Oxidative stress-induced apoptosis and matrix loss of chondrocytes is inhibited by eicosapentaenoic acid

Krüppel-like factors family in health and disease

Krüppel-like factors (KLFs) are a family of basic transcription factors with three conserved Cys2/His2 zinc finger domains located in their C-terminal regions. It is acknowledged that KLFs exert complicated effects on cell proliferation, differentiation, survival, and responses to stimuli. Dysregulation of KLFs is associated with a range of diseases including cardiovascular disorders, metabolic diseases, autoimmune conditions, cancer, and neurodegenerative diseases. Their multidimensional roles in modulating critical pathways underscore the significance in both physiological and pathological contexts. Recent research also emphasizes their crucial involvement and complex interplay in the skeletal system. Despite the substantial progress in understanding KLFs and their roles in various cellular processes, several research gaps remain. Here, we elucidated the multifaceted capabilities of KLFs on body health and diseases via various compliable signaling pathways. The associations between KLFs and cellular energy metabolism and epigenetic modification during bone reconstruction have also been summarized. This review helps us better understand the coupling effects and their pivotal functions in multiple systems and detailed mechanisms of bone remodeling and develop potential therapeutic strategies for the clinical treatment of pathological diseases by targeting the KLF family.

Nutritional Epigenomics: Bioactive Dietary Compounds in the Epigenetic Regulation of Osteoarthritis

Nutritional epigenomics is exceptionally important because it describes the complex interactions among food compounds and epigenome modifications. Phytonutrients or bioactive compounds, which are secondary metabolites of plants, can protect against osteoarthritis by suppressing the expression of inflammatory and catabolic mediators, modulating epigenetic changes in DNA methylation, and the histone or chromatin remodelling of key inflammatory genes and noncoding RNAs. The combination of natural epigenetic modulators is crucial because of their additive and synergistic effects, safety and therapeutic efficacy, and lower adverse effects than conventional pharmacology in the treatment of osteoarthritis. In this review, we have summarized the chondroprotective properties of bioactive compounds used for the management, treatment, or prevention of osteoarthritis in both human and animal studies. However, further research is needed into bioactive compounds used as epigenetic modulators in osteoarthritis, in order to determine their potential value for future clinical applications in osteoarthritic patients as well as their relation with the genomic and nutritional environment, in order to personalize food and nutrition together with disease prevention.

Protective Effect of Knee Postoperative Fluid on Oxidative-Induced Damage in Human Knee Articular Chondrocytes

The oxidative-stress-elicited deterioration of chondrocyte function is the initial stage of changes leading to the disruption of cartilage homeostasis. These changes entail a series of catabolic damages mediated by proinflammatory cytokines, MMPs, and aggrecanases, which increase ROS generation. Such uncontrolled ROS production, inadequately balanced by the cellular antioxidant capacity, eventually contributes to the development and progression of chondropathies. Several pieces of evidence show that different growth factors, single or combined, as well as anti-inflammatory cytokines and chemokines, can stimulate chondrogenesis and improve cartilage repair and regeneration. In this view, hypothesizing a potential growth-factor-associated action, we investigate the possible protective effect of post-operation knee fluid from patients undergoing prosthesis replacement surgery against ROS-induced damage on normal human knee articular chondrocytes (HKACs). To this end, HKACs were pre-treated with post-operation knee fluid and then exposed to H2O2 to mimic oxidative stress. Intracellular ROS levels were measured by using the molecular probe H2DCFDA; cytosolic and mitochondrial oxidative status were assessed by using HKACs infected with lentiviral particles harboring the redox-sensing green fluorescent protein (roGFP); and cell proliferation was determined by measuring the rate of DNA synthesis with BrdU incorporation. Moreover, superoxide dismutase (SOD), catalase, and glutathione levels from the cell lysates of treated cells were also measured. Postoperative peripheral blood sera from the same patients were used as controls. Our study shows that post-operation knee fluid can counteract H2O2-elicited oxidative stress by decreasing the intracellular ROS levels, preserving the cytosolic and mitochondrial redox status, maintaining the proliferation of oxidatively stressed HKACs, and upregulating chondrocyte antioxidant defense. Overall, our results support and propose an important effect of post-operation knee fluid substances in maintaining HKAC function by mediating cell antioxidative system upregulation and protecting cells from oxidative stress.

P53: A Key Target in the Development of Osteoarthritis

Osteoarthritis (OA), a chronic degenerative disease characterized mainly by damage to the articular cartilage, is increasingly relevant to the pathological processes of senescence, apoptosis, autophagy, proliferation, and differentiation of chondrocytes. Clinical strategies for osteoarthritis can only improve symptoms and even along with side effects due to age, sex, disease, and other factors. Therefore, there is an urgent need to identify new ideas and targets for current clinical treatment. The tumor suppressor gene p53, which has been identified as a potential target for tumor therapeutic intervention, is responsible for the direct induction of the pathological processes involved in OA modulation. Consequently, deciphering the characteristics of p53 in chondrocytes is essential for investigating OA pathogenesis due to p53 regulation in an array of signaling pathways. This review highlights the effects of p53 on senescence, apoptosis, and autophagy of chondrocytes and its role in the development of OA. It also elucidates the underlying mechanism of p53 regulation in OA, which may help provide a novel strategies for the clinical treatment of OA.

Comparative RNA-sequencing analysis of the prostate in a mouse model of benign prostatic hyperplasia with bladder outlet obstruction

In ageing men, benign prostatic hyperplasia (BPH) is a chronic disease that leads to progressive lower urinary tract symptoms (LUTS) caused by obstruction of the bladder outlet (BOO). Patients with LUTS (such as increased frequency and urgency of urination) and complications of BOO (such as hydronephrosis and bladder stones) are at risk of serious health problems. BPH causes a rapidly rising burden of LUTS far exceeding that of other urological conditions. Treatment outcomes are unsatisfactory for BPH largely due to the lacking of fully understanding of the pathogenesis. Hormonal imbalances related to androgen and oestrogen can cause BPH, but the exact mechanism is still unknown, even the animal model is not fully understood. Additionally, there are no large-scale data to explain this mechanism. A BPH mouse model was established using mixed slow-release pellets of testosterone (T) and estradiol (E2), and we measured gene expression in mouse prostate tissue using RNA-seq, verified the results using qRT‒PCR, and used bioinformatics methods to analyse the differentially expressed genes (DEGs).

The Role of Polyunsaturated Fatty Acids in Osteoarthritis: Insights from a Mendelian Randomization Study

The prior observational research on the impact of polyunsaturated fatty acid (PUFA) supplementation on osteoarthritis (OA) patients had yielded inclusive outcomes. This study utilized the Mendelian randomization (MR) approach to explore potential causal relationships between PUFAs and OA. The MR study was performed using GWAS summary statistics for PUFAs, encompassing omega-3 and omega-6 fatty acids, and for knee OA (KOA) and hip OA (HOA). The primary inverse-variance-weighted (IVW) method and two supplementary MR approaches were used to establish robust causality. Heterogeneity and horizontal pleiotropy were assessed using Cochrane's Q and MR-Egger intercept tests. Additionally, a range of sensitivity analyses were conducted to strengthen the precision and reliability of the results. The IVW method indicated a potential genetic association between omega-3 fatty acids and KOA risk (odd ratio (OR) = 0.94, 95% confidence interval (CI): 0.89-1.00, p = 0.048). No significant correlation was found between omega-3 levels and HOA. Moreover, genetically predicted higher levels of omega-6 fatty acids were associated with a decreased risk of KOA (OR = 0. 93, 95% CI: 0.86-1.00, p = 0.041) and HOA (OR = 0.89, 95% CI: 0.82-0.96; p = 0.003). The MR-Egger intercept evaluation showed no horizontal pleiotropy affecting the MR analysis (all p  >  0.05). Our findings supported the causal relationship between PUFAs and OA susceptibility and offered a novel insight that high omega-6 fatty acids may reduce the risk of KOA and HOA. These results underscore the importance of maintaining optimal levels of PUFAs, particularly omega-6 fatty acids, in individuals with a genetic predisposition to OA. Future research is necessary to validate these findings and elucidate the underlying mechanisms involved.

Targeting the Inflammatory Hallmarks of Obesity-Associated Osteoarthritis: Towards Nutraceutical-Oriented Preventive and Complementary Therapeutic Strategies Based on n-3 Polyunsaturated Fatty Acids

Obesity (Ob), which has dramatically increased in the last decade, is one of the main risk factors that contribute to the incidence and progression of osteoarthritis (OA). Targeting the characteristics of obesity-associated osteoarthritis (ObOA) may offer new chances for precision medicine strategies in this patient cohort. First, this review outlines how the medical perspective of ObOA has shifted from a focus on biomechanics to the significant contribution of inflammation, mainly mediated by changes in the adipose tissue metabolism through the release of adipokines and the modification of fatty acid (FA) compositions in joint tissues. Preclinical and clinical studies on n-3 polyunsaturated FAs (PUFAs) are critically reviewed to outline the strengths and weaknesses of n-3 PUFAs' role in alleviating inflammatory, catabolic and painful processes. Emphasis is placed on potential preventive and therapeutic nutritional strategies based on n-3 PUFAs, with a focus on ObOA patients who could specifically benefit from reformulating the dietary composition of FAs towards a protective phenotype. Finally, tissue engineering approaches that involve the delivery of n-3 PUFAs directly into the joint are explored to address the perspectives and current limitations, such as safety and stability issues, for implementing preventive and therapeutic strategies based on dietary compounds in ObOA patients.

Effect of omega-3 polyunsaturated fatty acids supplementation for patients with osteoarthritis: a meta-analysis

BACKGROUND

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) confers anti-inflammatory efficacy, which has been suggested to be effective for patients with osteoarthritis (OA). However, previous studies evaluating the influence of n-3 PUFAs supplementation in patients with OA showed inconsistent results. We performed a systematic review and meta-analysis to comprehensively evaluate the influence of n-3 PUFAs on symptom and joint function of patients with OA.

METHODS

Relevant randomized controlled trials (RCTs) were obtained by searching PubMed, Embase, and Cochrane Library databases. A random-effects model was employed to combine the results.

RESULTS

Nine RCTs with 2070 patients with OA contributed to the meta-analysis. Pooled results showed that n-3 PUFAs supplementation could significantly relieve the arthritis pain as compared to placebo (standardized mean difference [SMD]: - 0.29, 95% confidence interval [CI] - 0.47 to - 0.11, p = 0.002, I² = 60%). Besides, supplementation with n-3 PUFAs was also associated with improved joint function (SMD: - 0.21, 95% CI - 0.34 to - 0.07, p = 0.002, I² = 27%). Subgroup analysis showed consistent results of studies with arthritis pain and joint function evaluated by the Western Ontario-McMaster University Osteoarthritis Index and other scales (p for subgroup difference = 0.33 and 0.34, respectively). No severe treatment-related adverse events (AEs) were observed in the included patients, and the incidence of overall AEs was similar between groups (odds ratio: 0.97, 95% CI 0.64-1.45, p = 0.86, I² = 0%).

CONCLUSIONS

Supplementation of n-3 PUFAs is effective to relieve pain and improve joint function in patients with OA.

Baicalin Relieves LPS-Induced Lung Inflammation via the NF-κB and MAPK Pathways

Baicalin is an active ingredient extracted from the Chinese medicine Scutellaria and has many beneficial effects. Pulmonary interstitial and alveolar edema are common symptoms of an acute lung injury (ALI). We investigated the effects of baicalin on LPS-induced inflammation and the underlying mechanisms in mice and cells. The protein contents and mRNA expression of TNF-α, IL-1β, and IL-6 in RAW264.7 cells and mice were detected using ELISA and qRT-PCR. Baicalin significantly suppressed TNF-α, IL-1β, and IL-6 levels and expression, both in vitro and in vivo, compared with the LPS group. Baicalin inhibits the expression of TLR4 and MyD88, resulting in significant decreases in p-p65, p-p38, p-ERK, and p-JNK, as measured by the Western blotting of RAW264.7 cells. A baicalin treatment for 12 h resulted in a rapid increasing of the white blood cell number and significantly improved the pathological changes in the lung. We also found that the baicalin pretreatment for 12 h could decrease the MPO content and wet/dry (W/D) weight ratio, which indicates that baicalin can significantly reduce pulmonary edema. Furthermore, the baicalin pretreatment also resulted in the recovery of TGF-β protein levels and decreased iNOS. Baicalin inhibits ALI inflammation in mice and cells and is a potential candidate for the treatment of ALI.

A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis

With osteoarthritis being the most common degenerative disease in pet animals, a very broad panel of natural health products is available on the market for its management. The aim of this systematic review and meta-analysis, registered on PROSPERO (CRD42021279368), was to test for the evidence of clinical analgesia efficacy of fortified foods and nutraceuticals administered in dogs and cats affected by osteoarthritis. In four electronic bibliographic databases, 1578 publications were retrieved plus 20 additional publications from internal sources. Fifty-seven articles were included, comprising 72 trials divided into nine different categories of natural health compound. The efficacy assessment, associated to the level of quality of each trial, presented an evident clinical analgesic efficacy for omega-3-enriched diets, omega-3 supplements and cannabidiol (to a lesser degree). Our analyses showed a weak efficacy of collagen and a very marked non-effect of chondroitin-glucosamine nutraceuticals, which leads us to recommend that the latter products should no longer be recommended for pain management in canine and feline osteoarthritis.

Enhanced Extracellular Matrix Degradation in Growth Plate Contributes to Manganese Deficiency-Induced Tibial Dyschondroplasia in Broiler Chicks

Manganese (Mn) is a crucial trace element for poultry nutrition, and its deficiency compromises tibial cartilage development, leading to perosis and a higher incidence of slipped tendon. Tibial dyschondroplasia (TD) is a metabolic cartilage disease characterized by disruption of endochondral bone formation, which is closely related to extracellular matrix (ECM) degradation, in which Mn deficiency plays an important role. Previous studies have confirmed the role of matrix metalloproteinases (MMPs) in the pathogenesis of TD, but whether dysregulated ECM degradation and MMP expression profiles in growth plate are involved in Mn deficiency-induced avian TD has not been fully elucidated yet. Thus, this study was conducted to clarify these issues. Firstly, we successfully established TD model induced by Mn deficiency in broiler chicks. Mn deficiency decreased the number of chondrocytes, contents of proteoglycan, and type II collagen in tibial growth plate, demonstrating the tibial growth plate damage with enhanced ECM degradation. Also, Mn deficiency inhibited the Nrf2 signaling pathway and enhanced the protein levels of NLRP3, active caspase-1, and active IL-1β in tibial growth plate, indicating the oxidative stress and inflammatory response in Mn deficiency-induced TD. Additionally, upregulated expression levels of MMPs (MMP1, 9, and 13) were observed in tibial growth plate of Mn deficiency group. In summary, these findings suggest that Mn deficiency-enhanced ECM degradation is involved in avian TD, which may be correlated with oxidative stress, inflammatory response, and upregulation of MMPs.

The protective effect of mangiferin on osteoarthritis: An in vitro and in vivo study

Mangiferin is a kind of polyphenol chemical compound separated from these herbal medicines of Mangifera indica L., Anemarrhena asphodeloides Bge. and Belamcanda chinensis L., which has anti-inflammatory, anti-virus, and other physiological activities without toxic effects. Osteoarthritis (OA) is a chronic disease that is also a kind of arthritis disease in which articular cartilage or bones under the joint is damaged. In addition, artificial replacements are required in severe cases. At present, there are not too much researches on the potential biological activities of mangiferin that plays a protective role in the treatment of OA. In this study, we evaluated the protective effect of mangiferin on osteoarthritis (OA) in vitro and in vivo. First, the effect of different concentrations of mangiferin on rat chondrocytes was determined by MTT assay. Second, the effects of mangiferin on the expression levels of matrix metalloproteinase (MMP)-13, TNF alpha, Collagen II, Caspase-3, and cystatin-C in interleukin-1beta (IL-1beta)-induced rat chondrocytes were examined by the real-time polymerase chain reaction in vitro, meanwhile the effects of mangiferin on the nuclear factor kappa-B (NF-kappaB) signaling pathway were also investigated by Western Blot. Finally, the anti-osteoarthritic protective effect of mangiferin was evaluated in the rat model by anterior cruciate ligament transection (ACLT) combined with bilateral ovariectomy-induced OA in vivo. The results showed that the mangiferin was found to inhibit the expression of MMP-13, TNF-alpha, and Caspase-3 which also increased the expression of Collagen II and cystatin-C in IL 1beta induced rat chondrocytes. In addition, IL-1beta-induced activation of nuclear factor kappa-B (NF-kappaB) and the degradation of inhibitor of kappaB (IkappaB)-alpha were suppressed by mangiferin. For the in vivo study in a rat model of OA, 100 microl of mangiferin was administered by intra-articular injections for rats, the results showed that the cartilage degradation was suppressed by mangiferin through Micro CT and Histological Examination. According to both in vitro and in vivo results, mangiferin has a protective effect in the treatment of OA which may be a promising therapeutic agent for OA.

Potential modulatory mechanisms of action by long-chain polyunsaturated fatty acids on bone cell and chondrocyte metabolism

Long-chain polyunsaturated fatty acids (LCPUFAs) and their metabolites are considered essential factors to support bone and joint health. The n-6 PUFAs suppress the osteoblasts differentiation via increasing peroxisome proliferator-activated receptor gamma (PPARγ) expression and promoting adipogenesis while n-3 PUFAs promote osteoblastogenesis by down-regulating PPARγ and enhancing osteoblastic activity. Arachidonic acid (AA) and its metabolite prostaglandin E2 (PGE2) are key regulators of osteoclast differentiation via induction of the receptor activator of nuclear factor kappa-Β ligand (RANKL) pathway. Marine-derived n-3 LCPUFAs have been shown to inhibit osteoclastogenesis by decreasing the osteoprotegerin (OPG)/RANKL signalling pathway mediated by a reduction of pro-inflammatory PGE2 derived from AA. Omega-3 PUFAs reduce the expression of cartilage degrading enzyme matrix metalloproteinase-13 (MMP-13) and a disintegrin and metalloprotease with thrombospondin motifs-5 (ADAMTS-5) protein, oxidative stress and thereby apoptosis via nuclear factor kappa-betta (NF-kβ) and inducible nitric oxide synthase (iNOS) pathways. In this review, a diverse range of important effects of LCPUFAs on bone cells and chondrocyte was highlighted through different mechanisms of action established by cell cultures and animal studies. This review allows a better understanding of the possible role of LCPUFAs in bone and chondrocyte metabolism as potential therapeutics in combating the pathological complications such as osteoporosis and osteoarthritis.

Iron Chelator Induces Apoptosis in Osteosarcoma Cells by Disrupting Intracellular Iron Homeostasis and Activating the MAPK Pathway

Osteosarcoma is a common malignant bone tumor in clinical orthopedics. Iron chelators have inhibitory effects on many cancers, but their effects and mechanisms in osteosarcoma are still uncertain. Our in vitro results show that deferoxamine (DFO) and deferasirox (DFX), two iron chelators, significantly inhibited the proliferation of osteosarcoma cells (MG-63, MNNG/HOS and K7M2). The viability of osteosarcoma cells was decreased by DFO and DFX in a concentration-dependent manner. DFO and DFX generated reactive oxygen species (ROS), altered iron metabolism and triggered apoptosis in osteosarcoma cells. Iron chelator-induced apoptosis was due to the activation of the MAPK signaling pathway, with increased phosphorylation levels of JNK, p38 and ERK, and ROS generation; in this process, the expression of C-caspase-3 and C-PARP increased. In an orthotopic osteosarcoma transplantation model, iron chelators (20 mg/kg every day, Ip, for 14 days) significantly inhibited the growth of the tumor. Immunohistochemical analysis showed that iron metabolism was altered, apoptosis was promoted, and malignant proliferation was reduced with iron chelators in the tumor tissues. In conclusion, we observed that iron chelators induced apoptosis in osteosarcoma by activating the ROS-related MAPK signaling pathway. Because iron is crucial for cell proliferation, iron chelators may provide a novel therapeutic strategy for osteosarcoma.

Fatty Acids and Oxylipins in Osteoarthritis and Rheumatoid Arthritis-a Complex Field with Significant Potential for Future Treatments

Purpose of Review

Osteoarthritis (OA) and rheumatoid arthritis (RA) are characterized by abnormal lipid metabolism manifested as altered fatty acid (FA) profiles of synovial fluid and tissues and in the way dietary FA supplements can influence the symptoms of especially RA. In addition to classic eicosanoids, the potential roles of polyunsaturated FA (PUFA)-derived specialized pro-resolving lipid mediators (SPM) have become the focus of intensive research. Here, we summarize the current state of knowledge of the roles of FA and oxylipins in the degradation or protection of synovial joints.

Recent Findings

There exists discordance between the large body of literature from cell culture and animal experiments on the adverse and beneficial effects of individual FA and the lack of effective treatments for joint destruction in OA and RA patients. Saturated 16:0 and 18:0 induce mostly deleterious effects, while long-chain n-3 PUFA, especially 20:5n-3, have positive influence on joint health. The situation can be more complex for n-6 PUFA, such as 18:2n-6, 20:4n-6, and its derivative prostaglandin E₂, with a combination of potentially adverse and beneficial effects. SPM analogs have future potential as analgesics for arthritic pain.

Summary

Alterations in FA profiles and their potential implications in SPM production may affect joint lubrication, synovial inflammation, pannus formation, as well as cartilage and bone degradation and contribute to the pathogeneses of inflammatory joint diseases. Further research directions include high-quality randomized controlled trials on dietary FA supplements and investigations on the significance of lipid composition of microvesicle membrane and cargo in joint diseases.

Polysaccharide from Angelica sinensis attenuates SNP-induced apoptosis in osteoarthritis chondrocytes by inducing autophagy via the ERK1/2 pathway

OBJECTIVE

Chondrocyte apoptosis plays a vital role in osteoarthritis (OA) progression. Angelica sinensis polysaccharide (ASP), a traditional Chinese medicine, possesses anti-inflammatory and anti-apoptotic properties in chondrocytes. This study aimed to determine the protective role of ASP on sodium nitroprusside (SNP)-induced chondrocyte apoptosis, and explore the underlying mechanism.

METHOD

Human primary chondrocytes isolated from the articular cartilage of OA patients were treated with SNP alone or in combination with different doses of ASP. Cell viability and apoptosis were assessed, and apoptosis-related proteins including Bcl-2 and Bax were detected. Autophagy levels were evaluated by light chain 3 (LC3) II immunofluorescence staining, mRFP-GFP-LC3 fluorescence localization, and western blot (LC3II, p62, Beclin-1, Atg5). Meanwhile, activation of the ERK 1/2 pathway was determined by western blot. The autophagy inhibitors, 3-methyladenine (3-MA), chloroquine (CQ), and a specific inhibitor of ERK1/2, SCH772984, were used to confirm the autophagic effect of ASP.

RESULTS

The results showed that SNP-induced chondrocyte apoptosis was significantly rescued by ASP, whereas ASP alone promoted chondrocyte proliferation. The anti-apoptotic effect of ASP was related to the enhanced autophagy and depended on the activation of the ERK1/2 pathway.

CONCLUSION

ASP markedly rescued SNP-induced apoptosis by activating ERK1/2-dependent autophagy in chondrocytes, and it made ASP as a potential therapeutic supplementation for OA treatment.

Gelatin hydrogels with eicosapentaenoic acid can prevent osteoarthritis progression in vivo in a mouse model

Eicosapentanoic acid (EPA) is an antioxidant and omega-3 polyunsaturated fatty acid that reduces inflammatory cytokine production. Gelatin hydrogel can be used as a carrier of a physiologically active substance that release it gradually for an average of ~3 weeks. Therefore, this study aimed to clarify the effect of EPA-incorporating gelatin hydrogels on osteoarthritis (OA) progression in vivo. Ten-week-old male C57BL/6J mice were randomly divided into six groups (n = 6): Sham, destabilization of the medial meniscus (DMM), Corn: DMM + 2 µL corn oil, EPA injection alone (EPA-I): DMM + 2 µL corn oil + 125 μg/μL EPA, Gel: DMM + gelatin hydrogels, and EPA-G: DMM + 125 μg/μL EPA-incorporating gelatin hydrogels. The mice were euthanized at 8 weeks after DMM or Sham surgery, and subjected to histological evaluation. Matrix-metalloproteinases-3 (MMP-3), MMP-13, interleukin-1β (IL-1β), p-IKK α/β, CD86, and CD163 protein expression in the synovial cartilage was detected by immunohistochemical staining. F4/80 expression was also assessed using the F4/80 score of macrophage. Histological score was significantly lower in EPA-G than in EPA-I. MMP-3-, MMP-13-, IL-1β-, and p-IKK α/β-positive cell ratio was significantly lower in EPA-G than in EPA-I. However, CD86- and CD163-positive cell ratio was not significantly different between EPA-I and EPA-G. The average-sum F4/80 score of macrophage in EPA-G was significantly lower than that in EPA-I. EPA-incorporating gelatin hydrogels were shown to prevent OA progression in vivo more effectively than EPA injection alone. Our results suggested that intra-articular administration of controlled-release EPA can be a new therapeutic approach for treating OA.

Hyaluronic Acid Loaded with Cerium Oxide Nanoparticles as Antioxidant in Hydrogen Peroxide Induced Chondrocytes Injury: An In Vitro Osteoarthritis Model

Osteoarthritis (OA) is the most common joint disease type and is accompanied by varying degrees of functional limitation. Both hyaluronic acid (HA) joint injections and pain relievers are efficient treatments for early-stage osteoarthritis. However, for the decomposition by hyaluronidase and free radicals in the knee joint, HA injection treatment has limited effect time. The cerium oxide nanoparticles (CeO₂) is a long time free radical scavenger. CeO₂ combined with HA expected, may extend the HA decomposition time and have a positive effect on osteoarthritis therapy. In this study, CeO₂ was successfully synthesized using the hydrothermal method with a particle size of about 120 nm, which possessed excellent dispersibility in the culture medium. The in vitro OA model was established by cell treated with H₂O₂ for 30 min. Our study found that the inhibition of chondrocyte proliferation dose-dependently increased with H₂O₂ concentration but was significantly decreased by supplementation of cerium oxide nanoparticles. COL2a1 and ACAN gene expression in chondrocytes was significantly decreased after H₂O₂ treatment; however, the tendency was changed after cerium oxide nanoparticles treatment, which suggested that damaged chondrocytes were protected against oxidative stress. These findings suggest that cerium oxide nanoparticles are potential therapeutic applications in the early stage of OA.

Nutraceutical Activity in Osteoarthritis Biology: A Focus on the Nutrigenomic Role

Osteoarthritis (OA) is a disease associated to age or conditions that precipitate aging of articular cartilage, a post-mitotic tissue that remains functional until the failure of major homeostatic mechanisms. OA severely impacts the national health system costs and patients' quality of life because of pain and disability. It is a whole-joint disease sustained by inflammatory and oxidative signaling pathways and marked epigenetic changes responsible for catabolism of the cartilage extracellular matrix. OA usually progresses until its severity requires joint arthroplasty. To delay this progression and to improve symptoms, a wide range of naturally derived compounds have been proposed and are summarized in this review. Preclinical in vitro and in vivo studies have provided proof of principle that many of these nutraceuticals are able to exert pleiotropic and synergistic effects and effectively counteract OA pathogenesis by exerting both anti-inflammatory and antioxidant activities and by tuning major OA-related signaling pathways. The latter are the basis for the nutrigenomic role played by some of these compounds, given the marked changes in the transcriptome, miRNome, and methylome. Ongoing and future clinical trials will hopefully confirm the disease-modifying ability of these bioactive molecules in OA patients.

Therapeutic potentials and modulatory mechanisms of fatty acids in bone

Bone metabolism is a lifelong process that includes bone formation and resorption. Osteoblasts and osteoclasts are the predominant cell types associated with bone metabolism, which is facilitated by other cells such as bone marrow mesenchymal stem cells (BMMSCs), osteocytes and chondrocytes. As an important component in our daily diet, fatty acids are mainly categorized as long-chain fatty acids including polyunsaturated fatty acids (LCPUFAs), monounsaturated fatty acids (LCMUFAs), saturated fatty acids (LCSFAs), medium-/short-chain fatty acids (MCFAs/SCFAs) as well as their metabolites. Fatty acids are closely associated with bone metabolism and associated bone disorders. In this review, we summarized the important roles and potential therapeutic implications of fatty acids in multiple bone disorders, reviewed the diverse range of critical effects displayed by fatty acids on bone metabolism, and elucidated their modulatory roles and mechanisms on specific bone cell types. The evidence supporting close implications of fatty acids in bone metabolism and disorders suggests fatty acids as potential therapeutic and nutritional agents for the treatment and prevention of metabolic bone diseases.

Association between Extracellular Matrix Accumulation and Oxidative Stress-Induced Apoptosis in Chondrocytes Cultured on 3D-Porous Scaffolds in Static versus Dynamic Cultures

The aim of this study was to investigate the relation between the amount of glycosaminoglycans (GAGs) secreted and the level of apoptosis induced by hydrogen peroxide (H2O2) in porcine chondrocytes cultured on two different biodegradable PCL/PHBV scaffolds: one had primary pores solely, while the other possessed both primary and secondary pores, namely PCL/PHBV/0%NaCl and PCL/PHBV/50%NaCl scaffolds, respectively. The scaffolds with an average primary pore size of 200 μm were primarily fabricated by a fused deposition modeling (FDM) machine, and secondary pores on the material surface were then generated after NaCl leaching in a sodium hydroxide solution. The investigation was performed comparatively under static and dynamic environments. In static culture study, more pronounced GAG accumulation was found on the PCL/PHBV/50%NaCl scaffold, suggesting that the secondary pores could promote the chondrogenic function of chondrocytes, and the primary pores could further accommodate the cells to grow and function more productively. Meanwhile, the significant reductions in the levels of apoptosis of chondrocytes, studied in a H2O2-dose dependent manner (0-2 mM), were observed with a use of a flow cytometer when the chondrocytes were cultured on the PCL/PHBV/50%NaCl scaffold in which more GAG content was found. In dynamic culture study, although the total GAG content detected on the PCL/PHBV/50%NaCl scaffold was still significantly higher than that measured on the PCL/PHBV/0%NaCl scaffold, these GAG accumulations were tremendously greater than those found in the static culture. As a consequence, far less oxidative stress-induced apoptotic death was observed in the cells cultured under the dynamic culture. Moreover, cells seemed to be well protected from apoptosis, in the presence of considerable amounts of GAGs; similar degrees of apoptosis (~25%) were observed on the cells cultured on each scaffold at all H2O2 concentrations studied. The obtained results had demonstrated that the degree of chondrocyte apoptosis was somehow related to the level of GAG accumulation.

Apoptotic bodies from endplate chondrocytes enhance the oxidative stress-induced mineralization by regulating PPi metabolism

This study aimed to investigate the role of apoptotic bodies (Abs) from the oxidative stressed endplate chondrocytes in regulating mineralization and potential mechanisms. Endplate chondrocytes were isolated from rats and treated with H2O2 to induce oxidative stress. The calcium deposition for matrix mineralization in the cells was examined by histological staining. The expression levels of calcification‐related genes in individual groups of cells were determined by quantitative real time‐PCR (qRT‐PCR). Subsequently, extracellular vesicles (EVs) were purified and characterized. The effect of treatment with H2O2 and/or Abs on the mineralization, extracellular PPi metabolism and related gene expression were determined. Oxidative stress significantly increased the mineralization and promoted the generation of main Abs from endplate chondrocytes. Abs were effectively endocytosed by endplate chondrocytes and co‐localized with collagen (COL)‐II in the cytoplasm, which enhanced the mineralization, alkaline phosphatase (ALP), osteocalcin (OCN), Runt‐related transcription factor 2 (RUNX2) and COL‐I expression in endplate chondrocytes. Furthermore, treatment either H2O2 or Abs significantly decreased PPi, but increased Pi production and treatment with both further enhancing the changes in endplate chondrocytes. Similarly, treatment either H2O2 or Abs significantly decreased the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), and ankylosis protein (ANK) expression and ENPP1 promoter activity, but increased the tissue‐nonspecific alkaline phosphatase (TNAP) expression and TNAP promoter activity in endplate chondrocytes. Oxidative stress promoted the generation of Abs, which might enhance the oxidative stress‐mediated mineralization in endplate chondrocytes by regulating the PPi metabolism.

Omega-3 fatty acids and docosahexaenoic acid oxymetabolites modulate the inflammatory response of equine recombinant interleukin1β-stimulated equine synoviocytes

Omega-3 fatty acid (n-3 PUFA) supplementation may have beneficial effects in certain chronic diseases, potentially including osteoarthritis. Favorable effects are attributed, in part, to downstream pro-resolving oxylipid metabolites. We investigated the role of n-3 PUFA and docosahexaenoic acid (DHA)-derived oxylipids (docosanoids) on equine synoviocyte metabolism. We hypothesized that n-3 PUFA and selected docosanoids would modulate inflammatory mediator gene expression by recombinant equine (re)IL-1β-stimulated synovial fibroblasts. Synoviocyte monolayer cultures were prepared from grossly normal equine carpal synovium. Cellular incorporation of eicosapentaenoic acid (EPA) and DHA was determined using LC-MS and docosanoid biosynthesis by LC-MS-MS. The influence of n-3 PUFA and docosanoids on osteoarthritis marker gene expression was determined by quantitative real time polymerase chain reaction (qPCR). Synoviocytes incorporated EPA and DHA in significant amounts and DHA treatment augmented the synthesis of several docosanoids. Synoviocyte cultures pre-treated with EPA or DHA followed by reIL-1β stimulation had significant reductions in expression of ADAMTS4, MMP-1, MMP-13, IL-1β, IL-6 and COX-2. The docosanoids resolvin D1 and D2, maresin 1 and protectin DX, alone and in combination, abrogated ADAMTS4, MMP-1, MMP-13, and IL-6 gene expression in reIL-1β-stimulated synoviocytes. Similarly, both resolvins and maresin 1 stifled COX-2 expression. Our results demonstrate that synoviocytes readily incorporate n-3 PUFA. DHA incorporation was sufficient for biosynthesis of significant concentrations of several docosanoids which modulated the synovial inflammatory response in vitro. These data indicate n-3 PUFA supplementation may prove useful in the prevention or treatment of osteoarthritis.

Physiologic and pathologic effects of dietary free fatty acids on cells of the joint

Fatty acids (FAs) are potent organic compounds that not only can be used as an energy source during nutrient deprivation but are also involved in several essential signaling cascades in cells. Therefore, a balanced intake of different dietary FAs is critical for the maintenance of cellular functions and tissue homeostasis. A diet with an imbalanced fat composition creates a risk for developing metabolic syndrome and various musculoskeletal diseases, including osteoarthritis (OA). In this review, we summarize the current state of knowledge and mechanistic insights regarding the role of dietary FAs, such as saturated FAs, omega-6 polyunsaturated FAs (PUFAs), and omega-3 PUFAs on joint inflammation and OA pathogeneses. In particular, we review how different types of dietary FAs and their derivatives distinctly affect a variety of cells within the joint, including chondrocytes, osteoblasts, osteoclasts, and synoviocytes. Understanding the molecular mechanisms underlying the effects of FAs on metabolic behavior, anabolic, and catabolic processes, as well as the inflammatory response of joint cells, may help identify therapeutic targets for the prevention of metabolic joint diseases.

Effects of Hesperidin on H₂O₂-Treated Chondrocytes and Cartilage in a Rat Osteoarthritis Model

Background

The purpose of this research was to investigate the effects of hesperidin on hydrogen peroxide (H₂O₂)-induced chondrocytes injury and cartilage degeneration in a rat model of osteoarthritis (OA).

Material/Methods

Chondrocytes were isolated from rat knee joints and treated with hesperidin alone or combined with H₂O₂. Then, Cell Counting Kit-8 (CCK-8) assay was used to assess cell viability. Activity of reactive oxygen species (ROS) and levels of malondialdehyde (MDA) were estimated. Cell apoptosis was assessed by flow cytometry assay. In addition, gene expression levels were measured for caspase 3, tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), collagen type II (Col2a1), aggrecan, (sex-determining region Y)-box 9 (SOX9), matrix metalloproteinase (MMP)-13, and inducible nitric oxide synthase (iNOS) through quantitative real-time polymerase chain reaction (qPCR). To examine the effects on cartilage destruction in vivo, hesperidin or vehicle control were orally administrated in a surgically-induced osteoarthritis (OA) model.

Results

The results indicated that hesperidin pretreatment of chondrocytes reduce H₂O₂-induced cytotoxicity and apoptosis. Hesperidin pretreatment decreased the formation of MDA and intracellular ROS, including chondrocyte apoptosis. Hesperidin also reversed the activity of H₂O₂ on inhibiting the Col2a1, aggrecan, and SOX9 gene expression and increasing the gene expression of caspase 3, IL-1β, TNFα, iNOS, and MMP13. In addition, hesperidin administration markedly attenuated cartilage destruction and reduced IL-1β and TNF-α levels in a surgically-induced OA model.

Conclusions

Our study suggests that hesperidin can prevent H₂O₂-induced chondrocytes injury through its antioxidant effects in vitro and reduce cartilage damage in a rat model of OA.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Articular Cartilage Aging-Potential Regenerative Capacities of Cell Manipulation and Stem Cell Therapy

Changes in articular cartilage during the aging process are a stage of natural changes in the human body. Old age is the major risk factor for osteoarthritis but the disease does not have to be an inevitable consequence of aging. Chondrocytes are particularly prone to developing age-related changes. Changes in articular cartilage that take place in the course of aging include the acquisition of the senescence-associated secretory phenotype by chondrocytes, a decrease in the sensitivity of chondrocytes to growth factors, a destructive effect of chronic production of reactive oxygen species and the accumulation of the glycation end products. All of these factors affect the mechanical properties of articular cartilage. A better understanding of the underlying mechanisms in the process of articular cartilage aging may help to create new therapies aimed at slowing or inhibiting age-related modifications of articular cartilage. This paper presents the causes and consequences of cellular aging of chondrocytes and the biological therapeutic outlook for the regeneration of age-related changes of articular cartilage.

Early Metabolome Profiling and Prognostic Value in Paraquat-Poisoned Patients: Based on Ultraperformance Liquid Chromatography Coupled To Quadrupole Time-of-Flight Mass Spectrometry

Paraquat (PQ) has caused countless deaths throughout the world. There remains no effective treatment for PQ poisoning. Here we study the blood metabolome of PQ-poisoned patients using ultraperformance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS). Patients were divided into groups according to blood PQ concentration. Healthy subjects served as controls. Metabolic features were statistically analyzed using multivariate pattern-recognition techniques to identify the most important metabolites. Selected metabolites were further compared with a series of clinical indexes to assess the prognostic value. PQ-poisoned patients showed substantial differences compared with healthy subjects. Based on variable of importance in the project (VIP) values and statistical analysis, 17 metabolites were selected and identified. These metabolites well-classified low PQ-poisoned patients, high PQ-poisoned patients, and healthy subjects, which was better than that of a complete blood count (CBC). Among the 17 metabolites, 20:3/18:1-PC (PC), LPA (0:0/16:0) (LPA), 19-oxo-deoxycorticosterone (19-oxo-DOC), and eicosapentaenoic acid (EPA) had prognostic value. In particular, EPA was the most sensitive one. Besides, the levels of EPA was correlated with LPA and 19-oxo-DOC. If EPA was excessively consumed, then prognosis was poor. In conclusion, the serum metabolome is substantially perturbed by PQ poisoning. EPA is the most important biomarker in early PQ poisoning.

Aging and osteoarthritis: Central role of the extracellular matrix

Osteoarthritis (OA), is a major cause of severe joint pain, physical disability and quality of life impairment in the aging population across the developed and developing world. Increased catabolism in the extracellular matrix (ECM) of the articular cartilage is a key factor in the development and progression of OA. The molecular mechanisms leading to an impaired matrix turnover have not been fully clarified, however cellular senescence, increased expression of inflammatory mediators as well as oxidative stress in association with an inherently limited regenerative potential of the tissue, are all important contributors to OA development. All these factors are linked to and tend to be maximized by aging. Nonetheless the role of aging in compromising joint stability and function in OA has not been completely clarified yet. This review will systematically analyze cellular and structural changes taking place in the articular cartilage and bone in the pathogenesis of OA which are linked to aging. A particular emphasis will be placed on age-related changes in the phenotype of the articular chondrocytes.

Association between MMP3 and TIMP3 polymorphisms and risk of osteoarthritis

Osteoarthritis (OA) is the most commonly occurring degenerative joint disease worldwide, and its incidence has increased in recent years. We evaluated whether there is the association between MMP-3 and TIMP-3 variants and susceptibility to OA in a Chinese population. Venous blood samples were collected from 431 female participants (200 cases and 231 controls) at Hong Hui Hospital, Xi’an Jiaotong University College of Medicine between 2015 and 2016. After genotyping the samples using standard protocols, the association between MMP-3 and TIMP-3 single nucleotide polymorphisms and risk of OA was assessed by calculating odds ratios (ORs) and 95% confidence intervals (95% CIs) using unconditional logistic regression analysis. The minor G allele of rs650108 was associated with OA risk in a recessive model (p = 0.034, OR = 1.82, 95%CI = 1.04-3.18), while the minor A allele of rs715572 was associated with OA risk in a recessive model (p = 0.030, OR = 1.88, 95%CI = 1.05-3.34). Thus a suggestive association was observed in a discovery case-control study between OA and two common SNPs, rs650108 in MMP-3 and rs715572 in TIMP-3.

Gene expression analysis of growth factor receptors in human chondrocytes in monolayer and 3D pellet cultures

The main goal of cartilage repair is to create functional tissue by enhancing the in vitro conditions to more physiological in vivo conditions. Chondrogenic growth factors play an important role in influencing cartilage homeostasis. Insulin‑like growth factor (IGF)‑1 and transforming growth factor (TGF)‑β1 affect the expression of collagen type II (Col2) and glycosaminoglycans (GAGs) and, therefore, the targeted use of growth factors could make chondrogenic redifferentiation more efficient. In the present study, human chondrocytes were postmortally isolated from healthy articular cartilage and cultivated as monolayer or 3D pellet cultures either under normoxia or hypoxia and stimulated with IGF‑1 and/or TGF‑β1 to compare the impact of the different growth factors. The mRNA levels of the specific receptors (IGF1R, TGFBR1, TGFBR2) were analyzed at different time points. Moreover, gene expression rates of collagen type 1 and 2 in pellet cultures were observed over a period of 5 weeks. Additionally, hyaline‑like Col2 protein and sulphated GAG (sGAG) levels were quantified. Stimulation with IGF‑1 resulted in an enhanced expression of IGF1R and TGFBR2 whereas TGF‑β1 stimulated TGFBR1 in the monolayer and pellet cultures. In monolayer, the differences reached levels of significance. This effect was more pronounced under hypoxic culture conditions. In pellet cultures, increased amounts of Col2 protein and sGAGs after incubation with TGF‑β1 and/or IGF‑1 were validated. In summary, constructing a gene expression profile regarding mRNA levels of specific growth factor receptors in monolayer cultures could be helpful for a targeted application of growth factors in cartilage tissue engineering.

Acetoacetate induces hepatocytes apoptosis by the ROS-mediated MAPKs pathway in ketotic cows

Dairy cows with ketosis are characterized by oxidative stress, hepatic damage, and hyperketonemia. Acetoacetate (AA) is the main component of ketone bodies in ketotic cows, and is associated with the above pathological process. However, the potential mechanism was not illuminated. Therefore, the aim of this study was to investigate the mechanism of AA-induced hepatic oxidative damage in ketotic cows. Compared with healthy cows, ketotic cows exhibited severe oxidative stress and hepatic damage. Moreover, the extent of hepatic damage and oxidative stress had a positive relationship with the AA levels. In vitro, AA treatment increased reactive oxygen species (ROS) content and further induced oxidative stress and apoptosis of bovine hepatocytes. In this process, AA treatment increased the phosphorylation levels of JNK and p38MAPK and decreased the phosphorylation level of ERK, which could increase p53 and inhibit nuclear factor E2-related factor 2 (Nrf2) expression, nuclear localization, and DNA-binding affinity, thereby inducing the overexpression of pro-apoptotic molecules Bax, Caspase 3, Caspase 9, PARP and inhibition of anti-apoptotic molecule Bcl-2. Antioxidant N-acetylcysteine (NAC) treatment or interference of MAPKs pathway could attenuate the hepatocytes apoptosis induced by AA. Collectively, these results indicate that AA triggers hepatocytes apoptosis via the ROS-mediated MAPKs pathway in ketotic cows.

Protective effects of seabuckthorn pulp and seed oils against radiation-induced acute intestinal injury

Radiation-induced gastrointestinal syndrome, including nausea, diarrhea and dehydration, contributes to morbidity and mortality after medical or industrial radiation exposure. No safe and effective radiation countermeasure has been approved for clinical therapy. In this study, we aimed to investigate the potential protective effects of seabuckthorn pulp and seed oils against radiation-induced acute intestinal injury. C57/BL6 mice were orally administered seabuckthorn pulp oil, seed oil and control olive oil once per day for 7 days before exposure to total-body X-ray irradiation of 7.5 Gy. Terminal deoxynucleotidyl transferase dUTP nick end labeling, quantitative real-time polymerase chain reaction and western blotting were used for the measurement of apoptotic cells and proteins, inflammation factors and mitogen-activated protein (MAP) kinases. Seabuckthorn oil pretreatment increased the post-radiation survival rate and reduced the damage area of the small intestine villi. Both the pulp and seed oil treatment significantly decreased the apoptotic cell numbers and cleaved caspase 3 expression. Seabuckthorn oil downregulated the mRNA level of inflammatory factors, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-8. Both the pulp and seed oils elevated the level of phosphorylated extracellular-signal-regulated kinase and reduced the levels of phosphorylated c-Jun N-terminal kinase and p38. Palmitoleic acid (PLA) and alpha linolenic acid (ALA) are the predominant components of pulp oil and seed oil, respectively. Pretreatment with PLA and ALA increased the post-radiation survival time. In conclusion, seabuckthorn pulp and seed oils protect against mouse intestinal injury from high-dose radiation by reducing cell apoptosis and inflammation. ALA and PLA are promising natural radiation countermeasure candidates.

Insights on Molecular Mechanisms of Chondrocytes Death in Osteoarthritis

Osteoarthritis (OA) is a joint pathology characterized by progressive cartilage degradation. Medical care is mainly based on alleviating pain symptoms. Compelling studies report the presence of empty lacunae and hypocellularity in cartilage with aging and OA progression, suggesting that chondrocyte cell death occurs and participates to OA development. However, the relative contribution of apoptosis per se in OA pathogenesis appears complex to evaluate. Indeed, depending on technical approaches, OA stages, cartilage layers, animal models, as well as in vivo or in vitro experiments, the percentage of apoptosis and cell death types can vary. Apoptosis, chondroptosis, necrosis, and autophagic cell death are described in this review. The question of cell death causality in OA progression is also addressed, as well as the molecular pathways leading to cell death in response to the following inducers: Fas, Interleukin-1β (IL-1β), Tumor Necrosis factor-α (TNF-α), leptin, nitric oxide (NO) donors, and mechanical stresses. Furthermore, the protective role of autophagy in chondrocytes is highlighted, as well as its decline during OA progression, enhancing chondrocyte cell death; the transition being mainly controlled by HIF-1α/HIF-2α imbalance. Finally, we have considered whether interfering in chondrocyte apoptosis or promoting autophagy could constitute therapeutic strategies to impede OA progression.

Cellular senescence in aging and osteoarthritis

- It is well accepted that age is an important contributing factor to poor cartilage repair following injury, and to the development of osteoarthritis. Cellular senescence, the loss of the ability of cells to divide, has been noted as the major factor contributing to age-related changes in cartilage homeostasis, function, and response to injury. The underlying mechanisms of cellular senescence, while not fully understood, have been associated with telomere erosion, DNA damage, oxidative stress, and inflammation. In this review, we discuss the causes and consequences of cellular senescence, and the associated biological challenges in cartilage repair. In addition, we present novel strategies for modulation of cellular senescence that may help to improve cartilage regeneration in an aging population.

A low ratio of n-6/n-3 polyunsaturated fatty acids suppresses matrix metalloproteinase 13 expression and reduces adjuvant-induced arthritis in rats

Increased expression of matrix metalloproteinase 13 (MMP13) in chondrocytes contributes to the development of osteoarthritis. The hypothesis of this study was that diet with a low ratio of n-6/n-3 polyunsaturated fatty acids (PUFAs) is associated with reduced MMP13 expression in inflammatory chondrocytes in vitro and in vivo. Human chondrocytes were cultured with different ratios of linoleic acid (LA, n-6 PUFA) to α-linolenic acid (n-3 PUFA) from 1:1 to 10:1. Proliferation of chondrocytes, MMP13 protein and mRNA levels were detected, respectively. Sprague-Dawley rats (n=30) were fed diets containing different ratios of n-6/n-3 PUFA. Freund's complete adjuvant was injected to make the model of arthritis. Paw swelling rate was measured and all rats were euthanized after 6 weeks of treatment. Serum MMP13 and IL-1 were measured by enzyme-linked immunosorbent assay. Joint histological sections were stained with safranin-O Fast Green to evaluate cartilage damage. Low ratio of LA/α-linolenic acid decreased the mRNA and protein levels of MMP13 but did not affect chondrocytes proliferation. Ratios of PUFA such as 1:1 and 2:1 significantly reduced paw swelling rate, and serum MMP13 and IL-1 levels in a rat model. Histological staining showed that ratios of 1:1 and 2:1 PUFA significantly alleviated cartilage damage in adjuvant-induced arthritis. A ratio of n-6/n-3 PUFA of 1:1 showed the strongest inhibitory effect on MMP13. Our results indicate that a low ratio of n-6/n-3 PUFA at 1:1 significantly suppressed MMP13 expression both in vitro and in vivo and reduced adjuvant-induced arthritis in rats could be a means to control and reduce the symptoms of osteoarthritis.

The role of resolvin D1 in the regulation of inflammatory and catabolic mediators in osteoarthritis

OBJECTIVE AND DESIGN

Resolvin D1 (RvD1), an omega-3 fatty acid derivative, has shown remarkable properties in resolving inflammation, promoting tissue repair and preserving tissue integrity. In this study, we investigated RvD1 effects on major processes involved in osteoarthritis (OA) pathophysiology.

MATERIALS AND METHODS

Human OA chondrocytes were treated with either 1 ng/ml interleukin-1β (IL-1β) or 20 μM 4-hydroxynonenal (HNE), then treated or not with increased concentrations of RvD1 (0-10 μM). RvD1 levels were measured by enzyme immunoassay in synovial fluids from experimental dog model of OA and sham operated dogs obtained from our previous study. Cell viability was evaluated by 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-SH-tetrazolium bromide assay. Parameters related to inflammation, catabolism and apoptosis were determined by enzyme-linked immunosorbent assay, Western blotting, and quantitative polymerase chain reaction. Glutathione (GSH) was assessed by commercial kit. The activation of mitogen-activated protein kinases and nuclear factor-kappaB (NF-κB) pathways was evaluated by Western blot.

RESULTS

We showed that RvD1 levels were higher in synovial fluids from OA joint compared to controls. In OA human chondrocytes, we demonstrated that RvD1 was not toxic up to 10 μM and stifled IL-1β-induced cyclooxygenase 2, prostaglandin E2, inducible nitric oxide synthase, nitric oxide, and matrix metalloproteinase-13. Our study of signalling pathways revealed that RvD1 suppressed IL-1β-induced activation of NF-κB/p65, p38/MAPK and JNK(1/2). Moreover, RvD1 prevented HNE-induced cell apoptosis and oxidative stress, as indicated by inactivation of caspases, inhibition of lactate dehydrogenase release, and increased levels of Bcl2 and AKT, as well as GSH.

CONCLUSION

This is the first in vitro study demonstrating the beneficial effect of RvD1 in OA. That RvD1 abolishing a number of factors known to be involved in OA pathogenesis renders it a clinically valuable agent in prevention of the disease.

ROS/oxidative stress signaling in osteoarthritis

Osteoarthritis is the most common joint disorder with increasing prevalence due to aging of the population. Its multi-factorial etiology includes oxidative stress and the overproduction of reactive oxygen species, which regulate intracellular signaling processes, chondrocyte senescence and apoptosis, extracellular matrix synthesis and degradation along with synovial inflammation and dysfunction of the subchondral bone. As disease-modifying drugs for osteoarthritis are rare, targeting the complex oxidative stress signaling pathways would offer a valuable perspective for exploration of potential therapeutic strategies in the treatment of this devastating disease.

p21 deficiency is susceptible to osteoarthritis through STAT3 phosphorylation

Introduction

Osteoarthritis (OA) is a multifactorial disease, and recent studies have suggested that cell cycle–related proteins play a role in OA pathology. p21 was initially identified as a potent inhibitor of cell cycle progression. However, it has been proposed that p21 is a regulator of transcription factor activity. In this study, we evaluated the role of p21 in response to biomechanical stress.

Methods

Human chondrocytes were treated with p21-specific small interfering RNA (siRNA), and cyclic tensile strain was introduced in the presence or absence of a signal transducer and activator of transcription 3 (STAT3)-specific inhibitor. Further, we developed an in vivo OA model in a p21-knockout background for in vivo experiments.

Results

The expression of matrix metalloproteinase (MMP13) mRNA increased in response to cyclic tensile strain following transfection with p21 siRNA, whereas the expression of aggrecan was decreased. Phospho-STAT3 and MMP-13 protein levels increased following downregulation of p21, and this was reversed by treatment with a STAT3 inhibitor. p21-deficient mice were susceptible to OA, and this was associated with increased STAT3 phosphorylation, elevated MMP-13 expression, and elevation of synovial inflammation. The expression of p21 mRNA was decreased and phosphorylation of STAT3 was elevated in human OA chondrocytes.

Conclusions

The lack of p21 has catabolic effects by regulation of aggrecan and MMP-13 expression through STAT3 phosphorylation in the cartilage tissue. p21 may function as a regulator of transcriptional factors other than the inhibitor of cell cycle progression in the cartilage tissue. Thus, the regulation of p21 may be a therapeutic strategy for the treatment of OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0828-6) contains supplementary material, which is available to authorized users.

Oxidative stress induced by zearalenone in porcine granulosa cells and its rescue by curcumin in vitro

Oxidative stress (OS), as a signal of aberrant intracellular mechanisms, plays key roles in maintaining homeostasis for organisms. The occurrence of OS due to the disorder of normal cellular redox balance indicates the overproduction of reactive oxygen species (ROS) and/or deficiency of antioxidants. Once the balance is broken down, repression of oxidative stress is one of the most effective ways to alleviate it. Ongoing studies provide remarkable evidence that oxidative stress is involved in reproductive toxicity induced by various stimuli, such as environmental toxicants and food toxicity. Zearalenone (ZEA), as a toxic compound existing in contaminated food products, is found to induce mycotoxicosis that has a significant impact on the reproduction of domestic animals, especially pigs. However, there is no information about how ROS and oxidative stress is involved in the influence of ZEA on porcine granulosa cells, or whether the stress can be rescued by curcumin. In this study, ZEA-induced effect on porcine granulosa cells was investigated at low concentrations (15 μM, 30 μM and 60 μM). In vitro ROS levels, the mRNA level and activity of superoxide dismutase, glutathione peroxidase and catalase were obtained. The results showed that in comparison with negative control, ZEA increased oxidative stress with higher ROS levels, reduced the expression and activity of antioxidative enzymes, increased the intensity of fluorogenic probes 2', 7'-Dichlorodihydrofluorescin diacetate and dihydroethidium in flow cytometry assay and fluorescence microscopy. Meanwhile, the activity of glutathione (GSH) did not change obviously following 60 μM ZEA treatment. Furthermore, the underlying protective mechanisms of curcumin on the ZEA-treated porcine granulosa cells were investigated. The data revealed that curcumin pre-treatment significantly suppressed ZEA-induced oxidative stress. Collectively, porcine granulosa cells were sensitive to ZEA, which may induce oxidative stress. The findings from this study clearly demonstrate that curcumin is effective to reduce the dysregulation of cellular redox balance on porcine granulosa cells in vitro and should be further investigated for its protective role against ZEA in animals.