Recent advancements in cartilage tissue engineering innovation and translation

Articular cartilage was expected to be one of the first successfully engineered tissues, but today, cartilage repair products are few and they exhibit considerable limitations. For example, of the cell-based products that are available globally, only one is marketed for non-knee indications, none are indicated for severe osteoarthritis or rheumatoid arthritis, and only one is approved for marketing in the USA. However, advances in cartilage tissue engineering might now finally lead to the development of new cartilage repair products. To understand the potential in this field, it helps to consider the current landscape of tissue-engineered products for articular cartilage repair and particularly cell-based therapies. Advances relating to cell sources, bioactive stimuli and scaffold or scaffold-free approaches should now contribute to progress in therapeutic development. Engineering for an inflammatory environment is required because of the need for implants to withstand immune challenge within joints affected by osteoarthritis or rheumatoid arthritis. Bringing additional cartilage repair products to the market will require an understanding of the translational vector for their commercialization. Advances thus far can facilitate the future translation of engineered cartilage products to benefit the millions of patients who suffer from cartilage injuries and arthritides. In this Review, the current landscape of tissue engineering for repair of articular cartilage is discussed, with reference to advances in cell sources, bioactive stimuli and the use of scaffolds, and with consideration of the challenges that result from the inflammatory articular environments in osteoarthritis and rheumatoid arthritis. Of the cell-based articular cartilage products available globally, only one is marketed for non-knee indications, none are marketed for severe osteoarthritis and none are marketed for rheumatoid arthritis.Cartilage tissue engineering advances include making scaffold-based and scaffold-free cartilage with robust mechanical properties that might enable implants to survive in the loaded-joint environment.Tissue engineering cartilage implants to survive the inflammatory environment through the use of immunomodulatory biomaterials and synthetic biology is a current research highlight.Most large-animal studies for cartilage tissue engineering in the knee use porcine, caprine and ovine models, whereas porcine models are used for temporomandibular joint studies.Several tissue-engineered cartilage products in clinical development use allogeneic cell sources; the use of cell banks that employ allogeneic cells can improve reproducibility and consistency.Owing to the arduous nature of translating biologics, academic researchers should familiarize themselves with the translational vector (including regulatory, manufacturing, funding and intellectual property aspects) to facilitate clinical development.