Early Lung Injury Is Associated with Acute Graft-Versus-Host Disease in Murine Following Allogeneic hematopoietic Stem Cell Transplantation

Objective: To explore the mechanism of early lung injury and it’s association with acute graft-versus-host disease (aGVHD) in murine after allogeneic hematopoietic stem cell transplantation (allo-HSCT).

Methods: Established acute GVHD model of C57BL/6→BALB/c mice. Chest computed tomography (CT) scans were dynamically performed in recipient mice after transplant. Histopathology and the level of cytokines including TNFα and IFNγ in lung tissue were kinetically detected by Linchip system.

Results: The incidence of aGVHD in allogeneic transplant (C) group was 100%, but those were 0% in simple irradiation

• and syngeneic transplant

• group.

CT scans indicated that lungs of mice in three groups were normal at day +3 and +7 after transplant. CT scans revealed that two of ten mice had bilateral lung diffuse infiltrate on day +12 post-transplant (on the brink of death) in A group and six of ten mice had bilateral lung diffuse infiltrate on day +14 (3 day after acute GVHD occurring) in C group, and normal on day +12 and +14 in B group. Histopathology of lung in three groups were similar, consisting of slight edema in epithelial cells,scattered lymphocytes and macrophages infiltration on day +3 post-transplant. In A group, Histopathology of lung showed edema and hyperplasia of epithelial cells, widened alveolar interval at day +7, and epithelial cells necrosis, alveolar space hemorrhage, protein leakage, and local consolidation of lungs at day +12 after transplant. Histopathology of B group showed slight edema of epithelial cells on day +7 post-transplant, which were slighter than that on day +3, and virtually normal on day +14. And in C group, histopathology was characterized by significant expansion and congestion of capillaries, pulmonary interval widened and lymphocytes infiltration on day +7, and acute pneumonitis was present involving both the interstitial and alveolar spaces, the alveolar infiltrate was composed of macrophages, lymphocytes, epithelial cells and scattered polymorphonuclear cells within a fibrin matrix, and dense mononuclear cell infiltrates were observed around both pulmonary vessel and bronchioles on posttransplant day +14. The levels of TNFα in lung tissues were 48.167±7.679, 48.667±9.223 and 46.167±4.792 pg/ml at day +3 (P =0.830), and 34.000±2.608, 45.500±6.899 and 62.500±6.235 pg/ml at day +7 after transplant in A, B and C group (P=0.000), respectively. On day +14 post-transplant, the levels of TNFα in B group were lower than those in C group (51.167±4.262 vs 63.667±12.242 pg/ml, P =0.04). The levels of IFNγ were 319.833±12.481, 364.000±66.798 and 382.000±29.435 pg/ml on day +3 (P=0.062), and 397.500±37.914, 380.500±33.243 and 399.833±29.968 pg/ml on day +7 post-transplant (P=0.571) in A, B and C group, respectively. The levels of IFNγ in B group were higher than those in C group (405.167±23.928 vs 309.333±52.099 pg/ml, P=0.005).

Conclusions: Acute GVHD is the main reason of early non-infectious lung injury. T lymphocytes and TNFα might play a fundamental role in the pathogenesis of acute GVHD-induced lung injury. The decreasing of IFNγ in lung tissues after allo-HSCT might be associated with pulmonary fibrosis in late non-infectious pulmonary complications.