Fabrication of an osteochondral graft with using a solid freeform fabrication system

Current approaches for the engineering of osteochondral grafts are associated with poor tissue formation and compromised integration at the interface between the cartilage and bone layers. Many researchers have attempted to provide osteochondral grafts of combined cartilage and bone for osteochondral repair to help overcome the limitations of standard procedures. Solid freeform fabrication is recognized as a promising tool for creating tissue engineering scaffolds due to advantages such as superior interconnectivity and a highly porous structure. This study aimed to develop a three-dimensional plotting system to enable the manufacturing of a biphasic graft consisting cartilage and subchondral bone for application to osteochondral defects. The material advantages of both synthetic (poly L lactide-co-polyglycolide) and natural (alginate) polymers were combined for a supporting frame and cell printing. Specifically, in order to promote the maturity of the osteochondral graft in our study, cartilage-derived ECM (cECM) or hydroxyapatate (HA) substances blended with alginate was plotted together with human fetal cartilage-derived progenitor cells in the cartilage or subchondral bone layer under a multi-nozzle deposition system. Notably, a plotted biphasic graft shows good integration between cartilage and subchondral bone layers without structural separation. Furthermore, the non-toxicity of the cECM and HA substances were proved from a live/dead assay of plotted cell-laden alginate. A fabricated osteochondral graft with cECM and HA substances showed dominant cartilage and bone tissue formation in a differentiation assay. Future studies should be done to modify the alginate physical properties for long-lasting structural stability.