Preparation And Performance Of Bioactive Inorganic Materials For Osteochondral Defect Regeneration

Osteoarthritis is a common disease which will result in articular cartilage damage in clinic.As cartilage lacks innate healing response,thus cartilage regeneration remains significant challenge.Moreover,the cartilage lesion always induces the subchondral bone to be developed into osteochondral defects.Since cartilage and subchondral bone possess different physiological functions,multi-layered biomaterials were fabricated to imitate the physiology structure of osteochondral complex in traditional ways.However,the combination of two layers in multi-layered scaffolds is insufficient.Hence,it remains a challenge to develop a monophasic scaffold that can biologically meet the needs for simultaneously reconstructing both of cartilage and subchondral bone within osteochondral defects.Currently,bioactive inorganic materials are mainly applied to the regeneration of hard tissues,such as bone and teeth.Nonetheless,there is few research about bioactive inorganic materials for the repair and reconstruction of cartilage.In this dissertation,the strategies by incorporating bioactive ions into bioactive ceramics,and a 3D printing technology was used to fabricate a monophasic porous scaffold for simultaneously regenerating both of cartilage and subchondral bone.The obtained bioactive ceramic scaffolds were used to study the bone/cartilage-related biological response in vitro and in vivo.Furthermore,the underlying mechanism of bioactive ions for protecting cartilage from OA and stimulating osteochondral reconstruction was investigated.Hence,the incooperation of bioactive ions into a monophasic inorganic bioceramic scaffold may represent a smart strategy for OA treatments and bone/cartilage regeneration simultaneously.The main results are described as follows:1.Based on the positive effect of Manganese(Mn)on supporting cartilage and subchondral bone development,and the good biocompatibility of ?-tricacium phosphate(?-TCP),Mn-TCP bioactive ceramics were synthesized by a coprecipitation method and Mn-TCP scaffolds were fabricated via a 3D printing technology.The incorporation of Mn into ?-TCP lowers the lattices parameters and crystallization temperatures,but improves the compressive strength and degradation of the scaffolds.The in vitro study showed that the ionic products from Mn-TCP significantly stimulated the proliferation and supported the muturation of chondrocytes through activating HIF pathway.The Mn2+ and Ca2+ ions from Mn-TCP may have a collective effect on the proliferation and osteogenic differentiation of rabbit mesenchymal stem cells(r BMSCs).Mn2+ ions protected chondrocytes from the inflammatory osteoarthritis environment by inhibiting metabolic activity.The in vivo study demonstrated that Mn-TCP scaffolds possessed bilineage physiological functions for simultaneously regenerating both of cartilage and subchondral bone.2.Based on the stimulated effect of single bioactive ions on osteochondral defect regeneration,the positive effect of multi-bioactive ions for cartilage and subchondral bone regeneration was further investigated.In view of the osteoinduction of Lithium(Li)and calsium silicate(CS),pure crystalline phase Li2Ca2Si2O7(LCS)bioactive ceramiscs were synthesized by a sol-gel method,and LCS scaffolds with designed morphology and uniform macropores were obtained via a 3D printing technology.The in vitro study indicated that LCS extracts significantly stimulated the proliferation and maturation of chondrocytes,as well as promoted the osteogenic differentiation of r BMSCs.Further study showed that Li and Si together promoted chondrocytes maturation via activating HIF pathway,as well as cooperatively protected chondrocytes from OA environment through inhibiting the hedgehog pathway and decresing the metabolic activity in chondrocytes.In an osteochondral defect model in New Zealand white rabbits' s knee,LCS scaffolds exhibted bilineage bioactivities for both of cartilage and subchondral bone regeneration,which represents an intelligent strategy for OA therapy by harnessing the cooperative effect of multi-bioactive ions in one single scaffold.3.Based on cooperative effect of multi-bioactive ions in one single scaffold on osteochondral defect regeneration,the stimulated effect of multi-bioactive ions in monophasic scaffold for the interface between cartilage and subchondral bone reconstruction was further investigated.Given the essential role of strotium(Sr)and silicon(Si)in cartilage and subchondral bone tissue,a solid phase method was used to synthesize Sr5(PO4)2Si O4(SPS)bioactive ceramics,and a 3D printing technology was used to fabricate porous SPS scaffolds which possessed highly controlled uniform structure.The in vitro study demonstrated that the ionic products from SPS bioceramics significantly stimulated the proliferation of chondrocytes and elevated chondrocyte specific genes and proteins expression.Further study indicated that Sr and Si synergistically promoted chondrocytes proliferation and supported chondrocyte maturation through activating HIF pathway,as well as protected chondrocytes from OA environment via activating autophagy and inhibiting the hedgehog pathway in chondrocytes.The vivo study suggested that SPS scaffolds can achieve osteochondral defect reconstruction and well reconstruct the complex interface between cartilage and subchondral bone.In summary,bioactive ions were incorporated into inorganic bioceramics and their positive effect for osteochondral defect regeneration was further studied.Combining the essential role of bioactive ions for osteochondral reconstruction with 3D printing technology,the bioceramic scaffolds with highly controlled macropores and morphology,and bilineage bioactivities for both of cartilage and subchondral bone regeneration were developed.Furthermore,the obtained porous bioceramic scaffolds significantly improved both of cartilage and subchondral bone regeneration simultaneously,which offers a smart strategy for the regeneration of osteochondral defects,especially for cartilage lesion regeneration.