Strategies for Cartilage Repair and Regeneration

Articular cartilage is a hyaline cartilage consisting of a small number of chondrocytes and the surrounding extracellular matrix. Since articular cartilage lacks blood vessels and nerve fibers, it is quite difficult to work normal wound healing process once it is damaged. For localized cartilage defects, drilling or microfracture techniques that introduce cells from bone marrow, osteochondral autograft harvested from non-weight bearing area of the joint, and autologous cultured chondrocyte implantation have been performed. However, there is no gold standard procedure. The meniscus plays important roles in the knee joints, such as shock absorption, load distribution, and lubrication. For the meniscal tears in the vascularized area, suture is aggressively performed to preserve the function of the meniscus. However, there are still many cases with non-vascularized filed tears and degenerative tears that require extensive partial meniscectomy. Regenerative medicine is expected to be applied to cases of articular cartilage or meniscus injuries that are difficult to treat with conventional therapies, and some clinical applications have been started in Japan. In regenerative medicine, the important factors are the cells to be transplanted, the scaffold for cell proliferation, and the growth factors to promote cell proliferation and cell function. In the regeneration of articular cartilage and meniscus, cells are usually isolated and cultured from biopsied tissues and transplanted alone or with a scaffold, but the high quality control required for cell culture and the two-step process of tissue collection and transplantation in surgery are major barriers to clinical application. We have been attempting to regenerate articular cartilage and meniscus by transplanting small pieces of cartilage or meniscus without culture process. To date, we have confirmed the efficacy of minced tissue as a cell source in vitro and have reported good tissue regeneration of articular cartilage and meniscus in vivo using rabbits and pigs.