From Electrospun Nanofibrils to 3D Zonal Cartilage: Biomimetic Reconstruction via Aligned Nanofibrillar Yarn Assemblies for Cartilage Regeneration

Articular cartilage exhibits a distinct zonal architecture that is crucial for its mechanical resilience and functional performance. Recreating this zonal architecture in the engineered scaffolds remains a major challenge in cartilage tissue engineering. In this study, we report the development of a scaffold mimicking the zonal architecture of articular cartilage using nanofibrillar yarn assemblies. By leveraging the flexibility and manoeuvrability of nanofibrillar yarns, we fabricated nanofibrillar yarn-based articular cartilage scaffolds (NACS) with two architecturally distinct zones, achieved through region-specific alignment of yarn bundles. The yarns were oriented parallel and perpendicular to the scaffold surface in the superficial and deep zones, respectively, to emulate the zonal architecture of native cartilage. This region-specific design was intended to guide chondrocytes to deposit a cartilage-specific extracellular matrix (ECM) along the yarn axis, recapitulating the organized ECM structure of the superficial and deep zones. Upon seeding, human mesenchymal stem/stromal cells (hMSCs) attached and aligned along the axis of the nanofibrillar yarns and adopted a chondrocyte-like rounded morphology following chondrogenic induction. hMSCs exhibited robust growth and deposited ECM, predominantly composed of type II collagen, which was found to be aligned along the orientation of the nanofibrillar yarn bundles within 4 weeks. These findings demonstrate the potential of regionally aligned nanofibrillar yarn-based scaffolds to recapitulate selected depth-dependent architectural features of native articular cartilage, offering a promising strategy for functional cartilage regeneration.