Biological Effects Of Human Hemangiopoietin(HAPO) On Bone Marrow Stromal Cells

This academic thesis has exhibited its essences of research onbiological characteristics of murine marrow-derived mesenchymal stemcells and bone marrow microenvironment, and biological effects ofrecombined human hemangiopoietin upon bone marrow stromal cells, as wellas the potential impact of stromal cells transduced with humanhemangiopoietin gene on in vitro hematopoiesis.Section 1. The aim of this section is to explore the biologicalcharacteristics and in vitro differentiation potential of murinemarrow-derived mesenchymal stem cells. The techniques for isolation ofmurine marrow-derived mesenchymal stem cells have been described, as wellas the methods to directing their differentiation into osteogenic,chondrogenic, and adipogenic lineages. Their characteristics regardingmorphology, surface marker profiles and growth kinetics have also beenexplored. These cells were positive for the surface markers CD29, CD38,CD44, and CD106, and exhibited a homogeneous, distinctive morphology, andwere shown to differentiate along osteogenic, chondrogenic, andadipogenic pathways. After the 8th passage, MSC had a markedly diminishproliferation rate.Section 2. The objective of this section is to survey the biologicaleffects of a novel cytokine, recombined human hemangiopoietin (rhHAPO),on bone marrow stromal cells. The biological effects of rhHAPO on theproliferartion of primary bone marrow stromal cells, the formulation offibroblast-colony-forming unit, and the regulation of cell adhesionmolecules on the stromal cell line HESS-5, have been explored by by Typanblue exclusion, MTT assay, colony assay and flow cytometry analysisrespectively. The expression of cytokine gene of HESS-5 cells has beendetermined by reverse transcription polymerase chain reaction (RT-PCR).The rhHAPO stimulated the proliferation of stromal cells by increasingtheir proportion of S-phase cells, and enhanced the total adhesive abilityby up-regulating the expression of adhesion molecules (VCAM and ICAM) onHESS-5 cells. However, HESS-5 cells expressed M-CSF and c-mpl genes, butnot HAPO or G-CSF gene. Section 3.and 4. In these two sections, the main subjects areconstructing the eukaryotic expression vector containing humanhemangiopoietin gene and expressing it in mouse bone marrow stromal cellline HESS-5, then supporting hematopoiesis in vitro with gene modifiedHESS-5 (HAPO-HESS-5). The PCR products of HAPO were digested with BamHâ… and BgI â…¡. Then the HAPO gene segment obtained was cloned intopIRES2-EGFP to construct recombinant eukaryotic expression vectorHAPO-pIRES2-EGFP. The recombinant vector was identified by enzymedigestion analysis, PCR, and sequencing. HESS-5 cells were transfectedby recombinant vector and positive clones were selected with G418. Theexpression of HAPO gene in the transformed cells was detected by studyingEGFP expression, RT-PCR, and Western blotting analysis. Support of humanhematopoiesis by HAPO-HESS-5 cells was evaluated in co-culture systemswith human CD34+ cells. Enzyme digestion analysis and sequencing showedthat target gene had been cloned into recombinant vector. The expressionof HAPO gene in the transformed stromal cells had been demonstrated byfluoro-microscopy and RT-PCR analysis. HAPO protein was also detected inthe supernatant of HAPO-HESS-5 by Western blotting analysis. As expected,stably transfected HAPO-HESS-5 cells significantly increased in bothrelative and absolute numbers of CD34+ cells after 7 days of culture. ThePKH26 study demonstrated that cell division and self-regeneration werepromoted faster in CD34+ cells cocultured with HAPO-HESS-5 cells than incells cocultured with vector-HESS-5 cells. The HAPO-HESS-5 cells alsosupported human hematopoiesis in vitro more efficiently than controlvector-HESS-5 cells. Conclusions and Perspectives: 1, The methodology for the culture and induced differentiation ofmouse mesenchymal stem cells, as well as a comprehensive understandingof their biology, will make it possible to the development of cellularand genetic therapy protocols in murine models, and provide newperspectives in the field of adult stem cells research. 2, The data suggest for the first time that rhHAPO is a novel growthfactor stimulating the proliferation and adhesion of stromal cells, andthat it may have a clinical potential in the reconstitution of bone marrowmicroenvironment as well as the homing of stem cells after hematopoieticstem cell transplantation. 3, The recombinant eukaryotic expression vector has been constructedand expressed successfully in the transformed cells. The HAPO-HESS-5cells support rapid generation of primitive progenitor cells and maintainreconstituting ability of hematopoietic stem cells in vitro. Therefore,it is possible to use the stromal cells expression HAPO gene as subsidiarycells in the hematopoietic stem cell transplantation.