[Preliminary studies on repairing osteochondral defects in the rabbit knee joint by using porous PA66/n-HA...

We have investigated the effects of repairing knee osteochondral defects in rabbit by using porous polyamide 66/nano-Hydroxyapatite (PA66/n-HA) combination bone marrow mesenchymal stem cells (MSCs). Eighteen 6-month-old New Zealand rabbits were used to produce the models of 4 mm x 4 mm osteochondral defect in the middle trochlea groove of femur. These models were randomly divided into 3 groups: PA66/n-HA + MSCs Group (Group A), PA66/n-HA group (Group B) and Operation control-group (Group C) in which operation for osteochondral defects was performed but neither material nor cells were implanted. The materials in Group A were seeded with MSCs (5 x 10(5)) in vitro before being implanted in to defects. The materials in groups A and B were 0.5 - 0.8 mm lower than normal cartilage. The animals were killed 1 and 4 months after operation. We assessed the effects by means of macroscopic observation, HE staining, toluidine blue staining, immunohistochemistry assay for type I and type II collagen. Group A displayed a little effect at the 1 month, but at the 4th month, Group A showed better results,compared to Groups B and C. At this time point, the repair tissue of Group A was regular; it presented more metachromatic substance visualized by toluidine blue staining, and it expressed type II collagen(+ +) and type I collagen(+). These results demonstrate that the repair tissue in Group A is nearly hyaline cartilage. So we presume that porous PA66/n-HA provides biomechanical support, and at the same time, MSCs enhance the repair effects.