| Backgrounds and Objectives:The consistently successful repair of articular cartilage defects is still a major andhot clinical challenge. Adult articular cartilage exhibits little capacity for intrinsic repair,and thus even minor injuries or lesions may lead to progressive damage and osteoarthriticjoint degeneration, resulting in significant pain and disability. In the past decades,considerable efforts have been made to propose experimental and clinical treatments forarticular cartilage defects. However, no treatment modality has so far proved to besuperior compared to the others, and the results of each technique demonstrate largevariances. In this study, the CaP materials with a nanospherical structure have beenprepared and blended with PLA to prepare a composite coating on porous Ta scaffold.The properties of physic-chemical, in-situ mineralization, in vitro cytotoxicity of the CaPcoated Ta scaffolds have been investigated. Furthermore, the effect of in vivo articularcartilage defect repair has also been investigated,using the composite material covered bythe periosteum. With this approach we explore the importance of the subchondral bonefor its role in the treatment of articular surface damage, and discussed the strategies forthe repair of cartilage defects that arise from or extend into the subchondral bone.Methods and results:This study consisted of two experimental parts. the CaP materials with ananospherical structure have been prepared using a co-precipitation method in thepresence of the block copolymer of polylactide–block–monomethoxy(polyethyleneglycol)(PLA mPEG). Then, the CaP has been blended with PLA to prepare a composite coatingon porous Ta scaffold. The properties of physic-chemical, in-situ mineralization, in vitrocytotoxicity of the CaP coated Ta scaffolds have been investigated. The samples werecharaterized in many aspects, using Transmission electron microscopy (TEM),Dynamiclight scattering (DLS), X ray powder diffraction (XRD), Fourier transform infrared(FTIR). After the coating procedure, the CaP/PLA modified Ta plates were obtained andused for the investigation of in-situ mineralization. The samples were withdrawn forobservation and characterization on days of1,3and7. The CaP/PLA modified porous Tascaffolds were also obtained and used for the study of cell viability using theosteoblast-like cells (MG63). Furthermore, the effect of in vivo articular cartilage defectrepair has also been investigated.18female New Zealand rabbits were randomly divided into a vacuity contrast group (n=6, the cartilage and subchondral bone defect model), asimple group(n=6simple autogeneic periosteum tansplants were applied to repair thedefects), an experimental group (n=6, repaired with compound material made ofas-prepared porous tantalum and periosteum as a scaffold).The condyles of femur withthe defects were harvested twelve weeks after the operations. Thereafter, these sampleswere sliced into thin specimens parallel to the long axis of the condyles for histologicexamination. Statistical methods were used to evaluate restoration effects.After the operations for12weeks, all experimental animals were healthy with freemotive joints. The cartilage and bone regeneration of experimental group and thecontrols have been investigated through the morphologic compare of the repairedcondyles of femur. A group:Microscopy revealed that a good deal of chondrocytes werefound with thinner,continuous and smooth surface, comparing with the normalcartilage.The deep cells were columnar arrangement. integration of tantalum scafford andthe surrounding cartilage, bone cell ingrowth into porous tantalum. The interfaces ofregenerating tissues with adjacent tissues were integrated satisfactorily, and new bonetissue had grown into the porous scaffold.The average score is11.67; B group: Fewerrepairing cartilage tissue covering the defects, with rough surface, under pathologicdisorder arranged chondrocytes.The subchondral zone of cartilage had been formedwithosteo-like structure, connecting with the surrounding bone. The average score is7.33;C group:New repairing cartilage tissue was not easy to be found in the defect area,and a few of osteo-like structure was found at the bottom. Some fiber bundlemetachromatic material were found in the defect area. The average score is1.33.Therewere significant differences of repairing effect in those groups (p<0.05).Conclusion:1. The results indicated that the as-prepared scaffold which could provide growthfactors, physical support, structural guidance and interface for the new cartilage and bonegrowth was favorable to guide the cartilage and subchondral bone regeneration.2. Animal experimental results showed that the repairing effect of experimentalgroup was more significant than the controls(p<0.05). And this scaffold can not onlyprovide growth factors, physical support and structural guidance, but also give muchsuitable sites for adhesion of osteoblast cells. This research also showed the importance of the subchondral bone for its role in the treatment of articular surface damage. |
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