failure to restore tissue homeostasis. Emerging data suggest that the unique immune microenvironment in the skin is responsible for defining location- and context-specific mechanisms of injury that are distinct from those involved in other target organs. In this review, we address recent advances in our understanding of GVHD biology in the skin and outline the new research themes that will ultimately enable design of precision therapies.

The Critical Role of Inflammation in the Pathogenesis and Progression of Myeloid Malignancies

Hematopoietic stem cells (HSCs) maintain an organism's immune system for a lifetime, and derangements in HSC proliferation and differentiation result in hematologic malignancies. Chronic inflammation plays a contributory if not causal role in HSC dysfunction. Inflammation induces HSC exhaustion, which promotes the emergence of mutant clones that may be resistant to an inflammatory microenvironment; this likely promotes the onset of a myeloid hematologic malignancy. Inflammatory cytokines are characteristically high in patients with myeloid malignancies and are linked to disease initiation, symptom burden, disease progression, and worsened prognostic survival. This review will cover our current understanding of the role of inflammation in the initiation, progression, and complications of myeloid hematologic malignancies, drawing from clinical studies as well as murine models. We will also highlight inflammation as a therapeutic target in hematologic malignancies.