To Explore The Pathogenesis Of Hematopoietic Stem Cell Transplantation Associated Thrombotic Microangiopathy

Background and Objective:An uncommon but devastating consequence of HSCT is transplantation-associated thrombotic microangiopathy(TA-TMA). The incidence of TA-TMA ranges from 0.5%to 76%, it is a multifactorial disease where generalized endothelial dysfunction leads to microangiopathic hemolytic anemia, intravascular platelet activation,which can contribute to end-organ injury,especially involving the kidney.The risk factors for HSCT-associated TMA include chemotherapy, radiation, graft versus host disease, unrelated donor, calcineurin inhibitors, and infections.The mechanisms of endothelial injury in TA-TMA are not completely understood.previously studies showed that the Pathophysiologic of TA-TMA is associated with deficiency of ADAMTS-13 activity. Now, complement alternative pathway dysregulation may be involved in the pathogenesis of post-HSCT TMA.Due to unclear diagnosis,the mortality rate of TA-TMA is 60–90% despite treatment.What’s more,it unusually confused with severe GVHD,infections and other thrombosis complications after HSCT.So diagnosis and intervention as early as possible is of great importance.This study aimed to investigate the changes of ADAMTS-13 activity,VWF antigen, VWF activity, C3 b and C5 b in patients with TA-TMA,and evaluate their clinical significance.Methods:A total of patients who were received HSCT in our hospital were enrolled in this study.The patients including14 cases of TA-TMA as experimental group,and other groups as control,which consist of 20 cases of infection,20 cases of GVHD,11 cases in VOD group and 20 patients without complication.The sodium citrate anticoagulated plasma of these patients were collected before pretreatment and after transplantation.Fluorescence resonance energy transfer substrate VWF73(FRETS-VWF73) assay was used to detect the plasma ADAMTS-13 activity while VWF activity was measured by VWF colledge banding activity,at the same time,VWF antigen was detected by LIA, and the changes of C3 b,C5b were inspected in ELISA.Results:(1)ADAMTS-13 activity in cases of VOD patients before pretreatment(63.72±14.38)% was significantly higher than it when VOD occurred(34.09±9.00)%,(P<0.05),what’s more,ADAMTS-13 activity was lower than other groups before pretreatment and in event of VOD(P<0.05).There is no difference between before pretreatment and complication occurred in patients with other groups including TA-TMA,infections,GVHD and no complications(P>0.05).(2) In a total of 85 patients who recived HSCT,when VOD occurred,v WF antigen in 11 cases of VOD group was highly increased( 218.57±24.30) % vs(168.75±9.34)%,(P<0.05).At the same time, v WF antigen in patients of VOD has no different from other groups before HSCT,(P>0.05),however,it was significantly lower than other groups in an event of an break,( P<0.05).Nonetheless, v WF activity has no obviously difference between case group and control group in front hematopoietic stem cell transplantation pretreatment(P>0.05);while v WF activity in the presence of VOD was significantly higher than that of other groups,(P<0.05). But v WF activity has no difference in groups of TA-TMA,GVHD and no complications after HSCT.(3) UL-v WF multimer was found in blood samples of TA-TMA and VOD,the distribution of infection group,GVHD group and uncomplication group are roughly same as normal control.(4) The complement C3 b in a total of patients who underwent HSCT preconditioning(198.46±14.78) ng/ml is significantly higher than normal control(85.02±8.50)ng/ml,(P<0.05). When complications of TA-TMA and GVHD occurred, The complement C3 b was clearly increase,respectively( 480.70±66.76) ng/ml vs(150.27±29.66)ng/ml,(298.50±32.06)ng/ml vs(199.68±26.92)ng/ml,(P<0.05).The content of C3 b elevated more obviously than other groups including GVHD.(4)Compared with normal control, patients who before preprocessing have no distinct difference in the content of complement C5 b,respectively(584.84±19.91)ng/ml vs(682.48±19.54)ng/ml,(P>0.05). But the complement C5 b in cases of TA-TMA patients(1059.49±85.57)ng/ml was higher than that of before preprocessing(653.19±44.91)ng/ml,(P<0.05);while also higher than that of other groups.Conclusions:(1)Patients in VOD group have lower ADAMTS-13 activity than other groups before preprocessing. When VOD occurred,ADAMST-13 average activity significantly reduced,at the same time, v WF antigen and v WF activity had increased apparently and there is no difference between other groups except VOD group. UL-VWF is related to lower ADAMTS-13 in VOD group,which showed that ADAMTS-13 is a plasma protease specifically cleaving von Willebrand factor.Meanwhile,there are some UL-VWF multimer also in TA-TMA patients,so it may still exist other enzyme that cleaves UL-VWF multimer.(2)TA-TMA is a serious complications after HSCT with a high mortality rate,At present,the diagnostic criteria of TA-TMA is a challenging question. When the complication occuered,C3 b content in TA- TMA and GVHD complications were higher than other groups, but TA- TMA group increased more obviously, significantly higher than that of GVHD group, which could prompt complement C3 b levels is a predictor of vascular lesions.(3)The content of C5 b in TA- TMA was significantly higher in patients with pretreatment group, and other various complications before precontioning.It can be a specificity index for early detection of TA – TMA.