Apoptosis and the loss of chondrocyte survival signals contribute to articular cartilage degradation in osteoarthritis

Natural products in osteoarthritis treatment: bridging basic research to clinical applications

Osteoarthritis (OA) is the most prevalent degenerative musculoskeletal disease, severely impacting the function of patients and potentially leading to disability, especially among the elderly population. Natural products (NPs), obtained from components or metabolites of plants, animals, microorganisms etc., have gained significant attention as important conservative treatments for various diseases. Recently, NPs have been well studied in preclinical and clinical researches, showing promising potential in the treatment of OA. In this review, we summed up the main signaling pathways affected by NPs in OA treatment, including NF-κB, MAPKs, PI3K/AKT, SIRT1, and other pathways, which are related to inflammation, anabolism and catabolism, and cell death. In addition, we described the therapeutic effects of NPs in different OA animal models and the current clinical studies in OA patients. At last, we discussed the potential research directions including in-depth analysis of the mechanisms and new application strategies of NPs for the OA treatment, so as to promote the basic research and clinical transformation in the future. We hope that this review may allow us to get a better understanding about the potential bioeffects and mechanisms of NPs in OA therapy, and ultimately improve the effectiveness of NPs-based clinical conservative treatment for OA patients.

Role of Apoptosis in the Pathogenesis of Osteoarthritis: An Explicative Review

Apoptosis is a complex regulatory, active cell death process that plays a role in cell development, homeostasis, and ageing. Cancer, developmental defects, and degenerative diseases are all pathogenic disorders caused by apoptosis dysregulation. Osteoarthritis (OA) is by far the most frequently diagnosed joint disease in the aged, and it is characterized by the ongoing breakdown of articular cartilage, which causes severe disability. Multiple variables regulate the anabolic and catabolic pathways of the cartilage matrix, which either directly or indirectly contribute to cartilage degeneration in osteoarthritis. Articular cartilage is a highly specialized tissue made up of an extracellular matrix of cells that are tightly packed together. As a result, chondrocyte survival is crucial for the preservation of an optimal cartilage matrix, and chondrocyte characteristics and survival compromise may result in articular cartilage failure. Inflammatory cytokines can either promote or inhibit apoptosis, the process of programmed cell death. Pro-apoptotic cytokines like TNF-α can induce cell death, while anti-apoptotic cytokines like IL-4 and IL-10 protect against apoptosis. The balance between these cytokines plays a critical role in determining cell fate and has implications for tissue damage and disease progression. Similarly, they contribute to the progression of OA by disrupting the metabolic balance in joint tissues by promoting catabolic and anabolic pathways. Their impact on cell joints, as well as the impacts of cell signalling pathways on cytokines and inflammatory substances, determines their function in osteoarthritis development. Apoptosis is evident in osteoarthritic cartilage; however, determining the relative role of chondrocyte apoptosis in the aetiology of OA is difficult, and the rate of apoptotic chondrocytes in osteoarthritic cartilage is inconsistent. The current study summarises the role of apoptosis in the development of osteoarthritis, the mediators, and signalling pathways that trigger the cascade of events, and the other inflammatory features involved.

Inhibition of LncRNA SNHG14 protects chondrocyte from injury in osteoarthritis via sponging miR-137

Long-chain noncoding small nucleolar RNA host gene 14 (LncRNA SNHG14) is highly expressed in various diseases and promotes diseases progression, but the role and mechanism of LncRNA SNHG14 on targeting miR-137 in promoting osteoarthritis (OA) chondrocyte injury remains unclear. To measure the expression of the LncRNAs SNHG14 and miR-137, cell survival, inflammatory response, chondrocyte apoptosis, and extracellular matrix (ECM) levels, we subjected human chondrocytes to a variety of lipopolysaccharide (LPS) concentrations. To measure the luciferase activity of SNHG14-WT and SNHG14-MUT transfected with miR-137 mimic or miR-NC mimic, luciferase reporter genes were utilized. The results showed that chondrocyte viability was significantly inhibited with LPS treatment and chondrocyte inflammatory response, apoptosis and extracellular matrix degradation were significantly increased. However, the above results were significantly reversed after LncRNA SNHG14 inhibition. The luciferase activity bound to miR-137 was decreased in SNHG14-WT group, but there was no change in SNHG14-mut group, which indicated that LncRNA SNHG14 inhibited miR-137 expression as a miRNA sponge. In conclusion, inhibition of LncRNA SNHG14 attenuates chondrocyte inflammatory response, apoptosis and extracellular matrix degradation by targeting miR-137 in LPS induced chondrocytes.

Hsa_circ_0007292 promotes chondrocyte injury in osteoarthritis via targeting the miR-1179/HMGB1 axis

BACKGROUND

Circular RNAs (circRNAs) have been demonstrated to participate in the progression of osteoarthritis (OA). This study aimed to investigate the role and molecular mechanism of hsa_circ_0007292 in OA.

METHODS

Hsa_circ_0007292 was identified by analyzing a circRNA microarray from the Gene Expression Omnibus (GEO) database, and its expression was detected by real-time PCR in OA cartilage tissues and interleukin (IL)-1β-induced two human chondrocytes (CHON-001 and C28/I2), the OA cell models. The effects of hsa_circ_0007292 knockdown and miR-1179 overexpression on IL-1β-induced chondrocyte injury were examined by CCK-8, BrdU, flow cytometry, ELISA, and western blot. RNA pull-down assay and dual-luciferase reporter gene assay were used to analyze the interaction between hsa_circ_0007292 and miR-1179. Rescue experiments were carried out to determine the correlations among hsa_circ_0007292, miR-1179 and high mobility group box-1 (HMGB1).

RESULTS

Hsa_circ_0007292 expression was upregulated in OA tissues and IL-1β-induced chondrocytes. Both downregulation of hsa_circ_0007292 and miR-1179 overexpression increased the proliferation and Aggrecan expression, suppressed apoptosis, matrix catabolic enzyme MMP13 expression and inflammatory factor (TNF-α, IL-6, and IL-8) levels. There was a negative correlation between hsa_circ_0007292 and miR-1179, and a positive correlation between hsa_circ_0007292 and HMGB1 in OA tissues. The mechanistic study showed that hsa_circ_0007292 prevented HMGB1 downregulation by sponging miR-1179. Upregulation of HMGB1 could reverse the influence of hsa_circ_0007292 downregulation on IL-1β-induced chondrocyte injury.

CONCLUSIONS

Downregulation of hsa_circ_0007292 relieved apoptosis, extracellular matrix degradation and inflammatory response in OA via the miR-1179/HMGB1 axis, suggesting that hsa_circ_0007292 might be a potential therapeutic target for OA treatment.

Inflammatory Process on Knee Osteoarthritis in Cyclists

Osteoarthritis is a disorder affecting the joints and is characterized by cellular stress and degradation of the extracellular matrix cartilage. It begins with the presence of micro- and macro-lesions that fail to repair properly, which can be initiated by multiple factors: genetic, developmental, metabolic, and traumatic. In the case of the knee, osteoarthritis affects the tissues of the diarthrodial joint, manifested by morphological, biochemical, and biomechanical modifications of the cells and the extracellular matrix. All this leads to remodeling, fissuring, ulceration, and loss of articular cartilage, as well as sclerosis of the subchondral bone with the production of osteophytes and subchondral cysts. The symptomatology appears at different time points and is accompanied by pain, deformation, disability, and varying degrees of local inflammation. Repetitive concentric movements, such as while cycling, can produce the microtrauma that leads to osteoarthritis. Aggravation of the gradual lesion in the cartilage matrix can evolve to an irreversible injury. The objective of the present review is to explain the evolution of knee osteoarthritis in cyclists, to show the scarce research performed in this particular field and extract recommendations to propose future therapeutic strategies.

The Role of Tocotrienol in Arthritis Management—A Scoping Review of Literature

Arthritis is a cluster of diseases impacting joint health and causing immobility and morbidity in the elderly. Among the various forms of arthritis, osteoarthritis (OA) and rheumatoid arthritis (RA) are the most common. Currently, satisfying disease-modifying agents for arthritis are not available. Given the pro-inflammatory and oxidative stress components in the pathogenesis of arthritis, tocotrienol, a family of vitamin E with both anti-inflammatory and antioxidant properties, could be joint-protective agents. This scoping review aims to provide an overview of the effects of tocotrienol on arthritis derived from the existing scientific literature. A literature search using PubMed, Scopus and Web of Science databases was conducted to identify relevant studies. Only cell culture, animal and clinical studies with primary data that align with the objective of this review were considered. The literature search uncovered eight studies investigating the effects of tocotrienol on OA (n = 4) and RA (n = 4). Most of the studies were preclinical and revealed the positive effects of tocotrienol in preserving joint structure (cartilage and bone) in models of arthritis. In particular, tocotrienol activates the self-repair mechanism of chondrocytes exposed to assaults and attenuates osteoclastogenesis associated with RA. Tocotrienol also demonstrated strong anti-inflammatory effects in RA models. The single clinical trial available in the literature showcases that palm tocotrienol could improve joint function among patients with OA. In conclusion, tocotrienol could be a potential anti-arthritic agent pending more results from clinical studies.

Metals-triggered compound CDPDP exhibits anti-arthritic behavior by downregulating the inflammatory cytokines, and modulating the oxidative storm in mice models with extensive ADMET, docking and simulation studies

Triggering through abiotic stress, including chemical triggers like heavy metals, is a new technique for drug discovery. In this research, the effect of heavy metal Nickel on actinobacteria Streptomyces sp. SH-1327 to obtain a stress-derived compound was firstly investigated. A new compound cyclo-(D)-Pro-(D)-Phe (CDPDP) was triggered from the actinobacteria strain SH-1327 with the addition of nickel ions 1 mM. The stress compound was further evaluated for its anti-oxidant, analgesic, and anti-inflammatory activity against rheumatoid arthritis through in-vitro and in-vivo assays in albino mice. A remarkable in-vitro anti-oxidant potential of CDPDP was recorded with the IC₅₀ value of 30.06 ± 5.11 μg/ml in DPPH, IC₅₀ of 18.98 ± 2.91 against NO free radicals, the IC₅₀ value of 27.15 ± 3.12 against scavenging ability and IC₅₀ value of 28.40 ± 3.14 μg/ml for iron chelation capacity. Downregulation of pro-inflammatory mediators (NO and MDA), suppressed levels of pro-inflammatory cytokines (TNF-α, IL-6, IL-Iβ) and upregulation of expressions of anti-oxidant enzymes (GSH, catalase, and GST) unveiled its anti-inflammatory potential. CDPDP was analyzed in human chondrocyte cell line CHON-001 and the results demonstrated that CDPDP significantly increased cell survival, and inhibited apoptosis of IL-1β treated chondrocytes and IL-1β induced matrix degrading markers. In addition, to evaluate the mitochondrial fitness of CHON-001 cells, CDPDP significantly upregulated pgc1-α, the master regulator of mitochondrial biogenesis, indicating that CDPDP provides protective effects in CHON-001 cells. The absorption, distribution, metabolism, excretion, and toxicity (ADMET) profile of the CDPDP showed that CDPDP is safe in cases of hepatotoxicity, cardiotoxicity, and cytochrome inhibition. Furthermore, docking results showed good binding of CDPDP with IL-6-17.4 kcal/mol, and the simulation studies proved the stability between ligand and protein. Therefore, the findings of the current study prospect CDPDP as a potent anti-oxidant and a plausible anti-arthritic agent with a strong pharmacokinetic and pharmacological profile.

Loganin attenuates interleukin-1-induced chondrocyte inflammation, cartilage degeneration, and rat synovial inflammation by regulating TLR4/MyD88/NF-κB

Objective

Inflammation plays a crucial part in osteoarthritis (OA) development. This work aimed to explore loganin’s role and molecular mechanism in inflammation and clarify its anti-inflammatory effects in OA treatment.

Methods

Chondrocytes were stimulated using interleukin (IL)-1β and loganin at two concentrations (1 μM and 10 μM). Nitric oxide (NO) and prostaglandin E2 (PGE2) expression was assessed. Real-time polymerase chain reaction was used to evaluate inducible NO synthase (iNOS), cyclooxygenase (COX)-2, IL-6, and tumor necrosis factor (TNF)-α mRNA levels. Western blot was used to investigate TLR4, MyD88, p-p65, and IκB-α expression. p65 nuclear translocation, synovial inflammatory response, and cartilage degeneration were also assessed.

Results

Loganin significantly reduced IL-1β-mediated PGE2, NO, iNOS, and COX-2 expression compared with that of the IL-1β stimulation group. The TLR4/MyD88/NF-κB pathway was suppressed by loganin, which decreased inflammatory cytokine (TNF-α and IL-6) levels compared with those of the IL-1β stimulation group. Loganin inhibited IL-1β-mediated NF-κB p65 nuclear translocation compared with that of the IL-1β stimulation group. Loganin partially suppressed cartilage degeneration and the synovial inflammatory response in vivo.

Conclusion

This work demonstrated that loganin inhibited IL-1β-mediated inflammation in rat chondrocytes through TLR4/MyD88/NF-κB pathway regulation, thereby reducing rat cartilage degeneration and the synovial inflammatory response.

Vascular injury of immature epiphyses impair stem cell engraftment in cartilage defects

The purpose of our study was to investigate if vascular injury in immature epiphyses affects cartilage repair outcomes of matrix-associated stem cell implants (MASI). Porcine bone marrow mesenchymal stromal stem cells (BMSCs) suspended in a fibrin glue scaffold were implanted into 24 full-thickness cartilage defects (5 mm ø) of the bilateral distal femur of six Göttingen minipigs (n = 12 defects in 6 knee joints of 3 immature pigs; age 3.5-4 months; n = 12 defects in 6 knee joints of 3 mature control pigs; age, 21-28 months). All pigs underwent magnetic resonance imaging (MRI) at 2, 4, 12 (n = 24 defects), and 24 weeks (n = 12 defects). After the last imaging study, pigs were sacrificed, joints explanted and evaluated with VEGF, H&E, van Gieson, Mallory, and Safranin O stains. Results of mature and immature cartilage groups were compared using the Wilcoxon signed-rank test. Quantitative scores for subchondral edema at 2 weeks were correlated with quantitative scores for cartilage repair (MOCART score and ICRS score) at 12 weeks as well as Pineda scores at end of the study, using linear regression analysis. On serial MRIs, mature joints demonstrated progressive healing of cartilage defects while immature joints demonstrated incomplete healing and damage of the subchondral bone. The MOCART score at 12 weeks was significantly higher for mature joints (79.583 ± 7.216) compared to immature joints (30.416 ± 10.543, p = 0.002). Immature cartilage demonstrated abundant microvessels while mature cartilage did not contain microvessels. Accordingly, cartilage defects in immature joints showed a significantly higher number of disrupted microvessels, subchondral edema, and angiogenesis compared to mature cartilage. Quantitative scores for subchondral edema at 2 weeks were negatively correlated with MOCART scores (r =  - 0.861) and ICRS scores (r =  - 0.901) at 12 weeks and positively correlated with Pineda scores at the end of the study (r = 0.782). Injury of epiphyseal blood vessels in immature joints leads to subchondral bone defects and limits cartilage repair after MASI.

Novel Psychoactive Substances: The Razor's Edge between Therapeutical Potential and Psychoactive Recreational Misuse

BACKGROUND

Novel psychoactive substances (NPS) are compounds of natural and synthetic origin, similar to traditional drugs of abuse. NPS are involved in a contemporary trend whose origin lies in a thinner balance between legitimate therapeutic drug research and legislative control. The contemporary NPS trend resulted from the replacement of MDMA by synthetic cathinones in 'ecstasy' during the 2000s. The most common NPS are synthetic cannabinoids and synthetic cathinones. Interestingly, during the last 50 years, these two classes of NPS have been the object of scientific research for a set of health conditions.

METHODS

Searches were conducted in the online database PubMed using boolean equations.

RESULTS

Synthetic cannabinoids displayed protective and therapeutic effects for inflammatory, neurodegenerative and oncologic pathologies, activating the immune system and reducing inflammation. Synthetic cathinones act similarly to amphetamine-type stimulants and can be used for depression and chronic fatigue.

CONCLUSIONS

Despite the scientific advances in this field of research, pharmacological application of NPS is being jeopardized by fatalities associated with their recreational use. This review addresses the scientific achievements of these two classes of NPS and the toxicological data, ending with a reflection on Illicit and NPS control frames.

Conditioned Medium of Adipose-Derived Mesenchymal Stem Cells as a Promising Candidate to Protect High Glucose-Induced Injury in Cultured C28I2 Chondrocytes

Purpose: The aim of this study was to evaluate the protective effect of conditioned medium derived from human adipose mesenchymal stem cells (CM-hADSCs) on C28I2 chondrocytes against oxidative stress and mitochondrial apoptosis induced by high glucose (HG).

Methods: C28I2 cells were pre-treated with CM-hADSCs for 24 hours followed by HG exposure (75 mM) for 48 hours. MTT assay was used to assess the cell viability. Reactive oxygen species (ROS) and lipid peroxidation were determined by 2,7-dichlorofluorescein diacetate (DCFHDA) and thiobarbituric acid reactive substances (TBARS) assays, respectively. Expressions of glutathione peroxidase 3 (GPX 3), heme oxygenase-1 (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1) were analyzed by RT-PCR. Finally, western blot analysis was used to measure Bax, Bcl-2, cleaved caspase-3, and Nrf-2 expression at protein levels.

Results: CM-hADSCs pretreatment mitigated the cytotoxic effect of HG on C28I2 viability. Treatment also markedly reduced the levels of ROS, lipid peroxidation, and augmented the expression of HO-1, NQO1, and GPx3 genes in HG-exposed group. CM-ADSCs enhanced Nrf-2 protein expression and reduced mitochondrial apoptosis through reducing Bax/Bcl-2 ratio and Caspase-3 activation.

Conclusion: MSCs, probably through its paracrine effects, declined the deleterious effect of HG on chondrocytes. Hence, therapies based on MSCs secretomes appear to be a promising therapeutic approaches to prevent joint complications in diabetic patients.

Regenerative Engineering Animal Models for Knee Osteoarthritis

Abstract

Osteoarthritis (OA) of the knee is the most common synovial joint disorder worldwide, with a growing incidence due to increasing rates of obesity and an aging population. A significant amount of research is currently being conducted to further our understanding of the pathophysiology of knee osteoarthritis to design less invasive and more effective treatment options once conservative management has failed. Regenerative engineering techniques have shown promising preclinical results in treating OA due to their innovative approaches and have emerged as a popular area of study. To investigate these therapeutics, animal models of OA have been used in preclinical trials. There are various mechanisms by which OA can be induced in the knee/stifle of animals that are classified by the etiology of the OA that they are designed to recapitulate. Thus, it is essential to utilize the correct animal model in studies that are investigating regenerative engineering techniques for proper translation of efficacy into clinical trials. This review discusses the various animal models of OA that may be used in preclinical regenerative engineering trials and the corresponding classification system.

Lay Summary

Osteoarthritis (OA) of the knee is the most common synovial joint disease worldwide, with high rates of occurrence due to an increase in obesity and an aging population. A great deal of research is currently underway to further our understanding of the causes of osteoarthritis, to design more effective treatments. The emergence of regenerative engineering has provided physicians and investigators with unique opportunities to join ideas in tackling human diseases such as OA. Once the concept is proven to work, the initial procedure for the evaluation of a treatment solution begins with an animal model. Thus, it is essential to utilize a suitable animal model that reflects the particular ailment in regenerative engineering studies for proper translation to human patients as each model has associated advantages and disadvantages. There are various ways by which OA can occur in the knee joint, which are classified according to the particular cause of the OA. This review discusses the various animal models of OA that may be used in preclinical regenerative engineering investigations and the corresponding classification system.

Recombinant platelet-derived growth factor-BB alleviates osteoarthritis in a rat model by decreasing chondrocyte apoptosis in vitro and in vivo

Osteoarthritis (OA) is a common joint disease that mainly affects the diarthrodial joints. Treatments for OA include non‐pharmacological interventions, topical and oral therapies, intra‐articular therapies and joint surgery. However, all the treatments mentioned above mainly aim to control the symptoms instead of improving or reversing the joint condition. In this research, we observed the effect of recombinant platelet‐derived growth factor (PDGF)‐BB on OA in a monosodium iodoacetate (MIA)–induced rat model and revealed the possible mechanisms. In vitro, the level of inflammation in the chondrocytes was gradually alleviated, and the apoptosis rate was gradually decreased by PDGF‐BB at increasing concentrations. The levels of p‐p38, Bax and caspase‐3 decreased, and the level of p‐Erk increased with increasing PDGF‐BB concentration. In vivo, PDGF‐BB could significantly reverse chondrocyte and matrix loss. Furthermore, high concentrations of PDGF‐BB could alleviate cartilage hyperplasia to remodel the tissue. The level of collagen II was up‐regulated, and the levels of collagen X and apoptosis were down‐regulated by increasing concentrations of PDGF‐BB. In conclusion, recombinant PDGF‐BB alleviated OA by down‐regulating caspase‐3‐dependent apoptosis. The effects of PDGF‐BB on OA mainly include inhibiting chondrocyte loss, reducing cartilage hyperplasia and osteophyte formation, and regulating collagen anabolism.

Therapeutic Prospects of Cannabinoids in the Immunomodulation of Prevalent Autoimmune Diseases

Introduction: Cannabinoids such as ▵-9-THC and CBD can downregulate the immune response by modulating the endocannabinoid system. This modulation is relevant for the treatment of prevalent autoimmune diseases (ADs), such as multiple sclerosis (MS), systemic lupus erythematosus (SLE), diabetes mellitus type 1 (DMT1), and rheumatoid arthritis (RA). These conditions require new therapeutic options with fewer side effects for the control of the autoimmune response. Objective: to conduct a literature review of preclinical scientific evidence that supports further clinical investigations for the use of cannabinoids (natural or synthetic) as potential immunomodulators of the immune response in ADs. Methodology: A systematic search was carried out in different databases using different MeSH terms, such as Cannabis sativa L., cannabinoids, immunomodulation, and ADs. Initially, 677 journal articles were found. After filtering by publication date (from 2000 to 2020 for SLE, DMT1, and RA; and 2010 to 2020 for MS) and removing the duplicate items, 200 articles were selected and analyzed by title and summary associated with the use of cannabinoids as immunomodulatory treatment for those diseases. Results: Evidence of the immunomodulatory effect of cannabinoids in the diseases previously mentioned, but SLE that did not meet the search criteria, was summarized from 24 journal articles. CBD was found to be one of the main modulators of the immune response. This molecule decreased the number of Th1 and Th17 proinflammatory cells and the production of the proinflammatory cytokines, interleukin (IL)-1, IL-12, IL-17, interferon (IFN)-γ, and tumor necrosis factor alpha, in mouse models of MS and DMT1. Additionally, new synthetic cannabinoid-like molecules, with agonist or antagonist activity on CB1, CB2, TRPV1, PPAR-α, and PPAR-γ receptors, have shown anti-inflammatory properties in MS, DMT1, and RA. Conclusion: Data from experimental animal models of AD showed that natural and synthetic cannabinoids downregulate inflammatory responses mediated by immune cells responsible for AD chronicity and progression. Although synthetic cannabinoid-like molecules were evaluated in just two clinical trials, they corroborated the potential use of cannabinoids to treat some ADs. Notwithstanding, new cannabinoid-based approaches are required to provide alternative treatments to patients affected by the large group of ADs.

Arrabidaea chica Verlot fractions reduce MIA-induced osteoarthritis progression in rat knees

This study aims to investigate the activity of n-hexane, ethyl acetate and butanol fractions obtained from Arrabidaea chica Verlot against MIA-induced osteoarthritis (OA). The antinociceptive potentials of each fraction were evaluated through a cyclooxygenase (COX) 1 and 2 inhibition test and an in vivo OA-model. In addition, toxicity assessments in the liver, spleen and kidney, as well as radiographic and histopathological knee analyses, were performed. The chemical composition of the n-hexane fraction was elucidated, and a molecular docking protocol was carried out to identify which compounds are associated with the detected bioactivity. The n-hexane A. chica fraction preferentially inhibits COX-2, with 90% inhibition observed at 10 µg/mL. The fractions also produced significant improvements in OA incapacity, motor activity and hyperalgesia parameters and in radiological knee conditions. However, concerning the histopathological evaluations, these improvements were only significant in the hexane and ethyl acetate fraction treatments, which resulted in better average scores, suggesting that these fractions slow OA-promoted joint injury progression. Histopathological organ analyses indicate that the fractions are not toxic to animals. Twenty compounds were identified in the n-hexane fraction, comprising fatty acids, terpenes and phytosterols. In silico analyses indicate the presence of favourable interactions between some of the identified compounds and the COX-2 enzyme, mainly concerning alpha-tocopherol (Vitamin E), squalene and beta-sitosterol. The findings indicate that A. chica fractions display analgesic, anti-inflammatory properties, are non-toxic and are able to slow OA progression, and may, therefore, be prioritized as natural products in OA human clinical trials.

Acteoside Counteracts Interleukin-1β-Induced Catabolic Processes through the Modulation of Mitogen-Activated Protein Kinases and the NFκB Cellular Signaling Pathway

Osteoarthritis (OA) is the most common degenerative joint disease with chronic joint pain caused by progressive degeneration of articular cartilage at synovial joints. Acteoside, a caffeoylphenylethanoid glycoside, has various biological activities such as antimicrobial, anti-inflammatory, anticancer, antioxidative, cytoprotective, and neuroprotective effect. Further, oral administration of acteoside at high dosage does not cause genotoxicity. Therefore, the aim of present study is to verify the anticatabolic effects of acteoside against osteoarthritis and its anticatabolic signaling pathway. Acteoside did not decrease the viabilities of mouse fibroblast L929 cells used as normal cells and primary rat chondrocytes. Acteoside counteracted the IL-1β-induced proteoglycan loss in the chondrocytes and articular cartilage through suppressing the expression and activation of cartilage-degrading enzyme such as matrix metalloproteinase- (MMP-) 13, MMP-1, and MMP-3. Furthermore, acteoside suppressed the expression of inflammatory mediators such as inducible nitric oxide synthase, cyclooxygenase-2, nitric oxide, and prostaglandin E2 in the primary rat chondrocytes treated with IL-1β. Subsequently, the expression of proinflammatory cytokines was decreased by acteoside in the primary rat chondrocytes treated with IL-1β. Moreover, acteoside suppressed not only the phosphorylation of mitogen-activated protein kinases in primary rat chondrocytes treated with IL-1β but also the translocation of NFκB from the cytosol to the nucleus through suppression of its phosphorylation. Oral administration of 5 and 10 mg/kg acteoside attenuated the progressive degeneration of articular cartilage in the osteoarthritic mouse model generated by destabilization of the medial meniscus. Our findings indicate that acteoside is a promising potential anticatabolic agent or supplement to attenuate or prevent progressive degeneration of articular cartilage.

miR-335-5P contributes to human osteoarthritis by targeting HBP1

MicroRNA (miR)-335-5P has the ability to regulate chondrogenic differentiation and promote chondrogenesis in mouse mesenchymal stem cells. It is also abnormally elevated in human osteoarthritic chondrocytes. However, the biological function of miR-335-5P in osteoarthritis (OA) is not well understood. The present study investigated the mechanism of miR-335-5P in the pathogenesis of OA. To investigate the effect of miR-335-5P on the pathogenesis of OA in vitro, a miR-335-5P mimic and inhibitor were transfected into chondrocytes. Cell Counting kit-8 assay and flow cytometry were used to observe the effects of miR-335-5P on chondrocyte apoptosis and the expression of cartilage-specific genes, such as aggrecan, collagen II, matrix metalloproteinase 13 and collagen X, were detected by reverse transcription-quantitative PCR and western blot analysis. Moreover, the current study assessed whether HMG-box transcription factor 1 (HBP1) is a novel target of miR-335-5P with dual luciferase reporter assays. Finally, a rescue experiment was used to prove the regulation between miR-335-5P and HBP1. The results revealed that HBP1 was a novel target of miR-335-5P, and that miR-335-5P mediated the apoptosis of chondrocytes and changes in cartilage-specific genes via targeting HBP1. Overall, the present study revealed that miR-335-5P mediated the development of OA by targeting the HBP1 gene and promoting chondrocyte apoptosis. These data suggested that miR-335-5P may be used to develop novel early-stage diagnostic and therapeutic strategies for OA.

The Role of Inflammation in the Pathogenesis of Osteoarthritis

A joint is the point of connection between two bones in our body. Inflammation of the joint leads to several diseases, including osteoarthritis, which is the concern of this review. Osteoarthritis is a common chronic debilitating joint disease mainly affecting the elderly. Several studies showed that inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. This stimulates the release of early-stage inflammatory cytokines like interleukin-1 beta (IL-1β), which in turn induces the activation of signaling pathways, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT), and mitogen-activated protein kinase (MAPK). These events, in turn, generate more inflammatory molecules. Subsequently, collagenase like matrix metalloproteinases-13 (MMP-13) will degrade the extracellular matrix. As a result, anatomical and physiological functions of the joint are altered. This review is aimed at summarizing the previous studies highlighting the involvement of inflammation in the pathogenesis of osteoarthritis.

Post-treatment of hyaluronan to decrease the apoptotic effects of carprofen in canine articular chondrocyte culture

A major concern associated with the use of drugs is their adverse side effects. Specific examples of the drugs of concern include antibiotic agents and non-steroidal anti-inflammatory drugs. Despite the presence of a high degree of efficacy for specific conditions, these drugs may deteriorate the surrounding tissues that are exposed to them. Often, carprofen is used for joint inflammation; however, it may stimulate cartilage degradation which can then lead to osteoarthritis progression. In this study, hyaluronan was combined with carprofen treatment in three different applications (pre-treatment, co-treatment and post-treatment) on normal canine chondrocytes to determine whether Hyaluronan (HA) is capable of mitigating the degree of chondrotoxicity of carprofen. Our findings revealed that carprofen at IC₂₀ (0.16 mg/mL) decreased viability and increased nitric oxide (NO) production. Importantly, carprofen induced the apoptosis of canine chondrocytes via the up-regulation of Bax, Casp3, Casp8, Casp9 and NOS2 as compared to the control group. Although the co-treatment of HA and carprofen appeared not to further alleviate the chondrotoxicity of carprofen due to the presence of a high number of apoptotic chondrocytes, post-treatment with HA (carprofen treatment for 24 h and then changed to HA for 24 h) resulted in a decrease in chondrocyte apoptosis by the down-regulation of Bax, Casp3, Casp8, Casp9, NOS2, along with NO production when compared with the treatment of carprofen for 48 h (P < 0.05). These results suggest that HA can be used as a therapeutic agent to mitigate the degree of chondrotoxicity of carprofen.

Therapeutic effect of Resveratrol in the treatment of osteoarthritis via the MALAT1/miR-9/NF-κB signaling pathway

The aim of the current study was to explore the role of Resveratrol (Res) in osteoarthritis (OA) and its underlying mechanism. Reverse transcription-quantitative polymerase chain reaction and western blot analysis were used to determine the relative expression levels of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), microRNA-9 (miR-9), nuclear factor kappa B subunit 1 (NF-κB1), interleukin (IL)-6, matrix metallopeptidase 13 (MMP-13) and caspase-3 in vitro and in the in vivo model of OA, as well as examining the effect of Res on MALAT1, miR-9 and NF-κB1, IL-6, MMP-13 and caspase-3 expression levels. Immunohistochemical analysis was performed to examine NF-κB1 and MMP-13 protein levels in the in vivo model of OA. Dual-luciferase reporter assays were used to confirm the regulatory relationship between miR-9 and MALAT1 and NF-κB1, as well as examining the effect of Res on the transcriptional activation of MALAT1 promoter. Furthermore, the effect of Res on cell proliferation in vitro was examined by MTT assay. The relative mRNA expression levels of MALAT1 and NF-κB1 were significantly increased, while miR-9 expression was significantly decreased in the OA group compared with the sham group. Treatment with Res partially reversed the effects of OA on MALAT1, NF-κB1 and miR-9 expression. Similarly, the relative protein expression levels of NF-κB1, IL-6, MMP-13 and caspase-3 were significantly increased in the OA group compared with the sham group; however, treatment with Res partially reversed the effects of OA on the protein expression levels of NF-κB1, IL-6, MMP-13 and caspase-3. MALAT1 and NF-κB1 were identified as potential target genes of miR-9, and dual-luciferase assays were used to examine the effect of miR-9 on the luciferase activity of 3'UTR MALAT1 and NF-κB1. Treatment with Res suppressed the transcriptional activation of the MALAT1 promoter, thereby inhibiting MALAT1 expression. Additionally, the relative expression level of miR-9 significantly increased following treatment with Res in a dose-dependent manner, while the relative protein expression levels of NF-κB1, IL-6, MMP-13 and caspase-3 significantly decreased following treatment with Res compared with the control. Furthermore, treatment with Res significantly increased the growth rate of chondrocytes in a dose-dependent manner compared with the control. Taken together, these results suggest that direct targeting of the MALAT1/miR-9/NF-κB1/IL-6, MMP-13/caspase-3 axis may be a novel therapeutic strategy for the treatment of OA.

Catalpol Attenuates IL-1β Induced Matrix Catabolism, Apoptosis and Inflammation in Rat Chondrocytes and Inhibits Cartilage Degeneration

BACKGROUND Chondrocyte dysfunction and apoptosis are 2 major features during the progression of osteoarthritis. Catalpol, an iridoid glycoside isolated from the root of Rehmannia, is a valuable medication with anti-inflammatory, anti-oxidative, and anti-apoptotic effects in various diseases. However, whether catalpol protects against osteoarthritis has not been investigated. MATERIAL AND METHODS To assess the role of catalpol in osteoarthritis and the potential mechanism of action, chondrocytes were treated with interleukin (IL)-1ß and various concentrations of catalpol. Catabolic metabolism, apoptotic level and relative signaling pathway were measured by western blot, real-time polymerase chain reaction and immunofluorescence staining. Meanwhile, we assess the cartilage degeneration in an experimental rat model using Safranin O fast green staining and cartilage was graded according to the Osteoarthritis Research Society International (OARSI) system. RESULTS The results showed that catalpol prevented chondrocyte apoptotic level triggered by IL-1ß, suppressed the release of catabolic enzymes, and inhibited the degradation of extracellular matrix induced by IL-1ß. Catalpol also inhibited the nuclear factor kappa B (NF-kappaB) pathway, reduced the production of inflammatory cytokines (IL-6, tumor necrosis factor-alpha) in IL-1ß-treated chondrocytes, and partially reversed cartilage degeneration in the knee joint in animal model of osteoarthritis. CONCLUSIONS Our work suggested that catalpol treatment attenuates IL-1ß-induced inflammatory response and catabolism in rat chondrocytes by inhibiting the NF-kappaB pathway, suggesting the therapeutic potential of catalpol for the treatment of osteoarthritis.

Tricetin Protects Rat Chondrocytes against IL-1β-Induced Inflammation and Apoptosis

Tricetin is a well-studied flavonoid with a wide range of pharmacological activities in cancer and inflammation. However, the ability of tricetin to ameliorate the inflammation that occurs in osteoarthritis (OA) has not been determined. This study explored the effects of tricetin on interleukin- (IL-) 1β-induced rat chondrocytes. Chondrocytes harvested from rat cartilage were incubated in vitro with tricetin in the presence of IL-1β. The expression of matrix metalloproteinase- (MMP-) 1, MMP-3, MMP-13, nitric oxide (NO), prostaglandin E2 (PGE2), Bax, and Bcl-2 was evaluated by real-time-PCR, ELISA, Griess reaction, and western blotting. Caspase-3 activity in chondrocytes was determined using a caspase-3 activity assay and MAPK pathway activity by western blotting. Tricetin decreased the expression of MMP-1, MMP-3, and MMP-13 at both the gene and protein level in IL-1β-induced rat chondrocytes. It also inhibited IL-1β-induced NO and PGE2 production, by modulating inducible NO synthase and cyclooxygenase 2 gene expression. An antiapoptotic role of tricetin involving the Bax/Bcl-2/caspase-3 pathway was also determined. The chondroprotective effect of tricetin was shown to be partly related to the suppression of the MAPK signaling pathway. The results of this study demonstrate the chondroprotective role of tricetin, based on its anticatabolic, anti-inflammatory, and antiapoptotic effects in chondrocytes. The therapeutic potential of tricetin in OA patients should be explored in future studies.

The protective effect of sinapic acid in osteoarthritis: In vitro and in vivo studies

The anti-inflammatory effect of sinapic acid (SA) has been reported in several studies. However, whether SA has the same effect on osteoarthritis (OA) has yet to be clearly elucidated. We designed a series of in vitro and in vivo procedures to verify the above conjecture. Compared with controls, SA-pretreated human chondrocytes showed lower levels of interleukin (IL)-1β-induced IL-6, prostaglandin E2 (PGE2), nitric oxide (NO) and tumour necrosis factor-α (TNF-α) in vitro. Meanwhile, SA could also reverse the degradation of type II collage and aggrecan, as well as the overproduction of matrix metalloproteinase-9 (MMP-9) and matrix metalloproteinase-13 (MMP-13), inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 and a disintegrin and metalloproteinase thrombospondin motifs (ADAMTS)-5. Furthermore, activation of nuclear factor κB (NF-κB), which was induced by IL-1β, was also inhibited by SA through the pathway of nuclear factor-erythroid 2-related factor-2 (Nrf2)/heme oxygenase 1. In vivo, SA could delay the progress of mice OA models. We propose that SA may be applied as a potential therapeutic drug in OA treatment.

Chondroprotective effect of curcumin and lecithin complex in human chondrocytes stimulated by IL-1β via an anti-inflammatory mechanism

A complex of curcumin and lecithin developed to improve the solubility of curcumin, enhanced its chondroprotective effect via an anti-inflammatory mechanism. In macrophage, proinflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, prostaglandin E2 (PGE2), and nitric oxide (NO) were quantified. In addition, the activity of nuclear factor (NF)-κB was examined. With chondrocytes, inflammatory mediators were assessed by measuring the secretion levels of IL-6, IL-8, and PGE2, also the mRNA expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Metalloproteinases (MMPs), tissue inhibitor of metalloprotease (TIMP)-1, type II collagen (COL2), proteoglycan (PG), and hyaluronic acid (HA) were measured with respect to the articulation surface. The complex promoted the anti-inflammatory effect by the inhibition of inflammatory mediators. In addition, mRNA expression levels ameliorated. Furthermore, it was effective in decreasing extracellular secretion of polypeptides, also corresponding intracellular MMPs and TIMP-1. In conclusion, the complex may be developed as a functional supplement to maintain articulation health.

Expression of pro-apoptotic markers is increased along the osteochondral junction in naturally occurring osteochondrosis

Osteochondrosis (OC) is a naturally occurring disease of the articular-epiphyseal cartilage and subchondral bone layers, leading to pain and decreased mobility. The objective of this study was to characterize gene and protein expression of apoptotic markers in chondrocytes surrounding cartilage canals and along the osteochondral junction of osteochondrosis (OC)-affected and normal cartilage, using naturally occurring disease in horses. Paraffin-embedded osteochondral samples (6 OC, 8 normal controls) and cDNA from chondrocytes captured with laser capture microdissection (4 OC, 6 normal controls) were obtained from the lateral trochlear ridge of femoropatellar joints in 14 immature horses (1–6 months of age). Equine-specific caspase-3, caspase-8, caspase-10, Fas, Bcl-2, BAG-1, TNFα, cytochrome C, thymosin-β10, and 18S mRNA expression levels were evaluated by two-step real-time quantitative PCR. Percentage of cell death was determined using the TUNEL method. Protein expression of caspase-10, Fas, cytochrome C, and thymosin-β10 was determined following immunohistochemistry. Statistical analysis was performed using the Wilcoxon rank sum test or two-sample t-test (p < 0.05). In OC samples, there was significantly increased gene expression of caspase-10, Fas, cytochrome C, and thymosin-β10 in chondrocytes along the osteochondral junction and increased Fas gene expression in chondrocytes adjacent to cartilage canals, compared to controls. In OC samples, higher matrix Fas and cytochrome C protein expression, lower mitochondrial cytochrome C protein expression, and a trend for higher cytoplasmic caspase-10 protein expression were found. Collectively, these results suggest that both extrinsic and intrinsic apoptotic pathways are activated in OC cartilage. Increased apoptosis of osteochondral junction chondrocytes may play a role in OC, based on increased gene expression of several pro-apoptotic markers in this location.

•

Pro-apoptotic marker gene expression increased in osteochondrosis cartilage

•

Extrinsic and intrinsic apoptotic pathways activated along osteochondral junction

•

Higher caspase-10, Fas, cytochrome C, and thymosin-β10 gene expression

Association between Fas/FasL gene polymorphism and musculoskeletal degenerative diseases: a meta-analysis

Background

It was reported that Fas (rs1800682, rs2234767) and FasL (rs5030772, rs763110) gene polymorphism might be related to the risk of musculoskeletal degenerative diseases (MSDD), such as osteoarthritis (OA), intervertebral disc degeneration (IVDD) and rheumatoid arthritis (RA). However, data from different studies was inconsistent. Here we aim to elaborately summarize and explore the association between the Fas (rs1800682, rs2234767) and FasL (rs5030772, rs763110) and MSDD.

Methods

Literatures were selected from PubMed, Web of Science, Embase, Scopus and Medline in English and VIP, SinoMed, Wanfang and the China National Knowledge Infrastructure (CNKI) in Chinese up to August 21, 2017. All the researches included are case-control studies about human. We calculated the pooled odds ratios (ORs) with 95% confidence intervals (95% CI) to evaluate the strengths of the associations of Fas (rs1800682, rs2234767) and FasL (rs5030772, rs763110) polymorphisms with MSDD risk.

Results

Eleven eligible studies for rs1800682 with 1930 cases and 1720 controls, 6 eligible studies for rs2234767 with 1794 cases and 1909 controls, 3 eligible studies for rs5030772 with 367 cases and 313 controls and 8 eligible studies for rs763110 with 2010 cases and 2105 controls were included in this analysis. The results showed that the G allele of Fas (rs1800682) is associated with an increased risk of IVDD in homozygote and recessive models. The G allele of Fas (rs2234767) is linked to a decreased risk of RA but an enhanced risk of OA in allele and recessive models. In addition, the T allele of FasL (rs763110) is correlated with a reduced risk of IVDD in all of models. However, no relationship was found between FasL (rs5030772) and these three types of MSDD in any models.

Conclusions

Fas (rs1800682) and FasL (rs763110) polymorphism were associated with the risk of IVDD and Fas (rs2234767) was correlated to the susceptibility of OA and RA. Fas (rs1800682) and Fas (rs2234767) are more likely to be associated with MSDD for Chinese people. FasL (rs763110) is related to the progression of MSDD for both Caucasoid and Chinese race groups. But FasL (rs5030772) might not be associated with any types of MSDD or any race groups statistically.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2057-z) contains supplementary material, which is available to authorized users.

Inflammatory Biomarker Profiling in Total Joint Arthroplasty and Its Relevance to Circulating Levels of Lubricin, a Novel Proteoglycan

Lubricin, also known as proteoglycan 4, acts as an antiadhesive and boundary lubricant to prevent cartilage damage in healthy joints. Following injury, a decrease in synovial fluid (SF) lubricin may lead to secondary osteoarthritis (OA). Inflammatory biomarkers, such as IL-1β and TNF-α, are also implicated in the pathophysiology of OA. Interestingly, they have been shown to suppress the expression and secretion of lubricin in SF. This study aims to compare circulating levels of inflammatory biomarkers and lubricin between total joint arthroplasty (TJA) patients and healthy individuals. Doing so may better elucidate their roles in OA and extend the understanding of inflammation as a regulator of lubricin. Deidentified plasma samples were obtained 1 day preoperatively and 1 day postoperatively from patients undergoing TJA. Utilizing biochip array technology, they were profiled for IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFN-γ, IL-1α, IL-1β, MCP-1, EGF, and TNF-α. Circulating lubricin levels were also measured using enzyme-linked immunosorbent assay. Compared to healthy controls, IL-6, IL-8, VEGF, IL-1β, MCP-1, EGF, and TNF-α were significantly increased pre- and postoperatively. Lubricin was significantly decreased. This may indicate that elevations in inflammatory cytokines initiate a cascade of events, leading to decreased lubricin, which places the joint at increased risk of developing OA.

Plumbagin Prevents IL-1β-Induced Inflammatory Response in Human Osteoarthritis Chondrocytes and Prevents the Progression of Osteoarthritis in Mice

Inflammation and inflammatory cytokines have been reported to play vital roles in the development of osteoarthritis (OA). Plumbagin, a quinonoid compound extracted from the roots of medicinal herbs of the Plumbago genus, has been reported to have anti-inflammatory effects. However, the anti-inflammatory effects of plumbagin on OA have not been reported. This study aimed to assess the effects of plumbagin on human OA chondrocytes and in a mouse model of OA induced by destabilization of the medial meniscus (DMM). In vitro, human OA chondrocytes were pretreated with plumbagin (2, 5, 10 μM) for 2 h and subsequently stimulated with IL-1β for 24 h. Production of NO, PGE2, MMP-1, MMP-3, and MMP-13 was evaluated by the Griess reagent and ELISAs. The messenger RNA (mRNA) expression of COX-2, iNOS, MMP-1, MMP-3, MMP-13, aggrecan, and collagen-II was measured by real-time PCR. The protein expression of COX-2, iNOS, p65, p-p65, IκBα, and p-IκBα was detected by Western blot. The protein expression of collagen-II was evaluated by immunofluorescence. In vivo, the severity of OA was determined by histological analysis. We found that plumbagin significantly inhibited the IL-1β-induced production of NO and PGE2; expression of COX-2, iNOS, MMP-1, MMP-3, and MMP-13; and degradation of aggrecan and collagen-II. Furthermore, plumbagin dramatically suppressed IL-1β-stimulated NF-κB activation. In vivo, treatment of plumbagin not only prevented the destruction of cartilage and the thickening of subchondral bone but also relieved synovitis in mice OA models. Taken together, these results suggest that plumbagin may be a potential agent in the treatment of OA.

Oleuropein inhibits the IL-1β-induced expression of inflammatory mediators by suppressing the activation of NF-κB and MAPKs in human osteoarthritis chondrocytes

Osteoarthritis (OA) is the most common form of joint disease and is widespread in the elderly population and is characterized by erosion of articular cartilage, subchondral bone sclerosis and synovitis. Oleuropein (OL), a secoiridoid, is considered as the most prevalent phenolic component in olive leaves and seeds, pulp and peel of unripe olives and has been shown to have potent anti-inflammatory effects. However, its effects on OA have not been clearly elucidated. This study aimed to assess the effect of OL on human OA chondrocytes. Human OA chondrocytes were pretreated with OL (10, 50 and 100 μM) for 2 h and subsequently stimulated with IL-1β for 24 h. The production of NO, PGE2, MMP-1, MMP-13, and ADAMTS-5 was evaluated by the Griess reaction and ELISA assays. The messenger RNA (mRNA) expression of COX-2, iNOS, MMP-1, MMP13, ADAMTS-5, aggrecan, and collagen-II was measured by using real-time PCR. The protein expressions of COX-2, iNOS, p65, IκB-α, JNK, p-JNK, ERK, p-ERK, p38, and p-p38 were tested by using western blot. We found that OL significantly inhibited the IL-1β-induced production of NO and PGE2; expression of COX-2, iNOS, MMP-1, MMP-13, and ADAMTS-5; and degradation of aggrecan and collagen-II. Furthermore, OL dramatically suppressed IL-1β-stimulated NF-κB and MAPK activation. Immunofluorescence staining demonstrated that OL could suppress IL-1β-induced phosphorylation of p65 nuclear translocation. These results indicate that the therapeutic effect of OL on OA is accomplished through the inhibition of both NF-κB and MAPK signaling pathways. Altogether, our findings provide the evidence to develop OL as a potential therapeutic agent for patients with OA.

In Vitro and In Vivo Anti-Osteoarthritis Effects of 2,3,5,4'-Tetrahydroxystilbene-2-O-β-d-Glucoside from Polygonum Multiflorum

Polygonum multiflorum Thunb. is a traditional herbal medicine that is rich in polyphenols. The major compound, 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucoside (THSG) has many pharmacological activities, such as antioxidative and free radical-scavenging properties, and the abilities to reduce hyperlipidemia, prevent lipid peroxidation, and protect the cardiovascular system. In this study, the anti-osteoarthritis (OA) effects of THSG were explored using in vitro and in vivo models. THSG inhibited nitric oxide (NO) and prostaglandin E₂ (PGE₂) production and inducible NO synthase (iNOS) and cyclooxygenase-2 expressions by lipopolysaccharide-stimulated RAW 264.7 cells. On the other hand, THSG inhibited PGE₂ production and iNOS and matrix metalloproteinase-13 expressions by interleukin-1β-stimulated primary rat chondrocytes. Through a mono-iodoacetate-induced rat OA model assay, THSG reduced paw edema and improved the weight-bearing distribution. Therefore, THSG has anti-inflammatory activity and could be applied as a lead compound for the development as an OA drug.

Pioglitazone inhibits advanced glycation end product-induced matrix metalloproteinases and apoptosis by suppressing the activation of MAPK and NF-κB

Apoptosis and degeneration coming mainly from chondrocytes are important mechanisms in the onset and progression of osteoarthritis. Specifically, advanced glycation end products (AGEs) play an important role in the pathogenesis of osteoarthritis. Pioglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist has a protective effect on cartilage. This study aims to evaluate the effect of pioglitazone on AGEs-induced chondrocyte apoptosis and degeneration and their underlying mechanism. The in vitro study shows that AGEs induce cleavage of caspase-3 and PARP, up-regulate MMP-13 expression, enhance chondrocyte apoptosis and down-regulate PPARγ expression in human primary chondrocytes, which is reversed by pioglitazone. Furthermore, AGEs activate phosphorylation of Erk, JNK, and p38, and pioglitazone reverses AGEs-induced phosphorylation of Erk and p38. AGEs-induced degradation of IκBα and translocation of nuclear NF-κB p65 is reversed by pioglitazone. Pretreatment of chondrocytes with SB202190 (p38 inhibitor), SP600125 (JNK inhibitor) and BAY-11-7082 (NF-κB inhibitor) inhibit AGEs-induced apoptosis and degeneration. In vivo experiments suggest that pioglitazone reverses AGEs-induced cartilage degeneration and apoptosis in a mouse model, as demonstrated by HE and Safranin O staining, immunohistochemical analyses of Type II collagen (Col II), metalloproteinases (MMPs) and caspase-3. These findings suggest that pioglitazone, a PPARγ agonist, inhibits AGEs-induced chondrocytes apoptosis and degeneration via suppressing the activation of MAPK and NF-κB.

Modulation of cartilage's response to injury: Can chondrocyte apoptosis be reversed?

Osteoarthritis is characterized by a chronic, progressive and irreversible degradation of the articular cartilage associated with joint inflammation and a reparative bone response. More than 100 million people are affected by this condition worldwide with significant health and welfare costs. Our available treatment options in osteoarthritis are extremely limited. Chondral or osteochondral grafts have shown some promising results but joint replacement surgery is by far the most common therapeutic approach. The difficulty lies on the limited regeneration capacity of the articular cartilage, poor blood supply and the paucity of resident progenitor stem cells. In addition, our poor understanding of the molecular signalling pathways involved in the senescence and apoptosis of chondrocytes is a major factor restricting further progress in the area. This review focuses on molecules and approaches that can be implemented to delay or even rescue chondrocyte apoptosis. Ways of modulating the physiologic response to trauma preventing chondrocyte death are proposed. The use of several cytokines, growth factors and advances made in altering several of the degenerative genetic pathways involved in chondrocyte apoptosis and degradation are also presented. The suggested approaches can help clinicians to improve cartilage tissue regeneration.

Knockdown of PRMT1 suppresses IL-1β-induced cartilage degradation and inflammatory responses in human chondrocytes through Gli1-mediated Hedgehog signaling pathway

Osteoarthritis (OA) is characterized by articular cartilage degradation and joint inflammation. The purpose of the present study is to elucidate the role of the specific function of PRMT1 in chondrocytes and its association with the pathophysiology of OA. We observed that the expression of PRMT1 was apparently upregulated in OA cartilage, as well as in chondrocytes stimulated with IL-1β. Additionally, knockdown of PRMT1 suppressed interleukin 1 beta (IL-1β)-induced extracellular matrix (ECM) metabolic imbalance by regulating the expression of MMP-13, ADAMTS-5, COL2A1, and ACAN. Furthermore, silencing of PRMT1 dramatically declined the production of prostaglandin E2 (PGE2) and nitric oxide as well as the level of pro-inflammatory cytokine IL-6 and TNF-α. Mechanistic analyses further revealed that IL-1β-induced activation of the Hedgehog/Gli-1 signaling is suppressed upon PRMT1 knockdown. However, the effects of inhibition of PRMT1-mediated IL-1β-induced cartilage matrix degradation and inflammatory response in OA chondrocytes were obviously abolished by Hedgehog agonist Purmorphamine (Pur). Our data collectively suggest that silencing of PRMT1 exerts anti-catabolic and anti-inflammatory effects on IL-1β-induced chondrocytes via suppressing the Gli-1 mediated Hedgehog signaling pathway, indicating that PRMT1 plays a critical role in OA development and serves as a promising therapeutic target for OA.

Tormentic Acid Inhibits IL-1β-Induced Inflammatory Response in Human Osteoarthritic Chondrocytes

The pro-inflammatory cytokine interleukin-1beta (IL-1β) plays critical roles in pathogenesis of osteoarthritis (OA). Tormentic acid (TA), a triterpene isolated from Rosa rugosa, has anti-inflammatory activity. However, the anti-inflammatory effect of TA on OA is still unclear. So, in the present study, we examined the effect of TA on IL-1β-induced inflammatory response in primary human OA chondrocytes. Our results demonstrated that TA significantly decreased the IL-1β-stimulated expression of matrix metalloproteinase-3 (MMP-3) and MMP-13. It also inhibited the IL-1β-induced expression of inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2), as well as the production of NO and prostaglandin E2 (PGE2) in human OA chondrocytes. Furthermore, TA greatly inhibited the IL-1β-induced NF-κB activation. In conclusion, this study is the first to demonstrate the anti-inflammatory activity of TA in human OA chondrocytes. TA significantly inhibits the IL-1β-induced inflammatory response by suppressing the NF-κB signaling pathway. Thus, TA may be a potential agent in the treatment of OA.

Electrical stimulation drives chondrogenesis of mesenchymal stem cells in the absence of exogenous growth factors

Electrical stimulation (ES) is known to guide the development and regeneration of many tissues. However, although preclinical and clinical studies have demonstrated superior effects of ES on cartilage repair, the effects of ES on chondrogenesis remain elusive. Since mesenchyme stem cells (MSCs) have high therapeutic potential for cartilage regeneration, we investigated the actions of ES during chondrogenesis of MSCs. Herein, we demonstrate for the first time that ES enhances expression levels of chondrogenic markers, such as type II collagen, aggrecan, and Sox9, and decreases type I collagen levels, thereby inducing differentiation of MSCs into hyaline chondrogenic cells without the addition of exogenous growth factors. ES also induced MSC condensation and subsequent chondrogenesis by driving Ca2+/ATP oscillations, which are known to be essential for prechondrogenic condensation. In subsequent experiments, the effects of ES on ATP oscillations and chondrogenesis were dependent on extracellular ATP signaling via P2X4 receptors, and ES induced significant increases in TGF-β1 and BMP2 expression. However, the inhibition of TGF-β signaling blocked ES-driven condensation, whereas the inhibition of BMP signaling did not, indicating that TGF-β signaling but not BMP signaling mediates ES-driven condensation. These findings may contribute to the development of electrotherapeutic strategies for cartilage repair using MSCs.

Aquaporin 1 contributes to chondrocyte apoptosis in a rat model of osteoarthritis

Aquaporins (AQPs) have been found to be associated with a number of diseases. However, the role of AQP-1 in the pathogenesis of osteoarthritis remains unclear. We previously found that AQP-1 expression was upregulated in osteoarthritic cartilage and strongly correlated with caspase-3 expression and activity. The aim of this study was to further investigate the association of AQP-1 expression with chondrocyte apoptosis in a rat model of osteoarthritis, using RNA interference to knock down AQP-1. For this purspose, 72 male Sprague-Dawley rats were randomly assigned to 3 groups as follows: the control group not treated surgically (n=24), the sham-operated group (n=24), and the osteoarthritis group (n=24). Osteoarthritis was induced by amputating the anterior cruciate ligament and medial collateral ligament and partially excising the medial meniscus. Chondrocytes from the rats with osteoarthritis were isolated and cultured. shRNAs were used to knock down AQP-1 expression in the cultured chondrocytes. The expression of AQP-1 and caspase-3 was determined by reverse transcription-quantitative polymerase chain reaction. Caspase-3 activity was measured using a caspase-3 colorimetric assay. The rats in our model of osteoarthritis exhibited severe cartilage damage. The knockdown of AQP-1 decreased caspase-3 expression and activity in the cultured chondrocytes. In addition, the expression of AQP-1 positively correlated with caspase-3 expression and activity. Thus, the findings of our study, suggest that AQP-1 promotes caspase-3 activation and thereby contributes to chondrocyte apoptosis and to the development of osteoarthritis.

Finite difference time domain model of ultrasound propagation in agarose scaffold containing collagen or chondrocytes

Measurement of ultrasound backscattering is a promising diagnostic technique for arthroscopic evaluation of articular cartilage. However, contribution of collagen and chondrocytes on ultrasound backscattering and speed of sound in cartilage is not fully understood and is experimentally difficult to study. Agarose hydrogels have been used in tissue engineering applications of cartilage. Therefore, the aim of this study was to simulate the propagation of high frequency ultrasound (40 MHz) in agarose scaffolds with varying concentrations of chondrocytes (1 to 32 × 10(6) cells/ml) and collagen (1.56-200 mg/ml) using transversely isotropic two-dimensional finite difference time domain method (FDTD). Backscatter and speed of sound were evaluated from the simulated pulse-echo and through transmission measurements, respectively. Ultrasound backscatter increased with increasing collagen and chondrocyte concentrations. Furthermore, speed of sound increased with increasing collagen concentration. However, this was not observed with increasing chondrocyte concentrations. The present study suggests that the FDTD method may have some applicability in simulations of ultrasound scattering and propagation in constructs containing collagen and chondrocytes. Findings of this study indicate the significant role of collagen and chondrocytes as ultrasound scatterers and can aid in development of modeling approaches for understanding how cartilage architecture affects to the propagation of high frequency ultrasound.

Dominant roles of Fenton reaction in sodium nitroprusside-induced chondrocyte apoptosis

Sodium nitroprusside (SNP) has been widely used as an exogenous nitric oxide (NO) donor to explore the molecular mechanism of NO-mediated chondrocyte apoptosis during the latest two decades. We have recently found that NO-independent ROS play a key role in SNP-induced apoptosis in rabbit chondrocytes. This study aims to investigate what kind of ROS and how the reliable ROS mediators mediate the SNP-induced apoptosis. Data shows that SNP and NO-exhausted SNP (SNPex) induced ROS production or cytotoxicity to identically degree. SNP induced a marked increase in iron ions, superoxide anion (O2(•-)), hydrogen peroxide (H2O2) and hydroxyl radical ((•)OH) level. H2O2 scavenger (CAT) and (•)OH scavenger (DMSO) significantly inhibited SNP-induced chondrocyte apoptosis. Iron ions chelator (DFO) entirely prevented SNP-induced chondrocyte apoptosis. In contrast, O2(•-) scavenger (SOD) and glutathione depletion agent (BSO) promoted SNP-induced cytotoxicity. K3[Fe(CN)6] exhibited no cytotoxicity, and H2O2 alone up to 250µM or iron ions alone up to 90µM is non-cytotoxic to chondrocytes. Combination of 25µM FeSO4 and 100µM H2O2 in the presence of BSO induced chondrocyte death similar to SNP treatment. Fetal bovine serum (FBS) enhanced iron ions release from SNP and the cytotoxicity of SNP. Our data shows that the extracellular Fenton reaction between iron ions released from SNP and H2O2 induced by SNP plays a key role in SNP-induced chondrocyte apoptosis. Overall, our results indicate that the potential of SNP to increase iron ions and ROS should be especially considered for some biological functions and, possibly, also for clinical applications of this drug.

Intraarticular Injection of Allogenic Mesenchymal Stem Cells has a Protective Role for the Osteoarthritis

Background:

Researchers initially proposed the substitution of apoptotic chondrocytes in the superficial cartilage by injecting mesenchymal stem cells (MSCs) intraarticularly. This effect was termed as bio-resurfacing. Little evidence supporting the treatment of osteoarthritis (OA) by the delivery of a MSC suspension exists. The aim of this study was to investigate the effects of injecting allogenic MSCs intraarticularly in a rat OA model and to evaluate the influence of immobility on the effects of this treatment.

Methods:

We established a rat knee OA model after 4 and 6 weeks and cultured primary bone marrow MSCs. A MSC suspension was injected into the articular space once per week for 3 weeks. A subgroup of knee joints was immobilized for 3 days after each injection, while the remaining joints were nonimmobilized. We used toluidine blue staining, Mankin scores, and TdT-mediated dUTP-biotin nick end labeling staining to evaluate the therapeutic effect of the injections. Comparisons between the therapy side and the control side of the knee joint were made using paired t-test, and comparisons between the immobilized and nonimmobilized subgroups were made using the unpaired t-test. A P value < 0.05 was considered significant.

Results:

The three investigative approaches revealed less degeneration on the therapy sides of the knee joints than the control sides in both the 4- and 6-week groups (P < 0.05), regardless of immobilization. No significant differences were observed between the immobilized and nonimmobilized subgroups (P > 0.05).

Conclusions:

Therapy involving the intraarticular injection of allogenic MSCs promoted cartilage repair in a rat arthritis model, and 3-day immobility after injection had little effect on this therapy.

Inflammatory mediators in osteoarthritis: A critical review of the state-of-the-art, current prospects, and future challenges

Osteoarthritis (OA) has traditionally been defined as a prototypical non-inflammatory arthropathy, but today there is compelling evidence to suggest that it has an inflammatory component. Many recent studies have shown the presence of synovitis in a large number of patients with OA and demonstrated a direct association between joint inflammation and the progression of OA. Pro-inflammatory cytokines, reactive oxygen species (ROS), nitric oxide, matrix degrading enzymes and biomechanical stress are major factors responsible for the progression of OA in synovial joints. The aim of this review is to discuss the significance of a wide range of implicated inflammatory mediators and their contribution to the progression of OA. We also discuss some of the currently available guidelines, practices, and prospects. In addition, this review argues for new innovation in methodologies and instrumentation for the non-invasive detection of inflammation in OA by modern imaging techniques. We propose that identifying early inflammatory events and targeting these alterations will help to ameliorate the major symptoms such as inflammation and pain in OA patients.

Ginsenoside Ro suppresses interleukin-1β-induced apoptosis and inflammation in rat chondrocytes by inhibiting NF-κB

This study investigated effects of Ginsenoside Ro (Ro) on interleukin-1β (IL-1β)-induced apoptosis and inflammation in rat chondrocytes. The rat chondrocytes were co-treated with IL-1β (10 ng·kg(-1)) and Ro (50, 100 and 200 μmol·L(-1)) for 48 h. Chondrocytes viability was detected by the MTT assay and Annexin V-FITC/PI dual staining assay. Caspase 3 activity was measured by using caspase 3 colorimetric assay kit. Apoptosis related proteins Bax, Bad, Bcl-xL, PCNA, p53 and phospho-p53, along with inflammation related protein MMP 3, MMP 9 and COX-2, and the expression of phospho-NF-κB p65 were assayed by western blotting analyses. Ro could improve IL-1β-induced chondrocytes viability. Ro could suppress IL-1β-induced apoptosis by inhibiting levels of Bax and Bad, decreasing p53 phosphorylation and promoting the expression of Bcl-xL and PCNA. Ro inhibited caspase 3 activity. IL-1β-induced inflammation and matrix degration were also alleviated by Ro with down-regulating the expression of MMP 3, MMP 9 and COX-2. Moreover, Ro inhibited NF-κB p65 phosphorylation induced by IL-1β. In conclusion, these results suggested Ro exerted anti-apoptosis and anti-inflammation in IL-1β-induced rat chondrocytes, which might be related to NF-κB signal pathway. Therefore, we propose that Ro might be a potential novel drug for the treatment of osteoarthritis.

Xanthan gum protects rabbit articular chondrocytes against sodium nitroprusside-induced apoptosis in vitro

We have previously reported that intra-articular injection of xanthan gum (XG) could significantly ameliorate the degree of joint cartilage degradation and pain in experimental osteoarthritis (OA) model in vivo. In this present study, we evaluated the protective effect of XG against Sodium nitroprusside (SNP)-induced rabbit articular chondrocytes apoptosis in vitro. Rabbit articular chondrocytes were incubated with various concentrations of XG for 24h prior to 0.5mmol/L SNP co-treatment for 24h. The proliferation of chondrocytes was analyzed using MTT assay. The chondrocytes early apoptosis rates were evaluated using Annexin V-FITC/PI flow cytometry. The morphology of apoptosis chondrocytes were observed by scanning electron microscopy (SEM). The loss/disruption of mitochondrial membrane potential was detected using rhodamin 123 by confocal microscope. The concentration of prostaglandin E2 (PGE2) in cell culture supernatants was evaluated using ELISA assay. The results showed that XG could significantly reverse SNP-reduced cell proliferation and inhibited cell early apoptosis rate in a dose-dependent manner. XG alleviated loss/disruption of mitochondrial membrane potential and decreased the PGE2 level of chondrocytes cell culture supernatants in SNP-induced chondrocytes. These results of the present research strongly suggest that XG can protect rabbit articular chondrocytes against SNP-induced apoptosis in vitro.

Installing and thereafter removing an aberrant prosthesis elicited opposite remodelling responses in growing mouse temporomandibular joints

Temporomandibular joint (TMJ) displays a high remodelling capability. The current purpose was to investigate the differences between mandibular condylar remodelling responses of growing mice to installation and removal of unilateral anterior crossbite (UAC) prosthesis. Twenty-four mice were divided into one mock control group and two UAC groups. Unilateral anterior crossbite was created by installing a pair of prosthesis to left-side maxillary and mandibular incisors. Unilateral anterior crossbite was removed in removal group at 3 weeks but remained in UAC group. Temporomandibular joints were sampled at 7 weeks. Changes in condylar cartilage and subchondral bone were assessed by histology and in vivo micro-CT. Real-time PCR and immunohistochemistry were performed to evaluate expression changes in ADAMTS-5, MMP-3, MMP-9, MMP-13, IL-1, TNF-α, OPG and RANKL. Statistical analysis was performed at α = 0.05. Temporomandibular joint cartilage degradation was induced by UAC as previously reported but was reversed by removal of UAC. The dropped cartilage thickness, chondrocyte number and collagen II-positive area, the increased expression levels of Adamts-5, Mmp3, 9, 13, Tnf-α and Il-1β in cartilage, the decreased ratio of OPG/RANKL in both condylar cartilage and subchondral bone, the loss of TMJ subchondral bone and the increase in the TRAP-positive cells in subchondral bone were all reversed in the removal group (P < 0.05). The growing mouse TMJ condyle displays a high remodelling capability which can be degenerative and rehabilitative, respectively, in response to placement and thereafter removal of the aberrant prosthesis. Eliminating aberrant prosthesis is helpful to promote the degraded condyle to recover.

Disruption of cell-cell contact-mediated notch signaling via hydrogel encapsulation reduces mesenchymal stem cell chondrogenic potential: winner of the Society for Biomaterials Student Award in the Undergraduate Category, Charlotte, NC, April 15 to 18, 2015

Cell-cell contact-mediated Notch signaling is essential for mesenchymal stem cell (MSC) chondrogenesis during development. However, subsequent deactivation of Notch signaling is also required to allow for stem cell chondrogenic progression. Recent literature has shown that Notch signaling can also influence Wnt/β-catenin signaling, critical for MSC differentiation, through perturbations in cell-cell contacts. Traditionally, abundant cell-cell contacts, consistent with development, are emulated in vitro using pellet cultures for chondrogenesis. However, cells are often encapsulated within biomaterials-based scaffolds, such as hydrogels, to improve therapeutic cell localization in vivo. To explore the role of Notch and Wnt/β-catenin signaling in the context of hydrogel-encapsulated MSC chondrogenesis, we compared signaling and differentiation capacity of MSCs in both hydrogels and traditional pellet cultures. We demonstrate that encapsulation within poly(ethylene glycol) hydrogels reduces cell-cell contacts, and both Notch (7.5-fold) and Wnt/β-catenin (84.7-fold) pathway activation. Finally, we demonstrate that following establishment of cell-cell contacts and transient Notch signaling in pellet cultures, followed by Notch signaling deactivation, resulted in a 1.5-fold increase in MSC chondrogenesis. Taken together, these findings support that cellular condensation, and establishment of initial cell-cell contacts is critical for MSC chondrogenesis, and this process is inhibited by hydrogel encapsulation.