Preparation of a biphase composite scaffold and its application in tissue engineering for femoral osteochondral defects in rabbits.

Purpose: Three-dimensional bioactive scaffolds are useful tools for stem cell implant in tissue-engineering. For chondral and subchondral repair, the chondroinductive and osteoinductive property of a scaffold is a major challenge. The scaffolds that aim to osteogenic differentiation have been well studied. However, cartilage cells can hardly be induced for osteogenesis, and monophase scaffolds cannot ideally repair both cartilage and subchondral defects at the same time.

Methods: We developed a novel biphase composite scaffold and observe its application osteochondral defects. We combined the advantages of silk-fibroin/chitosan (SF/CS) scaffold in chondrogenic differentiation and the silk-fibroin/chitosan/nano-hydroxyapatite (SF/CS/nHA) scaffold in osteogenic differentiation and bone regeneration, and synthesized a SF/CS-SF/CS/nHA scaffold, which contained both the chondrocytic phase (SF/CS) and the osteoblastic phase (SF/CS/nHA).

Results: The biphase scaffold exhibited a porosity ratio around 90% and a water absorption ratio about 822%. A similar degradation property to traditional monophase scaffolds was observed. Bone mesenchymal stem cells (BMSCs) showed a good proliferation on this scaffold. Expression of two types of collagen was inducable for BMSCs on the scaffold. Neoformative extracellular matrix integrated with the scaffold was observed by the scanning electron microscope. When implanted in the lesion site in the rabbit femur with cartilage injury, mixing and filling function were exerted by the cell-scaffold constructs (CSCs). Micro-CT scanning revealed both chondral and subchondral layers were repaired. Moreover, type I and II collagens were both expressed in the implanted CSCs.

Conclusions: Chondral and subchondral repair can be achieved using the biphase scaffold implant that permits both chondrogenesis and osteogenesis from BMSCs. This approach has the potential to be clinically used for tissue engineering implantation.