Amniotic fluid MSCs for scaffold-free cartilage repair: spheroid fusion and chondrogenic microtissue development.

Background: Articular cartilage injuries are challenging due to limited regenerative capacity, causing chronic pain and impaired mobility. Current treatments are often inadequate, necessitating novel cartilage repair approaches. This study investigates amniotic fluid-derived mesenchymal stromal cells (AF-MSC) as a promising cell source for tissue engineering.

Research design and method: Cartilage-like microtissues were produced by differentiating AF-MSC into chondrocytes within a 3D culture system. Using a 3D-printed non-adhesive micromold, AF-MSC spheroids were formed and fused into larger microtissues. Spheroids were characterized for morphology, viability, and extracellular matrix (ECM) production. The mechanical properties of resulting microtissues were compared to native cartilage and agarose hydrogel.

Results: AF-MSC proved a viable, scalable cell source for cartilage microtissues. Spheroid fusion created structures with mechanical properties and ECM components resembling native cartilage.

Conclusions: AF-MSCs differentiated into chondrocytes when stimulated with TGF-β3 in a 3D micromolded culture, forming uniform, viable spheroids with robust ECM production and mechanical properties. These spheroids fused into neocartilage microtissue, showing potential for regenerative medicine, especially osteoarthritis treatment and drug testing. Further research should optimize conditions and evaluate long-term biomechanical performance.