Mast Cell Involvement in Fibrosis in Chronic Graft-Versus-Host Disease.

Allogeneic hematopoietic stem cell transplantation (HSCT) is most commonly a treatment for inborn defects of hematopoiesis or acute leukemias. Widespread use of HSCT, a potentially curative therapy, is hampered by onset of graft-versus-host disease (GVHD), classified as either acute or chronic GVHD. While the pathology of acute GVHD is better understood, factors driving GVHD at the cellular and molecular level are less clear. Mast cells are an arm of the immune system that are known for atopic disease. However, studies have demonstrated that they can play important roles in tissue homeostasis and wound healing, and mast cell dysregulation can lead to fibrotic disease. Interestingly, in chronic GVHD, aberrant wound healing mechanisms lead to pathological fibrosis, but the cellular etiology driving this is not well-understood, although some studies have implicated mast cells. Given this novel role, we here review the literature for studies of mast cell involvement in the context of chronic GVHD. While there are few publications on this topic, the papers excellently characterized a niche for mast cells in chronic GVHD. These findings may be extended to other fibrosing diseases in order to better target mast cells or their mediators for treatment of fibrotic disease.

Microbiome: An Emerging New Frontier in Graft-Versus-Host Disease.

Hematopoietic cell transplantation is an intensive therapy used to treat high-risk hematological malignant disorders and other life-threatening hematological and genetic diseases. Graft-versus-host disease (GVHD) presents a barrier to its wider application. A conditioning regimen and medications given to patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT) are capable of disturbing the homeostatic crosstalk between the microbiome and the host immune system and of leading to dysbiosis. Intestinal inflammation in the context of GVHD is associated with loss in microbial diversity that could serve as an independent predictor of mortality. Successful gastrointestinal decontamination using high doses of non-absorbable antibiotics likely affect allo-HCT outcomes leading to significantly less acute GVHD (aGVHD). Butyrate-producing Clostridia directly result in the increased presence of regulatory T cells in the gut, which are protective in GVHD development. Beyond the microbiome, Candida, a member of the mycobiome, colonization in the gut has been considered as a risk factor in pathophysiology of aGVHD and reduction in GVHD is observed with antifungal prophylaxis with fluconazole. Reduced number of goblet cells and Paneth cells have been shown to associate with GVHD and has a significant impact on the micro- and mycobiome density and their composition. Lower levels of 3-indoxyl sulfate at initial stages after allo-HCT are related with worse GVHD outcomes and increased mortality. Increased understanding of the vital role of the gut microbiome in GVHD can give directions to move the field towards the development of improved innovative approaches for preventing or treating GVHD following allo-HCT.

Myeloablative vs reduced-intensity conditioning allogeneic hematopoietic cell transplantation for chronic myeloid leukemia.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment of chronic myeloid leukemia (CML). Optimal conditioning intensity for allo-HCT for CML in the era of tyrosine kinase inhibitors (TKIs) is unknown. Using the Center for International Blood and Marrow Transplant Research database, we sought to determine whether reduced-intensity/nonmyeloablative conditioning (RIC) allo-HCT and myeloablative conditioning (MAC) result in similar outcomes in CML patients. We evaluated 1395 CML allo-HCT recipients between the ages of 18 and 60 years. The disease status at transplant was divided into the following categories: chronic phase 1, chronic phase 2 or greater, and accelerated phase. Patients in blast phase at transplant and alternative donor transplants were excluded. The primary outcome was overall survival (OS) after allo-HCT. MAC (n = 1204) and RIC allo-HCT recipients (n = 191) from 2007 to 2014 were included. Patient, disease, and transplantation characteristics were similar, with a few exceptions. Multivariable analysis showed no significant difference in OS between MAC and RIC groups. In addition, leukemia-free survival and nonrelapse mortality did not differ significantly between the 2 groups. Compared with MAC, the RIC group had a higher risk of early relapse after allo-HCT (hazard ratio [HR], 1.85; P = .001). The cumulative incidence of chronic graft-versus-host disease (cGVHD) was lower with RIC than with MAC (HR, 0.77; P = .02). RIC provides similar survival and lower cGVHD compared with MAC and therefore may be a reasonable alternative to MAC for CML patients in the TKI era.

The lung function score and its components as predictors of overall survival and chronic graft-vs-host disease after allogeneic stem cell transplantation.

AIM: To retrospectively assess if the modified lung function score (LFS) and/or its components, forced expiratory volume within the first second (FEV1) and diffusion capacity for carbon monoxide corrected for hemoglobin level (cDLCO), predict overall survival (OS) and chronic graft-vs-host-disease (cGvHD). METHODS: We evaluated 241 patients receiving allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the University of Regensburg Transplant Center between June 1998 and July 2005 in relation to their LFS, FEV1 and cDLCO, before and after HSCT. RESULTS: Decreased OS after allo-HSCT was related to decreased pre-transplantation values of FEV1<60% (P=0.040), cDLCO<50% of predicted value (P=0.025), and LFS≥III (P=0.037). It was also related to decreased FEV1 at 3 and 12 months after HSCT (P<0.001 and P=0.001, respectively) and increased LFS at 3 and 12 months after HSCT (P=.028 and P=0.002, respectively), but not to changes of cDLCO. A higher incidence of cGvHD was related to decreased FEV1 at 6, 12, and 18 months (P=0.069, P=0.054, and P=0.009, respectively) and increased LFS at 12 months (P=0.002), but not to changes in cDLCO. CONCLUSIONS: OS was related to both LFS and FEV1, but cGvHD had a stronger relation to FEV1 than to cDLCO or LFS. FEV1 alone offered more information on the outcome after allo-HSCT than LFS or cDLCO, suggesting limited value of LFS for the patients' assessment after allo-HSCT.

Subacute hepatic necrosis mimicking veno-occlusive disease in a patient with HFE H63D homozygosity after allogeneic hematopoietic cell transplantation with busulfan conditioning.

Busulfan is a commonly used chemotherapeutic agent in myeloablative conditioning regimens for allogeneic hematopoietic cell transplantation (allo-HCT). It has been associated with sinusoidal-obstructive syndrome(SOS) as a life-threatening complication of myeloablative allo-HCT, yet it has not been found to cause severe hepatocellular injury, even in cases of significant accidental overdose.We report the case of a 31-year-old male with a history of high-risk myelodysplastic syndrome transitioning to acute myeloid leukemia, who in complete remission underwent allo-HCT using myeloablative busulfan­fludarabine conditioning, and who developed hepatic failure. While he met clinical criteria for SOS and was treated with defibrotide,liver biopsy demonstrated severe subacute hepatic necrosis and lacked characteristics of SOS. Further evaluation revealed that the patient was homozygous for the HFE H63D gene mutation, associated with hereditary hemochromatosis.Both Busulfan and iron overload related to HFE H63D homozygosity can cause oxidative stress resulting in cellular injury, and the cumulative effects of these risk factors are possibly responsible for the severe hepatocellular injury in this case, making our patient the first-known case of subacute hepatic necrosis related to busulfan administration.