| Background:Bone defects and non-unions caused by trauma,tumor resection,and congenital deformities are critical challenges in the field of orthopedic and craniomaxillofacial surgeries.Autografts,allografts and biomedical materials are three major ways for bone reconstruction.Although autografts are considered as the "gold standard",its remarkable drawbacks including impairment of the donor site and limited availability restrict its clinical use.Allografts are also credited for favorable clinical results,but its drawbacks including immunogenic and disease transmission are also annoying.According to recent research,biphasic ceramic phosphate(BCP)is a promising,efficient material in bone regeneration,and it has already been used in prosthodontics and for the non-weight-bearing bones.However,the molecular mechanisms of BCP-induced bone formation are still not understood definitely.Previous studies found that the efficacy of osteoinduction induced by BCP was associated with its components and microstructure.The Notch signaling pathway plays an important role in bone formation and skeletal remodeling.Previous studies detected high level of Jaggedl(one of the ligands of the Notch signaling pathway)in the fracture site and found the osteogenic effect of Notch signaling pathway.Meanwhile,Notch signaling pathway related components could be detected in cells cultured on the biomaterials.The above-mentioned studies indicated that the Notch signaling pathway not only regulate the healing of fracture,but also play a potential role in the biomaterial induced bone reconstruction.However,the implications of Notch signaling in the BCP-induced bone formation is still unknown.Thus,we made a hypothesis that the osteoinductive potential of BCP was achieved through up-or down-regulating of the Notch signaling pathway.A thorough understanding of the molecular mechanism of BCP induced bone formation is important for the refinement of biomaterials design,shortening treatment timeframe,and offering new strategies for clinical use.Objective:To increase the efficacy of bone formation,manufacturing a new BCP with high porosity using mechanical mixing method and H2O2 foaming method;Evaluate the biocompatibility of the BCP,and discover the implications of Notch signaling in the BCP-induced bone formation.Methods:60 wt%Hydroxyapatite and 40 wt%β-tricalcium phosphate were prepared and mixed together,and then sintered at 1,100℃ for 3 hours.The pores were created through H2O2 foaming method.X-ray,scanning electron microscope and mercury injection apparatus were used to assess pertinent physicochemical parameters.By coculturing the bone marrow derived stem cells(BMSCs)with BCP,the compatibility of BCP was assessed by the cell morphology observation and cell proliferation viability.The osteoinduction of BCP was evaluated through the alkaline phosphate activity assay and ectopic bone formation.To study the implications of Notch signaling in the BCP-induced bone formation,a specific inhibitor of Notch signaling pathway,RO4929097,was used to culture BMSCs in vitro,and the intramuscularly ectopic implantation models of Beagle dogs were also used.Results:1.BCP ceramic discs and granules with macropore size measuring 380±50 μm,overall porosity measuring 70.8%and specific weight measuring 0.970 g/cm3 were successfully manufactured.2.BCP ceramics had favorable biocompatibility.When coculturing with BMSCs with BCP ceramics,BMSCs secreted more ALP which indicated its osteogenic differentiation.In Beagle ectopic bone formation model,at 12 weeks,77±11%of the macropores could detect new formed bone/osteoid tissues,and the volume was 71±14%.3.BCP ceramics with or without Notch signaling inhibitor RO4929097 were cocultured with bone marrow-derived stem cells in vitro,and the intramuscularly ectopic implantation models of Beagle dogs were used.At 8 weeks,both the percentage and volume of newly formed bone was significantly reduced in the BCP+RO4929097 group compared with the BCP group.However,at 12 weeks,there was no significant difference between them.Both the in vitro and in vivo results indicated that the Notch signaling pathway illustrated positively influence to ectopic bone formation by promoting BMSCs to differentiate toward osteoblasts at early stages,but had no favorable effect at late stages.Several signaling pathways are involved in the BCP-induced bone formation,the interaction between the Notch and other signaling pathways still needs further study.Conclusion1.BCP is a high biocompatible,efficient biomedical material for bone formation.2.BCP can positively promote BMSCs to differentiate towards osteoblasts.3.The Notch signaling pathway plays a positive role in bone formation induced by BCP at early stages. |
