Developing Bioreactors to Host Joint-Derived Tissues That Require Mechanical Stimulation

Demographics of the Western Societies points toward an elderly population in need of research on replacement parts for joints and their components, such as the meniscus, cartilage, ligaments, tendons, and intervertebral discs. There is a lack of basic research to predict treatment options before degeneration or inflammation has progressed, and at late stages, when regeneration might not be an option anymore. Thus, to achieve a better understanding of the current specific problems in orthopedic research, there is a need for clinically relevant mechanobiological models. Animal experiments, especially those on large animals, are costly and, in some cases, doubtful as regards clinical translation. Ex vivo bioreactors that allow biomechanical loading are aimed to mimic the in vivo situation of critical joints that are prone to failure. These tissues often require unique adaptations prior and during organ culture as these are often under mechanical forces in situ. On the one hand, ex vivo organ cultures are limited in regarding the size and cell numbers that can be kept alive and the duration of experiments. However, a strong asset of these cultures is the use of primary human material, which is a chance to provide more translational relevant results. Within this book chapter, we give a brief history of general concepts for bioreactor constructions in the field of orthopedic research and give some recent examples for tendons, the knee joint and the intervertebral disc. We offer a summary of the current state of the art, pitfalls and limitations in the design and the future challenges.