High Hopes for the Biofabrication of Articular Cartilage-What Lies beyond the Horizon of Tissue Engineering and 3D Bioprinting?

Technologies and biomaterials for 3D bioprinting have been developing extremely quickly in the past decade as they hold great potential in tissue engineering. This, together with the possibility to differentiate stem cells of different origin into any cell type, raises the hopes in regenerative medicine once again after the initial breakthrough with stem cells in the 1980s. Nevertheless, three decades of 3D bioprinting experiments have shown that the production of functional tissues would take a longer time than anticipated. Cartilage, one of the simplest tissues in the body, consists of only one cell type. It is not vascularised and innervated and does not have lymphatic vessels either, which makes it a perfect target tissue for successful implantation. The tremendous amount of work since the beginning of this century, combining the efforts of bioengineers, material scientists, biologists, and physicians, has culminated in multiple proof-of-concept constructs that have been implanted in animals. However, there is no single reproducible, standardised, widely accessible and accepted strategy that can be readily applied in the clinic. In this review, we focus on the current progress in the field of the 3D biofabrication of articular cartilage and critically assess failures and future challenges.