Cyclic compressive loading on 3D tissue of human synovial fibroblasts upregulates prostaglandin E2 via COX-2 production without IL-1β and TNF-α

Abstract

ObjectiveExcessive mechanical stress on synovial joints causes osteoarthritis (OA) and results in the production of prostaglandin E2 (PGE2), a key molecule in arthritis, by synovial fibroblasts. However, the relationship between arthritis-related molecules and mechanical stress is still unclear. The purpose of this study was to examine the synovial fibroblast response to cyclic mechanical stress using an in vitro osteoarthritis model.MethodHuman synovial fibroblasts were cultured on collagen scaffolds to produce three-dimensional constructs. A cyclic compressive loading of 40 kPa at 0.5 Hz was applied to the constructs, with or without the administration of a cyclooxygenase-2 (COX-2) selective inhibitor or dexamethasone, and then the concentrations of PGE2, interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α), IL-6, IL-8 and COX-2 were measured.ResultsThe concentrations of PGE2, IL-6 and IL-8 in the loaded samples were significantly higher than those of unloaded samples; however, the concentrations of IL-1β and TNF-α were the same as the unloaded samples. After the administration of a COX-2 selective inhibitor, the increased concentration of PGE2 by cyclic compressive loading was impeded, but the concentrations of IL-6 and IL-8 remained high. With dexamethasone, upregulation of PGE2, IL-6 and IL-8 was suppressed.ConclusionThese results could be useful in revealing the molecular mechanism of mechanical stress in vivo for a better understanding of the pathology and therapy of OA.Cite this article: Bone Joint Res 2014;3:280–8.

Early OA Stage Like Response Occurs after Dynamic Stretching of Human Synovial Fibroblasts

“…Our results indicate that short-term high-frequency cyclic tensile strain induced a mechanical stress response, as a significant increase in the inflammatory and innate immune response activating marker IL-6 could be detected. This concurs with previous findings applying pressure on fibroblasts [24,48]. Interestingly, the application of the dynamic stretching protocol had beneficial effects on IL-6 expression in synovial fibroblasts, contrary to chondrocytes [23].…”

“…In general, in vitro experiments suffer from inadequate simulation of in vivo situations, especially when mimicking movement and the effect of mechanical strain on cells. For this reason, various protocols and applications are published aiming to overcome this issue [21][22][23][24].…”

Activation of calcitonin gene-related peptide signaling through the prostaglandin E2-EP1/EP2/EP4 receptor pathway in synovium of knee osteoarthritis patients

“…In contrast, exogenously added TNF-α and IL-1β stimulated CGRP expression in vitro, but no significant correlation was detected between TNF-α- or IL-1β-induced CGRP mRNA expression levels in the synovial tissue from knee joints of OA patients. In a recent study, Nakata et al [ 21 ] demonstrated that cyclic compressive loading on a 3D-cultured construct of human synovial fibroblasts upregulates PGE2 and COX-2 in the absence of IL-1β or TNF-α stimulation. These results suggest that CGRP may be regulated by PGE2 in an IL-1β- and TNF-α-independent manner in the synovium of OA patients.…”

Differential expression of COX-2 in osteoarthritis and rheumatoid arthritis

“…Studies have demonstrated the physiological role of COX-1 in the body's normal metabolism and protection by the release of prostaglandin, while COX-2 has been recognized as an inducible or pathological enzyme that can be induced by various chemical/physical injuries or biological factors. COX-2 also participates in the inflammatory response by facilitating prostaglandin synthesis (Lee et al, 2014b;Shimomura et al, 2014). The pathogenesis of OA or RA is not well-understood, although abnormal expression of certain genes or proteins has been found to be correlated with the occurrence of these diseases to some degree.…”