Inhibition of early response genes prevents changes in global joint metabolomic profiles in mouse post-traumatic osteoarthritis

Abstract

Objective: Although joint injury itself damages joint tissues, a substantial amount of secondary damage is mediated by the cellular responses to the injury. Cellular responses include the production and activation of proteases (MMPs, ADAMTSs, Cathepsins), and the production of inflammatory cytokines. The trajectory of cellular responses is driven by the transcriptional activation of early response genes, which requires Cdk9-dependent RNA Polymerase II phosphorylation. Our objective was to determine whether inhibition of cdk9-dependent early response gene activation affects changes in the joint metabolome. Design: To model post-traumatic osteoarthritis, we subjected mice to non-invasive Anterior Cruciate Ligament (ACL)-rupture joint injury. Following injury, mice were treated with flavopiridol e a potent and selective inhibitor of Cdk9 kinase activity e to inhibit Cdk9-dependent transcriptional activation, or vehicle control. Global joint metabolomics were analyzed 1 h after injury. Results: We found that injury induced metabolomic changes, including increases in Vitamin D3 metabolism, anandamide, and others. Inhibition of primary response gene activation immediately after injury largely prevented the global changes in the metabolomics profiles. Cluster analysis of joint metabolomes identified groups of injury-induced and drug-responsive metabolites. Conclusions: Metabolomic profiling provides an instantaneous snapshot of biochemical activity representing cellular responses. We identified two sets of metabolites that change acutely after joint injury: those that require transcription of primary response genes, and those that do not. These data demonstrate the potential for inhibition of early response genes to alter the trajectory of cell-mediated degenerative changes following joint injury, which may offer novel targets for cell-mediated secondary joint damage.

Subchondral bone and synovial fluid metabolomic profiles are altered in injured and contralateral limbs 7 days after non-invasive joint injury in skeletally-mature C57BL/6 mice

“…Metabolomic profiles were also similar between injured and contralateral-to-injured limbs. Our study contributes to a growing body of work that demonstrates that distinct shifts occur in synovial fluid metabolism in the first week post joint injury 25 and are consistent with shifts in whole joint metabolism 44 . Synovial fluid metabolic changes are driven by dysregulation of cartilage and bone metabolism following joint injuries 19 .…”

Cannabinoid-based therapy as a future for joint degeneration. Focus on the role of CB2 receptor in the arthritis progression and pain: an updated review

“…AEA and 2-AG levels were augmented in the synovial fluid of dogs with OA [115]. AEA was also elevated in the joint in a posttraumatic OA mouse model [116]. In contrast to those in healthy volunteers, AEA and 2-AG have been detected in the synovial fluid of OA and RA patients [72].…”

Alternations of Metabolic Profiles in Synovial Fluids and the Correlation with T2 Relaxation Times of Cartilage and Meniscus—A Study on Anterior Cruciate Ligament- (ACL-) Injured Rabbit Knees at Early Stage

“…The authors demonstrated that it was possible to distinguish between ACL surgical samples after 2 weeks and nonsurgical ones, based on their different metabolic signatures [3]. In another study, June et al induced noninvasive ACL injury in mice by applying a mechanical load to their ankles and investigated the resultant metabolic alterations in microdissected joint tissues following ACL injury by HPLC-MS. Their results showed that the ACL injury caused a broad range of metabolic changes, including the upregulation of retinoid metabolism, phospholipid biosynthesis, hydroxyproline degradation, and anandamide metabolism [19]. Similar metabolomics studies have also been performed on the synovial fluid samples obtained from patients with osteoarthritis or rheumatoid arthritis [20, 21].…”