Oleanolic acid cubic liquid crystal nanoparticle-based thermosensitive gel attenuates knee osteoarthritis symptoms in rats.

Background: Knee osteoarthritis (KOA) is a prevalent degenerative joint disease with limited effective treatment options. Oleanolic acid (OA) possesses promising anti-inflammatory and cartilage-protective properties, but its clinical application is hindered by poor solubility and rapid metabolism. Purpose: This study aimed to develop an oleanolic acid-loaded liquid crystalline nanogel (OANG) for intra-articular delivery and to systematically evaluate its therapeutic effects and potential mechanisms in a rat KOA model. Methods: OA-loaded nanoparticles were prepared and incorporated into a thermosensitive Poloxamer gel base to form OANG. A papain-induced KOA rat model was established. Rats were administered OANG (high/low dose) intra-articularly, with celecoxib as a positive control. Evaluations included behavioral tests, micro-computed tomography, histological analyses (hematoxylin and eosin, transmission electron microscopy, immunohistochemistry), enzyme-linked immunosorbent assay of synovial fluid, serum, and hippocampus, Western blot (WB), network pharmacology, and molecular docking. Results: OANG exhibited sustained-release properties and improved joint lubrication. Treatment with OANG significantly alleviated KOA-induced pain and depression-like behaviors, reduced cartilage degradation and subchondral bone sclerosis, and downregulated levels of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6) and cartilage degradation markers (C-terminal cross-linked telopeptide of type II collagen, cartilage oligomeric matrix protein) in synovial fluid. It also enhanced antioxidant capacity (increased superoxide dismutase, glutathione peroxidase; decreased malondialdehyde) and modulated the expression of key cartilage proteins (increased Collagen II; decreased matrix metalloproteinase 13; regulated glycogen synthase kinase-3β/SRY-box transcription factor 9, β-catenin, and Yes-associated protein). Furthermore, OANG ameliorated hippocampal oxidative stress and inflammation (decreased Cleaved caspase-3, Malondialdehyde; increased IL-10). Network pharmacology and docking suggested the involvement of peroxisome proliferator-activated receptor gamma, mitogen-activated protein kinase 3, prostaglandin-endoperoxide synthase 2, and pathways such as estrogen signaling and cyclic adenosine monophosphate signaling.