Role of Signal Transduction Pathways and Transcription Factors in Cartilage and Joint Diseases

Therapeutic potential of SOX family transcription factors in osteoarthritis

BACKGROUND

As the worldwide population ages, osteoarthritis has significantly increased. This musculoskeletal condition has become a pressing global health issue and thus, prevention and treatment of osteoarthritis have become the primary focus of domestic and international research. Scholarly investigations of the molecular mechanisms that are related to the occurrence and development of osteoarthritis have shed light on the pathological causes of this condition to a certain extent, providing a foundation for its prevention and treatment. However, further research is necessary to fully understand the critical role of the transcription factor SOX9 in chondrocyte differentiation and the development of osteoarthritis. As a result, there has been widespread interest in SOX transcription factors. While SOX9 has been utilized as a biomarker to indicate the occurrence and prognosis of osteoarthritis, investigations into other members of the SOX family and the development of targeted treatments around SOX9 are still required.

PURPOSE

This article considers the impact of the SOX protein on the development and inhibition of osteoarthritis and highlights the need for therapeutic approaches targeting SOX9, as supported by existing research.

RESULTS

SOX9 can contribute to the process of osteoarthritis through acetylation and ubiquitination modifications. The regulation of the WNT signalling pathway, Nrf2/ARE signalling pathway, NF-κB signalling pathway and SOX9 is implicated in the emergence of osteoarthritis. Non-coding RNA may play a role in the onset and progression of osteoarthritis by modulating various SOX family members, including SOX2, SOX4, SOX5, SOX6, SOX8, SOX9 and SOX11.

CONCLUSION

SOX9 has the capability of mitigating the onset and progression of osteoarthritis through means such as medication therapy, stem cell therapy, recombinant adeno-associated virus (rAAV) vector therapy, physical therapy and other approaches.

Mendelian randomization study on the causal relationships among fasting blood glucose, plasma proteins, and squamous cell lung cancer

BACKGROUND

Squamous cell lung cancer (SQCLC) represents the second most common subtype of lung cancer (LC) with characteristics of treatment resistance. Plasma proteins often influence levels of fasting blood glucose (FBG), consequently impacting LC. However, the precise role of FBG in this association remains unclear.

OBJECTIVE

To investigate the causal relationships of FBG with LC and its subtypes, plasma proteins, and SQCLC, as well as the mediating role of FBG.

METHODS

Mendelian randomization (MR) analysis was employed to assess the causal associations of FBG with LC and its subtypes, plasma proteins and SQCLC, and plasma proteins and FBG, using the two-step MR approach with the primary method being Inverse Variance Weighted (IVW). Protein-Protein Interaction (PPI) network was utilized to identify hub genes of plasma proteins causally linked to SQCLC.

RESULTS

FBG was a risk factor for SQCLC (OR: 1.376, 95% CI 1.017-1.862, P = 0.038) but had no significant causal associations with LC and other subtypes (P > 0.05). Furthermore, 54 plasma proteins had significant causal associations with SQCLC (P < 0.05). EEF2 K (OR: 1.111, 95% CI 1.015-1.216, P = 0.023) and SSR1 (OR: 0.546, 95% CI 0.487-0.613, P < 0.001) were identified as a risk and protective factor for FBG, respectively. Mediation analysis indicated a significant negative mediating effect of FBG in the causal relationship between SSR1 and SQCLC (B = - 0.193, 95% CI - 0.312-0.074, P = 0.001), with a mediation proportion of 44.4%.

CONCLUSION

Our study revealed FBG as a risk factor for SQCLC and demonstrated the mediating role of FBG in the causal association between SSR1 and SQCLC.

Layered Double Hydroxide Reshapes the Immune Microenvironment of Rheumatoid Arthritis through Small Mothers against Decapentaplegic 5

Persistent synovitis is a pivotal pathological feature of rheumatoid arthritis (RA). However, the current rheumatoid drugs are accompanied by severe side effects and have limited anti-inflammatory capabilities. In this work, we designed a bioactive material-folic acid modified layered double hydroxides (FA-LDH), aiming at targeting M1 macrophages and modulating macrophage repolarization. The in vitro experiment showed that FA-LDH mitigated the release of proinflammatory cytokines and promoted the expression of M2 macrophage markers. In terms of the action mechanism, FA-LDH modulated the nucleocytoplasmic transport of the small mothers against decapentaplegic 5 (Smad5) protein by adjusting the pH within the immune microenvironment. Subsequently, relying on the interaction between phospho-Smad5 (pSmad5) and p65, the nuclear factor kappa B signaling pathway was down-regulated through inhibiting nuclear transport of p65. Additionally, FA-LDH exhibited excellent targeting capability toward M1 macrophages and strong accumulation capacity in inflamed joints. In vivo experiment showed that FA-LDH could relieve swelling of limbs, reduce the infiltration of inflammatory cells, and protect joint cartilage and subchondral bone structure in collagen-induced arthritis mice. In summary, this work introduces a strategy for utilizing bioactive FA-LDH in the treatment of RA, highlighting the potential of FA-LDH to alleviate inflammation and reshape the immune microenvironment through the pSmad5/p65 axis.

T helper cell 17/regulatory T cell balance regulates ulcerative colitis and the therapeutic role of natural plant components: a review

Ulcerative colitis (UC) is a chronic relapsing inflammatory disease characterized by progressive mucosal damage. The incidence rate of UC is rising rapidly, which makes the burden of medical resources aggravated. In UC, due to various pathogenic factors such as mucosal immune system disorders, gene mutations and environmental factors disrupting the mucosal barrier function, the midgut pathogenic bacteria and exogenous antigens translocate into the lamina propria, thereby aggravating the inflammatory response and further damages the mucosal barrier. During the progression of UC, Th17 populations that cause inflammation generally increase, while Tregs that suppress Th17 activity decrease. Among them, Th17 mediates immune response, Treg mediates immunosuppression, and the coordinated balance of the two plays a key role in the inflammation and immune process of UC. Natural plant components can regulate biological processes such as immune inflammation from multiple levels of proinflammatory cytokines and signaling pathways. These characteristics have unique advantages and broad prospects in the treatment of UC. In immunomodulation, there is substantial clinical and experimental evidence for the modulatory role of natural plant products in restoring balance between Th17/Treg disturbances in UC. This review summarizes the previous studies on the regulation of Th17/Treg balance in UC by natural plant active ingredients, extracts, and traditional Chinese medicine prescriptions, and provides new evidence for the development and design of lead compounds and natural new drugs for the regulation of Th17/Treg balance in the future, and then provides ideas and evidence for future clinical intervention in the treatment of UC immune disorders and clinical trials.

Novel role of the SOX4/CSNK2A1 axis in regulating TOP2A phosphorylation in breast cancer progression

This study examines the critical role of DNA topoisomerase II alpha (TOP2A) phosphorylation in breast cancer progression, regulated by the SRY-box transcription factor 4 (SOX4)/Casein kinase II subunit alpha 1 (CSNK2A1) axis. Using integrated transcriptomic and proteomic analyses, data were sourced from the Clinical Proteomic Tumor Analysis Consortium (CPTAC) and The Cancer Genome Atlas (TCGA) databases. To explore the dataset, differential analysis, kinase-substrate enrichment analysis (KSEA), and weighted gene co-expression network analysis (WGCNA) were performed. Immune profiling, combined with survival analysis, revealed the prognosis linked to different immune profiles in breast cancer patients. In vitro experiments assessed the effect of SOX4 on CSNK2A1 promoter activity through real-time quantitative polymerase chain reaction (RT-qPCR), Western blot, dual-luciferase reporter assays, and chromatin immunoprecipitation (ChIP). The phosphorylation level of TOP2A was also measured. Cell proliferation, migration, and invasion were evaluated using cell counting kit-8 (CCK-8), colony formation, and Transwell assays. In vivo studies extended to mouse models, where the effect of SOX4 on CSNK2A1-TOP2A phosphorylation was analyzed about tumor growth and metastasis. The results showed that upregulation of SOX4 increases CSNK2A1 transcription, which in turn promotes TOP2A phosphorylation and accelerates breast cancer progression. The clinical analysis identified three immune profiles, with the intermediate profile associated with a poorer prognosis, possibly due to enhanced TOP2A phosphorylation mediated by SOX4/CSNK2A1. Silencing SOX4 significantly reduced cell proliferation, migration, invasion, and tumor growth in vivo by lowering CSNK2A1-TOP2A phosphorylation. These findings highlight the therapeutic potential of targeting the SOX4/CSNK2A1 axis in breast cancer and provide insight into its mechanism through TOP2A phosphorylation.

Gossypin Ameliorates Collagen-Induced Arthritic Rats by Inhibiting Angiogenesis, Inflammation and Oxidative Stress

BACKGROUND

Rheumatoid arthritis (RA) is a long-term inflammatory autoimmune disease that damages cartilage and synovial membranes while also affecting bones and joints. The aim of the current study was to investigate the antiarthritic effect of gossypin against collagen-induced arthritis (CIA) in rats.

METHODS

Intraperitoneal administration of Type II collagen (2 mg/mL) was used to induce arthritis in the rats, followed by oral administration of gossypin (5, 10 and 15 mg/kg) for 28 days. Various parameters were assessed, including body weight, paw swelling, arthritis score, organ weights, RF, haematological parameters, inflammatory markers, MMP levels, antioxidants, cytokines and nonhepatic and hepatic liver parameters. Additionally, the expression of various mRNAs was analysed.

RESULTS

Gossypin significantly (p < 0.001) altered the body weight, paw swelling, arthritis score and organ weights along with RF level. Gossypin treatment significantly (p < 0.001) altered the level of antioxidant and hepatic parameters; inflammatory cytokines; and inflammatory parameters such as PGE2, COX-2, NF-κB and VEGF, respectively. Gossypin also enhanced the level of HO-1 and Nrf2 and suppressed the level of MMP parameters such as MMP-2, MMP-3 and MMP-9. Gossypin also modified the mRNA expression of MMP-3, MMP-9, TRAP, RANK, Ctsk and RANKL, respectively.

CONCLUSION

Gossypin demonstrated antiarthritic effects against CIA in rats.

Chronic intermittent hypobaric hypoxia alleviates early-stage posttraumatic osteoarthritis via NF-κB/Nrf2 pathway in mice

BACKGROUND

Posttraumatic osteoarthritis (PTOA) is directly associated with early acute articular cartilage injury. Inhibition of cartilage destruction immediately following joint damage can effectively slow or prevent PTOA progression. Therefore, we sought to determine intervention targets and therapeutic strategies in the acute stage of cartilage injury. The benefits of chronic intermittent hypobaric hypoxia (CIHH) extend to various body tissues, but its impact on acute cartilage injury remains unclear. We selected PTOA initiation as the therapeutic window and administered CIHH treatment immediately following cartilage injury initiation to investigate its protective effect on cartilage and molecular mechanism changing with time-varying.

METHODS

The non-invasive PTOA mouse model was established by applying a single rapid specific impact force to the right knee's tibial plateau, initiating load-induced PTOA development, closely resembling the pathological changes in human diseases. Following loading, we inhibited cartilage destruction by treating mice immediately in a hypobaric chamber with a hypobaric hypoxia mimic at 5000 m altitude. Cohorts of mice subjected to distinct experimental conditions were monitored for 3, 7, 14 or 28 days. Safranin O-Fast Green staining, Immunohistochemistry, immunofluorescence, ELISA, and western blotting were performed to evaluate the therapeutic effects of CIHH on cartilage in vivo. The nuclear translocation of NF-κB p65 and Nrf2 were detected by immunofluorescence.

RESULTS

The results showed that inhibiting cartilage destruction using CIHH immediately following acute articular cartilage injury initiation delayed the progression of PTOA, decreased the Mankin score and suppressed the expression of proinflammatory factors, including iNOS, NO, TNF-α, and IL-1β. Meanwhile, immediate CIHH treatment reduced levels of the catabolic enzymes ADAMTS5 and MMP13 in the cartilage matrix, reversed degradation of Collagen II and COMP, and inhibited oxidative stress by decreasing ROS levels. Moreover, CIHH suppressed NF-κB signaling by activating the Nrf2 in vivo studies.

CONCLUSION

Our study demonstrated that immediate CIHH treatment following cartilage injury initiation can attenuate load-induced cartilage damage by activating Nrf2/HO-1 and inhibiting the NF-κB p65 signalling pathways to counteract oxidative stress and inflammatory reactions, enhance the metabolic balance of the cartilage matrix and delay cartilage degeneration. This treatment may represent a potential therapeutic strategy for limiting PTOA progression.

Regulation mechanism of endochondral ossification in Rana zhenhaiensis during metamorphosis based on histomorphology and transcriptome analyses

Endochondral ossification plays a crucial role in the limb development of amphibians. This study explored the ossification sequence in the hindlimb of Rana zhenhaiensis tadpoles and the correlation between thyroid hormones (THs) and endochondral ossification via histomorphology and transcriptional analyses. Our results suggest that ossification of the femur and tibiofibula was initiated during the period of high THs activity (metamorphosis climax). In addition, the results of differentially expressed gene analyses in the hindlimb and tail showed that systemic factors, transcription factors, and locally secreted factors interacted with each other during the metamorphosis climax to regulate the occurrence of endochondral ossification. These results will enrich the morphological data of anurans and provide scientific reference for the evolutionary history of vertebrates.

Mesenchymal stem cell-derived extracellular vesicles in joint diseases: Therapeutic effects and underlying mechanisms

Joint diseases greatly impact the daily lives and occupational functioning of patients globally. However, conventional treatments for joint diseases have several limitations, such as unsatisfatory efficacy and side effects, necessitating the exploration of more efficacious therapeutic strategies. Mesenchymal stem cell (MSC)-derived EVs (MSC-EVs) have demonstrated high therapeutic efficacyin tissue repair and regeneration, with low immunogenicity and tumorigenicity. Recent studies have reported that EVs-based therapy has considerable therapeutic effects against joint diseases, including osteoarthritis, tendon and ligament injuries, femoral head osteonecrosis, and rheumatoid arthritis. Herein, we review the therapeutic potential of various types of MSC-EVs in the aforementioned joint diseases, summarise the mechanisms underlying specific biological effects of MSC-EVs, and discuss future prospects for basic research on MSC-EV-based therapeutic modalities and their clinical translation. In general, this review provides an in-depth understanding of the therapeutic effects of MSC-EVs in joint diseases, as well as the underlying mechanisms, which may be beneficial to the clinical translation of MSC-EV-based treatment. The translational potential of this article: MSC-EV-based cell-free therapy can effectively promote regeneration and tissue repair. When used to treat joint diseases, MSC-EVs have demonstrated desirable therapeutic effects in preclinical research. This review may supplement further research on MSC-EV-based treatment of joint diseases and its clinical translation.

The Role of Neuromodulation and Potential Mechanism in Regulating Heterotopic Ossification

Heterotopic ossification (HO) is a pathological process characterized by the aberrant formation of bone in muscles and soft tissues. It is commonly triggered by traumatic brain injury, spinal cord injury, and burns. Despite a wide range of evidence underscoring the significance of neurogenic signals in proper bone remodeling, a clear understanding of HO induced by nerve injury remains rudimentary. Recent studies suggest that injury to the nervous system can activate various signaling pathways, such as TGF-β, leading to neurogenic HO through the release of neurotrophins. These pathophysiological changes lay a robust groundwork for the prevention and treatment of HO. In this review, we collected evidence to elucidate the mechanisms underlying the pathogenesis of HO related to nerve injury, aiming to enhance our understanding of how neurological repair processes can culminate in HO.

TMF inhibits extracellular matrix degradation by regulating the C/EBPβ/ADAMTS5 signaling pathway in osteoarthritis

Osteoarthritis (OA) is a chronic joint disease, characterized by degenerative destruction of articular cartilage. Chondrocytes, the unique cell type in cartilage, mediate the metabolism of extracellular matrix (ECM), which is mainly constituted by aggrecan and type II collagen. A disintegrin and metalloproteinase with thrombospondin 5 (ADAMTS5) is an aggrecanase responsible for the degradation of aggrecan in OA cartilage. CCAAT/enhancer binding protein β (C/EBPβ), a transcription factor in the C/EBP family, has been reported to mediate the expression of ADAMTS5. Our previous study showed that 5,7,3',4'-tetramethoxyflavone (TMF) could activate the Sirt1/FOXO3a signaling in OA chondrocytes. However, whether TMF protected against ECM degradation by down-regulating C/EBPβ expression was unknown. In this study, we found that aggrecan expression was down-regulated, and ADAMTS5 expression was up-regulated. Knockdown of C/EBPβ could up-regulate aggrecan expression and down-regulate ADAMTS5 expression in IL-1β-treated C28/I2 cells. TMF could compromise the effects of C/EBPβ on OA chondrocytes by activating the Sirt1/FOXO3a signaling. Conclusively, TMF exhibited protective activity against ECM degradation by mediating the Sirt1/FOXO3a/C/EBPβ pathway in OA chondrocytes.

C/EBPβ: The structure, regulation, and its roles in inflammation-related diseases

Inflammation, a mechanism of the human body, has been implicated in many diseases. Inflammatory responses include the release of inflammatory mediators by activating various signaling pathways. CCAAT/enhancer binding protein β (C/EBPβ), a transcription factor in the C/EBP family, contains the leucine zipper (bZIP) domain. The expression of C/EBPβ is mediated at the transcriptional and post-translational levels, such as phosphorylation, acetylation, methylation, and SUMOylation. C/EBPβ has been involved in inflammatory responses by mediating several signaling pathways, such as MAPK/NF-κB and IL-6/JAK/STAT3 pathways. C/EBPβ plays an important role in the pathological development of inflammation-related diseases, such as osteoarthritis, pneumonia, hepatitis, inflammatory bowel diseases, and rheumatoid arthritis. Here, we comprehensively discuss the structure and biological effects of C/EBPβ and its role in inflammatory diseases.

The molecular mechanisms of glycosaminoglycan biosynthesis regulating chondrogenesis and endochondral ossification

Disorders of chondrocyte differentiation and endochondral osteogenesis are major underlying factors in skeletal developmental disorders, including tibial dysplasia (TD), osteoarthritis (OA), chondrodysplasia (ACH), and multiple epiphyseal dysplasia (MED). Understanding the cellular and molecular pathogenesis of these disorders is crucial for addressing orthopedic diseases resulting from impaired glycosaminoglycan synthesis. Glycosaminoglycan is a broad term that refers to the glycan component of proteoglycan macromolecules. It is an essential component of the cartilage extracellular matrix and plays a vital role in various biological processes, including gene transcription, signal transduction, and chondrocyte differentiation. Recent studies have demonstrated that glycosaminoglycan biosynthesis plays a regulatory role in chondrocyte differentiation and endochondral osteogenesis by modulating various growth factors and signaling molecules. For instance, glycosaminoglycan is involved in mediating pathways such as Wnt, TGF-β, FGF, Ihh-PTHrP, and O-GlcNAc glycosylation, interacting with transcription factors SOX9, BMPs, TGF-β, and Runx2 to regulate chondrocyte differentiation and endochondral osteogenesis. To propose innovative approaches for addressing orthopedic diseases caused by impaired glycosaminoglycan biosynthesis, we conducted a comprehensive review of the molecular mechanisms underlying chondrocyte glycosaminoglycan biosynthesis, which regulates chondrocyte differentiation and endochondral osteogenesis. Our analysis considers the role of genes, glycoproteins, and associated signaling pathways during chondrogenesis and endochondral ossification.

IL-6, IL-1β and TNF-α regulation of the chondrocyte phenotype: a possible mechanism of haemophilic cartilage destruction

OBJECTIVE

Proinflammatory cytokines are considered to be one of the key causes of haemophilic cartilage destruction by inducing chondrocyte apoptosis and extracellular matrix degradation. However, few studies have focused on how proinflammatory cytokines regulate the phenotypic changes of chondrocytes, which may be an important factor in haemophilic cartilage degradation pathogenesis. More understanding is needed about the effect of proinflammatory cytokines on phenotypic changes of the chondrocyte. The objective of this study was to examine how IL-6, TNF-α and IL-1β regulate the chondrocyte phenotype, which may be an important factor in haemophilic cartilage degradation pathogenesis.

METHODS

HUM-iCell-s018 chondrocytes were treated with increasing concentrations of TNF-α, IL-6 or IL-1β (0, 1, 5, 10 ng/ml) for 24 h, then FGF23 and SOX9 expression was determined by qRT-PCR and WB, respectively.

RESULTS

We found that TNF-α, IL-6 and IL-1β induced FGF23 and suppressed SOX9 expression in chondrocytes in a dose-dependent manner. IL-1β had a stronger regulatory effect on FGF23, while TNF-α and IL-6 had stronger regulatory effects on SOX9.

CONCLUSIONS

These findings suggest that IL-6, IL-1β and TNF-α may be involved in haemophilic cartilage destruction pathogenesis by altering the chondrocyte phenotype through modulation of FGF23 and SOX9 gene expression.

FGF1 reduces cartilage injury in osteoarthritis via regulating AMPK/Nrf2 pathway

Osteoarthritis (OA) is a systemic joint degenerative disease involving a variety of cytokines and growth factors. In this study, we investigated the protective effect of fibroblast growth factor 1 (FGF1) knockdown on OA and its underlying mechanisms in vitro. In addition, we evaluated the effect of FGF1 knockout on the destabilization of the medial meniscus (DMM) and examined the anterior and posterior cruciate ligament model in vivo. FGF1 affects OA cartilage destruction by increasing the protein expression of Nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1), which is associated with the phosphorylation of AMPK and its substrates. Our study showed that FGF1 knockdown could reverse the oxidative damage associated with osteoarthritis. Nrf2 knockdown eliminated the antioxidant effect of FGF1 knockdown on chondrocytes. Furthermore, AMPK knockdown could stop the impact of FGF1 knockdown on osteoarthritis. These findings suggested that FGF1 knockdown could effectively prevent and reverse osteoarthritis by activating AMPK and Nrf2 in articular chondrocytes.

Fibroblast growth factor 10 delays the progression of osteoarthritis by attenuating synovial fibrosis via inhibition of IL-6/JAK2/STAT3 signaling in vivo and in vitro

Synovial fibrosis is a driver in the progression of osteoarthritis (OA). Fibroblast growth factor 10 (FGF10) has prominent anti-fibrotic effects in many diseases. Thus, we explored the anti-fibrosis effects of FGF10 in OA synovial tissue. In vitro, fibroblast-like synoviocytes (FLSs) were isolated from OA synovial tissue and stimulated with TGF-β to establish a cell model of fibrosis. After treatment with FGF10, we assessed the effects on FLS proliferation and migration using CCK-8, EdU, and scratch assays, and collagen production was observed using Sirius Red Stain. The JAK2/STAT3 pathway and expression of fibrotic markers were evaluated through western blotting (WB) and immunofluorescence (IF). In vivo, we treated mice with OA induced by surgical destabilization of the medial meniscus (DMM) with FGF10 and assessed the anti-OA effect using histological and immunohistochemical (IHC) staining of MMP13, and fibrosis was evaluated using HE and Masson's trichrome staining. The expression of IL-6/JAK2/STAT3 pathway components was determined using ELISA, WB, IHC, and IF. In vitro, FGF10 inhibited TGF-β-induced FLS proliferation and migration, decreased collagen deposition, and improved synovial fibrosis. Moreover, FGF10 mitigated synovial fibrosis and improved the symptoms of OA in DMM-induced OA mice. Overall, FGF10 had promising anti-fibrotic effects on FLSs and improved OA symptoms in mice. The IL-6/STAT3/JAK2 pathway plays key roles in the anti-fibrosis effect of FGF10. This study is the first to demonstrate that FGF10 inhibited synovial fibrosis and attenuated the progression of OA by inhibiting the IL-6/JAK2/STAT3 pathway.

New treatment for osteoarthr: pbad014itis: Gene therapy

Osteoarthritis is a complex degenerative disease that affects the entire joint tissue. Currently, non-surgical treatments for osteoarthritis focus on relieving pain. While end-stage osteoarthritis can be treated with arthroplasty, the health and financial costs associated with surgery have forced the search for alternative non-surgical treatments to delay the progression of osteoarthritis and promote cartilage repair. Unlike traditional treatment, the gene therapy approach allows for long-lasting expression of therapeutic proteins at specific sites. In this review, we summarize the history of gene therapy in osteoarthritis, outlining the common expression vectors (non-viral, viral), the genes delivered (transcription factors, growth factors, inflammation-associated cytokines, non-coding RNAs) and the mode of gene delivery (direct delivery, indirect delivery). We highlight the application and development prospects of the gene editing technology CRISPR/Cas9 in osteoarthritis. Finally, we identify the current problems and possible solutions in the clinical translation of gene therapy for osteoarthritis.

Mesenchymal cell-derived Wnt1 signaling regulates subchondral bone remodeling but has no effects on the development of growth plate or articular cartilage in mice

Chondrocyte differentiation is a principal progress in endochondral ossification and in the formation of secondary ossification center (SOC) during the long bone development. We have previously reported that targeted deletion of Wnt1 in mesenchymal progenitors (Wnt1_Prrx^-/-) leads to spontaneous fractures and severe osteopenia in mouse long bones, suggesting that Wnt1 is a key regulator of bone metabolism. However, the effect of Wnt1 on the regulation of cartilage development and chondrocyte differentiation remained unknown. In this study, WNT1 protein expression was observed in lateral superficial cartilage and growth plate pre-hypertrophic chondrocytes in mice. Wnt1 mRNA expression was detected in epiphyseal cartilage from E16.5 to 3 month-old mice. Detailed histological analyses revealed that the average thickness and chondrocyte density of proximal tibial articular cartilage and growth plate were unchanged between Wnt1_Prrx^-/- and control mice. However, μCT analysis of tibial epiphyses showed that the subchondral bone mass was reduced in Wnt1_Prrx^-/- mice compared to control mice, as demonstrated by decreased bone volume, trabecular number, trabecular thickness, and increased trabecular separation in Wnt1_Prrx^-/- mice. Mechanistically, histomorphometric analyses showed that the reduced subchondral bone mass in Wnt1_Prrx^-/- mice was due to impaired bone formation and enhanced bone resorption. In vitro, exogenous Wnt1 inhibited chondrogenesis and chondrocyte hypertrophy in both cell autonomous and juxtacrine manners, while matrix mineralization and the expression of Mmp13, Mmp9 and Opn were induced in a juxtacrine manner. Taken together, mesenchymal cell-derived Wnt1 is an important regulator of subchondral bone remodeling, although it has no effect on the regulation of growth plate or articular cartilage.

The activity of cytokines in dental pulp

BACKGROUND

After binding to their corresponding receptors, cytokines mediate a variety of biological activities. However, the activity of cytokines in dental pulp has not been studied in the single cell level.

METHODS

The cytokines activity of dental pulp was analyzed through CytoSig with the single cell sequencing data of dental pulp.

RESULTS

There are 43 cytokine signalling pathways analysed with CytoSig. The activity of TRAIL, NO, IL3, CXCL12 and IL1A was high in the majority of cells in the dental pulp. NO, TRAIL, CXCL12, BMP4 and BMP6 had higher activity in dental pulp stem cells, while CXCL12, BMP4, BMP6, BMP2 and IFN1 were the cytokines with high activity in pulp cells.

CONCLUSION

Our findings show the landscape of cytokine activity in dental pulp.

Activation and Function of NLRP3 Inflammasome in Bone and Joint-Related Diseases

Inflammation is a pivotal response to a variety of stimuli, and inflammatory molecules such as cytokines have central roles in the pathogenesis of various diseases, including bone and joint diseases. Proinflammatory cytokines are mainly produced by immune cells and mediate inflammatory and innate immune responses. Additionally, proinflammatory cytokines accelerate bone resorption and cartilage destruction, resulting in the destruction of bone and joint tissues. Thus, proinflammatory cytokines are involved in regulating the pathogenesis of bone and joint diseases. Interleukin (IL)-1 is a representative inflammatory cytokine that strongly promotes bone and cartilage destruction, and elucidating the regulation of IL-1 will advance our understanding of the onset and progression of bone and joint diseases. IL-1 has two isoforms, IL-1α and IL-1β. Both isoforms signal through the same IL-1 receptor type 1, but the activation mechanisms are completely different. In particular, IL-1β is tightly regulated by protein complexes termed inflammasomes. Recent research using innovative technologies has led to a series of discoveries about inflammasomes. This review highlights the current understanding of the activation and function of the NLRP3 (NOD-like receptor family, pyrin domain-containing 3) inflammasome in bone and joint diseases.

RNA-seq based integrative analysis of potential crucial genes and pathways associated with patellar instability

Patellar instability (PI) is a common knee injury in adolescents, but the crucial biomarkers and molecular mechanisms associated with it remain unclear. We established a PI mouse model and investigated PI-related changes in gene expression by RNA sequencing (RNA-seq). Differentially expressed gene (DEG) analysis and enrichment analysis were performed to identify crucial genes and pathways associated with PI. Subsequently, a protein-protein interaction, DEG-miRNA, DEG-transcription factors, and DEG-drug interaction networks were constructed to reveal hub genes, molecular mechanism, and potential drugs for PI. Finally, the reliability of the sequencing results was confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry. Upon comparison with the control group, 69 genes were differently expressed in PI, including 17 upregulated and 52 downregulated ones. The DEGs were significantly enriched in Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway and immune responses. The protein–protein interaction network identified ten PI-related hub genes, all of which are involved in the JAK/STAT signaling pathway or inflammation-related pathways. DEG-miRNA and DEG-transcription factor networks offered new insights for regulating DEGs post-transcriptionally. We also determined potential therapeutic drugs or molecular compounds that could restore dysregulated expression of DEGs via the DGIdb database. RT-qPCR results were consistent with the RNA-seq, confirming the reliability of the sequencing data. Immunohistochemistry results suggested that JAK1 and STAT3 expression was increased in PI. Our study explored the potential molecular mechanisms in PI, provided promising biomarkers and suggested a molecular basis for therapeutic targets for this condition.

Accelerated Discovery of the Polymer Blends for Cartilage Repair through Data-Mining Tools and Machine-Learning Algorithm

In designing successful cartilage substitutes, the selection of scaffold materials plays a central role, among several other important factors. In an empirical approach, the selection of the most appropriate polymer(s) for cartilage repair is an expensive and time-consuming affair, as traditionally it requires numerous trials. Moreover, it is humanly impossible to go through the huge library of literature available on the potential polymer(s) and to correlate the physical, mechanical, and biological properties that might be suitable for cartilage tissue engineering. Hence, the objective of this study is to implement an inverse design approach to predict the best polymer(s)/blend(s) for cartilage repair by using a machine-learning algorithm (i.e., multinomial logistic regression (MNLR)). Initially, a systematic bibliometric analysis on cartilage repair has been performed by using the bibliometrix package in the R program. Then, the database was created by extracting the mechanical properties of the most frequently used polymers/blends from the PoLyInfo library by using data-mining tools. Then, an MNLR algorithm was run by using the mechanical properties of the polymers, which are similar to the cartilages, as the input and the polymer(s)/blends as the predicted output. The MNLR algorithm used in this study predicts polyethylene/polyethylene-graftpoly(maleic anhydride) blend as the best candidate for cartilage repair.

Possible Repositioning of an Oral Anti-Osteoporotic Drug, Ipriflavone, for Treatment of Inflammatory Arthritis via Inhibitory Activity of KIAA1199, a Novel Potent Hyaluronidase

KIAA1199 has a strong hyaluronidase activity in inflammatory arthritis. This study aimed to identify a drug that could reduce KIAA1199 activity and clarify its effects on inflammatory arthritis. Rat chondrosarcoma (RCS) cells were strongly stained with Alcian blue (AB). Its stainability was reduced in RCS cells, which were over-expressed with the KIAA1199 gene (RCS-KIAA). We screened the drugs that restore the AB stainability in RCS-KIAA. The effects of the drug were evaluated by particle exclusion assay, HA ELISA, RT-PCR, and Western blotting. We further evaluated the HA accumulation and the MMP1 and three expressions in fibroblast-like synoviocytes (FLS). In vivo, the effects of the drug on symptoms and serum concentration of HA in a collagen-induced arthritis mouse were evaluated. Ipriflavone was identified to restore AB stainability at 23%. Extracellular matrix formation was significantly increased in a dose-dependent manner (p = 0.006). Ipriflavone increased the HA accumulation and suppressed the MMP1 and MMP3 expression on TNF-α stimulated FLS. In vivo, Ipriflavone significantly improved the symptoms and reduced the serum concentrations of HA. Conclusions: We identified Ipriflavone, which has inhibitory effects on KIAA1199 activity. Ipriflavone may be a therapeutic candidate based on its reduction of KIAA1199 activity in inflammatory arthritis.

miR9 inhibits 6-mer HA-induced cytokine production and apoptosis in human chondrocytes by reducing NF-kB activation

The present study aimed to investigate the expression of miR9 and its correlation with cytokines, proteolytic enzymes and apoptosis in an experimental model of 6-mer HA induced inflammation in human chondrocytes. Human articular chondrocytes, transfected with a miR-9 mimic and miR-9 inhibitor, were stimulated with 6-mer HA in presence/absence of a specific NF-kB inhibitor. 6-mer HA induced a significant increase of TLR-4, CD44, IL-8, IL-18, MMP-9, ADAMTS-5, BAX and BCL-2 mRNAs expression and the related proteins, as well as NF-kB activation, associated with a significant up regulation of miR-9. In chondrocytes transfected with the miR-9 mimic before 6-mer HA treatment we found a decrease of such inflammatory cytokines, metalloproteases and pro-apoptotic molecules, while we found them increased in chondrocytes transfected with the miR9 inhibitor before 6-mer HA stimulation. The activities of TLR-4 and CD44, up regulated by 6-mer HA, were not modified by miR9 mimic/inhibitor, while the NF-kB activation was significantly affected. We suggested that the up regulation of miR9, induced by 6-mer HA, could be a cellular attempt to limit cell damage during inflammation.

Shikonin Derivatives Inhibit Inflammation Processes and Modulate MAPK Signaling in Human Healthy and Osteoarthritis Chondrocytes

Osteoarthritis (OA) is the most common joint disorder and is characterized by the degeneration of articular cartilage. To develop new therapeutic approaches, we investigated the effect of shikonin derivatives on inflammation, MMP expression, and the regulation of MAPK signaling in human healthy (HC) and OA chondrocytes (pCH-OA). Viability was analyzed using the CellTiter-Glo^® Assay. Inflammatory processes were investigated using a proteome profiler™ assay. Furthermore, we analyzed the effects of the shikonin derivatives by protein expression analysis of the phosphorylation pattern and the corresponding downstream gene regulation using RT-qPCR. Both HC and pCH-OA showed a dose-dependent decrease in viability after treatment. The strongest effects were found for shikonin with IC₅₀ values of 1.2 ± 0.1 µM. Shikonin counteracts the inflammatory response by massively reducing the expression of the pro-inflammatory mediators. The phosphorylation level of ERK changed slightly. pJNK and pp38 showed a significant increase, and the downstream targets c/EBPs and MEF2c may play a role in the cartilage homeostasis. STAT3 phosphorylation decreased significantly and has a chondroprotective function through the regulation of cyclin D1 and Sox9. Our results demonstrate for the first time that shikonin derivatives have extensive effects on the inflammatory processes, MAPKs, and IL6/STAT3 downstream regulation in healthy and OA chondrocytes.

Hedgehog signalling in bone and osteoarthritis: the role of Smoothened and cholesterol

Hedgehog signalling is essential for development, crucial for normal anatomical arrangement and activated during tissue damage repair. Dysregulation of hedgehog signalling is associated with cancer, developmental disorders and other diseases including osteoarthritis (OA). The hedgehog gene was first discovered in Drosophila melanogaster, and the pathway is evolutionarily conserved in most animals. Although there are several hedgehog ligands with different protein expression patterns, they share a common plasma membrane receptor, Patched1 and hedgehog signalling pathway activation is transduced through the G-protein-coupled receptor-like protein Smoothened (SMO) and downstream effectors. Functional assays revealed that activation of SMO is dependent on sterol binding, and cholesterol was observed bound to SMO in crystallography experiments. In vertebrates, hedgehog signalling coordinates endochondral ossification and balances osteoblast and osteoclast activation to maintain homeostasis. A recently discovered mutation of SMO in humans (SMO^R173C ) is predicted to alter cholesterol binding and is associated with a higher risk of hip OA. Functional studies in mice and human tissue analysis provide evidence that hedgehog signalling is pathologically activated in chondrocytes of osteoarthritic cartilage.

Inflammation and Bone Metabolism in Rheumatoid Arthritis: Molecular Mechanisms of Joint Destruction and Pharmacological Treatments

Rheumatoid arthritis (RA) is an inflammatory disease characterized by a variety of symptoms and pathologies often presenting with polyarthritis. The primary symptom in the initial stage is joint swelling due to synovitis. With disease progression, cartilage and bone are affected to cause joint deformities. Advanced osteoarticular destruction and deformation can cause irreversible physical disabilities. Physical disabilities not only deteriorate patients' quality of life but also have substantial medical economic effects on society. Therefore, prevention of the progression of osteoarticular destruction and deformation is an important task. Recent studies have progressively improved our understanding of the molecular mechanism by which synovitis caused by immune disorders results in activation of osteoclasts; activated osteoclasts in turn cause bone destruction and para-articular osteoporosis. In this paper, we review the mechanisms of bone metabolism under physiological and RA conditions, and we describe the effects of therapeutic intervention against RA on bone.

Effect of Swell1 on regulating chondrocyte hypertrophy during the condylar osteochondral development process in mice

Chondrocyte hypertrophy is a significant factor in cartilage development, yet the molecular mechanism for cell volume expand during the process is remains unclear. In the present study, the relationship between Swell1, a cell volume regulated anion channel, and chondrocyte hypertrophy was explored. The results reveal that the spatiotemporal expression of Swell1 was similar with the development process of hypertrophic chondrocytes in condyles. Through Col10a1 mediated knock out of Swell1 in hypertrophy chondrocytes, we found that there are less obvious boundary between different condylar cartilage layers in which increased hypertrophic chondrocytes were scattered in all three cartilage layers. The cortical bone mass and bone mineral density in the subchondral bone significantly increased. Additionally, knock out of Swell1 could increase the expression of OCN in the femur condyle. Based on the aforementioned findings, a conclusion could be drawn that Swell1 is a significant factor in chondrocyte hypertrophy during the condylar osteochondral development process, and there was some difference between the mandibular and femur condyles, which will provide some new clues for understanding the development of cartilage and related diseases.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Anti-inflammatory and osteoprotective effects of Chikusetsusaponin Ⅳa on rheumatoid arthritis via the JAK/STAT signaling pathway

BACKGROUND

Rheumatoid arthritis (RA) is a common autoimmune disease, for which no economical and safe target drug treatment is available. Chikusetsusaponin Ⅳa (CS-IVa), an active compound in Panax japonicus C.A. Mey, has a good anti-inflammatory effect, but whether this compound can serve as a targeted drug for RA and the corresponding therapeutic mechanism remain unclear.

PURPOSE

To investigate the anti-inflammatory and bone-protecting effects of CS-IVa on RA and the possible corresponding mechanisms of action.

METHODS

Biomarkers and underlying pathological mechanisms were examined by performing a bioinformatics analysis of RA synovial gene expression data profiles, and the feasibility of CS-IVa treatment for RA was predicted using molecular docking and molecular dynamics simulation techniques. Histomorphological and molecular biology techniques were used to verify the feasibility and molecular mechanism of CS-IVa treatment for RA in vivo using a collagen-induced arthritis (CIA) model.

RESULTS

CS-IVa alleviated symptoms and reduced the immune organ index, arthritis index, hind paw thickness, and number of swollen joints in the foot for CIA mice. Bioinformatics analysis suggested that interferon-gamma (IFN-γ), interleukin-1 β (IL-1β), and the Janus kinase/signal transduction and activator of transcription (JAK/STAT) pathway played important roles in the pathogenesis of RA. The results of molecular docking and molecular dynamics simulations showed that CS-IVa bound effectively to IFN-γ and IL-1β and that the combined pose has good stability and flexibility. The histomorphological results showed that CS-IVa reduced joint histopathology scores, OARSI scores, and TRAP-positive cell counts. Molecular biology analysis indicated that CS-IVa reduced the concentration of inflammatory factors in the peripheral serum of CIA mice and suppressed the mRNA expression of these factors in the spleen in a dose-dependent manner. The protein expression level of the JAK/STAT pathway was also inhibited by CS-IVa.

CONCLUSION

The results of the current study demonstrate a novel inhibitory effect of CS-IVa on inflammation and bone destruction in CIA mice, and the mechanism may be related to the JAK/STAT signaling pathway, which provides new insights into the development of CS-IVa as a therapeutic agent for RA.

Blockade of Fgfr1 with PD166866 Protects Cartilage from the Catabolic Effects Induced by Interleukin-1β: A Genome-Wide Expression Profiles Analysis

OBJECTIVE

Previously we showed that genetic deletion of Fgfr1 in chondrocytes protected mice from progression of osteoarthritis (OA). The aim of this study is to evaluate the effect of PD166866, a potent selective inhibitor of Fgfr1, on cartilage degeneration induced by interleukin-1β (IL-1β) and to clarify underlying global gene expression pattern.

DESIGN

Cartilage explants and primary rat chondrocytes were stimulated with IL-1β to establish an inflammatory OA in vitro model. The effects of PD166866 were determined by measuring the release of glycosaminoglycans (GAG) in cartilage explants and primary rat chondrocytes, and the underlying molecular mechanism was analyzed by microarray and RT-PCR analysis in primary chondrocytes.

RESULTS

In cartilage explants, PD166866 significantly counteracts IL-β stimulated GAG release. In addition, PD166866 impede IL-1β-stimulated nuclear translocation of p65 in rat chondrocytes. Based on microarray analysis, a total of 67 and 132 genes with more than 1.5-fold changes were identified in IL-1β-treated versus control and PD166866 cotreatment versus IL-1β treatment alone, respectively. Only 19 thereof were coregulated by IL-1β and PD166866 simultaneously. GO and KEGG pathway analysis showed that some pathways, including "cytokine-cytokine receptor interaction," "chemokine signaling pathway," and "complement and coagulation cascades," as well as some key genes like chemokines, complement, and matrix metalloproteinases may relevant for therapeutic application of Fgfr1 blockade in IL-1β-stimulated chondrocytes.

CONCLUSION

Our results clearly demonstrated that blockade of Fgfr1 with PD166866 could effectively suppress the catabolic effects induced by IL-1β, and elucidated whole genomic targets of Fgfr1 inhibition responsible for the therapeutic effects of Fgfr1 blockade against inflammatory OA.

Weighted gene co-expression network analysis reveals specific modules and hub genes related to immune infiltration of osteoarthritis

Background

The incidence of osteoarthritis (OA), a chronic degenerative disease, is increasing every year. There is no effective clinical treatment for OA and the pathological mechanism remains unclear. Early diagnosis is an effective strategy to control the progress of OA. In this study, we aimed to identify potential early diagnostic biomarkers.

Methods

We downloaded the gene expression profile dataset, GSE51588 and GSE55235, from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) public database. The differentially expressed genes (DEGs) were screened out using the “limma” R package. Weighted gene co-expression network analysis (WGCNA) was utilized to build the co-expression network between the normal and OA samples. A Venn diagram was constructed to detect the hub genes. Potential molecular mechanisms and signaling pathways were enriched by gene set variation analysis (GSVA). Single sample gene set enrichment analysis (ssGSEA) was used to identify the immune infiltration of OA.

Results

We screened out three hub genes based on WGCNA and DEGs in this study. GSVA results showed that nuclear factor interleukin-3 (NFIL3) was related to tumor necrosis factor alpha (TNF-α) signaling via nuclear factor kappa-B (NF-κB), the reactive oxygen species pathway, and myelocytomatosis (MYC) targets v2. Highly-expressed ADM (adrenomedullin) pathways included TNF-α signaling via NF-κB, the reactive oxygen species pathway, and ultraviolet (UV) response up. OGN (osteoglycin)-enriched pathways included epithelial mesenchymal transition, coagulation, and peroxisome.

Conclusions

We identified three hub genes (NFIL3, ADM, and OGN) that were correlated to the development and progression of OA, which may provide new biomarkers for early diagnosis.

ROS/TGF-β signal mediated accumulation of SOX4 in OA-FLS promotes cell senescence

Osteoarthritis (OA) is an age-related disease, which is mainly treated with oral, topical, and/or intra-articular options to relieve symptoms and lack of specific treatment measures. Fibroblasts (FLS) are crucial cells in joint inflammation and destruction. Cellular senescence plays an important role during OA pathogenesis and senescent cells exhibit cell-cycle arrest and senescence-associated secretory phenotype (SASP). SRY-related HMG-box 4 (SOX4) is a contributing factor during many developmental processes and is elevated in inflamed synovium than in noninflamed synovium from arthritis patients. This study was designed to investigate whether SOX4 participate in the pathogenesis of OA by affecting FLS senescence and explore the internal mechanism. Firstly, we found that FLS cells exhibited more cellular senescence in OA compared with control group. We also verified the role of reactive oxygen species (ROS)/TGF-β signal in the induction of OA-FLS senescence. During the exploration of SOX4 in cell senescence, the results indicated that SOX4 activation promotes cell senescence and SASP of OA-FLS. Apart from that, we also confirmed that SOX4, regulated by ROS/TGF-β signal, was critical transcription factor associated with OA-FLS senescence. Therefore, SOX4 is likely to be a novel therapeutic target and early diagnostic marker during OA pathogenesis.

Inhibitors of Human Divalent Metal Transporters DMT1 (SLC11A2) and ZIP8 (SLC39A8) from a GDB-17 Fragment Library

Solute carrier proteins (SLCs) are membrane proteins controlling fluxes across biological membranes and represent an emerging class of drug targets. Here we searched for inhibitors of divalent metal transporters in a library of 1,676 commercially available 3D-shaped fragment-like molecules from the generated database GDB-17, which lists all possible organic molecules up to 17 atoms of C, N, O, S and halogen following simple criteria for chemical stability and synthetic feasibility. While screening against DMT1 (SLC11A2), an iron transporter associated with hemochromatosis and for which only very few inhibitors are known, only yielded two weak inhibitors, our approach led to the discovery of the first inhibitor of ZIP8 (SLC39A8), a zinc transporter associated with manganese homeostasis and osteoarthritis but with no previously reported pharmacology, demonstrating that this target is druggable.

Single-Cell Integration Analysis of Heterotopic Ossification and Fibrocartilage Developmental Lineage: Endoplasmic Reticulum Stress Effector Xbp1 Transcriptionally Regulates the Notch Signaling Pathway to Mediate Fibrocartilage Differentiation

INTRODUCTION

Regeneration of fibrochondrocytes is essential for the healing of the tendon-bone interface (TBI), which is similar to the formation of neurogenic heterotopic ossification (HO). Through single-cell integrative analysis, this study explored the homogeneity of HO cells and fibrochondrocytes.

METHODS

This study integrated six datasets, namely, GSE94683, GSE144306, GSE168153, GSE138515, GSE102929, and GSE110993. The differentiation trajectory and key transcription factors (TFs) for HO occurrence were systematically analyzed by integrating single-cell RNA (scRNA) sequencing, bulk RNA sequencing, and assay of transposase accessible chromatin seq. The differential expression and enrichment pathways of TFs in heterotopically ossified tissues were identified.

RESULTS

HO that mimicked pathological cells was classified into HO1 and HO2 cell subsets. Results of the pseudo-temporal sequence analysis suggested that HO2 is a differentiated precursor cell of HO1. The analysis of integrated scRNA data revealed that ectopically ossified cells have similar transcriptional characteristics to cells in the fibrocartilaginous zone of tendons. The modified SCENIC method was used to identify specific transcriptional regulators associated with ectopic ossification. Xbp1 was defined as a common key transcriptional regulator of ectopically ossified tissues and the fibrocartilaginous zone of tendons. Subsequently, the CellPhoneDB database was completed for the cellular ligand-receptor analysis. With further pathway screening, this study is the first to propose that Xbp1 may upregulate the Notch signaling pathway through Jag1 transcription. Twenty-four microRNAs were screened and were found to be potentially associated with upregulation of XBP1 expression after acute ischemic stroke.

CONCLUSION

A systematic analysis of the differentiation landscape and cellular homogeneity facilitated a molecular understanding of the phenotypic similarities between cells in the fibrocartilaginous region of tendon and HO cells. Furthermore, by identifying Xbp1 as a hub regulator and by conducting a ligand-receptor analysis, we propose a potential Xbp1/Jag1/Notch signaling pathway.

Functional and regulatory aspects of oxidative stress response in X monosomy

The partial/complete loss of one X chromosome in a human female leads to Turner syndrome (TS). TS individuals display a range of phenotypes including short stature, osteoporosis, ovarian malfunction, diabetes, and thyroid dysfunction. Epigenetic factors and regulatory networks are distinctly different in X monosomy (45, X). In a lifetime, an individual is exposed to a variety of stress conditions. To study whether X monosomy cells display a differential response upon exposure to mild stress as compared to normal 46, XX cells and whether this may contribute to various co-morbidities in aneuploid individuals, we have carried out a transcriptomic analysis of human fibroblasts 45, X and 46, XX after exposure to mild oxidative stress. Under these conditions, over 350 transcripts were seen to be differentially expressed in 45, X and 46, XX cells. Pathways associated with oxidative stress were differentially expressed highlighting the differential regulation of genes and associated phenotypes. It could be seen that X monosomy cells are more susceptible to oxidative stress as compared to normal cells and have altered molecular pathways both in normal conditions and also upon exposure to mild oxidative stress. To explore this aspect in detail, we have mapped the expressions of transcription factors (TFs) in 45, X and 46, XX cells. The network of transcription activating factors is differentially regulated in 45, X and 46, XX cells under stress exposure. It is tempting to speculate that the altered ability of 45, X (Turner) cells to respond to stress may play a significant role in the physiological function and altered phenotypes in Turner syndrome.

Functional Duality of Chondrocyte Hypertrophy and Biomedical Application Trends in Osteoarthritis

Chondrocyte hypertrophy is one of the key indicators in the progression of osteoarthritis (OA). However, compared with other OA indications, such as cartilage collapse, sclerosis, inflammation, and protease activation, the mechanisms by which chondrocyte hypertrophy contributes to OA remain elusive. As the pathological processes in the OA cartilage microenvironment, such as the alterations in the extracellular matrix, are initiated and dictated by the physiological state of the chondrocytes, in-depth knowledge of chondrocyte hypertrophy is necessary to enhance our understanding of the disease pathology and develop therapeutic agents. Chondrocyte hypertrophy is a factor that induces OA progression; it is also a crucial factor in the endochondral ossification. This review elaborates on this dual functionality of chondrocyte hypertrophy in OA progression and endochondral ossification through a description of the characteristics of various genes and signaling, their mechanism, and their distinguishable physiological effects. Chondrocyte hypertrophy in OA progression leads to a decrease in chondrogenic genes and destruction of cartilage tissue. However, in endochondral ossification, it represents an intermediate stage at the process of differentiation of chondrocytes into osteogenic cells. In addition, this review describes the current therapeutic strategies and their mechanisms, involving genes, proteins, cytokines, small molecules, three-dimensional environments, or exosomes, against the OA induced by chondrocyte hypertrophy. Finally, this review proposes that the contrasting roles of chondrocyte hypertrophy are essential for both OA progression and endochondral ossification, and that this cellular process may be targeted to develop OA therapeutics.

Kartogenin prevents cartilage degradation and alleviates osteoarthritis progression in mice via the miR-146a/NRF2 axis

Osteoarthritis (OA) is a common articular degenerative disease characterized by loss of cartilage matrix and subchondral bone sclerosis. Kartogenin (KGN) has been reported to improve chondrogenic differentiation of mesenchymal stem cells. However, the therapeutic effect of KGN on OA-induced cartilage degeneration was still unclear. This study aimed to explore the protective effects and underlying mechanisms of KGN on articular cartilage degradation using mice with post-traumatic OA. To mimic the in vivo arthritic environment, in vitro cultured chondrocytes were exposed to interleukin-1β (IL-1β). We found that KGN barely affected the cell proliferation of chondrocytes; however, KGN significantly enhanced the synthesis of cartilage matrix components such as type II collagen and aggrecan in a dose-dependent manner. Meanwhile, KGN markedly suppressed the expression of matrix degradation enzymes such as MMP13 and ADAMTS5. In vivo experiments showed that intra-articular administration of KGN ameliorated cartilage degeneration and inhibited subchondral bone sclerosis in an experimental OA mouse model. Molecular biology experiments revealed that KGN modulated intracellular reactive oxygen species in IL-1β-stimulated chondrocytes by up-regulating nuclear factor erythroid 2-related factor 2 (NRF2), while barely affecting its mRNA expression. Microarray analysis further revealed that IL-1β significantly up-regulated miR-146a that played a critical role in regulating the protein levels of NRF2. KGN treatment showed a strong inhibitory effect on the expression of miR-146a in IL-1β-stimulated chondrocytes. Over-expression of miR-146a abolished the anti-arthritic effects of KGN not only by down-regulating the protein levels of NRF2 but also by up-regulating the expression of matrix degradation enzymes. Our findings demonstrate, for the first time, that KGN exerts anti-arthritic effects via activation of the miR-146a-NRF2 axis and KGN is a promising heterocyclic molecule to prevent OA-induced cartilage degeneration.

Xanthohumol Attenuated Inflammation and ECM Degradation by Mediating HO-1/C/EBPβ Pathway in Osteoarthritis Chondrocytes

Osteoarthritis (OA) is the most frequent and disabling disease in developed countries. The progressive degeneration of articular cartilage characterized as thinner and erosive. Inflammation is well-known to be involved in OA development. However, there are no effective therapeutic strategies to cure it. Xanthohumol (XH) is a natural prenylflavonoid isolated from hops and beer. The protective activity of XH against OA chondrocytes inflammation and ECM degradation is unclear. In this article, we found that XH significantly inhibited inflammatory responses, attenuated catabolic enzymes expression, and ameliorated ECM degradation, as showed by decreased production of NO, PGE2, TNFα, and IL-6, decreased expression of MMP-3/-13 and ADAMTS-4/-5, and increased expression of collagen-II and aggrecan. In addition, XH activated HO-1 signaling and attenuated IL-1β-induced C/EBPβ. XH promoted the interaction between HO-1 and C/EBPβ, inhibiting the nuclear translocation of C/EBPβ. HO-1 knockdown could abrogate the protective effects of XH in IL-1β-treated chondrocytes. Collectively, XH attenuated inflammatory responses and ECM degradation by mediating HO-1 and C/EBPβ signaling pathways in osteoarthritis chondrocytes.

Hydrogen Sulfide: a Novel Immunoinflammatory Regulator in Rheumatoid Arthritis

Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has been shown to have vasodilative, anti-oxidative, anti-inflammatory, and cytoprotective activities. Increasing evidence also indicates that H₂S can suppress the production of inflammatory mediators by immune cells, for example, T cells and macrophages. Inflammation is closely related to an immune response in several diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE), and cancer. Considering these biological effects of H₂S, a potential role in the treatment of immune-related RA is being exploited. In the present review, we will provide an overview of the therapeutic potential of H₂S in RA treatment.

Circ_DHRS3 positively regulates GREM1 expression by competitively targeting miR-183-5p to modulate IL-1β-administered chondrocyte proliferation, apoptosis and ECM degradation

BACKGROUND

Osteoarthritis (OA) is a chronic inflammatory disease caused by degenerative changes of articular cartilage, involving in the expression changes of special circular RNAs (circRNAs). This study aimed to explore the role of circ_DHRS3 in OA cell models and provide a potential mechanism.

METHODS

OA cell models were constructed using human chondrocytes with Interleukin-1 beta (IL-1β) treatment. The expression of circ_DHRS3, microRNA (miR)-183-5p and Gremlin 1 (GREM1) mRNA was detected using real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation was identified using 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide (MTT) assay. Cell apoptosis was investigated using flow cytometry assay. The protein levels of proliferation- and apoptosis-related proteins were quantified by western blot. The levels of extracellular matrix (ECM)-associated proteins were quantified by western blot to assess ECM degradation. The relationship between miR-183-5p and circ_DHRS3 or GREM1 was predicted and then verified by dual-luciferase reporter assay.

RESULTS

Circ_DHRS3 expression was elevated in OA cartilage tissues and IL-1β-treated chondrocytes. Circ_DHRS3 was resistant to RNase R and Actinomycin D. Circ_DHRS3 knockdown promoted chondrocyte proliferation inhibited by IL-1β, and alleviated IL-1β-induced apoptosis and ECM degradation, which were reversed by the inhibition of miR-183-5p, a target of circ_DHRS3. MiR-183-5p restoration also enhanced IL-1β-blocked cell proliferation, and relieved IL-1β-induced cell apoptosis and ECM degradation, while GREM1 (a target of miR-183-5p) overexpression abolished the effects of miR-183-5p restoration. Moreover, circ_DHRS3 regulated GREM1 expression by targeting miR-183-5p.

CONCLUSION

Circ_DHRS3 mediated IL-1β-administered chondrocyte proliferation, apoptosis and ECM degradation by positively regulating GREM1 expression via competitively targeting miR-183-5p.

INSR mediated by transcription factor KLF4 and DNA methylation ameliorates osteoarthritis progression via inactivation of JAK2/STAT3 signaling pathway

OBJECTIVE

To probe into the role and regulatory mechanisms of INSR in pathogenesis of osteoarthritis (OA).

METHODS

KLF4 and INSR expression was detected in cartilage tissues of 40 OA patients and 10 controls using RT-qPCR. IL-1β-induced OA chondrocytes and anterior cruciate ligament transection (ACLT)-induced OA models were respectively constructed. After overexpressing or silencing KLF4 or INSR, flow cytometry assay was utilized to detect chondrocyte apoptosis. Furthermore, JAK2/STAT3, cartilage markers and OA-related markers were examined by western blot. Dual luciferase report and CHIP assay were carried out to verify the interactions between KLF4 and INSR, followed by functional gain and loss assay. INSR promoter methylation was assessed by MS-PCR.

RESULTS

Both KLF4 and INSR were down-regulated both in OA chondrocytes and cartilage tissues. Knockdown of KLF4 or INSR accelerated apoptosis of IL-1β-induced OA chondrocytes. However, overexpression of KLF4 or INSR ameliorated OA progression both in OA chondrocytes and OA mouse models. Moreover, INSR inactivated JAK2/STAT3 pathway in OA chondrocytes. Dual luciferase report and CHIP assay results confirmed that INSR was transcriptionally regulated by KLF4. As shown in MS-PCR results, INSR expression was mediated by DNA methylation in OA.

CONCLUSION

Our findings suggested that INSR, as a key regulator for OA, was regulated by transcription factor KLF4 and DNA methylation, thereby mediating the activation of JAK2/STAT3 signaling, which was considered as an underlying therapeutic target for OA.

Activation of c-Jun N-Terminal Kinase, a Potential Therapeutic Target in Autoimmune Arthritis

The c-Jun-N-terminal kinase (JNK) is a critical mediator involved in various physiological processes, such as immune responses, and the pathogenesis of various diseases, including autoimmune disorders. JNK is one of the crucial downstream signaling molecules of various immune triggers, mainly proinflammatory cytokines, in autoimmune arthritic conditions, mainly including rheumatoid arthritis, ankylosing spondylitis, and psoriatic arthritis. The activation of JNK is regulated in a complex manner by upstream kinases and phosphatases. Noticeably, different subtypes of JNKs behave differentially in immune responses. Furthermore, aside from biologics targeting proinflammatory cytokines, small-molecule inhibitors targeting signaling molecules such as Janus kinases can act as very powerful therapeutics in autoimmune arthritis patients unresponsiveness to conventional synthetic antirheumatic drugs. Nevertheless, despite these encouraging therapies, a population of patients with an inadequate therapeutic response to all currently available medications still remains. These findings identify the critical signaling molecule JNK as an attractive target for investigation of the immunopathogenesis of autoimmune disorders and for consideration as a potential therapeutic target for patients with autoimmune arthritis to achieve better disease control. This review provides a useful overview of the roles of JNK, how JNK is regulated in immunopathogenic responses, and the potential of therapeutically targeting JNK in patients with autoimmune arthritis.

Genetics in Cartilage Lesions: Basic Science and Therapy Approaches

Cartilage lesions have a multifactorial nature, and genetic factors are their strongest determinants. As biochemical and genetic studies have dramatically progressed over the past decade, the molecular basis of cartilage pathologies has become clearer. Several homeostasis abnormalities within cartilaginous tissue have been found, including various structural changes, differential gene expression patterns, as well as altered epigenetic regulation. However, the efficient treatment of cartilage pathologies represents a substantial challenge. Understanding the complex genetic background pertaining to cartilage pathologies is useful primarily in the context of seeking new pathways leading to disease progression as well as in developing new targeted therapies. A technology utilizing gene transfer to deliver therapeutic genes to the site of injury is quickly becoming an emerging approach in cartilage renewal. The goal of this work is to provide an overview of the genetic basis of chondral lesions and the different approaches of the most recent systems exploiting therapeutic gene transfer in cartilage repair. The integration of tissue engineering with viral gene vectors is a novel and active area of research. However, despite promising preclinical data, this therapeutic concept needs to be supported by the growing body of clinical trials.

Agonism of GPR120 prevented IL-1β-induced reduction of extracellular matrix through SOX-9

Osteoarthritis (OA) is a whole-joint disease with extremely high prevalence. In all treatment approaches of OA, blocking the degradation of the cartilage extracellular matrix is an important treatment. In OA, overexpression of derivative enzymes leads to excessive catabolism and reduced synthesis of cartilage including type II collagen and aggrecan, which results in irreversible destruction of the joint. SOX9 is a transcription factor that regulates the synthesis of type II collagen and aggrecan and is significantly downregulated in OA. GPR120 has been reported to affect the pathophysiology of OA. In this study, we used the GPR120 agonist GW9508 and TUG891 in ATDC5 chondrocytes exposed to interleukin (IL)-1β to investigate the involvement of GPR120 in SOX9-mediated expression of type II collagen and aggrecan. Our findings show that agonism of GPR120 can reduce inflammation by inhibiting the expression of IL-6 and IL-8 induced by IL-1β. We also show that GW9508 and TUG891 rescue the expression of type II collagen and aggrecan by preventing the reduction of SOX9 expression. Additionally, we demonstrate that the effects of GW9508 on SOX9 expression are mediated through CREB and that GPR120 is indeed required for this effect. Thus, agonism of GPR120 by GW9508 might be a potential therapeutic strategy to halt or prevent cartilage degradation.