Biphasic fish collagen scaffold for osteochondral regeneration

Developing a biphasic scaffold that can concurrently regenerate both cartilage and bone of osteochondral defects (OCDs) is a challenge. Fish collagen (FC) is currently considered an alternative scaffold to mammalian collagen (MC) due to its safety, accessibility, lower price, and similar biological properties compared to those of MC. Here, we developed bilayer FC-based composite scaffolds with different components and pore sizes to modulate the differentiation fate of bone marrow stem cells (BMSCs): chondroitin sulfate-incorporated FC scaffolds (FC-CS) with small pores (approximately 128 μm) as the top layer and hydroxyapatite-incorporated FC scaffolds (FC-HA) with larger pores (approximately 326 μm) as the bottom layer. Both the FC-CS and FC-HA scaffolds possessed good cytocompatibility, excellent water absorption, suitable biodegradability and high cell seeding efficiency. The in vitro results indicated that FC-CS and FC-HA promote chondrogenesis and osteogenesis of BMSCs, respectively, as validated by gene expression and histological examination. Furthermore, compared to the empty group in a rabbit OCD model, the bilayer scaffold significantly induced simultaneous regeneration of cartilage and subchondral bone after 6 and 12 weeks of implantation, which was confirmed by gross, histological, and microcomputed tomography images. Our findings demonstrated that the FC-based bilayer scaffold is a promising scaffold for the repair of OCD.