Anabolic/Catabolic balance in pathogenesis of osteoarthritis: identifying molecular targets

MMP13-targeted siRNA-loaded micelles for diagnosis and treatment of posttraumatic osteoarthritis

Posttraumatic osteoarthritis (PTOA) patients are often diagnosed by X-ray imaging at a middle-late stage when drug interventions are less effective. Early PTOA is characterized by overexpressed matrix metalloprotease 13 (MMP13). Herein, we constructed an integrated diagnosis and treatment micelle modified with MMP13 enzyme-detachable, cyanine 5 (Cy5)-containing PEG, black hole quencher-3 (BHQ3), and cRGD ligands and loaded with siRNA silencing MMP13 (siM13), namely ERMs@siM13. ERMs@siM13 could be cleaved by MMP13 in the diseased cartilage tissues to detach the PEG shell, causing cRGD exposure. Accordingly, the ligand exposure promoted micelle uptake by the diseased chondrocytes by binding to cell surface αvβ3 integrin, increasing intracellular siM13 delivery for on-demand MMP13 downregulation. Meanwhile, the Cy5 fluorescence was restored by detaching from the BHQ3-containing micelle, precisely reflecting the diseased cartilage state. In particular, the intensity of Cy5 fluorescence generated by ERMs@siM13 that hinged on the MMP13 levels could reflect the PTOA severity, enabling the physicians to adjust the therapeutic regimen. Finally, in the murine PTOA model, ERMs@siM13 could diagnose the early-stage PTOA, perform timely interventions, and monitor the OA progression level during treatment through a real-time detection of MMP13. Therefore, ERMs@siM13 represents an appealing approach for early-stage PTOA theranostics.

Effects of Pomegranate (Punica granatum L.) Peel Extract Supplementation on Markers of Inflammation and Serum Matrix Metalloproteinase 1 in Women With Knee Osteoarthritis: A Randomized Double-Blind Placebo-Controlled Study

Objective

Osteoarthritis (OA) as a common musculoskeletal disorder is the main cause of disability in the world. The present study aimed to evaluate the effects of pomegranate peel extract (PPE) on some inflammatory markers and matrix maloproteinase1 (MMP1) in women with knee OA.

Methods

Sixty obese women with knee OA aged 38 to 60 years were included in this clinical trial. The women were allocated into intervention (n = 30) and placebo (n = 30) groups along with standard drug therapy receiving 500 mg PPE or placebo twice daily for 8 weeks, respectively. Three-day food records, anthropometric measurements, fasting blood samples, and physical activity questionnaires were gathered at the baseline and the end of the study.

Results

The supplementation of PPE significantly reduced the serum high-sensitivity C-reactive protein (hs-CRP), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB), MMP1, and monocyte chemoattractant protein-1 (MCP-1) levels of the patients within the intervened group (all, P < .05) and compared with the placebo (P = .002, .045, .040, and .003, respectively) at the end of the study. The serum NF-ĸB levels significantly increased within the placebo group at the end of the trial (P = .002). Changes in other variables in the placebo group were not significant (P > .05).

Conclusions

The findings of this clinical trial indicated that PPE supplementation decreased serum inflammatory markers including hs-CRP, NF-ĸB, and MCP-1 and MMP1 levels in women with knee OA. PPE supplementation may be useful as a part of an integrated approach to modulating inflammatory complications in women with knee OA.

Piezo1 mediates the degradation of cartilage extracellular matrix in malocclusion-induced TMJOA

OBJECTIVES

To evaluate the role of Piezo1 in the malocclusion-induced osteoarthritic cartilage of the temporomandibular joint.

METHODS

A temporomandibular joint osteoarthritis model was established using a unilateral anterior crossbite in vivo, and cartilage degeneration and Piezo1 expression were observed by histological and immunohistochemical staining. ATDC5 cells were loaded with 24 dyn/cm2 fluid flow shear stress using the Flexcell device in vitro and expression and function of Piezo1 were evaluated. After identifying the function of Piezo1 in YAP translocation under FFSS conditions, the influence of Piezo1 and YAP on metabolism-related enzymes under FFSS was detected through a real-time polymerase chain reaction analysis and western blotting. A UAC-TMJ injection model was established to observe the therapeutic effect of intra-articular injection of a Piezo1 inhibitor on osteoarthritic cartilage matrix loss.

RESULTS

Piezo1 was overexpressed in the osteoarthritic cartilage and cultured chondrocytes under shear stress. Piezo1 Silencing inhibited the nuclear translocation of YAP and subsequently downregulated the expression of MMP13 and ADAMTS5. Intra-articular injection of the Piezo1 inhibitor, GsMTx4, could ameliorate proteoglycan degradation in malocclusion-induced TMJOA and suppressed MMP13 and ADAMTS5 expression.

CONCLUSIONS

Our results revealed that the activation of Piezo1 promotes mechanical-induced cartilage degradation through the YAP-MMP13/ADAMTS5 signaling pathway.

Chondrocyte targeting gold nanoparticles protect growth plate against inflammatory damage by maintaining cartilage balance

Cartilage destruction caused by inflammation is a clinical challenge. Many studies have investigated cartilage destruction in adults, but little research was conducted on children. In this study, the protective effect of gold nanoparticles (AuNPs) on the cartilage of children was realized by counteracting chondrocyte apoptosis and extracellular matrix (ECM) degradation in a young mouse model of lipopolysaccharide (LPS)-induced growth plate (GP) cartilage damage. Initially, engineered AuNPs can be efficiently absorbed by chondrocytes, approximately 20 times the amount absorbed by macrophages, resulting in a 29% ± 0.05% increase in chondrocyte viability. Then, AuNPs exposure significantly reduced the release of inflammatory cytokines and secretion of ECM degradation factors induced by LPS. Subsequently, AuNPs were applied to resist LPS-induced cartilage destruction in young mice. AuNPs inhibited the formation of gaps, without chondrocytes and extracellular matrix, between the proliferative and hypertrophy zones of the GP cartilage, and the gaps were noticeable in the LPS group. This finding can be attributed to the capability of AuNPs to reduce the LPS-induced apoptosis rate of mouse chondrocytes by 72.38% and the LPS-induced ECM degradation rate by 70.89%. Further analysis demonstrated that remission is partly due to AuNPs' role in maintaining the balance of catabolic and anabolic factors in the ECM. Altogether, these findings indicate that AuNPs can partially protect the cartilage of children from inflammatory damage by suppressing chondrocyte apoptosis and ECM degradation.

Cartilage organoids and osteoarthritis research: a narrative review

Osteoarthritis (OA) is one of the most common degenerative joint diseases, significantly impacting individuals and society. With the acceleration of global aging, the incidence of OA is increasing. The pathogenesis of osteoarthritis is not fully understood, and there is no effective way to alleviate the progression of osteoarthritis. Therefore, it is necessary to develop new disease models and seek new treatments for OA. Cartilage organoids are three-dimensional tissue masses that can simulate organ structure and physiological function and play an important role in disease modeling, drug screening, and regenerative medicine. This review will briefly analyze the research progress of OA, focusing on the construction and current development of cartilage organoids, and then describe the application of cartilage organoids in OA modeling, drug screening, and regeneration and repair of cartilage and bone defects. Finally, some challenges and prospects in the development of cartilaginous organoids are discussed.

Effects of low-intensity exercise on spontaneously developed knee osteoarthritis in male senescence-accelerated mouse prone 8

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease associated with aging, which often leads to joint stiffness and disability. Exercise is one of the most important non-pharmacological treatments and is prescribed as an indispensable treatment for OA. However, whether physical exercise is beneficial for preventing the progression of OA symptoms with age is poorly understood. We investigated the effects of exercise on spontaneously developed knee OA using male senescence-accelerated mouse prone 8 (SAMP8).

METHODS

To examine age-related changes in the knee joints of SAMP8, knee articular cartilage changes, synovitis, knee joint flexion and extension angles, swelling, walking ability, and quadriceps muscle atrophy were analyzed at 3, 5, 7, and 9 months. SAMP8 were required to run at a speed of 10 m/min for 15 min/day from 7 to 9 months of age. The knee joint pathologies and symptoms of exercising and non-exercising mice were compared by histological, immunohistochemical, and morphometrical analyses.

RESULTS

The mice presented with various histological changes, including cartilage destruction, osteocyte formation, synovitis, declined joint angles, and swelling. Notably, medial and posterior cartilage destruction was more severe than that of the lateral and anterior cartilage. Knee joint angles were significantly correlated with the histological scores (modified Mankin and OARSI, osteophyte formation and synovial lining cell layer). Exercise did not attenuate cartilage degeneration in the medial and posterior tibial plateau, although the articular cartilage of the anterior and lateral tibial plateau and its histological scores was remained and significantly improved, respectively, by exercise. Exercise suppressed the age-related decline of collagen type II-positive areas in the remaining articular cartilage and improved the OA symptoms. Exercise reduced the expression of monocyte chemoattractant protein (MCP)-1 and tumor necrosis factor (TNF)-α positive macrophages in the synovium.

CONCLUSION

This study revealed that SAMP8 developed spontaneous knee OA with age, which resembled the disease symptoms in humans. Low-intensity exercise temporarily alleviated degeneration of the remaining cartilage, synovitis, and age-related decreases in knee flexion angle, stride length, and muscle atrophy in SAMP8. However, exercise during OA progression with age may cause mechanical stress that could be both beneficial and detrimental to joint health.

The Role of Matrix Metalloproteinase 13 and Vitamin D in Osteoarthritis: A Hospital-Based Observational Study

Introduction Osteoarthritis (OA) is the most common form of degenerative joint disease characterized by the progressive degeneration of articular cartilage, osteophyte formation, and joint space narrowing. Matrix metalloproteinases (MMPs) are potential biomarkers for osteoarthritis. Aims and objective The study's aim is the estimation of serum and synovial fluid matrix metalloproteinase (MMP) 13 and serum vitamin D levels in the grade 3 and grade 4 stages of osteoarthritis according to the Kellgren and Lawrence (KL) system of classification. Materials and methods A total of 100 subjects were included; of them, 25 patients with grade 3 and 25 patients with grade 4 knee osteoarthritis diagnosed clinically and radiologically according to the Kellgren and Lawrence criteria have been enrolled in the study, and 50 patients with knee pain having a diagnosis other than degenerative OA of the knee were taken as controls. Venous blood and synovial fluid have been collected from all of them for the estimation of MMP-13 and vitamin D. The enzyme-linked immunosorbent assay (ELISA) and chemiluminescent microparticle immunoassay (CMIA) methods were used for the estimation of MMP-13 and vitamin D, respectively. Results The mean value of synovial fluid MMP-13 was found to be elevated in grade 4 as compared to grade 3 and the control group, whereas the mean value of serum MMP-13 was found to be elevated in grade 3 as compared to grade 4 and control. The level of serum vitamin D was found deficient in OA patients as compared to control. The Kruskal-Wallis test was performed to compare these groups, and there was a significant difference between these groups (p-value of <0.05). Summary and conclusion High synovial and serum MMP-13 is associated with knee structural abnormalities in patients with knee OA as compared to the control group suggesting that MMP-13 can be a biomarker in knee OA, whereas the decreased level of vitamin D may be associated with an increased risk for the progression of OA; hence, serum vitamin D may be a good indicator for the prediction of the initiation of OA.

Formononetin, a Beer Polyphenol with Catabolic Effects on Chondrocytes

Beer consumption has been identified as a risk factor for osteoarthritis (OA), a rheumatic disease characterised by cartilage degradation, joint inflammation, and eventual joint failure. One of the main isoflavonoids in beer is formononetin (FNT), an estrogenic compound also found in multiple plants and herbs. In this study, we aimed to investigate the effect of FNT on chondrocyte viability, inflammation, and metabolism. Cells were treated with FNT with or without IL-1β for 48 h and during 7 days of differentiation. Cell viability was determined via MTT assay. Nitrite accumulation was determined by Griess reaction. The expression of genes involved in inflammation and metabolism was determined by RT-PCR. The results revealed that a low concentration of FNT had no deleterious effect on cell viability and decreased the expression of inflammation-related genes. However, our results suggest that FNT overexposure negatively impacts on chondrocytes by promoting catabolic responses. Finally, these effects were not mediated by estrogen receptors (ERs) or aryl hydrocarbon receptor (AhR). In conclusion, factors that favour FNT accumulation, such as long exposure times or metabolic disorders, can promote chondrocyte catabolism. These data may partially explain why beer consumption increases the risk of OA.

Meloxicam emulgel potently suppressed cartilage degradation in knee osteoarthritis: Optimization, formulation, industrial scalability and pharmacodynamic analysis

BACKGROUND AND OBJECTIVE

Meloxicam (MLX) is prescribed for the management of pain and inflammation allied with osteoarthritis (OA). However, MLX causes intestinal damage in long term administration. Hence, meloxicam loaded emulgel (MLX-emulgel) was optimized, formulated and examined under stringent parameters in monosodium-iodoacetate (MIA) induced knee OA in Wistar rats.

METHODS AND RESULTS

Nanoemulsion of MLX was fabricated by ultrasonication and microfluidization method with a droplet size of 66.81 ± 5.31-nm and zeta potential of -24.6 ± 0.72-mV. Further, MLX nanoemulsion was optimized with centrifugation, heating-cooling cycles and transmittance parameters in addition to scale-up feasibility with microfluidizer. Post optimization, MLX-nanoemulsion was tailored as emulgel with Carbopol Ultrez 10 NF and assessed for pH, rheology, textural properties, assay and stability features. The in-vitro release study revealed the Korsmeyer-Peppas release kinetics and ex-vivo skin permeation was improved by 6.71-folds. The skin distribution of MLX-emulgel evinced the transfollicular mode of permeation. In-vivo study indicated the protective action of MLX-emulegl expressed in terms of inflammatory cyctokines level, X-ray analysis of knee joints of rats, histopathology and OARSI (Osteoarthritis Research Society International) scoring. MLX-emulgel treated group displayed lower (P < 0.001) level of COX-2 intensity as compared to positive control group. However, it was comparable (P > 0.05) to the normal control group, MLX oral dispersion, i.v. solution and etoricoxib gel groups. MLX-emulgel showcased an alternative to the long term usage of analgesics for relieving the symptoms of knee OA.

CONCLUSION

MLX-emulgel may be a potential candidate for translating in to a clinically viable dosage form in the management of knee OA.

Micronutrient optimization for tissue engineered articular cartilage production of type II collagen

Tissue Engineering of cartilage has been hampered by the inability of engineered tissue to express native levels of type II collagen in vitro. Inadequate levels of type II collagen are, in part, due to a failure to recapitulate the physiological environment in culture. In this study, we engineered primary rabbit chondrocytes to express a secreted reporter, Gaussia Luciferase, driven by the type II collagen promoter, and applied a Design of Experiments approach to assess chondrogenic differentiation in micronutrient-supplemented medium. Using a Response Surface Model, 240 combinations of micronutrients absent in standard chondrogenic differentiation medium, were screened and assessed for type II collagen promoter-driven Gaussia luciferase expression. While the target of this study was to establish a combination of all micronutrients, alpha-linolenic acid, copper, cobalt, chromium, manganese, molybdenum, vitamins A, E, D and B7 were all found to have a significant effect on type II collagen promoter activity. Five conditions containing all micronutrients predicted to produce the greatest luciferase expression were selected for further study. Validation of these conditions in 3D aggregates identified an optimal condition for type II collagen promoter activity. Engineered cartilage grown in this condition, showed a 170% increase in type II collagen expression (Day 22 Luminescence) and in Young's tensile modulus compared to engineered cartilage in basal media alone.Collagen cross-linking analysis confirmed formation of type II-type II collagen and type II-type IX collagen cross-linked heteropolymeric fibrils, characteristic of mature native cartilage. Combining a Design of Experiments approach and secreted reporter cells in 3D aggregate culture enabled a high-throughput platform that can be used to identify more optimal physiological culture parameters for chondrogenesis.

Anatomy, molecular structures, and hyaluronic acid - Gelatin injectable hydrogels as a therapeutic alternative for hyaline cartilage recovery: A review

Cartilage damage caused by trauma or osteoarthritis is a common joint disease that can increase the social and economic burden in society. Due to its avascular characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Hydrogels have been developed into one of the most suitable biomaterials for the regeneration of cartilage because of its characteristics such as high-water absorption, biodegradation, porosity, and biocompatibility similar to natural extracellular matrix. Therefore, the present review article presents a conceptual framework that summarizes the anatomical, molecular structure and biochemical properties of hyaline cartilage located in long bones: articular cartilage and growth plate. Moreover, the importance of preparation and application of hyaluronic acid - gelatin hydrogels for cartilage tissue engineering are included. Hydrogels possess benefits of stimulating the production of Agc1, Col2α1-IIa, and SOX9, molecules important for the synthesis and composition of the extracellular matrix of cartilage. Accordingly, they are believed to be promising biomaterials of therapeutic alternatives to treat cartilage damage.

Prognostic Factors for the Clinical Outcome after Microfracture Treatment of Chondral and Osteochondral Defects in the Knee Joint: A Systematic Review

OBJECTIVE

The objective of this study is to establish which patient and lesion characteristics are related to the clinical outcome after microfracture of cartilage defects in the knee.

STUDY DESIGN

Systematic review.

METHODS

After preregistration, PubMed, Embase, and Cochrane were searched for studies that analyzed prognostic factors for the outcome of microfracture treatment in the knee. The criteria for inclusion were outcome measured using Patient-Reported Outcome Measures (PROMs), a clinical study with ≥10 participants receiving microfracture, and a minimal follow-up period of 1 year.

RESULTS

For none of the investigated prognostic factors, effect size reporting was sufficiently homogeneous to conduct a meta-analysis. However, a majority of the included studies identified higher age, larger lesion size, longer preoperative symptom duration, and previous surgery on the ipsilateral knee, especially meniscectomy and anterior cruciate ligament reconstruction, as factors that are reported to be correlated to a less favorable outcome. A lesion location that does not include the trochlea or the patellofemoral joint and is not weightbearing, a nondegenerative mechanism of injury, and a single lesion were reported as factors that predict a favorable outcome. As to gender, body mass index, preoperative activity level, smoking, and concomitant knee surgery, the included articles were inconclusive or no effect was reported.

CONCLUSIONS

Several factors correlated with the clinical result after microfracture treatment. However, the information on the effect sizes of the influence on clinical outcome is incomplete due to poor reporting. Large-scale registries or pooling of homogeneous, well-reported data is needed to work toward prognostic models. That would be an important step toward personalized treatment.

Indirubin protects chondrocytes and alleviates OA by inhibiting the MAPK and NF-κB pathways

PHARMACOLOGICAL RELEVANCE

Indirubin (IR) is a key active ingredient in the traditional Chinese medication QingDai, also called indigo naturalis, which are extensively used in China to treat chronic diseases, such as inflammation and cancer. However, the function of IR in reducing chondrocyte inflammation in osteoarthritis (OA) is still unclear.

AIM OF THE STUDY

The aim of this research was to examine how IR inhibits arthritis and to highlight some of its cellular-level processes.

MATERIALS AND METHODS

Chondrocytes from the knee joint of C57 mice were gathered and grown for in vitro tests and used to determine the toxicity of IR toward chondrocytes using a CCK8 kit. Chondrocytes were treated with IL-1β and IR or with IL-1β alone, and western blotting was used to determine the expression levels of inflammatory mediators. Meanwhile, through the identification and examination of pertinent markers via quantitative PCR. By using PCR assays, western blotting, toluidine blue staining and safranin O staining, the expression of proteoglycan (AGG) and type II collagen (collagen II) was investigated. Furthermore, western blotting was used to detect activation of the NF-κB and MAPK signaling pathways, and immunofluorescence was used to detect p65 nuclear translocation. In an in vivo experiment, C57BL/6 mice were subjected to destabilization of the medial meniscus (DMM) surgery to produce an OA model, and IR was injected into the articular cavity for 8 weeks. Eventually, the mice were killed, and samples of the knee joints were obtained for histological examination and analysis.

RESULTS

IR significantly reduced the expression of inflammatory regulators in chondrocytes treated with IL-1β, including iNOS and COX-2. Inhibition of IL-1β induced production of the key catabolic enzymes MMP3, MMP13 and A5. Additionally, an improvement in the downregulation of collagen II and AGG expression was observed. Moreover, IR prevented the aberrant IL-1β-induced activation of the NF-κB and MAPK signaling pathways, which resulted in downregulation of p65 and p38 expression. Compared to the DMM group, the severity of cartilage injury in animals was dramatically lessened and OARSI scores were lower in the treated groups.

CONCLUSION

According to the above findings, IR is quite effective in preventing arthritis both in vivo and in vitro, suggesting that IR may be employed as a possible anti-arthritis drug.

Dendrobine Alleviates Cellular Senescence and Osteoarthritis via the ROS/NF-κB Axis

Osteoarthritis (OA) is a degenerative joint disease characterized by low-grade inflammation and cartilage degradation. Dendrobine (DEN) is reported to inhibit inflammation and oxidative stress in some diseases, but its role in chondrocyte senescence and OA progress has not yet been elucidated. Our study aimed to explore the protective effects of DEN on OA both in vitro and in vivo. We found that DEN inhibited extracellular matrix (ECM) degradation and promoted ECM synthesis. Meanwhile, DEN inhibited senescence-associated secretory phenotype (SASP) factors expression and senescence phenotype in IL-1β-treated chondrocytes. Furthermore, DEN improved mitochondrial function and reduced the production of intracellular reactive oxygen species (ROS). Also, DEN suppressed IL-1β-induced activation of the NF-κB pathway. Further, using NAC (ROS inhibitor), we found that DEN might inhibit NF-κB cascades by reducing ROS. Additionally, X-ray, micro-CT, and histological analyses in vivo demonstrated that DEN significantly alleviated cartilage inflammation, ECM degradation, and subchondral alterations in OA progression. In conclusion, DEN inhibits SASP factors expression and senescence phenotype in chondrocytes and alleviated the progression of OA via the ROS/NF-κB axis, which provides innovative strategies for the treatment of OA.

Silencing miR-146a-5p Protects against Injury-Induced Osteoarthritis in Mice

Osteoarthritis (OA), the most prevalent joint disease and the leading cause of disability, remains an incurable disease largely because the etiology and pathogenesis underlying this degenerative process are poorly understood. Low-grade inflammation within joints is a well-established factor that disturbs joint homeostasis and leads to an imbalance between anabolic and catabolic processes in articular cartilage; however, the complexity of the network between inflammatory factors that often involves positive and negative feedback loops makes current anti-cytokine therapy ineffective. MicroRNAs (miRNAs) have emerged as key regulators to control inflammation, and aberrant miRNAs expression has recently been linked to OA pathophysiology. In the present study, we characterized transcriptomic profiles of miRNAs in primary murine articular chondrocytes in response to a proinflammatory cytokine, IL-1β, and identified miR-146a-5p as the most responsive miRNA to IL-1β. miR-146a-5p was also found to be upregulated in human OA cartilage. We further demonstrated that knockdown of miR-146a-5p antagonized IL-1β-mediated inflammatory responses and IL-1β-induced catabolism in vitro, and silencing of miR-146a in chondrocytes ameliorated articular cartilage destruction and reduced OA-evoked pain in an injury-induced murine OA model. Moreover, parallel RNA sequencing revealed that differentially expressed genes in response to IL-1β were enriched in pathways related to inflammatory processes, cartilage matrix homeostasis, and cell metabolism. Bioinformatic analyses of putative miR-146a-5p gene targets and following prediction of protein-protein interactions suggest a functional role of miR-146a-5p in mediating inflammatory processes and regulation of cartilage homeostasis. Our genetic and transcriptomic data define a crucial role of miR-146a-5p in OA pathogenesis and implicate modulation of miR-146a-5p in articular chondrocytes as a potential therapeutic strategy to alleviate OA.

An In Vitro Engineered Osteochondral Model as Tool to Study Osteoarthritis Environment

Osteoarthritis (OA) is a joint degenerative pathology characterized by mechanical and inflammatory damages affecting synovium, articular cartilage (AC), and subchondral bone (SB). Several in vitro, in vivo, and ex vivo models are developed to study OA, but to date the identification of specific pharmacological targets seems to be hindered by the lack of models with predictive capabilities. This study reports the development of a biomimetic in vitro model of AC and SB interface. Gellan gum methacrylated and chondroitin sulfate/dopamine hydrogels are used for the AC portion, whereas polylactic acid functionalized with gelatin and nanohydroxyapatite for the SB. The physiological behavior of immortalized stem cells (Y201s) and Y201s differentiated in chondrocytes (Y201-Cs), respectively, for the SB and AC, is demonstrated over 21 days of culture in vitro in healthy and pathological conditions, whilst modeling the onset of cytokines-induced OA. The key metrics are: lower glycosaminoglycans production and increased calcification given by a higher Collagen X content, in the AC deep layer; higher expression of pro-angiogenic factor (vegf) and decreased expression of osteogenic markers (coll1, spp1, runx2) in the SB. This novel approach provides a new tool for studying the development and progression of OA.

Natural Compounds: Potential Therapeutics for the Inhibition of Cartilage Matrix Degradation in Osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disease characterized by enzymatic degradation of the cartilage extracellular matrix (ECM) causing joint pain and disability. There is no disease-modifying drug available for the treatment of OA. An ideal drug is expected to stop cartilage ECM degradation and restore the degenerated ECM. The ECM primarily contains type II collagen and aggrecan but also has minor quantities of other collagen fibers and proteoglycans. In OA joints, the components of the cartilage ECM are degraded by matrix-degrading proteases and hydrolases which are produced by chondrocytes and synoviocytes. Matrix metalloproteinase-13 (MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs 4 and 5 (ADAMTS5) are the major collagenase and aggrecanase, respectively, which are highly expressed in OA cartilage and promote cartilage ECM degradation. Current studies using various in vitro and in vivo approaches show that natural compounds inhibit the expression and activity of MMP-13, ADAMTS4, and ADAMTS5 and increase the expression of ECM components. In this review, we have summarized recent advancements in OA research with a focus on natural compounds as potential therapeutics for the treatment of OA with emphasis on the prevention of cartilage ECM degradation and improvement of joint health.

Osteochondral regenerative engineering: challenges, state-of-the-art and translational perspectives

Despite quantum leaps, the biomimetic regeneration of cartilage and osteochondral regeneration remains a major challenge, owing to the complex and hierarchical nature of compositional, structural and functional properties. In this review, an account of the prevailing challenges in biomimicking the gradients in porous microstructure, cells and extracellular matrix (ECM) orientation is presented. Further, the spatial arrangement of the cues in inducing vascularization in the subchondral bone region while maintaining the avascular nature of the adjacent cartilage layer is highlighted. With rapid advancement in biomaterials science, biofabrication tools and strategies, the state-of-the-art in osteochondral regeneration since the last decade has expansively elaborated. This includes conventional and additive manufacturing of synthetic/natural/ECM-based biomaterials, tissue-specific/mesenchymal/progenitor cells, growth factors and/or signaling biomolecules. Beyond the laboratory-based research and development, the underlying challenges in translational research are also provided in a dedicated section. A new generation of biomaterial-based acellular scaffold systems with uncompromised biocompatibility and osteochondral regenerative capability is necessary to bridge the clinical demand and commercial supply. Encompassing the basic elements of osteochondral research, this review is believed to serve as a standalone guide for early career researchers, in expanding the research horizon to improve the quality of life of osteoarthritic patients affordably.

Identification of the OA-related metabolism-related genes, corresponding transcription factors, relevant pathways, and specific bioactive small molecules

Metabolic alteration of articular cartilage is associated with the pathogenesis of Osteoarthritis (OA). This study aims to identify the metabolism-related genes, corresponding transcription factors (TFs), and relevant pathways. Overall, RNA sequencing profiles of articular cartilage were collected from the GEO database. Metabolism-related genes and OA-related hallmarks were collected from the MSigDB v7.1. Differential expression analysis, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and Gene Set Variation Analysis (GSVA) were conducted to identify pathways or hallmarks that were related to the pathogenesis of OA. The Pearson correlation analysis was used to establish the regulatory network among transcription factors, metabolism-related genes, and hallmarks. To further confirm the regulation of the identified transcription factors, Chromatin Immunoprecipitation-sequencing (ChIP-seq) was conducted, and single-cell sequencing was used to locate the cell clusters. Connectivity Map (CM) analysis were also conducted to identify the potential specific bioactive small molecules targeting the metabolic alteration of osteoarthritis. scTPA database was used to detect activated signaling pathways. Collectively, a total of 74 and 38 differentially expressed metabolism-related genes and TFs were retrieved. Skeletal system development, extracellular matrix, and cell adhesion molecule binding were important pathways in GO analysis. Human papillomavirus infection, PI3K-Akt signaling pathway, and Human T-cell leukemia virus 1 infection were the top 3 pathways in KEGG. 7 and 12 hallmarks were down- and up-regulated in GSVA, respectively. Ten bioactive small molecules may be potential treatments of OA by regulating the metabolism of articular cartilage. ChIP-seq analysis showed high relativity between transcription factors and their target genes. Furthermore, single-cell sequencing confirms the high expression of identified transcription factors in chondrocytes. To conclude, we established a comprehensive network integrated with transcription factors, metabolism-related genes, and hallmarks.

Characterization of Non-Invasively Induced Post-Traumatic Osteoarthritis in Mice

The pathophysiology of post-traumatic arthritis (PTOA) is not fully understood. This study used non-invasive repetitive mechanical loading (ML) mouse models to study biochemical, biomechanical, and pain-related behavioral changes induced in mice. Mouse models reflected the effects of the early stages of PTOA in humans. For the PTOA model, cyclic comprehensive loading (9N) was applied to each mouse’s left knee joint. ML-induced biochemical and molecular changes were analyzed after loading completion. Cartilage samples were examined using gene expression analysis. Tissue sections were used in subsequent OA severity scoring. Biomechanical features and pain-related behavior were studied after 24 h and three weeks post-ML sessions to examine the development of PTOA. The loaded left knee joint showed a greater ROS/RNS signal than the right knee, which was not loaded. There was a significant increase in cartilage damage and MMP activity in the mechanically loaded joints relative to non-loaded control knee joints. Similarly, we found a difference in the viscoelastic tangent, which highlights significant changes in mechanical properties. Biochemical analyses revealed significant increases in total NO, caspase-3 activity, H₂O₂, and PGE2 levels. Gene expression analysis highlighted increased catabolism (MMP-13, IL-1β, TNF-α) with a concomitant decrease in anabolism (ACAN, COL2A1). Histopathology scores clearly indicated increases in OA progression and synovitis. The gait pattern was significantly altered, suggesting signs of joint damage. This study showed that biomechanical, biochemical, and behavioral characteristics of the murine PTOA groups are significantly different from the control group. These results confirm that the current mouse model can be considered for translational PTOA studies.

A systematic review on the potential value of synovial fluid biomarkers to predict clinical outcomes in cartilage repair treatments

OBJECTIVE

Multiple biochemical biomarkers have been previously investigated for the diagnosis, prognosis and response to treatment of articular cartilage damage, including osteoarthritis (OA). Synovial fluid (SF) biomarker measurement is a potential method to predict treatment response and effectiveness. However, the significance of different biomarkers and their correlation to clinical outcomes remains unclear. This systematic review evaluated current SF biomarkers used in investigation of cartilage degeneration or regeneration in the knee joint and correlated these biomarkers with clinical outcomes following cartilage repair or regeneration interventions.

METHOD

PubMed, Institute of Science Index, Scopus, Cochrane Central Register of Controlled Trials, and Embase databases were searched. Studies evaluating SF biomarkers and clinical outcomes following cartilage repair intervention were included. Two researchers independently performed data extraction and Quality Assessment of Diagnostic Accuracy Score 2 (QUADAS-2) analysis. Biomarker inclusion, change following intervention and correlation with clinical outcome was compared.

RESULTS

9 studies were included. Study heterogeneity precluded meta-analysis. There was significant variation in sampling and analysis. 33 biomarkers were evaluated in addition to microRNA and catabolic/anabolic ratios. Five studies reported on correlation of biomarkers with six biomarkers significantly correlated with clinical outcomes following intervention. However, correlation was only demonstrated in isolated studies.

CONCLUSION

This review demonstrates significant difficulties in drawing conclusions regarding the importance of SF biomarkers based on the available literature. Improved standardisation for collection and analysis of SF samples is required. Future publications should also focus on clinical outcome scores and seek to correlate biomarkers with progression to further understand the significance of identified markers in a clinical context.

REGISTRATION NUMBER

PROSPERO CRD42022304298. Study protocol available on PROSPERO website.

SEMA6D, Negatively Regulated by miR-7, Contributes to C28/I2 chondrocyte's Catabolic and Anabolic Activities via p38 Signaling Pathway

MiR-7 has been recognized as an osteoarthritis (OA-)-promoting factor, but the specific downstream pathway of miR-7 still remains unknown. Further investigation of the molecular regulatory mechanism of miR-7 might help develop a novel therapeutic method for OA. In this study, we revealed that Semaphorin 6D (SEMA6D) was a direct target gene of miR-7 and presented a negative regulatory relation with SEMA6D in vitro and in vivo. SEMA6D could improve OA in rat OA models, as indicated by H&E and Safranin O-Fast green staining, and also μCT analysis. Further evaluation of SEMA6D suggested that SEMA6D promotes the anabolism and reduces the catabolism of C28/I2 chondrocytes via inhibiting the activation of the p38 pathway. The present research illustrated that SEMA6D is a negatively regulatory factor of miR-7 and a pivotal mediator of catabolism and anabolism in C28/I2 chondrocytes. SEMA6D exerts its function via inhibiting the activation of the p38 pathway.

Evaluation of the therapeutic and the chemical effects of balneological treatment on clinical and laboratory parameters in knee osteoarthritis: a randomized, controlled, single-blinded trial

The purpose of this study was to investigate the therapeutic and the chemical effects of balneological treatment (peloidotherapy + hydrotherapy), and its effects on serum levels of interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and insulin-like growth factor-1 (IGF-1) in patients with knee osteoarthritis (OA). Sixty-four (64) knee OA patients were randomly divided into study and control groups. Balneological treatment, consisting of hydrotherapy, and peloidotherapy were given to both groups. Unlike the study group, in the control group, the peloid was applied over a stretch film cover, preventing any contact between the skin and peloid. Clinical outcome measures of the study were pain degree, patient's and investigator's global assessment on visual analog scale (VAS-pain, VAS-PGA, VAS-IGA), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (pain, stiffness, and physical function). Patients were evaluated at baseline, post-treatment (after 10th session), and 3 and 6 months after treatment. Blood samples were taken at baseline, post- treatment, and 6 months after treatment for analysis of IL-1β, TNF-α, and IGF-1 serum levels. When compared with the baseline, VAS measurements decreased significantly in almost all evaluation periods in both groups, and no difference was observed between the groups. In the study group, WOMAC scores showed significant improvement in all assessments. In the control group, pain and physical function subscores of WOMAC significantly decreased at post-treatment and 3 months after treatment. In group comparison, pain and stiffness subscores showed a significant difference in favor of the study group at 6 months after treatment. No clinically significant improvement was seen in levels of IL-1β and IGF-1 in both groups during the whole assessment period. Because of TNF-α kit failure, we could not evaluate the measurements. In conclusion, balneological treatment is an effective treatment option to improve the pain and functional capacity of patients with knee OA. The application of peloid by contact with the skin is superior in the long-term period, which means that in addition to the thermal effect, the chemical content of peloid can also contribute to the therapeutic effect.

Estradiol Inhibits ER Stress-Induced Apoptosis in Chondrocytes and Contributes to a Reduced Osteoarthritic Cartilage Degeneration in Female Mice

Gender differences are a common finding in osteoarthritis (OA). This may result from a differential response of males and females to endoplasmic reticulum (ER) stress in articular chondrocytes. We have previously described that ER stress in cartilage-specific ERp57 KO mice (ERp57 cKO) favors the development of knee OA, since this stress condition cannot be adequately compensated in articular chondrocytes with increasing age leading to the induction of apoptotic cell death and subsequent cartilage degeneration. The aim of this study was to enlighten gender-specific differences in ER stress, apoptosis, and OA development in ERp57 cKO mice. The analyses were extended by in vitro studies on the influence of estradiol in CRISPR/Cas9-generated C28/I2 ERp57 knock out (KO) and WT cells. ER stress was evaluated by immunofluorescence analysis of the ER stress markers calnexin (Cnx) and binding-immunoglobulin protein (BiP), also referred to as glucose-regulating protein 78 (GRP78) in vivo and in vitro. Apoptotic cell death was investigated by a commercially available cell death detection ELISA and TUNEL assay. OA development in mice was analyzed by toluidine blue staining of paraffin-embedded knee cartilage sections and quantified by OARSI-Scoring. Cell culture studies exhibited a reduction of ER stress and ER stress-induced apoptosis in C28/I2 cells in presence of physiological estradiol concentrations. This is consistent with a slower increase in age-related ER stress and a reduced number of apoptotic chondrocytes in female mice compared to male littermates contributing to a reduced osteoarthritic cartilage degeneration in female mice. Taken together, this study demonstrates that the female sex hormone estradiol can reduce ER stress and ER stress-induced apoptosis in articular chondrocytes, thus minimizing critical events favoring osteoarthritic cartilage degeneration. Therefore, the inhibition of ER stress through a modulation of effects induced by female sex hormones appears to be attractive for OA therapy.

Rhoifolin ameliorates osteoarthritis via the Nrf2/NF-κB axis: in vitro and in vivo experiments

OBJECTIVE

Osteoarthritis (OA) is an age-related degenerative disease accompanied by an increasing number of senescent cells and chronic low-grade inflammation. Rhoifolin (ROF) showed considerable inhibition to inflammation, but its role in chondrocyte senescence and OA progress has not been fully characterized. We aimed to evaluate the protective effects of ROF on OA through a series of in vitro and in vivo experiments.

METHODS

The role of ROF in the expression of senescence-associated secretory phenotype (SASP) factors was investigated using RT-qPCR, western blotting, and ELISA. Chondrocyte senescence was assessed by SA-β-gal staining. We applied molecular docking to screen candidate proteins regulated by ROF. Meanwhile, SASP factors and cellular senescence were further assessed after the transfection of Nrf2 siRNA. In the anterior cruciate ligament transection (ACLT) rat model, X-ray, hematoxylin-eosin (HE), and Masson's staining were performed to evaluate the therapeutic effects of ROF on OA.

RESULTS

We found that ROF inhibited SASP factors expression and senescence phenotype in IL-1β-treated chondrocytes. Furthermore, ROF suppressed IL-1β-induced activation of the NF-κB pathway cascades. Also, molecular docking and knock-down studies demonstrated that ROF might bind to Nrf2 to suppress the NF-κB pathway. In vivo, ROF ameliorated the OA process in the ACLT rat model.

CONCLUSIONS

ROF inhibits SASP factors expression and senescence phenotype in chondrocytes and ameliorates the progression of OA via the Nrf2/NF-κB axis, which supports ROF as a potential therapeutic agent for the treatment of OA.

How Pyroptosis Contributes to Inflammation and Fibroblast-Macrophage Cross-Talk in Rheumatoid Arthritis

About thirty years ago, a new form of pro-inflammatory lytic cell death was observed and termed pyroptosis. Only in 2015, gasdermins were defined as molecules that create pores at the plasma membrane and drive pyroptosis. Today, we know that gasdermin-mediated death is an important antimicrobial defence mechanism in bacteria, yeast and mammals as it destroys the intracellular niche for pathogen replication. However, excessive and uncontrolled cell death also contributes to immunopathology in several chronic inflammatory diseases, including arthritis. In this review, we discuss recent findings where pyroptosis contributes to tissue damage and inflammation with a main focus on injury-induced and autoimmune arthritis. We also review novel functions and regulatory mechanisms of the pyroptotic executors gasdermins. Finally, we discuss possible models of how pyroptosis may contribute to the cross-talk between fibroblast and macrophages, and also how this cross-talk may regulate inflammation by modulating inflammasome activation and pyroptosis induction.

Regulatory network-based model to simulate the biochemical regulation of chondrocytes in healthy and osteoarthritic environments

In osteoarthritis (OA), chondrocyte metabolism dysregulation increases relative catabolic activity, which leads to cartilage degradation. To enable the semiquantitative interpretation of the intricate mechanisms of OA progression, we propose a network-based model at the chondrocyte level that incorporates the complex ways in which inflammatory factors affect structural protein and protease expression and nociceptive signals. Understanding such interactions will leverage the identification of new potential therapeutic targets that could improve current pharmacological treatments. Our computational model arises from a combination of knowledge-based and data-driven approaches that includes in-depth analyses of evidence reported in the specialized literature and targeted network enrichment. We achieved a mechanistic network of molecular interactions that represent both biosynthetic, inflammatory and degradative chondrocyte activity. The network is calibrated against experimental data through a genetic algorithm, and 81% of the responses tested have a normalized root squared error lower than 0.15. The model captures chondrocyte-reported behaviors with 95% accuracy, and it correctly predicts the main outcomes of OA treatment based on blood-derived biologics. The proposed methodology allows us to model an optimal regulatory network that controls chondrocyte metabolism based on measurable soluble molecules. Further research should target the incorporation of mechanical signals.

Liraglutide, a glucagon-like peptide 1 receptor agonist, exerts analgesic, anti-inflammatory and anti-degradative actions in osteoarthritis

Osteoarthritis (OA) is a common disabling disease worldwide, with no effective and safe disease-modifying drugs (DMOAD) in the market. However, studies suggest that drugs, such as liraglutide, which possess strong potential in decreasing low-grade systemic inflammation may be effective in treating OA. Therefore, the aim of this study was to examine the anti-inflammatory, analgesic, and anti-degradative effects in OA using in vitro and in vivo experiments. The results showed that intra-articular injection of liraglutide alleviated pain-related behavior in in vivo sodium monoiodoacetate OA mouse model, which was probably driven by the GLP-1R-mediated anti-inflammatory activity of liraglutide. Moreover, liraglutide treatment significantly decreased IL-6, PGE₂ and nitric oxide secretion, and the expression of inflammatory genes in vitro in chondrocytes and macrophages in a dose-dependent manner. Additionally, liraglutide shifted polarized macrophage phenotype in vitro from the pro-inflammatory M1 phenotype to the M2 anti-inflammatory phenotype. Furthermore, liraglutide exerted anti-catabolic activity by significantly decreasing the activities of metalloproteinases and aggrecanases, a family of catabolic enzymes involved in cartilage breakdown in vitro. Overall, the findings of this study showed that liraglutide ameliorated OA-associated pain, possess anti-inflammatory and analgesic properties, and could constitute a novel therapeutic candidate for OA treatment.

Adiponectin, May Be a Potential Protective Factor for Obesity-Related Osteoarthritis

Osteoarthritis (OA) is the most common joint disease in elderly individuals and seriously affects quality of life. OA has often been thought to be caused by body weight load, but studies have increasingly shown that OA is an inflammation-mediated metabolic disease. The current existing evidence suggests that OA is associated with obesity-related chronic inflammation as well as abnormal lipid metabolism in obesity, such as fatty acids (FA) and triglycerides. Adiponectin, a cytokine secreted by adipose tissue, can affect the progression of OA by regulating obesity-related inflammatory factors. However, the specific molecular mechanism has not been fully elucidated. According to previous research, adiponectin can promote the metabolism of FA and triglycerides, which indicates that it is a potential protective factor for OA through many mechanisms. This article aims to review the mechanisms of chronic inflammation, FA and triglycerides in OA, as well as the potential mechanisms of adiponectin in regulating chronic inflammation and promoting FA and triglyceride metabolism. Therefore, adiponectin may have a protective effect on obesity-related OA, which could provide new insight into adiponectin and the related mechanisms in OA.

Ribosome dysfunction in osteoarthritis

PURPOSE OF REVIEW

Translation of genetic information encoded within mRNA molecules by ribosomes into proteins is a key part of the central dogma of molecular biology. Despite the central position of the ribosome in the translation of proteins, and considering the major proteomic changes that occur in the joint during osteoarthritis development and progression, the ribosome has received very limited attention as driver of osteoarthritis pathogenesis.

RECENT FINDINGS

We provide an overview of the limited literature regarding this developing topic for the osteoarthritis field. Recent key findings that connect ribosome biogenesis and activity with osteoarthritis include: ribosomal RNA transcription, processing and maturation, ribosomal protein expression, protein translation capacity and preferential translation.

SUMMARY

The ribosome as the central cellular protein synthesis hub is largely neglected in osteoarthritis research. Findings included in this review reveal that in osteoarthritis, ribosome aberrations have been found from early-stage ribosome biogenesis, through ribosome build-up and maturation, up to preferential translation. Classically, osteoarthritis has been explained as an imbalance between joint tissue anabolism and catabolism. We postulate that osteoarthritis can be interpreted as an acquired ribosomopathy. This hypothesis fine-tunes the dogmatic anabolism/katabolism point-of-view, and may provide novel molecular opportunities for the development of osteoarthritis disease-modifying treatments.

Cell-laden injectable microgels: Current status and future prospects for cartilage regeneration

Injectable hydrogels have been employed extensively as versatile materials for cartilage regeneration due to their excellent biocompatibility, tunable structure, and ability to accommodate bioactive factors, as well as their ability to be locally delivered via minimally invasive injection to fill irregular defects. More recently, in vitro and in vivo studies have revealed that processing these materials to produce cell-laden microgels can enhance cell-cell and cell-matrix interactions and boost nutrient and metabolite exchange. Moreover, these studies have demonstrated gene expression profiles and matrix regeneration that are superior compared to conventional injectable bulk hydrogels. As cell-laden microgels and their application in cartilage repair are moving closer to clinical translation, this review aims to present an overview of the recent developments in this field. Here we focus on the currently used biomaterials and crosslinking strategies, the innovative fabrication techniques being used for the production of microgels, the cell sources used, the signals used for induction of chondrogenic differentiation and the resultant biological responses, and the ability to create three-dimensional, functional cartilage tissues. In addition, this review also covers the current clinical approaches for repairing cartilage as well as specific challenges faced when attempting the regeneration of damaged cartilage tissue. New findings related to the macroporous nature of the structures formed by the assembled microgel building blocks and the novel use of microgels in 3D printing for cartilage tissue engineering are also highlighted. Finally, we outline the challenges and future opportunities for employing cell-laden microgels in clinical applications.

Adipose-Derived Mesenchymal Stem Cells-Conditioned Medium Modulates the Expression of Inflammation Induced Bone Morphogenetic Protein-2, -5 and -6 as Well as Compared with Shockwave Therapy on Rat Knee Osteoarthritis

The dose-dependent effects of adipose-derived mesenchymal stem cell-conditioned medium (ADSC-CM) were compared with those of shockwave (SW) therapy in the treatment of early osteoarthritis (OA). Anterior cruciate ligament transaction (ACLT) with medial meniscectomy (MMx) was performed in rats divided into sham, OA, SW, CM1 (intra-articular injection of 100 μL ADSC-CM into knee OA), and CM2 (intra-articular injection of 200 μL ADSC-CM) groups. Cartilage grading, grading of synovium changes, and specific molecular analysis by immunohistochemistry staining were performed. The OARSI and synovitis scores of CM2 and SW group were significantly decreased compared with those of the OA group (p < 0.05). The inflammatory markers interleukin 1β, terminal deoxynucleotidyl transferase dUTP nick end labeling and matrix metalloproteinase 13 were significantly reduced in the CM2 group compared to those in the SW and CM1 groups (p < 0.001). Cartilage repair markers (type II collagen and SRY-box transcription factor 9, SOX9) expression were significantly higher in the CM2 group than in the other treatment groups (p < 0.001; p < 0.05). Furthermore, inflammation-induced growth factors such as bone morphogenetic protein 2 (BMP2), BMP5, and BMP6 were significantly reduced in the treatment groups, and the CM2 group showed the best results among the treatments (p < 0.05). In conclusion, ADSC-CM and SW ameliorated the expression of inflammatory cytokines and inflammation-induced BMPs to protect the articular cartilage of the OA joint.

Melatonin Maintains Anabolic-Catabolic Equilibrium and Regulates Circadian Rhythm During Osteoarthritis Development in Animal Models: A Systematic Review and Meta-analysis

Background: The driving force behind osteoarthritis (OA) pathogenesis is an anabolic-catabolic (a/c) imbalance. Melatonin (MT) is a key player in maintaining a/c stability and mitigates OA pathogenesis, but mechanisms underlying its effects remain poorly understood.

Objectives: We performed a systematic review analyzing the experimental data that support the clinical applicability of MT in the treatment of OA pathogenesis, placing particular emphasis on the regulation of circadian rhythms and a/c balance.

Methods: Major electronic databases and grey literature were used to identify related original articles. Methodological quality of all selected studies was evaluated using the SYRCLE risk of bias tool. Pooled mean differences (MDs)/standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to estimate the effect size.

Results: Eleven trials were included in this systematic review. Compared with the control group, MT significantly decreased the levels of interleukin-1β (IL-1β; SMD = −5.45; 95% CI [−6.78, −4.12]; p < 0.00001, and histological grading scale (SMD = −3.46; 95% CI, [−5.24, −1.68]; p < 0.0001). MT significantly increased the transforming growth factor-β1 (TGF-β1; SMD = 1.17; 95% CI [0.31, 2.03]; p < 0.0007). Furthermore, core circadian clock genes Per2 and Cry1 mRNA levels were regulated by MT treatment in OA progression.

Conclusion: MT may maintain a/c balance and regulate circadian rhythms during OA development. MT could be used in as adjunct with other interventions to manage pain and OA severity.

Differentiating Psoriatic Arthritis from Osteoarthritis and Rheumatoid Arthritis: A Narrative Review and Guide for Advanced Practice Providers

Psoriatic arthritis (PsA) is a chronic inflammatory disease that affects multiple organ systems and is characterized by skin and joint manifestations. PsA is frequently undiagnosed and/or misdiagnosed, especially because of the similarities in clinical presentation shared with other arthritic diseases, including rheumatoid arthritis (RA) and osteoarthritis (OA). An accurate and timely diagnosis of PsA is crucial to prevent delays in optimal treatment, which can lead to irreversible joint damage and increased functional disability. Patients are usually seen by a number of different healthcare providers on their path to a diagnosis of PsA, including advanced practice providers (APPs). This review provides a comprehensive overview of the characteristic features that can be used to facilitate the differentiation of PsA from RA and OA. Detailed information on clinical manifestations, biomarkers, radiologic features, and therapeutic recommendations for PsA included here can be applied in routine clinical settings to provide APPs with the confidence and knowledge to recognize and refer patients more accurately to rheumatologists for management of patients with PsA.

Diagnostic and Therapeutic Role of Extracellular Vesicles in Articular Cartilage Lesions and Degenerative Joint Diseases

Two leading contributors to the global disability are cartilage lesions and degenerative joint diseases, which are characterized by the progressive cartilage destruction. Current clinical treatments often fail due to variable outcomes and an unsatisfactory long-term repair. Cell-based therapies were once considered as an effective solution because of their anti-inflammatory and immunosuppression characteristics as well as their differentiation capacity to regenerate the damaged tissue. However, stem cell-based therapies have inherent limitations, such as a high tumorigenicity risk, a low retention, and an engraftment rate, as well as strict regulatory requirements, which result in an underwhelming therapeutic effect. Therefore, the non-stem cell-based therapy has gained its popularity in recent years. Extracellular vesicles (EVs), in particular, like the paracrine factors secreted by stem cells, have been proven to play a role in mediating the biological functions of target cells, and can achieve the therapeutic effect similar to stem cells in cartilage tissue engineering. Therefore, a comprehensive review of the therapeutic role of EVs in cartilage lesions and degenerative joint diseases can be discussed both in terms of time and favorability. In this review, we summarized the physiological environment of a joint and its pathological alteration after trauma and consequent changes in EVs, which are lacking in the current literature studies. In addition, we covered the potential working mechanism of EVs in the repair of the cartilage and the joint and also discussed the potential therapeutic applications of EVs in future clinical use.

Blocking TNFα attenuates progressive cartilage matrix degradation in inflammatory arthritis

Because damage to hyaline cartilage is irreversible, relieving progressive cartilage destruction is an important therapeutic approach for inflammatory arthritis. In the present study, human hyaline chondrocytes were isolated from total knee replacements of 15 patients with osteoarthritis (OA) and three with rheumatoid arthritis (RA). Synovial fluid of OA (n=25) and RA (n=34) were collected to measure tumor necrosis factor α (TNFα) using ELISA. Consistent with previous studies, the synovial fluid exhibited high TNFα levels and hyaline cartilage was severely destroyed in patients with RA. TNFα-treated chondrocytes were used as model for inflammatory arthritis. TNFα did not influence proliferation or extracellular matrix expression in chondrocytes, but induced matrix metalloproteinase (MMP)1, 3 and 13 expression levels in chondrocytes, which was accompanied by activation of nuclear factor-κB signaling. During chondrogenic differentiation, TNFα attenuated mRNA expression levels of anabolic factors (collagen type 2 and aggrecan) and enhanced mRNA expression of catabolic factors (MMP1, MMP3 and MMP13) in chondrocytes. Moreover, anti-TNFα agents (Golimumab) inhibited the TNFα-induced metabolic shift in chondrocytes and chondrogenic differentiation. The present study revealed a mechanism by which TNFα may induce metabolic shift in chondrocytes, leading to progressive chondrocyte destruction.

Oral Administration of Lactobacillus rhamnosus Ameliorates the Progression of Osteoarthritis by Inhibiting Joint Pain and Inflammation

Osteoarthritis (OA) is the most common form of arthritis and age-related degenerative joint disorder, which adversely affects quality of life and causes disability. However, the pathogenesis of OA remains unclear. This study was performed to examine the effects of Lactobacillus rhamnosus in OA progression. OA was induced in 6-week-old male Wistar rats by monosodium iodoacetate (MIA) injection, and the effects of oral administration of L. rhamnosus were examined in this OA rat model. Pain severity, cartilage destruction, and inflammation were measured in MIA-induced OA rats. The small intestines were isolated from OA rats, and the intestinal structure and inflammation were measured. Protein expression in the dorsal root ganglion was analyzed by immunohistochemistry. The effects of L. rhamnosus on mRNA and protein expression in chondrocytes stimulated with interleukin (IL)-1β and lipopolysaccharide (LPS) were analyzed by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Pain severity was decreased in L. rhamnosus-treated MIA-induced OA rats. The levels of expression of MCP-1, a potential inflammatory cytokine, and its receptor, CCR2, were decreased, and GABA and PPAR-γ expression were increased in L. rhamnosus-treated OA rats. The inflammation, as determined by IL-1β, and cartilage destruction, as determined by MMP3, were also significantly decreased by L. rhamnosus in OA rats. Additionally, intestinal damage and inflammation were improved by L. rhamnosus. In human OA chondrocytes, TIMP1, TIMP3, SOX9, and COL2A1 which are tissue inhibitors of MMP, and IL-10, an anti-inflammatory cytokine, were increased by L. rhamnosus. L. rhamnosus treatment led to decreased pain severity and cartilage destruction in a rat model of OA. Intestinal damage and inflammation were also decreased by L. rhamnosus treatment. Our findings suggested the therapeutic potential of L. rhamnosus in OA.

Metformin Attenuates Monosodium-Iodoacetate-Induced Osteoarthritis via Regulation of Pain Mediators and the Autophagy-Lysosomal Pathway

Osteoarthritis (OA) is the most common degenerative arthritis associated with pain and cartilage destruction in the elderly; it is known to be involved in inflammation as well. A drug called celecoxib is commonly used in patients with osteoarthritis to control pain. Metformin is used to treat type 2 diabetes but also exhibits regulation of the autophagy pathway. The purpose of this study is to investigate whether metformin can treat monosodium iodoacetate (MIA)-induced OA in rats. Metformin was administered orally every day to rats with OA. Paw-withdrawal latency and threshold were used to assess pain severity. Cartilage damage and pain mediators in dorsal root ganglia were evaluated by histological analysis and a scoring system. Relative mRNA expression was measured by real-time PCR. Metformin reduced the progression of experimental OA and showed both antinociceptive properties and cartilage protection. The combined administration of metformin and celecoxib controlled cartilage damage more effectively than metformin alone. In chondrocytes from OA patients, metformin reduced catabolic factor gene expression and inflammatory cell death factor expression, increased LC3Ⅱb, p62, and LAMP1 expression, and induced an autophagy-lysosome fusion phenotype. We investigated if metformin treatment reduces cartilage damage and inflammatory cell death of chondrocytes. The results suggest the potential for the therapeutic use of metformin in OA patients based on its ability to suppress pain and protect cartilage.

Effects of Exercise Combined with Undenatured Type II Collagen on Endurance Capacity, Antioxidant Status, Muscle Lipogenic Genes and E3 Ubiquitin Ligases in Rats

The current study aimed to investigate the effect of exercise combined with undenatured type II collagen (UCII) administration on endurance capacity, lipid metabolism, inflammation, and antioxidant status in rats. Twenty-one male Wistar albino rats were divided into three groups as follows: (1) Sedentary control, (2) Exercise (E), (3) Exercise + UCII (4 mg/kg BW/day; E + UCII). The findings showed that the exhaustive running time in the UCII group was significantly prolonged compared to that of the non-supplemented group (p < 0.001). When compared to the control group, total serum cholesterol (TC, p < 0.05) and triglyceride (TG, p < 0.05) levels decreased, while creatinine kinase (CK) levels increased in the E group (p < 0.001). Serum creatinine kinase levels were reduced in the E + UCII group compared to the E group (p < 0.01). Serum lactate, myoglobin (p < 0.01), and osteocalcin levels (p < 0.01) increased significantly in exercised rats compared to sedentary control rats, while serum lactate (p < 0.01) and myoglobin (p < 0.0001) levels decreased in the E + UCII group compared to control. Additionally, UCII supplementation caused significant increases in antioxidant enzyme activities [SOD (p < 0.01) and GSH-Px (p < 0.05)] and decreases in malondialdehyde (MDA) and tumor necrosis factor (TNF-α) levels (p < 0.001). Muscle lipogenic protein (SREBP-1c, ACLY, LXR, and FAS) levels were lower in the E + UCII group than in other groups. In addition, UCII supplementation decreased muscle MAFbx, MuRF-1, myostatin and increased MyoD levels in exercised rats. Moreover, the E + UCII group had lower muscle inflammatory markers [TNF-α (p < 0.0001) and IL-1β (p < 0.01)] than the control group. These results suggest exercise combined with UCII (4 mg/kg BW/day) modulates lipid, muscle, and antioxidant status in rats.

Autologous protein solution as selective treatment for advanced patellofemoral osteoarthritis in the middle-aged female patient: 54% response rate at 1 year follow-up

PURPOSE

The study wanted to investigate the benefit, durability and safety of autologous protein solution (APS) injection(s) in a middle-aged female-only cohort suffering predominantly from patellofemoral osteoarthritis.

METHODS

Fifty females (aged 50.4 ± 6.5) with mainly moderate-severe (86%) patellofemoral cartilage wear (PFCW) were treated with a unilateral intra-articular APS injection. The KOOS, NRS, Kujala, UCLA and EQ-5D were assessed at baseline and 1, 3, 6, and 12 months post-injection. Therapeutic response rate (TRR) was based on KOOS pain improvement > 10 points. Absolute improvement for, respectively, therapy responders and non-responders was determined. Second APS injection was administered if improvement was deemed insufficient by the patient after 3 months.

RESULTS

The TRR remained stable averaging to 53.7% at final follow-up with subjects improving overall from 40.3 ± 18.7 to 57.3 ± 24.8 points on KOOS pain (p = 0.0002) and from 48.4 ± 13.0 to 56.3 ± 18.1 points on Kujala (p = 0.0203) at 12 months. Significant improvement was observed for the other KOOS subscales and NRS at each follow-up. In absolute values, APS responders improved with 30.5 ± 11.4 points on KOOS pain at 12 months. In contrast, non-responders deteriorated with 5.9 ± 8.9 points relative to baseline. A second APS injection was administered in 28 subjects. Patients with definite synovitis improved more on KOOS symptoms (p = 0.017) and KOOS ADL (p = 0.037) at 12 months compared to non-synovitis subjects. Mild-moderate arthralgia (46%) and effusion (29%) were commonly observed during the first month post-injection.

CONCLUSION

This study evidenced a 54% response rate at 12 months to a single or second APS injection in a middle-aged female population with advanced patellofemoral cartilage wear. Moderate temporary flares can be expected without affecting clinical outcomes. Second APS injection has low efficacy in initially poor responding patients after 3 months. Major synovitis on baseline MRI appeared to be a beneficial prognosticator for pain relief and functional improvement after APS.

LEVEL OF EVIDENCE

IV.

Silymarin modulates catabolic cytokine expression through Sirt1 and SOX9 in human articular chondrocytes

Background

Silymarin (SMN), a polyphenolic flavonoid, is involved in multiple bioactive functions including anti-inflammation. Pretreatment with SMN demonstrated chondroprotection against tumour necrosis factor-alpha (TNF-α) stimulation in a chondrocyte cell line. However, pre- and posttreatment with phytochemicals have varying effects on osteoarthritis (OA) chondrocytes, and the therapeutic potential of SMN after catabolic cytokine stimulation is not fully elucidated.

Methods

The cytotoxicity of SMN (12.5, 25, 50 and 100 μM) was evaluated in human primary chondrocytes. The chondrocytes were supplemented with SMN (25 and 50 μM) after interleukin-1beta (IL-1β) stimulation. The mRNA expression and protein production of catabolic/anabolic cytokines as well as extracellular matrix (ECM) components were evaluated.

Results

High-dose SMN (100 μM) impaired the mitochondrial activity in chondrocytes, and 50 μM SMN further caused cell death in IL-1β-stimulated cells. The addition of 25 μM SMN ameliorated cell senescence; downregulated the catabolic genes of inducible nitric oxide synthase, IL-1β, TNF-α, matrix metalloproteinase-3 (MMP-3), MMP-9 and MMP-13; upregulated the anabolic genes of tissue inhibitor of metalloproteinase-1 (TIMP-1) and collagen type II alpha 1; and restored the expression of chondrogenic phenotype genes SOX9 and sirtuin-1 (Sirt1). In addition, the production of IL-1β, MMP-3 and MMP-9 decreased with an increase in TIMP-1 secretion. However, the mRNA levels of IL-6, IL-8 and IL-10 and protein production remained high. The addition of nicotinamide, a Sirt1 inhibitor, downregulated SOX9 and attenuated the therapeutic effects of SMN on IL-1β-stimulated chondrocytes.

Conclusion

SMN regulates the chondrocyte phenotype through Sirt1 and SOX9 to improve ECM homeostasis and may serve as a complementary therapy for early-stage knee OA.

The P2X7 Receptor in Osteoarthritis

Osteoarthritis (OA) is the most common joint disease. With the increasing aging population, the associated socio-economic costs are also increasing. Analgesia and surgery are the primary treatment options in late-stage OA, with drug treatment only possible in early prevention to improve patients' quality of life. The most important structural component of the joint is cartilage, consisting solely of chondrocytes. Instability in chondrocyte balance results in phenotypic changes and cell death. Therefore, cartilage degradation is a direct consequence of chondrocyte imbalance, resulting in the degradation of the extracellular matrix and the release of pro-inflammatory factors. These factors affect the occurrence and development of OA. The P2X7 receptor (P2X7R) belongs to the purinergic receptor family and is a non-selective cation channel gated by adenosine triphosphate. It mediates Na⁺, Ca²⁺ influx, and K⁺ efflux, participates in several inflammatory reactions, and plays an important role in the different mechanisms of cell death. However, the relationship between P2X7R-mediated cell death and the progression of OA requires investigation. In this review, we correlate potential links between P2X7R, cartilage degradation, and inflammatory factor release in OA. We specifically focus on inflammation, apoptosis, pyroptosis, and autophagy. Lastly, we discuss the therapeutic potential of P2X7R as a potential drug target for OA.

Morroniside attenuates apoptosis and pyroptosis of chondrocytes and ameliorates osteoarthritic development by inhibiting NF-κB signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Corni Fructus (CF), the red fruit of Cornus officinalis Siebold & Zucc, has been used both as food and medicinal herb in traditional Chinese medicine (TCM). Our previous studies showed that Yougui pills and Bushenhuoxue formula, both TCM prescriptions containing Corni Fructus (CF), have protective effects on osteoarthritis (OA). However, the underlying detailed components in both TCM prescriptions that play therapeutic roles have not been fully defined. Morroniside is a major iridoid glycoside and one of the quality control metrics of CF, but the effects of morroniside on OA remain largely elusive.

AIM OF THE STUDY

The study aims to assess the therapeutic effects of morroniside on cartilage degeneration using a mouse model of OA.

MATERIAL AND METHODS

8-week-old male C57BL/6J mice were randomly divided into 4 groups: Sham, destabilization of the medial meniscus (DMM)-treated with vehicle, DMM-treated with low dose morroniside and DMM-treated with high dose morroniside. Histological staining, immunostaining, and TUNEL staining were conducted to detect changes in tissue morphology, expression of key molecules in chondrocytes, and chondrocyte apoptosis, respectively. Osteophyte formation, meniscus calcification, and subchondral sclerosis were quantitated using micro-CT. The expression of chondrocyte markers was also analyzed by Western blot in primary chondrocytes derived from mice treated with morroniside.

RESULTS

Morroniside attenuated the progression of OA in mice, resulting in substantially reduced osteophyte formation and subchondral sclerosis and lower OARSI scores. Specifically, morroniside significantly promoted cartilage matrix synthesis by increasing collagen type II expression and suppressing chondrocyte pyroptosis. Morroniside administration led to inhibition of matrix metalloproteinase-13 (MMP13), Caspase-1 and nod-like receptor protein-3 (NLRP3) expression in DMM mice and IL-1β-stimulated chondrocytes. In addition, morroniside attenuated the progression of OA by enhancing chondrocyte proliferation and inhibiting chondrocyte apoptosis. Morroniside also attenuated the progression of OA by inhibiting nuclear factor-κB (NF-κB) signaling.

CONCLUSION

Morroniside was protective against cartilage matrix degradation and reduced DMM-induced chondrocyte pyroptosis and apoptosis by the inhibition of NF-κB signaling.

Overview of MMP-13 as a Promising Target for the Treatment of Osteoarthritis

Osteoarthritis (OA) is a common degenerative disease characterized by the destruction of articular cartilage and chronic inflammation of surrounding tissues. Matrix metalloproteinase-13 (MMP-13) is the primary MMP involved in cartilage degradation through its particular ability to cleave type II collagen. Hence, it is an attractive target for the treatment of OA. However, the detailed molecular mechanisms of OA initiation and progression remain elusive, and, currently, there are no interventions available to restore degraded cartilage. This review fully illustrates the involvement of MMP-13 in the initiation and progression of OA through the regulation of MMP-13 activity at the molecular and epigenetic levels, as well as the strategies that have been employed against MMP-13. The aim of this review is to identify MMP-13 as an attractive target for inhibitor development in the treatment of OA.

Current Models for Development of Disease-Modifying Osteoarthritis Drugs

Osteoarthritis (OA) is a painful and disabling disease that affects millions of people worldwide. Symptom-alleviating treatments exist, although none with long-term efficacy. Furthermore, there are currently no disease-modifying OA drugs (DMOADs) with demonstrated efficacy in OA patients, which is, in part, attributed to a lack of full understanding of the pathogenesis of OA. The inability to translate findings from basic research to clinical applications also highlights the deficiencies in the available OA models at simulating the clinically relevant pathologies and responses to treatments in humans. In this review, the current status in the development of DMOADs will be first presented, with special attention to those in Phase II-IV clinical trials. Next, current in vitro, ex vivo, and in vivo OA models are summarized and the respective advantages and disadvantages of each are highlighted. Of note, the development and application of microphysiological or tissue-on-a-chip systems for modeling OA in humans are presented and the issues that need to be addressed in the future are discussed. Microphysiological systems should be given serious consideration for their inclusion in the DMOAD development pipeline, both for their ability to predict drug safety and efficacy in human clinical trials at present, as well as for their potential to serve as a test platform for personalized medicine. Impact statement At present, no disease-modifying osteoarthritis (OA) drugs (DMOADs) have been approved for widespread clinical use by regulatory bodies. The failure of developing effective DMOADs is likely owing to multiple factors, not the least of which are the intrinsic differences between the intact human knee joint and the preclinical models. This work summarizes the current OA models for the development of DMOADs, discusses the advantages/disadvantages of each, and then proposes future model development to aid in the discovery of effective and personalized DMOADs. The review also highlights the microphysiological systems, which are emerging as a new platform for drug development.

FoxO1 is a crucial mediator of TGF-β/TAK1 signaling and protects against osteoarthritis by maintaining articular cartilage homeostasis

Transforming growth factor-β (TGF-β) signaling is a critical regulator for articular cartilage tissue maintenance and chondrocyte homeostasis. Nonetheless, the regulatory networks and downstream signaling pathways that govern the chondroprotective function of TGF-β in the context of osteoarthritis (OA) are not fully defined. Recent studies reveal that mice with postnatal deletion of triple forkhead box class Os (FoxOs) (1, 3, and 4) spontaneously develop OA-like pathologies. The OA phenotype largely recapitulates that observed in mice with loss of TGF-βR2. In the present study, we investigated the role of FoxOs as downstream mediators of TGF-β signaling and define their role in articular cartilage homeostasis. Among the three FoxOs (1, 3, and 4), TGF-β signaling exclusively regulates FoxO1 in a TGF-β activated kinase 1 (TAK1)-dependent manner. Furthermore, FoxO1 was genetically ablated in mice in a tissue-specific manner in articular cartilage or overexpressed in adult cartilage immediately followed by meniscal/ligament injury (MLI). Histological and microcomputed tomography (micro-CT) analyses demonstrated that loss of FoxO1 postnatally in articular cartilage leads to OA-like pathologies, and gain of FoxO1 in adult cartilage has both preventative and therapeutic effects on surgically induced OA. Mechanistically, FoxO1 was found to maintain articular chondrocyte homeostasis through induction of anabolic and autophagy-related gene expressions. Importantly, overexpression of FoxO1 markedly rescued the OA phenotypes caused by deficiency in TGF-β signaling in chondrocytes. Our study identifies that TGF-β/TAK1-FoxO1 is a key signaling cascade in regulation of articular cartilage autophagy and homeostasis and is a potentially important therapeutic target for OA-like joint diseases.

Pyroptosis Plays a Role in Osteoarthritis

Recent studies have revealed novel forms of cell death beyond the canonical types of cellular apoptosis and necrosis, and these novel forms of cell death are induced by extreme microenvironmental factors. Pyroptosis, a type of regulated cell death, occurs when pattern recognition receptors (PRRs) induce the activation of cysteine-aspartic protease 1 (caspase-1) or caspase-11, which can trigger the release of the pyrogenic cytokines interleukin-1β (IL-1β) and IL-18. Osteoarthritis (OA), the most common joint disease worldwide, is characterized by low-grade inflammation and increased levels of cytokines, including IL-1β and IL-18. Additionally, some damaged chondrocytes associated with OA exhibit morphological changes consistent with pyroptosis, suggesting that this form of regulated cell death may contribute significantly to the pathology of OA. This review summarizes the molecular mechanisms of pyroptosis and shows the critical role of NLRP3 (NLR family, pyrin domain containing 3; NLR refers to "nucleotide-binding domain, leucine-rich repeat") inflammasomes. We also provide evidence describing potential role of pyroptosis in OA, including the relationship with OA risk factors and the contribution to cartilage degradation, synovitis and OA pain.

Mass Spectrometry Imaging as a Potential Tool to Investigate Human Osteoarthritis at the Tissue Level

Osteoarthritis (OA) is the most common degenerative joint disease, predicted to increase in incidence year by year due to an ageing population. Due to the biological complexity of the disease, OA remains highly heterogeneous. Although much work has been undertaken in the past few years, underlying molecular mechanisms leading to joint tissue structural deterioration are not fully understood, with only few validated markers for disease diagnosis and progression being available. Discovery and quantitation of various OA-specific biomarkers is still largely focused on the bodily fluids which does not appear to be reliable and sensitive enough. However, with the advancement of spatial proteomic techniques, several novel peptides and proteins, as well as N-glycans, can be identified and localised in a reliable and sensitive manner. To summarise the important findings from OA biomarker studies, papers published between 2000 and 2020 were searched via Google Scholar and PubMed. Medical subject heading (MeSH) terms ‘osteoarthritis’, ‘biomarker’, ‘synovial fluid’, ‘serum’, ‘urine’, ’matrix-assisted laser desorption/ionisation’, ‘mass spectrometry imaging’, ‘proteomic’, ‘glycomic’, ‘cartilage’, ‘synovium’ AND ‘subchondral bone’ were selectively used. The literature search was restricted to full-text original research articles and written only in English. Two main areas were reviewed for OA biomarker studies: (1) an overview of disease-specific markers detected from different types of OA bio-samples, and (2) an up-to-date summary of the tissue-specific OA studies that have utilised matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI). Overall, these OA biomarkers could provide clinicians with information for better the diagnosis, and prognosis of individual patients, and ultimately help facilitate the development of disease-modifying treatments.