Mechanism Of Bone Marrow Failure Induced By Cytomegalovirus After Hematopoietic Stem Cell Transplantation

Background and ObjectivesHuman cytomegalovirus(HCMV)is a member of beta-herpesvirus characterized by a linear double-stranded DNA genome.Reactivation from latent CMV can lead to life-threatening complications in immunocompromised populations especially the receipts of allogeneic hematopoietic stem cell transplantation(allo-HSCT).CMV infection is closely related to bone marrow failure diseases after allo-HSCT,such as poor graft function(PGF),autoimmune hematological diseases(AHDs)and so on.CMV might indirectly inhibit hematopoiesis through antiviral drug toxicities or directly inhibit hematopoiesis by infecting the hematopoietic stem cells(HSCs)and their progenitors and stromal cells.Bone marrow(BM)is made up of HSCs,their progenitors and stromal cells.Interactions between hematopoietic stem and progenitor cells and the bone marrow stromal cells are important in maintaining normal hematopoiesis.BM-derived mesenchymal stem cells(BM-MSCs)and endothelial progenitor cells(BM-EPCs)are important components of stromal cells in BM microenvironment.They paly important role in supporting HSCs.However,how CMV causes dysfunction of BM stromal cells and the related mechanisms remain unclear.Based on the above scientific background,the purpose of this study was to investigate whether BM stromal cells,including BMMSCs and BM-EPCs,were the target cells for CMV infection.To analyze whether CMV infection would affect the number and function of BM-MSCs and BM-EPCs.To explore the mechanism of CMV infection affecting BM-MSCs and BM-EPCs.To reveal the risk factors of PGF and AHDs after allo-HSCT.MethodsBone marrow stromal cells including BM-MSCs and BM-EPCs were cultured in vitro and identified by flow cytometry and functional experiments.The expression ofCMV pp65 protein in the nucleus was detected by indirect immunofluorescence.The number and function of bone marrow stromal cells were detected by cell and colony count,enzyme labeling,flow cytometry,immunofluorescence,real-time quantitative polymerase chain reaction,protein immune imprinting,and non-contact co-culture experiments.The risk factors for the occurrence of PGF and AHDs after allo-HSCT were retrospectively analyzed.Results(1)CMV pp65 protein expression was detected in the primary BM-MSCs and BM-EPCs from patients with CMV viremia after allo-HSCT.BM-MSCs and BMEPCs which were infected in vitro with HCMV AD 169 strain also could express CMV pp65 protein.(2)After CMV infection,the proliferation capacity of BM-MSCs was decreased,the level of apoptosis was increased,the osteogenic ability was decreased,the adipogenic ability was enhanced,the transcription level of IL-6 and TGF-β1 was increased,the transcription level of SCF was decreased,and the ability to support CD34+ cells was decreased.(3)After CMV infection,the proliferation capacity of BM-EPCs was decreased,the level of apoptosis was increased,the reactive oxygen species was increased,the ability to form tubes and migrate was decreased,the transcription level of IL-6 and TGF-β1 was increased,the transcription level of SCF was decreased,and the ability to support CD34+cells was decreased.(4)Increased expression of phosphorylated p-38 MAPK protein was detected in CMV-infected BM-MSCs and BM-EPCs.Decreased phosphorylation of p-38 MAPK protein partially corrected CMV induced impairments of BM-MSCs and BM-EPCs.(5)Retrospective analysis of clinical data suggested that CMV reactivation and acute graft-versus-host disease(aGVHD)were risk factors for the occurrence of PGF after allo-HSCT.Haploidentical transplantation and chronic GVHD(cGVHD)were risk factors for AHDs after allo-HSCT.ConclusionsCMV could infect BM-MSCs and BM-EPCs and cause the quantitive and functional impairments.These impairments could be partially corrected through the downregulation of phosphorylation of p38 MAPK pathway.