Investigating the influence of synovium on cartilage response to inflammatory stimuli using predictive in vitro models
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Inflammatory joint diseases, such as rheumatoid arthritis and osteoarthritis, constitute a significant economic and social burden. Currently there are very few disease modifying treatments, the search for which is hampered by an incomplete understanding of disease processes and the lack of appropriate human in vitro models. The chondrocyte response to pro-inflammatory cytokines is known to play an important role in the aetiology of cartilage degradation. Increasing evidence suggests that the communication between the synovium and articular cartilage contributes to the onset, progression, and symptomatic presentation of inflammatory joint diseases. However, the precise nature of this interaction has yet to be fully established. Understanding the intricate interplay between cartilage and synovium with the inflammatory joint environment is crucial for developing effective therapeutic strategies. We hypothesize that the cells of the synovium influence the inflammatory response of chondrocytes through paracrine signalling. To address this hypothesis, we carried out a number of in vitro experiments using bovine, and subsequently human, primary fibroblast-like synoviocytes (FLS) and primary chondrocytes. These studies employed both conditioned media and co-culture methods with chondrocytes cultured in both 2D, 3D and explant models. The response to the pro-inflammatory cytokine IL-1β, was assessed in terms of the release of pro-inflammatory and catabolic mediators nitric oxide and PGE2. as well as downstream effects on cartilage matrix degradation. The study also examined the effects of mechanical stimulation of FLS on subsequent regulation of chondrocyte response to IL-1β. In both, bovine and human models, our findings indicate that the presence of FLS, or FLS-derived conditioned media (CM), modulated the chondrocyte inflammatory response to exogenous IL1β. Interestingly, for PGE2 release, an opposite modulation was found comparing bovine and human donors. In bovine cells, FLS conditioned media exacerbated the chondrocyte response to IL1β where as a reduced response was observed in human cartilage cells treated with FLS conditioned media. The differences in the response were attributed to the species differences as opposed to donor age or disease state. Furthermore, in human cells we identified differences between the different donors in terms of the effects of FLSM CM on chondrocyte catabolic gene expression under exogenous IL1β stimulation. These differences were associated with differences in the release of cytokine from the FLS. The inherent donor differences enabled identification of specific cytokines released by FLS which are likely to be responsible for paracrine regulation of chondrocyte response to IL1β. In summary this thesis identifies the modulation by FLS of the chondrocyte response to pro-inflammatory cytokines and how this is further influenced by physiological mechanical loading of the synoviocytes. Important differences are revealed between bovine and human cells. Finally using a sample of human donors, the study identifies likely paracrine mediators released by FLS which may represent potential therapeutical targets for controlling inflammatory joint disease. The study highlights the importance of including both cell types within predictive in vitro models of inflammatory joint disease whilst identification of donor specific responses opens the way for personalized in vitro models which may be used for patient stratification and personalized medicine
Authors
Jurado Terrazas, DACollections
- Theses [4248]