Hyaluronic Acid-Binding, Anionic, Nanoparticles Inhibit ECM Degradation and Restore Compressive Stiffness in Aggrecan-Depleted Articular Cartilage Explants

Alteration in cartilage matrix stiffness as an indicator and modulator of osteoarthritis

Osteoarthritis (OA) is characterized by cartilage degeneration and destruction, leading to joint ankylosis and disability. The major challenge in diagnosing OA at early stage is not only lack of clinical symptoms but also the insufficient histological and immunohistochemical signs. Alteration in cartilage stiffness during OA progression, especially at OA initiation, has been confirmed by growing evidences. Moreover, the stiffness of cartilage extracellular matrix (ECM), pericellular matrix (PCM) and chondrocytes during OA development are dynamically changed in unique and distinct fashions, revealing possibly inconsistent conclusions when detecting cartilage matrix stiffness at different locations and scales. In addition, it will be discussed regarding the mechanisms through which OA-related cartilage degenerations exhibit stiffened or softened matrix, highlighting some critical events that generally incurred to cartilage stiffness alteration, as well as some typical molecules that participated in constituting the mechanical properties of cartilage. Finally, in vitro culturing chondrocytes in various stiffness-tunable scaffolds provided a reliable method to explore the matrix stiffness-dependent modulation of chondrocyte metabolism, which offers valuable information on optimizing implant scaffolds to maximally promote cartilage repair and regeneration during OA. Overall, this review systematically and comprehensively elucidated the current progresses in the relationship between cartilage stiffness alteration and OA progression. We hope that deeper attention and understanding in this researching field will not only develop more innovative methods in OA early detection and diagnose but also provide promising ideas in OA therapy and prognosis.

Chitosan hydrogels with MK2 inhibitor peptide-loaded nanoparticles to treat atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that lacks ideal long-term treatment options due to a series of side effects, such as skin atrophy, related to the most common treatment prescribed to manage moderate-to-severe AD. In this study, a cell-penetrating MK2 inhibitor peptide YARA (YARAAARQARAKALNRQGLVAA) was loaded into hollow thermo-responsive pNIPAM nanoparticles (NP), which were further incorporated into chitosan hydrogels (H-NP-YARA) to promote local drug delivery, improve moisture and the anti-inflammatory activity. The NPs exhibited high loading efficiency (>50%) and the hydrogel remained porous following NP incorporation as observed by scanning electron microscopy (SEM). Both nanoparticles and hydrogels were able to improve the release of YARA and sustained release to up to 120 h. The hydrogels and NPs delivered 2 and 4-fold more YARA into viable skin layers of porcine skin in vitro at 12 h post-application than the non-encapsulated compound in intact and impaired barrier conditions. Furthermore, the YARA-loaded NPs (NP-YARA) and H-NP-YARA treatment decreased the levels of inflammatory cytokines up to 20 time-fold compared with the non-treated group of human keratinocytes under inflammatory conditions. Consistent with the results in cell culture, the loading of YARA in NP reduced the levels of IL-1β, IL-6, and TNF-α up to 3.3 times in an ex vivo skin culture model after induction of inflammation. A further decrease of up to 17 times-fold was observed with H-NP-YARA treatment compared to the drug in solution. Our data collectively suggest that chitosan hydrogel containing YARA-loaded nanoparticles is a promising new formulation for the topical treatment of AD.

Application of magnetic particle imaging to evaluate nanoparticle fate in rodent joints

Nanoparticles are a promising approach for improving intra-articular drug delivery and tissue targeting. However, techniques to non-invasively track and quantify their concentration in vivo are limited, resulting in an inadequate understanding of their retention, clearance, and biodistribution in the joint. Currently, fluorescence imaging is often used to track nanoparticle fate in animal models; however, this approach has limitations that impede long-term quantitative assessment of nanoparticles over time. The goal of this work was to evaluate an emerging imaging modality, magnetic particle imaging (MPI), for intra-articular tracking of nanoparticles. MPI provides 3D visualization and depth-independent quantification of superparamagnetic iron oxide nanoparticle (SPION) tracers. Here, we developed and characterized a polymer-based magnetic nanoparticle system incorporated with SPION tracers and cartilage targeting properties. MPI was then used to longitudinally assess nanoparticle fate after intra-articular injection. Magnetic nanoparticles were injected into the joints of healthy mice, and evaluated for nanoparticle retention, biodistribution, and clearance over 6 weeks using MPI. In parallel, the fate of fluorescently tagged nanoparticles was tracked using in vivo fluorescence imaging. The study was concluded at day 42, and MPI and fluorescence imaging demonstrated different profiles in nanoparticle retention and clearance from the joint. MPI signal was persistent over the study duration, suggesting NP retention of at least 42 days, much longer than the 14 days observed based on fluorescence signal. These data suggest that the type of tracer - SPIONs or fluorophores - and modality of imaging can affect interpretation of nanoparticle fate in the joint. Given that understanding particle fate over time is paramount for attaining insights about therapeutic profiles in vivo, our data suggest MPI may yield a quantitative and robust method to non-invasively track nanoparticles following intra-articular injection on an extended timeline.