Rational development of intra-articular drug delivery systems for the treatment of osteoarthritis

Osteoarthritis (OA) is a debilitating joint disease characterized by progressive cartilage degradation and calcification, synovitis, and subchondral bone sclerosis, resulting in pain and functional impairment. OA pathogenesis is multifactorial with mechanical (wear and tear) and biochemical components that converge on the progressive cartilage destruction mainly orchestrated by inflammatory cytokines and catabolic enzymes. Current therapies provide only temporary relief from symptoms, and no disease-modifying OA drugs (DMOADs) are clinically available. Clinically approved intra-articular OA therapies include corticosteroids to manage pain and inflammation and hyaluronic acid (HA) to restore cartilage lubrication. However, several clinical trials revealed that this approach is associated with several limitations, including rapid clearance from the joint space. Therefore, there is an unmet clinical need for precision medicines capable of both extending the retention of drugs within the osteoarthritic joint and addressing the underlying causes of cartilage degradation. An optimal approach in precision medicine for OA involves the synergistic combination of a drug delivery system (DDS) with a disease-modifying osteoarthritis drug. In the present research project, various strategies were employed to develop intra-articular DDS containing potential DMOADs. Three therapeutic approaches were investigated to target distinct aspects of OA pathology: cartilage lubrication failure, pathological cartilage calcification, and the accumulation of senescent cells in osteoarthritic joints. Reduced cartilage lubrication is a key factor in OA, which causes increased friction between cartilage interfaces, triggering further cartilage degradation and local inflammation. Thus, early-stage restoration of cartilage lubrication could ameliorate, and potentially reverse, OA. Within this context, the first study presents a methodology for producing injectable cross-linked HA hydrogel microparticles (uHP) tailored for localized OA treatment. Leveraging the crucial lubricant role of HA in the cartilage and synovial fluid, HA-μHP were designed to function not only as a bioinspired lubricant but also as a platform for drug delivery. HA-methacrylate (10 or 50 kDa) precursors with different degrees of methacrylation were employed to generate these hydrogel microparticles, combining a template strategy and multi-step photo-polymerization. This process yielded HA-μHP with a square base measuring 20 μm on each side and a height of 5 μm. The developed method enabled the fine-tuning of particle properties and the loading of diverse payloads, including small molecules, macromolecules, and nanoparticles. Using a linear two-axis tribometer (designed and constructed in the Tribology Laboratory at the Azrieli College of Engineering in Jerusalem), we assessed the static and dynamic friction coefficients of the μHP-enriched simulated synovial fluid. Notably, both friction coefficients exhibited a consistent decrease in the presence of HA-μHP, underscoring the lubricating efficacy of HA, even in the form of microparticles. Under conditions simulating OA oxidative stress (0.3 mM H2O2), these particles exhibited no degradation, emphasizing the advantages of the HA formulation in hydrogel microparticles over bulk hydrogels. Also, the biocompatibility of HA μHP with various cell types, including chondrocytes and fibroblasts – key components of the joint capsule was confirmed, further supporting the potential of this approach for OA treatment. Cartilage calcification is another hallmark of OA because calcium crystals released by chondrocytes promote cartilage degradation via different pathways. Consequently, the inhibition of calcification and prevention of subsequent events can potentially block cartilage deterioration. In the second study, Fetuin, a hepatically synthesized glycoprotein known for its endogenous calcification inhibition and anti-inflammatory properties, was chosen as a therapeutic agent. Two distinct delivery strategies for Fetuin were proposed, either for combinatorial therapy or enhanced drug retention. Fetuin has been effectively nanoformulated with the natural anti-inflammatory fatty acid methyl palmitate, resulting in stable 200 nm nanoparticles (MPN), creating a dual-anti-inflammatory system. Also, Fetuin was incorporated into HA-μHP through a charge-based (ionic) interaction. This platform enabled a sustained delivery of the protein over 30 days in a biologically relevant volume. In vitro studies conducted on human chondrocytes demonstrated that both formulations significantly reduced H2O2-calcium crystals-mediated inflammation, with a more pronounced beneficial effect compared to Fetuin alone. This highlighted the advantageous nature of our strategy, which exploits the benefits of combinatorial therapy with MPN and drug depot with HA-μHP. The final part of this research work, conducted at Vanderbilt University, was focused on a therapeutic target that has drawn significant attention in recent years—namely, the accumulation of senescent cells in OA joints. Targeting senescence through the application of senolytic and senomorphic drugs has emerged as a promising strategy for modifying the disease and addressing OA causes. In the latest research activity, senescence-modulating drugs were effectively encapsulated with high drug-loading capacities within ROS-responsive polysulfide nanoparticles. Two separate in vitro models were utilized to evaluate their effectiveness. Among the senolytic drugs investigated, NVP-CMG097 (MDM2 inhibitor) demonstrated moderate selectivity in eliminating senescent fibroblast-like synoviocytes. Concurrently, senomorphic drugs 114810 and GSK343 exhibited promise in reducing inflammation and cartilage degradation within a 3D model of OA. These results underscore the potential of utilizing this class of drugs as innovative therapeutic agents, thereby paving the way to explore the co-delivery of these drugs using advanced drug delivery systems

Tribological behavior of shape-specific microplate-enriched synovial fluids on a linear two-axis tribometer

Abstract Nano- and micro-particles are being increasingly used to tune interfacial frictional properties in diverse applications, from friction modifiers in industrial lubrication to enhanced biological fluids in human osteoarthritic joints. Here, we assessed the tribological properties of a simulated synovial fluid enriched with non-spherical, poly lactic-co-glycolic acid (PLGA) microparticles (µPL) that have been previously demonstrated for the pharmacological management of osteoarthritis (OA). Three different µPL configurations were fabricated presenting a 20 µm × 20 µm square base and a thickness of 5 µm (thin, 5H µPL), 10 µm (10H µPL), and 20 µm (cubical, 20H µPL). After extensive morphological and physicochemical characterizations, the apparent Young’s modulus of the µPL was quantified under compressive loading returning an average value of ∼ 6 kPa, independently of the particle morphology. Then, using a linear two-axis tribometer, the static (µ s) and dynamic (µ d) friction coefficients of the µPL-enriched simulated synovial fluid were determined in terms of particle configuration and concentration, varying from 0 (fluid only) to 6µ105 µPL/mL. The particle morphology had a modest influence on friction, possibly because the µPL were fully squeezed between two mating surfaces by a 5.8 N normal load realizing boundary-like lubrication conditions. Differently, friction was observed to depend on the dimensionless parameter Ω, defined as the ratio between the total volume of the µPL enriching the simulated synovial fluid and the volume of the fluid itself. Both coefficients of friction were documented to grow with Ω reaching a plateau of µ s ∼ 0.4 and µ d ∼ 0.15, already at Ω ∼ 2×10−3. Future investigations will have to systematically analyze the effect of sliding velocity, normal load, and rigidity of the mating surfaces to elucidate in full the tribological behavior of µPL in the context of osteoarthritis