Research On Biological Characteristics Of Bone Marrow Mesenchymal Stem Cells And JAK2Mutation In Myeloproliferative Neoplasms

Mesenchymal stem cells （MSC） are important component of hematopoieticmicroenvironment, which have self renewal capacity and multiple differentiation potential.It has been found that MSC have complex relationship with tumor microenvironment,which have been involved in the generation and development of hematological disorders.However, the number of researches on myeloproliferative neoplasms (MPN) is limited.Moreover, MSC have characteristics of supporting hematopoiesis and immune regulation,which have been used as methods to improve hematopoietic reconstruction andprophylaxis/treatment of GVHD after hematopoietic stem cell transplantation (HSCT). Butno final conclusion has yet been reached on the origin of bone marrow MSC afterallo-HSCT.Part1Objective To study the biological characteristics of bone marrow MSC from MPNpatients and detect JAK2mutation in MSC from MPN patients. Methods We searched forthe JAK2V617F mutation and JAK2exon12mutation in70MPN patients’ blood/bonemarrow samples. We further isolated MSC and then characterized their phenotype,mesenchymal differentiation capacity, chromosome karyotype, the expression ofhematopoietic and immune molecules and existence of JAK2mutation. Results MSCderived from the patients were similar to healthy donors in morphology, surface antigen,differentiation ability and chromosome karyotype. Besides, MSC from the patient canexpress a variety of hematopoietic and immune molecules normally. We found38patients’blood/bone marrow samples harbored JAK2V617F mutation and identified3JAK2V617F-negative-patients’ samples existed JAK2exon12. Despite blood/bonemarrow samples carried JAK2mutation, we didn’t find any patients’ MSC harbored JAK2 mutation. Conclusion MSC from MPN patients had similar biological characteristics tohealthy donors. We demonstrated that MSC from MPN patients known to carry JAK2mutation in blood/bone marrow cells were not affected with the same mutation.Part2Objective To study the chimerism status of bone marrow MSC following allogeneichematopoietic stem cell transplantation (allo-HSCT). Methods Bone marrow mononuclearcells were isolated by Ficoll density gradient centrifugation from21patients followingallo-HSCT and healthy donors. After cultured for about25days, MSC surface makers, theability of trillineage differentiation were detected, moreover, chimerism status of MSCwere also evaluated by multiple short tandem repeat (STR) amplification usingfluorescence labeling polymerase chain reaction (PCR) combined with capillaryelectrophoresis. Results MSC derived from patients were similar to normal adult MSC inmorphology, surface and differentiation ability. When bone marrow/peripheral blood wascomplete chimerism, the results of STR-PCR showed that patients’ MSC donor chimerismwas (5.24±2.5)%. A patient following double-unit cord blood stem cell transplantation(DCBT) demonstrated complete donor chimerism, hematopoiesis in BM and PB were froma single unit cord blood (donor chimerism was96.4%and95.7%, respectively). But thepredominant cord blood chimerism of MSC was5.4%. Conclusion MSC were generallyfrom host following allo-HSCT. Sustained hematopoiesis was derived from a single unitcord blood following DCBT. The majority of MSC were origin from host tissue, mixedchimerism donor part of MSC stemed from the engrafted unit of cord blood.