Rabbit Articular Cartilage Defect Treated With Cultured Chondrocytes Embedded In Self-setting Calcium Phosphate/Fibrin Gel Two-Phase Scaffold

Objective 1) To evaluate the effectiveness and feasibility of the cultured articular cartilage chondrocytes embedded in CPC/FG two-phase scaffold to repair rabbit articular cartilage defect based on tissue engineering. 2) To explore the effect of temporary substitution of subchondral bone by porous self-setting Calcium Phosphate (as a part of the two-phase scaffold) in the period of reparing. 3) To study the effectiveness of secure fixation of the scaffold-chondrocytes complex using the porous self-setting Calcium Phosphate directly press fitting into subchondral bone.Methods 1) The third passaged chondrocytes were harvested and embedded in the two-phase scaffolds' fibrin gel with a final cell density of 2.5 107/ml. After the scaffold-chondrocytes complexes were cultured for 1 week in vitro, the gross and light microscopic examination was performed to observe the chondrocytes morphology and the carriers' absorption. 2) The complex of chondrocytes-scaffold was transplanted to repair the articular cartilage defects of femoral condyle of rabbit knees (the defects were 4mm in diameter,3.5mm in depth, extending down to the subchondral bone). 3) A total of 18 rabbits were randomly divided into three groups: In group A, the defects of the left knees were transplanted with the complexes of CPC/FG-chondrocytes (experimental group), the defects of the right knees were transplanted with the pure CPC/FG(control group 1); In group B, the defects of the left knees were transplanted with the complexes of FG-chondrocytes(control group 2), the defects of the right knees were left empty(blank control group); In group C, the total defects were transplanted with the complexes of CPC/FG- chondrocytes(detected the collagen content 12 weeks after transplantation). 4) Atthe 4th 8th, 12th weeks postoperation, the rabbits were sacrificed respectively. The healing of defects were assessed by gross examination, light microscope, transmission electron microscope, and histologically scored. In addition, the collagen content of the healing cartilages in the 12th week after transplantation and of the normal cartilages were detected and compared.Results 1) Cultured in vitro, the passaged chondrocytes embedded in the two-phase scaffolds' fibrin gel grew well and maintained the characteristic chondrocyte morphology, excreted the matrix. The FG maintained original shape. 2) The complex of chondrocytes-scaffold grew well in vivo. After 8 weeks and later than that, the neocartilages were matured and FG were almost completely degraded. At 12th week, the articular cartilage defects were repaired by hyaline cartilage. In control group, the defects were repaired only by fiber tissue. The difference of histological scores between experimental groups and control groups was statistically significant. 3) The collagen content of healing cartilage 12 weeks after transplantation was (43.25 + 0.57)%, and the content of normal cartilage was (51.96 0.46)%,The difference between the two groups was statistically significant. 4) At 12 weeks after operation, the CPC was scarcely degraded, and incorporated with subchondral bone closely.Conclusions 1) The two-phase scaffold of CPC;FG embedding chondrocytes can repairsuccessfully the cartilage defects of femoral condyle of rabbit knee in the mode of hyalinecartilage. 2) The porous self-setting Calcium Phosphate can temporarily substitute thesubchondral bone in the period of reparing. 3) The porous self-setting Calcium Phosphatedirectly press fitting into subchondral bone can securely fix of the scaffold-chondrocytescomplexes.