| OBJECTIVE: Mesenchymal stem cells （MSCs） have a mesodermaldifferentiation potential, are an important cell source for the regeneration ofdamaged tisses and have been widely used to help bone repair.Hypoxia-inducible factor1alpha （HIF-1α） can improve the osteogenic andangiogenic potential of MSCs simultaneously. This study explored whetherHIF-1α transduction could enhance bone repair capacity of MSCs throughimproving their osteogenic differentiation and angiogenic activity, and whethertransplantation of HIF-1α transgenic bone marrow-derived stem cells（BMSCs） could promote the repair of the necrotic tissues of the femoralhead in a rabbit model with early-stage corticosteroid-induced osteonecrosis ofthe femoral head. This study also explored whether dimethyloxaloylglycine（DMOG） could enhance the osteogenic differentiation and angiogenicactivities of adipose-derived stem cells （ASCs） by increasing HIF-1αexpression in cells, and bone repair capacity of DMOG-treated ASCs fortreating the critical-sized calvarial defects in rats. Besides, we tried to useDMOG to enhance the angiogenic activity of BMSCs, thereby improve theangiogenesis of tissue-engineered bone.METHODS: The first part: After transduction with HIF-1α gene, qRT-PCR,ELISA, ALP activity and alizarin red-S staining was carried out to detect theosteogenic differentiation capacity and angiogenic capacity of BMSCs. HIF-1αtransgenic BMSCs were transplanted into the necrotic area of the femoralhead to improve the bone regeneration. MicroCT and histological examinationwere then performed to assess the bone regenetaion and the new bloodvessels formation in the necrotic area. The second part: After ASCs were treated with different concentrations of DMOG, Western Blotting, qRT-PCR,ELISA, ALP activity and alizarin red-S staining were performed to detect theosteogenic differentiation capacity and angiogenic capacity of ASCs.DMOG-treated ASCs were transplanted to treat the critical-sized calvarialdefects of rats, the bone regenetaion and the new blood vessels formation inthe defect area were assessed. The third part: After BMSCs were treated withDMOG, qRT-PCR and ELISA were used to detect the expression and secretionof angiogenic factors. Tissue-engineered bone constructed DMOG-treatedBMSCs and β-TCP were implanted to treat the critical-sized calvarial defectsof rats, the bone regenetaion and the new blood vessels formation in the defectarea were then evaluated.RESULTS: The first part: After transduction with HIF-1α gene, BMSCssecreted more VEGF than normal BMSCs, and had enhanced osteogenicdifferentiation capacity in vitro. Transplantation of HIF-1α transgenic BMSCsobviously increased the bone regeneration of the necrotic area of the femoralhead. The volume and number of newly formed blood vessels weresignificantly enhanced in the necrotic area of the femoral head compared tothose of other groups. The second part: DMOG could obviously increaseVEGF expression and secretion of ASCs by activating the expression ofHIF-1α in vitro. DMOG also could increase mRNA expression of RUNX-2,OCN and ALP, and improve osteogenic differentiation capacity of ASCs. Ratswith critical-sized calvarial defects treated with DMOG-treated ASCs had morebone regeneration and new blood vessels formation than the control groups.The third part: After treated with DMOG, the expression and secretion of VEGF,SDF1, bFGF and PLGF in BMSCs were obviously increased. DMOG-treatedBMSCs had an enhanced angiogenic activity in tissue-engineered bone.CONCLUTIONS: HIF-1α transgenic BMSCs have enhanced bone repaircapacity in vitro and in vivo, improved its effect in treating early-stagecorticosteroid-induced osteonecrosis of the femoral head in rabbit model.DMOG improved the osteogenic and angiogenic activity of ASCs by activating the expression of HIF-1α in cells, thereby improved bone repair capacity ofASCs for treating rat critical-sized calvarial defects. DMOG could improve theangiogenesis of tissue-engineered bone by enhancing the angiogenic activityof BMSCs. |
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