The regeneration of damaged or diseased cartilage is challenging due to its poor self-repair capacity. Instead of relying on invasive surgical replacements, tissue engineering strategies aim to facilitate the formation of new tissue that integrates with the native cartilage. However, robust integration is complicated by a lack of chondrocyte migration at the host tissue interface, which poses a critical concern for clinical translation. Our group has previously developed an in vitro 3D-bioassembly model for investigating cell spheroid fusion processes, as well as screening for therapeutics in diseased microenvironments.1,2 Furthermore, mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have been shown to promote proliferation and migration of chondrocytes.3,4 This study aims to assess the potential of human bone-marrow derived MSC-EVs to improve the regeneration of diseased cartilage and enhance the integration of engineered tissue into native cartilage, using the previously developed 3D-bioassembly model.
Human articular chondrocytes (hACs) were centrifuged to form microtissue spheroids (1mm diameter). Multiple spheroids were bio-assembled within 3D-printed thermoplastic scaffolds after 10-days culture in chondrogenic media. EVs were extracted (Izon AFC) from concentrated conditioned medium, following 2D incubation of hBMSCs in serum-free media. MSC-EVs were supplied (106 particles/mL) to spheroids over 14-days culture. Histological analysis (Safranin-O/fast green, Collagen I and II, DAPI staining) showed that EV supplementation increased hAC migration into the tissue interface, while retaining collagen II deposition, indicating the formation of hyaline cartilage in the fusion region. Thus, our 3D-bioassembly model highlights the potential of EVs to increase chondrocyte migration, leading to improved tissue fusion and cartilage regeneration.