Cartilage damage in osteoarthritis and rheumatoid arthritis—two unequal siblings

Immunomodulatory nanosystems for treating inflammatory diseases

Inflammatory disease (ID) is an umbrella term encompassing all illnesses involving chronic inflammation as the central manifestation of pathogenesis. These include, inflammatory bowel diseases, hepatitis, pulmonary disorders, atherosclerosis, myocardial infarction, pancreatitis, arthritis, periodontitis, psoriasis. The IDs create a severe burden on healthcare and significantly impact the global socio-economic balance. Unfortunately, the standard therapies that rely on a combination of anti-inflammatory and immunosuppressive agents are palliative and provide only short-term relief. In contrast, the emerging concept of immunomodulatory nanosystems (IMNs) has the potential to address the underlying causes and prevent reoccurrence, thereby, creating new opportunities for treating IDs. The IMNs offer exquisite ability to precisely modulate the immune system for a therapeutic advantage. The nano-sized dimension of IMNs allows them to efficiently infiltrate lymphatic drainage, interact with immune cells, and subsequently to undergo rapid endocytosis by hyperactive immune cells (HICs) at inflamed sites. Thus, IMNs serve to restore dysfunctional or HICs and alleviate the inflammation. We identified that different IMNs exert their immunomodulatory action via either of the seven mechanisms to modulate; cytokine production, cytokine neutralization, cellular infiltration, macrophage polarization, HICs growth inhibition, stimulating T-reg mediated tolerance and modulating oxidative-stress. In this article, we discussed representative examples of IMNs by highlighting their rationalization, design principle, and mechanism of action in context of treating various IDs. Lastly, we highlighted technical challenges in the application of IMNs and explored the future direction of research, which could potentially help to overcome those challenges.

Extensive cytokine analysis in synovial fluid of osteoarthritis patients

OBJECTIVE

Osteoarthritis (OA) is a joint disease characterized by articular cartilage loss and afflicts many people worldwide. However, diagnostic methods and treatment options remain limited and are often characterized by low sensitivity and low efficacy. The focus of the present study was to identify proteomic biomarkers in synovial fluid to improve diagnosis and therapy of OA patients.

METHODS

Antibody array technology was utilized for protein expression profiling of synovial fluid from 24 OA patients and 24 healthy persons.

RESULTS

Compared with healthy persons, twenty proteins showed lower expression levels in OA patients, while thirty proteins had higher levels. Among these differential proteins, GITRL, CEACAM-1, FSH, EG-VEGF, FGF-4, PIGF, Cystatin EM and NT-4 were found for the first time to be differentially expressed in OA. Bioinformatics analysis showed that most of these differential proteins were involved leukocytes events, and some differentially expressed proteins including IL-18, CXCL1, CTLA4, MIP-3b, CD40, MMP-1, THBS1, CCL11, PAI-1, BAFF, aggrecan, angiogenin and follistatin were located in central positions of the protein-protein interaction (PPI) network.

CONCLUSION

We speculate that leukocyte proliferation and migration to the joint may be an important pathogenesis of OA, which needs a further validation. The central proteins of the PPI network may play a more pivotal role in OA. The newly identified differentially expressed proteins may be novel biomarkers for OA diagnosis and targets for OA therapy.

Naturally occurring coumestans from plants, their biological activities and therapeutic effects on human diseases

Naturally occurring coumestans are known as a collection of plant-derived polycyclic aromatic secondary metabolites which are characterized by the presence of an oxygen heterocyclic four-ring system comprising a coumarin moiety and a benzofuran moiety sharing a C˭C bond. Recently, there is an increasing attention in excavating the medicinal potential of coumestans, particularly coumestrol, wedelolactone, psoralidin and glycyrol, in a variety of diseases. This review is a comprehensive inventory of the chemical structures of coumestans isolated from various plant sources during the period of 1956-2020, together with their reported biological activities. 120 molecules were collected and further classified as coumestans containing core skeleton, dimethylpyranocoumestans, furanocoumestans, O-glycosylated coumestans and others, which showed a wide range of pharmacological activities including estrogenic, anti-cancer, anti-inflammatory, anti-osteoporotic, organ protective, neuroprotective, anti-diabetic and anti-obesity, antimicrobial, immunosuppressive, antioxidant and skin-protective activities. Furthermore, this review focuses on the counteraction of coumestans against bone diseases and organ damages, and the involved molecular mechanisms, which could provide important information to better understand the medicinal values of these compounds. This review is intended to be instructive for the rational design and development of less toxic and more effective drugs with a coumestan scaffold.

Chromatin accessibility landscapes of immune cells in rheumatoid arthritis nominate monocytes in disease pathogenesis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that involves a variety of cell types. However, how the epigenetic dysregulations of peripheral immune cells contribute to the pathogenesis of RA still remains largely unclear.

RESULTS

Here, we analysed the genome-wide active DNA regulatory elements of four major immune cells, namely monocytes, B cells, CD4⁺ T cells and CD8⁺ T cells, in peripheral blood of RA patients, osteoarthritis (OA) patients and healthy donors using Assay of Transposase Accessible Chromatin with sequencing (ATAC-seq). We found a strong RA-associated chromatin dysregulation signature in monocytes, but no other examined cell types. Moreover, we found that serum C-reactive protein (CRP) can induce the RA-associated chromatin dysregulation in monocytes via in vitro experiments. And the extent of this dysregulation was regulated through the transcription factor FRA2.

CONCLUSIONS

Together, our study revealed a CRP-induced pathogenic chromatin dysregulation signature in monocytes from RA patients and predicted the responsible signalling pathway as potential therapeutic targets for the disease.

Mechanical stress determines the configuration of TGFβ activation in articular cartilage

Our incomplete understanding of osteoarthritis (OA) pathogenesis has significantly hindered the development of disease-modifying therapy. The functional relationship between subchondral bone (SB) and articular cartilage (AC) is unclear. Here, we found that the changes of SB architecture altered the distribution of mechanical stress on AC. Importantly, the latter is well aligned with the pattern of transforming growth factor beta (TGFβ) activity in AC, which is essential in the regulation of AC homeostasis. Specifically, TGFβ activity is concentrated in the areas of AC with high mechanical stress. A high level of TGFβ disrupts the cartilage homeostasis and impairs the metabolic activity of chondrocytes. Mechanical stress stimulates talin-centered cytoskeletal reorganization and the consequent increase of cell contractile forces and cell stiffness of chondrocytes, which triggers αV integrin-mediated TGFβ activation. Knockout of αV integrin in chondrocytes reversed the alteration of TGFβ activation and subsequent metabolic abnormalities in AC and attenuated cartilage degeneration in an OA mouse model. Thus, SB structure determines the patterns of mechanical stress and the configuration of TGFβ activation in AC, which subsequently regulates chondrocyte metabolism and AC homeostasis.

Recent Developments in Clinical Applications of Mesenchymal Stem Cells in the Treatment of Rheumatoid Arthritis and Osteoarthritis

Mesenchymal stem cell (MSC) therapies have been used as cell-based treatments for decades, owing to their anti-inflammatory, immunomodulatory, and regenerative properties. With high expectations, many ongoing clinical trials are investigating the safety and efficacy of MSC therapies to treat arthritic diseases. Studies on osteoarthritis (OA) have shown positive clinical outcomes, with improved joint function, pain level, and quality of life. In addition, few clinical MSC trials conducted on rheumatoid arthritis (RA) patients have also displayed some optimistic outlook. The largely positive outcomes in clinical trials without severe side effects establish MSCs as promising tools for arthritis treatment. However, further research is required to investigate its applicability in clinical settings. This review discusses the most recent advances in clinical studies on MSC therapies for OA and RA.

Artificial Intelligence for Ultrasound Informative Image Selection of Metacarpal Head Cartilage. A Pilot Study

Objectives: This study aims to develop an automatic deep-learning algorithm, which is based on Convolutional Neural Networks (CNNs), for ultrasound informative-image selection of hyaline cartilage at metacarpal head level. The algorithm performance and that of three beginner sonographers were compared with an expert assessment, which was considered the gold standard.

Methods: The study was divided into two steps. In the first one, an automatic deep-learning algorithm for image selection was developed using 1,600 ultrasound (US) images of the metacarpal head cartilage (MHC) acquired in 40 healthy subjects using a very high-frequency probe (up to 22 MHz). The algorithm task was to identify US images defined informative as they show enough information to fulfill the Outcome Measure in Rheumatology US definition of healthy hyaline cartilage. The algorithm relied on VGG16 CNN, which was fine-tuned to classify US images in informative and non-informative ones. A repeated leave-four-subject out cross-validation was performed using the expert sonographer assessment as gold-standard. In the second step, the expert assessed the algorithm and the beginner sonographers' ability to obtain US informative images of the MHC.

Results: The VGG16 CNN showed excellent performance in the first step, with a mean area (AUC) under the receiver operating characteristic curve, computed among the 10 models obtained from cross-validation, of 0.99 ± 0.01. The model that reached the best AUC on the testing set, which we named “MHC identifier 1,” was then evaluated by the expert sonographer. The agreement between the algorithm, and the expert sonographer was almost perfect [Cohen's kappa: 0.84 (95% confidence interval: 0.71–0.98)], whereas the agreement between the expert and the beginner sonographers using conventional assessment was moderate [Cohen's kappa: 0.63 (95% confidence interval: 0.49–0.76)]. The conventional obtainment of US images by beginner sonographers required 6.0 ± 1.0 min, whereas US videoclip acquisition by a beginner sonographer lasted only 2.0 ± 0.8 min.

Conclusion: This study paves the way for the automatic identification of informative US images for assessing MHC. This may redefine the US reliability in the evaluation of MHC integrity, especially in terms of intrareader reliability and may support beginner sonographers during US training.

Triborheological Study under Physiological Conditions of PVA Hydrogel/HA Lubricant as Synthetic System for Soft Tissue Replacement

In soft tissue replacement, hydrophilic, flexible, and biocompatible materials are used to reduce wear and coefficient of friction. This study aims to develop and evaluate a solid/liquid triborheological system, polyvinyl alcohol (PVA)/hyaluronic acid (HA), to mimic conditions in human synovial joints. Hydrogel specimens prepared via the freeze–thawing technique from a 10% (w/v) PVA aqueous solution were cut into disc shapes (5 ± 0.5 mm thickness). Compression tests of PVA hydrogels presented a Young’s modulus of 2.26 ± 0.52 MPa. Friction tests were performed on a Discovery Hybrid Rheometer DHR-3 under physiological conditions using 4 mg/mL HA solution as lubricant at 37 °C. Contact force was applied between 1 and 20 N, highlighting a coefficient of friction change of 0.11 to 0.31 between lubricated and dry states at 3 N load (angular velocity: 40 rad/s). Thermal behavior was evaluated by differential scanning calorimetry (DSC) in the range of 25–250 °C (5 °C/min rate), showing an endothermic behavior with a melting temperature (Tm) around 231.15 °C. Scanning Electron Microscopy (SEM) tests showed a microporous network that enhanced water content absorption to 82.99 ± 1.5%. Hydrogel achieved solid/liquid lubrication, exhibiting a trapped lubricant pool that supported loads, keeping low coefficient of friction during lubricated tests. In dry tests, interstitial water evaporates continuously without countering sliding movement friction.

Roles of leptin on the key effector cells of rheumatoid arthritis

Leptin, an adipokine sharing structural characteristics of the long-chain helical cytokine family with the crucial role as a regulator in energy homeostasis, has been paid more and more attention to its immunoregulatory function. Emerging evidence has indicated the roles of leptin on autoimmune diseases such as systemic lupus erythematous (SLE), multiple sclerosis (MS), rheumatoid arthritis (RA) and psoriasis, implying that leptin may be involved in autoimmune disorders. It is very definite that there exists immunocyte dysfunction in RA patients. Growing data has manifested that leptin is increased in both serum and synovial fluid of RA patients compared to healthy controls, suggesting leptin probably takes part in the pathogenesis of RA. The aim of this review is to discuss about what we currently know with regard to the role of leptin in immune system and its effects on RA crucial cells. To clarify the role of leptin in the pathogenesis of RA is beneficial to both the treatment and medical study.

Effect of oblique headless compression screw fixation for metacarpal shaft fracture: a biomechanical in vitro study

Background

Metacarpal shaft fracture is a common fracture in hand trauma injuries. Surgical intervention is indicated when fractures are unstable or involve considerable displacement. Current fixation options include Kirschner wire, bone plates, and intramedullary headless screws. Common complications include joint stiffness, tendon irritation, implant loosening, and cartilage damage.

Objective

We propose a modified fixation approach using headless compression screws to treat transverse or short-oblique metacarpal shaft fracture.

Materials and methods

We used a saw blade to model transverse metacarpal neck fractures in 28 fresh porcine metacarpals, which were then treated with the following four fixation methods: (1) locked plate with five locked bicortical screws (LP group), (2) regular plate with five bicortical screws (RP group), (3) two Kirschner wires (K group), and (4) a headless compression screw (HC group). In the HC group, we proposed a novel fixation model in which the screw trajectory was oblique to the long axis of the metacarpal bone. The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; thus, the screw did not damage the articular cartilage. The specimens were tested using a modified three-point bending test on a material testing system. The maximum fracture forces and stiffness values of the four fixation types were determined by observing the force–displacement curves. Finally, the Kruskal–Wallis test was adopted to process the data, and the exact Wilcoxon rank sum test with Bonferroni adjustment was performed to conduct paired comparisons among the groups.

Results

The maximum fracture forces (median ± interquartile range [IQR]) of the LP, RP, HC, and K groups were 173.0 ± 81.0, 156.0 ± 117.9, 60.4 ± 21.0, and 51.8 ± 60.7 N, respectively. In addition, the stiffness values (median ± IQR) of the LP, HC, RP, and K groups were 29.6 ± 3.0, 23.1 ± 5.2, 22.6 ± 2.8, and 14.7 ± 5.6 N/mm, respectively.

Conclusion

Headless compression screw fixation provides fixation strength similar to locked and regular plates for the fixation of metacarpal shaft fractures. The headless screw was inserted obliquely to the long axis of the metacarpal bone. The entry point of the screw was in the dorsum of the metacarpal neck, and the exit point was in the volar cortex of the supracondylar region; therefore the articular cartilage iatrogenic injury can be avoidable. This modified fixation method may prevent tendon irritation and joint cartilage violation caused by plating and intramedullary headless screw fixation.

Clinical Efficacy of Platelet-Rich Plasma Injection and Its Association With Growth Factors in the Treatment of Mild to Moderate Knee Osteoarthritis: A Randomized Double-Blind Controlled Clinical Trial As Compared With Hyaluronic Acid

BACKGROUND

Although platelet-rich plasma (PRP) has potential as a regenerative treatment for knee osteoarthritis, its efficacy varies. Compositional differences among types of PRP could affect clinical outcomes, but the biological characterization of PRP is lacking.

PURPOSE

To assess the efficacy of intra-articular PRP injection in knee osteoarthritis as compared with hyaluronic acid (HA) injection and to determine whether the clinical efficacy of PRP is associated with its biological characteristics.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 110 patients with symptomatic knee osteoarthritis received a single injection of leukocyte-rich PRP (1 commercial kit) or HA. Clinical data were assessed at baseline and at 6 weeks and 3 and 6 months after injection. The primary endpoint was an improvement in the International Knee Documentation Committee (IKDC) subjective score at 6 months, and the secondary endpoints were improvements in scores based on the Patient Global Assessment, the visual analog scale (VAS) for pain, the Western Ontario and McMaster Universities Osteoarthritis Index, and the Samsung Medical Center patellofemoral score. Cell counts and concentrations of growth factors and cytokines in the injected PRP were assessed to determine their association with clinical outcomes.

RESULTS

PRP showed significantly improvement in IKDC subjective scores at 6 months (11.5 in the PRP group vs 6.3 in the HA group; P = .029). There were no significant differences between groups in other clinical outcomes. The Patient Global Assessment score at 6 months was better in the PRP group (P = .035). The proportion of patients who scored above the minimal clinically important difference (MCID) for VAS at 6 months was significantly higher in the PRP group (P = .044). Within the PRP group, the concentrations of platelet-derived growth factors were high in patients with a score above the MCID for VAS at 6 months. The incidence of adverse events did not differ between the groups (P > .05).

CONCLUSION

PRP had better clinical efficacy than HA. High concentrations of growth factors were observed in patients who scored above the MCID for clinical outcomes in the PRP group. These findings indicate that concentration of growth factors needs to be taken into consideration for future investigations of PRP in knee osteoarthritis.

REGISTRATION

NCT02211521 (ClinicalTrials.gov identifier).

lncRNA-CRNDE regulates BMSC chondrogenic differentiation and promotes cartilage repair in osteoarthritis through SIRT1/SOX9

Osteoarthritis (OA) is the most common chronic and degenerative joint disease. Although traditional OA medications can partially relieve pain, these medications cannot completely cure OA. Therefore, it is particularly important to find an effective treatment for OA. This study explored the function of long non-coding RNA (lncRNA)-colorectal neoplasia differentially expressed gene (CRNDE) in the chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the underlying molecular mechanism, aiming to develop a new treatment method for osteoarthritis. BMSCs were isolated from rat bone marrow using the gradient centrifugation method. And BMSC chondrogenic differentiation was induced with chondrogenic medium. The expression of lncRNA-CRNDE was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Silent information regulator factor 2-related enzyme 1 (SIRT1) and cartilage marker genes Aggrecan and collagen 2 (α1) protein expression were researched using western blot. Alcian blue staining was employed to examine the content of cartilage matrix proteoglycan glycosaminoglycan (GAG). The interaction between lncRNA-CRNDE and SIRT1 was detected by RNA pull-down and RNA immunoprecipitation (RIP) assay. Ubiquitination experiments were performed to measure the ubiquitination level of SIRT1. The combination between SMAD ubiquitination regulatory factor 2 (SMURF2) and SIRT1, as well as SRY-related high-mobility-group box 9 (SOX9) and collagen 2 (α1) promoter, was detected by Co-immunoprecipitation or ChIP. With the prolongation of induction time, the expression of lncRNA-CRNDE, SIRT1, cartilage marker genes Aggrecan and collagen 2 (α1) in BMSC osteogenic differentiation was gradually increased. Also, the content of cartilage matrix proteoglycan GAG was gradually elevated with the extension of the induction time. Further increase in the expression of SIRT1, cartilage marker genes Aggrecan and collagen 2 (α1) by overexpression of lncRNA-CRNDE also indicated elevated GAG content. RNA pull-down and RIP assay confirmed the binding between lncRNA-CRNDE and SIRT1. qRT-PCR and western blot showed that interference with lncRNA-CRNDE significantly inhibited the protein expression of SIRT1. BMSCs transfected with si-CRNDE increased ubiquitination levels of SIRT1 mediated by the E3 ligase SMURF2, leading to the reduced protein stability of SIRT1. However, overexpression of lncRNA-CRNDE increased the binding ability of SOX9 and collagen 2 (α1) promoter, which was reversed by the simultaneous transfection of CRNDE overexpression (pcDNA-CRNDE) and SIRT1 small interfering RNA (si-SIRT1). lncRNA-CRNDE regulates BMSC chondrogenic differentiation to promote cartilage repair in osteoarthritis through SIRT1/SOX9.

Magnetic resonance imaging of the knee joint in juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is an umbrella term for a group of diseases in children younger than 16 years old lasting six weeks or longer. Synovitis may lead to destructive and irreversible joint changes with subsequent functional impairment. Prompt diagnosis is essential to prevent permanent joint damage and preserve joint functionality. In the course of JIA both the axial and peripheral skeleton may be involved in the inflammatory process, but the knee joint is most frequently affected. New drugs and treatment protocols have forced the need for diagnosis at the earliest possible stage. Magnetic resonance imaging (MRI) allows early detection of lesions and constitutes a superior diagnostic imaging method. Synovitis, tenosynovitis, enthesitis, bursitis, osteitis, cartilage loss, bone cysts, and erosions are lesions diagnosed in JIA, and they can be precisely imaged in MRI. This article aims to present MRI inflammatory features of the knee in children with JIA based on the literature.

Inhibition effect of Caragana sinica root extracts on Osteoarthritis through MAPKs, NF-κB signaling pathway

Osteoarthritis (OA) is a common joint disease characterized by degradation and inflammation of cartilage extracellular matrix. We aimed to evaluate the protective effect of Caragana sinica root (CSR) on interleukin (IL)-1β-stimulated rat chondrocytes and a monosodium iodoacetate (MIA)-induced model of OA. In vitro, cell viability of CSR-treated chondrocytes was measured by MTT assay. The mRNA expression of Matrix metallopeptidases (MMPs), a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) and extracellular matrix (ECM) were analyzed by quantitative real-time PCR (qRT-PCR). Moreover, the protein expression of MAPK (phosphorylation of EKR, JNK, p38), inhibitory kappa B (IκBα) and nuclear factor-kappa B (NF-κB p65) was detected by western blot analysis. In vivo, the production of nitric oxide (NO) was detected by Griess reagent, while those of inflammatory mediators, MMPs and ECM were detected by ELISA. The degree of OA was evaluated by histopathological analyses, Osteoarthritis Research Society International (OARSI) score and micro-CT analysis. CSR significantly inhibited the expression of MMPs, ADAMTSs and the degradation of ECM in IL-1β-stimulated chondrocytes. Furthermore, CSR significantly suppressed IL-1β-stimulated of MAPKs, NF-κB signaling pathway. In vivo, CSR and Indomethacin inhibited the production of inflammatory mediators, MMPs and degradation of ECM in MIA-induced model of OA. In addition, CSR improved the severity of OA. Taken together, these results suggest CSR is a potential therapeutic active agent in the treatment of OA.

Metformin inhibits inflammation and bone destruction in collagen-induced arthritis in rats

Background

Metformin (MF) is a widely used biguanide oral hypoglycemic agent, which has obvious anti-inflammatory and immunomodulatory effects. However, the mechanism of MF on rheumatoid arthritis (RA) remains uncertain. In this study, we investigated the therapeutic effects of MF on collagen-induced arthritis (CIA).

Methods

CIA was induced in rats by intradermal injection of a mixture of bovine type II collagen and incomplete Freund's adjuvant (IFA) on day 0 and day 7 through the base of the tail. Intraperitoneal injection of MF (100 mg/kg) was given every 3 days, from day 14 for 3 weeks. The effects of MF on arthritis-induced systemic inflammation and synovitis were studied by pathological analysis of the knee joint and serological examination of peripheral blood in CIA rats. The bone protection effect of MF was studied by microscopic computed tomography (micro-CT) and histological analysis of the knee joint. The effects of MF on chondrocytes in CIA rats were studied by detecting the relevant pro-apoptotic mediators in the chondrocytes.

Results

After administration of MF in CIA rats, systemic inflammation and synovitis caused by arthritis were significantly suppressed. Histomorphometry and micro-CT analysis of the knee joint revealed that MF can protect bone by inhibiting the changes of trabecular bone in CIA rats. Histological analysis of the knee joint found that MF can inhibit osteoclast formation and degradation of the cartilage layer matrix. Detection of the relevant pro-apoptotic mediators in chondrocytes revealed that MF can significantly inhibit the apoptosis of chondrocytes in CIA rats.

Conclusions

Our study showed that MF can inhibit systemic inflammation and synovitis and plays a role in bone protection by inhibiting cartilage layer matrix degradation, osteoclast formation, and chondrocyte apoptosis.

Mesenchymal stem cells: amazing remedies for bone and cartilage defects

Skeletal disorders are among the leading debilitating factors affecting millions of people worldwide. The use of stem cells for tissue repair has raised many promises in various medical fields, including skeletal disorders. Mesenchymal stem cells (MSCs) are multipotent stromal cells with mesodermal and neural crest origin. These cells are one of the most attractive candidates in regenerative medicine, and their use could be helpful in repairing and regeneration of skeletal disorders through several mechanisms including homing, angiogenesis, differentiation, and response to inflammatory condition. The most widely studied sources of MSCs are bone marrow (BM), adipose tissue, muscle, umbilical cord (UC), umbilical cord blood (UCB), placenta (PL), Wharton's jelly (WJ), and amniotic fluid. These cells are capable of differentiating into osteoblasts, chondrocytes, adipocytes, and myocytes in vitro. MSCs obtained from various sources have diverse capabilities of secreting many different cytokines, growth factors, and chemokines. It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues. Accordingly, differential identification of MSCs' secretome enables us to make optimal choices in skeletal disorders considering various sources. This review discusses and compares the therapeutic abilities of MSCs from different sources for bone and cartilage diseases.

The circadian clock and inflammation: A new insight

The circadian clock is a complex cellular mechanism that controls a series of physiological processes, including inflammation. It can directly interact physically with the components of the key inflammatory pathway. Similarly, inflammation can also lead to circadian rhythm disorders, which may further amplify the inflammatory response and aggravate tissue damage. This review offers a structured overview that focusses on the core proteins of the circadian clock and their interactions with inflammatory players, and provides a potential mechanism for the pathological rhythms observed under inflammatory conditions.

Exosome-mediated delivery of kartogenin for chondrogenesis of synovial fluid-derived mesenchymal stem cells and cartilage regeneration

Transplantation of synovial fluid-derived mesenchymal stem cells (SF-MSCs) is a viable therapy for cartilage degeneration of osteoarthritis (OA). But controlling chondrogenic differentiation of the transplanted SF-MSCs in the joints remains a challenge. Kartogenin (KGN) is a small molecule that has been discovered to induce differentiation of SF-MSCs to chondrocytes both in vitro and in vivo. The clinical application of KGN however is limited by its low water solubility. KGN forms precipitates in the cell, resulting in low effective concentration and thus limiting its chondrogesis-promoting activity. Here we report that targeted delivery of KGN to SF-MSCs by engineered exosomes leads to even dispersion of KGN in the cytosol, increases its effective concentration in the cell, and strongly promotes the chondrogenesis of SF-MSCs in vitro and in vivo. Fusing an MSC-binding peptide E7 with the exosomal membrane protein Lamp 2b yields exosomes with E7 peptide displayed on the surface (E7-Exo) that has SF-MSC targeting capability. KGN delivered by E7-Exo efficiently enters SF-MSCs and induces higher degree of cartilage differentiation than KGN alone or KGN delivered by exosomes without E7. Co-administration of SF-MSCs with E7-Exo/KGN in the knee joints via intra-articular injection also shows more pronounced therapeutic effects in a rat OA model than KGN alone or KGN delivered by exosomes without E7. Altogether, transplantation of SF-MSCs with in situ chondrogenesis enabled by E7-Exo delivered KGN holds promise towards as an advanced stem cell therapy for OA.

Identification of putative master regulators in rheumatoid arthritis synovial fibroblasts using gene expression data and network inference

Rheumatoid arthritis (RA) is a systemic autoimmune disease that affects the synovial joints of the body. Rheumatoid arthritis fibroblast-like synoviocytes (RA FLS) are central players in the disease pathogenesis, as they are involved in the secretion of cytokines and proteolytic enzymes, exhibit invasive traits, high rate of self-proliferation and an apoptosis-resistant phenotype. We aim at characterizing transcription factors (TFs) that are master regulators in RA FLS and could potentially explain phenotypic traits. We make use of differentially expressed genes in synovial tissue from patients suffering from RA and osteoarthritis (OA) to infer a TF co-regulatory network, using dedicated software. The co-regulatory network serves as a reference to analyze microarray and single-cell RNA-seq data from isolated RA FLS. We identified five master regulators specific to RA FLS, namely BATF, POU2AF1, STAT1, LEF1 and IRF4. TF activity of the identified master regulators was also estimated with the use of two additional, independent software. The identified TFs contribute to the regulation of inflammation, proliferation and apoptosis, as indicated by the comparison of their differentially expressed target genes with hallmark molecular signatures derived from the Molecular Signatures Database (MSigDB). Our results show that TFs influence could be used to identify putative master regulators of phenotypic traits and suggest novel, druggable targets for experimental validation.

Challenges with matrix metalloproteinase inhibition and future drug discovery avenues

INTRODUCTION

Matrix metalloproteinases have been in the scope of pharmaceutical drug discovery for decades as promising targets for drug development. Until present, no modulator of the enzyme class survived clinical trials, all failing for various reasons. Nevertheless, the target family did not lose its attractiveness and there is ever more evidence that MMP modulators are likely to overcome the hurdles and result in successful clinical therapies.

AREAS COVERED

This review provides an overview of past efforts that were taken in the development of MMP inhibitors and insight into promising strategies that might enable drug discovery in the field in the future. Small molecule inhibitors as well as biomolecules are reviewed.

EXPERT OPINION

Despite the lack of successful clinical trials in the past, there is ongoing research in the field of MMP modulation, proving the target class has not lost its appeal to pharmaceutical research. With ever-growing insights from different scientific fields that shed light on previously unknown correlations, it is now time to use synergies deriving from biological knowledge, chemical structure generation, and clinical application to reach the ultimate goal of bringing MMP derived drugs on a broad front for the benefit of patients into therapeutic use.

TAK1: a potent tumour necrosis factor inhibitor for the treatment of inflammatory diseases

Aberrant tumour necrosis factor (TNF) signalling is a hallmark of many inflammatory diseases including rheumatoid arthritis (RA), irritable bowel disease and lupus. Maladaptive TNF signalling can lead to hyper active downstream nuclear factor (NF)-κβ signalling in turn amplifying a cell's inflammatory response and exacerbating disease. Within the TNF intracellular inflammatory signalling cascade, transforming growth factor-β-activated kinase 1 (TAK1) has been shown to play a critical role in mediating signal transduction and downstream NF-κβ activation. Owing to its role in TNF inflammatory signalling, TAK1 has become a potential therapeutic target for the treatment of inflammatory diseases such as RA. This review highlights the current development of targeting the TNF-TAK1 signalling axis as a novel therapeutic strategy for the treatment of inflammatory diseases.

S1P facilitates IL-1β production in osteoblasts via the JAK and STAT3 signaling pathways

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, in which the immune system attacks synovial joint tissues. Interleukin (IL)-1β is a critical proinflammatory cytokine in RA progression. Sphingosine-1-phosphate (S1P), a platelet-derived lysophospholipid mediator, reportedly regulates osteoimmunology. Here, we investigated how S1P mediates IL-1β expression in osteoblasts. Our analysis of records from the Gene Expression Omnibus (GEO) database demonstrate higher levels of IL-1β in patients with RA compared with those with osteoarthritis. Stimulation of osteoblasts with S1P concentration dependently increased mRNA and protein expression of IL-1β. Elevations in IL-1β mRNA expression induced by S1P were reduced by the small interfering RNA (siRNA) against the S1P₁ receptor. S1P also augmented JAK and STAT3 molecular cascades. We also found that JAK and STAT3 inhibitors and their siRNAs antagonized S1P-promoted IL-1β expression. Our results indicate that S1P promotes the expression of IL-1β in osteoblasts via the S1P₁ receptor and the JAK and STAT3 signaling pathways.

Intra-articular Injection of Culture-Expanded Mesenchymal Stem Cells Without Adjuvant Surgery in Knee Osteoarthritis: A Systematic Review and Meta-analysis

BACKGROUND

Although many clinical studies have assessed the efficacy of mesenchymal stem cells (MSCs) in knee osteoarthritis, evidence on their efficacy remains unclear owing to heterogeneity of cell entity and concomitant procedures.

PURPOSE

To determine the efficacy of culture-expanded MSCs in knee osteoarthritis in terms of clinical outcome and cartilage repair via meta-analysis of randomized controlled trials (RCTs) without adjuvant surgery.

STUDY DESIGN

Meta-analysis.

METHODS

PubMed, Embase, the Cochrane Library, CINAHL, and Scopus were searched from inception to December 31, 2018. RCTs with culture-expanded MSCs for treating knee osteoarthritis were included. Studies with adjuvant surgery or cell concentrate were excluded. Quality was assessed by the Cochrane Collaboration risk-of-bias tool. For meta-analysis, data on clinical outcomes were measured using a visual analog scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and data on cartilage repair were measured using the Whole-Organ Magnetic Resonance Imaging Score (WORMS); categorization related to improvement was extracted.

RESULTS

Six RCTs (203 patients) were included. Two studies were deemed to have a low risk of bias. In pooled analysis, the only significant difference was in the VAS score (mean difference, -13.55; 95% CI, -22.19 to -4.9). In cumulative pain analysis with VAS and WOMAC pain scores, there was significant improvement after treatment (standardized mean difference, -0.54; 95% CI, -0.85 to -0.23). There was no significant difference in cartilage repair assessed by magnetic resonance imaging (standardized mean difference, 0.11; 95% CI, -0.51 to 0.73), WORMS (standardized mean difference, 1.68; 95% CI -14.84 to 18.21), or categorical results (odds ratio, 1.56; 95% CI, 0.32-7.59).

CONCLUSION

Intra-articular injection of culture-expanded MSCs without adjuvant surgery can improve pain for patients experiencing knee osteoarthritis at short-term follow-up (6-12 months). However, evidence regarding function and cartilage repair remains limited.

Secreted Osteoclastogenic Factor of Activated T Cells (SOFAT) Is Associated With Rheumatoid Arthritis and Joint Pain: Initial Evidences of a New Pathway

Rheumatoid arthritis (RA) has an inflammatory milieu in the synovial compartment, which is regulated by a complex cytokine and chemokine network that induces continuously degenerative and inflammatory reactions. The secreted osteoclastogenic factor of activated T cells (SOFAT) is a unique cytokine and represents an alternative pathway for osteoclast activation. In this study, we examined whether SOFAT is able to induce joint pain and investigated the presence of SOFAT in a Collagen-induced Arthritis (CIA) model and in human subjects. Here, we found that an intra-articular stimulation with SOFAT (1, 10, 100, or 1,000 ng/10 μl) in the knee joint significantly decreases the mechanical threshold in the hind paw of mice (p < 0.05). Moreover, after a second injection of SOFAT, the mechanical threshold decrease was sustained for up to 8 days (p < 0.05). In the CIA model, the immunohistochemical assay of knee joint showed positivity stained for SOFAT, and the mRNA and protein expression of SOFAT were significantly higher in the affected-group (p < 0.05). Besides, the mRNA of RANKL, IL-1β, IL-6, and IL-15 were significantly higher in the affected-group (p < 0.05). Finally, SOFAT was detected in the synovial fluid of RA patients, but not in OA patients (p < 0.05). In conclusion, SOFAT is up regulated in inflammatory milieu such as RA but not in non-inflammatory OA. SOFAT may be a novel molecule in the complex inflammatory phenotype of RA.

Differential patterns of pathology in and interaction between joint tissues in long-term osteoarthritis with different initiating causes: phenotype matters

OBJECTIVE

To determine if osteoarthritis (OA) progression and joint tissue-pathology associations link specific animal models to different human OA phenotypes.

DESIGN

Male 11-week-old C57BL6 mice had unilateral medial-meniscal-destabilization (DMM) or antigen-induced-arthritis (AIA). Joint tissue histopathology was scored day-3 to week-16. Tissue-pathology associations (corrected for time and at week-16) were determined by partial correlation coefficients, and odds ratios (OR) calculated for likelihood of cartilage damage and joint inflammation by ordinal-logistic-regression.

RESULTS

Despite distinct temporal patterns of progression, by week-16 joint-wide OA pathology in DMM and AIA was equivalent. Significant pathology associations common to both models included: osteophyte size and maturity (r > 0.4); subchondral bone (SCB) sclerosis and osteophyte maturity (r > 0.25); cartilage erosion and chondrocyte hypertrophy/apoptosis (r > 0.4), SCB sclerosis (r > 0.26), osteophyte size (r > 0.3), and maturity (r > 0.32). DMM-specific associations were between cartilage proteoglycan loss and structural damage (r = 0.56), osteophyte maturity (r = 0.49), size (r = 0.45), and SCB sclerosis (r = 0.28). AIA-specific associations were between SCB sclerosis and chondrocyte hypertrophy/apoptosis (r = 0.40) and osteophyte size (r = 0.37); and synovitis with cartilage structural damage (r = 0.18). No tissue-pathology associations were common to both models at week-16. Increased likelihood of cartilage structural damage was associated with: chondrocyte hypertrophy/apoptosis (OR>1.7), and osteophyte size (OR>2.3) in both models; SCB sclerosis (OR = 2.0) and proteoglycan loss (OR = 2.4) in DMM; and synovitis (OR = 1.2) in AIA. Joint inflammation was associated positively with cartilage proteoglycan loss (OR = 1.4) and inversely with osteophyte size (OR = 0.21) in AIA only.

CONCLUSION

This study highlights the importance of defining OA-models by initiating mechanisms and progression, not just end-stage joint-tissue pathology.

Salvianolic Acid A Has Anti-Osteoarthritis Effect In Vitro and In Vivo

Osteoarthritis (OA) is a degenerative disease found in middle-aged and elderly people, which seriously affects their quality of life. The anti-inflammatory and anti-apoptosis pharmacological effects of salvianolic acid A (SAA) have been shown in many studies. In this study, we intended to explore the anti-inflammatory and anti-apoptotic effects of SAA in OA. We evaluated the expression of pro-inflammatory mediators and cartilage matrix catabolic enzymes in chondrocytes by ELISA, Griess reaction, immunofluorescence, and Western blot, which includes nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), MMPs (MMP-3, MMP-13), and ADAMTS-5. Bax, Bcl-2, and cleaved caspase-3 were also measured by Western blot methods. The results of this experiment in vitro showed that SAA not only inhibited the production of inflammatory mediators induced by IL-1β and the loss of cartilage matrix but also reduced the apoptosis of mouse chondrocytes induced by IL-1β. According to the results of immunofluorescence and Western blot, SAA inhibited the activation of the NF-κB pathway and MAPK pathway. The results of these in vitro experiments revealed for the first time that SAA down-regulated the production of inflammatory mediators and inhibited the apoptosis of mouse chondrocytes and the degradation of extracellular matrix (ECM), which may be attributed to the inhibition of the activation of NF-κB and MAPK signaling pathways. In the in vivo experiments, 45 mice were randomly divided among three groups (the sham group, OA group, and OA + SAA group). The results of animal experiments showed that SAA treatment for eight consecutive weeks inhibited further deterioration of OA. These results demonstrate that SAA plays an active therapeutic role in the development of OA.

Salvianolic Acid A Exhibits Anti-Inflammatory and Antiarthritic Effects via Inhibiting NF-κB and p38/MAPK Pathways

INTRODUCTION

Osteoarthritis (OA), a chronic joint disease, combines with massive inflammation and plays a vital role in cartilage degeneration. The main strategy in clinic is controlling inflammation, thereby treating osteoarthritis. Salvianolic acid A (SAA) is a type of phenolic acid, derived from a traditional chinese herbal medicine Danshen that is extensively used clinically.

METHODS AND RESULTS

We observed the anti-inflammatory and antiarthritic effects of SAA in IL-1β-stimulated cells. We found that SAA evidently decreased the expression of mainly inflammatory factors, exerted the remarkable effects of anti-inflammation and anti-arthritis. Furthermore, SAA inhibited the expression of Matrix metalloproteinases (MMP1, MMP13), and ADAMTS-5 and raised the synthesis of collagen II and aggrecan. Additionally, the results indicated that SAA gave rise to the effects by down-regulation of NF-κB and p38/MAPK pathways.

DISCUSSION

Our study demonstrates that SAA may be a promising anti-inflammatory for the treatment of OA in clinic.

Role of Chondrocytes in the Development of Rheumatoid Arthritis Via Transmembrane Protein 147-Mediated NF-κB Activation

OBJECTIVE

We have previously reported that the coactivation of NF-κB and STAT3 in nonimmune cells, including synovial fibroblasts, enhances the expression of NF-κB target genes and plays a role in chronic inflammation and rheumatoid arthritis (RA). This study was undertaken to examine the role of NF-κB activation in chondrocytes and better understand the pathogenesis of RA. Furthermore, transmembrane protein 147 (TMEM147) was investigated as a representative NF-κB activator in chondrocytes.

METHODS

Clinical samples from RA patients were analyzed by immunohistochemistry. Specimens obtained from patients with polydactyly were used as control samples. The functional contribution of chondrocytes and TMEM147 to arthritis was examined in several murine models of RA. In vitro experiments (quantitative polymerase chain reaction, RNA interference, immunoprecipitation, and confocal microscopy) were performed to investigate the mechanism of action of TMEM147 in chondrocytes.

RESULTS

Samples obtained from RA patients and mouse models of RA showed coactivation of NF-κB and STAT3 in chondrocytes (P < 0.001). This coactivation induced a synergistic expression of NF-κB targets in vitro (P < 0.01). Chondrocyte-specific deletion of STAT3 significantly suppressed the development of cytokine-induced RA (P < 0.01). TMEM147 was highly expressed in chondrocytes from RA patient samples and the mouse models of RA. Gene silencing of TMEM147 or anti-TMEM147 antibody treatment inhibited the cytokine-mediated activation of NF-κB in vitro (P < 0.01) and suppressed cytokine-induced RA in vivo (P < 0.01). Mechanistically, TMEM147 molecules acted as scaffold proteins for the NF-κB complex, which included breakpoint cluster region and casein kinase 2, and enhanced NF-κB activity.

CONCLUSION

These results suggest that chondrocytes play a role in the development of RA via TMEM147-mediated NF-κB activation and indicate a novel therapeutic strategy for RA.

Rapid and Detergent-Free Decellularization of Cartilage

The use of decellularized tissues or organs as cell culture scaffolds has proven to be a promising approach for tissue engineering and regenerative medicine, as these decellularized tissues can provide the instructive niche for cell differentiation and functions. Cartilage is a largely avascular tissue with limited regenerative capacity. Lesions caused by arthritis can lead to severe cartilage degeneration. Previous studies have indicated that decellularized cartilage can be used as scaffolds that support the chondrogenic differentiation of adult stem cells. However, these decellularization protocols all require the use of denaturing agents, such as high salt and detergents, that lead to the artifactual disruption of the chemical and physical integrity of the tissue microenvironment. Here, we established a new decellularization method for cartilage, through a combined effect of freezing-thawing, sectioning, and sonication in water. This protocol achieved the complete removal of cells within minutes, instead of hours or days required by existing procedures, and does not use any detergent. The resulting decellularized cartilage preserved the native ultrastructure and biochemical contents, including glycosaminoglycans, which is typically depleted by traditional decellularization methods. Human mesenchymal stem cells could readily adhere onto the decellularized cartilage. Together, this work unveils a simple new method for decellularizing cartilage, which will be useful in studying how tissue microenvironment supports chondrocyte growth and functions. Impact statement In this study, we develop a simple, fast cartilage decellularization method that does not require any detergent, so that the decellularized cartilage chemistry is preserved. Traditional detergent-based decellularization removes the tissue biochemical contents (i.e., glycosaminoglycans). In this new water decellularization protocol, the biochemical contents of cartilage can be preserved. This allows the study of biochemistry and physical content in extracellular matrix as a whole, and this protocol would definitely be useful for studying the effect of tissue microenvironment in supporting chondrocyte growth and functions.

Clinical therapeutic efficacy of mesenchymal stem cells derived from adipose or bone marrow for knee osteoarthritis: a meta-analysis of randomized controlled trials

Aim: This meta-analysis, only including randomized controlled trials (RCTs), was conducted to assess separately and compare the therapeutic efficacy of adipose-derived mesenchymal stem cells (ADMSCs) and bone marrow-derived mesenchymal stem cells (BMSCs) for knee osteoarthritis (OA) at the same follow-up time. Methods: Potential relevant researches were identified from PubMed, Web of Science, Embase, Cochrane Library and clinicaltrials.gov. The data, from clinical trials concentrating on knee OA treated with ADMSCs or BMSCs, were extracted and pooled for meta-analysis to compare the clinical outcomes of patients with knee OA in visual analog scale (VAS), Western Ontario McMaster Universities Osteoarthritis Index (WOMAC), Lysholm knee scale (Lysholm) and Tegner activity scale (Tegner). Results: Nine randomized controlled trials including a total of 377 patients met the inclusion criteria. This meta-analysis obtained the following results. First, the improvement of VAS scores was statistically significant after BMSCs treatment at 6-, 12- and 24-month follow-up compared with control groups (p < 0.01). In contrast, the improvement of WOMAC scores was of no statistical significance, but showed a positive trend with the prolongation of the follow-up time (6 months: mean difference [MD] = 6.51; 95% CI: -2.38 to 15.40; p = 0.15; 12 months: MD = -6.81; 95% CI: -13.94 to 0.33; p = 0.06). Lysholm scores presented a similar pattern (12 months: MD = 1.93; 95% CI: -11.52 to 15.38; p = 0.78; 24 months: MD = 8.94; 95% CI: 1.45 to 16.43; p = 0.02). Second, VAS and WOMAC scores of patients after ADMSCs treatment were significantly improved at any follow-up time (p ≤ 0.05). The improvement of Lysholm scores was of no statistical significance compared with control groups, although treatment outcome at 12-month follow-up was better than that at 24-month follow-up, which was debatable because only data of one clinical trial were pooled in the analysis (12 months: MD = 7.50; 95% CI: -1.94 to 16.94; p = 0.12; 24 months: MD = 5.10; 95% CI: -3.02 to 13.22; p = 0.22). Finally, by comparing the statistical results of VAS and WOMAC scores, it could be concluded that the therapeutic effect of ADMSCs on knee OA was more effective than that of BMSCs. Conclusion: This meta-analysis showed that regeneration with BMSCs or ADMSCs had a great application potential in the treatment of patients with knee OA, and ADMSCs tended to be superior to BMSCs according to the limited clinical evidences available.

PBT-6, a Novel PI3KC2γ Inhibitor in Rheumatoid Arthritis

Phosphoinositide 3-kinase (PI3K) is considered as a promising therapeutic target for rheumatoid arthritis (RA) because of its involvement in inflammatory processes. However, limited studies have reported the involvement of PI3KC2γ in RA, and the underlying mechanism remains largely unknown. Therefore, we investigated the role of PI3KC2γ as a novel therapeutic target for RA and the effect of its selective inhibitor, PBT-6. In this study, we observed that PI3KC2γ was markedly increased in the synovial fluid and tissue as well as the PBMCs of patients with RA. PBT-6, a novel PI3KC2γ inhibitor, decreased the cell growth of TNF-mediated synovial fibroblasts and LPS-mediated macrophages. Furthermore, PBT-6 inhibited the PI3KC2γ expression and PI3K/ AKT signaling pathway in both synovial fibroblasts and macrophages. In addition, PBT-6 suppressed macrophage migration via CCL2 and osteoclastogenesis. In CIA mice, it significantly inhibited the progression and development of RA by decreasing arthritis scores and paw swelling. Three-dimensional micro-computed tomography confirmed that PBT-6 enhanced the joint structures in CIA mice. Taken together, our findings suggest that PI3KC2γ is a therapeutic target for RA, and PBT-6 could be developed as a novel PI3KC2γ inhibitor to target inflammatory diseases including RA.

Prevalence and distribution of cartilage damage at the metacarpal head level in rheumatoid arthritis and osteoarthritis: an ultrasound study

OBJECTIVES

To determine the prevalence and distribution of US-detected qualitative cartilage damage at metacarpal heads of patients with RA and hand OA.

METHODS

Fifty-two RA patients and 34 patients with hand OA were enrolled. US examination of the metacarpal head cartilage from the II to V finger of both hands was performed. A total of 414 MCP joints in RA and 266 MCP joints in OA patients were scanned with a linear probe up to 22 MHz. Qualitative assessments using a previously described scoring system for cartilage damage were performed. The prevalence and distribution of cartilage damage were analysed. Multivariate regression analysis was used to determine the predictive value of age, gender, BMI, disease duration and the presence of RF and anti-CCP antibodies for US-detected cartilage damage.

RESULTS

The metacarpal head cartilage was positive for cartilage damage in 35.7% (148/414) of MCP joints in RA and in 43.6% (116/266) of MCP joints in OA patients. In RA, the hyaline cartilage of the II and III metacarpal heads (bilaterally) was the most frequently affected. In OA, cartilage damage was more homogeneously distributed in all MCP joints. Multivariate regression analysis showed that age and disease duration, but not gender, BMI or autoantibody status, were independent predictors of US-detected cartilage damage in RA.

CONCLUSION

Cartilage damage was found in more than one-third of the MCP joints in both RA and OA patients, and in RA patients, the II and III MCP joints were the most damaged.

Macrophage: A Potential Target on Cartilage Regeneration

Cartilage lesions and osteoarthritis (OA) presents an ever-increasing clinical and socioeconomic burden. Synovial inflammation and articular inflammatory environment are the key factor for chondrocytes apoptosis and hypertrophy, ectopic bone formation and OA progression. To effectively treat OA, it is critical to develop a drug that skews inflammation toward a pro-chondrogenic microenvironment. In this narrative and critical review, we aim to see the potential use of immune cells modulation or cell therapy as therapeutic alternatives to OA patients. Macrophages are immune cells that are present in synovial lining, with different roles depending on their subtypes. These cells can polarize to pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes, being the latter associated with wound-healing by the production of ARG-1 and pro-chondrogenic cytokines, such as IL-10, IL-1RA, and TGF-b. Emerging evidence reveals that macrophage shift can be determined by several stimuli, apart from the conventional in vitro IL-4, IL-13, and IL-10. Evidences show the potential of physical exercise to induce type 2 response, favoring M2 polarization. Moreover, macrophages in contact with oxLDL have effect on the production of anabolic mediators as TGF-b. In the same direction, type II collagen, that plays a critical role in development and maturation process of chondrocytes, can also induce M2 macrophages, increasing TGF-b. The mTOR pathway activation in macrophages was shown to be able to polarize macrophages in vitro, though further studies are required. The possibility to use mesenchymal stem cells (MSCs) in cartilage restoration have a more concrete literature, besides, MSCs also have the capability to induce M2 macrophages. In the other direction, M1 polarized macrophages inhibit the proliferation and viability of MSCs and impair their ability to immunosuppress the environment, preventing cartilage repair. Therefore, even though MSCs therapeutic researches advances, other sources of M2 polarization are attractive issues, and further studies will contribute to the possibility to manipulate this polarization and to use it as a therapeutic approach in OA patients.

Destroy to Rebuild: The Connection Between Bone Tissue Remodeling and Matrix Metalloproteinases

Bone is a dynamic organ that undergoes constant remodeling, an energetically costly process by which old bone is replaced and localized bone defects are repaired to renew the skeleton over time, thereby maintaining skeletal health. This review provides a general overview of bone’s main players (bone lining cells, osteocytes, osteoclasts, reversal cells, and osteoblasts) that participate in bone remodeling. Placing emphasis on the family of extracellular matrix metalloproteinases (MMPs), we describe how: (i) Convergence of multiple protease families (including MMPs and cysteine proteinases) ensures complexity and robustness of the bone remodeling process, (ii) Enzymatic activity of MMPs affects bone physiology at the molecular and cellular levels and (iii) Either overexpression or deficiency/insufficiency of individual MMPs impairs healthy bone remodeling and systemic metabolism. Today, it is generally accepted that proteolytic activity is required for the degradation of bone tissue in osteoarthritis and osteoporosis. However, it is increasingly evident that inactivating mutations in MMP genes can also lead to bone pathology including osteolysis and metabolic abnormalities such as delayed growth. We argue that there remains a need to rethink the role played by proteases in bone physiology and pathology.

Platelet Rich Plasma for Treatment of Rheumatoid Arthritis: Case Series and Review of Literature

Platelet-rich plasma (PRP) is an autologous blood product with platelets above circulating levels and releases several growth factors after activation. PRP may help to decrease joint inflammation by modulating synovial cell proliferation and differentiation and inhibition of catabolic pathways in various articular conditions. Though PRP has shown good efficacy in osteoarthritis and other musculoskeletal conditions such as synovitis, epicondylitis, skeletal muscle injuries, and tendinopathy, there is limited experience for the use of PRP in patients with rheumatoid arthritis. Precise mechanisms of action of PRP are not known. We present clinical experience for treatment with PRP (2–4 ml) in four patients with rheumatoid arthritis who had inadequate response and persistent pain and inflammation with intra-articular steroids. Irrespective of past and ongoing treatments and duration of disease, all patients showed improvement in the visual analog scale and disease activity score of 28 joints at 4 and 8 weeks after injection. There was an improvement in joint inflammation on ultrasound imaging in some patients. These effects were sustained for up to 1 year. No adverse effects were reported in any patient. PRP may be a safe and useful therapy in patients with rheumatoid arthritis who fail to respond to one or more established treatment options.

Synovial fibroblasts and articular tissue remodelling: Role and mechanisms

Synovial joints are unique functional elements of the body and provide the ability for locomotion and for physical interaction with the environment. They are composed of different connective tissue structures, of which the synovial membrane is one central component. It shows a number of peculiarities that makes it different from other membranes in our body, while several lines of evidence suggest that synovial fibroblasts, also termed fibroblast-like synoviocytes (FLS) critically contribute to these peculiarities. This becomes evident particularly under disease conditions such as in rheumatoid arthritis and osteoarthritis, where the synovium is a key pathophysiological component. Therefore, an in-depth knowledge of FLS biology is not only important for understanding key features of articular function but also provides explanations for important characteristics of both degenerative and inflammatory joint diseases. This article reviews the structure, biochemical composition and functions of the synovial membrane and by focusing on the role of synovial fibroblasts explains key features of articular tissue remodelling particularly under disease conditions.

Fluorometric Imaging for Early Diagnosis and Prognosis of Rheumatoid Arthritis

Early diagnosis and monitoring of disease progress are of significant importance in the effective treatment of rheumatoid arthritis (RA), because the continuing inflammation can lead to irreversible joint damage and systemic complications. However, applying imaging modalities for the prognosis of RA remains challenging, because no tissue-specific guidelines are available to monitor the progressive course of RA. In this study, fluorometric imaging of RA is reported using bioengineered targeted agents of the blood vessel, bone, and cartilage in combination with the customized optical fluorescence imaging system. Separate but simultaneous tissue-specific images of synovitis, cartilage destruction, and bone resorption are obtained from a mouse model of RA, which allows quantification of the prognosis of diseases at each stage. Thus, the fluorometric imaging of RA by using tissue-specific contrast agents plays a key role in the systemic treatment of RA by monitoring structural damage and disease progression.

T1ρ-mapping for assessing knee joint cartilage in children with juvenile idiopathic arthritis - feasibility and repeatability

BACKGROUND

Ongoing arthritis in children with juvenile idiopathic arthritis (JIA) can result in cartilage damage.

OBJECTIVE

To study the feasibility and repeatability of T_1ρ for assessing knee cartilage in JIA and also to describe T_1ρ values and study correlation between T_1ρ and conventional MRI scores for disease activity.

MATERIALS AND METHODS

Thirteen children with JIA or suspected JIA underwent 3-tesla (T) knee MRI that included conventional sequences and a T_1ρ sequence. Segmentation of knee cartilage was carried out on T_1ρ images. We used intraclass correlation coefficient to study the repeatability of segmentation in a subset of five children. We used the juvenile arthritis MRI scoring system to discriminate inflamed from non-inflamed knees. The Mann-Whitney U and Spearman correlation compared T_1ρ between children with and without arthritis on MRI and correlated T_1ρ with the juvenile arthritis MRI score.

RESULTS

All children successfully completed the MRI examination. No images were excluded because of poor quality. Repeatability of T_1ρ measurement had an intraclass correlation coefficient (ICC) of 0.99 (P<0.001). We observed no structural cartilage damage and found no differences in T_1ρ between children with (n=7) and without (n=6) inflamed knees (37.8 ms vs. 31.7 ms, P=0.20). However, we observed a moderate correlation between T_1ρ values and the juvenile arthritis MRI synovitis score (r=0.59, P=0.04).

CONCLUSION

This pilot study suggests that T_1ρ is a feasible and repeatable quantitative imaging technique in children. T_1ρ values were associated with the juvenile arthritis MRI synovitis score.

Lycium barbarum polysaccharides exert an antioxidative effect on rat chondrocytes by activating the nuclear factor (erythroid-derived 2)-like 2 signaling pathway

INTRODUCTION

Oxidative stress is the main cause of osteoarthritis (OA). Lycium barbarum polysaccharides (LBP) have antioxidant properties. Thus, the potential effect of LBP on H₂O₂-stimulated chondrocytes was examined.

MATERIAL AND METHODS

The cell viability was detected by CCK-8. The reactive oxygen species (ROS) production and apoptosis rates were determined by flow cytometric analysis. The DNA damage was detected by comet assay. Real-time polymerase chain reaction (qPCR) and Western blot assays were performed to examine the expression of histone 2A family member X (γH2AX), checkpoint kinase 1 (Chk1), poly ADP-ribose polymerase (PARP), cysteinyl aspartate specific proteinase (caspase)-3/8/9, and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and its antioxidant-response element (ARE) dependent factors including heme oxygenase-1 (HO-1) and quinine oxidoreductase-1 (NQO-1).

RESULTS

Compared to the H₂O₂ group, LBP inhibited the ROS production and DNA damage caused by H₂O₂ (p < 0.05), respectively. LBP inhibited the mRNA and protein expressions of γH2AX and Chk1 (p < 0.05). Meanwhile, LBP significantly decreased apoptosis (p < 0.05). And LBP inhibited the expression levels of PARP and Caspase-3/8/9 (p < 0.05). Moreover, LBP increased the expression of Nrf2, HO-1and NQO-1 (p < 0.05). Furthermore, the depletion of Nrf2 that mediated by RNA interference reversed the apoptosis and DNA damage inhibition effect of LBP (p < 0.05).

CONCLUSIONS

LBP protected chondrocytes through inhibiting DNA damage and apoptosis caused by H₂O₂, in which the Nrf2/ARE signaling pathway played a positive role. It provided an inspiration for clinical application - developing LBP as a therapeutic agent and Nrf2 as a promising candidate.

Cathepsin K: The Action in and Beyond Bone

Cathepsin K (CatK) is one of the most potent proteases in lysosomal cysteine proteases family, of which main function is to mediate bone resorption. Currently, CatK is among the most attractive targets for anti-osteoporosis drug development. Although many pharmaceutical companies are working on the development of selective inhibitors for CatK, there is no FDA approved drug till now. Odanacatib (ODN) developed by Merck & Co. is the only CatK inhibitor candidate which demonstrated high therapeutic efficacy in patients with postmenopausal osteoporosis in Phase III clinical trials. Unfortunately, the development of ODN was finally terminated due to the cardio-cerebrovascular adverse effects. Therefore, it arouses concerns on the undesirable CatK inhibition in non-bone sites. It is known that CatK has far-reaching actions throughout various organs besides bone. Many studies have also demonstrated the involvement of CatK in various diseases beyond the musculoskeletal system. This review not only summarized the functional roles of CatK in bone and beyond bone, but also discussed the potential relevance of the CatK action beyond bone to the adverse effects of inhibiting CatK in non-bone sites.

S1P promotes IL-6 expression in osteoblasts through the PI3K, MEK/ERK and NF-κB signaling pathways

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, in which the immune system attacks joint tissue. Interleukin (IL)-6 is a key proinflammatory cytokine in RA progression. Sphingosine-1-phosphate (S1P), a platelet-derived lysophospholipid mediator, reportedly regulates osteoimmunology. Here, we examined the effects of S1P on IL-6 expression in osteoblasts. Our results and records from the Gene Expression Omnibus (GEO) database demonstrate higher levels of IL-6 in patients with RA compared with those with osteoarthritis. Stimulation of osteoblasts with S1P increased mRNA and protein expression of IL-6. PI3K, MEK, ERK and NF-κB inhibitors and their small interfering RNAs (siRNAs) reduced S1P-promoted IL-6 expression. S1P also facilitated PI3K, MEK/ERK and NF-κB signaling cascades. Our results indicate that S1P promotes the expression of IL-6 in osteoblasts via the PI3K, MEK/ERK and NF-κB signaling pathways.

Knockdown of PVT1 inhibits IL-1β-induced injury in chondrocytes by regulating miR-27b-3p/TRAF3 axis

Long noncoding RNA plasmacytoma variant translocation 1 (PVT1) has been identified to implicate in the progression of osteoarthritis (OA). However, the mechanism underlying PVT1 in OA development remains largely unknown. This study aimed to investigate the effect of PVT1 on interleukin-1 beta (IL-1β)-induced injury in chondrocytes and explore potential mechanism. The cartilage tissues from 25 OA patients and normal controls were collected. Human transformed chondrocytes C28/I2 were stimulated by IL-1β. The levels of PVT1, microRNA (miR)-27b-3p, and tumor necrosis factor receptor-associated factor 3 (TRAF3) were detected by quantitative real-time polymerase chain reaction or western blot. IL-1β-induced injury was investigated by cell viability, apoptosis, autophagy and inflammatory response using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, flow cytometry, western blot and enzyme linked immunosorbent assay, respectively. The target association between miR-27b-3p and PVT1 or TRAF3 was explored by luciferase reporter, RNA immunoprecipitation and RNA pull-down assays. We found that PVT1 expression was enhanced in OA patients and IL-1β-treated C28/I2 cells. Silence of PVT1 promoted cell viability and autophagy but suppressed apoptosis and inflammatory response in IL-1β-treated C28/I2 cells. miR-27b-3p was confirmed as a target of PVT1 and its deficiency reversed the suppressive effect of PVT1 knockdown on IL-1β-induced injury. TRAF3 was a target of miR-27b-3p and attenuated the effect of miR-27b-3p on IL-1β-induced injury in C28/I2 cells. Moreover, TRAF3 expression was positively regulated by PVT1 via sponging miR-27b-3p. Collectively, knockdown of PVT1 increased cell viability and autophagy but inhibited apoptosis and inflammatory response in chondrocytes treated by IL-1β via up-regulating miR-27b-3p and down-regulating TRAF3.

Knockdown of lncRNA MFI2-AS1 inhibits lipopolysaccharide-induced osteoarthritis progression by miR-130a-3p/TCF4

AIMS

Long noncoding RNA melanotransferrin antisense RNA (MFI2-AS1) plays a vital role in the development of multiple diseases. This study aimed to investigate the effect of this lncRNA on osteoarthritis progression and explore the interaction among MFI2-AS1, microRNA (miR)-130a-3p and transcription factor 4 (TCF4).

METHODS

Forty-six knee osteoarthritis tissues and 28 normal samples were collected. Human chondrocytes C28/I2 cells treated by lipopolysaccharide (LPS) were used as the model of osteoarthritis. The expression levels of MFI2-AS1, miR-130a-3p and TCF4 were detected by quantitative real-time polymerase chain reaction or western blot. LPS-induced chondrocytes injury was investigated by cell viability, apoptosis, inflammatory response and extracellular matrix degradation using MTT, flow cytometry, enzyme-linked immunosorbent assay and western blot. The target association between miR-130a-3p and MFI2-AS1 or TCF4 was confirmed by luciferase reporter assay and RNA immunoprecipitation.

RESULTS

MFI2-AS1 expression was increased in osteoarthritis tissues and LPS-treated C28/I2 cells. Silence of MFI2-AS1 attenuated LPS-induced viability suppression, apoptosis production, inflammatory response and extracellular matrix degradation. MFI2-AS1 was validated as a decoy of miR-130a-3p and TCF4 was confirmed as a target of miR-130a-3p. miR-130a-3p overexpression inhibited LPS-induced cell injury in C28/I2 cells by decreasing TCF4 expression. Moreover, knockdown of MFI2-AS1 alleviated LPS-induced cell injury in C28/I2 cells by mediating miR-130a-3p and TCF4.

CONCLUSION

Knockdown of MFI2-AS1 increased cell viability but suppressed apoptosis, inflammatory response and extracellular matrix degradation in LPS-treated chondrocytes by increasing miR-130a-3p and decreasing TCF4, indicating a novel target for the treatment of osteoarthritis.

Emerging quantitative MR imaging biomarkers in inflammatory arthritides

PURPOSE

To review quantitative magnetic resonance imaging (qMRI) methods for imaging inflammation in connective tissues and the skeleton in inflammatory arthritis. This review is designed for a broad audience including radiologists, imaging technologists, rheumatologists and other healthcare professionals.

METHODS

We discuss the use of qMRI for imaging skeletal inflammation from both technical and clinical perspectives. We consider how qMRI can be targeted to specific aspects of the pathological process in synovium, cartilage, bone, tendons and entheses. Evidence for the various techniques from studies of both adults and children with inflammatory arthritis is reviewed and critically appraised.

RESULTS

qMRI has the potential to objectively identify, characterize and quantify inflammation of the connective tissues and skeleton in both adult and pediatric patients. Measurements of tissue properties derived using qMRI methods can serve as imaging biomarkers, which are potentially more reproducible and informative than conventional MRI methods. Several qMRI methods are nearing transition into clinical practice and may inform diagnosis and treatment decisions, with the potential to improve patient outcomes.

CONCLUSIONS

qMRI enables specific assessment of inflammation in synovium, cartilage, bone, tendons and entheses, and can facilitate a more consistent, personalized approach to diagnosis, characterisation and monitoring of disease.

Inhibition of CD44 intracellular domain production suppresses bovine articular chondrocyte de-differentiation induced by excessive mechanical stress loading

CD44 fragmentation is enhanced in chondrocytes of osteoarthritis (OA) patients. We hypothesized that mechanical stress-induced enhancement of CD44-intracellular domain (CD44-ICD) production plays an important role in the de-differentiation of chondrocytes and OA. This study aimed to assess the relationship between CD44-ICD and chondrocyte gene expression. Monolayer cultured primary bovine articular chondrocytes (BACs) were subjected to cyclic tensile strain (CTS) loading. ADAM10 inhibitor (GI254023X) and γ-secretase inhibitor (DAPT) were used to inhibit CD44 cleavage. In overexpression experiments, BACs were electroporated with a plasmid encoding CD44-ICD. CTS loading increased the expression of ADAM10 and subsequent CD44 cleavage, while decreasing the expression of SOX9, aggrecan, and type 2 collagen (COL2). Overexpression of CD44-ICD also resulted in decreased expression of these chondrocyte genes. Both GI254023X and DAPT reduced the production of CD44-ICD upon CTS loading, and significantly rescued the reduction of SOX9 expression by CTS loading. Chemical inhibition of CD44-ICD production also rescued aggrecan and COL2 expression following CTS loading. Our findings suggest that CD44-ICD is closely associated with the de-differentiation of chondrocytes. Excessive mechanical stress loading promoted the de-differentiation of BACs by enhancing CD44 cleavage and CD44-ICD production. Suppression of CD44 cleavage has potential as a novel treatment strategy for OA.

Proinflammatory Effects of IL-1β Combined with IL-17A Promoted Cartilage Degradation and Suppressed Genes Associated with Cartilage Matrix Synthesis In Vitro

Combinations of IL-1β and other proinflammatory cytokines reportedly promote the severity of arthritis. We aimed to investigate the effects of IL-1β combined with IL-17A on cartilage degradation and synthesis in in vitro models. Cartilage explant degradation was determined using sulfated glycosaminoglycans (S-GAGs) levels, matrix metalloproteinase (MMP13) gene expression, uronic acid, and collagen contents. Cell morphology and accumulation of proteoglycans were evaluated using hematoxylin-eosin and safranin O staining, respectively. In the pellet culture model, expressions of cartilage-specific anabolic and catabolic genes were evaluated using real-time qRT-PCR. Early induction of MMP13 gene expression was found concomitantly with significant S-GAGs release. During the prolonged period, S-GAGs release was significantly elevated, while MMP-13 enzyme levels were persistently increased together with the reduction of the cartilaginous matrix molecules. The pellet culture showed anabolic gene downregulation, while expression of the proinflammatory cytokines, mediators, and MMP13 genes were elevated. After cytokine removal, these effects were restored to nearly basal levels. This study provides evidence that IL-1β combined with IL-17A promoted chronic inflammatory arthritis by activating the catabolic processes accompanied with the suppression of cartilage anabolism. These suggest that further applications, which suppress inflammatory enhancers, especially IL-17A, should be considered as a target for arthritis research and therapy.

Activation of RXR by bexarotene inhibits inflammatory conditions in human rheumatoid arthritis fibroblast‑like synoviocytes

Rheumatoid arthritis (RA) is a debilitating joint disease characterized by chronic inflammation, pathologic alteration of fibroblast‑like synoviocytes (FLS), destruction of cartilage and bone, and the formation of an invasive pannus. RA‑FLS exhibit increased proliferation and resistance to apoptosis. The retinoid X receptor (RXR) has a role in regulating cell cycle, differentiation and apoptosis, and agonism of RXR has been investigated as a treatment strategy in several types of cancer. However, there is little research on the effects of RXR agonism in other diseases. Bexarotene is a novel selective RXR ligand used in the treatment of T‑cell lymphoma. In the present study, bexarotene was used to investigate the involvement of RXR in tumor necrosis factor‑α (TNF‑α)‑induced RA conditions in human FLS. To the best of our knowledge, this is the first time that RXR has been demonstrated to be expressed in FLS and to be downregulated in response to TNF‑α stimulation. The present study also demonstrated that bexarotene exerted an anti‑inflammatory effect by downregulating expression of interleukin (IL)‑6, IL‑8, monocyte chemoattractant protein‑1, and high mobility group box‑1. Notably, bexarotene also rescued the TNF‑α‑induced downregulation of the anti‑inflammatory cytokines IL‑4 and transforming growth factor‑β1. Bexarotene treatment exhibited a potential protective effect against cartilage degradation by downregulating the expression of matrix metalloproteinase (MMP)‑1, MMP‑3 and MMP‑13. In addition, the present results demonstrated that the effects of bexarotene were mediated through the p38 mitogen‑activated protein kinase/nuclear factor‑κB pathway, via inhibition of p38 protein and the inhibitor α of κB phosphorylation. Taken together, the present findings demonstrated the potential of RXR agonism using bexarotene as a treatment against the development and progression of RA.

LncRNA HOTAIR-mediated Wnt/β-catenin network modeling to predict and validate therapeutic targets for cartilage damage

BACKGROUND

Cartilage damage is a crucial feature involved in several pathological conditions characterized by joint disorders, such as osteoarthritis and rheumatoid arthritis. Accumulated evidences showed that Wnt/β-catenin pathway plays a role in the pathogenesis of cartilage damage. In addition, it is experimentally documented that lncRNA (long non-coding RNA) HOTAIR plays a key role in the regulation of Wnt/β-catenin pathway based on directly decreased WIF-1 expression. Further, it is reported that Wnt/β-catenin pathway is a potent pathway to regulate the expression of MMP-13, which is responsible for degradation of collagen type II in articular cartilage. It is increasingly recognized that systems modeling approach provides an opportunity to understand the complex relationships and direct quantitative analysis of dynamic network in various diseases.

RESULTS

A dynamic network of lncRNA HOTAIR-mediated Wnt/β-catenin pathway regulating MMP-13 is developed to investigate the dynamic mechanism of the network involved in the pathogenesis of cartilage damage. Based on the network modeling, the potential therapeutic intervention point Axin is predicted and confirmed by the experimental validation.

CONCLUSIONS

Our study provides a promising strategy for revealing potential dynamic mechanism and assessing potential targets which contribute to the prevention of the pathological conditions related to cartilage damage.