In situ implantation of type II collagen-based double-layer scaffolds for Articular Osteochondral Regeneration comprising hyaline cartilage and vascularized subchondral bones

The articular osteochondral injury involves the repair of hyaline cartilage, subchondral bone plate, and cancellous bone. Due to the weak regeneration ability of chondrocytes and the complex structure of the bone-cartilage junction, there is currently no excellent repair method. The challenge of hyaline cartilage repair is to avoid fibrosis and hypertrophy, which has been solved to some extent after the advent of type II collagen scaffolds; the difficulty of the subchondral bone plate and cancellous bone repair lies in the repair of the complex transition structure of cartilage tidemark, calcified cartilage, subchondral bone plate, and cancellous bone. Inspired by developmental biology, the generation of this complex structure during development depends on endochondral ossification (ECO). ECO depends on some specific proteins, such as IHH, PTHrP, BMP, and WNT, and the receptors of these proteins. Studies have shown that polydopamine coating can promote the production of BMP and WNT proteins. We developed a type II collagen-based double-layer scaffold (Col II & Dopa-Col II) with type II collagen on the upper layer and polydopamine-coated type II collagen on the lower layer. Proteomics and RNA sequencing analysis have found that polydopamine coating can mobilize the proliferation and hypertrophy differentiation of chondrocytes, induce intra-chondral vascular nerve invasion, and promote ECO and bone remodeling by upregulating Parathyroid hormone signaling pathway, Hedgehog signaling pathway, VEGF signaling pathway, and Axon guidance. All the results indicate that Col II & Dopa-Col II can achieve hyaline cartilage and vascularized subchondral bone regeneration.