Intra-articular injection of flavopiridol-loaded microparticles for treatment of post-traumatic 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.

小分子药物在关节内的快速清除，是目前骨关节炎及其亚型（包括创伤后骨关节炎，PTOA）临床治疗方法的主要局限。纳米/微技术等微粒系统，有望为提高小分子药物在关节内的留存提供一条潜在途径。一种用于治疗PTOA的目标药物是黄酮吡醇，它可抑制细胞周期蛋白依赖性激酶9（CDK9）。在此，我们制备了包裹黄酮吡醇的聚乳酸 - 羟基乙酸共聚物微粒，对其进行了表征，并评估了通过抑制CDK9来减轻PTOA相关炎症的策略。对微粒进行了包括载药量、流体动力学直径、稳定性和释放曲线等方面的表征。黄酮吡醇微粒的平均流体动力学直径约为15μm，表明其具有良好的可注射性且被吞噬的可能性较低。这些微粒在体外无细胞毒性，即使长时间暴露在高温（60°C）下，包封后的药物活性依然得以保持。在大鼠PTOA膝关节损伤模型中，通过关节内注射给予负载黄酮吡醇的微粒或空白（未负载）微粒。与可溶性黄酮吡醇相比，我们观察到黄酮吡醇微粒在关节内有显著留存，证实了微粒的缓释特性。损伤后3天，作为关节炎症指标的基质金属蛋白酶（MMP）活性，被黄酮吡醇微粒显著降低。组织病理学分析显示，损伤后28天，黄酮吡醇微粒减轻了PTOA的严重程度。综上所述，这项研究展示了一个有前景的生物材料平台，可将小分子药物持续递送至关节腔，作为创伤后骨关节炎的一种治疗手段。