Complement Activation-mediated Endothelial Injury And Micro-thrombogenesis In Pathogenesis Of Thrombotic Microangiopathy After Allogeneic Stem-cell Transplantation

Transplantation associated-thrombotic microangiopathy(TA-TMA)is a severe disease after hematopoietic stem cell transplantation(HSCT).Previous studies showed that TATMA is related to complement activation.However,the pathogenesis of complement activation in TA-TMA is still unclear.We collected plasma samples of patients with TATMA and found that,unlike with classical thrombotic microangiopathy(TTP),ADAMTS13 level does not increase in patients with TA-TMA while plasma C3 b and sC5b-9 level in these patients significantly increased compared to patients with veno occlusive disease(VOD),graft-versus-host disease(GVHD),infection and non-complications both before and after HSCT.hypoxia-inducible factor-1α(HIF-1α)belongs to a family of oxygen-labile transcription factors,which is associated with injury,repair and regeneration of endothelial cells.Using Western Blot and enzyme-linked immuno sorbent assay(ELISA),we found that HIF-1α level in patients with TA-TMA increased compared to controls.Next,we constructed human umbilical vein endothelial cells(HUVECs)which overexpresses HIF-1α gene.Afterwards,we incubated HUVECs with plasma collected from healthy volunteers.We found that C3 level on surface of HIF-1α overexpression HUVECs increased compared to controls by Western Blot.We also used HIF-1α agonist IOX-2 and inhibitor PX-478 to regulate HIF-1α level in HUVECs,then we found increased C3 level by FACS,Western Blot and immunocytochemistry.Data also showed that HIF-1α agonist IOX-2 cloud induce injury and inhibits proliferation of HUVECs by CCK8 kits.Finally,we constructed HSCT mouse model and upregulated HIF-1α level by agonist DMOG through intraperitoneal injection.The platelet counts and hemoglobin level of DMOG mice decreased as well as LDH increased.We also found C4 d deposition and microthrombosis by immunehistofluorescence stain and hematoxylin-eosin staining.We concluded that HIF-1α may play an important role in pathogenesis of TA-TMA,and downregulating HIF-1α level could be a potential therapy for TA-TMA in the future.