Preparation Of Scaffold With Different Structures For Regeneration Of Osteochondral Defects In Vivo

Osteochondral defect refers to the damage of cartilage as well as subchondral bone,leading to acute pain in knee articular and influencing human normal life.Cartilage tissue engineering focusing on the regeneration of cartilage and disregarding the subchondral bone always leads to partial regeneration of the damage,resulting in poor mechanical and physiological properties.Unlike cartilage tissue engineering,osteochondral regeneration contains two different types of tissues,and is highly dependent on the materials and scaffold structures.Currently,the scaffolds suitable for in situ inductive regeneration of both types of tissues are urgently needed.In this work,two different types of scaffolds were prepared for osteochondral regeneration.Firstly,a biphasic scaffold integrated by macro-porous fibrin and 3D-printed wollastonite(containing 8%MgSi03(CS-Mg8))scaffolds,either preloaded with rabbit bone marrow mesenchymal stem cells(BMSCs)or not,were fabricated and used to repair osteochondral defects in vivo(full thickness osteochondral defects in rabbits,4 mm in diameter and 4 mm in depth).The fibrin scaffold had a pore size of 100-200 ?m,and was degraded gradually and reached weight loss over 80%at 4 w.The presence of BMSCs could accelerate the degradation rate.BMSCs could well proliferate in the fibrin scaffold along with time prolongation.The CS-Mg8 scaffold possessed a regular structure of cross stacked CS-Mg8 rods,and was degraded rather slowly with a mass loss of 8.5%at 4 w.BMSCs adhered and showed well spreading on the CS-Mg8 scaffold,without apparent proliferation in vitro.In vivo transplantation of the biphasic scaffolds,either preloaded with BMSCs or not,could induce the regeneration of both cartilage and subchondral bone to a great extent.Loading of BMSCs enabled better regeneration of cartilage layer,leading to smoother macroscopic appearance,good integrity with surrounding tissue and tide mark formation.However,no significant difference in bone formation and in gene expression was found with and without BMSCs loading.The scaffold with orient pore structure can facilitate nutrition exchange and cell migration.A scaffold with longitudinal pore structure was prepared by a unidirectional freeze-drying method,which was confirmed by SEM observation.The compressive modulus of orient PLGA scaffold was higher than that of random PLGA scaffold in a wet state.In vitro cell culture showed that BMSCs could migrate deeper into the orient PLGA scaffold.In vivo implantation of these two types of PLGA scaffolds showed that the orient scaffold could regenerate the cartilage better with smoother macroscopic appearance,and good integrity with surrounding tissue.