Bone Morphogenetic Protein 9 Stimulates Callus Formation In Osteoporotic Rats Of Fracture Healing

Objective: Bone morphogenetic protein 9(BMP9)is one of the most potent factors in bone formation.Present study aimed to evaluate the osteogenic potential of BMP9 in vitro and in vivo,and the relationship of Single nucleotide polymorphisms(SNPs)and bone mineral density(BMD).Methods: Alkaline phosphatase(ALP)Assay Kit was used to stain and measure the ALP activity,and calcium mineral deposits were tested by Alizarin Red S staining.Expressions of BMP9,runt related transcription factor 2(Runx2),and type 1 collagen(COL-I)were detected in both in vitro and in vivo.The femoral bone mineral density was assessed for osteoporosis in ovariectomized rats.The open femora fracture was then created with gelatin sponges containing AdBMP9 implanted.The femora were harvested for radiographical,Micro-CT,biomechanical,and histological analysis 4-weeks later.Genetics and bio-information analysis methods: MMAP software,Haploview software,Genotyping using either the Affymetrix 500 k or Affymetrix v6.0 SNP chips,and bio-information databases.Results: BMP9 successfully increased ALP activity and induced mineralized nodules formation in BMSCs.BMP9 within gelatin sponges showed the stronger effects on microstructural parameters and biomechanical strength of the callus.It was also found to enhance the expression of Runx2 and COL1.AdBMP9 within gelatin sponges significantly promoted the callus formation,bone mass and strength in osteoporotic rat of femora fracture.We also found that PTH and BMP9 synergetically promotes the osteogenetic differentiation of BMSCs cells.We found SNPs around BMP9 gene region have no relation with BMD.We found SNPs around WISP1 gene region are significant associated with BMD.Conclusion: Results of this study suggested that BMP9 enhancing the callus formation and maintaining an early mechanical stability in osteoporotic rats of fracture healing makes it a possible attractive improvement for fracture healing.BMP9 and PTH have the synergistic effect on osteogenetic differentiation.SNPs around BMP9 gene region are not associated with BMD.SNPs around WISP1 gene region are significantly associated with BMD.