Three‐dimensional printed biomimetic multilayer scaffolds coordinated with sleep‐related small extracellular vesicles: A strategy for extracellular matrix homeostasis and macrophage polarization to enhance osteochondral regeneration

Abstract

Cartilage defects resulting from injury or degeneration are a common clinical problem, and due to its avascular nature, articular cartilage has poor self‐healing capacity. Three‐dimensional (3D) bioprinting has attracted great attention in tissue engineering. Melatonin (MT), a hormone mainly secreted at night, plays an important role in tissue repair. Small extracellular vesicles (sEV) are considered ideal drug delivery vehicles and MT‐sEV (sleep‐related sEV) have the potential ability to promote cartilage regeneration. Here, biomimetic multilayer scaffolds were fabricated using 3D bioprinting. A double network hydrogel, composed of methacrylated hyaluronic acid and gelatin methacryloyl (HG), was prepared. MT‐sEV and HG hydrogel were used to create a cartilage layer. A bone layer was formed using poly(ε‐caprolactone) and hydroxyapatite ultralong nanowires. Additionally, two bioinks were alternately printed at the interface layer. The results of RNA sequencing revealed the potential regulatory mechanisms. MT‐sEV showed promotional effects on cell migration, proliferation, chondrogenic differentiation, and extracellular matrix (ECM) deposition. Moreover, MT‐sEV altered macrophage polarization and regulated the expression of inflammatory cytokines. In vivo experiments demonstrated that the biomimetic multilayer scaffolds promoted cartilage regeneration. These experiments demonstrated the ability of MT‐sEV to regulate the immune microenvironment and promote the secretion of ECM, providing a promising strategy for cartilage regeneration.