[Suppression of articular cartilage breakdown in osteoarthritis by interleukin-1 receptor antagonist using ex vivo gene therapy]

Abstract

Objective: To explore the role of interleukin-1 receptor antagonist (IL-1Ra) in suppression of cartilage matrix degradation and pathologic changes.

Methods: Thirty New Zealand White rabbits underwent partial synovectomy of the left knee. Synovial fibroblasts were isolated and cultured. The rabbits underwent anterior cruciate ligament transection (ACLT) in the right knee. After the ACLT the rabbits were forced to run 4 hours a day for 4 weeks so as to establish the osteoarthritis (OA) model. Three days after the ACLT the rabbits were randomly divided into 3 groups of 10 rabbits: group 1, to be injected with the cultured autologous synovial fibroblasts into the right knees; group 2, injected with the autologous synovial fibroblasts transfected with marker gene, and group 3, injected with autologous synovial fibroblasts transfected with IL-1Ra gene. Two and 4 weeks after the injection 5 rabbits in each group were killed respectively. Their right knee joints were lavaged and the lavage fluid was extracted. IL-1Ra level in the synovial fluid (SF) was determined by ELISA. 20 mg of articular cartilage were taken from the condyle of right femur and digested by papain. The glycosamino-glycan (GAG) level in the SF and in the cartilage digest were evaluated using dimethylmethylene blue assay. Two pieces of cartilage were taken from each rabbit's and were sliced and stained to undergo pathologic changes.

Results: The IL-1Ra level in the SF of the group 3 was (20.2 +/- 1.8) ng/ml 2 weeks after, and was (4.8 +/- 0.5) ng/ml 4 weeks after, significantly lower than those in the group 2 (84 +/- 7) micro g/ml and group 3 (84 +/- 6) micro g/ml IL-1Ra was not detected in the SF of the group 1. The GAG level in SF was 40.1 micro g/ml with an inhibitory rate of 56.2%, and those in the group 2 and group 3 were 30.2 micro g/mg and 10.8 micro g/mg respectively. The GAG levels 4 weeks after in the cartilage digest of the group 1 and group 2 were (10.1 +/- 1.2) micro g/mg and (10.8 +/- 0.9) micro g/mg respectively, both significantly lower than that in the group 3 [(30 +/- 3) micro g/mg, both P < 0.05]. Pathological examination showed that the articular cartilage of the left knee was all normal in all the rabbits. However, obvious damage was found in the articular cartilage of the right knees of all the rabbits. However, the damage in the group 3 was significantly milder than that in the other 2 groups.

Conclusion: Intraartilcular injection of synovial cells transfected with IL-1Ra gene can suppress articular cartilage matrix degradation and pathologic changes.