Acute Changes in NADPH Oxidase 4 in Early Post-Traumatic Osteoarthritis

Bone Adaptations to a Whole Body Vibration Protocol in Murine Models of Different Ages: A Preliminary Study on Structural Changes and Biomarker Evaluation

Background/Objectives: Whole body vibration (WBV) is a valuable tool to mitigate physiological adaptations related to age and inactivity. Although significant benefits have been found at the musculoskeletal level, including increased bone mass and reduced muscle atrophy, the underlying biological mechanisms remain largely unknown. Therefore, our study aimed to evaluate the effects of vibratory training on bone tissue in murine models of different age groups by investigating the structural and distribution changes in some crucial biomarkers involved in musculoskeletal homeostasis. Methods: Specifically, 4-, 12-, and 24-month-old mice were trained with a WBV protocol characterized by three series of 2 min and 30 s, interspersed with a recovery period of the same duration, on a 3-weekly frequency for 3 months. At the end of the training, histological and morphometric analyses were conducted, in association with immunohistochemical analysis to investigate changes in the distribution of fibronectin type III domain-containing protein 5 (FNDC5), NADPH oxidase 4 (NOX4), and sirtuin 1 (SIRT1). Results: Our preliminary results showed that WBV improves musculoskeletal health by preserving bone architecture and promoting up-regulation of FNDC5 and SIRT1 and down-regulation of NOX4. Conclusions: Our study confirms vibratory training as a viable alternative to counter musculoskeletal decline in elderly and/or sedentary subjects. Further investigations should be conducted to deepen knowledge in this field and explore the role of other molecular mediators in physiological adaptations to vibration.

Research progress of procyanidins in repairing cartilage injury after anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tear is a common sports-related injury, and cartilage injury always emerges as a serious complication following ACL tear, significantly impacting the physical and psychological well-being of affected individuals. Over the years, efforts have been directed toward finding strategies to repair cartilage injury after ACL tear. In recent times, procyanidins, known for their anti-inflammatory and antioxidant properties, have emerged as potential key players in addressing this concern. This article focuses on summarizing the research progress of procyanidins in repairing cartilage injury after ACL tear. It covers the roles, mechanisms, and clinical significance of procyanidins in repairing cartilage injury following ACL tear and explores the future prospects of procyanidins in this domain. This review provides novel insights and hope for the repair of cartilage injury following ACL tear.

Inflammatory mechanisms in post-traumatic osteoarthritis: a role for CaMKK2

Post-traumatic osteoarthritis (PTOA) is a multifactorial disease of the cartilage, synovium, and subchondral bone resulting from direct joint trauma and altered joint mechanics after traumatic injury. There are no current disease-modifying therapies for PTOA, and early surgical interventions focused on stabilizing the joint do not halt disease progression. Chronic pain and functional disability negatively affect the quality of life and take an economic toll on affected patients. While multiple mechanisms are at play in disease progression, joint inflammation is a key contributor. Impact-induced mitochondrial dysfunction and cell death or altered joint mechanics after trauma culminate in inflammatory cytokine release from synoviocytes and chondrocytes, cartilage catabolism, suppression of cartilage anabolism, synovitis, and subchondral bone disease, highlighting the complexity of the disease. Current understanding of the cellular and molecular mechanisms underlying the disease pathology has allowed for the investigation of a variety of therapeutic strategies that target unique apoptotic and/or inflammatory processes in the joint. This review provides a concise overview of the inflammatory and apoptotic mechanisms underlying PTOA pathogenesis and identifies potential therapeutic targets to mitigate disease progression. We highlight Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2), a serine/threonine protein kinase that was recently identified to play a role in murine and human osteoarthritis pathogenesis by coordinating chondrocyte inflammatory responses and apoptosis. Given its additional effects in regulating macrophage inflammatory signaling and bone remodeling, CaMKK2 emerges as a promising disease-modifying therapeutic target against PTOA.

Drug Delivery Strategies and Nanozyme Technologies to Overcome Limitations for Targeting Oxidative Stress in Osteoarthritis

Oxidative stress is an important, but elusive, therapeutic target for osteoarthritis (OA). Antioxidant strategies that target oxidative stress through the elimination of reactive oxygen species (ROS) have been widely evaluated for OA but are limited by the physiological characteristics of the joint. Current hallmarks in antioxidant treatment strategies include poor bioavailability, poor stability, and poor retention in the joint. For example, oral intake of exogenous antioxidants has limited access to the joint space, and intra-articular injections require frequent dosing to provide therapeutic effects. Advancements in ROS-scavenging nanomaterials, also known as nanozymes, leverage bioactive material properties to improve delivery and retention. Material properties of nanozymes can be tuned to overcome physiological barriers in the knee. However, the clinical application of these nanozymes is still limited, and studies to understand their utility in treating OA are still in their infancy. The objective of this review is to evaluate current antioxidant treatment strategies and the development of nanozymes as a potential alternative to conventional small molecules and enzymes.

An Integrated View of Stressors as Causative Agents in OA Pathogenesis

Cells in the body are exposed to dynamic external and internal environments, many of which cause cell damage. The cell's response to this damage, broadly called the stress response, is meant to promote survival and repair or remove damage. However, not all damage can be repaired, and sometimes, even worse, the stress response can overtax the system itself, further aggravating homeostasis and leading to its loss. Aging phenotypes are considered a manifestation of accumulated cellular damage and defective repair. This is particularly apparent in the primary cell type of the articular joint, the articular chondrocytes. Articular chondrocytes are constantly facing the challenge of stressors, including mechanical overloading, oxidation, DNA damage, proteostatic stress, and metabolic imbalance. The consequence of the accumulation of stress on articular chondrocytes is aberrant mitogenesis and differentiation, defective extracellular matrix production and turnover, cellular senescence, and cell death. The most severe form of stress-induced chondrocyte dysfunction in the joints is osteoarthritis (OA). Here, we summarize studies on the cellular effects of stressors on articular chondrocytes and demonstrate that the molecular effectors of the stress pathways connect to amplify articular joint dysfunction and OA development.

NADPH oxidase 4 deficiency attenuates experimental osteoarthritis in mice

OBJECTIVE

Low-grade inflammation plays a pivotal role in osteoarthritis (OA) through exposure to reactive oxygen species (ROS). In chondrocytes, NADPH oxidase 4 (NOX4) is one of the major ROS producers. In this study, we evaluated the role of NOX4 on joint homoeostasis after destabilisation of the medial meniscus (DMM) in mice.

METHODS

Experimental OA was simulated on cartilage explants using interleukin-1β (IL-1β) and induced by DMM in wild-type (WT) and NOX4 knockout (NOX4^-/-) mice. We evaluated NOX4 expression, inflammation, cartilage metabolism and oxidative stress by immunohistochemistry. Bone phenotype was also determined by micro-CT and histomorphometry.

RESULTS

Whole body NOX4 deletion attenuated experimental OA in mice, with a significant reduction of the OARSI score at 8 weeks. DMM increased total subchondral bone plate (SB.Th), epiphysial trabecular thicknesses (Tb.Th) and bone volume fraction (BV/TV) in both NOX4^-/- and wild-type (WT) mice. Interestingly, DDM decreased total connectivity density (Conn.Dens) and increased medial BV/TV and Tb.Th only in WT mice. Ex vivo, NOX4 deficiency increased aggrecan (AGG) expression and decreased matrix metalloproteinase 13 (MMP13) and collagen type I (COL1) expression. IL-1β increased NOX4 and 8-hydroxy-2'-deoxyguanosine (8-OHdG) expression in WT cartilage explants but not in NOX4^-/-. In vivo, absence of NOX4 increased anabolism and decreased catabolism after DMM. Finally, NOX4 deletion decreased synovitis score, 8-OHdG and F4/80 staining following DMM.

CONCLUSION

NOX4 deficiency restores cartilage homoeostasis, inhibits oxidative stress, inflammation and delays OA progression after DMM in mice. These findings suggest that NOX4 represent a potential target to counteract for OA treatment.

Subchondral bone structure and synovial fluid metabolism are altered in injured and contralateral limbs 7 days after non-invasive joint injury in skeletally-mature C57BL/6 mice

OBJECTIVE

Post-traumatic osteoarthritis (PTOA) commonly develops after ACL injury, but early changes to the joint soon after injury are insufficiently understood. The objectives of this study were (1) evaluate the response of subchondral bone tissue modulus to joint injury and (2) identify which bone structural, material, and metabolic outcomes are local (i.e., injured joint only) or systemic (i.e., injured and contralateral-to-injured).

DESIGN

Female C57Bl∖6N mice (19 weeks at injury) underwent tibial compression overload to simulate ACL injury (n = 8) or a small pre-load (n = 8). Synovial fluid was harvested at euthanasia 7 days later for metabolomic profiling. Bone outcomes included epiphyseal and SCB microarchitecture, SCB nanoindentation modulus, SCB formation rate, and osteoclast number density.

RESULTS

Injury decreased epiphyseal bone volume fraction ([-5.29, -1.38%], P = 0.0016) and decreased SCB thickness for injured vs sham-injured limbs ([2.2, 31.4 μm], P = 0.017)). Epiphyseal bone loss commonly occurred for contralateral-to-injured limbs. There was not sufficient evidence to conclude that SCB modulus changes with injury. Metabolomic analyses revealed dysregulated synovial fluid metabolism with joint injury but that many metabolic pathways are shared between injured and contralateral-to-injured limbs.

CONCLUSION

This study demonstrates rapid changes to bone structure and synovial fluid metabolism after injury with the potential for influencing the progression to PTOA. These changes are often evidenced in the contralateral-to-injured limb, indicating that systemic musculoskeletal responses to joint injury should not be overlooked.

Inhibition of NADPH Oxidases Prevents the Development of Osteoarthritis

Increased oxidative stress in osteoarthritis (OA) cartilage mediates catabolic signal transduction leading to extracellular matrix degradation and chondrocyte apoptosis. This study aimed to explore the contribution of NADPH oxidase (NOX), a major source of cellular reactive oxygen species (ROS), to the catabolic process of chondrocytes and to OA. The inhibition of NOX isoforms with a pan-NOX inhibitor, APX-115, significantly decreased IL-1β-induced ROS production in primary chondrocytes and, most potently, suppressed the expression of oxidative stress marker genes and catabolic proteases compared with the inhibition of other ROS sources. Catabolic stimuli by IL-1β treatment and in post-traumatic OA conditions upregulated the expression of NOX2 and NOX4 in chondrocytes. In the post-traumatic OA model, the pharmacologic inhibition of NOX protected mice against OA by modulating the oxidative stress and the expression of MMP-13 and Adamts5 in chondrocytes. Mechanistically, NOX inhibition suppresses Rac1, p38, and JNK MAPK signaling consistently and restores oxidative phosphorylation in IL-1β-treated chondrocytes. In conclusion, NOX inhibition prevented the development of OA by attenuating the catabolic signaling and restoring the mitochondrial metabolism and can thus be a promising class of drug for OA.

Recent Advances in Reactive Oxygen Species (ROS)-Responsive Polyfunctional Nanosystems 3.0 for the Treatment of Osteoarthritis

Osteoarthritis (OA) is an inflammatory and degenerative joint disease with severe effects on individuals, society, and the economy that affects millions of elderly people around the world. To date, there are no effective treatments for OA; however, there are some treatments that slow or prevent its progression. Polyfunctional nanosystems have many advantages, such as controlled release, targeted therapy and high loading rate, and have been widely used in OA treatment. Previous mechanistic studies have revealed that inflammation and ROS are interrelated, and a large number of studies have demonstrated that ROS play an important role in different types of OA development. In this review article, we summarize third-generation ROS-sensitive nanomaterials that scavenge excessive ROS from chondrocytes and osteoclasts in vivo. We only focus on polymer-based nanoparticles (NPs) and do not review the effects of drug-loaded or heavy metal NPs. Mounting evidence suggests that polyfunctional nanosystems will be a promising therapeutic strategy in OA therapy due to their unique characteristics of being sensitive to changes in the internal environment.

Identification of the Resveratrol Potential Targets in the Treatment of Osteoarthritis

Objectives

Osteoarthritis (OA) is a chronic joint degenerative disease and has become an important health problem for the elderly. However, there is still a lack of effective drugs for the treatment of OA. Our research combines bioinformatics and experimental strategies to determine the target of resveratrol for OA treatment.

Methods

First, the differentially expressed genes (DEGs) of OA joint tissues were obtained from the related microarray gene expression data. Second, resveratrol, a natural polyphenol compound, was used to screen the drug treatment target genes. Third, the drug-disease network was established, and the resveratrol target genes for OA treatment were obtained and verified through experimental verification.

Results

A total of 300 differentially expressed genes with 246 upregulated and 54 downregulated were found in OA joint tissues, and 310 resveratrol potential target genes were obtained. Finally, six genes, namely, CXCL1, HIF1A, IL-6, MMP3, NOX4, and PTGS2, were selected to validate the treatment effects of the resveratrol. The results showed that all six genes in human OA chondrocytes were significantly increased. In addition, in these chondrocytes, CXCL1, HIF1A, IL-6, MMP3, NOX4, and PTGS2 were reduced considerably, but HIF1A was significantly increased after resveratrol treatment.

Conclusions

Our data indicates that CXCL1, HIF1A, IL-6, MMP3, NOX4, and PTGS2 are all targets of resveratrol therapy. Our findings may provide valuable information for the mechanism and therapeutic of OA.

In Vivo Investigation of the Ameliorating Effect of Tempol against MIA-Induced Knee Osteoarthritis in Rats: Involvement of TGF-β1/SMAD3/NOX4 Cue

Osteoarthritis (OA) is a complex disease characterized by structural, functional, and metabolic deteriorations of the whole joint and periarticular tissues. In the current study, we aimed to investigate the possible effects of tempol on knee OA induced by the chemical chondrotoxic monosodium iodoacetate (MIA) which closely mimics both the pain and structural changes associated with human OA. Rats were administrated oral tempol (100 mg/kg) one week post-MIA injection (3 mg/50 μL saline) at the right knee joints for 21 consecutive days. Tempol improved motor performance and debilitated the MIA-related radiological and histological alterations. Moreover, it subsided the knee joint swelling. Tempol decreased the cartilage degradation-related biomarkers as matrix metalloproteinase-13, bone alkaline phosphatase (bone ALP), and fibulin-3. The superoxide dismutase mimetic effect of tempol was accompanied by decreased NADPH oxidase 4 (NOX4), inflammatory mediators, nuclear factor-kappa B (NF-κB), over-released transforming growth factor-β1 (TGF-β1). Tempol decreased the expression of chemokine (C-C motif) ligand 2 (CCL2). On the molecular level, tempol reduced the phosphorylated protein levels of p38 mitogen-activated protein kinase (MAPK), and small mother against decapentaplegic 3 homologs (SMAD3). These findings suggest the promising role of tempol in ameliorating MIA-induced knee OA in rats via collateral suppression of the catabolic signaling cascades including TGF-β1/SMAD3/NOX4, and NOX4/p38MAPK/NF-κB and therefore modulation of oxidative stress, catabolic inflammatory cascades, chondrocyte metabolic homeostasis.

Prevention of posttraumatic osteoarthritis at the time of injury: Where are we now, and where are we going?

This overview of progress made in preventing post-traumatic osteoarthritis (PTOA) was delivered in a workshop at the Orthopaedics Research Society Annual Conference in 2019. As joint trauma is a major risk factor for OA, defining the molecular changes within the joint at the time of injury may enable the targeting of biological processes to prevent later disease. Animal models have been used to test therapeutic targets to prevent PTOA. A review of drug treatments for PTOA in rodents and rabbits between 2016 and 2018 revealed 11 systemic interventions, 5 repeated intra-articular or topical interventions, and 5 short-term intra-articular interventions, which reduced total Osteoarthritis Research Society International scores by 30%-50%, 20%-70%, and 0%-40%, respectively. Standardized study design, reporting of effect size, and quality metrics, alongside a "whole joint" approach to assessing efficacy, would improve the translation of promising new drugs. A roadblock to translating preclinical discoveries has been the lack of guidelines on the design and conduct of human trials to prevent PTOA. An international workshop addressing this in 2016 considered inclusion criteria and study design, and advocated the use of experimental medicine studies to triage candidate treatments and the development of early biological and imaging biomarkers. Human trials for the prevention of PTOA have tested anakinra after anterior cruciate ligament rupture and dexamethasone after radiocarpal injury. PTOA offers a unique opportunity for defining early mechanisms of OA to target therapeutically. Progress in trial design and high-quality preclinical research, and allegiance with patients, regulatory bodies, and the pharmaceutical industry, will advance this field.

ROS-Sensitive Nanoparticles Co-delivering Dexamethasone and CDMP-1 for the Treatment of Osteoarthritis Through Chondrogenic Differentiation Induction and Inflammation Inhibition

Objective: Osteoarthritis (OA) is a common subtype of arthritis. To date, treatment of OA focuses primarily on alleviating pain and improving joint function. The lack of a vascular system within synovial joints and the rapid removal of agents due to synovial exchange hinder continuous delivery of OA drugs. However, these obstacles are being addressed by promising nanoscale drugs.

Methods: We synthesize and assemble a hydrogen peroxide [H₂O₂, belongs to the category of active oxygen species (ROS)]-sensitive nanomicelle, which is loaded with the anti-inflammation drug dexamethasone and chondrogenic differentiation factor cartilage-derivedmor-phogeneticprotein-1. The micelle can induce bone marrow mesenchymal stem cells to repair cartilage while inhibiting joint inflammation.

Results: The prepared nanoparticles were of uniform size and displayed an obvious core-shell structure. Under H₂O₂ stimulation, the shell layer could be removed gradually. The drug-loaded micelle effectively inhibited proliferation of activated macrophages, induced macrophage apoptosis with an anti-inflammatory effect, and caused the BMSCs to differentiate into chondrocytes.

Conclusion: This work provides an experimental and theoretical basis for further development of a drug-loaded micelle in the healing of osteoarthritis.

NADPH oxidases in bone and cartilage homeostasis and disease: A promising therapeutic target

Reactive oxygen species (ROS) generated by the NADPH oxidase (Nox) enzymes are important short-range signaling molecules. They have been extensively studied in the physiology and pathophysiology of the cardiovascular system, where they have important roles in vascular inflammation, angiogenesis, hypertension, cardiac injury, stroke, and aging. Increasing evidence demonstrates that ROS and Nox enzymes also affect bone homeostasis and osteoporosis, and more recent studies implicate ROS and Nox enzymes in both inflammatory arthritis and osteoarthritis. Mechanistically, this connection may be through the effects of ROS on signal transduction. ROS affect both transforming growth factor-β/Smad signaling, interleukin-1β/nuclear factor-kappa B signaling, and the resulting changes in matrix metalloproteinase expression. The purpose of this review is to describe the role of Nox enzymes in the physiology and pathobiology of bone and joints and to highlight the potential of therapeutically targeting the Nox enzymes.

The evaluation of oxidative stress in osteoarthritis

Osteoarthritis (OA) is a whole joint disease driven by abnormal biomechanics and attendant cell-derived and tissue-derived factors. The disease is multifactorial and polygenic, and its progression is significantly related to oxidative stress and reactive oxygen species (ROS). Augmented ROS generation can cause the damage of structural biomolecules of the joint and, by acting as intracellular signaling component, ROS are associated with various inflammatory responses. By activating several signaling pathways, ROS have a vital importance in the patho-physiology of OA. This review is focused on the mechanism of ROS which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation, along with synovial inflammation and dysfunction of the subcondral bone, targeting the complex oxidative stress signaling pathways.