OBJECTIVETo trace the pathological changes of the cultured autologous chondrocytes mass after implanted in cartilage defects and investigate the pathophysiological mechanisms of the antologous chondrocytes mass transplantation in the repair of cartilage defects.

METHODSTwenty-four New Zealand white rabbits of 4 to 6 month-old and weighing more than 3.0 kg (female and male was unrestricted) were randomly divided into experiment group and the control group. For 12 rabbits of experiment group, the cartilage defects were repaired with the autologous chondrocytes mass and sealed with one piece of periosteum. Firstly, cartilage tissue of 10 to 30 mg was obtained from the shoulder of the rabbits after anaesthetized by 1 mg/kg 20% sumianxin. Then, chondrocytes were isolated from the cartilage tissue with 0.2% type II collagenase digestion and were cultured in DMEM/F-12 supplemented with 20% fetal bovine serum (FBS), 50 microg/ml ascorbic acid-2-phosphate, 0.4 mM proline, 5 microg/ml insulin and 1 mM non-essential amino acids (NEAA) in flasks in vitro. The cells were harvested until a thin film of the cells covered the bottom of the flask could be seen with naked eyes. Then the film was collected with a curled glass stick and formed a solid mass. On this time, the animal was anaesthetized again and the full-thickness cartilage square defect of 4.0 mm x 6.0 mm was fabricated in the patellar grove of distal femur, and then the cellular mass was transplanted into the defect covered by one piece of periosteum which obtained from the upper anterior of tibia and sealed with the femoral condyles. For 12 rabbits of the control group, the defects were sealed with one piece of periosteum only. The animals were sacrificed in the 1st, 3rd, 6th and 12th weeks after the operation respectively. The histologic sections were stained with safranin O-fast green, hematoxylin-eosin (H&E) and picric acid-Sirius red and immunostained for type II collagen and aggrecan.

RESULTSIn the 1st week, the transplanted cells oriented to articular surface differentiated to matured hyaline chondrocytes and excrete large amount cartilage matrix. In the 3rd week, the trend was more obvious and the periosteum was union to the cell mass. In the 12th week, the defects were repaired with hyaline-like cartilage tissue, and in the 24th week, the repair tissue turned to matured hyaline cartilage. In the control group, the defects were repaired with fibrocartilage tissues.

CONCLUSIONIt was evidenced that the defects were repaired by the autologous chondrocytes mass transplantation. The procedure was gradual and initialed from up toward joint to down to the deep of the defect.