Osteoarthritis (OA) is a debilitating disease of the joints, impacting over 500 million people worldwide. OA affects several load-bearing regions of the body, but specifically within the knee joint, its pathology involves deterioration of several tissues including cartilage, synovium, meniscus, ligaments and bone, ultimately leading to chronic pain, severe inflammation and joint immobility. Despite its large impact on quality of life and the discovery of several disease modifying OA drugs, no clinically approved cure exists.

Aging represents the greatest risk for OA as accumulation of advanced glycation endproducts (AGEs) increase cartilage stiffness, causing chondrocytes to exhibit senescent, inflammatory behavior. We simultaneously captured this biomechanical and biochemical response by treating cartilage explants with 100 mM ribose. Using in silico blind docking simulations, we predicted the in vitro efficacy of anti-aging therapeutics resveratrol and curcumin at suppressing AGE formation and cartilage stiffening, whilst maintaining chondrocyte health.

Another major OA cause is traumatic joint injury, following which, significant inter-tissue biological crosstalk occurs, resulting in immediate elevation of inflammatory cytokines and cartilage matrix degrading enzymes that rapidly accelerate disease onset. To represent this crosstalk in vitro, we developed co-cultures containing combinations of cartilage, synovium and meniscus tissue. In response to catabolic challenge with interleukin-1 (IL1), the synovium exhibited protective effects by lowering nitrite production. Additionally, in presence of synovium, cartilage matrix loss was further suppressed following single administration of receptor antagonist IL-1Ra. Proteomic analysis revealed IL-4, matrilin-3 and carbonic anhydrase III as proteins which may contribute to endogenous IL-1 inhibitor production, explaining the protective effects of synovium.

Finally, achieving long-term benefits of such therapeutics remains challenging due to rapid synovial joint space clearance and an inability of drugs to penetrate through the dense, negatively charged cartilage matrix following their intra-articular administration. Therefore, we synthesized cartilage-targeting and penetrating conjugates using Avidin or Cationic Peptide Carriers for delivering IL-1Ra. A single low dose of each conjugate significantly alleviated long-term IL-1-induced cartilage aggrecan and nitrite release, while rescuing cellular metabolism more effectively than free IL-1Ra. This work can potentially enable clinical translation of various drugs that have failed due to lack of cartilage targeting or systemic toxicity.