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Introduction: After any defect, the articular hyaline cartilage is replaced by fibrocartilage which consists of a high concentration of collagen type I and a low content of aggrecan. This composition is contrary to hyaline cartilage (high in collagen type II and aggrecan) and therefore does not match the requirements of the articular pressure load. Until now, there is no successful method to produce a suitable cartilage in vitro. The aim of this study was to determine whether application of hydrostatic pressure to chondrocytes in vitro has a beneficial influence on the expression of extracellular matrix components according to hyaline cartilage.
Materials and Methods: Human articular chondrocytes were pre-cultivated in vitro under standard conditions for 7 days. Afterwards, they were transferred to a bioreactor system applying a hydrostatic pressure of 10 bar for a time period of 1.5, 3, 6 or 12 h. Subsequently, the expression of aggrecan, collagen type I, and collagen type II was investigated and quantified using RT-qPCR. Chondrocytes cultivated exclusively without the application of hydrostatic pressure served as controls.
Results: The chondrocytes under pressure showed almost constant levels of collagen type I and II expression, which were 0.8-fold lower than those of the untreated control group. At the same time the expression of aggrecan holds 1.5–2.5-fold higher values with a pressure duration of1.5 h and 3 h in comparison to 6 h and 12 h. Being compared to the control group aggrecan expression of 1.5 h and 3 h was 1.6–2.4-fold higher, while it was 0.8- fold lower at 6 h and 12 h.
Conclusion: Results show that time matters regarding the application of hydrostatic pressure on chondrocytes in vitro. Particularly the application of 10 bar for 1.5 h- 3 h positively influences chondrocyte0s synthesis of an extracellular matrix towards its composition in hyaline cartilage.