Injectable sustainable andrographolide-releasing hydrogel for long-lasting alleviation of osteoarthritis and regulation of chondrocyte autophagy via PRKCA/EGFR

Osteoarthritis is one of the most prevalent age-related joint diseases, with chondrocyte inflammation and autophagy dysregulation serving as pivotal pathogenesis factors. Andrographolide (AD), a phytochemical identified in Andrographis paniculata, exhibits anti-inflammatory properties and regulates autophagy to safeguard cells from damage. Nevertheless, the precise mechanism underlying the influence of AD on autophagy in osteoarthritis (OA) chondrocytes remains unelucidated. Concurrently, sustained efficacy of andrographolide typically necessitates prolonged administration, posing a challenge for its clinical application. We engineered an injectable 4-arm PEG-Mix-Hydrogel/PF system capable of encapsulating lipophilic drugs and achieving sustained release over a period of up to 24 days, substantially reducing the frequency of medication. Our findings indicate that andrographolide augments chondrocyte autophagy via the PRKCA/EGFR pathway and modulates chondrocyte inflammation as well as extracellular matrix degradation. Subsequent experimentation revealed that the injectable 4-arm PEG-Mix-Hydrogel/PF@AD (PHPF@AD) exhibited excellent biocompatibility with chondrocytes, possessed a rapid in-situ gelation time, and a single injection was sufficient to alleviate joint degeneration, abnormal gait, and weakened chondrocyte autophagy in OA mice, while ameliorating inflammation, matrix degradation, and apoptosis levels, and maintaining a certain degree of bone mass around the joints. In summary, this injectable hydrogel with spontaneous andrographolide release is anticipated to be a promising therapeutic modality for OA. • Experimental findings demonstrate that andrographolide (AD) promotes chondrocyte autophagy in osteoarthritis (OA) through the PRKCA/EGFR pathway. Simultaneously, it mitigates joint tissue damage and concurrently reduces inflammation, extracellular matrix degradation, and apoptosis. These results establish AD as a potentially valuable natural compound for OA treatment, thereby elucidating the hitherto unknown mechanism of AD in alleviating OA by enhancing autophagy. • The hydrogel-micelle composite creates an ideal microenvironment for the slow-release of hydrophobic AD. It prevents burst-type drug release, avoiding poor efficacy and side-effects. The injectable PHPF@AD system can sustain drug release for over 24 days, solving the problem of frequent AD administration in prior studies. Additionally, this system exhibits excellent biocompatibility and biosafety with cartilage tissue, essential for cartilage-related therapies. • The injectable PHPF@AD system, with a single administration, can provide continuous treatment for OA mice induced by destabilization of the medial meniscus (DMM) surgery over a period of 24 days. It significantly alleviates the abnormal gait and joint tissue damage in OA mice and, to a certain extent, reduces bone loss.