Differential expressions of the lysyl oxidase family and matrix metalloproteinases-1, 2, 3 in posterior cruciate ligament fibroblasts after being co-cultured with synovial cells.

PURPOSE: The adult human posterior cruciate ligament (PCL) has poor functional healing response. The synovial tissue, which surrounds the PCL ligament, might be the major regulator of the microenvironment in the joint cavity after PCL injury, thus affecting the healing process. Here we establish a novel co-culture system for PCL fibroblasts and synovial cells (SC) in vitro to explore the direct influence of paracrine on PCL cells by characterizing the different expressions of the lysyl oxidase family (LOXs) and matrix metalloproteinases (MMP-1, 2, 3), which respectively facilitate extracellular matrix (ECM) repair and degradation.
METHODS: Total RNA was harvested, reverse transcribed and assessed by semi-quantitative PCR and real-time PCR for the expression of LOXs and MMP-1, 2, 3 messenger RNAs. MMP-2 activity was assayed from the collected culture media samples by using zymography.
RESULTS: We found co-culture could promote gene expressions of the LOXs and MMP-1, 2, 3 in normal PCL fibroblasts. But in injured PCL, we found that matrix crosstalk induced an increase of the MMP-1, 2, 3 expressions and a down-regulation of the LOXs.
CONCLUSION: Based on these results, the crosstalk between PCL and SC strongly modified homeostatic balance of ECM and appeared to have a significant impact on PCL wound healing; decreased expression of cross-linking enzymes (LOXs) and increased expression of ECM-degrading proteinases (MMP-1, 2, 3) might be of great contribution to poor healing ability of PCL ligament.