Objective      To investigate the expression of matrix metalloproteinase (MMP)-1

MMP-2 and MMP-3 in posterior cruciate ligament (PCL) fibroblasts co-cultured with synovial cells.       Methods      Human PCL fibroblasts were co-cultured with synovial cells and the monocultures of human PCL fibroblasts and synovial cells were assigned as control. Cell viability and migration were observed by microscopy after 24 h incubation. Total RNA was isolated after 6 h incubation and the expression of MMPs was analyzed by semi-quantitative PCR and quantitative real-time PCR. Gelatin zymography was applied to detect the MMP-2 activity in culture supernatants collected at 1

2 and 3 d after incubation.       Results      As compared with the monocultures

the migration rates of the human PCL fibroblasts and synovial cells in the co-culture increased by (43.1±0.1)% and (76.2±0.2)%

respectively (P0.01). The mRNA expression levels of MMP-1 and MMP-3 in the PCL fibroblasts co-cultured with synovial cells were lower than those in the PCL fibroblasts monoculture. However

PCL fibroblasts-synovial cells interaction significantly increased the expression and activity of MMP-2 in the PCL fibroblasts (P0.05).       Conclusion      The differential expression of MMP-1

MMP-2 and MMP-3 in human PCL fibroblasts co-cultured with synovial cells indicates that cell-cell interaction and cross-talking are associated with PCL fibroblasts wound healing and have potential clinical value for curing injured PCL.