Bone Morphogenetic Protein 1 And Dentin Matrix Protein1 Transduced Bone Marrow Stem Cells Promote The Osteogenesis And Osseointegration Of Maxillary Sinus Floor Elevation In Beagles

Objective Beta-tricalcium phosphate(β-TCP)has been successfully used in maxillary sinus floor augmentation(MSFA)as a commonly used bone replacement material in implantation surgeries of dental implants.However,this bone replacement material lacks osteogenic induction properties,which in turn leads to insufficient new bone formation and bone mineralization after implantation.In contrast,dentin matrix protein-1(DMP-1),which is pivotal in the process of jaw bone mineralization,can release a functional fragment DMP1-C through the hydrolysis of full-length DMP1,which plays an important role in bone formation and mineralization.In addition,bone morphogenetic protein-1(BMP-1)can regulate osteogenic mineralization by affecting the hydrolysis of DMP1.Based on the above mechanisms,the aim of this study is to investigate whether the functional fragment DMP1-C produced by the BMP1-stimulated effective hydrolysis of DMP1 could promote osteo-differentiation of bone marrow mesenchymal stem cells(BMSCs).This study further aims to explore the performance of the β-TCP scaffold that incorporates BMSCs with overexpressed BMP1 and DMP1 genes via lentiviral vector transduction in improving the mineralization and osteogenesis in MSFA of beagles.Methods BMSCs were transduced in vitro with lentivirus vectors that overexpress DMP1 gene(Lenti-DMP1),BMP1 gene(Lenti-BMP1),enhanced green fluorescent protein(Lenti-EGFP),enhanced red fluorescent protein(Lenti-mcherry)and enhanced blue fluorescent protein(Lenti-EBFP2).The BMSCs were then mixed withβ-TCP bone substitute material for subsequent maxillary sinus lifting surgery.Beagles underwent bilateral maxillary sinus floor augmentation(MSFA)and simultaneous implantation of four groups of materials:(1)Lenti-BMP1/EGFP+BMSCs+β-TCP,(2)Lenti-DMP1/mcherry+BMSCs+β-TCP,(3)Lenti-BMP1+DMP1/EBFP2+BMSCs+β-TCP and(4)β-TCP).Material 3 was set as the experimental group,while Materials 1,2 and 4 were set as the control groups.After 12 weeks of surgery,the maxillae of the beagles were removed,and each maxillary sinus sample was evaluated by X-ray imaging,micro-CT and histological analysis.The osteogenic and osseointegration performances of the four groups of different materials were then compared.Results Three months after the MSFA with simultaneous material implantation,the CT images clearly shows the maxillary sinus with good growth and healing,and no maxillary sinus perforation,inflammation,or mucosal hyperplasia was observed in each group.Compared with the other three control groups,the experimental group beagles implanted with Lenti-BMP1+DMP1/EBFP2-transduced BMSCs/β-TCP composite scaffold showed superior relative bone volume(BV/TV),bone trabecular thickness(Tb.Th),and bone trabecular number(Tb.N)in the maxillary sinus.Optical microscopy observation of the sample sections showed that there was also more mature bone tissue around the implant threads.Moreover,the implant osseointegration rate and bone area fraction were also higher in the experimental group compared with the control groups,while the volume of the remaining bone replacement material was smaller than that of the control groups,indicating a greater bone contact area,higher bone density,and better resorption of bone replacement material in the experimental group.Conclusion The results of this study show that the DMP1-C fragments generated by the BMP1-stimulated effective hydrolysis of DMP1 could promote osteo-differentiation of BMSCs.The mineralization and the osseointegration of the new bone tissue could thus be enhanced,and the osteogenesis of the MSFA with simultaneous implantation surgeries in beagles was also improved.