Abstract
Chronic graft-versus-host disease (cGvHD) is the major source of late phase morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Humanized acute GvHD (aGvHD) in vivo models using NOD-SCID il2rγ-/- (NSG) mice are well described and are important tools for investigating pathogenicity of human cells in vivo. However, there have been only few reported humanized cGvHD mouse models. We evaluated if prolonged inflammation driven by low dose G-CSF-mobilized human PBMCs (G-hPBMCs) would lead to cGvHD following cyclophosphamide (CTX) administration and total body irradiation (TBI) in NSG mice. Engraftment was assessed in peripheral blood (PB) and in specific target organs by either flow cytometry or immunohistochemistry (IHC). Tissue samples were harvested 56 days post transplantation and were evaluated by a pathologist. Some mice were kept for up to 84 days to evaluate the degree of fibrosis. Mice that received CTX at 20mg/kg did not show aGvHD with stable expansion of human CD45+ CD3+ T-cells in PB (mean; 5.8 to 23.2%). The pathology and fibrosis scores in the lung and the liver were significantly increased with aggregation of T-cells and hCD68+ macrophages. There was a correlation between liver pathology score and the percentage of hCD68+ cells, suggesting the role of macrophage in fibrogenesis in NSG mice. In order to study long-term survival, 6/9 mice who survived more than 56 days showed increased fibrosis in the lung and liver at the endpoint, which suggests the infiltrating hCD68+ macrophages may be pathogenic. It was shown that the combination of CTX and TBI with a low number of G-hPBMCs (1x106) leads to chronic lung and liver inflammation driven by a high infiltration of human macrophage and mature human T cells from the graft, resulting in fibrosis of lung and liver in NSG mice. In conclusion this model may serve as an important pre-clinical model to further current understanding of the roles of human macrophages in cGvHD.
Highlights
Allogeneic hematopoietic stem cell transplantation is widely used for the treatment of hematological malignancies and other disorders including immune deficiencies, inborn errors of metabolism and hemoglobinopathies
In order to increase the possibility of development of Chronic Graft-versus-Host Disease (GvHD) (cGvHD), G-hPBMCs were applied as the donor source because of the known high risk of leading to cGvHD in humans[18]
To determine the required number of G-hPBMCs to give rise to acute GvHD (aGvHD) in NSG mice, mice were infused with G-hPBMCs on day 0 at either 20x106, 10x106, 5x106 or 1x106 cells/mouse following total body irradiation (TBI) (200cGy)
Summary
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is widely used for the treatment of hematological malignancies and other disorders including immune deficiencies, inborn errors of metabolism and hemoglobinopathies. Graft-versus-Host Disease (GvHD) is the major source of morbidity and mortality following allo-HSCT. GvHD is typically classified as either acute or chronic largely depending on the length of time before disease onset and/or clinical manifestations[1]. Chronic GvHD (cGvHD) occurs in 40%-70% of allo-HSCT patients. CGvHD presents with autoimmune-like and fibrotic symptoms, and B cell activation appears to be involved in this process[3,4]. Corticosteroids are used as the standard treatment for cGvHD with limited success. At this point, there are no effective second line therapies for cGvHD[5]
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