Expression of matrix metalloproteinase-1 in cartilage and synovium of traumatic osteoarthritis model in rabbits

Objective To observe the distribution and expression of matrix metalloproteinase-1 (MMP-1) in cartilage and synovium of traumatic osteoarthritis (OA) in anterior cruciate ligament transection (ACLT) of rabbit model and to explore the relation between the MMP-1 expression and the severity of OA. Methods OA was induced in 20 rabbits by ACLT and 10 rabbits killed 4 and 8 weeks respectively after the operation. Other 10 rabbits received unilateral knee arthrotomy as pseudo operative controls and were killed 8 weeks after operation. Synovial changes were grossly checked and OA severity observed under dissecting microscope. Immunohistochemical and morphometric analyses were adopted to record the in situ expression and distribution of MMP-1 in cartilage and synovium at protein level. Results Cartilage degeneration in ACLT group was significantly severer than that in control group (P0.01). Cartilage degeneration in 8-week group was also severer than that in 4-week group (P0.05). MMP-1 expressed predominantly in the superficial and upper intermediate layers of cartilage and in the lining layers of synovium. Its expression increased steadily over the progression of OA in both cartilage and synovium (P0.05). The increase of MMP-1 in synovium lagged behind that of MMP-1 in cartilage in the early stage of OA. Conclusions MMP-1 is closely involved in cartilage degeneration in OA of rabbit ACLT. At the early stage of OA, cartilage degeneration is primarily from self metabolic changes of the cartilage. With OA progression, the synovium also participates in the cartilage degeneration.