alvocidib and Osteoarthritis

Rapid joint clearance of small molecule drugs is the major limitation of current clinical approaches to osteoarthritis and its subtypes, including post-traumatic osteoarthritis (PTOA). Particulate systems such as nano/microtechnology could provide a potential avenue for improved joint retention of small molecule drugs. One drug of interest for PTOA treatment is flavopiridol, which inhibits cyclin-dependent kinase 9 (CDK9). Herein, polylactide-co-glycolide microparticles encapsulating flavopiridol were formulated, characterized, and evaluated as a strategy to mitigate PTOA-associated inflammation through the inhibition of CDK9. Characterization of the microparticles, including the drug loading, hydrodynamic diameter, stability, and release profile was performed. The mean hydrodynamic diameter of flavopiridol particles was ∼15 µm, indicating good syringeability and low potential for phagocytosis. The microparticles showed no cytotoxicity in-vitro, and drug activity was maintained after encapsulation, even after prolonged exposure to high temperatures (60 °C). Flavopiridol-loaded microparticles or blank (unloaded) microparticles were administered by intraarticular injection in a rat knee injury model of PTOA. We observed significant joint retention of flavopiridol microparticles compared to the soluble flavopiridol, confirming the sustained release behavior of the particles. Matrix metalloprotease (MMP) activity, an indicator of joint inflammation, was significantly reduced by flavopiridol microparticles 3 days post-injury. Histopathological analysis showed that flavopiridol microparticles reduced PTOA severity 28 days post-injury. Taken altogether, this work demonstrates a promising biomaterial platform for sustained small molecule drug delivery to the joint space as a therapeutic measure for post-traumatic osteoarthritis. STATEMENT OF SIGNIFICANCE: Post-traumatic osteoarthritis (PTOA) begins with the deterioration of subchondral bone and cartilage after acute injuries. In spite of the prevalence of PTOA and its associated financial and psychological burdens, therapeutic measures remain elusive. A number of small molecule drugs are now under investigation to replace FDA-approved palliative measures, including cyclin-dependent kinase 9 (CDK9) inhibitors which work by targeting early inflammatory programming after injury. However, the short half-life of these drugs is a major hurdle to their success. Here, we show that biomaterial encapsulation of Flavopirido

Topics: Animals; Biocompatible Materials; Cartilage, Articular; Cyclin-Dependent Kinase 9; Flavonoids; Inflammation; Injections, Intra-Articular; Osteoarthritis; Piperidines; Rats

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.. 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 - a potent and selective inhibitor of Cdk9 kinase activity - to inhibit Cdk9-dependent transcriptional activation, or vehicle control. Global joint metabolomics were analyzed 1 h after injury.. 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.. 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.

Topics: Animals; Anterior Cruciate Ligament Injuries; Cyclin-Dependent Kinase 9; Flavonoids; Joints; Male; Metabolomics; Mice; Mice, Inbred C57BL; Osteoarthritis; Piperidines; Transcriptome