Current status and perspective of 3D printing technology to construct articular osteochondral scaffolds with boundary structure

Articular osteochondral defects are very common in clinical practice. Tissue engineering technology provides a promising treatment strategy for the disease. The articular osteochondral unit is composed of hyaline cartilage, calcified cartilage zone and subchondral bone. As the boundary structure between articular bone and cartilage, calcified cartilage zone plays an important role in stress conduction and microenvironment regulation. Composite scaffolds with boundary structure for defect repair is a development direction of osteochondral tissue engineering in the future. 3D printing technology has the advantages and characteristics of speediness, accuracy and personalized customization, which meet the needs of geometric shape, multi-layer structure and component differentiation when manufacturing osteochondral scaffold with boundary structure. We summarize the morphological structure, biochemical components and physiological functions of articular osteochondral unit, and comment on the necessity of constructing its boundary structure in articular osteochondral composite tissue engineering scaffold and its construction scheme by 3D printing technologies, such as material extrusion, melt electro-writing, electro-spinning, stereolithography, and digital light processing. Deepening the basic research of articular cartilage boundary structure and expanding the application of 3D printing technology in the construction of osteochondral scaffolds containing boundary structure will realize the bionic function and structure of osteochondral scaffold, and finally improve the regeneration treatment of articular osteochondral defects caused by various injuries.