Effect of synovial membrane infection in vitro on equine synoviocytes and chondrocytes.

The research investigates how bacterial infection in synovial membranes impacts the function of synoviocytes and chondrocytes in horses. The results show a decrease in hyaluronan concentration and an increased release of certain mediators during bacterial infection, which is retained even after the elimination of bacteria. This response also contributes to damage in the articular cartilage.

Research Methodology

• In this study, synovium and articular cartilage explants were extracted from the midcarpal and tarsocrural joints of adult horses.
• Two main experiments were carried out. For the first experiment, synovium explants were exposed to different conditions: regular incubation (control), infection with Staphylococcus aureus bacteria (I), and incubation with medium obtained from infected group and then filtered (IF).
• The medium collected daily was then checked for concentrations of interleukin 1 beta, interleukin-6, tumor necrosis factor, and hyaluronan.
• In the second experiment, cartilage explants were incubated with standard medium (control) and medium collected from infected synovium cultures and filtered (IF).
• After 48 hours, the synthesis of proteoglycan in the explant, as well as the endogenous proteoglycan and glycosaminoglycan content, were measured.

Key Findings

• The research found that the concentrations of interleukin-1 beta and interleukin-6 were significantly increased in synovium explants from the infected and infected-filtered groups.
• Conversely, hyaluronan concentration was found to be lower in the infected and infected-filtered groups.
• The synthesis of proteoglycan, along with the total glycosaminoglycan and chondroitin sulfate concentrations, significantly decreased in cartilage from the infected-filtered group.
• The researchers concluded that a bacterial infection resulted in decreased hyaluronan concentration and increased mediator release, even when the bacteria were eliminated.
• Additionally, exposure to a medium that was sterile but had been previously infected led to a decrease in the synthesis and the composition of the articular cartilage matrix.

Implications

• This study suggests that synovial cells residing in the synovium can contribute to damage in the articular cartilage during a bacterial infection, even in the absence of migrant inflammatory cells.
• Significantly, this adverse response lingers even after the elimination of bacteria.
• The findings may have important implications for understanding and treating joint infections and degenerative joint diseases in horses and potentially other species.