Bioprinting chondrocyte hydrogel cultures onto fibre membranes for cartilage defect repair

This study developed a bioprinted matrix-assisted autologous chondrocyte implantation strategy that combines cell-laden collagen-alginate-fibrin hydrogels with Chondro-Gide collagen membranes for cartilage defect repair. Using reactive jet impingement bioprinting, the authors deposited CAF hydrogels containing chondrocytes at low and high cell densities directly onto Chondro-Gide substrates and compared these constructs with CAF-only hydrogels and manually seeded membrane controls over 14 days. Cell viability remained high across conditions, while high-density cultures developed stronger cell-cell interactions and more compact cellular structures. Chondro-Gide-containing constructs promoted cell migration toward the membrane surface and alignment along collagen fibres, supporting earlier extracellular matrix development. ACAN expression increased substantially from day 1 to day 14 across all groups, while SOX9 expression was generally higher in Chondro-Gide-containing conditions. High-density Chondro-Gide/CAF constructs showed the strongest collagen II and sulphated glycosaminoglycan deposition, indicating enhanced cartilage-specific matrix formation. Mechanical testing showed that compressive modulus increased significantly between days 1 and 14 in all cellular groups but not in acellular gels, with Chondro-Gide/CAF constructs showing the greatest stiffness at day 14 while largely maintaining construct volume. Overall, the study demonstrates that combining high-density chondrocyte-laden CAF bioinks with a clinically used collagen membrane can improve cell distribution, extracellular matrix formation, structural stability, and mechanical maturation, supporting development of an in-clinic bioprinting approach for next-generation cartilage repair.