Consequences of metabolic and oxidative modifications of cartilage tissue

Verapamil attenuates intervertebral disc degeneration by suppressing ROS overproduction and pyroptosis via targeting the Nrf2/TXNIP/NLRP3 axis in four-week puncture-induced rat models both in vivo and in vitro

Low back pain is usually caused by intervertebral disc degeneration (IVDD), during which the involvement of oxidation system imbalance and inflammasome activation cannot be neglected. In this study, we aimed to validate the expression level of TXNIP in IVDD and investigate the function and potential mechanism of action of verapamil. TXNIP is upregulated in the degenerate nucleus pulposus in both humans and rats, as well as in tert-butyl hydroperoxide (TBHP)-stimulated nucleus pulposus cells. Administration of verapamil, a classic clinical drug, mitigated the TBHP-induced overproduction of reactive oxygen species and activation of the NLRP3 inflammasome, thus protecting cells from pyroptosis, apoptosis, and extracellular matrix degradation. The Nrf2/TXNIP/NLRP3 axis plays a major role in verapamail-mediated protection. In vivo, a puncture-induced IVDD rat model was constructed, and we found that verapamil delayed the development of IVDD at both the imaging and histological levels. In summary, our results indicate the potential therapeutic effects and mechanisms of action of verapamil in the treatment of IVDD.

Cartilage-inspired terpolymer hydrogel with excellent mechanical properties and superior lubricating ability

Osteoarthritis (OA), the most common degenerative joint disorder, seriously affects patients' daily activities. Recently, hydrogels, due to their similar structure to articular cartilage, have shown great potential as cartilage-repairing materials. In the present work, we developed a simple process for fabricating terpolymer [P(acrylamide-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/Fe3+] hydrogel [P(AAm-co-AAc-co-AMPS)/Fe3+]. The content of AMPS was found to show a crucial effect on the mechanical and tribological performance of the terpolymer hydrogel. When the content of AMPS was 0.45 mol L-1, the compressive strength, modulus, and friction coefficient of the terpolymer hydrogel were 66.60 ± 1.79 MPa, 2.10 ± 0.16 MPa, and 0.032, respectively. In addition, the hydrogel showed high wear durability and the friction coefficient was as low as 0.038 after 3.6 × 105 sliding cycles.

IL-10 enhances cell-to-cell communication in chondrocytes via STAT3 signaling pathway

Gap junction intercellular communication (GJIC) allows the transfer of material, message and energy between cells, which influences cell behaviors including cell proliferation, migration, differentiation and apoptosis and determines cell fate. Interleukin-10 (IL-10), a versatile cytokine, attracts more and more attention in the cartilage pathology such as osteoarthritis (OA) due to its potential in anti-inflammation and wound repair. However, whether IL-10 can mediate GJIC in chondrocytes remains elusive. In the current study, we aimed to explore the role of IL-10 on GJIC and its underlying mechanism. We found that IL-10 can promote GJIC in living chondrocytes. IL-10-enhanced GJIC in chondrocytes was dependent on the up-regulation of connexin 43 (Cx43). Knockdown experiment based on siRNA interference then confirmed that IL-10-enhanced GJIC required participation of IL-10 receptor 1 (IL-10R1). IL-10 activated signal transducer and activator of transcription 3 (STAT3) signaling and promoted the nuclear accumulation of p-STAT3 through IL-10 receptor 1. Inhibitor experiment further confirmed the importance of STAT3 signaling in IL-10-mediated GJIC. Taking together, our results provided a thorough process of IL-10-modulated cell-to-cell communication in chondrocytes and established a bridge between inflammatory factor, IL-10, and GJIC, which can increase our understanding about the physiology and pathology of cartilage.

The yin/yang balance of the MHC-self-immunopeptidome

The MHC-self immunopeptidome of professional antigen presenting cells is a cognate ligand for the TCRs expressed on both conventional and thymic-derived natural regulatory T cells. In regulatory T cells, the TCR signaling associated with MHC-peptide recognition induces antigen specific as well as bystander immunosuppression. On the other hand, TCR activation of conventional T cells is associated with protective immunity. As such the peripheral T cell repertoire is populated by a number of T cells with different phenotypes and different TCRs, which can recognize the same MHC-self-peptide complex, resulting in opposite immunological outcomes. This article summarizes what is known about regulatory and conventional T cell recognition of the MHC-self-immunopeptidome at steady state and in inflammatory conditions associated with increased T and B cell self-reactivity, discussing how changes in the MHC-ligandome including epitope copy number and post-translational modifications can tilt the balance toward the expansion of pro-inflammatory or regulatory T cells.

Spatial Gradients of Quantitative MRI as Biomarkers for Early Detection of Osteoarthritis: Data From Human Explants and the Osteoarthritis Initiative

BACKGROUND

Healthy articular cartilage presents structural gradients defined by distinct zonal patterns through the thickness, which may be disrupted in the pathogenesis of several disorders. Analysis of textural patterns using quantitative MRI data may identify structural gradients of healthy or degenerating tissue that correlate with early osteoarthritis (OA).

PURPOSE

To quantify spatial gradients and patterns in MRI data, and to probe new candidate biomarkers for early severity of OA.

STUDY TYPE

Retrospective study.

SUBJECTS

Fourteen volunteers receiving total knee replacement surgery (eight males/two females/four unknown, average age ± standard deviation: 68.1 ± 9.6 years) and 10 patients from the OA Initiative (OAI) with radiographic OA onset (two males/eight females, average age ± standard deviation: 57.7 ± 9.4 years; initial Kellgren-Lawrence [KL] grade: 0; final KL grade: 3 over the 10-year study).

FIELD STRENGTH/SEQUENCE

3.0-T and 14.1-T, biomechanics-based displacement-encoded imaging, fast spin echo, multi-slice multi-echo T2 mapping.

ASSESSMENT

We studied structure and strain in cartilage explants from volunteers receiving total knee replacement, or structure in cartilage of OAI patients with progressive OA. We calculated spatial gradients of quantitative MRI measures (eg, T2) normal to the cartilage surface to enhance zonal variations. We compared gradient values against histologically OA severity, conventional relaxometry, and/or KL grades.

STATISTICAL TESTS

Multiparametric linear regression for evaluation of the relationship between residuals of the mixed effects models and histologically determined OA severity scoring, with a significance threshold at α = 0.05.

RESULTS

Gradients of individual relaxometry and biomechanics measures significantly correlated with OA severity, outperforming conventional relaxometry and strain metrics. In human explants, analysis of spatial gradients provided the strongest relationship to OA severity (R²  = 0.627). Spatial gradients of T2 from OAI data identified variations in radiographic (KL Grade 2) OA severity in single subjects, while conventional T2 alone did not.

DATA CONCLUSION

Spatial gradients of quantitative MRI data may improve the predictive power of noninvasive imaging for early-stage degeneration.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 1.

Catalytic anti-oxidative stress for osteoarthritis treatment by few-layered phosphorene

As one of the most common representations of articular cartilage damage, osteoarthritis (OA) is characterized by the apoptosis and dysfunction of chondrocytes as well as the progressive degradation of extracellular matrix, of which the main components are glycosaminoglycan and type Ⅱ collagen. Few-layered phosphorene (FLP) has been attracting great attentions in biomedical fields owing to the excellent capability of in-situ catalysis for scavenging oxidate-associated molecules, especially the reactive oxygen species (ROS) and reactive nitrogen species (RNS). Herein, FLP has been fabricated and employed for articular cartilage protection by means of deleting oxidate-associated molecules. The in vitro results show that as low as 200 ​μg/mL FLP is capable of diminishing oxidative damages on the osteoarthritic chondrocytes through the efficient elimination of ROS, H₂O₂ and NO. Meanwhile, the cartilage matrix protection has also been achieved at 200 ​μg/mL FLP by the uniform restoration of glycosaminoglycan and type Ⅱ collagen. FLP enables the nanocatalytic treatment for the overloaded oxidative stress in the injured articular cartilage and represents a promising alternative for osteoarthritis therapy.

Potential Protective Role of Galectin-3 in Patients with Gonarthrosis and Diabetes Mellitus: A Cross-Sectional Study

BACKGROUND

Gonarthrosis and diabetes mellitus are two diseases that are increasingly being linked. The aim of this study was to quantify serum levels of Gal-3, pro- and anti-inflammatory cytokines (including their ratios and correlations), and participant's condition (pain, stiffness, functional limitations) in gonarthrosis patients with and without diabetes mellitus.

METHODS

A between-subject, cross-sectional experimental design was adopted. Serum levels of TNF-α, IL-6, IL-12, IL-23, IFN-γ, IL-17, IL-10, Gal-3, and WOMAC score were measured.

RESULTS

Gonarthrosis patients with diabetes mellitus had significantly (p < 0.05) lower levels of TNF-α, IL-6, IL-12, IL-17, IFN-γ, and Gal-3 compared to gonarthrosis patients without diabetes mellitus. On the other hand, IL-10/TNF-α, IL-10/IL-6, IL-10/IL-12, Gal-3/TNF-α, Gal-3/IL-6, and Gal-3/IL-12 (p = 0.001) were significantly higher (p < 0.05) in gonarthrosis with diabetes mellitus. Moderate-large correlation (p < 0.05) was detected between the serum values of Gal-3 and pro- and anti-inflammatory cytokines, including IL-12 (r = 0.575), IL-10 (r = 0.535), TNF-α (r = 0.306), and IL-23 (r = 0.323). WOMAC index was significantly lower (p < 0.05) in gonarthrosis patients without diabetes mellitus compared to gonarthrosis patients with diabetes mellitus.

CONCLUSIONS

Correlation between Gal-3 and proinflammatory cytokines and its dominance over proinflammatory cytokines implicate the potential role of Gal-3 in preventing cartilage destruction.

Current Probes for Imaging Carbonylation in Cellular Systems and Their Relevance to Progression of Diseases

Oxidative stress resulted from reactive oxygen or nitrogen species in biological systems has a significant role in the diagnosis/progression of several human diseases. Human diseases associated with oxidative stress include Alzheimer's disease, chronic lung disease, chronic renal failure, cancer, diabetes, and fibrosis. In oxidative stress conditions, carbonylation process can be described as one of the most common modifications in biomolecules that takes place in the presence of carbonyl (C = O) groups which are introduced into molecules by direct metal-catalyzed oxidation of certain amino acids or indirectly by reaction with the oxidation of lipids and sugars. At a molecular cellular level, carbonylation can cause some defective biological consequences or chemical transformations in cells. During this process, specifically, carbonylated proteins can be accumulated in cells and trigger to develop some diseases in human body. The role of the accumulation of carbonylated proteins in the progression of several diseases has also been reported in the literature, such as neurodegenerative diseases, diabetes, obesity, aging, and cancer. Early detection of carbonylation process is, therefore, very critical to monitor these diseases at an early stage. Finding a suitable biomarker or probe is very challenging due to the need for multiple criteria: high fluorescence efficiency, stability, toxicity, and permeability. If they are designed with a good strategy, these probes are highly effective in cell biology applications and they can be used as good diagnostic tools for monitoring oxidative stress-induced carbonylation in relevant diseases. This review highlights the design and use of recent fluorescent probes for visualization of carbonylation in cellular systems and the relationship between oxidative stress and carbonyl species for causing long-term disease complications.

Carbazate-modified cross-linked dextran microparticles suppress the progression of osteoarthritis by ROS scavenging

A series of modified polysaccharide microparticles have been fabricated and their potential application for scavenging reactive oxygen species (ROS) and their derivatives to achieve osteoarthritis (OA) treatment has been explored. These microparticles were cross-linked dextran (Sephadex) with different carbazate substitution ratios determined by the TNBS assay and elemental analysis. It has been demonstrated that they could effectively scavenge carbonylated proteins and ROS including hydroxyl radicals (˙OH), superoxide anions (˙O₂^-) and H₂O₂ and their derivatives with high efficiency, improve the viability of H₂O₂-treated chondrocytes by reducing their ROS levels, as well as lower their inflammatory factors. The above ability of antioxidation and inflammation resistance improved with the increase of carbazate substitution ratio. Significantly, this work provided the proof that modified Sephadex successfully alleviated the deterioration of cartilage and the progression of OA in vivo. The proposed microparticles showed a very promising capability for reducing ROS levels and further treating OA.

Chondrocyte Aging: The Molecular Determinants and Therapeutic Opportunities

Osteoarthritis (OA) is a joint degenerative disease that is an exceedingly common problem associated with aging. Aging is the principal risk factor for OA, but damage-related physiopathology of articular chondrocytes probably drives the mechanisms of joint degeneration by a progressive decline in the homeostatic and regenerative capacity of cells. Cellular aging is the manifestation of a complex interplay of cellular and molecular pathways underpinned by transcriptional, translational, and epigenetic mechanisms and niche factors, and unraveling this complexity will improve our understanding of underlying molecular changes that affect the ability of the articular cartilage to maintain or regenerate itself. This insight is imperative for developing new cell and drug therapies for OA disease that will target the specific causes of age-related functional decline. This review explores the key age-related changes within articular chondrocytes and discusses the molecular mechanisms that are commonly perturbed as cartilage ages and degenerates. Current efforts and emerging potential therapies in treating OA that are being employed to halt or decelerate the aging processes are also discussed.

Mass Spectrometry-based Biomarkers for Knee Osteoarthritis: A Systematic Review

Introduction: Knee osteoarthritis (OA) is a joint disease, affecting multiple tissues in the joint. Early detection and intervention may delay OA development and avoid total knee arthroplasty. Specific biomarker profiles for early detection and guiding clinical decision-making of OA have not yet been identified. One technique that can contribute to the finding of this "OA biomarker" is mass spectrometry (MS), which offers the possibility to analyze different molecules in tissues or fluids. Several proteomic, lipidomic, metabolomic and other -omic approaches aim to identify these molecular profiles; however, variation in methods and techniques complicate the finding of promising candidate biomarkers.Areas covered: In this systematic review, we aim to provide an overview of molecules in OA knee patients. Possible biomarkers in several tissue types of OA and non-OA patients, as well as current limitations and possible future suggestions will be discussed.Expert opinion: According to this review, we do not believe one specific biomarker will function as predictive molecule for OA. Likely, a group of molecules will give insight in OA development and possible therapeutic targets. For clinical implementation of MS-analysis in clinical decision-making, standardized procedures, large cohort studies and sharing protocols and data is necessary.

The Implication of Reactive Oxygen Species and Antioxidants in Knee Osteoarthritis

Knee osteoarthritis (KOA) is a chronic multifactorial pathology and a current and essential challenge for public health, with a negative impact on the geriatric patient's quality of life. The pathophysiology is not fully known; therefore, no specific treatment has been found to date. The increase in the number of newly diagnosed cases of KOA is worrying, and it is essential to reduce the risk factors and detect those with a protective role in this context. The destructive effects of free radicals consist of the acceleration of chondrosenescence and apoptosis. Among other risk factors, the influence of redox imbalance on the homeostasis of the osteoarticular system is highlighted. The evolution of KOA can be correlated with oxidative stress markers or antioxidant status. These factors reveal the importance of maintaining a redox balance for the joints and the whole body's health, emphasizing the importance of an individualized therapeutic approach based on antioxidant effects. This paper aims to present an updated picture of the implications of reactive oxygen species (ROS) in KOA from pathophysiological and biochemical perspectives, focusing on antioxidant systems that could establish the premises for appropriate treatment to restore the redox balance and improve the condition of patients with KOA.

TLR4, RAGE, and p-JNK/JNK mediated inflammatory aggression in osteoathritic human chondrocytes are counteracted by redox-sensitive phenolic olive compounds: Comparison with ibuprofen

Osteoarthritic chondrocytes show an over-activity of inflammatory catabolic mediators, and olive products have attracted attention because they were discovered to have some benefits on osteoarthritis patients. We investigated the mechanisms of action of olive leaf polyphenolic compounds in osteoarthritic chondrocytes (OACs) using a standardized leaf extract, ZeyEX, and its main phenolic component, oleuropein, also compared with anti-inflammatory drug ibuprofen. OACs, isolated from joint-cartilages of Grade 4 OA patients, were found to express COMP and MMP-9 throughout their culture period. ZeyEX, oleuropein, and ibuprofen increased cell viability at concentrations of 1-100 nM, did not change at 500 nM-50 μM, but inhibited at ≥100 μM. The adherence profile of OACs increased with 1 μM of ibuprofen or ZeyEX and 10 nM-1 μM oleuropein. Although the markers for oxidative and nitrosative stresses (ROS and 3-NT) generally inhibited by three agents, the inhibitory effect of ZeyEX on 3-NT emerged dramatically (1 nM-10 μM). Lipid-hydroperoxides and HNE-adducts were also inhibited by each agent, but AGE-adducts unchanged by oleuropein while reduced by ZeyEX and ibuprofen. Inflammatory biomarkers, IL-1β, IL-6, Casp-1/ICE, and TNF-α, were inhibited by three agents, however osteopontin and GM-CSF by only ZeyEX and ibuprofen. A decreased COMP, TLR4, and RAGE expression levels were observed by three agents, but only the effects of ZeyEX was concentration-dependent. In particular, ZeyEX and oleuropein improved COL2, inhibited p-JNK/JNK, and increased GPx. COX2 was only inhibited by ibuprofen. The results indicate that polyphenolic-olive compounds counteract redox-sensitive inflammatory aggressions in osteoarthritic chondrocytes that may stop the progression of pathology and allow regeneration.

Exquisite design of injectable Hydrogels in Cartilage Repair

Cartilage damage is still a threat to human beings, yet there is currently no treatment available to fully restore the function of cartilage. Recently, due to their unique structures and properties, injectable hydrogels have been widely studied and have exhibited high potential for applications in therapeutic areas, especially in cartilage repair. In this review, we briefly introduce the properties of cartilage, some articular cartilage injuries, and now available treatment strategies. Afterwards, we propose the functional and fundamental requirements of injectable hydrogels in cartilage tissue engineering, as well as the main advantages of injectable hydrogels as a therapy for cartilage damage, including strong plasticity and excellent biocompatibility. Moreover, we comprehensively summarize the polymers, cells, and bioactive molecules regularly used in the fabrication of injectable hydrogels, with two kinds of gelation, i.e., physical and chemical crosslinking, which ensure the excellent design of injectable hydrogels for cartilage repair. We also include novel hybrid injectable hydrogels combined with nanoparticles. Finally, we conclude with the advances of this clinical application and the challenges of injectable hydrogels used in cartilage repair.

Phylogenetic and physiological signals in metazoan fossil biomolecules

Proteins, lipids, and sugars establish animal form and function. However, the preservation of biological signals in fossil organic matter is poorly understood. Here, we used high-resolution in situ Raman microspectroscopy to analyze the molecular compositions of 113 Phanerozoic metazoan fossils and sediments. Proteins, lipids, and sugars converge in composition during fossilization through lipoxidation and glycoxidation to form endogenous N-, O-, and S-heterocyclic polymers. Nonetheless, multivariate spectral analysis reveals molecular heterogeneities: The relative abundance of glycoxidation and lipoxidation products distinguishes different tissue types. Preserved chelating ligands are diagnostic of different modes of biomineralization. Amino acid-specific fossilization products retain phylogenetic information and capture higher-rank metazoan relationships. Molecular signals survive in deep time and provide a powerful tool for reconstructing the evolutionary history of animals.

Extracellular matrix mechanics regulate transfection and SOX9-directed differentiation of mesenchymal stem cells

Gene delivery within hydrogel matrices can potentially direct mesenchymal stem cells (MSCs) towards a chondrogenic fate to promote regeneration of cartilage. Here, we investigated whether the mechanical properties of the hydrogel containing the gene delivery systems could enhance transfection and chondrogenic programming of primary human bone marrow-derived MSCs. We developed collagen-I-alginate interpenetrating polymer network hydrogels with tunable stiffness and adhesion properties. The hydrogels were activated with nanocomplexed SOX9 polynucleotides to direct chondrogenic differentiation of MSCs. MSCs transfected within the hydrogels showed higher expression of chondrogenic markers compared to MSCs transfected in 2D prior to encapsulation. The nanocomplex uptake and resulting expression of transfected SOX9 were jointly enhanced by increased stiffness and cell-adhesion ligand density in the hydrogels. Further, transfection of SOX9 effectively induced MSCs chondrogenesis and reduced markers of hypertrophy compared to control matrices. These findings highlight the importance of matrix stiffness and adhesion as design parameters in gene-activated matrices for regenerative medicine. STATEMENT OF SIGNIFICANCE: Gene-activated matrices (GAMs) are biodegradable polymer networks integrating gene therapies, and they are promising technologies for supporting tissue regeneration. Despite this interest, there is still limited information on how to rationally design these systems. Here, we provide a systematic study of the effect of matrix stiffness and cell adhesion ligands on gene transfer efficiency. We show that high stiffness and the presence of cell-binding sites promote transfection efficiency and that this result is related to more efficient internalization and trafficking of the gene therapies. GAMs with optimized mechanical properties can induce cartilage formation and result in tissues with better characteristics for articular cartilage tissue engineering as compared to previously described standard methods.

Therapeutic "Tool" in Reconstruction and Regeneration of Tissue Engineering for Osteochondral Repair

Repairing osteochondral defects to restore joint function is a major challenge in regenerative medicine. However, with recent advances in tissue engineering, the development of potential treatments is promising. In recent years, in addition to single-layer scaffolds, double-layer or multilayer scaffolds have been prepared to mimic the structure of articular cartilage and subchondral bone for osteochondral repair. Although there are a range of different cells such as umbilical cord stem cells, bone marrow mesenchyml stem cell, and others that can be used, the availability, ease of preparation, and the osteogenic and chondrogenic capacity of these cells are important factors that will influence its selection for tissue engineering. Furthermore, appropriate cell proliferation and differentiation of these cells is also key for the optimal repair of osteochondral defects. The development of bioreactors has enhanced methods to stimulate the proliferation and differentiation of cells. In this review, we summarize the recent advances in tissue engineering, including the development of layered scaffolds, cells, and bioreactors that have changed the approach towards the development of novel treatments for osteochondral repair.

AdipoRon promotes diabetic fracture repair through endochondral ossification-based bone repair by enhancing survival and differentiation of chondrocytes

Diabetic bone defects may exhibit impaired endochondral ossification (ECO) leading to delayed bone repair. AdipoRon, a receptor agonist of adiponectin polymers, can ameliorate diabetes and related complications, as well as overcome the disadvantages of the unstable structure of artificial adiponectin polymers. Here, the effects of AdipoRon on the survival and differentiation of chondrocytes in a diabetic environment were explored focusing on related mechanisms in gene and protein levels. In vivo, AdipoRon was applied to diet-induced-obesity (DIO) mice, a model of obesity and type 2 diabetes, with femoral fracture. Sequential histological evaluations and micro-CT were examined for further verification. We found that AdipoRon could ameliorate cell viability, apoptosis, and reactive oxygen species (ROS) production and promote mRNA expression of chondrogenic markers and cartilaginous matrix production of ATDC5 cells in high glucose medium via activating ERK1/2 pathway. Additionally, DIO mice with intragastric AdipoRon administration had more neocartilage and accelerated new bone formation. These data suggest that AdipoRon could stimulate bone regeneration via ECO in diabetes.

Highly bioavailable curcumin powder suppresses articular cartilage damage in rats with mono-iodoacetate (MIA)-induced osteoarthritis

This study was performed to investigate the effects of highly bioavailable curcumin as Theracurmin^® (TC) in rats with monosodium iodoacetate (MIA)-induced osteoarthritis (OA). Seventy-seven male Wistar rats were divided into six groups: normal, negative control (MIA only), positive control (Cerebrex), and three experimental groups treated with 500, 1300, or 2600 mg/kg of TC for 5 weeks. MIA injection-induced OA caused 30% weight-bearing imbalance whereas weight bearing imbalance was significantly improved in the TC groups. Mankin scores revealed TC treatment had significantly ameliorated cartilage damage and chondrocyte decrease. The expressions of nitrotyrosine, tumor necrosis factor-α, phosphorylated nuclear factor kappa B cells, and cleaved caspase-3 were markedly increased in rat with MIA-induced OA, but the TC-treated groups exhibited a significant reduction in the number of immunoreactive cells in a dose-dependent manner. In conclusion, administration of TC contributes to the anti-arthritic effect in rat with MIA-induced OA.

Discovery and analysis of methylation quantitative trait loci (mQTLs) mapping to novel osteoarthritis genetic risk signals

OBJECTIVE

Osteoarthritis (OA) is polygenic with over 90 independent genome-wide association loci so far reported. A key next step is the identification of target genes and the molecular mechanisms through which this genetic risk operates. The majority of OA risk-conferring alleles are predicted to act by modulating gene expression. DNA methylation at CpG dinucleotides may be a functional conduit through which this occurs and is detectable by mapping methylation quantitative trait loci, or mQTLs. This approach can therefore provide functional insight into OA risk and will prioritize genes for subsequent investigation. That was our goal, with a focus on the largest set of OA loci yet to be reported.

METHOD

We investigated DNA methylation, genotype and RNA sequencing data derived from the cartilage of patients who had undergone arthroplasty and combined this with in silico analyses of expression quantitative trait loci, epigenomes and chromatin interactions.

RESULTS

We investigated 42 OA risk loci and in ten of these we identified 24 CpGs in which methylation correlated with genotype (false discovery rate (FDR) P-values ranging from 0.049 to 1.73x10^-25). In silico analyses of these mQTLs prioritised genes and regulatory elements at the majority of the ten loci, with COLGALT2 (encoding a collagen galactosyltransferase), COL11A2 (encoding a polypeptide chain of type XI collagen) and WWP2 (encoding a ubiquitin ligase active during chondrogenesis) emerging as particularly compelling target genes.

CONCLUSION

We have highlighted the pivotal role of DNA methylation as a link between genetic risk and OA and prioritized genes for further investigation.

Intra-hydrogel culture prevents transformation of mesenchymal stem cells induced by monolayer expansion

In this study, we report that the intra-hydrogel culture system mitigates the transformation of mesenchymal stem cells (MSCs) induced by two-dimensional (2D) expansion. MSCs expanded in monolayer culture prior to encapsulation in collagen hydrogels (group eMSCs-CH) featured impaired stemness in chondrogenesis, comparing with the freshly isolated bone marrow mononuclear cells seeded directly in collagen hydrogels (group fMSCs-CH). The molecular mechanism of the in vitro expansion-triggered damage to MSCs was detected through genome-wide microarray analysis. Results indicated that pathways such as proteoglycans in cancer and pathways in cancer expansion were highly enriched in eMSCs-CH. And multiple up-regulated oncoma-associated genes were verified in eMSCs-CH compared with fMSCs-CH, indicating that expansion in vitro triggered cellular transformation was associated with signaling pathways related to tumorigenicity. Besides, focal adhesion (FA) and mitogen-activated protein kinase (MAPK) signaling pathways were also involved in in vitro expansion, indicating restructuring of the cell architecture. Thus, monolayer expansion in vitro may contribute to vulnerability of MSCs through the regulation of FA and MAPK. This study indicates that intra-hydrogel culture can mitigate the monolayer expansion induced transformation of MSCs and maintain the uniformity of the stem cells, which is a viable in vitro culture system for stem cell therapy.

High glucose-induced excessive reactive oxygen species promote apoptosis through mitochondrial damage in rat cartilage endplate cells

Diabetes mellitus (DM) is an important factor in intervertebral disc degeneration (IDD). Apoptosis of cartilage endplate (CEP) cells is one of the initiators of IDD. However, the effects of high glucose on CEP cells are still unknown. Therefore, we conducted the present study to evaluate the effects of high glucose on CEP cells and to identify the mechanisms of those effects. Rat CEP cells were isolated and cultured in 10% foetal bovine serum (FBS, normal control) or high-glucose medium (10% FBS + 0.1 M glucose or 10% FBS + 0.2 M glucose, experimental conditions) for 1 or 3 days. In addition, CEP cells were treated with 0.2 M glucose for 3 days in the presence or absence of alpha-lipoic acid (ALA, 0.15 M). Flow cytometry was performed to identify and quantify the degree of apoptosis. The expression of reactive oxygen species (ROS) was assessed by flow cytometry, and mitochondrial damage (mitochondrial membrane potential) was assessed by fluorescence microscopy. Furthermore, the expression levels of cleaved caspase-3, cleaved caspase-9, Bcl-2, Bax, and cytochrome c were evaluated by Western blotting. High glucose significantly increased apoptosis and ROS accumulation in CEP cells in a dose- and time-dependent manner. Meanwhile, a disrupted mitochondrial membrane potential was detected in rat CEP cells cultured in the two high glucose concentrations. Incubating in high glucose enhanced the expression levels of cleaved caspase-3, cleaved caspase-9, Bax, and cytochrome c but decreased the level of the anti-apoptotic protein Bcl-2. ALA inhibited the expression of cleaved caspase-3, cleaved caspase-9, Bax, and cytochrome c but enhanced the expression of Bcl-2. ALA also prevented disruption of the mitochondrial membrane potential in CEP cells. This study demonstrates that high glucose-induced excessive reactive oxygen species promote mitochondrial damage, thus causing apoptosis in rat CEP cells in a dose- and time-dependent manner. ALA could prevent mitochondrial damage and apoptosis caused by high glucose in CEP cells. The results suggest that appropriate blood glucose control may be the key to preventing IDD in diabetic patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2476-2483, 2018.

Non-enzymatic cross-linking of collagen type II fibrils is tuned via osmolality switch

An important aspect in cartilage ageing is accumulation of advanced glycation end products (AGEs) after exposure to sugars. Advanced glycation results in cross-links formation between the collagen fibrils in articular cartilage, hampering their flexibility and making cartilage more brittle. In the current study, we investigate whether collagen cross-linking after exposure to sugars depends on the stretching condition of the collagen fibrils. Healthy equine cartilage specimens were exposed to l-threose sugar and placed in hypo-, iso-, or hyper-osmolal conditions that expanded or shrank the tissue and changed the 3D conformation of collagen fibrils. We applied micro-indentation tests, contrast enhanced micro-computed tomography, biochemical measurement of pentosidine cross-links, and cartilage surface color analysis to assess the effects of advanced glycation cross-linking under these different conditions. Swelling of extracellular matrix due to hypo-osmolality made cartilage less susceptible to advanced glycation, namely, the increase in effective Young's modulus was approximately 80% lower in hypo-osmolality compared to hyper-osmolality and pentosidine content per collagen was 47% lower. These results indicate that healthy levels of glycosaminoglycans not only keep cartilage stiffness at appropriate levels by swelling and pre-stressed collagen fibrils, but also protect collagen fibrils from adverse effects of advanced glycation. These findings highlight the fact that collagen fibrils and therefore cartilage can be protected from further advanced glycation ("ageing") by maintaining the joint environment at sufficiently low osmolality. Understanding of mechanochemistry of collagen fibrils provided here might evoke potential ageing prohibiting strategies against cartilage deterioration. © 2018 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:1929-1936, 2018.

Glycation marker glucosepane increases with the progression of osteoarthritis and correlates with morphological and functional changes of cartilage in vivo

Background

Changes of serum concentrations of glycated, oxidized, and nitrated amino acids and hydroxyproline and anticyclic citrullinated peptide antibody status combined by machine learning techniques in algorithms have recently been found to provide improved diagnosis and typing of early-stage arthritis of the knee, including osteoarthritis (OA), in patients. The association of glycated, oxidized, and nitrated amino acids released from the joint with development and progression of knee OA is unknown. We studied this in an OA animal model as well as interleukin-1β-activated human chondrocytes in vitro and translated key findings to patients with OA.

Methods

Sixty male 3-week-old Dunkin-Hartley guinea pigs were studied. Separate groups of 12 animals were killed at age 4, 12, 20, 28 and 36 weeks, and histological severity of knee OA was evaluated, and cartilage rheological properties were assessed. Human chondrocytes cultured in multilayers were treated for 10 days with interleukin-1β. Human patients with early and advanced OA and healthy controls were recruited, blood samples were collected, and serum or plasma was prepared. Serum, plasma, and culture medium were analyzed for glycated, oxidized, and nitrated amino acids.

Results

Severity of OA increased progressively in guinea pigs with age. Glycated, oxidized, and nitrated amino acids were increased markedly at week 36, with glucosepane and dityrosine increasing progressively from weeks 20 and 28, respectively. Glucosepane correlated positively with OA histological severity (r = 0.58, p < 0.0001) and instantaneous modulus (r = 0.52–0.56; p < 0.0001), oxidation free adducts correlated positively with OA severity (p < 0.0009–0.0062), and hydroxyproline correlated positively with cartilage thickness (p < 0.0003–0.003). Interleukin-1β increased the release of glycated and nitrated amino acids from chondrocytes in vitro. In clinical translation, plasma glucosepane was increased 38% in early-stage OA (p < 0.05) and sixfold in patients with advanced OA (p < 0.001) compared with healthy controls.

Conclusions

These studies further advance the prospective role of glycated, oxidized, and nitrated amino acids as serum biomarkers in diagnostic algorithms for early-stage detection of OA and other arthritic disease. Plasma glucosepane, reported here for the first time to our knowledge, may improve early-stage diagnosis and progression of clinical OA.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1636-6) contains supplementary material, which is available to authorized users.

Type 2 diabetes patients have accelerated cartilage matrix degeneration compared to diabetes free controls: data from the Osteoarthritis Initiative

PURPOSE

Osteoarthritis (OA) and diabetes mellitus (DM) share common risk factors with a potential underlying relationship between both diseases. The purpose of this study was to investigate the longitudinal effects of DM on cartilage deterioration over 24-months with MR-based T2 relaxation time measurements.

METHODS

From the Osteoarthritis Initiative (OAI) cohort 196 diabetics were matched in small sets for age, sex, BMI and Kellgren-Lawrence score with 196 non-diabetic controls. Knee cartilage semi-automatic segmentation was performed on 2D multi-slice multi-echo spin-echo sequences. Texture of cartilage T2 maps was obtained via grey level co-occurrence matrix analysis. Linear regression analysis was used to compare cross-sectional and changes in T2 and texture parameters between the groups.

RESULTS

Both study groups were similar in age (63.3 vs 63.0 years, P = 0.70), BMI (30.9 vs 31.2 kg/m2, P = 0.52), sex (female 53.6% vs 54.1%, P = 0.92) and KL score distribution (P = 0.97). In diabetics, except for the patella, all compartments showed a significantly higher increase in mean T2 values when compared to non-diabetic controls. Global T2 values increased almost twice as much; 1.77ms vs 0.98ms (0.79ms [CI: 0.39,1.19]) (P < 0.001). Additionally, global T2 values showed a significantly higher increase in the bone layer (P = 0.006), and in a separate analysis of the texture parameters, diabetics also showed consistently higher texture values (P < 0.05), indicating a more disordered cartilage composition.

CONCLUSION

Cartilage T2 values in diabetics show a faster increase with a consistently more heterogeneous cartilage texture composition. DM seems to be a risk factor for developing early OA with an accelerated degeneration of the articular cartilage in the knee.

Diet Quality and Nutrient Intake of Urban Overweight and Obese Primarily African American Older Adults with Osteoarthritis

Diet quality may be a unique target for preventing and managing obesity-related osteoarthritis (OA). Using the Healthy Eating Index-2010 (HEI-2010), this study examined the nutrient intake and diet quality of 400 urban overweight and obese primarily African American older adults with self-reported lower extremity OA. Associations between sociodemographic and health-related factors and diet quality were explored. Participants (mean age 67.8 years, SD 5.9) were included. Habitual dietary intake was assessed using a food frequency questionnaire (FFQ). Nutrient intake and diet quality were calculated from the FFQ. Results indicated that diet quality needs improvement (HEI-2010: 66.3 (SD 10.5)). Age, body mass index, employment (multivariable model only), and OA severity (bivariate model only) were significant predictors of HEI-2010 total score in linear models. Mean intakes for fiber, calcium, and vitamin D were below recommendations, while percentage of calories as total fat exceeded recommendations. These findings can inform future dietary intervention trials and public health messaging for a sub-population at a high risk for obesity-related OA.

Association between Dietary Glycemic Index and Knee Osteoarthritis: The Korean National Health and Nutrition Examination Survey 2010-2012

BACKGROUND

Obesity and metabolic abnormalities are important risk factors for knee osteoarthritis (KOA). Recent epidemiologic studies have found that a high glycemic index (GI) and glycemic load (GL) diet are associated with a higher risk for metabolic complications and cardiovascular mortality.

OBJECTIVE

We aimed to examine the association between dietary GI, dietary GL, and KOA among Korean adults.

DESIGN

This was a cross-sectional study that analyzed data obtained from the Korean National Health and Nutrition Examination Survey 2010-2012.

PARTICIPANTS/SETTING

A total of 9,203 participants (5,275 women) aged ≥50 years were included.

MAIN OUTCOME MEASURES

KOA was defined as the presence of radiographic features of Kellgren-Lawrence grade ≥2. Chronic knee pain was defined as the presence of knee pain for more than 30 days during the past 3 months. Dietary information was collected using a single 24-hour recall method.

STATISTICAL ANALYSES PERFORMED

The association between the quintiles of dietary GI and dietary GL and knee conditions was analyzed using a multinomial logistic regression analysis adjusting for age, physical activity, obesity, hypertension and diabetes, serum low-density lipoprotein, and total energy intake.

RESULTS

Among the women, the association between dietary GI and symptomatic KOA was: quintile 1: 1.00 (reference); quintile 2: 1.29 (95% CI 0.87 to 1.92); quintile 3: 1.59 (95% CI 1.11 to 2.28); quintile 4: 1.74 (95% CI 1.21 to 2.51); and quintile 5: 1.77 (95% CI 1.20 to 2.60) (P=0.001). Chronic knee pain without KOA was associated with dietary GI; however, this association was not linear across quintiles. There was no significant association between dietary GI and asymptomatic KOA. Among the men, no significant association was found between dietary GI and any knee conditions. There was no significant association between dietary GL and KOA in both men and women.

CONCLUSIONS

There was a significant positive association between dietary GI and symptomatic KOA in women.

Distinct metabolic programs induced by TGF-β1 and BMP2 in human articular chondrocytes with osteoarthritis

Objectives

Cellular energy metabolism is important for the function of all tissues, including cartilage. Recent studies indicate that superficial and deep subpopulations of articular chondrocytes (ACs) have distinct metabolic profiles. At the cellular and molecular level, osteoarthritis (OA) is characterised by alteration from a healthy homoeostatic state towards a catabolic state. Several molecular pathways, including transforming growth factor beta (TGF-β) and bone morphogenetic protein (BMP) signalling, have been identified as critical players in the pathogenesis and progression of OA. However, the manner in which these factors influence cellular energy metabolism in ACs is not well understood. This study investigates the effect of TGF-β or BMP signalling on energy metabolism in human articular chondrocytes (hACs).

Methods

ACs were isolated from residual macroscopically full thickness and intact cartilage from the femoral condyle of human samples obtained from patients with OA. ACs were treated with Vehicle (control), TGF-β1 or BMP2 for 48–72 hours. Metabolic assays were performed to determine glucose consumption, lactate production and adenosine triphosphate (ATP) production, whereas the mitochondrial stress test was performed to determine oxygen consumption rate. Protein was isolated to assess translational activity and was evaluated using Western blot.

Results

We showed that TGF-β1, known to maintain chondrocyte homoeostasis, stimulated glycolysis by upregulating key glycolytic factors, such as glucose transporter 1 (Glut1) and hexokinase II, while reducing oxidative phosphorylation in hACs. In contrast, BMP2 enhanced mitochondrial metabolism and oxidative phosphorylation and had a minimal effect on key glycolytic regulators.

Conclusions

Our data revealed distinct metabolic programs induced by TGF-β1 and BMP2 in hACs, suggesting that the regulation of cellular metabolism may represent a new mechanism underlying the pathogenesis of OA.

The translational potential of this article

The findings define the regulation of energy metabolism as a potential novel therapeutic approach for the treatment of OA.

A promising novel formulation for articular cartilage regeneration: Preclinical evaluation of a treatment that produces SOX9 overexpression in human synovial fluid cells

Osteoarthritis (OA) is a chronic disorder of synovial joints, in which there is progressive softening and disintegration of the articular cartilage. OA is the most common form of arthritis, and is the primary cause of disability and impaired quality of life in the elderly. Despite considerable medical necessity, no treatment has yet been proven to act as a disease‑modifying agent that may halt or reverse the structural progression of OA. The replacement of the joint with a prosthesis appears to be the best option in the advanced stages of the disease. A formulation (BIOF2) for cartilage regeneration has been recently developed. The present study evaluated the effects of BIOF2 on gene expression in human cell cultures, followed by efficacy trials in three OA animal models. Human synovial fluid cells that were exposed to the formulation exhibited increased transcription factor SOX‑9 (SOX9; chondrogenic factor) expression, and decreased mimecan (mineralization inducer) and macrophage‑stimulating protein receptor (osteoclastogenic factor) expression. The intra‑articular application of BIOF2 in the animal models significantly increased cartilage thickness from 12 to 31% at 28 days, compared with articular cartilage treated with saline solution. The articular area and number of chondrocytes additionally increased significantly, maintaining an unaltered chondrocyte/mm2 proportion. Evaluation of the histological architecture additionally displayed a decrease in the grade of articular damage in the groups treated with BIOF2. In conclusion, BIOF2 has proven to be effective for treating OA in animal models, most likely due to SOX9 overexpression in articular cells.

The interrelation of osteoarthritis and diabetes mellitus: considering the potential role of interleukin-10 and in vitro models for further analysis

INTRODUCTION

Today, not only the existence of an interrelation between obesity/adipositas and osteoarthritis (OA) but also the association of OA and diabetes mellitus (DM) are widely recognized. Nevertheless, shared influence factors facilitating OA development in DM patients still remain speculative up until now. To supplement the analysis of clinical data, appropriate in vitro models could help to identify shared pathogenetic pathways. Informative in vitro studies could later be complemented by in vivo data obtained from suitable animal models.

MATERIALS AND METHODS

Therefore, this detailed review of available literature was undertaken to discuss and compare the results of currently published in vitro studies focusing on the interrelation between OA, the metabolic syndrome and DM and to propose models to further study the molecular pathways.

RESULTS

The survey of literature presented here supports the hypothesis that the pathogenesis of OA in DM is based on imbalanced molecular pathways with a putative crucial role of antiinflammatory cytokines such as IL-10.

CONCLUSION

Future development of versatile micro-scaled in vitro models such as combining DM and OA on chip could allow the identification of common pathogenetic pathways and might help to develop novel therapeutic strategies.

Enzymatic and non-enzymatic detoxification of 4-hydroxynonenal: Methodological aspects and biological consequences

4-Hydroxynonenal (HNE), an electrophilic end-product deriving from lipid peroxidation, undergoes a heterogeneous set of biotransformations including enzymatic and non-enzymatic reactions. The former mostly involve red-ox reactions on the HNE oxygenated functions (phase I metabolism) and GSH conjugations (phase II) while the latter are due to the HNE capacity to spontaneously condense with nucleophilic sites within endogenous molecules such as proteins, nucleic acids and phospholipids. The overall metabolic fate of HNE has recently attracted great interest not only because it clearly determines the HNE disposal, but especially because the generated metabolites and adducts are not inactive molecules (as initially believed) but show biological activities even more pronounced than those of the parent compound as exemplified by potent pro-inflammatory stimulus induced by GSH conjugates. Similarly, several studies revealed that the non-enzymatic reactions, initially considered as damaging processes randomly involving all endogenous nucleophilic reactants, are in fact quite selective in terms of both reactivity of the nucleophilic sites and stability of the generated adducts. Even though many formed adducts retain the expected toxic consequences, some adducts exhibit well-defined beneficial roles as documented by the protective effects of sublethal concentrations of HNE against toxic concentrations of HNE. Clearly, future investigations are required to gain a more detailed understanding of the metabolic fate of HNE as well as to identify novel targets involved in the biological activity of the HNE metabolites. These studies are and will be permitted by the continuous progress in the analytical methods for the identification and quantitation of novel HNE metabolites as well as for proteomic analyses able to offer a comprehensive picture of the HNE-induced adducted targets. On these grounds, the present review will focus on the major enzymatic and non-enzymatic HNE biotransformations discussing both the molecular mechanisms involved and the biological effects elicited. The review will also describe the most important analytical enhancements that have permitted the here discussed advancements in our understanding of the HNE metabolic fate and which will permit in a near future an even better knowledge of this enigmatic molecule.

Friction-Induced Mitochondrial Dysregulation Contributes to Joint Deterioration in Prg4 Knockout Mice

Deficiency of PRG4 (lubricin), the boundary lubricant in mammalian joints, contributes to increased joint friction accompanied by superficial and upper intermediate zone chondrocyte caspase-3 activation, as shown in lubricin-null (Prg4^-/-) mice. Caspase-3 activity appears to be reversible upon the restitution of Prg4 either endogenously in vivo, in a gene trap mouse, or as an applied lubricant in vitro. In this study we show that intra-articular injection of human PRG4 in vivo in Prg4^-/- mice prevented caspase-3 activation in superficial zone chondrocytes and was associated with a modest decrease in whole joint friction measured ex vivo using a joint pendulum method. Non-lubricated Prg4^-/- mouse cartilage shows caspase cascade activation caused by mitochondrial dysregulation, and significantly higher levels of peroxynitrite (ONOO^- and ^-OH) and superoxide (O^-₂) compared to Prg4^+/+ and Prg4^+/- cartilage. Enzymatic activity levels of caspase 8 across Prg4 mutant mice were not significantly different, indicating no extrinsic apoptosis pathway activation. Western blots showed caspase-3 and 9 activation in Prg4^-/- tissue extracts, and the appearance of nitrosylated Cys163 in the active cleft of caspase-3 which inhibits its enzymatic activity. These findings are relevant to patients at risk for arthrosis, from camptodactyl-arthropathy-coxa vara-pericarditis (CACP) syndrome and transient lubricin insufficiency due to trauma and inflammation.

Injectable hydrogels for cartilage and bone tissue engineering

Tissue engineering has become a promising strategy for repairing damaged cartilage and bone tissue. Among the scaffolds for tissue-engineering applications, injectable hydrogels have demonstrated great potential for use as three-dimensional cell culture scaffolds in cartilage and bone tissue engineering, owing to their high water content, similarity to the natural extracellular matrix (ECM), porous framework for cell transplantation and proliferation, minimal invasive properties, and ability to match irregular defects. In this review, we describe the selection of appropriate biomaterials and fabrication methods to prepare novel injectable hydrogels for cartilage and bone tissue engineering. In addition, the biology of cartilage and the bony ECM is also summarized. Finally, future perspectives for injectable hydrogels in cartilage and bone tissue engineering are discussed.

Protein oxidation, nitration and glycation biomarkers for early-stage diagnosis of osteoarthritis of the knee and typing and progression of arthritic disease

Background

There is currently no blood-based test for detection of early-stage osteoarthritis (OA) and the anti-cyclic citrullinated peptide (CCP) antibody test for rheumatoid arthritis (RA) has relatively low sensitivity for early-stage disease. Morbidity in arthritis could be markedly decreased if early-stage arthritis could be routinely detected and classified by clinical chemistry test. We hypothesised that damage to proteins of the joint by oxidation, nitration and glycation, and with signatures released in plasma as oxidized, nitrated and glycated amino acids may facilitate early-stage diagnosis and typing of arthritis.

Methods

Patients with knee joint early-stage and advanced OA and RA or other inflammatory joint disease (non-RA) and healthy subjects with good skeletal health were recruited for the study (n = 225). Plasma/serum and synovial fluid was analysed for oxidized, nitrated and glycated proteins and amino acids by quantitative liquid chromatography-tandem mass spectrometry. Data-driven machine learning methods were employed to explore diagnostic utility of the measurements for detection and classifying early-stage OA and RA, non-RA and good skeletal health with training set and independent test set cohorts.

Results

Glycated, oxidized and nitrated proteins and amino acids were detected in synovial fluid and plasma of arthritic patients with characteristic patterns found in early and advanced OA and RA, and non-RA, with respect to healthy controls. In early-stage disease, two algorithms for consecutive use in diagnosis were developed: (1) disease versus healthy control, and (2) classification as OA, RA and non-RA. The algorithms featured 10 damaged amino acids in plasma, hydroxyproline and anti-CCP antibody status. Sensitivities/specificities were: (1) good skeletal health, 0.92/0.91; (2) early-stage OA, 0.92/0.90; early-stage RA, 0.80/0.78; and non-RA, 0.70/0.65 (training set). These were confirmed in independent test set validation. Damaged amino acids increased further in severe and advanced OA and RA.

Conclusions

Oxidized, nitrated and glycated amino acids combined with hydroxyproline and anti-CCP antibody status provided a plasma-based biochemical test of relatively high sensitivity and specificity for early-stage diagnosis and typing of arthritic disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-1154-3) contains supplementary material, which is available to authorized users.

Preserving the longevity of long-lived type II collagen and its implication for cartilage therapeutics

Human life expectancy has been steadily increasing at a rapid rate, but this increasing life span also brings about increases in diseases, dementia, and disability. A global burden of disease 2010 study revealed that hip and knee osteoarthritis ranked the 11th highest in terms of years lived with disability. Wear and tear can greatly influence the quality of life during ageing. In particular, wear and tear of the articular cartilage have adverse effects on joints and result in osteoarthritis. The articular cartilage uses longevity of type II collagen as the foundation around which turnover of proteoglycans and the homeostatic activity of chondrocytes play central roles thereby maintaining the function of articular cartilage in the ageing. The longevity of type II collagen involves a complex interaction of the scaffolding needs of the cartilage and its biochemical, structural and mechanical characteristics. The covalent cross-linking of heterotypic polymers of collagens type II, type IX and type XI hold together cartilage, allowing it to withstand ageing stresses. Discerning the biological clues in the armamentarium for preserving cartilage appears to be collagen cross-linking. Therapeutic methods to crosslink in in-vivo are non-existent. However intra-articular injections of polyphenols in vivo stabilize the cartilage and make it resistant to degradation, opening a new therapeutic possibility for prevention and intervention of cartilage degradation in osteoarthritis of aging.