Joint Lubrication Research Articles

The Importance of Hyaluronic Acid in Biological Systems

Hyaluronic acid (HA) is a crucial component of the extracellular matrix, found abundantly in connective tissues, skin, and synovial fluid. Its unique properties, including hydration capacity and viscoelasticity, play pivotal roles in tissue hydration, lubrication, and wound healing. Despite its ubiquitous presence, the specific mechanisms underlying its diverse biological functions remain the subject of ongoing research. Studies have elucidated HA's involvement in various physiological processes, such as cell proliferation, migration, and differentiation. Its interaction with cell surface receptors modulates signaling pathways implicated in tissue repair and inflammation regulation. Moreover, HA's rheological properties contribute to joint lubrication, facilitating smooth movement and preventing cartilage degradation. Understanding the multifaceted roles of HA holds significant implications for biomedical applications. Its therapeutic potential spans from skincare formulations to regenerative medicine and drug delivery systems. Targeting HA metabolism presents novel strategies for treating conditions like osteoarthritis, dry eye syndrome, and dermal aging. Continued exploration of HA biology promises exciting avenues for scientific advancement and clinical innovation. Emerging technologies, such as biomaterial engineering and nanomedicine, offer opportunities to tailor HA-based interventions for enhanced efficacy and targeted delivery. Additionally, investigating HA's interplay with the immune system could uncover new immunomodulatory therapies. In conclusion, the importance of hyaluronic acid in biological systems is indisputable, given its indispensable roles in tissue homeostasis and repair. By deciphering its intricate mechanisms of action, researchers pave the way for groundbreaking advancements in medicine and biotechnology. Harnessing the therapeutic potential of HA stands poised to revolutionize healthcare, offering solutions to a myriad of pathological conditions and enhancing quality of life.

Addressing Technical and Environmental Obstacles in Livestock Management for Enhanced Drinking Water Quality

Water is a vital nutrient for livestock, constituting 60 to 70 percent of their body composition. It plays a crucial role in maintaining body fluids, ion balance, digestion, nutrient absorption, waste elimination, and temperature regulation. Additionally, water serves as a lubricant and cushion for joints, spinal cord, and tissues, ranking second only to oxygen in essentiality for life. Despite its importance, water can also serve as a vehicle for transmitting pathogenic organisms, posing a significant concern for livestock health. Access to safe water remains a challenge, as the cost is prohibitive for many, leading to reliance on available water sources regardless of their quality. Given the presence of pathogenic microorganisms in freshwater bodies, routine assessment is essential to prevent future disease outbreaks among livestock populations. Keywords: Livestock Management, Drinking Water Quality, Pathogenic Organisms, Freshwater Bodies, Disease Outbreaks

Construction and tribological properties of poly acrylic acid‐poly(3‐(methacryloylamino)propyl) dimethyl(3‐sulfopropyl)ammonium hydroxide hydrogel coatings embedded with SiO2 nanoparticles on Ti6Al4V substrate

AbstractThe development of highly effective bio‐lubricant coatings for arthritis treatment is extremely demanded. Herein, inspired by the efficient lubrication of articular cartilage, acrylic acid (AA) with (3‐(methacryloylamino) propyl) dimethyl (3‐sulfopropyl) ammonium hydroxide (MPDSAH) hydrogel coatings containing nanoparticles on Ti6Al4V substrate were designed and fabricated via UV grafting technology. SiO2 and SiO2 grafted with PAA polymer brushes (SiO2‐g‐PAA) were separately doped into the PAA‐PMPDSAH hydrogel. The PAA‐PMPDSAH/SiO2‐g‐PAA exhibits good tensile and compressive properties compared with PAA‐PMPDSAH/SiO2 hydrogel, with an enhancement of 183.4% in tensile modulus and 60.8% in compressive modulus. The PAA‐PMPDSAH/SiO2‐g‐PAA hydrogel coatings exhibit a low wear volume, 2.9 ± 0.16 × 106 μm3, representing a decline of 32.1% and 61.3% compared with the PAA‐PMPDSAH and PAA‐PMPDSAH/SiO2 hydrogel coatings, respectively. The antiwear performance has obviously improved. The hydrophilic PAA polymer brushes prevent the agglomeration of nanoparticles and promote homogeneously dispersion within the hydrogel. The three‐dimensional crosslinked network structure of hydrogel effectively protects the structural integrity of the polymer brushes, thereby facilitating enduring lubrication properties. This work provides a strategy for promising artificial joint lubrication in biomedical fields.

Chemically programmed nanozyme with microenvironment remodeling for combinatorial treatment of osteoarthritis

Restoring the equilibrium of joint homeostasis is crucial in treating osteoarthritis (OA). However, current strategies are primarily concentrated on individual interventions aimed at improving joint lubrication, reducing inflammation, eliminating reactive oxygen species, and stimulating cartilage differentiation, resulting in unsatisfactory therapeutic efficacy. In this work, a kind of Zn-doped hollow mesoporous CeOx (HMZC) is prepared by a facile two-step method to efficiently encapsulate the kartogenin (KGN), and then HA as a “gatekeeper” is wrapped on the surface of HMZC to generate KGN@HMZC@HA nanozymes. Since the formation of additional oxygen vacancies in the Zn-doping procedure, enabling the KGN@HMZC@HA with SOD-like and CAT-like catalytic activities. The prepared KGN@HMZC@HA can achieve the controlled KGN release in response to the specific OA environment, and chemically programmed OA microenvironment (i.e., microenvironment remodeling) by effective ROS scavenging, O2 production, macrophages transformation of M1 to M2 phenotype, and inflammation suppression. Both cellular and in vivo findings manifest the promising treatment efficiency and minimal adverse effect of the chemically programmed nanozyme for OA therapy, showing its tremendous potential as a desirable treatment option for OA.

Exploration of the Advanced VIVOTM Joint Simulator: An In-Depth Analysis of Opportunities and Limitations Demonstrated by the Artificial Knee Joint.

In biomechanical research, advanced joint simulators such as VIVOTM offer the ability to test artificial joints under realistic kinematics and load conditions. Furthermore, it promises to simplify testing with advanced control approaches and the ability to include virtual ligaments. However, the overall functionality concerning specific test setup conditions, such as the joint lubrication or control algorithm, has not been investigated in-depth so far. Therefore, the aim of this study was to analyse the basic functionality of the VIVOTM joint simulator with six degrees of freedom in order to highlight its capabilities and limitations when testing a total knee endoprostheses using a passive flexion-extension movement. For this, different test setup conditions were investigated, e.g., the control method, repeatability and kinematic reproducibility, waveform frequency, lubrication, and implant embedding. The features offered by the VIVOTM joint simulator are useful for testing joint endoprostheses under realistic loading scenarios. It was found that the results were highly influenced by the varying test setup conditions, although the same mechanical load case was analysed. This study highlights the difficulties encountered when using six degrees of freedom joint simulators, contributes to their understanding, and supports users of advanced joint simulators through functional and tribological analysis of joint endoprostheses.

In vitro drug release and cartilage interface lubrication properties of biomimetic polymers

Osteoarthritis is a degenerative disease that is widely found in the elderly population, with a trend towards a younger age group in recent years. In the early stages of arthritis, patients are treated with hyaluronic acid injections and anti-inflammatory drugs. However, it has been found that hyaluronic acid can only play a supportive role and does not have a lubricating effect, and due to the absence of blood vessels, nerves, and lymphatic vessels in the articular cartilage, the oral anti-inflammatory drugs cannot reach the interface of the inflammatory joints adequately, and the drug utilisation rate is low. Herein, we designed and prepared a brush-like bionic lubricant for joint lubrication and drug loading. The poly(2-methyl-2-oxazoline) branched chain was grafted onto the hyaluronic acid main chain by ring-opening polymerisation and graft polymerisation to form a brush-like bionic lubricin containing multiple hydrophilic groups, which was self-assembled to encapsulate the drug by using its multi-branched special structure for drug loading. The friction behaviour tests on the articular cartilage surface showed that the prepared bionic lubricin has excellent lubrication effect, with a minimum friction coefficient of 0.036 close to the lubrication effect of natural synovial fluid, which is mainly due to the hydrophilic groups on its molecular chain that can adsorb the water molecules and form a hydration layer at the cartilage interface, which plays the role of hydration lubrication. In addition, in vitro drug release studies showed that the synthesised drug-loading biomimetic lubricin had a certain drug release capacity, and the maximum drug release rate could reach 77.8 % at 72 h. The synthesis of this bionic lubricant with dual functions of lubrication and drug release provides a new idea for the treatment of osteoarthritis.

The Actin Cytoskeleton as a Regulator of Proteoglycan 4.

The superficial zone (SZ) of articular cartilage is responsible for distributing shear forces for optimal cartilage loading and contributes to joint lubrication through the production of proteoglycan 4 (PRG4). PRG4 plays a critical role in joint homeostasis and is chondroprotective. Normal PRG4 production is affected by inflammation and irregular mechanical loading in post-traumatic osteoarthritis (PTOA). THe SZ chondrocyte (SZC) phenotype, including PRG4 expression, is regulated by the actin cytoskeleton in vitro. There remains a limited understanding of the regulation of PRG4 by the actin cytoskeleton in native articular chondrocytes. The filamentous (F)-actin cytoskeleton is a potential node in crosstalk between mechanical stimulation and cytokine activation and the regulation of PRG4 in SZCs, therefore developing insights in the regulation of PRG4 by actin may identify molecular targets for novel PTOA therapies. A comprehensive literature search on PRG4 and the regulation of the SZC phenotype by actin organization was performed. PRG4 is strongly regulated by the actin cytoskeleton in isolated SZCs in vitro. Biochemical and mechanical stimuli have been characterized to regulate PRG4 and may converge upon actin cytoskeleton signaling. Actin-based regulation of PRG4 in native SZCs is not fully understood and requires further elucidation. Understanding the regulation of PRG4 by actin in SZCs requires an in vivo context to further potential of leveraging actin arrangement to arthritic therapeutics.

Knee Osteoarthritis in Women: Ancient and Modern Treatment Modalities

Knee osteoarthritis (OA) is a common and debilitating condition that predominantly affects women. This article explores the historical and contemporary treatment modalities for knee OA in women, highlighting the evolution of therapeutic approaches over time. Ancient treatments for knee OA primarily focused on natural remedies and lifestyle modifications. These included the use of herbal medicines, dietary adjustments, and physical therapies like hot and cold compresses. Ancient cultures recognized the importance of maintaining a healthy weight and engaging in physical activity to alleviate symptoms and improve joint function. In modern times, treatment options for knee OA in women have significantly evolved. While conservative measures such as physical therapy, weight management, and non-steroidal anti-inflammatory drugs (NSAIDs) are still important, advanced interventions are available. These include corticosteroid injections, hyaluronic acid injections, and platelet-rich plasma therapy, which aim to reduce pain and enhance joint lubrication. For severe cases, surgical interventions like arthroscopy, partial or total knee replacement, and osteotomy may be considered. The article also explores the emerging field of regenerative medicine, which offers promising avenues for the management of knee OA in women. Stem cell therapies and tissue engineering approaches show potential in regenerating damaged cartilage and slowing down disease progression. Additionally, the role of lifestyle modifications, exercise, and physical therapy remains crucial in the modern era, with a focus on tailored rehabilitation programs to improve strength, flexibility, and joint stability. In conclusion, the treatment of knee OA in women has transitioned from ancient remedies rooted in tradition to a modern, evidence-based approach that combines conservative measures with innovative medical interventions. The evolution of treatment modalities reflects advances in medical knowledge and technology, offering hope for improved quality of life for women affected by this condition.

Calcium ions have a detrimental impact on the boundary lubrication property of hyaluronic acid and lubricin (PRG-4) both alone and in combination

Cartilage demineralisation in Osteoarthritis (OA) patients can elevate calcium ion levels in synovial fluid, as evidenced by the prevalence of precipitated calcium phosphate crystals in OA synovial fluid. Although it has been reported that there is a potential connection between elevated concentrations of calcium ions and a deterioration in the lubrication and wear resistance of cartilage tissues, the mechanism behind the strong link between calcium ion concentration and decreased lubrication performance is unclear. In this work, the AFM friction, imaging, and normal force distance measurements were used to investigate the lubrication performances of hyaluronic acid (HA), Lubricin (LUB), and HA-LUB complex in the presence of calcium ions (5 mM, 15 mM, and 30 mM), to understand the possible mechanism behind the change of lubrication property. The results of AFM friction measurements suggest that introducing calcium ions to the environment effectively eliminated the lubrication ability of HA and HA-LUB, especially with relatively low loading applied. The AFM images indicate that it is unlikely that structural or morphological changes in the surface-bound layer upon calcium ions addition are primarily responsible for the friction results demonstrated. Further, the poor correlation between the effect of calcium ions on the adhesion forces and its impact on friction suggests that the decrease in the lubricating ability of both layers is likely a result of changes in the hydration of the HA-LUB surface bound layers than changes in intermolecular or intramolecular binding. This work provides the first experimental evidence lending towards the relationship between bone demineralisation and articular cartilage degradation at the onset of OA and the mechanism through which elevated calcium levels in the synovial fluid act on joint lubrication.

Enhanced Hyaluronic Acid Production from Priestia flexa N7 Isolates

Background: Hyaluronic acid (HA) is a gel-like substance made up of glucuronic acid and N-acetylglucosamine units, capable of absorbing and retaining water, present in hydrated gel form across human and animal tissues. It aids in joint lubrication and moisture retention and acts as a cushion for shock absorption. HA has unique biological properties, promoting fibroblast cell growth, aiding wound healing, and exhibiting low solubility and viscosity, making it an organic ingredient in tissue culture techniques. It is utilized in eye drops and skin ointments and plays a vital role in the extracellular matrix, rendering it invaluable in medical and cosmetic applications, such as treating osteoarthritis and enhancing skin wound recovery. Methods: The methods employed in this study involve isolating microorganisms, screening bacterial strains capable of synthesizing HA, identifying bacteria using molecular biological methods, and researching optimal conditions to select bacterial strains that produce the highest HA concentrations. Results: In this study, strain Priestia flexa N7 was studied for suitable conditions for HA biosynthesis. Bacterial strains were fermented for 48 h on medium containing the following ingredients: glucose (60 g/L); yeast extract (5.0 g/L); peptone (20 g/L); K2HPO4 (2.0 g/L); Na2HPO4 (1.0 g/L); NaCl (2.0 g/L); FeSO4 (1.0 g/l); sodium glutamate (9.0 g/L); and MgSO4.7H2O (2.0 g/L) and pH 8.0 at 37°C under the condition of continuous shaking at 150 rpm. The maximum HA production achieved was 1105 mg/L. Conclusions: The mentioned bacterial strain exhibits significant potential for HA synthesis and is extensively employed in producing items across the health care, medical, food, and cosmetic industries. These findings revealed the most effective HA acid manufacturing strategy for achieving maximum output.

Recent Advances in Bio-Tribology From Joint Lubrication to Medical Implants: A Review

Bio-tribology, the study of lubrication, wear, and friction in biological systems, has made recent strides in the lubrication of medical implants and joints. This comprehensive review discusses the most recent developments in bio-tribology, with an emphasis on the transition from basic science to medical engineering applications. An overview of bio-tribology and its increasing significance in medicine commences the study. Following this, recent research on the composition of synovial fluid and its function in minimizing friction in natural joints is discussed. Medical implant tribology, including degradation issues in dental prostheses and joint replacements, is then addressed. This study investigates the manner in which surface modifications and coatings improve the tribological performance of medical implants. It emphasizes recent developments in material science and engineering. This article emphasizes the significance of minimizing implant material degradation in relation to the functionality and longevity of biomedical devices. Following this, digital models, simulations, and state-of-the-art imaging techniques that have propelled bio-tribology forward are highlighted. In addition to proposing potential research avenues to overcome the current obstacles, the article highlights the interdisciplinary nature of bio-tribology and urges collaboration among tribology, materials science, and biomechanics researchers.

Bio-bearings: Numerical Model of the Solid Lubricant in the Leg Joints of Insects

The proposed model describes the behavior of the lubricant particles at the interface between two surfaces for a group of cylindrical semi-solid lubricant fragments observed in a real beetle leg joint. It is shown that the lubricant particles may maintain a gap between joint surfaces at load. At the regular shear motion, such randomly oriented particles are reorienting perpendicular to the shear and function as a rolling bearing: the system demonstrates the lowest energy loss and lowest friction. At an increased load, the friction non-linearly increases, because of an increase of the particles’ eccentricity. Finally, at some load, the particle rotation stops, friction switches from the rolling to the sliding regime and increases significantly.

Lubricating Micro‐Interface Assisted General Strategy for Preparing dECM‐Microparticle–Based Heterogeneous Granular Inks toward 3D Printing

AbstractDecellularized extracellular matrix (dECM) retains the bioactive components to mimic tissue‐specific microenvironment. Designing dECM‐based inks for 3D printing to prepare scaffolds can enhance the regeneration of corresponding tissues. However, due to the strict requirements for inks, how to efficiently prepare dECM‐based inks is a challenge. Inspired by granular lubrication, the present study proposes an effective and general method for preparing granular ink from dECM microparticles (MP) with high content. Through dopamine polymerization, dECM‐MPs are coated with polydopamine (PDA). Meanwhile, gelatin methacryloyl (GelMA)‐based microspheres (GelMA‐MSs) are prepared with available double bonds. dECM‐MPs (30–40 wt%) and GelMA‐MSs assemble to form a granular ink, exhibiting well‐performed extrudability, plasticity, and fidelity. Further inspired by joint lubrication, hyaluronic acid (HA) is introduced into PDA coating and GelMA‐MSs to reduce the micro‐interface friction, further promoting the printability and broadening the printable window of dECM‐MPs content to 30–60 wt%. Osteochondral scaffold and skin wound dressing are fabricated through 3D printing from the corresponding dECM‐MPs, enhancing the regeneration of the corresponding tissues in vivo. Especially, the realization of printability of highly rigid dECM‐MPs confirms the universality, reliability and efficiency of the present strategy.

The effect of hyaluronic acid concentration on the rheological and tribological properties of artificial synovial fluid base solutions

Synovial joints are a basic part of the human body. Lack of proper lubrication of joints can lead to significant wear of their surfaces. The tribological and rheological properties of artificial synovial fluid solutions based on hyaluronic acid were studied. It was found that the concentration of selected hyaluronic acid solutions significantly affects the investigated parameters. The most promising results were obtained for 8 wt% hyaluronic acid solution, which showed the highest viscosity and wettability, and the lowest wear.

Modulating mechanobiology as a therapeutic target for synovial fibrosis to restore joint lubrication

Fibroses are disorders linked to persistence of myofibroblasts due to biochemical (e.g., Transforming growth factor-β) and biophysical cues (e.g., a stiff microenvironment). In the context of osteoarthritis, fibrotic changes in the joint-lining synovium have been linked with disease progression. The objective of this study was to probe synovial fibroblast mechanobiology and how essential functions (i.e., lubrication) are altered in fibrotic environments. Both ex vivo and in vitro synovium models were assessed for fibrotic and lubrication biomarkers to better understand the role of mechanobiology and lubrication. Additionally, in vitro, work on small molecules targeting mechanobiology was assessed. Our results indicated that modulating mechanobiology could rescue the fibrotic phenotype instigated by stiffening microenvironment that resulted in altered lubricant expression. A small molecule therapeutic, fasudil, blocked ROCK-mediated contractility and this inhibition of the fibrotic mechano-response of synovial fibroblasts restored proper lubrication function, providing insight into mechanisms of disease progression as well as a new avenue for therapeutic development. This study identifies synovial fibrosis as a condition that potentially has joint-wide deficits through inhibiting lubrication. Additionally, modulating mechanobiology (i.e., ROCK-mediated contractility) may pose a potential target for small molecule therapies that can be delivered to the joint space. Applied Biological Sciences.

Location of Polyelectrolytes in Swollen Lipid Oligobilayers.

Osteoarthritis is caused by degeneration of the cartilage, which covers the bone ends of the joints and is decorated with an oligolamellar phospholipid (PL) bilayer. The gap between the bone ends is filled with synovial fluid mainly containing hyaluronic acid (HA). HA and PLs are supposed to reduce friction and protect the cartilage from wear in joint movement. However, a detailed understanding of the molecular mechanisms of joint lubrication is still missing. Previously, we found that aqueous solutions of HA and poly(allylamine hydrochloride) (PAH), the latter serving as a polymeric analogue to HA, adsorb onto the headgroups of surface-bound 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) oligobilayers and significantly enhance their stability with respect to shear forces, typically occurring in joint movement. We now investigated the precise location of PAH chains across the lipid films in neutron reflectivity measurements, as bridging of the oligobilayers by polyelectrolytes (PEs) might be the cause for their improved mechanical stability. In a first set of experiments, we used hydrogenated PAH and chain-deuterated DMPC (DMPC-d54) to improve the contrast between the lipids and potentially intruding PAH. However, due to difficulties in distinguishing between incorporation of water and PAH, penetration into the lipid chain region could hardly be proven quantitatively. Therefore, we designed a more elaborate experiment based on mixed films of DMPC-d54 and hydrogenated DMPC, which is insensitive to water penetration into the films. Beside facilitating a detailed structural characterization of the oligolamellar system, this elaborate approach showed that PAH adsorbs to the DMPC heads and penetrates the lipid tail strata. No PAH was found in the lipid head strata, which excludes bridging of several lipid bilayers by the PE chains. The data are consistent with the assumption that PAH bridges are formed between the headgroups of two adjacent bilayers and contribute to the enhanced mechanical stability.

Targeting CD44 Receptor Pathways in Degenerative Joint Diseases: Involvement of Proteoglycan-4 (PRG4).

Rheumatoid arthritis (RA), osteoarthritis (OA), and gout are the most prevalent degenerative joint diseases (DJDs). The pathogenesis underlying joint disease in DJDs remains unclear. Considering the severe toxicities reported with anti-inflammatory and disease-modifying agents, there is a clear need to develop new treatments that are specific in their effect while not being associated with significant toxicities. A key feature in the development of joint disease is the overexpression of adhesion molecules, e.g., CD44. Expression of CD44 and its variants in the synovial tissues of patients with DJDs is strongly associated with cartilage damage and appears to be a predicting factor of synovial inflammation in DJDs. Targeting CD44 and its downstream signaling proteins has emerged as a promising therapeutic strategy. PRG4 is a mucinous glycoprotein that binds to the CD44 receptor and is physiologically involved in joint lubrication. PRG4-CD44 is a pivotal regulator of synovial lining cell hemostasis in the joint, where lack of PRG4 expression triggers chronic inflammation and fibrosis, driven by persistent activation of synovial cells. In view of the significance of CD44 in DJD pathogenesis and the potential biological role for PRG4, this review aims to summarize the involvement of PRG4-CD44 signaling in controlling synovitis, synovial hypertrophy, and tissue fibrosis in DJDs.

Drug in Therapeutic Polymer: Sinomenine-Loaded Oxidation-Responsive Polymeric Nanoparticles for Rheumatoid Arthritis Treatment.

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that frequently involves cartilage damage and the destruction of the bone structure, ultimately resulting in disability and long-term pain. It is clear that overexpression of reactive oxygen species (ROS) and the complex inflammatory microenvironment are the main causes of RA pathogenesis; thereby, the efficacy of any single-drug treatment is limited. Herein, we formulated a therapeutic hyaluronic acid derivative (PAM-HA) with adsorption capacity to the subchondral bone, a long retention time within inflamed joints, and ROS-scavenging capacity, which was used as a drug carrier for realizing the controlled release of sinomenine (Sin) within arthritic joints. This "drug in therapeutic polymer" design strategy was aimed at realizing antioxidant and anti-inflammatory combination therapy for RA. In vivo experiments suggest that PAM-HA@Sin NPs can be retained in the inflamed joints of rats for a long time compared with commercially available free Sin injections. As expected, therapeutic PAM-HA polymeric carriers can increase joint lubrication and reduce oxidative stress, while the released Sin induces downregulation of proinflammatory factors (TNF-α and IL-1β) and upregulation of anti-inflammatory factors (Arg-1 and IL-10) via the NF-κB pathway. In summary, a ROS-scavenging hyaluronic acid (HA) derivative was developed as the nanocarrier for Sin delivery to simultaneously remodel the oxidative/inflammatory microenvironment in RA, which opens up new horizons for the development of therapeutic polymers and the combined therapeutic strategies.

Mimicking Antioxidases and Hyaluronan Synthase: A Zwitterionic Nanozyme for Photothermal Therapy of Osteoarthritis.

Restoring joint homeostasis is crucial for relieving osteoarthritis (OA). Current strategies are limited to unilateral efforts in joint lubrication, inhibition of inflammation, free radicals scavenging, and cartilage regeneration. Herein, by modifying molybdenum disulfide (MoS2 ) with Mg2+ -doped polydopamine and coating with polysulfobetaines, a dual-bionic photothermal nanozyme (MPMP) is constructed to mimic antioxidases/hyaluronan synthase for OA therapy. Photothermally enhanced lubrication lowers the coefficient of friction (0.028) in the early stage of OA treatment. The antioxidases-mimicking properties of MPMP nanozyme contribute to eliminating reactive oxygen and nitrogen species (ROS/RNS) (over 90% of scavenging ratio for H2 O2 /·OH/O· 2 - /DPPH/ABTS+ ) and supplying O2 . With NIR irradiation, the MPMP nanozyme triggers thermogenesis (upregulating HSP70 expression) and Mg2+ release, which promotes the chondrogenesis in inflammatory conditions by deactivating NF-κB/IL-17 signaling pathways and enhancing MAPK signaling pathway. Benefiting from HSP70 and Mg2+ , MPMP-NIR shows HAS-mimicking activity to increase the intracellular (twofold) and extracellular (3.12-fold) HA production. Therefore, MPMP-NIR demonstrates superior spatiotemporally therapeutic effect on OA in mice model, in terms of osteophytes (83.41% of reduction), OARSI scores (88.57% of reduction), and ACAN expression (2.70-fold of increment). Hence, insights into dual-bionic nanozymes can be a promising strategy for OA therapy or other inflammation-related diseases.

Changes in joint lubrication with the degree of meniscectomy and osteochondral junction integrity

This study focuses on the relationship between meniscectomy and osteochondral junction health, and their integrity on cartilage lubrication. Using a previously published multi-component joint computational model, we explored the impact of increasing degree of meniscectomy and osteochondral flow conductivity on joint lubrication. Results suggest a greater effect of meniscectomy on joint lubrication when the osteochondral junction is healthy. However, the impact is less pronounced when the osteochondral junction is already diseased due to compromised lubrication capability. This research provides a first-time quantitative analysis of this interaction, which highlights the importance of adequately evaluating the osteochondral junction’s condition before meniscectomy surgery. It also suggests that reducing post-surgery activity level may be beneficial for patients with diseased junctions undergoing meniscectomy.