Cartilage Organoids from Articular Chondroprogenitor Cells and Their Potential to Produce Neo-Hyaline Cartilage

Introduction The use of autologous human primary articular chondrocytes (hPACs) for repairing damaged cartilage is the golden standard; however, their 2-dimensional (2D) expansion induces dedifferentiation, making it challenging to create hyaline cartilage. Spinner flasks are efficient for generating cartilage organoids, allowing hPACs to proliferate without dedifferentiation; however, porcine notochordal cell-derived matrix (NCM) is needed for aggregation, limiting clinical application. Human articular chondroprogenitor cells (hACPCs) can be expanded many fold while maintaining chondrogenic potential. Therefore, the scalable production of hACPC cartilage organoids without NCM in spinner flasks was investigated in this study. Methods hPAC organoids with NCM and hACPC organoids using bone morphogenetic protein 9 (BMP-9) were produced in spinner flasks in 14 days. Thereafter, approximately 20 organoids were fused in low adhesive wells for 21 days. Organoids underwent mechanical testing, and both organoids and fused constructs were evaluated using biochemical, histological, and immunohistochemical analysis. Results The hACPCs self-assembled and synthesized abundant extracellular matrix once stimulated with BMP-9. The hPAC and hACPC organoids showed similar mechanical properties, but hACPC organoids and fused constructs showed a more uniform matrix and cell distribution. Conclusion The hACPC organoids fused into a neo-hyaline cartilage-like tissue, demonstrating their potential for improved, scalable cartilage tissue repair.