Effect And Mechanism Of HO-1 High Expression On Attenuating Acute Graft-versus-host Disease

Objective: This study was aimed to explore the relationship between expression of HO-1 mRNA and severity of aGVHD who received allo-HSCT.To study on the effect of HO-1 high expression on attenuating acute graft-versus-host disease and its mechanism through lentivirus gene-transfer.It could provide experimental evidences and new ideas for treatment or prevetion of aGVHD.Methods: This study was divided into two parts: patients and experimental animals.For patients,bone marrow and peripheral blood mononuclear cells of 42 grade I-IV patients and 20 none-GVHD patients were collected at 30 days after allo-HSCT,30 healthy donors were collected for control.The expression of HO-1 mRNA in bone marrow and peripheral blood mononuclear cells were detected by Realtime PCR.For experimental animals,C57BL/6 as donor mice,BALB/c as recipient mice,mice model of allogeneic transplantation were established.HO-1-gene-modified MSCs(MSC-HO-1-ZsGreen)or empty vector transduced MSCs(MSC-ZsGreen)were injected into the recipient mice 24 hours after allogeneic transplantation.We added the mice which accepted bone marrow cell transplantation only as control.Engraftment of MSCs of MSC-HO-1-ZsGreen and MSC-ZsGreen were examined by immunohistochemical staining.Destruction of target organs organization structure in each group mice was observed by pathological section and H&E-stain.TH17 cells and Treg cells in splenic and lymph node tissues of each group mice was detected by Flow cytometry.Meanwhile,the expression levels of ROR-?t,IL-17 A mRNA and Foxp3 in the splenic tissue in each group was analyzed by Realtime PCR.Results:We found that expressions of HO-1 mRNA in the bone marrow and peripheral blood mononuclear cells of allo-HSCT recipients who had subsequent non-grade I aGVHD and healthy donors were significantly higher than those in patients with Grade III-IVaGVHD.There were no significance between healthy donors and grade III-IV aGVHD patients.At 14 days after transplantation,HO-1 expressions in damaged target organs of mice that received HO-1-gene-modified MSCs(MSC-HO-1-Zs Green)were considerably higher than those in the MSC-ZsGreen group.MSCs with HO-1overexpression significantly enhanced the survival of recipients,reduced weight loss,and attenuated clinical and pathological scores of mice.Flow cytometry revealed a higher expression of Treg cells and a lower expression of TH17 cells in splenic and lymph node tissues in MSC-HO-1-Zs Green mice,as compared to that in the others.This was further substantiated by lower expression levels of ROR-?t and IL-17 A mRNA,and higher levels of Foxp3 mRNA in the splenic tissue of mice with enhanced HO-1 expression.Conclusion: Our results indicate that high expression of HO-1 mRNA in bone marrow and peripheral blood mononuclear cells may indicate a less severe aGVHD.High expression of HO-1 may reduce the severity of aGVHD by regulation of the TH17/Treg balance.