To examine the in vivo effects of carboxymethylated chitin (CMC), intra-articularly administered, on cartilage degradation and the level and distribution of cartilage matrix metalloproteinase-1 (MMP-1).
Osteoarthritis (OA) was induced in 20 rabbits by unilateral anterior cruciate ligament transection (ACLT). The experimental group, comprising 10 rabbits randomly selected, was given an intra-articular injection of 0.3 ml of 2% CMC solution at 1, 3, and 5 weeks after ACLT. A further 10 rabbits that received an intra-articular injection of 0.3 ml normal saline at the same time served as controls. All knees were harvested at 6 weeks after surgery. Cartilage degradation of femoral condyles was evaluated at two levels: macroscopic and light microscopic. Tissue level and distribution of MMP-1 was documented by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry.
Cartilage degradation in the control group was significantly more severe than that in the experimental group both on the macroscopic grading scale and on Mankin's grading scale. In RT-PCR the amount of MMP-1 was significantly reduced by the treatment of CMC. Immunohistochemical study showed that in the experimental group MMP-1 was predominantly expressed in the superficial and upper intermediate layers of cartilage, and the amount of MMP-1 in the experimental group was also lower than that in control group.
CMC significantly reduces the severity of cartilage degradation and reduces the expression of MMP-1 in cartilage, both at the mRNA and the protein level, and thus may be a potential drug for the treatment of OA.