Inflammation in osteoarthritis. Curr Opin Rheumatol. 2011;23:471-478. [PMID: 21788902 DOI: 10.1097/bor.0b013e328349c2b1]

Modulation of Hyaluronan Synthesis by the Interaction between Mesenchymal Stem Cells and Osteoarthritic Chondrocytes

Bone marrow mesenchymal stem cells (BM-MSCs) are considered a good source for cellular therapy in cartilage repair. But, their potential to repair the extracellular matrix, in an osteoarthritic environment, is still controversial. In osteoarthritis (OA), anti-inflammatory action and extracellular matrix production are important steps for cartilage healing. This study examined the interaction of BM-MSC and OA-chondrocyte on the production of hyaluronan and inflammatory cytokines in a Transwell system. We compared cocultured BM-MSCs and OA-chondrocytes with the individually cultured controls (monocultures). There was a decrease in BM-MSCs cell count in coculture with OA-chondrocytes when compared to BM-MSCs alone. In monoculture, BM-MSCs produced higher amounts of hyaluronan than OA-chondrocytes and coculture of BM-MSCs with OA-chondrocytes increased hyaluronan production per cell. Hyaluronan synthase-1 mRNA expression was upregulated in BM-MSCs after coculture with OA-chondrocytes, whereas hyaluronidase-1 was downregulated. After coculture, lower IL-6 levels were detected in BM-MSCs compared with OA-chondrocytes. These results indicate that, in response to coculture with OA-chondrocytes, BM-MSCs change their behavior by increasing production of hyaluronan and decreasing inflammatory cytokines. Our results indicate that BM-MSCs per se could be a potential tool for OA regenerative therapy, exerting short-term effects on the local microenvironment even when cell:cell contact is not occurring.

New developments in the treatment of osteoarthritis - focus on biologic agents

Osteoarthritis (OA) is one of the most common diseases around the world. Medical, social, and financial consequences oblige clinicians, surgeons, and researchers to focus on finding the best treatment option, to eradicate and stop this degenerative joint disease, in order to avoid surgical options which in many instances are over-indicated. Noninvasive treatments, such as anti-inflammatory drugs, physiotherapy, orthotic devices, dietary supplements, have demonstrated lack of effectiveness. The possibility to perform intra-articular injections with hyaluronic acid, corticosteroids, or the newest but criticized treatment based on platelet-rich plasma (PRP) has changed the management of OA disease. The use of PRP has led to many differences in treatment since there is a lack of consensus about protocols, indications, number of doses, cost-effectiveness, and duration of the treatment. Many publications have suggested efficacy in tendon injuries, but when PRP has been indicated to treat cartilage injuries, things are more inconsistent. Some authors have reported their experience treating OA with PRP, and it seems that, if well indicated, it is an option as a supplementary therapy. Therefore, we need to understand that OA is a mechanical disease which not only produces changes in radiographs, but also affects the quality of life. Pathogenesis of OA has been well explained, providing us new knowledge and future possibilities to improve the clinical approach. From basic science to surgery, there is a great field we all need to contribute to, because the general population is aging and total joint replacements should not be the only solution for OA. So herein is an actual review of the developments for treating OA with biologics, intended to be useful for the population inside orthopedics who could be called bio-orthopedists, since OA is a molecular homeostasis disbalance between catabolism and anabolism triggered by mechanical stress.

Inflammatory response of cultured rat synoviocytes challenged with synovial fluid from osteoarthritis patients correlates with their radiographic grading: a pilot study

The inflammatory nature of synovial fluid (SF) of varying grade osteoarthritis (OA) patients was estimated by measuring pro-inflammatory factors and through a unique cell-challenge experiment. SF samples were collected from six OA and one non-OA patient; spanning Kellgren-Lawrence (KL) grades were analyzed for interlukin-1-beta (IL-1β), nitric oxide (NO) and its derivatives, and glycosaminoglycan (GAG). Levels of IL-1β, NO, and GAG in SF did not correlate with KL grades of the patients studied. In the cell-challenge experiment, cultured rat synoviocyte fibroblasts (RSFs) were challenged by the patient's SFs with and without pre-treatment of IL-1β and lipopolysaccharide (LPS). NO released by the cells was taken as an indicator of inflammation. SFs from KL grades 2 and 3 induced maximum inflammation in cultured RSFs (grade 2 64.61 ± 4.8 and 89.51 ± 5.6 μM/ml after 48 and 72 h, grade 3 58.27 ± 2.7 and 64.22 ± 2.8 μM/ml after 48 and 72 h, respectively). Similar trend was observed in RSF pretreated with either recombinant IL-1β or LPS suggesting that SF from patients KL grades 2 and 3 accumulates more pro-inflammatory factors. IL-1β-pre-treated RSFs challenged by SF for 72 h showed 234.41 ± 17.6 μM/ml increase (patient 3, grade 3), whereas higher NO after LPS pre-treatment was recorded (118.92 ± 6.2 μM/ml; patient 3, grade 3). Interestingly, SFs from grade 1 and non-OA patient could reduce released NO to 27.10 ± 2.2 μM/ml showing potency to alleviate inflammation. These interesting findings, however, need to be confirmed on a wider number of patients, which may offer significant therapeutic application in treatment of OA.

Emerging drugs for the treatment of knee osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is the most prevailing form of joint disease, with symptoms affecting 10 - 12% of the adult population with a projection of a 50% increase in prevalence in the next two decades. The disease characteristics are defined by articular cartilage damage, low-grade synovial inflammation and hypertrophic bone changes, leading to pain and functional deterioration. To date, available pain treatments are limited in their efficacy and have associated toxicities. No structural disease modification agents have been approved by regulatory agencies for this indication.

AREAS COVERED

We reviewed drugs in Phase II - III for OA pain and joint structure modification. Different aspects of structure modification are divided into targets of inflammatory pathway, cartilage catabolism and anabolism, and subchondral bone remodeling.

EXPERT OPINION

Further insight into the pathophysiology of the disease will allow for development of novel target classes focusing on the link between symptomatology and structural changes. Given the complexity of OA, one single therapy is unlikely to be universally and uniformly effective. Promising therapies are under development, but there are obstacles in the translation of treatment from preclinical models and trial designs need to be cognizant of the complex reasons for previous trial failures.

Magnetic Capture of a Molecular Biomarker from Synovial Fluid in a Rat Model of Knee Osteoarthritis

Biomarker development for osteoarthritis (OA) often begins in rodent models, but can be limited by an inability to aspirate synovial fluid from a rodent stifle (similar to the human knee). To address this limitation, we have developed a magnetic nanoparticle-based technology to collect biomarkers from a rodent stifle, termed magnetic capture. Using a common OA biomarker--the c-terminus telopeptide of type II collagen (CTXII)--magnetic capture was optimized in vitro using bovine synovial fluid and then tested in a rat model of knee OA. Anti-CTXII antibodies were conjugated to the surface of superparamagnetic iron oxide-containing polymeric particles. Using these anti-CTXII particles, magnetic capture was able to estimate the level of CTXII in 25 μL aliquots of bovine synovial fluid; and under controlled conditions, this estimate was unaffected by synovial fluid viscosity. Following in vitro testing, anti-CTXII particles were tested in a rat monoiodoacetate model of knee OA. CTXII could be magnetically captured from a rodent stifle without the need to aspirate fluid and showed tenfold changes in CTXII levels from OA-affected joints relative to contralateral control joints. Combined, these data demonstrate the ability and sensitivity of magnetic capture for post-mortem analysis of OA biomarkers in the rat.

Analgesic and anti-Inflammatory effect of UP3005, a botanical composition Containing two standardized extracts of Uncaria gambir and Morus alba

Background:

Osteoarthritis (OA) is a chronic debilitating degenerative joint disease characterized by cartilage degradation and synovial inflammation exhibited by clinical symptoms such as joint swelling, synovitis, and inflammatory pain. Present day pain relief therapeutics heavily relies on the use of prescription and over the counter nonsteroidal anti-inflammatory drugs as the first line of defense where their long-term usage causes detrimental gastrointestinal and cardiovascular-related side-effects. As a result, the need for evidence based safer and efficacious alternatives from natural sources to overcome the most prominent and disabling symptoms of arthritis is a necessity.

Materials and Methods:

Describe the anti-inflammatory and analgesic effect of UP3005, a composition that contains a standardized blend of two extracts from the leaf of Uncaria gambir and the root bark of Morus alba in carrageenan-induced rat paw edema, abdominal constriction (writhing’s) and ear swelling assays in mouse with oral dose ranges of 100–400 mg/kg.

Results:

In vivo, statistically significant improvement in pain resistance, and suppression of paw edema and ear thickness in animals treated with UP3005 were observed compared with vehicle-treated diseased rats and mice. Ibuprofen was used a reference compound in all the studies. In vitro, enzymatic inhibition activities of UP3005 were determined with IC50 values of 12.4 μg/ml, 39.8 μg/ml and 13.6 μg/ml in cyclooxygenase-2 (COX-1), COX-2 and lipoxygenase (5-LOX) enzyme activity assay, respectively.

Conclusions:

These data suggest that UP3005, analgesic and anti-inflammatory agent of botanical origin with balanced dual COX-LOX inhibition activity, could potentially be used for symptom management of OA.

Exogenous expression of IL-1Ra and TGF-β1 promotes in vivo repair in experimental rabbit osteoarthritis

OBJECTIVES

Potential gene therapy application of single and co-expression of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) and transforming growth factor-β1 (TGF-β1) to alter disease progression was investigated in an in-vivo rabbit model of osteoarthritis (OA).

METHOD

Sixteen young adult rabbits were randomly and equally divided into four groups: blank control group, IL-1Ra transfection group, TGF-β1 transfection group, and IL-1Ra/TGF-β1 double transfection group. Histological examinations were performed to monitor disease progression after haematoxylin and eosin (H&E) staining of articular cartilage. Immunohistochemistry was used to detect IL-1Ra and TGF-β1 in synovial membrane tissues. Exogenous IL-1Ra and TGF-β1 content was assessed in joint lavage fluid using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

ELISA measurements from the joint lavage fluid showed high expressions of IL-1Ra and TGF-β1 in the single and double transfection groups. Remarkably, concomitant reductions in IL-1β and tumour necrosis factor alpha (TNF-α) levels were observed in these single and double transfection groups. Radioimmunoassay (RIA)-based detection showed that IL-1β and TNF-α levels in the gene transfection groups were significantly lower compared to the blank control group, in parallel experiments. Importantly, injection of IL-1Ra and TGF-β1 expressing cartilage cells into joints led to a significant inhibition of cartilage matrix degradation. Finally, IL-1Ra and TGF-β1 expression in tissues correlated with disease reversal in the experimental group, with improved tissue architecture and collagen deposition.

CONCLUSIONS

Our results reveal that both single- and double-gene transfection of IL-1Ra and TGF-β1 promote extensive repair of damaged cartilage, and double transfections showed better recovery than single transfections, suggesting that co-expression of IL-1Ra and TGF-β1 inhibits degeneration and improves repair of articular cartilage in OA.

Chondrocyte miRNAs 221 and 483-5p respond to loss of matrix interaction by modulating proliferation and matrix synthesis

AIM

The purpose of this study was to identify the microRNAs that regulate the response of chondrocytes to loss of matrix interaction.

MATERIALS AND METHODS

MicroRNA and gene expression was compared in bovine cartilage and isolated chondrocytes using array analysis. Those microRNAs showing more than three-fold change in expression were verified by quantitative PCR after a stem-loop reverse transcription in bovine and human cartilage, and chondrocytes. Their function was investigated using target gene reporter construct expression, quantification of cell proliferation, and analysis of gene expression and matrix synthesis after transfection with microRNA mimics.

RESULTS

Only four microRNAs were confirmed to have a greater than three-fold change in expression after isolation of bovine or human chondrocytes from their extracellular matrix; miRs-221, -222 and -21 showed increased expression and miR-483-5p showed decreased expression. Transfection with a miR-221 mimic was shown to suppress expression of the cyclin-dependent kinase inhibitor p27 leading to the stimulation of chondrocyte proliferation. Transfection of chondrocytes with a miR-483-5p mimic was shown to suppress several members of the mitogen activated protein kinase (MAPK) pathway; a likely explanation of the increased matrix production observed.

CONCLUSIONS

microRNAs 221 and 483-5p respond to the loss of chondrocyte matrix interaction by respectively stimulating proliferation by suppression of inhibitors of cell division and suppression of matrix production possibly by release of inhibition of the MAPK pathway.

Cartilage repair in vivo: the role of migratory progenitor cells

The most common diseases of the joints and its tissues are osteoarthritis and rheumatoid arthritis, with osteoarthritis being anticipated to be the fourth leading cause of disability by the year 2020. To date, no truly causal therapies are available, and this has promoted tissue engineering attempts mainly involving mesenchymal stem cells. The goal of all tissue repairs would be to restore a fully functional tissue, here a hyaline articular cartilage. The hyaline cartilage is the most affected in osteoarthritis, where altered cell–matrix interactions gradually destroy tissue integrity. In rheumatoid arthritis, the inflammatory aspect is more important, and the cartilage tissue is destroyed by the invasion of tumor-like pannus tissue arising from the inflamed synovia. Furthermore, the fibrocartilage of the meniscus is clearly involved in the initiation of osteoarthritis, especially after trauma. Recent investigations have highlighted the role of migratory progenitor cells found in diseased tissues in situ. In osteoarthritis and rheumatoid arthritis, these chondrogenic progenitor cells are involved in regeneration efforts that are largely unsuccessful in diseased cartilage tissue. However, these progenitor cells are interesting targets for a cell-based regenerative therapy for joint diseases.

Matrine inhibits IL-1β-induced expression of matrix metalloproteinases by suppressing the activation of MAPK and NF-κB in human chondrocytes in vitro

Interleukin (IL)-1β plays an important role in promoting osteoarthritis (OA) lesions by inducing chondrocytes to secrete matrix metalloproteinases (MMPs), which degrade the extracellular matrix and facilitate chondrocyte apoptosis. Matrine was shown to exert anti-inflammatory effects. However, the role of matrine in OA is still unclear. Therefore, in this study, we investigated the effects of matrine on the expression of MMPs in IL-1β-treated human chondrocytes and the underlying mechanism. The cell viability of chondrocytes was detected by MTT assay. The cell apoptosis of chondrocytes was measured by flow cytometric analysis. The protein production of MMPs was determined by ELISA. The protein expression of phosphorylation of mitogen-activated protein kinases (MAPKs) and the inhibitor of kappaB alpha (IκBα) was determined by Western blot. Matrine significantly inhibited the IL-1β-induced apoptosis in chondrocytes. It also significantly inhibited the IL-1β-induced release of MMP-3 and MMP-13, and increased the production of TIMP-1. Furthermore, matrine inhibits the phosphorylation of p-38, extracellular regulated kinase (ERK), c-Jun-N-terminal kinase (JNK) and IκBα degradation induced by IL-1β in chondrocytes. Taken together, our results show that matrine inhibits IL-1β-induced expression of matrix metalloproteinases by suppressing the activation of MAPK and NF-κB in human chondrocytes in vitro. Therefore,-matrine may be beneficial in the treatment of OA.

Ageing and inflammation - A central role for mitochondria in brain health and disease

To develop successful therapies that prevent or treat neurodegenerative diseases requires an understanding of the upstream events. Ageing is by far the greatest risk factor for most of these diseases, and to clarify their causes will require an understanding of the process of ageing itself. Starting with the question Why do we age as individual organisms, but the line of pluripotent embryonic stem cells and germ cells carried by individuals and transmitted to descendants is immortal? this review discusses how the process of cellular differentiation leads to the accumulation of biological imperfections with ageing, and how these imperfections may be the cause of chronic inflammatory responses to stress that undermine cellular function. Both differentiation and inflammation involve drastic metabolic changes associated with alterations in mitochondrial dynamics that shift the balance between aerobic glycolysis and oxidative phosphorylation. With ageing, mitochondrial dysfunction can be both the cause and consequence of inflammatory processes and elicit metabolic adaptations that might be either protective or become progressively detrimental. It is argued here that an understanding of the relationship between metabolism, differentiation and inflammation is essential to understand the pathological mechanisms governing brain health and disease during ageing.

Synovial cytokine expression in ankle osteoarthritis depends on age and stage

PURPOSE

Aim of the study was the analysis of cytokine expression in ankle osteoarthritis (OA) hypothesizing age-dependent regulation patterns.

METHODS

Forty-nine patients undergoing an arthroscopy of the ankle with different stages of chronic OA were prospectively included in a clinical trial comparing the group <18 years (n = 9, Ø15.1 ± 2.0 years) with the older patients (≥18 years, n = 40, Ø36.5 ± 11.9). Lavage fluids were analysed by ELISA for levels of aggrecan, BMP-2/7, IGF-1/R, bFGF, CD105, MMP-13, and IL-1β. Additionally, clinical parameters and scores (FFI, CFSS, AOFAS) were evaluated and supplemented by radiographic scores [Kellgren-Lawrence Score (KLS) for conventional X-rays, Ankle Osteoarthritis Scoring System (AOSS) for MRI].

RESULTS

In contrast to distribution of gender and BMI (p < 0.005), parameters characterizing the cartilage defect as ICRS grading, size, and duration of symptoms were not dependent on age. The incidence of osteochondritis dissecans (OCD) was higher in the group <18 years (p < 0.006), but the average degree of OCD grading was not different. KLS and AOSS were significantly higher in the group ≥18 years (p < 0.02). Correlating with the higher degree of OA in the elderly, clinical function measured by FFI and AOFAS was statistically significantly worse (p < 0.05). Intra-articular concentrations of aggrecan (3.1-fold), bFGF (8.7-fold), BMP-7 (2.7-fold), and CD105 (1.5-fold) were statistically significantly higher in the group ≥18 years (p < 0.03).

CONCLUSIONS

Confirming the hypothesis, increased synovial levels of aggrecan, bFGF, BMP-7, and CD105 were found in patients over 18 years. This correlated with a higher stage of OA determined by radiographic changes or deteriorated function and may offer starting points for new diagnostics and interventional strategies.

LEVEL OF EVIDENCE

II.

Reciprocal inhibition between miR-26a and NF-κB regulates obesity-related chronic inflammation in chondrocytes

miR-26a suppresses proinflammatory cytokine production via inactivating NF-κB, whereas NF-κB inhibits miR-26a production through binding to miR-26a promoter. We identified a reciprocal inhibition between miR-26a and NF-κB in obesity-related chondrocytes, providing a potential mechanism linking obesity to osteoarthritis.

Obesity is causally linked to osteoarthritis (OA), with the mechanism being not fully elucidated. miRNAs (miRs) are pivotal regulators of various diseases in multiple tissues, including inflammation in the chondrocytes. In the present study, we for the first time identified the expression of miR-26a in mouse chondrocytes. Decreased level of miR-26a was correlated to increased chronic inflammation in the chondrocytes and circulation in obese mouse model. Mechanistically, we demonstrated that miR-26a attenuated saturated free fatty acid-induced activation of NF-κB (p65) and production of proinflammatory cytokines in chondrocytes. Meanwhile, NF-κB (p65) also suppressed miR-26a production by directly binding to a predicted NF-κB binding element in the promoter region of miR-26a. Finally, we observed a negative correlation between NF-κB and miR-26a in human patients with osteoarthritis. Thus, we identified a reciprocal inhibition between miR-26a and NF-κB downstream of non-esterified fatty acid (NEFA) signalling in obesity-related chondrocytes. Our findings provide a potential mechanism linking obesity to cartilage inflammation.

An inflammatory equine model demonstrates dynamic changes of immune response and cartilage matrix molecule degradation in vitro

The molecular aspects of inflammation were investigated in equine articular cartilage explants using quantitative proteomics. Articular cartilage explants were stimulated with interleukin (IL)-1β in vitro for 25 days, and proteins released into cell culture media were chemically labeled with isobaric mass tags and analyzed by liquid chromatography-tandem mass spectrometry. A total of 127 proteins were identified and quantified in media from explants. IL-1β-stimulation resulted in an abundance of proteins related to inflammation, including matrix metalloproteinases, acute phase proteins, complement components and IL-6. Extracellular matrix (ECM) molecules were released at different time points, and fragmentation of aggrecan and cartilage oligomeric matrix protein was observed at days 3 and 6, similar to early-stage OA in vivo. Degradation products of the collagenous network were observed at days 18 and 22, similar to late-stage OA. This model displays a longitudinal quantification of released molecules from the ECM of articular cartilage. Identification of dynamic changes of extracellular matrix molecules in the secretome of equine explants stimulated with IL-1β over time may be useful for identifying components released at different time points during the spontaneous OA process.

OA phenotypes, rather than disease stage, drive structural progression--identification of structural progressors from 2 phase III randomized clinical studies with symptomatic knee OA

BACKGROUND/PURPOSE

The aim of this study was to identify key characteristics of disease progression through investigation of the association of radiographic progression over two years with baseline Joint Space Width (JSW), Kellgren-Lawrence (KL) grade, Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain, Joint Space Narrowing (JSN), and BMI.

METHODS

Data from 2206 subjects (4390 knees) were combined for this post-hoc analysis of two randomized, double-blind, multi-center, placebo-controlled phase III trials (NCT00486434 and NCT00704847) that evaluated the efficacy and safety of 2-years treatment with oral salmon calcitonin of subjects with painful knee osteoarthritis (OA).

RESULTS

There was a clear positive and significant correlation between KL grade and WOMAC pain and total WOMAC, albeit the variance in pain measures was from min-to-max for all KL categories, emphasizing the heterogeneity of this patient population and pain perception. 32% of target knees did not progress, and only 51% had changes over minimum significant change (MSC). BMI, KL-Score and WOMAC pain was diagnostic, but only KL-score and pain had prognostic value, albeit pain in a non-linear manner.

CONCLUSION

These data clearly describe significant associations between KL grade, JSW, pain and BMI in patients with symptomatic knee OA. KL grade, BMI and WOMAC pain were diagnostically associated with OA based on JSW but only KL-score and pain in a non-linier fashion was prognostic. 50% of patients did not progress more than MSC, highlighting the importance for identification of structural progressors and the phenotypes associated with these. These results suggest that disease phenotypes, rather than disease status, are responsible for disease progression.

Epigenetics and Osteoarthritis

Osteoarthritis (OA) is the most common form of joint disease and the leading cause of chronic disability in middle-aged and older populations. The development of disease-modifying therapy for OA currently faces major obstacles largely because the regulatory mechanisms for the function of joint tissue cells remain unclear. Previous studies have found that the alterations in gene expression of specific transcription factors (TFs), pro- or anti-inflammatory cytokines, matrix proteinases and extracellular matrix (ECM) proteins in articular cartilage may be involved in the development of OA. However, the regulatory mechanisms for the expression of those genes in OA chondrocytes are largely unknown. The recent advances in epigenetic studies have shed lights on the importance of epigenetic regulation of gene expression in the development of OA. In this review, we summarize and discuss the recent studies on the regulatory roles of various epigenetic mechanisms in the expression of genes for specific TFs, cytokines, ECM proteins and matrix proteinases, as well the significance of these epigenetic mechanisms in the pathogenesis of OA.

MiR-193b regulates early chondrogenesis by inhibiting the TGF-beta2 signaling pathway

Cartilage generation and degradation are regulated by miRNAs. Our previous study has shown altered expression of miR-193b in chondrogenic human adipose-derived mesenchymal stem cells (hADSCs). In the current study, we investigated the role of miR-193b in chondrogenesis and cartilage degradation. Luciferase reporter assays showed that miR-193b targeted seed sequences of the TGFB2 and TGFBR3 3'-UTRs. MiR-193b suppressed the expression of early chondrogenic markers in chondrogenic ATDC5 cells, and TNF-alpha expression in IL-1b-induced PMCs. In conclusion, MiR-193b may inhibit early chondrogenesis by targeting TGFB2 and TGFBR3, and may regulate inflammation by repressing TNF-alpha expression in inflamed chondrocytes.

Chronic pain management in the obese patient: a focused review of key challenges and potential exercise solutions

In obese persons, general and specific musculoskeletal pain is common. Emerging evidence suggests that obesity modulates pain via several mechanisms such as mechanical loading, inflammation, and psychological status. Pain in obesity contributes to deterioration of physical ability, health-related quality of life, and functional dependence. We present the accumulating evidence showing the interrelationships of mechanical stress, inflammation, and psychological characteristics on pain. While acute exercise may transiently exacerbate pain symptoms, regular participation in exercise can lower pain severity or prevalence. Aerobic exercise, resistance exercise, or multimodal exercise programs (combination of the two types) can reduce joint pain in young and older obese adults in the range of 14%-71.4% depending on the study design and intervention used. While published attrition rates with regular exercise are high (∼50%), adherence to exercise may be enhanced with modification to exercise including the accumulation of several exercise bouts rather than one long session, reducing joint range of motion, and replacing impact with nonimpact activity. This field would benefit from rigorous comparative efficacy studies of exercise intensity, frequency, and mode on specific and general musculoskeletal pain in young and older obese persons.

Evaluation of the anti-inflammatory, anti-catabolic and pro-anabolic effects of E-caryophyllene, myrcene and limonene in a cell model of osteoarthritis

Osteoarthritis is a progressive joint disease and a major cause of disability for which no curative therapies are yet available. To identify compounds with potential anti-osteoarthritic properties, in this study, we screened one sesquiterpene, E-caryophyllene, and two monoterpenes, myrcene and limonene, hydrocarbon compounds for anti-inflammatory, anti-catabolic and pro-anabolic activities in human chondrocytes. At non-cytotoxic concentrations, myrcene and limonene inhibited IL-1β-induced nitric oxide production (IC50=37.3μg/ml and 85.3µg/ml, respectively), but E-caryophyllene was inactive. Myrcene, and limonene to a lesser extent, also decreased IL-1β-induced NF-κB, JNK and p38 activation and the expression of inflammatory (iNOS) and catabolic (MMP-1 and MMP-13) genes, while increasing the expression of anti-catabolic genes (TIMP-1 and -3 by myrcene and TIMP-1 by limonene). Limonene increased ERK1/2 activation by 30%, while myrcene decreased it by 26%, relative to IL-1β-treated cells. None of the compounds tested was able to increase the expression of cartilage matrix-specific genes (collagen II and aggrecan), but both compounds prevented the increased expression of the non-cartilage specific, collagen I, induced by IL-1β. These data show that myrcene has significant anti-inflammatory and anti-catabolic effects in human chondrocytes and, thus, its ability to halt or, at least, slow down cartilage destruction and osteoarthritis progression warrants further investigation.

Genetic polymorphisms of interleukin-16 are associated with susceptibility to primary knee osteoarthritis

Interleukin-16 (IL-16) polymorphisms have been associated with various disease states, and its activity is dysregulated in synovial fibroblasts of individuals with rheumatoid arthritis. Here, the association between genetic polymorphisms in the gene encoding IL-16 and susceptibility to primary knee osteoarthritis was investigated in the Chinese Han population. The study included 228 unrelated patients, half of whom presented with primary knee osteoarthritis (OA); the remainder was healthy individuals. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to examine single nucleotide polymorphisms (SNPs) in IL16 in these patients. Statistical analysis was performed using the chi-square goodness-of-fit test, Hardy-Weinberg (H-W) equilibrium, linkage disequilibrium analysis, and logistic regression analysis. The genotype distributions of three IL16 SNPs, rs11556218, rs4778889, and rs4072111, were found to be in line with Hardy-Weinberg equilibrium criteria (P > 0.05). The single-factor logistic regression analysis showed that, compared with the T/T genotype, the T/G genotype decreased the risk of primary knee OA in rs11556218 (OR = 0.37, 95% CI = 0.18~0.82) and, compared with the C/C genotype, the C/T genotype increased the risk of primary knee OA in rs4072111 (OR = 1.83, 95% CI = 1.07~3.59). There was linkage disequilibrium between rs4778889 and rs11556218 (D= 0.592, r(2) = 0.213). Finally, logistic regression analysis showed that compared to haplotype TTC, the TTT haplotype was associated with an increased risk of primary knee OA (OR = 2.10, 95% CI = 1.09-4.98); however, the GCC haplotype was associated with a reduced risk of primary knee OA (OR = 0.36, 95% CI = 0.12-0.93). Thus, the genetic polymorphisms rs11556218, rs4778889, and rs4072111 in the gene encoding IL-16 are associated with primary knee OA in Chinese Han population.

A machine learning heuristic to identify biologically relevant and minimal biomarker panels from omics data

BACKGROUND

Investigations into novel biomarkers using omics techniques generate large amounts of data. Due to their size and numbers of attributes, these data are suitable for analysis with machine learning methods. A key component of typical machine learning pipelines for omics data is feature selection, which is used to reduce the raw high-dimensional data into a tractable number of features. Feature selection needs to balance the objective of using as few features as possible, while maintaining high predictive power. This balance is crucial when the goal of data analysis is the identification of highly accurate but small panels of biomarkers with potential clinical utility. In this paper we propose a heuristic for the selection of very small feature subsets, via an iterative feature elimination process that is guided by rule-based machine learning, called RGIFE (Rule-guided Iterative Feature Elimination). We use this heuristic to identify putative biomarkers of osteoarthritis (OA), articular cartilage degradation and synovial inflammation, using both proteomic and transcriptomic datasets.

RESULTS AND DISCUSSION

Our RGIFE heuristic increased the classification accuracies achieved for all datasets when no feature selection is used, and performed well in a comparison with other feature selection methods. Using this method the datasets were reduced to a smaller number of genes or proteins, including those known to be relevant to OA, cartilage degradation and joint inflammation. The results have shown the RGIFE feature reduction method to be suitable for analysing both proteomic and transcriptomics data. Methods that generate large 'omics' datasets are increasingly being used in the area of rheumatology.

CONCLUSIONS

Feature reduction methods are advantageous for the analysis of omics data in the field of rheumatology, as the applications of such techniques are likely to result in improvements in diagnosis, treatment and drug discovery.

TNF-α and TGF-β1 regulate Syndecan-4 expression in nucleus pulposus cells: role of the mitogen-activated protein kinase and NF-κB pathways

Syndecan-4 is emerging as an important player in cell interaction with the extracellular environment and has been shown to be involved in the progression of intervertebral disc degeneration. However, the mechanism of syndecan-4 regulation by TNF-α and the role of TGF-β1 in regulating syndecan-4 expression remain poorly understood in nucleus pulposus (NP) cells. The aim of this study was to investigate these mechanisms. We exposed NP cells to TNF-α and the gene, protein expression, and promoter activity levels of syndecan-4 were measured by qPCR, western blotting, and the luciferase reporter assay, respectively. The activation of the MAPK and NF-κB pathways was detected using western blot analysis. Syndecan-4 expression in rat NP cells was increased by TNF-α, but this was neither time nor dose dependent in response to TNF-α. ERK1/2, JNK, and NF-κB pathways were activated following TNF-α treatment. Treatment with ERK1/2 and NF-κB inhibitors decreased the up-regulation of syndecan-4 by TNF-α. However, JNK inhibition showed no effect on syndecan-4 expression induced by TNF-α. TNF-α mediated up-regulation of syndecan-4 was antagonized by TGF-β1. This study provided evidence for the differential regulation by MAPK and NF-κB pathways in the over-expression of syndecan-4 promoted by TNF-α in NP cells. Our results demonstrate that TGF-β1 exerts anabolic effects on intervertebral discs by inhibiting the expression of syndecan-4.

The dynamics of the pain system is intact in patients with knee osteoarthritis: An exploratory experimental study

Background and aims

Despite the high prevalence of knee osteoarthritis (OA) it remains one of the most frequent knee disorders without a cure. Pain and disability are prominent clinical features of knee OA. Knee OA pain is typically localized but can also be referred to the thigh or lower leg. Widespread hyperalgesia has been found in knee OA patients. In addition, patients with hyperalgesia in the OA knee joint show increased pain summation scores upon repetitive stimulation of the OA knee suggesting the involvement of facilitated central mechanisms in knee OA. The dynamics of the pain system (i.e., the adaptive responses to pain) has been widely studied, but mainly from experiments on healthy subjects, whereas less is known about the dynamics of the pain system in chronic pain patients, where the pain system has been activated for a long time. The aim of this study was to assess the dynamics of the nociceptive system quantitatively in knee osteoarthritis (OA) patients before and after induction of experimental knee pain.

Methods

Ten knee osteoarthritis (OA) patients participated in this randomized crossover trial. Each subject was tested on two days separated by 1 week. The most affected knee was exposed to experimental pain or control, in a randomized sequence, by injection of hypertonic saline into the infrapatellar fat pad and a control injection of isotonic saline. Pain areas were assessed by drawings on anatomical maps. Pressure pain thresholds (PPT) at the knee, thigh, lower leg, and arm were assessed before, during, and after the experimental pain and control conditions. Likewise, temporal summation of pressure pain on the knee, thigh and lower leg muscles was assessed.

Results

Experimental knee pain decreased the PPTs at the knee (P <0.01) and facilitated the temporal summation on the knee and adjacent muscles (P < 0.05). No significant difference was found at the control site (the contralateral arm) (P =0.77). Further, the experimental knee pain revealed overall higher VAS scores (facilitated temporal summation of pain) at the knee (P < 0.003) and adjacent muscles (P < 0.0001) compared with the control condition. The experimental knee pain areas were larger compared with the OA knee pain areas before the injection.

Conclusions

Acute experimental knee pain induced in patients with knee OA caused hyperalgesia and facilitated temporal summation of pain at the knee and surrounding muscles, illustrating that the pain system in individuals with knee OA can be affected even after many years of nociceptive input. This study indicates that the adaptability in the pain system is intact in patients with knee OA, which opens for opportunities to prevent development of centralized pain syndromes.

Osteoarthritis-related biomarkers following anterior cruciate ligament injury and reconstruction: a systematic review

OBJECTIVE

There is an increased risk of developing knee osteoarthritis (OA) following anterior cruciate ligament (ACL) injury. Biomarkers may provide diagnostic, prognostic, or burden of disease indicators of OA before radiographic changes become apparent. Unfortunately, there has been no systematic review to clarify which biomarkers may be most informative following injury. Therefore, this review critically investigated existing studies of OA-related biomarkers in ACL-deficient (ACL-D) and reconstructed (ACL-R) patients to summarize the current evidence and identify knowledge gaps.

DESIGN

A systematic review of the literature in Web of Science and PubMed databases (1960-June 2014) was performed. All English-language case-control and longitudinal studies assessing OA-related biomarkers in ACL-D and ACL-R patients were considered. Data regarding biomarker changes over time within ACL-D and ACL-R patients as well as differences in ACL-D/ACL-R patients compared with a control group were extracted from pertinent studies.

RESULTS

A descriptive summary of 20 included studies was produced. In ACL-D patients compared with controls, synovial fluid biomarkers indicated elevated collagen turnover, while the inflammatory cytokine response was inconclusive. In ACL-R patients, serum concentrations indicated decreased collagen breakdown, but urine concentrations were indicative of greater collagen breakdown when compared to controls. Compared to preoperative values, the overall inflammatory cytokine response measured with synovial fluid biomarkers increased while plasma biomarkers did not change following reconstruction.

CONCLUSION

Patients with ACL-D or ACL-R have altered biomarkers indicative of OA. More research with standardized reporting is needed to effectively determine which biomarkers are the most indicative for OA development and progression following ACL injury.

Effect of two different preparations of platelet-rich plasma on synoviocytes

PURPOSE

To analyse the modifications induced by two different platelet-rich plasma (PRP) preparations on osteoarthritis (OA) synoviocytes, by documenting changes in gene expression of factors involved in joint physiopathology.

METHODS

OA synoviocytes were cultured for 7 days in medium with different concentrations of either P-PRP (a pure platelet concentrate without leucocytes but with a limited number of platelets), L-PRP (a higher platelet concentrate containing leucocytes) or platelet-poor plasma (PPP). Gene expression of interleukin (IL)-1beta, IL-6, IL-8/CXCL8, tumour necrosis factor alpha, IL-10, IL-4, IL-13, metalloproteinase-13, tissue inhibitor of metalloproteinase (TIMP)-1, (TIMP)-3, (TIMP)-4, vascular endothelial growth factor, transforming growth factor beta1, fibroblast growth factor (FGF)-2, hepatocyte growth factor (HGF), hyaluronic acid (HA) synthases (HAS)-1, (HAS)-2, and (HAS)-3 was analysed by RT-PCR. HA production was determined in culture supernatants by ELISA.

RESULTS

IL-1β, IL-8 and FGF-2 were significantly induced by L-PRP compared to both P-PRP and PPP; HGF was down-modulated by L-PRP versus both P-PRP and PPP, and an inverse dose-response influence was shown for all preparations. Expression level of TIMP-4 was lower in the presence of L-PRP compared with P-PRP. HA production and HAS gene expression did not seem to be modulated by PRP.

CONCLUSIONS

L-PRP is able to sustain the up-regulation of proinflammatory factors, (IL-1beta, IL-8 and FGF-2), together with a down-modulation of HGF and TIMP-4 expression, two factors that have been recognized as anti-catabolic mediators in cartilage, thus supporting the need to further optimize the PRP preparations to be applied in clinical practice.

Changes in synovial fluid biomarkers and clinical efficacy of intra-articular injections of hyaluronic acid for patients with knee osteoarthritis

Background

The changes in synovial fluid biomarkers after intra-articular injection of hyarulonic acid (IA HA) remain controversial. We investigate the changes in the properties of synovial fluid (SF) and clinical symptoms before the first and fifth IA HA.

Methods

A total of 73 patients (73 knees) with symptomatic knee osteoarthritis were treated with five weekly intra-articular injections of HA and 55 patients (55 knees) were analyzed. The SF total volume, viscosity, and levels of HA, chondroitin 4-sulfate (C4S), chondroitin 6-sulfate (C6S), keratin sulfate, and interleukin (IL)-6 were measured before the first and fifth injections. Clinical evaluations were performed using the American Knee Society score for physician-based outcome measurements and Knee injury and Osteoarthritis Outcome Score for patient-based outcome measurements before the first and fifth injections.

Results

The SF viscosity and levels of HA were significantly increased, and the total SF volume and levels of chondroitin 4-sulfate, chondroitin 6-sulfate, and interleukin-6 were significantly decreased. The physician-based and patient-based outcome scores were improved.

Conclusions

Our findings speculate that HA injections significantly modulate levels of intra articular biomarkers which may indicate beneficial effect for articular cartilage and synovium membrane.

Chondroprotective potential of Phyllanthus amarus Schum. & Thonn. in experimentally induced cartilage degradation in the explants culture model

Phyllanthus amarus Schum. & Thonn. (P. amarus) has been reported to exhibit anti-inflammation and antiarthritis properties leading to our interest to examine its beneficial effect in osteoarthritis. Thus, this study aimed to explore the chondroprotective potential of P. amarus extract (PAE) and its major compounds, phyllanthin and hypophyllanthin, in a cartilage explant model. Various concentrations of P. amarus extract, phyllanthin and hypophyllanthin, were treated on porcine articular cartilage explants induced with 25 ng/ml of interleukin-1 beta (IL-1β). After 4 days of incubation, the culture medium was measured for the release of sulfate glycosaminoglycans (s-GAGs) and matrix metalloproteinase-2 (MMP-2) activity by DMMB binding assay and zymography, respectively. The explant tissues were analyzed for the remaining of uronic acid content by colorimetric assay and stained with safranin-O for investigation of proteoglycan content. Cell viability of this model was evaluated by lactate dehydrogenase (LDH) assay. Chondroprotective potential of PAE and the major components against IL-1β-induced cartilage explant degradation were revealed by the decreased s-GAGs level and MMP-2 activity in culture medium consistent with an increase in uronic acid and proteoglycan contents in the explants when compared to the IL-1β treatment. These results agreed with those of diacerein and sesamin which used as positive controls. In addition, better chondroprotective activities of P. amarus crude extracts than those of the purified components were disclosed in this study. Hence, this is a pioneering study presenting the chondroprotective potential of PAE which may augment its application for therapeutic use as an antiarthritic agent.

Monotropein exerts protective effects against IL-1β-induced apoptosis and catabolic responses on osteoarthritis chondrocytes

Osteoarthritis, characterized by a loss of articular cartilage accompanied with inflammation, is the most common age-associated degenerative disease. Monotropein, an iridoids glycoside isolated from the roots of Morinda officinalis How, has been demonstrated to exhibit anti-inflammatory activity. In the present study, monotropein was firstly to exhibit cartilage protective activity by down regulating the pro-inflammatory cytokines in the knee synovial fluid in vivo. The anti-apoptotic and anti-catabolic effects of monotropein on rat OA chondrocytes treated by IL-1β were investigated in vitro. In cultured chondrocytes, monotropein attenuated apoptosis in a dose-dependent manner in response to IL-1β stimulation. Moreover, treatment with monotropein, the expressions of MMP-3 and MMP-13 were significantly decreased, the expression of COL2A1 was increased. Taken together, these findings suggested that monotropein exerted anti-apoptosis and anti-catabolic activity in chondrocytes, which might support its possible therapeutic role in OA.

Possible chondroprotective effect of canakinumab: an in vitro study on human osteoarthritic chondrocytes

Canakinumab is a human IgGκ monoclonal antibody that neutralizes the activity of interleukin (IL)-1β blocking interaction with IL-1β receptors. Our study aimed to evaluate the in vitro effect of canakinumab on human osteoarthritic (OA) chondrocytes cultivated in the presence or absence of tumor necrosis factor (TNF)-α. Articular cartilage was obtained from the femoral heads of patients with osteoarthritis (OA). Chondrocytes were incubated with two concentrations (1μg/ml and 10μg/ml) of canakinumab alone or with TNF-α (10ng/ml) for 48h. We evaluated cell viability, release of proteoglycans (PG) and nitric oxide (NO) in culture medium, inducible nitric oxide synthase (iNOS) and metalloproteinanes (MMP)-1,3,13 gene expression, apoptosis, necrosis and morphological feature by transmission electron microscopy (TEM). Canakinumab alone did not have cytotoxic effect. Cell viability was reduced significantly (p<0.001) by TNF-α and restored by canakinumab at both concentrations used. TNF-α determined a significant decrease of PG (p<0.001) and an increase of NO (p<0.001) and MMP-1,3,13 gene expression. Canakinumab significantly increased the PG levels and decreased (1μg/ml, p<0.01; 10μg/ml, p<0.01) NO levels in cells cultured with TNF-α. The NO data were confirmed by the immunocytochemistry assay for iNOS. A significant reduction of MMP-1,3,13 gene expression was induced by canakinumab. Our experiments confirmed the pro-apoptotic effect of TNF-α and demonstrated a protective role of canakinumab. The results concerning biochemical data were further confirmed by the morphological findings obtained by TEM. We showed that canakinumab counteracts the negative effects of TNF-α on OA chondrocyte cultures and may have a potential chondroprotective role in OA.

Mesenchymal stem cell therapies in the treatment of musculoskeletal diseases

The application of regenerative strategies to musculoskeletal ailments offers extraordinary promise to transform management of the conditions of numerous patients. The use of cell-based therapies and adjunct strategies is under active investigation for injuries and illnesses affecting bones, joints, tendons, and skeletal muscle. Of particular interest to the field is the mesenchymal stem cell, an adult stem cell found in bone marrow and adipose tissue. This cell type can be expanded ex vivo, has allogeneic application, and has the capacity for engraftment and differentiation into mesodermal lineages. Also of major interest in the field is the use of platelet-rich plasma, a strategy to concentrate endogenous cytokines and growth factors with reparative potential. Here we review the biological basis, clinical studies, safety, and current state of mesenchymal stem cell and platelet-rich plasma therapies in the treatment of musculoskeletal disease.

Intra-articular delivery of kartogenin-conjugated chitosan nano/microparticles for cartilage regeneration

We developed an intra-articular (IA) drug delivery system to treat osteoarthritis (OA) that consisted of kartogenin conjugated chitosan (CHI-KGN). Kartogenin, which promotes the selective differentiation of mesenchymal stem cells (MSCs) into chondrocytes, was conjugated with low-molecular-weight chitosan (LMWCS) and medium-molecular-weight chitosan (MMWCS) by covalent coupling of kartogenin to each chitosan using an ethyl(dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) catalyst. Nanoparticles (NPs, 150 ± 39 nm) or microparticles (MPs, 1.8 ± 0.54 μm) were fabricated from kartogenin conjugated-LMWCS and -MMWCS, respectively, by an ionic gelation using tripolyphosphate (TPP). The in vitro release profiles of kartogenin from the particles showed sustained release for 7 weeks. When the effects of the CHI-KGN NPs or CHI-KGN MPs were evaluated on the in vitro chondrogenic differentiation of human bone marrow MSCs (hBMMSCs), the CHI-KGN NPs and CHI-KGN MPs induced higher expression of chondrogenic markers from cultured hBMMSCs than unconjugated kartogenin. In particular, hBMMSCs treated with CHI-KGN NPs exhibited more distinct chondrogenic properties in the long-term pellet cultures than those treated with CHI-KGN MPs. The in vivo therapeutic effects of CHI-KGN NPs or CHI-KGN MPs were investigated using a surgically-induced OA model in rats. The CHI-KGN MPs showed longer retention time in the knee joint than the CHI-KGN NPs after IA injection in OA rats. The rats treated with CHI-KGN NPs or CHI-KGN MPs by IA injection showed much less degenerative changes than untreated control or rats treated with unconjugated kartogenin. In conclusion, CHI-KGN NPs or CHI-KGN MPs can be useful polymer-drug conjugates as an IA drug delivery system to treat OA.

Metabolic enrichment of omega-3 polyunsaturated fatty acids does not reduce the onset of idiopathic knee osteoarthritis in mice

OBJECTIVE

We evaluated the effect of a reduction in the systemic ratio of n-6:n-3 polyunsaturated fatty acids (PUFAs) on changes in inflammation, glucose metabolism, and the idiopathic development of knee osteoarthritis (OA) in mice. We hypothesized that a lower ratio of n-6:n-3 PUFAs would protect against OA markers in cartilage and synovium, but not bone.

DESIGN

Male and female fat-1 transgenic mice (Fat-1), which convert dietary n-6 to n-3 PUFAs endogenously, and their wild-type (WT) littermates were fed an n-6 PUFA enriched diet for 9-14 months. The effect of gender and genotype on serum PUFAs, interleukin (IL)-6, tumor necrosis factor (TNF)-α, and glucose tolerance was tested by 2-factor analysis of variance (ANOVA). Cortical and trabecular subchondral bone changes were documented by micro-focal computed tomography (CT), and knee OA was assessed by semi-quantitative histomorphometry grading.

RESULTS

The n-6:n-3 ratio was reduced 12-fold and 7-fold in male and female Fat-1 mice, respectively, compared to WT littermates. IL-6 and TNF-α levels were reduced modestly in Fat-1 mice. However, these systemic changes did not reduce osteophyte development, synovial hyperplasia, or cartilage degeneration. Also the fat-1 transgene did not alter subchondral cortical or trabecular bone morphology or bone mineral density.

CONCLUSIONS

Reducing the systemic n-6:n-3 ratio does not slow idiopathic changes in cartilage, synovium, or bone associated with early-stage knee OA in mice. The anti-inflammatory and anti-catabolic effects of n-3 PUFAs previously reported for cartilage may be more evident at later stages of disease or in post-traumatic and other inflammatory models of OA.

Synergistic anabolic actions of hyaluronic acid and platelet-rich plasma on cartilage regeneration in osteoarthritis therapy

Osteoarthritis (OA) is a common disease associated with tissue inflammation, physical disability and imbalanced homeostasis in cartilage. For advanced treatments, biological approaches are currently focused on tissue regeneration and anti-inflammation. This study was undertaken to evaluate the therapeutic efficacies of hyaluronic acid (HA) and platelet-rich plasma (PRP) (HA+PRP) on OA. Articular chondrocytes were obtained from five OA patients. The optimal HA and PRP concentrations were evaluated by MTT assay. The expressions of chondrogenic and inflammatory genes were analyzed by RT-PCR. Signaling pathway was examined by immunoblotting and the expressions of OA pathology-related chemokines and cytokines was demonstrated by real-time PCR-based SuperArray. The therapeutic efficacies of HA+PRP were then demonstrated in 3D arthritic neo-cartilage and ACLT-OA model. Here we showed that HA+PRP could greatly retrieve pro-inflammatory cytokines-reduced articular chondrocytes proliferation and chondrogenic phenotypes, the mechanism of which involve the sequential activation of specific receptors CD44 and TGF-βRII, downstream mediators Smad2/3 and Erk1/2, and the chondrogenic transcription factor SOX9. The real-time PCR-based SuperArray results also indicated that OA pathology-related chemokines and cytokines could be efficiently suppressed by HA+PRP. Moreover, the cartilaginous ECM could be retrieved from inflammation-induced degradation by HA+PRP in both 2D monolayer and 3D neo-cartilage model. Finally, the intra-articular injection of HA+PRP could strongly rescue the meniscus tear and cartilage breakdown and then decrease OA-related immune cells. The combination of HA+PRP can synergistically promote cartilage regeneration and inhibit OA inflammation. This study might offer an advanced and alternative OA treatment based on detailed regenerative mechanisms.

Lithium protects against cartilage degradation in osteoarthritis

OBJECTIVE

To determine the actions of lithium chloride (LiCl) on catabolic events in human articular chondrocytes, and the effects of LiCl on the progression and severity of cartilage degradation in interleukin-1β (IL-1β)-treated mouse knee joints and after surgical induction of osteoarthritis (OA) in a mouse model.

METHODS

Human articular chondrocytes were treated with LiCl followed by IL-1β, and the expression levels of catabolic genes were determined by real-time polymerase chain reaction. To understand the mechanism by which LiCl affects catabolic events in articular chondrocytes after IL-1β treatment, the activation of NF-κB was determined using luciferase reporter assays, and the activities of MAPKs and the STAT-3 signaling pathway were determined by immunoblot analysis of total cell lysates. Cultures of mouse femoral head explants treated with IL-1β and a mouse model of surgically induced OA were used to determine the effects of LiCl on proteoglycan loss and cartilage degradation.

RESULTS

LiCl treatment resulted in decreased catabolic marker messenger RNA levels and activation of NF-κB, p38 MAPK, and STAT-3 signaling in IL-1β-treated articular chondrocytes. Furthermore, LiCl directly inhibited IL-6-stimulated activation of STAT-3 signaling. Consequently, the loss of proteoglycan and severity of cartilage destruction in LiCl-treated mouse knee joints 8 weeks after OA induction surgery or in LiCl-treated mouse femoral head explants after IL-1β treatment were markedly reduced compared to that in vehicle-treated joints or explants.

CONCLUSION

LiCl reduced catabolic events in IL-1β-treated human articular chondrocytes and attenuated the severity of cartilage destruction in IL-1β-treated mouse femoral head explants and in the knee joints of mice with surgically induced OA, acting via inhibition of the activities of the NF-κB, p38, and STAT-3 signaling pathways.

Expression of receptors of advanced glycation end product (RAGE) and types I, III and IV collagen in the vastus lateralis muscle of men in early stages of knee osteoarthritis

Alterations in the contractile and non-contractile proteins of the skeletal muscle may reduce muscle function in knee osteoarthritis (OA), and the formation and accumulation of advanced glycation end products, particularly in collagen, can influence the quality of these muscle proteins. The objective of this study was to evaluate the reactivity of types I, III and IV collagen and the expression and localization of receptor for advanced glycation end products (RAGE) in the vastus lateralis (VL) muscle in early stages of knee OA. The hypothesis was that these patients present a higher expression of RAGE and increased immunoreactivity in the collagen. Thirty-five men were divided into two groups: the control group (CG; n = 17) and the osteoarthritis group (OAG; n = 18). All participants were submitted to a biopsy of the VL. The muscle samples were analyzed by immunohistochemistry for collagen and for RAGE and laminin. The expression of RAGE was counted (intracellular, extracellular and total). Student's t-test for independent samples and Mann-Whitney U test were used for the RAGE's intergroup analysis (α ≤ 0.05). A semiquantitative analysis was performed to assess the collagen reactivity. No significant differences were observed in the intracellular, extracellular or total localization of RAGE (p > 0.05). Higher immunoreactivity was observed in the OAG for all types of collagen, with more reactivity for collagen III and IV. We concluded that in the initial stages of knee OA, no differences were observed for RAGE levels between the groups. However, the OAG's higher collagen expression may represent adaptations for reducing muscle stiffness and avoiding injury.

Update on biological therapies for knee injuries: osteoarthritis

Osteoarthritis (OA) is a progressive disease that causes functional impairment of the joints. Chronic forms of knee OA have been increasing worldwide, limiting patients' quality of life. Recent studies have sought to increase effectiveness and quality in the development of new therapies, such as platelet-rich plasma, hyaluronic acid, stem cells, and nuclear factor κB, aimed principally at reducing proinflammatory activity, pain, and degeneration of the knee joints. The goal of this review is to present an update on biological therapies for knee OA and to provide guidance for future OA studies.

Exosomes from IL-1β stimulated synovial fibroblasts induce osteoarthritic changes in articular chondrocytes

Introduction

Osteoarthritis (OA) is a whole joint disease, and characterized by progressive degradation of articular cartilage, synovial hyperplasia, bone remodeling and angiogenesis in various joint tissues. Exosomes are a type of microvesicles (MVs) that may play a role in tissue-tissue and cell-cell communication in homeostasis and diseases. We hypothesized that exosomes function in a novel regulatory network that contributes to OA pathogenesis and examined the function of exosomes in communication among joint tissue cells.

Methods

Human synovial fibroblasts (SFB) and articular chondrocytes were obtained from normal knee joints. Exosomes isolated from conditioned medium of SFB were analyzed for size, numbers, markers and function. Normal articular chondrocytes were treated with exosomes from SFB, and Interleukin-1β (IL-1β) stimulated SFB. OA-related genes expression was quantified using real-time PCR. To analyze exosome effects on cartilage tissue, we performed glycosaminoglycan release assay. Angiogenic activity of these exosomes was tested in migration and tube formation assays. Cytokines and miRNAs in exosomes were analyzed by Bio-Plex multiplex assay and NanoString analysis.

Results

Exosomes from IL-1β stimulated SFB significantly up-regulated MMP-13 and ADAMTS-5 expression in articular chondrocytes, and down-regulated COL2A1 and ACAN compared with SFB derived exosomes. Migration and tube formation activity were significantly higher in human umbilical vein endothelial cells (HUVECs) treated with the exosomes from IL-1β stimulated SFB, which also induced significantly more proteoglycan release from cartilage explants. Inflammatory cytokines, IL-6, MMP-3 and VEGF in exosomes were only detectable at low level. IL-1β, TNFα MMP-9 and MMP-13 were not detectable in exosomes. NanoString analysis showed that levels of 50 miRNAs were differentially expressed in exosomes from IL-1β stimulated SFB compared to non-stimulated SFB.

Conclusions

Exosomes from IL-1β stimulated SFB induce OA-like changes both in vitro and in ex vivo models. Exosomes represent a novel mechanism by which pathogenic signals are communicated among different cell types in OA-affected joints.

Interleukin-1 beta and tumor necrosis factor alpha inhibit migration activity of chondrogenic progenitor cells from non-fibrillated osteoarthritic cartilage

Introduction

The repair capability of traumatized articular cartilage is highly limited so that joint injuries often lead to osteoarthritis. Migratory chondrogenic progenitor cells (CPC) might represent a target cell population for in situ regeneration. This study aims to clarify, whether 1) CPC are present in regions of macroscopically intact cartilage from human osteoarthritic joints, 2) CPC migration is stimulated by single growth factors and the cocktail of factors released from traumatized cartilage and 3) CPC migration is influenced by cytokines present in traumatized joints.

Methods

We characterized the cells growing out from macroscopically intact human osteoarthritic cartilage using a panel of positive and negative surface markers and analyzed their differentiation capacity. The migratory response to platelet-derived growth factor (PDGF)-BB, insulin-like growth factor 1 (IGF-1), supernatants obtained from in vitro traumatized cartilage and interleukin-1 beta (IL-1β) as well as tumor necrosis factor alpha (TNF-α) were tested with a modified Boyden chamber assay. The influence of IL-1β and TNF-α was additionally examined by scratch assays and outgrowth experiments.

Results

A comparison of 25 quadruplicate marker combinations in CPC and bone-marrow derived mesenchymal stromal cells showed a similar expression profile. CPC cultures had the potential for adipogenic, osteogenic and chondrogenic differentiation. PDGF-BB and IGF-1, such as the supernatant from traumatized cartilage, induced a significant site-directed migratory response. IL-1β and TNF-α significantly reduced basal cell migration and abrogated the stimulative effect of the growth factors and the trauma supernatant. Both cytokines also inhibited cell migration in the scratch assay and primary outgrowth of CPC from cartilage tissue. In contrast, the cytokine IL-6, which is present in trauma supernatant, did not affect growth factor induced migration of CPC.

Conclusion

These results indicate that traumatized cartilage releases chemoattractive factors for CPC but IL-1β and TNF-α inhibit their migratory activity which might contribute to the low regenerative potential of cartilage in vivo.

Influence of model and matrix on cytokine profile in rat and human

OBJECTIVE

Emerging evidence indicates that low-grade inflammation is part of the clinical picture of OA and that there is a need to identify soluble biomarkers of ongoing inflammation in the joint from a translational aspect. The aim of this study was to compare levels of pro-inflammatory biomarkers in SF, serum and/or EDTA plasma.

METHODS

SF and blood from rats subjected to Freund's complete adjuvant (FCA; n = 48) or monoiodoacetate (MIA; n = 88) monoarthritis and from control rats were collected over time. SF, EDTA plasma and serum were obtained from six individuals with OA of the knee and healthy controls. Levels of IL-6, KC/GRO, IL-8, monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 3α (MIP-3α), IL-1β, TNF and l(+)-lactate were assessed either by immune assay or by a colorimetric method.

RESULTS

Elevated levels of biomarkers were shown in monoarthritic animals in SF compared with the control groups, although with considerably lower magnitude in the MIA groups, which also indicated a biphasic pattern. Levels of KC/GRO and MIP-3α in serum from the FCA model and IL-6 in the MIA model followed the pattern of SF. In serum samples from OA individuals, MIP-3α correlated significantly with levels in SF.

CONCLUSION

While we found increased levels of markers in joint fluid and blood, no single systemic biochemical biomarkers that were a common denominator between the animal models and the patient material could be identified. Our data indicate that it is critical to delineate the temporal profile of multiple local and systemic factors in order to pinpoint soluble biomarkers for OA.

Human endogenous retrovirus W activity in cartilage of osteoarthritis patients

The etiology of viruses in osteoarthritis remains controversial because the prevalence of viral nucleic acid sequences in peripheral blood or synovial fluid from osteoarthritis patients and that in healthy control subjects are similar. Until now the presence of virus has not been analyzed in cartilage. We screened cartilage and chondrocytes from advanced and non-/early osteoarthritis patients for parvovirus B19, herpes simplex virus-1, Epstein Barr virus, cytomegalovirus, human herpes virus-6, hepatitis C virus, and human endogenous retroviruses transcripts. Endogenous retroviruses transcripts, but none of the other viruses, were detected in 15 out the 17 patients. Sequencing identified the virus as HERV-WE1 and E2. HERV-W activity was confirmed by high expression levels of syncytin, dsRNA, virus budding, and the presence of virus-like particles in all advanced osteoarthritis cartilages examined. Low levels of HERV-WE1, but not E2 envelope RNA, were observed in 3 out of 8 non-/early osteoarthritis patients, while only 3 out of 7 chondrocytes cultures displayed low levels of syncytin, and just one was positive for virus-like particles. This study demonstrates for the first time activation of HERV-W in cartilage of osteoarthritis patients; however, a causative role for HERV-W in development or deterioration of the disease remains to be proven.

Intraarticular injections (corticosteroid, hyaluronic acid, platelet rich plasma) for the knee osteoarthritis

Osteoarthritis (OA) is a complex “whole joint” disease pursued by inflammatory mediators, rather than purely a process of “wear and tear”. Besides cartilage degradation, synovitis, subchondral bone remodeling, degeneration of ligaments and menisci, and hypertrophy of the joint capsule take parts in the pathogenesis. Pain is the hallmark symptom of OA, but the extent to which structural pathology in OA contributes to the pain experience is still not well known. For the knee OA, intraarticular (IA) injection (corticosteroids, viscosupplements, blood-derived products) is preferred as the last nonoperative modality, if the other conservative treatment modalities are ineffective. IA corticosteroid injections provide short term reduction in OA pain and can be considered as an adjunct to core treatment for the relief of moderate to severe pain in people with OA. IA hyaluronic acid (HA) injections might have efficacy and might provide pain reduction in mild OA of knee up to 24 wk. But for HA injections, the cost-effectiveness is an important concern that patients must be informed about the efficacy of these preparations. Although more high-quality evidence is needed, recent studies indicate that IA platelet rich plasma injections are promising for relieving pain, improving knee function and quality of life, especially in younger patients, and in mild OA cases. The current literature and our experience indicate that IA injections are safe and have positive effects for patient satisfaction. But, there is no data that any of the IA injections will cause osteophytes to regress or cartilage and meniscus to regenerate in patients with substantial and irreversible bone and cartilage damage.

S-adenosylmethionine mediates inhibition of inflammatory response and changes in DNA methylation in human macrophages

S-adenosylmethionine (SAM), the unique methyl donor in DNA methylation, has been shown to lower lipopolysaccharide (LPS)-induced expression of the proinflammatory cytokine TNF-α and increase the expression of the anti-inflammatory cytokine IL-10 in macrophages. The aim of this study was to assess whether epigenetic mechanisms mediate the anti-inflammatory effects of SAM. Human monocytic THP1 cells were differentiated into macrophages and treated with 0, 500, or 1,000 μmol/l SAM for 24 h, followed by stimulation with LPS. TNFα and IL-10 expression levels were measured by real-time PCR, cellular concentrations of SAM and S-adenosylhomocysteine (SAH), a metabolite of SAM, were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and DNA methylation was measured with LC-MS/MS and microarrays. Relative to control (0 μmol/l SAM), treatment with 500 μmol/l SAM caused a significant decrease in TNF-α expression (-45%, P < 0.05) and increase in IL-10 expression (+77%, P < 0.05). Treatment with 1,000 μmol/l SAM yielded no significant additional benefits. Relative to control, 500 μmol/l SAM increased cellular SAM concentrations twofold without changes in SAH, and 1,000 μmol/l SAM increased cellular SAM sixfold and SAH fourfold. Global DNA methylation increased 7% with 500 μmol/l SAM compared with control. Following treatment with 500 μmol/l SAM, DNA methylation microarray analysis identified 765 differentially methylated regions associated with 918 genes. Pathway analysis of these genes identified a biological network associated with cardiovascular disease, including a subset of genes that were differentially hypomethylated and whose expression levels were altered by SAM. Our data indicate that SAM modulates the expression of inflammatory genes in association with changes in specific gene promoter DNA methylation.

Does intraarticular inflammation predict biomechanical cartilage properties?

BACKGROUND

Intact cartilage in the lateral compartment is an important requirement for medial unicompartmental knee arthroplasty (UKA). Progression of cartilage degeneration in the lateral compartment is a common failure mode of medial UKA. Little is known about factors that influence the mechanical properties of lateral compartment cartilage.

QUESTIONS/PURPOSES

The purposes of this study were to answer the following questions: (1) Does the synovial fluid white blood cell count predict the biomechanical properties of macroscopically intact cartilage of the distal lateral femur? (2) Is there a correlation between MRI grading of synovitis and the biomechanical properties of macroscopically intact cartilage? (3) Is there a correlation between the histopathologic assessment of the synovium and the biomechanical properties of macroscopically intact cartilage?

METHODS

The study included 84 patients (100 knees) undergoing primary TKA for varus osteoarthritis between May 2010 and January 2012. All patients underwent preoperative MRI to assess the degree of synovitis. During surgery, the cartilage of the distal lateral femur was assessed macroscopically using the Outerbridge grading scale. In knees with an Outerbridge grade of 0 or 1, osteochondral plugs were harvested from the distal lateral femur for biomechanical and histologic assessment. The synovial fluid was collected to determine the white blood cell count. Synovial tissue was taken for histologic evaluation of the degree of synovitis.

RESULTS

The mean aggregate modulus and the mean dynamic modulus were significantly greater in knees with 150 or less white blood cells/mL synovial fluid compared with knees with greater than 150 white blood cells/mL synovial fluid. There was no correlation among MRI synovitis grades, histopathologic synovitis grades, and biomechanical cartilage properties.

CONCLUSIONS

The study suggests that lateral compartment cartilage in patients with elevated synovial fluid white blood cell counts has a reduced ability to withstand compressive loads.

LEVEL OF EVIDENCE

Level III, diagnostic study. See the Instructions for Authors for a complete description of levels of evidence.

Effect of hydrogen sulfide sources on inflammation and catabolic markers on interleukin 1β-stimulated human articular chondrocytes

OBJECTIVE

Hydrogen sulfide (H2S), the third gasotransmitter together with NO and CO, is emerging as a regulator of inflammation. To test if it might offer therapeutic value in the treatment of osteoarthritis (OA) we evaluated the effects of two exogenous sources of H2S, NaSH and GYY4137, on inflammation and catabolic markers that characterize OA.

METHOD

Human chondrocytes (CHs) were isolated from OA tissue. Cells were stimulated with a pro-inflammatory cytokine (interleukin-1β, IL1β, 5 ng/ml) and the ability of the two H2S sources to ameliorate its effects on the cells was tested. Nitric oxide (NO) production was quantified through the Griess reaction. Protein levels of inducible NO synthase (NOS2) and matrix metalloproteinase 13 (MMP13) were visualized through immunocytochemistry (ICC). Relative mRNA expression was quantified with qRT-PCR. Prostaglandin-2 (PGE-2), interleukin 6 (IL6) and MMP13 levels were measured with specific EIAs. NFκB nuclear translocation was visualized with immunofluorescence.

RESULTS

Both H2S sources led to significant reductions in NO, PGE-2, IL6 and MMP13 released by the cells and at the protein level. This was achieved by downregulation of relevant genes involved in the synthesis routes of these molecules, namely NOS2, cyclooxigenase-2 (COX2), prostaglandin E synthase (PTGES), IL6 and MMP13. NFκB nuclear translocation was also reduced.

CONCLUSION

NaSH and GYY4137 show anti-inflammatory and anti-catabolic properties when added to IL1β activated osteoarthritic CHs. Supplementation with exogenous H2S sources can regulate the expression of relevant genes in OA pathogenesis and progression, counteracting IL1β pro-inflammatory signals that lead to cartilage destruction in part by reducing NFκB activation.