Accelerating cartilage regeneration with DNA-SF hydrogel sustained release system-based cartilage organoids.

Background: Cartilage repair remains a considerable challenge in regenerative medicine. Despite extensive research on biomaterials for cartilage repair in recent years, issues such as prolonged repair cycles and suboptimal outcomes persist. Organoids, miniature three-dimensional (3D) tissue structures derived from the directed differentiation of stem or progenitor cells, mimic the structure and function of natural organs. Therefore, the construction of cartilage organoids (COs) holds great promise as a novel strategy for cartilage repair.

Methods: This study employed a digital light processing system to perform 3D bioprinting of a DNA-silk fibroin (DNA-SF) hydrogel sustained-release system (DSRGT) with bone-marrow mesenchymal stem cells (BMSCs) to construct millimeter-scale cerebral organoids. COs at different developmental stages were characterized, and the COs with the best cartilage phenotype were selected for in vivo cartilage repair in a rat articular cartilage defect model.

Results: This study developed a DSRGT by covalently grafting glucosamine (which promotes cartilage matrix synthesis) and TD-198946 (which promotes chondrogenic differentiation) onto a hydrogel using acrylic acid-polyethylene glycol-N-hydroxysuccinimide (AC-PEG-NHS). In vitro, 4-week COs exhibited higher SRY-box transcription factor 9 (SOX9), type II collagen (Col II), and aggrecan (ACAN) expression and lower type I collagen (Col I) and type X collagen (Col X) expression, indicating that 4 weeks is the optimal culture duration for hyaline cartilage development. In vivo, the mitogen-activated protein kinase (MAPK) signaling pathway was upregulated in 4-week COs, enabling cartilage repair within 8 weeks. Transcriptomic analysis revealed that cartilage regenerated with 4-week COs presented gene expression profiles resembling those of healthy cartilage.

Conclusions: This study employs DSRGT to construct COs, providing an innovative strategy for the regeneration of cartilage defects.