Natural Macromolecular Polysaccharide-Based Hydrogels Incorporating Cartilage Extracellular Matrix Particles For Cartilage Repair

Articular cartilage lacks blood vessels,nerves and lymphatic vessels,and it is difficult to self-repair once damaged.Currently,a large number of treatment methods to improve the cartilage,including autologous chondrocyte implantation,autografts and allografts,have their own limitations.At present,cartilage repair has become one of the major clinical challenges.Fortunately,the development of cartilage tissue engineering brings new hope for cartilage repair.Natural macromolecular polysaccharide-based hydrogel,which is one of the important biomaterial in cartilage tissue engineering,has good biocompatibility and biodegradability.In this study,we developed a bioactive hydrogel(G-CS/OHA)composed of glycol chitosan(G-CS)and oxidized hyaluronic acid(OHA)based on the Schiffbase reaction between amino of G-CS and aldehyde groups of OHA.We studied the impact of the mix proportion of two ingredients and the degree of oxidation of OHA on the properties of hydrogel.The results showed that the OHA60%=2%(w/v),G-CS:OHA 60%=2:1(S1)hydrogel had excellent compression strength,degradation property and biocompatibility,Therefore,we chose S1 hydrogel for further study.Cartilage extracellular matrix(ECM)has been used to prepare and functionalize other biomaterials for enhancing the chondrogenesis of mesenchymal stem cell(MSC),due to the properties that it is actually custom-made b y cells,contains the relevant bioactive signal and has good chondroinductivity.Besides,ECM is low cost and easy access.Considering the pure G-CS/OHA hydrogels may have many shortcomings such as poor mechanical property and insufficient ability of chondroinductivity,different amount of ECM partiles were added in S1 hydrogel to functionalize hydrogel.The results showed the S1/ECM 2%(w/v)(S3)hydrogel showed the most appropriate compression strength and an ideal environment for proliferation of BMSCs.Therefore,we chose the S3 hydrogel for further study.Previous studies have shown that the synergistic effects of TGF-?1,BMP-7 and Kartogenin(TBK)could promote the chondrogenesis of BMSCs in vitro.In order to estimate the chondroinductivity of ECM particles,BMSCs were embedded in S1 and S3 hydrogel for culture in vitro.In the process of culture,routine medium and chondrogenic medium(routine medium+TBK)were added respectively.The results showed that the accumulation of glycosaminoglycands(GAGs)and type ? collagen(COL ?)was significantly higher in S3/BMSCs/TBK hydrogel compared other groups.In vivo,cartilage defects of rats generated most mature tissue within S3/BMSCs/TBK group.The tissues were more integrative and the surface was smoother and more complete compared to the other groups.These results show that G-CS/OHA hydrogel functionalized with ECM particles is a good candidate biomaterial to be applied in cartilage tissue engineering.Encapsulating BMSCs and TBK within G-CS/OHA/ECM hydrogel is a good treatment for cartilage repair.