Hierarchical scaffolds for osteochondral tissue engineering

Osteochondral defects caused by various factors are still difficult clinical problems. With the development of tissue engineering, the strategies and methods for repairing osteochondral defects in the past decade have made great progress, and some osteochondral tissue stratified stent products have gradually entered the clinical trial stage.. The related articles on tissue engineering for the treatment of osteochondral defects were retrieved by searching databases with key words osteochondral defects, cartilage repair and hierarchical scaffolds. This paper discussed the research status of hierarchical scaffolds in osteochondral tissue engineering during recent five years. In this work, the classification of hierarchical scaffold including monophasic scaffolds, bilayered scaffolds, multilayered scaffolds and gradient scaffolds, are summarized by comparing different experiment researches. Furthermore, the advantages and disadvantages of different types of hierarchical scaffolds were introduced through analyzing relevant studies. Monophasic scaffolds can support the adhesion and proliferation of osteoblasts and chondrocytes, but lack the inherent stratified structure features required for osteochondral regeneration.. Bilayered scaffolds consist of a chondral layer and subchondral layer which base on the biocompatibility of monophasic scaffolds. Biphasic scaffolds are significantly better than monophasic scaffolds in simulating natural cartilage, but the interface between chondral and subchondral layer is poor binding. Compared with bilayered scaffold, trilayered scaffolds are added with an intermediate layer which simulates the calcification of normal cartilage between the two layers, so as to obtain better connection of the bone and cartilage layer. Unlike hierarchical scaffolds, gradient scaffolds provide a gradient connection between the layers, which is more similar to the native osteochondral tissue. In the past five years, the development of osteochondral layered scaffolds mainly depended on the novel structure and fabrication methods of scaffolds. However, correlational clinical studies are quite few. Further high quality and large clinical studies are still required.