A Novel Bioreactor System Capable of Simulating the In Vivo Conditions of Synovial Joints

Any significant in vitro evaluation of cartilage tissue engineering and cartilage repair strategies has to be performed under the harsh conditions encountered in vivo within synovial joints. To this end, we have developed a novel automated physiological robot reactor system (PRRS) that is capable of recapitulating complex physiological motions and load patterns within an environment similar to that found in the human knee. The PRRS consists of a mechanical stimulation unit (MSU) and an automatic sample changer (ASC) within an environment control box in which the humidity, temperature, and gas composition are tightly regulated. The MSU has three linear (orthogonal) axes and one rotational degree of freedom (around the z-axis). The ASC provides space for up to 24 samples, which can be allocated to individual stimulation patterns. Cell-seeded scaffolds and ex vivo tissue culture systems were established to demonstrate the applicability of the PRRS to the investigation of the effect of load and environmental conditions on engineering and maintenance of articular cartilage in vitro. The bioreactor is a flexible system that has the potential to be applied for culturing connective tissues other than cartilage, such as bone and intervertebral disc tissue, even though the mechanical and environmental parameters are very different. IMPACT STATEMENT: The success of engineered cartilage tissues depends on the biological/biochemical stimulations parameters, which should be as close as possible to the conditions observed in vivo. The design of bioreactors should be, therefore, inspired from the in vivo conditions, rather than the application of one or two degree of freedom loading cycles.