In vivo regeneration of complex cartilage/bone defect using biomimetic scaffolds

摘要

Introduction: Due to the complex structure of the osteochondral interface, highly bioinspired scaffolds with continuous gradients in properties are needed as potential repair grafts.In this work, a novel multilayer scaffold with continuous HA gradient was well designed for osteochondral repair and fabricated by microsphere-based selective laser sintering (SLS), using PCL and HA/PCL microspheres. Materials and Methods: PCL and HA/PCL composite microspheres were prepared using modified S/O/W emulsion solvent evaporation method . A cylindrical scaffold of 4 mm in diameter and 2.8 mm in thickness was designed via Pro/Engineer 3D modeling software and fabricated by SLS, with the HA content continuously increasing from 0 to 30%, from top to bottom. Rat bone mesenchymal stem cells (MSCs) were used to evaluate the in vim cytocompatibility. A critical sized osteochondral defect in rabbit was created to evaluate the in vivo repair, using micro-CT and histological analysis. Results and Discussion: The novel multilayer scaffolds with interconnected pores and moderate mechanical property were demonstrated to be suitable for cell adhesion and proliferation in vitro. For osteochondral repair in vivo, the subchondral bone was considered as the key foundation for successful cartilage repair. In our study, the microspheres-based HA/PCL bony phase effectively facilitated the new bone formation compared to the PCL group. After 6 weeks, new bone has formed at the bottom of the implanted multilayer scaffold. After 12 weeks, abundant new bone filled the subchondral area with obvious vascularization. Moreover, the new bone integrated well with the adjacent tissue, providing a strong mechanical supporting for the defect area. The rapid and sufficient regeneration of subchondral bone may further significantly improve the repair of cartilage. Completely different cartilage repair was observed for the two kinds of scaffold. The defect implanted with the multilayer scaffold was repaired with zonal hyaline cartilage, however, inferior repair with fibrous tissue and fibrocartilage in the chondral area was observed in the PCL scaffold. Conclusion: Combining the microsphere-based SLS technology and the strategy of continuous gradient scaffold, the current study designed and fabricated a novel multilayer scaffold with continuous HA gradient, with demonstrated great potential for osteochondral repair.