Clinical Study On The Prevention Of GVHD By The Application Of The Low-dose Cyclophosphamide And Umbilical Cord Blood Mesenchymal Stem Cells After SAA Peripheral Blood Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation(allo-HSCT)is the most important treatment for the severe aplastic anemia(SAA)which is a serious bone marrow failure disease.Bone marrow(BM)is considered to be the preferred graft for allo-HSCT in the treatment of SAA due to the lower incidence of graft-versus-host-disease(GVHD),but the collection of BM stem cell not only increases the pain of donors also increases the financial burden of the patients,so its application is limited.Peripheral blood stem cells(PBSCs)are simple and convenient to collect,but PBSCs transplantation has a high rate of incidence of GVHD.However,umbilical cord blood mesenchymal stem cells(UC-MSCs)can reduce the rate of incidence of GVHD for their unique immunomodulatory effects,which can make up this deficiency.Our center has previously achieved a certain effect on SAA by adopting UC-MSCs combined with PBSCs,but GVHD is still poorly controlled after transplantation.High-dose post-transplantation cyclophosphamide(PT-Cy)can reduce the rate of incidence of GVHD,but it will affect hematopoietic implantation and immune recovery to some extent,increasing the risk of infection.Thus,this study aims to provide a new idea and direction for the treatment of SAA by assessing the clinical efficacy and safety of the application of the low-dose cyclophosphamide and umbilical cord blood mesenchymal stem cells after SAA peripheral blood stem cell transplantation.ObjectiveTo explore the clinical efficacy and safety of the application of the low-dose cyclophosphamide and umbilical cord blood mesenchymal stem cells after SAA peripheral blood stem cell transplantation.MethodsRetrospective analysis of clinical data of 22 SAA patients who underwent allo-HSCT treatment from October 2017 to December 2018 in the hematopoietic stem cell transplantation at the Affiliated Tumor Hospital of Zhengzhou University.There were 13 males(59.1%)and 9 females(40.9%)with a median age of 16(3 to 31)years.There is 1 case(4.5%)with very severe aplastic anemia(VSAA),9 cases(41%)of SAA-I and 12 cases(54.5%)of SAA-II,of which SAA-II with paroxysmal nocturnal hemoglobin Urinary(PNH)clones were in 2 patients.Eight patients were transplanted with siblings,and 14 patients were transplanted with alternative donors(4 cases in unrelated donors and 10 cases in haploid transplantation).The pretreatment is fludarabine(FLu)+cyclophosphamide(CTX)+rabbit anti-human anti-thymocyte immunoglobulin(ATG)/anti-human T cell immunoglobulin(ALG)±low dose total body irradiation(TBI)±busulfan(BU)±melphalan(Mel).GVHD prophylaxis was conducted by a reduction of PT-Cy+cyclosporine A(CsA)±mycophenolate mofetil(MMF).At the same time,we also have some treatments of prevention and support for other transplant-related complications.All of these 22patients accepted low-dose CTX and UC-MSCs after transplantation of PBSCs for the first time.Two patients underwent secondary UC-MSCs combined with PBSCs and BM after the first implantation failure.The median number of the infusion of peripheral blood mononuclear cells(MNC)during transplantation was 16.27×10~8/kg(8.42×10~8/kg~28.71×10~8/kg),and the median number of the infusion of CD34+cells was 8.58×10~6/Kg(2.4×10~6/kg~19.45×10~6/kg).The amount of the infusion of UC-MSCs was calculated according to 1×10~6/kg.We observe the hematopoietic reconstitution,the incidence of GVHD and other transplant-related complications,and overall rate of survival(OS),and compare with the results of previous traditional transplantation.At the same time,we also analyze the clinical efficacy and factors that may affect OS of patients.Results1 Hematopoietic reconstitutionTwenty patients were successfully reconstituted with hematopoietic reconstitution.Two patients failed because of grafting rejection(GR).However,the hematopoietic reconstruction was successful after secondary transplantation.The numbers of all patients undergoing is 24,and the hematopoietic reconstitution rate was 90.9%(20/22).The median time of neutrophil and platelet implantation in the evaluable patients was 11(10~15)d and 12(9~17)d,respectively.2 The occurrence of GVHDThe rate of the incidences of acute GVHD(aGVHD),chronic GVHD(cGVHD),and GR were 27.3%(6/22),4.5%(1/22),and 9.1%(2/22)respectively.The incidence rate of II-IV degree aGVHD was 18.2%(4/22).3 Other transplant-related complicationsThe pulmonary infection rate was 40.9%(9/22),the rate of the incidence of oral mucositis was 36.4%(8/22),and the cytomegalovirus(CMV)infection rate was36.4%(8/22).The incidence rate of hemorrhagic cystitis(HC)was 18.2%(4/22),the incidence rate of renal dysfunction was 18.2%(4/22),the Epstein-barr virus(EBV)infection rate was 4.5%(1/22),the bloodstream infection rate was 9.1%.(2/22),intestinal infection rate was 4.5%(1/22),skin soft tissue infection rate was 4.5%(1/22),and the urinary tract infection rate was 4.5%(1/22).The incidence rate of posterior reversible encephalopathy syndrome(PRES)was 4.5%(1/22),the incidence rate of gastrointestinal bleeding was 4.5%(1/22),and the rate incidence of transplant-associated thrombotic microangiopathy(TA-TMA)was 4.5%(1/22).There were no hepatic venous occlusive disease(HVOD)and BK virus(BKV)infection in all patients.4 Follow-up resultsBy March 1,2019,the median follow-up time was 11.8(3~17)months for all patients,with 2 patients dying and the remaining 20 patients surviving well.Univariate analysis showed that II-IV degree aGVHD was a factor affecting the OS of patients.Conclusions1 The choice of PBSCs as grafts in this study avoids the pain suffered by donors when collecting BM and reduces the economic burden of patients.2 UC-MSCs have weak poisoning side effects in allo-HSCT treatment of SAA.The patients are well tolerated.UC-MSCs are safe and effective,which can not only reduce the incidence rate of GVHD,but also promote the implantation of hematopoietic stem cells.3 Reducing PT-Cy can effectively reduce the rate of the incidence of GVHD by PBSCs,does not affect the speed and quality of stem cell implantation,and can reduce the application of other immune suppressants and the infection rate.4 Overall,the application of low-dose CTX and UC-MSCs after SAA peripheral blood stem cell transplantation can not only improve the survival rate of patients,but also reduce the incidence rate of transplant-related complications such as GVHD.It can be used as a new idea for allo-HSCT in the treatment of SAA.It has certain value of clinical application and development prospects.