MMP13 is a critical target gene during the progression of osteoarthritis

circSLTM knockdown attenuates chondrocyte inflammation, apoptosis and ECM degradation in osteoarthritis by regulating the miR-515-5p/VAPB axis

Osteoarthritis (OA) is a prevalent joint disorder characterized by cartilage degeneration. Circular RNAs (circRNAs) have emerged as pivotal players in OA progression, orchestrating various biological processes such as proliferation, apoptosis, inflammation, and extracellular matrix (ECM) reorganization. Among these circRNAs, circSLTM exhibits aberrant expression in OA, yet its precise regulatory mechanism remains elusive. This study aimed to elucidate the regulatory mechanisms of circSLTM in OA pathogenesis, with a focus on its role as a competing endogenous RNA (ceRNA). Human cartilage tissues were procured from both OA patients and non-OA individuals, while human chondrocyte cells were subjected to lipopolysaccharide (LPS) treatment to mimic OA-like conditions. Our findings revealed upregulation of circSLTM in OA patients and LPS-treated chondrocytes. Loss-of-function assays were conducted, demonstrating that silencing circSLTM via shRNAs mitigated LPS-induced effects on chondrocytes, as evidenced by enhanced proliferation, reduced apoptosis, and inflammatory factors, and altered expression of extracellular matrix proteins. Further exploration into the regulatory mechanism of circSLTM unveiled its interaction with microRNA-515-5p (miR-515-5p) to modulate vesicle-associated membrane protein (VAPB) expression in chondrocytes. VAPB, also upregulated in OA, was positively regulated by circSLTM. Rescue assays corroborated that VAPB overexpression reinstated the protective effects of circSLTM knockdown on LPS-treated chondrocytes. Moreover, concurrent knockdown of both circSLTM and VAPB demonstrated synergistic protection against LPS-induced chondrocyte injury. Additionally, we delineated that LPS triggered the activation of the NF-κB pathway in chondrocytes, which was counteracted by circSLTM silencing. To assess the effects of circSLTM on OA in vivo, anterior cruciate ligament transection (ACLT) mouse models were established, revealing that circSLTM deficiency ameliorated cartilage defects in vivo. In conclusion, circSLTM exacerbates osteoarthritis progression by orchestrating the miR-515-5p/VAPB axis and activating the NF-κB pathway, providing novel insights for targeted therapy in OA management.

Unraveling the Mechanisms of Hypertrophy-Induced Matrix Mineralization and Modifications in Articular Chondrocytes

Chondrocyte hypertrophic differentiation is a main event leading to articular cartilage degradation in osteoarthritis. It is associated with matrix remodeling and mineralization, the dynamics of which is not well characterized during chondrocyte hypertrophic differentiation in articular cartilage. Based on an in vitro model of progressive differentiation of immature murine articular chondrocytes (iMACs) into prehypertrophic (Prehyp) and hypertrophic (Hyp) chondrocytes, we performed kinetics of chondrocyte differentiation from Prehyp to Hyp to follow matrix mineralization and remodeling by immunofluorescence, biochemical, molecular, and physicochemical approaches, including atomic force microscopy, scanning electron microscopy associated with energy-dispersive X-ray spectroscopy (SEM-EDS), attenuated total reflection infrared analyses, and X-ray diffraction. Chondrocyte apoptosis was determined by TUNEL assay. The results show the formation of a mineral phase 7 days after Hyp induction, which spreads within the matrices to form poorly crystalline carbonate-substituted hydroxyapatite after 14 days, then the proportions of crystalline relative to amorphous content increases over time. Hyp differentiation also induced a matrix turnover that occurs over the first 7 days, characterized by a decrease in type II collagen and aggrecan and the concomitant appearance of type X collagen. This is accompanied by an increase in the enzymatic activity of MMP-13, the main collagenase in cartilage. The number of apoptotic chondrocytes slightly increased with Hyp differentiation and SEM-EDS analyses detected phosphorus-rich structures that could correspond to apoptotic bodies. Our findings highlight the mechanisms of matrix remodeling events leading to the mineralization of articular cartilage that may occur in osteoarthritis.

Teaming up to overcome challenges toward translation of new therapeutics for osteoarthritis

As a leading global cause of musculoskeletal-related disability, osteoarthritis (OA) represents a public health urgency. Understanding of disease pathogenesis has advanced substantially in the past decade, yet no disease-modifying therapeutics have advanced to the clinic. To address this challenge, the CARE-AP (Cartilage Repair strategies to alleviate Arthritis Pain) collaborative research team was convened to bring together relevant multidisciplinary expertise and perspectives from across the VA research community nationwide. The first CARE-AP Annual Research Symposium took place (virtually) in February 2022 with roughly 90 participants. A number of innovative and therapeutic strategies were discussed, including siRNA approaches coupled with novel nanoparticle-based delivery systems, cellular engineering approaches to develop reparative cells that can probe the joint environment and respond to disease-specific cues, and novel biofabrication techniques to improve tissue engineering and effect "biological joint replacement." In addition, challenges and advances in rehabilitation approaches, imaging outcomes, and clinical studies were presented, which were integrated into a framework of recommendations for running "preclinical trials" to improve successful clinical translation.

Injectable hydrogel encapsulating siMMP13 with anti-ROS and anti-apoptotic functions for osteoarthritis treatment

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease characterized by the progressive degeneration of articular cartilage, leading to pain, stiffness, and loss of joint function. The pathogenesis of OA involves multiple factors, including increased intracellular reactive oxygen species (ROS), enhanced chondrocyte apoptosis, and disturbances in cartilage matrix metabolism. These processes contribute to the breakdown of the extracellular matrix (ECM) and the loss of cartilage integrity, ultimately resulting in joint damage and dysfunction. RNA interference (RNAi) therapy has emerged as a promising approach for the treatment of various diseases, including hATTR and acute hepatic porphyria. By harnessing the natural cellular machinery for gene silencing, RNAi allows for the specific inhibition of target genes involved in disease pathogenesis. In the context of OA, targeting key molecules such as matrix metalloproteinase-13 (MMP13), which plays a critical role in cartilage degradation, holds great therapeutic potential.

RESULTS

In this study, we developed an innovative therapeutic approach for OA using a combination of liposome-encapsulated siMMP13 and NG-Monomethyl-L-arginine Acetate (L-NMMA) to form an injectable hydrogel. The hydrogel served as a delivery vehicle for the siMMP13, allowing for sustained release and targeted delivery to the affected joint. Experiments conducted on destabilization of the medial meniscus (DMM) model mice demonstrated the therapeutic efficacy of this composite hydrogel. Treatment with the hydrogel significantly inhibited the degradation of cartilage matrix, as evidenced by histological analysis showing preserved cartilage structure and reduced loss of proteoglycans. Moreover, the hydrogel effectively suppressed intracellular ROS accumulation in chondrocytes, indicating its anti-oxidative properties. Furthermore, it attenuated chondrocyte apoptosis, as demonstrated by decreased levels of apoptotic markers.

CONCLUSION

In summary, the injectable hydrogel containing siMMP13, endowed with anti-ROS and anti-apoptotic properties, may represent an effective therapeutic strategy for osteoarthritis in the future.

Prospects of Disease-Modifying Osteoarthritis Drugs

Osteoarthritis (OA) causes a massive disease burden with a global prevalence of nearly 23% in 2020 and an unmet need for adequate treatment, given a lack of disease-modifying drugs (DMOADs). The author reviews the prospects of active DMOAD candidates in the phase 2/3 clinical trials of drug development pipeline based on key OA pathogenetic mechanisms directed to inflammation-driven, bone-driven, and cartilage-driven endotypes. The challenges and possible research opportunities are stated in terms of the formulation of a research question known as the PICO approach: (1) population, (2) interventions, (3) comparison or placebo, and (4) outcomes.

Promoting Articular Cartilage Regeneration through Microenvironmental Regulation

In recent years, as the aging population continues to grow, osteoarthritis (OA) has emerged as a leading cause of disability, with its incidence rising annually. Current treatments of OA include exercise and medications in the early stages and total joint replacement in the late stages. These approaches only relieve pain and reduce inflammation; however, they have significant side effects and high costs. Therefore, there is an urgent need to identify effective treatment methods that can delay the pathological progression of this condition. The changes in the articular cartilage microenvironment, which are complex and diverse, can aggravate the pathological progression into a vicious cycle, inhibiting the repair and regeneration of articular cartilage. Understanding these intricate changes in the microenvironment is crucial for devising effective treatment modalities. By searching relevant research articles and clinical trials in PubMed according to the keywords of articular cartilage, microenvironment, OA, mechanical force, hypoxia, cytokine, and cell senescence. This study first summarizes the factors affecting articular cartilage regeneration, then proposes corresponding treatment strategies, and finally points out the future research direction. We find that regulating the opening of mechanosensitive ion channels, regulating the expression of HIF-1, delivering growth factors, and clearing senescent cells can promote the formation of articular cartilage regeneration microenvironment. This study provides a new idea for the treatment of OA in the future, which can promote the regeneration of articular cartilage through the regulation of the microenvironment so as to achieve the purpose of treating OA.

Magnetic Polysaccharide Mesenchymal Stem Cells Exosomes Delivery Microcarriers for Synergistic Therapy of Osteoarthritis

Osteoarthritis (OA) is a prevalent degenerative disease that afflicts more than 250 million people worldwide, impairing their mobility and quality of life. However, conventional drug therapy is palliative. Exosomes (Exo), although with the potential to fundamentally repair cartilage, face challenges in their efficient enrichment and delivery. In this study, we developed magnetic polysaccharide hydrogel particles as microcarriers for synergistic therapy of OA. The microcarriers were composed of modified natural polysaccharides, hyaluronic acid (HAMA), and chondroitin sulfate (CSMA), and were generated from microfluidic electrospray in combination with a cryogelation process. Magnetic nanoparticles with spiny structures capable of capturing stem cell Exo were encapsulated within the microcarriers together with an anti-inflammatory drug diclofenac sodium (DS). The released DS and Exo from the microcarriers had a synergistic effect in alleviating the OA symptoms and promoting cartilage repair. The in vitro and in vivo results demonstrated the excellent performance of the microcarrier for OA treatment. We believe this work has potential for Exo therapy of OA and other related diseases.

Alendronate treatment rescues the effects of compressive loading of TMJ in osteogenesis imperfecta mice

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue caused by mutations associated with type I collagen, which results in defective extracellular matrix in temporomandibular joint (TMJ) cartilage and subchondral bone. TMJ is a fibrocartilaginous joint expressing type I collagen both in the cartilage and the subchondral bone. In the present study the effects of alendronate and altered loading of the TMJ was analyzed both in male and female OI mice.

MATERIALS AND METHODS

Forty-eight, 10-weeks-old male and female OI mice were divided into 3 groups: (1) Control group: unloaded group, (2) Saline + Loaded: Saline was injected for 2 weeks and then TMJ of mice was loaded for 5 days, (3) alendronate + loaded: alendronate was injected for 2 weeks and then TMJ of mice was loaded for 5 days. Mice in all the groups were euthanized 24-h after the final loading.

RESULTS

Alendronate pretreatment led to significant increase in bone volume and tissue density. Histomorphometrically, alendronate treatment led to increase in mineralization, cartilage thickness and proteoglycan distribution. Increased mineralization paralleled decreased osteoclastic activity. Our immunohistochemistry revealed decreased expression of matrix metallopeptidase 13 and ADAM metallopeptidase with thrombospondin type 1 motif 5.

CONCLUSION

The findings of this research support that alendronate prevented the detrimental effects of loading on the extracellular matrix of the TMJ cartilage and subchondral bone.

CRISPR-GEM: A Novel Machine Learning Model for CRISPR Genetic Target Discovery and Evaluation

CRISPR gene editing strategies are shaping cell therapies through precise and tunable control over gene expression. However, achieving reliable therapeutic effects with improved safety and efficacy requires informed target gene selection. This depends on a thorough understanding of the involvement of target genes in gene regulatory networks (GRNs) that regulate cell phenotype and function. Machine learning models have been previously used for GRN reconstruction using RNA-seq data, but current techniques are limited to single cell types and focus mainly on transcription factors. This restriction overlooks many potential CRISPR target genes, such as those encoding extracellular matrix components, growth factors, and signaling molecules, thus limiting the applicability of these models for CRISPR strategies. To address these limitations, we have developed CRISPR-GEM, a multi-layer perceptron (MLP)-based synthetic GRN constructed to accurately predict the downstream effects of CRISPR gene editing. First, input and output nodes are identified as differentially expressed genes between defined experimental and target cell/tissue types respectively. Then, MLP training learns regulatory relationships in a black-box approach allowing accurate prediction of output gene expression using only input gene expression. Finally, CRISPR-mimetic perturbations are made to each input gene individually and the resulting model predictions are compared to those for the target group to score and assess each input gene as a CRISPR candidate. The top scoring genes provided by CRISPR-GEM therefore best modulate experimental group GRNs to motivate transcriptomic shifts towards a target group phenotype. This machine learning model is the first of its kind for predicting optimal CRISPR target genes and serves as a powerful tool for enhanced CRISPR strategies across a range of cell therapies.

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.

Puerarin modulates proliferation, inflammation and ECM metabolism in human nucleus pulposus mesenchymal stem cells via the lncRNA LINC01535

Background

Intervertebral disc degeneration (IVDD) is a highly prevalent musculoskeletal disorder characterized by progressive destruction of the intervertebral disc, leading to chronic low back pain and disability. Emerging evidence suggests that dysregulation of ferroptosis, a recently discovered form of regulated cell death, participates in IVDD pathogenesis. Puerarin, a natural flavonoid compound from Pueraria lobata, has shown promise in modulating ferroptosis in various diseases.

Methods

Human nucleus pulposus-derived mesenchymal stem cells (NPMSCs) were isolated and identified by flow cytometry. We investigated the effects of puerarin on human NPMSCs and examined the underlying molecular mechanisms.

Results

Puerarin significantly promoted human NPMSC proliferation, as evidenced by the increased cell viability and colony formation ability. Furthermore, puerarin suppressed the expression of cyclooxygenase-2 and the proinflammatory cytokine interleukin-6 in NPMSCs, demonstrating the anti-inflammatory properties of the compound. Notably, puerarin attenuated ECM breakdown by downregulating the ECM-degrading enzymes MMP3, MMP13 and ADAMTS5, and it increased ECM component synthesis, including collagen type II and aggrecan, by NPMSCs. Moreover, puerarin inhibited ferroptosis in NPMSCs by modulating the expression of key ferroptosis-related genes, including ACSL4, PTGS2 and GPX4. Depletion of LINC01535 abolished the effects of puerarin on proliferation, inflammation and ECM metabolism, suggesting a key role of this lncRNA in mediating the effects of puerarin.

Conclusion

Our findings show that puerarin promotes the proliferation of human NPMSCs and ECM synthesis by these cells. Furthermore, puerarin inhibits inflammation and ECM degradation by suppressing ferroptosis via LINC01535. These results provide insights into the molecular mechanisms underlying the therapeutic effects of puerarin in IVDD. Targeting ferroptosis and its regulatory factors, such as LINC01535, may have therapeutic potential for the treatment of IDD and other degenerative disorders of the intervertebral disc. Further studies are needed to uncover the translational potential of puerarin and its downstream targets in preclinical and clinical applications.

On-demand release of a selective MMP-13 blocker from an enzyme-responsive injectable hydrogel protects cartilage from degenerative progression in osteoarthritis

In osteoarthritis (OA), the degradation of cartilage is primarily driven by matrix metalloprotease-13 (MMP-13). Hence, the inhibition of MMP-13 has emerged as an attractive target for OA treatment. Among the various approaches that are being explored for MMP-13 regulation, blocking of the enzyme with specific binding molecules appears to be a more promising strategy for preventing cartilage degeneration. To enhance effectiveness and ensure patient compliance, it is preferable for the binding molecule to exhibit sustained activity when administered directly into the joint. Herein, we present an enzyme-responsive hydrogel that was designed to exhibit on-demand, the sustained release of BI-4394, a potent and highly selective MMP-13 blocker. The stable and compatible hydrogel was prepared using triglycerol monostearate. The efficacy of the hydrogel to prevent cartilage damage was assessed in a rat model of OA induced by anterior cruciate ligament transection (ACLT). The results revealed that in comparison to the rats administrated weekly with intra-articular BI-4394, the hydrogel implanted rats had reduced levels of inflammation and bone erosion. In comparison to untreated control, the cartilage in animals administered with BI-4394/hydrogel exhibited significant levels of collagen-2 and aggrecan along with reduced MMP-13. Overall, this study confirmed the potential of BI-4394 delivery using an enzyme-responsive hydrogel as a promising treatment option to treat the early stages of OA by preventing further cartilage degradation.

Signalling interaction between β-catenin and other signalling molecules during osteoarthritis development

Osteoarthritis (OA) is the most prevalent disorder of synovial joint affecting multiple joints. In the past decade, we have witnessed conceptual switch of OA pathogenesis from a 'wear and tear' disease to a disease affecting entire joint. Extensive studies have been conducted to understand the underlying mechanisms of OA using genetic mouse models and ex vivo joint tissues derived from individuals with OA. These studies revealed that multiple signalling pathways are involved in OA development, including the canonical Wnt/β-catenin signalling and its interaction with other signalling pathways, such as transforming growth factor β (TGF-β), bone morphogenic protein (BMP), Indian Hedgehog (Ihh), nuclear factor κB (NF-κB), fibroblast growth factor (FGF), and Notch. The identification of signalling interaction and underlying mechanisms are currently underway and the specific molecule(s) and key signalling pathway(s) playing a decisive role in OA development need to be evaluated. This review will focus on recent progresses in understanding of the critical role of Wnt/β-catenin signalling in OA pathogenesis and interaction of β-catenin with other pathways, such as TGF-β, BMP, Notch, Ihh, NF-κB, and FGF. Understanding of these novel insights into the interaction of β-catenin with other pathways and its integration into a complex gene regulatory network during OA development will help us identify the key signalling pathway of OA pathogenesis leading to the discovery of novel therapeutic strategies for OA intervention.

Chondrocyte-Targeted Delivery System of Sortase A-Engineered Extracellular Vesicles Silencing MMP13 for Osteoarthritis Therapy

Targeted drug delivery and the reduction of off-target effects are crucial for the promising clinical application of nucleic acid drugs. To address this challenge, a new approach for treating osteoarthritis (OA) that accurately delivers antisense oligonucleotides (ASO) targeting matrix metalloproteinase-13 (ASO-MMP13) to chondrocytes, is developed. Small extracellular vesicles (exos) are ligated with chondrocyte affinity peptide (CAP) using Sortase A and subsequently incubated with cholesterol-modified ASO-MMP13 to construct a chondrocyte-targeted drug delivery exo (CAP-exoASO). Compared with exos without CAP (ExoASO), CAP-exoASOs attenuate IL-1β-induced chondrocyte damage and prolong the retention time of ASO-MMP13 in the joint without distribution in major organs following intra-articular injection. Notably, CAP-exoASOs decrease MMP13 expression (P < 0.001) and upregulate COL2A1 expression (P = 0.006), resulting in reorganization of the cartilage matrix and alleviation of progression in the OA model. Furthermore, the Osteoarthritis Research Society International (OARSI) score of articular cartilage tissues treated with CAP-exoASO is comparable with that of healthy rats (P = 0.148). A mechanistic study demonstrates that CAP-exoASO may reduce inflammation by suppressing the IL-17 and TNF signaling pathways. Based on the targeted delivery effect, CAP-exoASOs successfully accomplish cartilage repair and have considerable potential for development as a promising therapeutic modality for satisfactory OA therapy.

FGF Ligands and Receptors in Osteochondral Tissues of the Temporomandibular Joint in Young and Aging Mice

OBJECTIVE

Fibroblast growth factors (FGFs) are a family of 22 proteins and 4 FGF receptors (FGFRs) that are crucial elements for normal development. The contribution of different FGFs and FGFRs for the homeostasis or disease of the cartilage from the mandibular condyle is unknown. Therefore, our goal was to characterize age-related alterations in the protein expression of FGF ligands and FGFRs in the mandibular condyle of mice.

METHOD

Mandibular condyles of 1-, 6-, 12-, 18-, and 24-month-old C57BL/6J male mice (5 per group) were collected and histologically sectioned. Immunofluorescence for FGFs that have been reported to be relevant for chondrogenesis (FGF2, FGF8, FGF9, FGF18) as well as the activated/phosphorylated FGFRs (pFGFR1, pFGFR3) was carried out.

RESULTS

FGF2 and FGF8 were strongly expressed in the cartilage and subchondral bone of 1-month-old mice, but the expression shifted mainly to the subchondral bone as mice aged. FGF18 and pFGFR3 expression was limited to the cartilage of 1-month-old mice only. Meanwhile, pFGFR1 and FGF9 were mostly limited to the cartilage with a significant increase in expression as mice aged.

CONCLUSIONS

Our results indicate FGF2 and FGF8 are important growth factors for mandibular condylar cartilage growth in young mice but with limited role in the cartilage of older mice. In addition, the increased expression of pFGFR1 and FGF9 and the decreased expression of pFGFR3 and FGF18 as mice aged suggest the association of these factors with aging and osteoarthritis of the cartilage of the mandibular condyle.

Novel insights into the role of ubiquitination in osteoarthritis

Ubiquitination (Ub) and deubiquitination are crucial post-translational modifications (PTMs) that precisely regulate protein degradation. Under the catalysis of a cascade of E1-E2-E3 ubiquitin enzymes, ubiquitination extensively regulates protein degradation exerting direct impact on various cellular processes, while deubiquitination opposes the effect of ubiquitination and prevents proteins from degradation. Notably, such dynamic modifications have been widely investigated to be implicated in cell cycle, transcriptional regulation, apoptosis and so on. Therefore, dysregulation of ubiquitination and deubiquitination could lead to certain diseases through abnormal protein accumulation and clearance. Increasing researches have revealed that the dysregulation of catalytic regulators of ubiquitination and deubiquitination triggers imbalance of cartilage homeostasis that promotes osteoarthritis (OA) progression. Hence, it is now believed that targeting on Ub enzymes and deubiquitinating enzymes (DUBs) would provide potential therapeutic pathways. In the following sections, we will summarize the biological role of Ub enzymes and DUBs in the development and progression of OA by focusing on the updating researches, with the aim of deepening our understanding of the underlying molecular mechanism of OA pathogenesis concerning ubiquitination and deubiquitination, so as to explore novel potential therapeutic targets of OA treatment.

Hsa_circular RNA_0045474 Facilitates Osteoarthritis Via Modulating microRNA-485-3p and Augmenting Transcription Factor 4

Circular RNA (circRNA) influences on the pathological process of osteoarthritis (OA) and may be a potential marker for disease diagnosis. The study was to scrutinize the association of circ_0045474 with OA. Clinical samples of OA patients were collected, and 12 circRNAs derived from KPNA2 gene were examined. CHON-001 cells were stimulated with IL-1β to construct an OA chondrocyte model. miR-485-3p, transcription factor 4 (TCF4) and circ_0045474, type II procollagen (COL2A1), and human collagenase-3 (MMP13) were tested. Furthermore, cell activities were analyzed. The relationship between miR-485-3p, TCF4, and circ_0045474 was determined. The role of circ_0045474 in vivo was further confirmed by constructing an OA mouse model by anterior cruciate ligament transection. circ_0045474 expression was elevated in OA patients. Suppressing circ_0045474 restrained IL-1β-stimulated extracellular matrix degradation, inflammatory cytokine secretion, and chondrocyte apoptosis. Circ_0045474 competitively combined with miR-485-3p, while TCF4 was the target of miR-485-3p. Circ_0045474 modulated IL-1β-stimulated extracellular matrix degradation, inflammatory cytokine secretion, and chondrocyte apoptosis via miR-485-3p/TCF4 axis. Suppressing circ 0045474 was effective to alleviate OA in mice. Silenced circ_0045474 suppresses OA progression in vitro and vivo via miR-485-3p/TCF4 axis. In short, circ_0045474 can be considered a novel therapeutic target for OA.

Surface functionalization of exosomes for chondrocyte-targeted siRNA delivery and cartilage regeneration

Osteoarthritis (OA) is the most prevalent degenerative cartilage disease, but no effective treatment is currently available to ameliorate the dysregulation of cartilage catabolism. Cartilage degeneration is closely related to the change in the physiology of chondrocytes: for example, chondrocytes of the OA patients overexpress matrix metallopeptidase 13 (MMP13), a.k.a. collagenase 3, which damages the extracellular matrix (ECM) of the cartilage and deteriorate the disease progression. Inhibiting MMP13 has shown to be beneficial for OA treatments, but delivering therapeutics to the chondrocytes embedded in the dense cartilage is a challenge. Here, we engineered the exosome surface with the cartilage affinity peptide (CAP) through lipid insertion to give chondrocyte-targeting exosomes, CAP-Exo, which was then loaded with siRNA against MMP13 (siMMP13) in the interior to give CAP-Exo/siMMP13. Intra-articular administration of CAP-Exo/siMMP13 reduced the MMP13 level and increased collagen COL2A1 and proteoglycan in cartilage in a rat model of anterior cruciate ligament transection (ACLT)-induced OA. Proteomic analysis showed that CAP-Exo/siMMP13 treatment restored the altered protein levels in the IL-1β-treated chondrocytes. Taken together, a facile exosome engineering method enabled targeted delivery of siRNA to chondrocytes and chondrocyte-specific silencing of MMP13 to attenuate cartilage degeneration.

Expression of semaphorin-3A in the joint and role in osteoarthritis

Osteoarthritis (OA) is characterised by the deterioration of cartilage in the joints and pain. We hypothesise that semaphorin-3A (sema-3A), a chemorepellent for sensory nerves, plays a role in joint degradation and pain. We used the mechanical joint loading (MJL) model of OA to investigate sema-3A expression in the joint and examine its association with the development of OA and pain. We also analyse its effect on chondrocyte differentiation using the ATDC5 cell line. We demonstrate that sema-3A is present in most tissues in the healthy joint and its expression increases in highly innervated tissues, such as cruciate ligaments, synovial lining and subchondral bone, in loaded compared to nonloaded control joints. In contrast, sema-3A expression in cartilage was decreased in the severe OA induced by the application of high loads. There was a significant increase in circulating sema-3A, 6 weeks after MJL compared to the nonloaded mice. mRNA for sema-3A and its receptor Plexin A1 were upregulated in the dorsal root ganglia of mice submitted to MJL. These increases were supressed by zoledronate, an inhibitor of bone pain. Sema-3A was expressed at all stages of Chondrocyte maturation and, when added exogenously, stimulated expression of markers of chondrocyte differentiation. This indicates that sema-3A could affect joint tissues distinctively during the development of OA. In highly innervated joint tissues, sema-3A could control innervation and/or induce pain-associated neuronal changes. In cartilage, sema-3A could favour its degeneration by modifying chondrocyte differentiation.

Identification of key miRNAs in unilateral mastication-induced disruption of cartilage homeostasis

OBJECTIVE

The present study identified potentially pivotal miRNAs contributing to chondrogenic differentiation in temporomandibular joint suffering abnormal stress.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into control and experimental unilateral mastication (EUM) group. Bone micro-structure parameters was detected by micro-CT, and FGF-1 and MMP-1 expression was examined by immunohistochemistry. Differentially expressed miRNAs of bilateral condyle cartilage were screened via miRNA microarray at 4- and 8-week EUM, then further verified using quantitative reverse-transcription PCR. Over-expression of five differentially expressed miRNAs in chondrocytes was triggered by transfecting miRNA mimics. The expression of MMP-13, Col-II, OPN, and Runx2 was verified by western blotting.

RESULTS

Expressions of FGF-1 and MMP-1 in right condyles gradually increased from 2 to 6 weeks after EUM. A total of 20 differentially expressed miRNAs were regulated by EUM, which related to cell proliferation, invasion, and osteoblast differentiation pathways. The over-expression of miR-148a-3p and miR-1-3p led to down-regulation of Col-II, while MMP-13 and Runx2 were up-regulated by induction of hypotrophic differentiation or IL-1β stimulation. These findings suggested that miR-148a-3p and miR-1-3p promote chondrogenic differentiation.

CONCLUSIONS

Several pivotal miRNAs were found to be related to chondrogenic differentiation, which provides novel insight into pathogenic mechanisms of cartilage homeostasis.

Syringic acid promotes cartilage extracellular matrix generation and attenuates osteoarthritic cartilage degradation by activating TGF-β/Smad and inhibiting NF-κB signaling pathway

Osteoarthritis (OA) is a common chronic degenerative disease which is characterized by the disruption of articular cartilage. Syringic acid (SA) is a phenolic compound with anti-inflammatory, antioxidant, and other effects including promoting osteogenesis. However, the effect of SA on OA has not yet been reported. Therefore, the purpose of our study was to investigate the effect and mechanism of SA on OA in a mouse model of medial meniscal destabilization. The expressions of genes were evaluated by qPCR or western blot or immunofluorescence. RNA-seq analysis was performed to examine gene transcription alterations in chondrocytes treated with SA. The effect of SA on OA was evaluated using destabilization of the medial meniscus model of mice. We found that SA had no obvious toxic effect on chondrocytes, while promoting the expressions of chondrogenesis-related marker genes. The results of RNA-seq analysis showed that extracellular matrix-receptor interaction and transforming growth factor-β (TGF-β) signaling pathways were enriched among the up-regulated genes by SA. Mechanistically, we demonstrated that SA transcriptionally activated Smad3. In addition, we found that SA inhibited the overproduction of lipopolysaccharide-induced inflammation-related cytokines including tumor necrosis factor-α and interleukin-1β, as well as matrix metalloproteinase 3 and matrix metalloproteinase 13. The cell apoptosis and nuclear factor-kappa B (NF-κB) signaling were also inhibited by SA treatment. Most importantly, SA attenuated cartilage degradation in a mouse OA model. Taken together, our study demonstrated that SA could alleviate cartilage degradation in OA by activating the TGF-β/Smad and inhibiting NF-κB signaling pathway.

Effects of a Combination of Polynucleotide and Hyaluronic Acid for Treating Osteoarthritis

Knee osteoarthritis (OA), an age-related degenerative disease characterized by severe pain and disability, is treated using polynucleotides (PNs) and hyaluronic acid (HA). The intra-articular (IA) injection of HA has been studied extensively in both animal models and in humans; however, the efficacy and mechanisms of action remain unclear. In addition, there has been a paucity of research regarding the use of PN alone or in combination with HA in OA. To investigate the effect of the combined injection of PN and HA in vivo, pathological and behavioral changes were assessed in an OA model. Anterior cruciate ligament transection and medial meniscectomy were performed in Sprague-Dawley rats to create the OA animal model. The locomotor activity improved following PNHA injection, while the OARSI grade improved in the medial tibia and femur. In mild OA, TNFα levels decreased histologically in the PN, HA, and PNHA groups but only the PNHA group showed behavioral improvement in terms of distance. In conclusion, PNHA exhibited anti-inflammatory effects during OA progression and improved locomotor activity regardless of the OARSI grade.

Inhibitory Effect of a Tankyrase Inhibitor on Mechanical Stress-Induced Protease Expression in Human Articular Chondrocytes

We investigated the effects of a Tankyrase (TNKS-1/2) inhibitor on mechanical stress-induced gene expression in human chondrocytes and examined TNKS-1/2 expression in human osteoarthritis (OA) cartilage. Cells were seeded onto stretch chambers and incubated with or without a TNKS-1/2 inhibitor (XAV939) for 12 h. Uni-axial cyclic tensile strain (CTS) (0.5 Hz, 8% elongation, 30 min) was applied and the gene expression of type II collagen a1 chain (COL2A1), aggrecan (ACAN), SRY-box9 (SOX9), TNKS-1/2, a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5), and matrix metalloproteinase-13 (MMP-13) were examined by real-time PCR. The expression of ADAMTS-5, MMP-13, nuclear translocation of nuclear factor-κB (NF-κB), and β-catenin were examined by immunocytochemistry and Western blotting. The concentration of IL-1β in the supernatant was examined by enzyme-linked immunosorbent assay (ELISA). TNKS-1/2 expression was assessed by immunohistochemistry in human OA cartilage obtained at the total knee arthroplasty. TNKS-1/2 expression was increased after CTS. The expression of anabolic factors were decreased by CTS, however, these declines were abrogated by XAV939. XAV939 suppressed the CTS-induced expression of catabolic factors, the release of IL-1β, as well as the nuclear translocation of NF-κB and β-catenin. TNKS-1/2 expression increased in mild and moderate OA cartilage. Our results demonstrated that XAV939 suppressed mechanical stress-induced expression of catabolic proteases by the inhibition of NF-κB and activation of β-catenin, indicating that TNKS-1/2 expression might be associated with OA pathogenesis.

The CREB1 inhibitor 666-15 maintains cartilage homeostasis and mitigates osteoarthritis progression

Aims

cAMP response element binding protein (CREB1) is involved in the progression of osteoarthritis (OA). However, available findings about the role of CREB1 in OA are inconsistent. 666-15 is a potent and selective CREB1 inhibitor, but its role in OA is unclear. This study aimed to investigate the precise role of CREB1 in OA, and whether 666-15 exerts an anti-OA effect.

Methods

CREB1 activity and expression of a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) in cells and tissues were measured by immunoblotting and immunohistochemical (IHC) staining. The effect of 666-15 on chondrocyte viability and apoptosis was examined by cell counting kit-8 (CCK-8) assay, JC-10, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) staining. The effect of 666-15 on the microstructure of subchondral bone, and the synthesis and catabolism of cartilage, in anterior cruciate ligament transection mice were detected by micro-CT, safranin O and fast green (S/F), immunohistochemical staining, and enzyme-linked immunosorbent assay (ELISA).

Results

CREB1 was hyperactive in osteoarthritic articular cartilage, interleukin (IL)-1β-treated cartilage explants, and IL-1β- or carbonyl cyanide 3-chlorophenylhydrazone (CCCP)-treated chondrocytes. 666-15 enhanced cell viability of OA-like chondrocytes and alleviated IL-1β- or CCCP-induced chondrocyte injury through inhibition of mitochondrial dysfunction-associated apoptosis. Moreover, inhibition of CREB1 by 666-15 suppressed expression of ADAMTS4. Additionally, 666-15 alleviated joint degeneration in an ACLT mouse model.

Conclusion

Hyperactive CREB1 played a critical role in OA development, and 666-15 exerted anti-IL-1β or anti-CCCP effects in vitro as well as joint-protective effects in vivo. 666-15 may therefore be used as a promising anti-OA drug.

Single‑cell sequencing, genetics, and epigenetics reveal mesenchymal stem cell senescence in osteoarthritis (Review)

Osteoarthritis (OA) is a chronic joint disease characterized by articular cartilage degeneration, secondary bone hyperplasia, inadequate extracellular matrix synthesis and degeneration of articular cartilage. Mesenchymal stem cells (MSCs) can self‑renew and undergo multidirectional differentiation; they can differentiate into chondrocytes. Aging MSCs have a weakened ability to differentiate, and release various pro‑inflammatory cytokines, which may contribute to OA progression; the other mechanism contributing to OA is epigenetic regulation (for instance, DNA methylation, histone modification and regulation of non‑coding RNA). Owing to the self‑renewal and differentiation ability of MSCs, various MSC‑based exogenous cell therapies have been developed to treat OA. The efficacy of MSC‑based therapy is mainly attributed to cytokines, growth factors and the paracrine effect of exosomes. Recently, extensive studies have been conducted on MSC‑derived exosomes. Exosomes from MSCs can deliver a variety of DNA, RNA, proteins and lipids, thereby facilitating MSC migration and cartilage repair. Therefore, MSC‑derived exosomes are considered a promising therapy for OA. The present review summarized the association between MSC aging and OA in terms of genetics and epigenetics, and characteristics of MSC‑derived exosomes, and the mechanism to alleviate OA cartilage damage.

Exploration and breakthrough in the mode of chondrocyte death - A potential new mechanism for osteoarthritis

Osteoarthritis (OA) is a frequent chronic joint disease in orthopedics that effects individuals and society significantly. Obesity, aging, genetic susceptibility, and joint misalignment are all known risk factors for OA, but its pathomechanism is still poorly understood. Researches have revealed that OA is a much complex process related to inflammation, metabolic and chondrocyte death. It can affect all parts of the joint and is characterized by causing chondrocyte death and extracellular matrix descent. Previously, OA was thought to develop from excessive mechanical loading leading to the destruction of articular cartilage. Since some programmed cell deaths and OA share a pattern of chondrocyte destruction, it is likely that OA also involves programmed cell death. Even though chondrocyte apoptosis and pyroptosis have been investigated in OA, clarifing solely conventional cell death pathways is still insufficient to understand the pathophysiology of osteoarthritis. With more researches, it has been discovered that osteoarthritis and other new cell death processes, including PANoptosis, ferroptosis, and cell senescence, are strongly associated. Among these, PANoptosis combines the key traits of pyroptosis, cell apoptosis, and necrotic apoptosis into a highly coordinated and dynamically balanced programmed inflammatory cell death mechanism. Furthermore, we think that PANopotosis might obstruct necroptosis and cell senescence. Therefore, in order to offer direction for therapeutic treatment, we evaluate the development of research on multiple cell death of chondrocytes in OA.

Albumin-binding RNAi Conjugate for Carrier Free Treatment of Arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are joint diseases that are associated with pain and lost quality of life. No disease modifying OA drugs are currently available. RA treatments are better established but are not always effective and can cause immune suppression. Here, an MMP13-selective siRNA conjugate was developed that, when delivered intravenously, docks onto endogenous albumin and promotes preferential accumulation in articular cartilage and synovia of OA and RA joints. MMP13 expression was diminished upon intravenous delivery of MMP13 siRNA conjugates, consequently decreasing multiple histological and molecular markers of disease severity, while also reducing clinical manifestations such as swelling (RA) and joint pressure sensitivity (RA and OA). Importantly, MMP13 silencing provided more comprehensive OA treatment efficacy than standard of care (steroids) or experimental MMP inhibitors. These data demonstrate the utility of albumin 'hitchhiking' for drug delivery to arthritic joints, and establish the therapeutic utility of systemically delivered anti-MMP13 siRNA conjugates in OA and RA.

Editorial summary

Lipophilic siRNA conjugates optimized for albumin binding and "hitchhiking" can be leveraged to achieve preferential delivery to and gene silencing activity within arthritic joints. Chemical stabilization of the lipophilic siRNA enables intravenous siRNA delivery without lipid or polymer encapsulation. Using siRNA sequences targeting MMP13, a key driver of arthritis-related inflammation, albumin hitchhiking siRNA diminished MMP13, inflammation, and manifestations of osteoarthritis and rheumatoid arthritis at molecular, histological, and clinical levels, consistently outperforming clinical standards of care and small molecule MMP antagonists.

Pathogenic Mechanisms and Therapeutic Approaches in Obesity-Related Knee Osteoarthritis

The knee is the joint most frequently involved in osteoarthritis, a common joint disorder in the adult population that is associated with significant chronic joint pain, reduced mobility and quality of life. Recent studies have established an association between obesity and the development of knee osteoarthritis that goes beyond the increased mechanical load on the knees as weight-bearing joints. This link is based on the maintenance of a chronic low-grade inflammation, altered secretion of adipokines by the adipose tissue and development of sarcopenia. Major adipokines involved in the pathogenesis of obesity-related knee osteoarthritis include adiponectin, which appears to have a protective effect, as well as leptin, resistin and visfatin, which are associated with higher pain scores and more severe structural damage. Joint pain in knee osteoarthritis may be both nociceptive and neuropathic and is the result of complex mechanisms driven by nerve growth factor, calcitonin gene-related peptide and pro-inflammatory cytokines. The role of endogenous cannabinoids and gut microbiota in common mechanisms between obesity and knee pain has recently been studied. The aim of the present review is to highlight major pathogenic mechanisms in obesity-related knee osteoarthritis with special attention on pain and to comment on possible therapeutic approaches.

Piperlongumine mediates amelioration of osteoarthritis via inhibition of chondrocyte senescence and inflammation in a goat ex vivo model

In osteoarthritis (OA), chondrocytes manifest senescence, which results in a vicious signaling loop that aids the progression of the disease. More specifically, inflammation-associated senescence is one of the major regulators of the initiation and progression of OA. Therefore, we targeted senescence through inflammation with a pharmacological approach for OA amelioration. In this study, we first confirmed the suitability of the IL1β-induced goat ex vivo OA model (emphasizing 3R's principle) for the screening of senotherapeutics, namely, ABT-263, ABT-737, and Piperlongumine (PL), wherein PL showed a positive outcome in the preliminary studies. Thereafter, we determined the cytocompatible concentrations of PL using live/dead staining. Further, treatment of ex vivo OA cartilage with PL exhibited a concentration-dependent increase in the retention of key cartilage matrix components. We then examined the effect of PL on chondrocyte senescence and observed a decreased expression of major senescence markers in the PL-treated groups. Interestingly, PL treatment reduced the expression of major downstream effectors of the chondrocyte senescence pathway in a concentration-dependent manner at both gene and protein levels. Moreover, IL1β-induced elevated levels of oxidative stress and DNA damage in cartilage explants were rescued by all the tested concentrations of PL. In addition, PL also reduced the expression of major inflammatory markers of OA in the goat ex vivo OA model. Finally, we proposed a model for the mechanism of action of PL in the treatment of OA. Overall, PL showed a promising outcome as a senotherapeutic for the amelioration of OA in the goat ex vivo OA model.

Dihydrotanshinone I protects human chondrocytes and alleviates damage from spontaneous osteoarthritis in a guinea pig model

Osteoarthritis (OA) is the most common degenerative joint disease. Currently, no satisfactory pharmacological treatment exists for OA. The potential anti-inflammatory properties of Dihydrotanshinone I (DHT) have been reported, but its effects on OA are unclear. In this study, we assess the impact of DHT on the viability of human chondrocytes in vitro. We then use a guinea pig model to investigate the effects of DHT on knee osteoarthritis progression. Twelve-week-old Dunkin Hartley guinea pigs spontaneously developing OA were intraperitoneally injected with different doses of DHT for eight weeks. Micro-CT analysis was performed on the subchondral bone in the knee, and histological assessment of the knee joint was done using stained sections, the ratio of hyaline to calcified cartilage, and Mankin scores. DHT successfully restored IL-1β-induced decreases in cell viability in human primary chondrocytes. In the guinea pig model, intraperitoneal injections of DHT ameliorated age-induced OA, effectively reduced the expression level of two cartilage metabolism-related genes (ADAMTS4 and MMP13) and decreased the inflammatory biomarker IL-6 in the serum of guinea pigs developing spontaneous osteoarthritis. These findings demonstrate DHT's protective effects on chondrocytes and suggest that it alleviates cartilage degradation and proteoglycan loss in OA.

A study on the therapeutic potential of graphene titanate nanocomposite for treating chemically induced arthritis in rats

Nanotechnology holds substantial promise in the innovative therapies for rheumatoid arthritis (RA). The current study was designed to synthesize and characterize a new graphene titanate nanocomposite (GTNc) and explore its anti-arthritic, anti-inflammatory, and antioxidant potencies against Complete Freund's adjuvant (CFA)-induced arthritis in rats, as well as investigate the underlying molecular mechanisms. Our characterization methods included XRD, FT-IR, SEM, EDX, zeta potential, practical size, and XRF to characterize the novel GTNc. Our findings revealed that arthritic rats treated with GTNc exhibited lower levels of RF, CRP, IL-1β, TNF-α, IL-17, and ADAMTS-5, and higher levels of IL-4 and TIMP-3. In arthritic rats, GTNc reduced LPO levels while increasing GSH content and GST antioxidant activity. Additionally, GTNc decreased the expression of the TGF-β mRNA gene in arthritic rats. Histopathological investigation showed that GTNc reduced inflammatory cell infiltration, cartilage degradation, and bone destruction in joint injuries caused by CFA in the arthritic rats. Collectively, the anti-arthritic, anti-inflammatory, and antioxidant properties of GTNc appear promising for future arthritis treatments and bone disability research.

Chondroprotective effects of Protaetia brevitarsis seulensis larvae as an edible insect on osteoarthritis in mice

Osteoarthritis (OA) is a common chronic joint inflammatory disease characterized by progressive destruction of the articular cartilage, bone remodeling, and excessive chronic pain. Most therapeutic approaches do not rescue the progression of OA effectively or provide relief of symptoms. Protaetia brevitarsis seulensis larva (PBSL), which is attracting attention, is an edible insect with very high nutritional value and herbal medicine for the treatment of blood stasis, hepatic disease, and various inflammatory diseases. However, the effect of PBSL on OA has not yet been investigated. This study aimed to demonstrate the effects of PBSL water extract on the progression of OA using monosodium iodoacetate (MIA)-induced mice and SW1353 chondrocytes or murine macrophages. We injected MIA into the intraarticular area of mice following pretreatment with either saline or PBSL (200 mg/kg) for 2 weeks, and then locomotor activity, microcomputed tomography and histopathological analysis, quantitative reverse transcriptase-polymerase chain reaction analysis, and western blot analysis were performed. To determine the molecular effects of PBSL, we used interleukin-1β (IL-1β)-induced SW1353 chondrosarcoma or lipopolysaccharide (LPS)-stimulated macrophages. Pretreatment with PBSL diminished the symptoms of OA. Physical activity, articular cartilage damage, and the generation of microfractures were rescued by pretreatment with PBSL in the mouse model. Pretreatment with PBSL suppressed the progress of OA through the regulation of articular cartilage degradation genes and inflammation in both in vivo and in vitro models. Our results demonstrated that PBSL has value as edible insect that can be used in the development of functional foods for OA.

Classification of distinct osteoarthritis subtypes with different knee joint tissues by gene expression profiles

Aims

Knee osteoarthritis (OA) involves a variety of tissues in the joint. Gene expression profiles in different tissues are of great importance in order to understand OA.

Methods

First, we obtained gene expression profiles of cartilage, synovium, subchondral bone, and meniscus from the Gene Expression Omnibus (GEO). Several datasets were standardized by merging and removing batch effects. Then, we used unsupervised clustering to divide OA into three subtypes. The gene ontology and pathway enrichment of three subtypes were analyzed. CIBERSORT was used to evaluate the infiltration of immune cells in different subtypes. Finally, OA-related genes were obtained from the Molecular Signatures Database for validation, and diagnostic markers were screened according to clinical characteristics. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to verify the effectiveness of markers.

Results

C1 subtype is mainly concentrated in the development of skeletal muscle organs, C2 lies in metabolic process and immune response, and C3 in pyroptosis and cell death process. Therefore, we divided OA into three subtypes: bone remodelling subtype (C1), immune metabolism subtype (C2), and cartilage degradation subtype (C3). The number of macrophage M0 and activated mast cells of C2 subtype was significantly higher than those of the other two subtypes. COL2A1 has significant differences in different subtypes. The expression of COL2A1 is related to age, and trafficking protein particle complex subunit 2 is related to the sex of OA patients.

Conclusion

This study linked different tissues with gene expression profiles, revealing different molecular subtypes of patients with knee OA. The relationship between clinical characteristics and OA-related genes was also studied, which provides a new concept for the diagnosis and treatment of OA.

Articular Cartilage Regeneration via Induced Chondrocyte Autophagy by Sustained Release of Leptin Inhibitor from Thermo-Sensitive Hydrogel through STAT3/REDD1/mTORC1 Cascade

The pathophysiology of osteoarthritis (OA) is closely linked to autophagy abnormalities in articular chondrocytes, the sole mature cell type in healthy cartilage. Nevertheless, the precise molecular mechanism remains uncertain. Previous research has demonstrated that leptin activates mTORC1 , thereby inhibiting chondrocyte autophagy during the progression of OA. In this study, it is demonstrated that the presence of leptin induces a substantial increase in the expression of STAT3, leading to a notable decrease in REDD1 expression and subsequent phosphorylation of p70S6K, a recognized downstream effector of mTORC1. Conversely, inhibition of leptin yields contrasting effects. Additionally, the potential advantages of utilizing a sustained intra-articular release of a leptin inhibitor (LI) via an injectable, thermosensitive poly(D,L-lactide)-poly(ethylene glycol)-poly(D,L-lactide) (PDLLA-PEG-PDLLA: PLEL) hydrogel delivery system for the purpose of investigating its impact on cartilage repair are explored. The study conducted on LI-loaded PLEL (PLEL@LI) demonstrates remarkable efficacy in inhibiting OA and displays encouraging therapeutic advantages in the restoration of subchondral bone and cartilage. These findings establish a solid foundation for the advancement of a pioneering treatment approach utilizing PLEL@LI for OA.

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.

Tick tock, the cartilage clock

Osteoarthritis (OA) is the most common age-related joint disease, affecting articular cartilage and other joint structures, causing severe pain and disability. Due to a limited understanding of the underlying disease pathogenesis, there are currently no disease-modifying drugs for OA. Circadian rhythms are generated by cell-intrinsic timekeeping mechanisms which are known to dampen during ageing, increasing disease risks. In this review, we focus on one emerging area of chondrocyte biology, the circadian clocks. We first provide a historical perspective of circadian clock discoveries and the molecular underpinnings. We will then focus on the expression and functions of circadian clocks in articular cartilage, including their rhythmic target genes and pathways, links to ageing, tissue degeneration, and OA, as well as tissue niche-specific entrainment pathways. Further research into cartilage clocks and ageing may have broader implications in the understanding of OA pathogenesis, the standardization of biomarker detection, and the development of novel therapeutic routes for the prevention and management of OA and other musculoskeletal diseases.

CODD-Pred: A Web Server for Efficient Target Identification and Bioactivity Prediction of Small Molecules

Target identification and bioactivity prediction are critical steps in the drug discovery process. Here we introduce CODD-Pred (COmprehensive Drug Design Predictor), an online web server with well-curated data sets from the GOSTAR database, which is designed with a dual purpose of predicting potential protein drug targets and computing bioactivity values of small molecules. We first designed a double molecular graph perception (DMGP) framework for target prediction based on a large library of 646 498 small molecules interacting with 640 human targets. The framework achieved a top-5 accuracy of over 80% for hitting at least one target on both external validation sets. Additionally, its performance on the external validation set comprising 200 molecules surpassed that of four existing target prediction servers. Second, we collected 56 targets closely related to the occurrence and development of cancer, metabolic diseases, and inflammatory immune diseases and developed a multi-model self-validation activity prediction (MSAP) framework that enables accurate bioactivity quantification predictions for small-molecule ligands of these 56 targets. CODD-Pred is a handy tool for rapid evaluation and optimization of small molecules with specific target activity. CODD-Pred is freely accessible at http://codd.iddd.group/.

Disease-modifying agents in osteoarthritis: where are we now and what does the future hold?

Cite this article: Bone Joint Res  2023;12(10):654–656.

Osteoarthritis improvement effect of Chrysanthemum zawadskii var. latilobum extract in relation to genotype

Objectives: To determine whether SNPs of osteoarthritis (OA)-related genes predict the effect of Chrysanthemum zawadskii var. latilobum (CZ) extract in OA patients with OA. Subjects/methods: To analyze correlations between CZ extract effects in humans and their genotypes, 121 Korean patients with OA were recruited. Patients ingested 600 mg/day of the CZ extract GCWB106 (one tablet daily), including 250-mg CZ, or placebo (one tablet daily) for 12 weeks. Twenty SNPs were genotyped in 11 genes associated with OA pathogenesis, including tumor necrosis factor-alpha (TNF-α) and matrix metalloproteinases (MMPs), and 9 genes involved in OA-related dietary intervention. The Visual Analogue Scale (VAS) and Korean Western Ontario and McMaster Universities (K-WOMAC) were measured as indicators of GCWB106 effect. Statistical comparisons were performed using Kruskal-Wallis tests to identify associations between these scales and genotyped loci in patients with OA. Results: Three SNPs (PPARG rs3856806, MMP13 rs2252070, and ZIP2 rs2234632) were significantly associated with the degree of change in VAS pain score. Homozygous CC genotype carriers of rs3856806, G allele carriers (GA or GG) of rs2252070, and T allele carriers (GT or TT) of rs2234632 showed lower VAS score (i.e., less severe symptoms) in the GCWB106 group (n=53) than the placebo group (n=57) (p=0.026, p=0.009, and p=0.025, respectively). Gene-gene interaction effects on GCWB106-mediated pain relief were then examined, and it was found that the addition of each genotype resulted in a greater decrease in VAS pain score in the GCWB106 group (p=0.0024) but not the placebo group (p=0.7734). Conclusions: These novel predictive markers for the pain-relieving effects of GCWB106 may be used in the personalized treatment of patients with OA.

Metabolic rewiring controlled by c-Fos governs cartilage integrity in osteoarthritis

OBJECTIVES

The activator protein-1 (AP-1) transcription factor component c-Fos regulates chondrocyte proliferation and differentiation, but its involvement in osteoarthritis (OA) has not been functionally assessed.

METHODS

c-Fos expression was evaluated by immunohistochemistry on articular cartilage sections from patients with OA and mice subjected to the destabilisation of the medial meniscus (DMM) model of OA. Cartilage-specific c-Fos knockout (c-FosΔCh) mice were generated by crossing c-fosfl/fl to Col2a1-CreERT mice. Articular cartilage was evaluated by histology, immunohistochemistry, RNA sequencing (RNA-seq), quantitative reverse transcription PCR (qRT-PCR) and in situ metabolic enzyme assays. The effect of dichloroacetic acid (DCA), an inhibitor of pyruvate dehydrogenase kinase (Pdk), was assessed in c-FosΔCh mice subjected to DMM.

RESULTS

FOS-positive chondrocytes were increased in human and murine OA cartilage during disease progression. Compared with c-FosWT mice, c-FosΔCh mice exhibited exacerbated DMM-induced cartilage destruction. Chondrocytes lacking c-Fos proliferate less, have shorter collagen fibres and reduced cartilage matrix. Comparative RNA-seq revealed a prominent anaerobic glycolysis gene expression signature. Consistently decreased pyruvate dehydrogenase (Pdh) and elevated lactate dehydrogenase (Ldh) enzymatic activities were measured in situ, which are likely due to higher expression of hypoxia-inducible factor-1α, Ldha, and Pdk1 in chondrocytes. In vivo treatment of c-FosΔCh mice with DCA restored Pdh/Ldh activity, chondrocyte proliferation, collagen biosynthesis and decreased cartilage damage after DMM, thereby reverting the deleterious effects of c-Fos inactivation.

CONCLUSIONS

c-Fos modulates cellular bioenergetics in chondrocytes by balancing pyruvate flux between anaerobic glycolysis and the tricarboxylic acid cycle in response to OA signals. We identify a novel metabolic adaptation of chondrocytes controlled by c-Fos-containing AP-1 dimers that could be therapeutically relevant.

Synthesis Folate-linked Chitosan-coated Quetiapine/BSA Nano-Carriers as the Efficient Targeted Anti-Cancer Drug Delivery System

Quetiapine (QTP) has been known to suppress cancer progression in patients suffering from mental disorders. This study aimed to produce the folate-linked chitosan-coated quetiapine/BSA nano-carriers (FCQB-NCs) and evaluate their antioxidant, apoptotic, and anti-metastatic potentials on prostate, pancreas, colon, and breast cancer cell lines. The FCQB-NCs were designed, produced, and characterized using DLS, FESEM, FTIR, and Zeta potential techniques. The nano-carriers antioxidant activity was studied by applying ABTS, DPPH, and FRAP assays. The FCQB-NCs' cytotoxicity and apoptotic/metastatic properties were evaluated utilizing MTT assay and qPCR-based analysis for measuring the apoptotic (Nf-KB)/metastatic (MMP2, MMP9, and MMP13) gene expression, respectively. The AO/PI fluorescent cell staining, DAPI staining, and scratch assay methods were conducted to verify the apoptotic and anti-metastatic activities of FCQB-NCs. The 51-nm FCQB-NCs (PDI = 0.26) exhibited antioxidant activity and selectively decreased the MDA-MB-231 cancer cells' viability by inducing Nf-KB overexpression, which caused the apoptosis pathway activation. Moreover, the FCQB-NCs suppressed the MDA-MB-231 cells' metastatic activity by down-regulating the MMP2, MMP9, and MMP13 gene expression, verified by detecting the decreased migration rate. The FCQB-NCs selectively induced apoptosis and suppressed metastasis in the human breast cancer cell line, which can be attributed to the stepwise release of QTP in two primary (extra-cellular release) and secondary (intra-cellular release) phases. The efficient selective cytotoxic impact of FCQB-NCs can be due to the novel stepwise release mechanism of the FCQB-NCs based on the two-phase entrapment of QTP by BSA and chitosan molecules. Therefore, FCQB-NCs have the potential to be used as an efficient selective anti-breast cancer.

The surgical destabilization of the abductor muscle leads to development of instability-associated hip osteoarthritis in mice

Osteoarthritis (OA) of the hip is a common and debilitating painful joint disease. However, there is paucity of surgically induced hip OA models in small animals that allow scientists to study the onset and progression of the disease. A growing body of evidence indicates a positive association between periarticular myotendinous pathology and the development of hip OA. Thus, in the current study, we aimed to establish a novel mouse instability-associated hip OA model via selective injury of the abductor complex around the hip joint. C57BL6/J mice were randomized to sham surgery or abductor injury, in which the myotendinous insertion at the third trochanter and greater trochanter were surgically detached. Mice were allowed free active movement until they were sacrificed at either 3 weeks or 20 weeks post-injury. Histologic analyses and immunohistochemical staining of the femoral head articular cartilage were performed, along with microCT (µCT) analysis to assess subchondral bone remodeling. We observed that mice receiving abductor injury exhibited significantly increased instability-associated OA severity with loss of proteoglycan and type II collagen staining compared to sham control mice at 20 weeks post-surgery, while comparable matrix metalloproteinase 13 expression was observed between injury and sham groups. No significant differences in subchondral bone remodeling were found after 3 or 20 weeks following injury. Our study further supports the link between abductor dysfunction and the development of instability-associated hip OA. Importantly, this novel surgically induced hip OA mouse model may provide a valuable tool for future investigations into the pathogenesis and treatment of hip OA.

Effects of Modified Glucosamine on the Chondrogenic Potential of Circulating Stem Cells under Experimental Inflammation

Glucosamine (GlcN) is a glycosaminoglycan (GAGs) constituent in connective tissues. It is naturally produced by our body or consumed from diets. In the last decade, in vitro and in vivo trials have demonstrated that the administration of GlcN or its derivates has a protective effect on cartilage when the balance between catabolic and anabolic processes is disrupted and cells are no longer able to fully compensate for the loss of collagen and proteoglycans. To date, these benefits are still controversial because the mechanism of action of GlcN is not yet well clarified. In this study, we have characterized the biological activities of an amino acid (AA) derivate of GlcN, called DCF001, in the growth and chondrogenic induction of circulating multipotent stem cells (CMCs) after priming with tumor necrosis factor-alpha (TNFα), a pleiotropic cytokine commonly expressed in chronic inflammatory joint diseases. In the present work, stem cells were isolated from the human peripheral blood of healthy donors. After priming with TNFα (10 ng/mL) for 3 h, cultures were treated for 24 h with DCF001 (1 μg/mL) dissolved in a proliferative (PM) or chondrogenic (CM) medium. Cell proliferation was analyzed using a Corning^® Cell Counter and trypan blue exclusion technique. To evaluate the potentialities of DCF001 in counteracting the inflammatory response to TNFα, we measured the amount of extracellular ATP (eATP) and the expression of adenosine-generating enzymes CD39/CD73, TNFα receptors, and NF-κB inhibitor IκBα using flow cytometry. Finally, total RNA was extracted to perform a gene expression study of some chondrogenic differentiation markers (COL2A1, RUNX2, and MMP13). Our analysis has shed light on the ability of DCF001 to (a) regulate the expression of CD39, CD73, and TNF receptors; (b) modulate eATP under differentiative induction; (c) enhance the inhibitory activity of IκBα, reducing its phosphorylation after TNFα stimulation; and (d) preserve the chondrogenic potentialities of stem cells. Although preliminary, these results suggest that DCF001 could be a valuable supplement for ameliorating the outcome of cartilage repair interventions, enhancing the efficacy of endogenous stem cells under inflammatory stimuli.

Recent targets of osteoarthritis research

Osteoarthritis is one of the most common diseases and poses a significant medical burden worldwide. Currently, the diagnosis and treatment of osteoarthritis primarily rely on clinical symptoms and changes observed in radiographs or other image modalities. However, identification based on reliable biomarkers would greatly improve early diagnosis, help with precise monitoring of disease progression, and provide aid for accurate treatment. In recent years, several biomarkers for osteoarthritis have been identified, including image modalities and biochemical biomarkers such as collagen degradation products, pro- or anti-inflammatory cytokines, micro RNAs, long non-coding RNAs, and circular RNAs. These biomarkers offer new insights in the pathogenesis of osteoarthritis and provide potential targets for further research. This article reviews the evolution of osteoarthritis biomarkers from the perspective of pathogenesis and emphasizes the importance of continued research to improve the diagnosis, treatment, and management of osteoarthritis.

The Protective Effect of Selenium Nanoparticles in Osteoarthritis: In vitro and in vivo Studies

Introduction

Osteoarthritis (OA) is a common chronic joint disease characterized by articular cartilage degeneration. OA usually manifests as joint pain, limited mobility, and joint effusion. Currently, the primary OA treatment is non-steroidal anti-inflammatory drugs (NSAIDs). Although they can alleviate the disease's clinical symptoms and signs, the drugs have some side effects. Selenium nanoparticles (SeNPs) may be an alternative to relieve OA symptoms.

Materials and Results

We confirmed the anti-inflammatory effect of selenium nanoparticles (SeNPs) in vitro and in vivo experiments for OA disease in this study. In vitro experiments, we found that SeNPs could significantly reduce the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the major inflammatory factors, and had significant anti-inflammatory and anti-arthritic effects. SeNPs can inhibit reactive oxygen species (ROS) production and increased glutathione peroxidase (GPx) activity in interleukin-1beta (IL-1β)-stimulated cells. Additionally, SeNPs down-regulated matrix metalloproteinase-13 (MMP-13) and thrombospondin motifs 5 (ADAMTS-5) expressions, while up-regulated type II collagen (COL-2) and aggrecan (ACAN) expressions stimulated by IL-1β. The findings also indicated that SeNPs may exert their effects through suppressing the NF-κB p65 and p38/MAPK pathways. In vivo experiments, the prevention of OA development brought on by SeNPs was demonstrated using a DMM model.

Discussion

Our results suggest that SeNPs may be a potential anti-inflammatory agent for treating OA.

Disrupting mechanical homeostasis promotes matrix metalloproteinase-13 mediated processing of neuron glial antigen 2 in mandibular condylar cartilage

Post-traumatic osteoarthritis in the temporomandibular joint (TMJ OA) is associated dysfunctional cellmatrix mediated signalling resulting from changes in the pericellular microenvironment after injury. Matrix metalloproteinase (MMP)-13 is a critical enzyme in biomineralisation and the progression of OA that can both degrade the extracellular matrix and modify extracellular receptors. This study focused on MMP-13 mediated changes in a transmembrane proteoglycan, Neuron Glial antigen 2 (NG2/CSPG4). NG2/CSPG4 is a receptor for type VI collagen and a known substrate for MMP-13. In healthy articular layer chondrocytes, NG2/CSPG4 is membrane bound but becomes internalised during TMJ OA. The objective of this study was to determine if MMP-13 contributed to the cleavage and internalisation of NG2/CSPG4 during mechanical loading and OA progression. Using preclinical and clinical samples, it was shown that MMP-13 was present in a spatiotemporally consistent pattern with NG2/CSPG4 internalisation during TMJ OA. In vitro, it was illustrated that inhibiting MMP-13 prevented retention of the NG2/CSPG4 ectodomain in the extracellular matrix. Inhibiting MMP-13 promoted the accumulation of membrane-associated NG2/CSPG4 but did not affect the formation of mechanical-loading dependent variant specific fragments of the ectodomain. MMP- 13 mediated cleavage of NG2/CSPG4 is necessary to initiate clathrin-mediated internalisation of the NG2/ CSPG4 intracellular domain following mechanical loading. This mechanically sensitive MMP-13-NG2/CSPG4 axis affected the expression of key mineralisation and OA genes including bone morphogenetic protein 2, and parathyroid hormone-related protein. Together, these findings implicated MMP-13 mediated cleavage of NG2/CSPG4 in the mechanical homeostasis of mandibular condylar cartilage during the progression of degenerative arthropathies such as OA.

BuShen JianGu Fang alleviates cartilage degeneration via regulating multiple genes and signaling pathways to activate NF-κB/Sox9 axis

BACKGROUND

Osteoarthritis (OA) is an inflammatory response in chondrocytes, causing extracellular matrix (ECM) degradation and cartilage destruction, affecting millions of people worldwide. Chinese herbal formulae BuShen JianGu Fang (BSJGF) has been clinically applied for treating OA-related syndromes, but the underlying mechanism still unclear.

METHODS

The components of BSJGF were analyzed by liquid chromatography-mass spectrometry (LC-MS). To make a traumatic OA model, the anterior cruciate ligament of 6-8-week-old male SD rats were cut and then the 0.4 mm metal was used to destroy the knee joint cartilage. OA severity was assessed by histological and Micro-CT. Mouse primary chondrocytes were utilized to investigate the mechanism of BSJGF alleviate osteoarthritis, which was examined by RNA-seq technology combined with a series of functional experiments.

RESULTS

A total 619 components were identified by LC-MS. In vivo, BSJGF treatment result in a higher articular cartilage tissue area compared to IL-1β group. Treatment also significantly increased Tb.Th, BV/TV and BMD of subchondral bone (SCB), which implied a protective effect on maintaining the stabilization of SCB microstructure. In vitro results indicated BSJGF promoted chondrocyte proliferation, increased the expression level of cartilage-specific genes (Sox9, Col2a1, Acan) and synthesized acidic polysaccharide, while inhibiting the release of catabolic enzymes and production of reactive oxygen species (ROS) induced by IL-1β. Transcriptome analysis showed that there were 1471 and 4904 differential genes between IL-1β group and blank group, BSJGF group and IL-1β group, respectively, including matrix synthesis related genes (Col2a1, H19, Acan etc.), inflammation related genes (Comp, Pcsk6, Fgfr3 etc.) and oxidative stress related genes (Gm26917, Bcat1, Sod1 etc.). Furthermore, KEGG analysis and validation results showed that BSJGF reduces OA-mediated inflammation and cartilage damaged due to modulation of NF-κB/Sox9 signaling axis.

CONCLUSION

The innovation of the present study was the elucidation of the alleviating cartilage degradation effect of BSJGF in vivo and in vitro and discovery of its mechanism through RNA-seq combined with function experiments, which provides a biological rationale for the clinical application of BSJGF for OA treatment.

Tenacissoside G alleviated osteoarthritis through the NF-κB pathway both in vitro and in vivo

BACKGROUND

Osteoarthritis (OA) is a degenerative joint disease characterized by the destruction of articular cartilage. Tenacissoside G is a flavonoid isolated from the dry roots of Marsdenia tenacissima (Roxb) and has been shown to have anti-inflammatory effects. However, there is no report on the protective effects of Tenacissoside G on OA.

OBJECTIVES

To identify the effects and mechanism of Tenacissoside G on OA.

METHODS

In vitro, primary mouse chondrocytes were induced with IL-1β to establish OA model. mRNA expression of MMP-13, MMP-3, TNF-α, IL-6 and iNOS, was detected by PCR. Protein expression of Collagen-II, MMP-13, p65, p-p65, and IκBα was detected by Western blot. Collagen-II in chondrocytes was also detected by immunofluorescence. In vivo, we established DMM OA mice model. The preventive effect of Tenacissoside G on OA was observed by micro-CT and histological analysis.

RESULTS

In vitro, Tenacissoside G significantly inhibited the expression of iNOS, TNF-α, IL-6, MMP-3, MMP-13 and the degradation of collagen-II, Tenacissoside G also significantly suppressed NF-κB activation in chondrocytes by IL-1β-stimulated. In vivo, we demonstrated Tenacissoside G can decrease articular cartilage damage and reduce OARSI score.

CONCLUSION

These results suggest that Tenacissoside G may serve as a potential drug for the prevention and treatment of OA.

Dihydrocaffeic acid improves IL-1β-induced inflammation and cartilage degradation via inhibiting NF-κB and MAPK signalling pathways

Aims

Osteoarthritis (OA) is a prevalent joint disorder with inflammatory response and cartilage deterioration as its main features. Dihydrocaffeic acid (DHCA), a bioactive component extracted from natural plant (gynura bicolor), has demonstrated anti-inflammatory properties in various diseases. We aimed to explore the chondroprotective effect of DHCA on OA and its potential mechanism.

Methods

In vitro, interleukin-1 beta (IL-1β) was used to establish the mice OA chondrocytes. Cell counting kit-8 evaluated chondrocyte viability. Western blotting analyzed the expression levels of collagen II, aggrecan, SOX9, inducible nitric oxide synthase (iNOS), IL-6, matrix metalloproteinases (MMPs: MMP1, MMP3, and MMP13), and signalling molecules associated with nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Immunofluorescence analysis assessed the expression of aggrecan, collagen II, MMP13, and p-P65. In vivo, a destabilized medial meniscus (DMM) surgery was used to induce mice OA knee joints. After injection of DHCA or a vehicle into the injured joints, histological staining gauged the severity of cartilage damage.

Results

DHCA prevented iNOS and IL-6 from being upregulated by IL-1β. Moreover, the IL-1β-induced upregulation of MMPs could be inhibited by DHCA. Additionally, the administration of DHCA counteracted IL-1β-induced downregulation of aggrecan, collagen II, and SOX9. DHCA protected articular cartilage by blocking the NF-κB and MAPK pathways. Furthermore, DHCA mitigated the destruction of articular cartilage in vivo.

Conclusion

We present evidence that DHCA alleviates inflammation and cartilage degradation in OA chondrocytes via suppressing the NF-κB and MAPK pathways, indicating that DHCA may be a potential agent for OA treatment.

Cite this article: Bone Joint Res 2023;12(4):259–273.