Effects Of Cyclic Pressure At Different Frequencies On The Constructing Of Tissue-engineering Cartilage

Objective:To investigate the effects of cyclic pressure at different frequencies on the constructing of tissue-engineering cartilage in bioreactor.Methods:Articular cartilages were obtained from freshly killed 3-day-old rabbits under sterile environment. And sheared it to the size of about 1mm×1mm×1mm. Then chondrocytes were isolated from the articular cartilage by digesting with 0.25% trypsin and 0.2% typeⅡcollagenase in sequence. 3-dimensional cartilage tissue was produced using PLGA scaffold as a carrier. After expansion in vitro, the 2th passage chondrocytes with a density of 4×10~7/ml were seeded into PLGA scaffolds with the size of 5mm×5mm. All samples were cultured in bioreactor(Celdyne HFB-40). Four different culture conditions were examined: A group(0～200kPa, 0.01Hz), B group(0～200kPa, 0.1Hz), C group(0～200kPa, 1Hz), D group(no pressure, a control group); each group had 10 samples. Each group was cultured for 2 weeks. After 2 weeks, the level of GAG in each sample was measured. Macroscopical analysis, histological analysis, and immunohistochemical analysis were performed.Results:The typeⅡcollagen dyeing area of each group(A,B,C,D) was (67.27±1.65)%,(83.95±2.23)%,(35.35±1.10)%,(40.57±2.06)% respectively. And the content of GAG was (341.00±27.00)μg,(476.33±25.66)μg,(163.33±20.82)μg,(243.67±37.58)μg respectively. There were significant differences of the the typeⅡcollagen dyeing area and the content of GAG among 4 groups(respectively F=478.379, P＜0.01; F=67.402, P＜0.01). The B group was morphologically the thickest, and produced the most GAG and typeⅡcollagen(P＜0.01) in 4 groups, the A group following closedly(P＜0.01), the D group the worst(P＜0.01).Conclusions:The results indicate that the cyclic pressure(0～200kPa, 0.1Hz) best promotes chondrocytes to synthesis and secrete extracellular matrix just as GAG and typeⅡcollagen in 4 groups. This suggests that cyclic pressure at different frequencies have important effects on metabolism of tissue-engineering cartilage.