Dual Regulation Of The Osteogenic Microenvironment By A Novel Endogenous Fibrin Hydrogel For Bone Regeneration

Background and Objective:Oral and maxillofacial bone defects due to tumor,trauma,inflammation and congenital diseases have been a challenge for clinical treatment.Various meansincluding autologous bone,allogeneic bone and synthetic bone graft materials have been used in current studies of oral and maxillofacial bone regeneration.Autologous bone grafting is considered the gold standard for repairing bone defects,but its use is limited by limited sources,the need for secondary surgery,chronic pain,and complications in the donor area.In addition,allogeneic bone may transmit disease,while synthetic bone graft materials lack osteogenic induction.Therefore,the use of bone tissue engineering to repair bone defects has become a hot research topic in recent years.Tissue engineering techniques promote new bone formation by loading seed cells and bioactive factors on scaffold materials.However,exogenous growth factors have limited their application in tissue engineering due to high cost,poor safety and unpredictable effects.Due to the absence of these drawbacks,human autologous blood products have achieved good results when applied to repair maxillofacial bone defects.Evidence has shown that autologous blood-derived protein scaffolds such as Platelet-Rich Plasma（PRP）,Platelet-Rich Fibrin（PRF）,and Concentrated Growth Factors（CGF）have significant bone regeneration promoting effects and are useful in bone tissue engineering.However,autologous hematopoietic protein scaffolds have a promising application in bone tissue engineering.However,autologous blood-derived protein scaffolds also have some disadvantages,such as poor mechanical properties and rapid release of growth factors,which can lead to poor results when used alone in bone tissue engineering.Therefore,this study was devoted to develop a new autologous hematogenous protein scaffold that can adapt to the local structural and mechanical environment and slow release of growth factors.Methods:1.SiO₂nanofibers were prepared by electrostatic spinning technique,homogenized and modified with polydopamine（PDA）on the surface.The PDA@SiO₂-i PRF hydrogel was prepared with the formation of fibrin network.2.The structural and mechanical properties of SiO₂nanofibers and PDA@SiO₂-i PRF hydrogels were characterized using scanning electron microscopy,Fourier infrared spectroscopy,XPS elemental analysis,and rheometry.3.Elisa kit was used to study the release pattern of growth factors in i PRF and PDA@SiO₂-i PRF.4.CCK-8,live-dead staining,q RT-PCR,immunofluorescence staining,alkaline phosphatase and alizarin red qualitative and quantitative assays were used to study the effects of PDA@SiO₂-i PRF hydrogels on the proliferation and differentiation of bone marrow mesenchymal stem cells.5.In vivo experiments to study the effect of PDA@SiO₂-i PRF hydrogel to promote the repair of cranial defects in rats.Results:In the present study,we prepared a composite hydrogel by combining polydopamine（PDA）-modified SiO₂nanofibers with i PRF.The PDA component in PDA@SiO₂-i PRF acts as the linker between the fibrin networks of i PRF and homogenized SiO₂nanofibers for mechanical property enhancement,overcoming the dilemma associated with insufficient stiffness.Moreover,PDA@SiO₂-i PRF hydrogels are injectable during the gel formation period of one minute,which is suitable for the filling of irregular bone defects in a minimally invasive manner.From the biophysical level,PDA@SiO₂-i PRF with enhanced mechanical property can withstand the external loading and maintaining the space for bone regeneration in bone defects.Particularly,the reinforced structure of hybrid hydrogels provides them with bone extracellular matrix（ECM）-like activities to stimulate osteoblasts differentiation via Yes-associated protein（YAP）signaling pathway.From the biochemical level,the PDA components in PDA@SiO₂-i PRF hinder the fast degradation of i PRF and make them release autologous growth factors in a sustained manner to avoid the initial burst release,providing continuous promotional effects for osteogenesis.Such reinforced hydrogels significantly facilitate osteoblast differentiation and bone regeneration both in vitro and in vivo with high efficacy...