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Effects of particulate debris on macrophage-dependent fibroblast stimulation in coculture
M Lind1, M C Trindade, B Yaszay
1Stanford University School of Medicine, California 94305, USA.
Abstract:
The interactions between the different cell types in periprosthetic tissue are still unclear. We used a non-contact coculture model to investigate the effects of polymethylmethacrylate (PMMA) particles and human macrophage-derived soluble mediators on fibroblast activation. Macrophages were either exposed or not exposed to phagocytosable PMMA particles, but fibroblasts were not. Increasing numbers of macrophages were tested in cocultures in which the fibroblast cell number was held constant and cultures of macrophages alone were used for comparison of cytokine release. We used the release of interleukin-1 beta (IL-1beta), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha), lysosomal enzyme and metalloproteinase activity to assess the cultivation of macrophages and fibroblasts. In cocultures, IL-6 release was increased 100-fold for both unchallenged and particle-challenged cultures when compared with macrophage cultures alone. Furthermore, particle-challenged cocultures had threefold higher IL-6 levels than unchallenged cocultures. Release of TNF-alpha was similar in cocultures and in macrophage cultures. IL-1beta release in cocultures was independent of the macrophage-fibroblast ratio. Lysosomal enzyme activity and metalloproteinase activity were increased in cocultures. Our data show that macrophages and fibroblasts in coculture significantly increase the release of IL-6 and to a less degree other inflammatory mediators; particle exposure accentuates this effect. This suggests that macrophage accumulation in fibrous tissue may lead to elevated IL-6 levels that are much higher than those caused by particle activation of macrophages alone. This macrophage-fibroblast interaction represents a novel concept for the initiation and maintenance of the inflammatory process in periprosthetic membranes.
Insights
Cell interactions in periprosthetic tissue are unclear. Macrophages and fibroblasts cocultured significantly increase interleukin-6 (IL-6) release, especially when macrophages encounter polymethylmethacrylate (PMMA) particles, driving inflammation.
Area of Science:
- Biomaterials Science
- Immunology
- Cell Biology
Background:
- Periprosthetic tissue inflammation is a complex process involving various cell types.
- The precise interactions between macrophages and fibroblasts in this environment remain poorly understood.
- Polymethylmethacrylate (PMMA) particles are common wear debris from orthopedic implants, potentially triggering inflammatory responses.
Purpose of the Study:
- To investigate the effects of polymethylmethacrylate (PMMA) particles and macrophage-derived soluble mediators on fibroblast activation using a non-contact coculture model.
- To elucidate the role of macrophage-fibroblast interactions in the release of inflammatory mediators.
- To understand how particle exposure influences these cellular interactions and mediator release.
Main Methods:
- Utilized a non-contact coculture system with human macrophages and fibroblasts.
- Macrophages were exposed to phagocytosable PMMA particles, while fibroblasts were not directly exposed.
- Measured the release of key inflammatory cytokines: interleukin-1 beta (IL-1beta), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-alpha).
- Assessed lysosomal enzyme and metalloproteinase activity as indicators of cellular activation.
Main Results:
- Coculture of macrophages and fibroblasts significantly increased interleukin-6 (IL-6) release by approximately 100-fold compared to macrophages alone.
- Particle-challenged cocultures exhibited threefold higher IL-6 levels than unchallenged cocultures.
- Tumor necrosis factor alpha (TNF-alpha) release was similar across cocultures and macrophage-only cultures.
- Lysosomal enzyme and metalloproteinase activities were elevated in cocultures, indicating heightened cellular activation.
- IL-1beta release was independent of the macrophage-to-fibroblast ratio.
Conclusions:
- Macrophage-fibroblast interactions in coculture markedly enhance IL-6 production and other inflammatory mediators.
- Exposure to PMMA particles further accentuates this inflammatory response.
- Accumulation of macrophages in periprosthetic fibrous tissue may lead to significantly elevated IL-6 levels, contributing to the initiation and maintenance of inflammation.
- This highlights a novel mechanism of macrophage-fibroblast crosstalk in periprosthetic membrane formation and inflammation.