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Tissue engineering approaches that recapitulate cartilage biomechanical properties are emerging as promising methods to restore the function of injured or degenerated tissue. However, despite significant progress in this research area, the generation of engineered cartilage constructs akin to native counterparts still represents an unmet challenge. In particular, the inability to accurately reproduce cartilage zonal architecture with different collagen fibril orientations is a significant limitation. The arrangement of the extracellular matrix (ECM) plays a fundamental role in determining the mechanical and biological functions of the tissue. In this study, it is shown that a novel light‐based approach, Filamented Light (FLight) biofabrication, can be used to generate highly porous, 3D cell‐instructive anisotropic constructs that lead to directional collagen deposition. Using a photoclick‐based photoresin optimized for cartilage tissue engineering, a significantly improved maturation of the cartilaginous tissues with zonal architecture and remarkable native‐like mechanical properties is demonstrated. Cartilage tissue engineering approaches hold great promises for restoring the function of damaged tissue. However, accurately reproducing cartilage matrix anisotropic architecture still represents an unmet challenge. In this work, it is demonstrated that the fast and biocompatible Filamented Light (FLight) biofabrication can be used to significantly improve the maturation of cartilaginous tissues featuring zonal architecture and remarkable native‐like mechanical properties.

Articular cartilage defects caused by traumatic injury rarely heal spontaneously and predispose into post‐traumatic osteoarthritis. In the current autologous cell‐based treatments the regenerative process is often hampered by the poor regenerative capacity of adult cells and the inflammatory state of the injured joint. The lack of ideal treatment options for cartilage injuries motivated the authors to tissue engineer a cartilage tissue which would be more resistant to inflammation. A clustered regularly interspaced short palindromic repeats (CRISPR)‐Cas9 knockout of TGF‐β‐activated kinase 1 (TAK1) gene in polydactyly chondrocytes provides multivalent protection against the signals that activate the pro‐inflammatory and catabolic NF‐κB pathway. The TAK1‐KO chondrocytes encapsulate into a hyaluronan hydrogel deposit copious cartilage extracellular matrix proteins and facilitate integration onto native cartilage, even under proinflammatory conditions. Furthermore, when implanted in vivo, compared to WT fewer pro‐inflammatory M1 macrophages invade the cartilage, likely due to the lower levels of cytokines secreted by the TAK1‐KO polydactyly chondrocytes. The engineered cartilage thus represents a new paradigm‐shift for the creation of more potent and functional tissues for use in regenerative medicine. Here a method to efficiently repair cartilage defects with a novel combination of cells, gene editing, and hydrogel is presented. The highly chondrogenic cells present inflammation‐resistance properties due to gene editing, can be used in off‐the‐shelf and mature into stiff constructs that integrate into mature cartilage when encapsulated in the hyaluronan‐based hydrogel.

Biofabrication techniques including three-dimensional bioprinting could be used one day to fabricate living, patient-specific tissues and organs for use in regenerative medicine. Compared to traditional casting and molding methods, bioprinted structures can be much more complex, containing for example multiple materials and cell types in controlled spatial arrangement, engineered porosity, reinforcement structures and gradients in mechanical properties. With this complexity and increased function, however, comes the necessity to develop guidelines to standardize the bioprinting process, so printed grafts can safely enter the clinics. The bioink material must firstly fulfil requirements for biocompatibility and flow. Secondly, it is important to understand how process parameters affect the final mechanical properties of the printed graft. Using a gellan-alginate physically crosslinked bioink as an example, we show shear thinning and shear recovery properties which allow good printing resolution. Printed tensile specimens were used to systematically assess effect of line spacing, printing direction and crosslinking conditions. This standardized testing allowed direct comparison between this bioink and three commercially-available products. Bioprinting is a promising, yet complex fabrication method whose outcome is sensitive to a range of process parameters. This study provides the foundation for highly needed best practice guidelines for reproducible and safe bioprinted grafts.

Achieving regeneration of articular cartilage is challenging due to the low healing capacity of the tissue. Appropriate selection of cell source, hydrogel, and scaffold materials are critical to obtain good integration and long‐term stability of implants in native tissues. Specifically, biomechanical stability and in vivo integration can be improved if the rate of degradation of the scaffold material matches the stiffening of the sample by extracellular matrix secretion of the encapsulated cells. To this end, a novel 3D‐printed lactide copolymer is presented as a reinforcement scaffold for an enzymatically crosslinked hyaluronic acid hydrogel. In this system, the biodegradable properties of the reinforced scaffold are matched to the matrix deposition of articular chondrocytes embedded in the hydrogel. The lactide reinforcement provides stability to the soft hydrogel in the early stages, allowing the composite to be directly implanted in vivo with no need for a preculture period. Compared to pure cellular hydrogels, maturation and matrix secretion remain unaffected by the reinforced scaffold. Furthermore, excellent biocompatibility and production of glycosaminoglycans and collagens are observed at all timepoints. Finally, in vivo subcutaneous implantation in nude mice shows cartilage‐like tissue maturation, indicating the possibility for the use of these composite materials in one‐step surgical procedures. The biodegradable properties of a novel lactide copolymer are matched to the matrix deposition of articular chondrocytes embedded in an enzymatically crosslinked hyaluronic acid‐based hydrogel. The lactide reinforcement provides stability to the soft hydrogel in the early stages and degrades once sufficient matrix has been deposited by cells. Excellent biocompatibility and production of glycosaminoglycans and collagens are observed at all timepoints.