Ⅰ/Ⅲ Collagen-based Composite Scaffolds Incorporating VAPs For Regulation Of Endogenous Cartilage Repair

Due to its avascular nature,low cell density and low proliferation activity,cartilage cannot regenerate after degenerative diseases such as injury,wear and tear or osteoarthritis.Current clinical treatment strategies,including debridement,microfracture,autologous chondrocyte transplantation,and mosaicplasty,have their own limitations.Therefore,the repair of cartilage defects is still a challenge in clinical practice.In recent years,tissue engineering for the purpose of reconstructing the complex architecture and biomechanical properties of the native tissue has provided a new technique for cartilage repair.The construction of biological scaffolds with controlled release characteristics is one of the most important research directions in this field.In this work,we developed a COL Ⅰ-COL Ⅲ composite scaffold incorporating VAPs and implemented the control release according micro-nano structure.Then this composite scaffolds were implanted into animal models to study the effect of cartilage defect repair.The specific steps are as follows:(1)The optimum proportion of COL Ⅰ-COL Ⅲ composite scaffolds were determined.COL Ⅰ-COL Ⅲ composite scaffolds with different mass ratios were prepared by blending,freeze drying,cross-linking,refreeze drying and other steps.The optimal proportion of the composite scaffolds were determined by studying and characterizing the porosity,swelling rate,hot water dissolution rate,contact Angle,compression modulus and biocompatibility.The results showed that optimal proportions of COL Ⅰ-COL Ⅲ composite scaffold was 1:1.(2)Composite scaffolds incorporating VAPs were prepared and studied on biocompatibility.VAPs-PLGA microspheres were prepared.The prepared VAPs-PLGA microspheres were uniformly compounded into the COL Ⅰ-COL Ⅲcomposite scaffolds by physical adsorption method,and the COL I-COL Ⅲ composite scaffolds incorporating VAPs were prepared.In vitro release kinetics experiment showed that the release of VAPs in the COL Ⅰ-COL Ⅲ composite scaffolds were over21 d,and accorded with the requirement of material design for controled release.BMSCs were cultured in vitro to the third generation and inoculated into the above composite scaffolds and their extracts.The adhesion,proliferation and activity of BMSCs were detected by MTT and AO/EB staining.The results showed that the COLⅠ-COL Ⅲ composite scaffolds incorporating VAPs had good biocompatibility.Both the scaffolds itself and its extract could increase the activity of BMSCs and promote the adhesion and proliferation of BMSCs.(3)The effect of COL Ⅰ-COL Ⅲ composite scaffolds incorporating VAPs on the repair of cartilage defects in rabbit models.A rabbit model of articular cartilage defect was established,and the COL Ⅰ-COL Ⅲ(1:1)composite scaffolds and COL Ⅰ-COL Ⅲcomposite scaffolds incorporating VAPs were implanted into the defect area respectively.Animals were sacrificed and articular cartilage specimens were collected at 4,8,12 and 16 weeks after surgery.Gross observation,micro-CT scanning,histological staining and histological scoring were performed to evaluate the repair effect of the cartilage defects.Compared with the COL Ⅰ-COL Ⅲ(1:1)composite scaffolds group,the COL Ⅰ-COL Ⅲ composite scaffolds incorporating VAPs group was completely repaired at 16 weeks.The defect was completely filled and the boundary of the surrounding tissue was difficult to identify.Compared with model control group and composite scaffolds without VAPs group,histological scores(15.3)showed significant difference.In conclusion,the COL Ⅰ-COL Ⅲ composite scaffolds incorporating VAPs could effectively repair the cartilage defect of the knee joint of animals,and the repair effect may be related to the composition and structure of the composite and the controled slow release of VAPs.