Recombinant Human Thrombopoietin Reduces the Risk of Acute Graft-Versus-Host-Disease and Its Mechanisms

Objective: Acute graft-versus-host-disease (aGVHD) is an important complication that is observed after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We aimed to evaluate the effects of recombinant human thrombopoietin (TPO; rhTPO) on aGVHD using clinical data, mice models, and peripheral blood mononuclear cells (PBMCs). Methods: From 2016 to 2018, 162 cases of allo-HSCT in our hospital were recruited in this study. The correlation between TPO use and aGVHD was analyzed. After a GVHD model was constructed in Balb-C mice, HE staining was performed to compare the pathophysiological changes of the liver, intestine, lung, kidney, and other organs of the mice. The levels of lymphocyte subsets and cytokines in the mice spleens in the different groups were detected. PBMCs were isolated from the peripheral blood of healthy persons and patients with allo-HSCT via Ficoll gradient centrifugation and treated with different concentrations of rhTPO. The proliferation of PBMCs was detected via the CCK8 method, and the differentiation of PBMCs into lymphocytes was analyzed via flow cytometry. Results: 1) The occurrence of aGVHD was observed in 10 patients (47.6%) in the control group and 27 (23.1%) in the treatment group. The difference between the two groups was statistically significant (χ2=5.465, P=0.019). 2) The results of the aGVHD mice proved that rhTPO decreased the damage to the mouse liver, intestine, lung, and kidney tissues. In addition, splenic cell subpopulations CD4+cells, CD8+cells, T cells, and NK cells increased in the GVHD group but decreased due to rhTPO (P<0.05). After rhTPO treament, T cell subpopulations Th2 and Th17 cells decreased in the GVHD mice (P<0.05). Cytokines CD8+IL-17A+ and CD8+IL-4+IFNγ showed no difference between the four groups (P>0.05). Compared to GVHD mice, CD8+IL-4+ decreased in TPO-treated GVHD mice, and the effect of TPO at a high dose was more significant (P<0.05). 3) The results of the PMBCs suggested that a low dose of rhTPO could promote the proliferation of PMBCs, while a high dose could inhibit the proliferation. rhTPO promoted the differentiation of PBMCs into the CD3-PC5 subset. Conclusions: Altogether, this study indicates that rhTPO reduces the risk of aGVHD and is a protective factor against the occurrence of aGVHD.