Intra-Articular Delivery of Quercetin Using Thermosensitive Hydrogel Attenuate Cartilage Degradation in an Osteoarthritis Rat Model.

Quercetin (Que), a bioflavonoid, is both anti-inflammatory and antioxidative. Que has been used as an oral supplement for osteoarthritis (OA) with inconsistent findings because of its low bioavailability. We encapsulated Que in a mPEG-polypeptide thermogel to prolong its bioactivity. The efficacy of this formulation was evaluated in a posttraumatic OA rat model. Methoxy-poly(ethylene glycol)-l-poly(alanine) (mPEG-PA) polymer was synthesized and characterized in terms of cytotoxicity and release kinetics in vitro. At 12 weeks old, Sprague-Dawley rats underwent anterior cruciate ligament transection (ACLT). At 24 weeks post-operation, rats received either an intra-articular (IA) injection of saline, hydrogel, or hydrogel with Que (50 or 500 μg). Gait analysis was performed at pre-ACLT, pre-treatment, and at 4, 8, and 12 weeks post-treatment. At 12 weeks post-treatment, knee joints were collected for histopathological evaluation. In vitro studies showed that chondrocytes were viable after 72 hours of incubation with mPEG-PA, and the release of Que could be sustained for >28 days. Among all OA rats, the limb idleness index (LII) were significantly increased at 24 weeks post-ACLT. Rats that received hydrogel with Que (50 μg) showed the most reduction in LII at both 4 and 8 weeks post-treatment. The Osteoarthritis Research Society International score of rats received hydrogel with Que (50 μg) was significantly lower than the control group. All rats suffered from low-grade synovitis (Krenn score: 2-4). This study suggests that a sustained delivery of Que (50 μg) could provide symptom relief and also delay the progression of OA in the knee.