Schematic of the melt electrowriting (MEW) process for producing 3D bioprinted scaffolds for the growth of fibrocartilage tissue (inset photo).
Schematic of the melt electrowriting (MEW) process for producing 3D bioprinted scaffolds for the growth of fibrocartilage tissue (inset photo).

The meniscus keeps the knee stable and redistributes forces through the joint into surrounding collagen fibers. Despite their remarkable mechanical capabilities, the meniscus is prone to tear and, because of its limited blood supply, does not fully regenerate. Damage to the meniscus can, in the long term, lead to degeneration and osteoarthritis. Tissue engineering approaches employing biomaterial scaffolds offer an alternative. Now researchers from Trinity College Dublin, the Royal College of Surgeons in Ireland, and Johnson & Johnson Services Inc. have developed inkjet bioprinted scaffolds that support the development of new tissue with mechanical properties that match those of the meniscus [Barceló et al., Acta Biomaterialia 158 (2023) 216-227,].

The team, led by Daniel J. Kelly, used 3D inkjet bioprinting to deposit a cell-impregnated bioink into additively manufactured scaffolds with different architectures. The polymer scaffolds, which are fabricated to have different aspect ratios, create a fibrous network that guides the growth of bone-marrow derived mesenchymal stem cells into useful fibrocartilage tissue. The researchers used two techniques to produce the scaffolds: fused deposition modelling (FDM) and melt electrowriting (MEW), which produce fibers of different diameters (150 microns or 15 microns, respectively) and internal architectures.

The spatial organization of the collagen network that the growing cell form is highly influenced by the scaffold architecture. The higher aspect ratio scaffolds produce tissue with anisotropic mechanical properties, simulating the characteristics of natural meniscal tissue more closely. Scaffolds produced with MEW, moreover, are highly porous and soft in compression while relatively stiff in tension, mimicking the behavior of native meniscus and producing fibrocartilaginous tissues with very similar properties. The architecture of MEW scaffolds can be readily tailored to determine the direction of collagen fiber growth and tune the anisotropic tensile mechanical behavior. The approach could enable the creation of spatially inhomogeneous scaffolds that guide the alignment of tissue in multiple directions simultaneously.

This proof-of-concept study indicates that MEW inkjet bioprinting can engineer anisotropic, spatially defined tissue that mimics native meniscal tissue. The researchers believe that bioprinted MEW scaffolds could offer new treatment options for patients with a damaged or diseased meniscus. Not only could the scaffolds enable the fabrication of biomimetic meniscal-like tissue, but the flexibility of their tailorable structures could offer the possibility of patient-specific implants.

“This multiple tool biofabrication strategy constitutes the basis of a promising approach for the development of biomimetic meniscus implants,” write the researchers.