Effects of bionic mechanical stimulation on the properties of engineered cartilage tissue

Tissue-engineered cartilage (TEC) remains a potential alternative for the repair of articular cartilage defects. However, there has been a significant different between the properties of TEC and those of natural cartilage. Studies have shown that mechanical stimulation such as compressive load can help regulate matrix remodelling in TEC, thus affecting its biomechanical properties. However, the influences of shear induced from the tissue fluid phase have not been well studied and may play an important role in tissue regeneration especially when integrated with the compressive load. Therefore, the aim of this study was to quantitatively investigate the effects of combined loading mechanisms on TEC in vitro. A bespoke biosimulator was built to incorporate the coupled motion of compression, friction and shear. The specimens, encapsulating freshly isolated rabbit chondrocytes in a hydrogel, were cultured within the biosimulator under various mechanical stimulations for 4 weeks, and the tissue activity, matrix contents and the mechanical properties were examined. Study groups were categorized according to different mechanical stimulation combinations, including strain (5–20% at 5% intervals) and frequency (0.25 Hz, 0.5 Hz, 1 Hz), and the effects on tissue behaviour were investigated. During the dynamic culture process, a combined load was applied to simulate the combined effects of compression, friction and shear on articular cartilage during human movement. The results indicated that a larger strain and higher frequency were more favourable for the specimen in terms of the cell proliferation and extracellular matrix synthesis. Moreover, the combined mechanical stimulation was more beneficial to matrix remodelling than the single loading motion. However, the contribution of the combined mechanical stimulation to the engineered cartilaginous tissue matrix was not sufficient to impede biodegradation of the tissue with culture time.