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

Neuroimmune expression in hip osteoarthritis: a systematic review

BACKGROUND

Neuroimmune axis is central in the physiopathology of hip osteoarthritis (OA), but its specific pathways are still unclear. This systematic review aims to assess the nervous and immune system profile of patients with hip osteoarthritis (OA) when compared to healthy controls.

METHODS

A systematic review followed PRISMA guidelines was conducted. A two-step selection process was completed, and from 609 references 17 were included. The inclusion criteria were: original articles on adult patients with hip OA, with assessment of neuroimmune expression. Articles with other interventions prior to analysis and those without a control group were excluded.

RESULTS

Thirty-nine relevant neuroimmune markers were identified, with assessments in bone, cartilage, synovial membrane, synovial fluid, whole blood, serum and/or immune cells. GM-CSF, IFN-γ, IL-1α, IL-6, IL-8, IL-1 and TNF-α presented variable expression among tissues studied when compared between hip OA and controls. VEGFs and TGF-ß isoforms showed similar tendencies among tissues and studies. On nervous expression, CGRP, Tuj-1 and SP were increased in synovial membrane. Overall, patients with hip OA presented a higher number of overexpressed markers.

CONCLUSIONS

For the first time a systematic review on neuroimmune expression in patients with hip OA found an upregulation of neuroimmune markers, with deregulated balance between pro and anti-inflammatory cytokines. However, no clear systematic pattern was found, and few information is available on nervous expression. This highlights the importance of future research with clear methodologies to guide the management of these patients.

Relationship between Sleep, Pain and Inflammatory Markers in Patients with Rheumatoid Arthritis

Introduction: Rheumatoid Arthritis (RA) is known as a progressive chronic auto-immune disease. Measurement of inflammatory markers are applied for follow up the activity of disease. So determining factors that effects these markers such as sleep and pain can help to prevent the severity of disease. The aim of study was to determine the relationship between sleep disorders, pain and inflammatory markers in patients with RA.

Methods: Participants included 210 patients with RA referred to educational medical clinics of Imam Reza and Sina in Tabriz selected by convenience sampling. They were assessed by Sleep Disorders Questionnaire (SDQ) and Epworth Sleepiness Scale (ESS). Visual Analog Scale (VAS) also applied for pain measurement. Data were analyzed using SPSS ver.13 by descriptive and inferential statistics.

Results: Most of participants (74%) were female, the mean age of participants was 48.41 years. The mean (SD) of sleepiness was 13.14 (5.6) and pain 6.09 (2.14). Significant relationship obtained between sleep disorders and pain. As well as sleep problems had significant relation with CRP. Also pain had significant correlation with inflammatory markers.

Conclusion: Sleep pattern in RA appears to be disrupted by pain. Pain severity and sleep problems can predict increasing inflammatory markers that can be a clues of intensity of disease. So relieving pain and improved sleep can decrease the intensity of disease.

Reduced primary cilia length and altered Arl13b expression are associated with deregulated chondrocyte Hedgehog signaling in alkaptonuria

Alkaptonuria (AKU) is a rare inherited disease resulting from a deficiency of the enzyme homogentisate 1,2-dioxygenase which leads to the accumulation of homogentisic acid (HGA). AKU is characterized by severe cartilage degeneration, similar to that observed in osteoarthritis. Previous studies suggest that AKU is associated with alterations in cytoskeletal organization which could modulate primary cilia structure/function. This study investigated whether AKU is associated with changes in chondrocyte primary cilia and associated Hedgehog signaling which mediates cartilage degradation in osteoarthritis. Human articular chondrocytes were obtained from healthy and AKU donors. Additionally, healthy chondrocytes were treated with HGA to replicate AKU pathology (+HGA). Diseased cells exhibited shorter cilia with length reductions of 36% and 16% in AKU and +HGA chondrocytes respectively, when compared to healthy controls. Both AKU and +HGA chondrocytes demonstrated disruption of the usual cilia length regulation by actin contractility. Furthermore, the proportion of cilia with axoneme breaks and bulbous tips was increased in AKU chondrocytes consistent with defective regulation of ciliary trafficking. Distribution of the Hedgehog-related protein Arl13b along the ciliary axoneme was altered such that its localization was increased at the distal tip in AKU and +HGA chondrocytes. These changes in cilia structure/trafficking in AKU and +HGA chondrocytes were associated with a complete inability to activate Hedgehog signaling in response to exogenous ligand. Thus, we suggest that altered responsiveness to Hedgehog, as a consequence of cilia dysfunction, may be a contributing factor in the development of arthropathy highlighting the cilium as a novel target in AKU.

Low-Density Lipoprotein Receptor-Related Proteins in Skeletal Development and Disease

The identification of the low-density lipoprotein receptor (LDLR) provided a foundation for subsequent studies in lipoprotein metabolism, receptor-mediated endocytosis, and many other fundamental biological functions. The importance of the LDLR led to numerous studies that identified homologous molecules and ultimately resulted in the description of the LDL-receptor superfamily, a group of proteins that contain domains also found in the LDLR. Subsequent studies have revealed that members of the LDLR-related protein family play roles in regulating many aspects of signal transduction. This review is focused on the roles of selected members of this protein family in skeletal development and disease. We present background on the identification of this subgroup of receptors, discuss the phenotypes associated with alterations in their function in human patients and mouse models, and describe the current efforts to therapeutically target these proteins to treat human skeletal disease.

Wnt/β-catenin and Hedgehog pathways are involved in the inflammatory effect of Interleukin 18 on rat chondrocytes

To investigate the inflammatory effect of Interleukin 18 (IL-18) on rat chondrocytes and the involvement of Wnt/β-catenin and Hedgehog pathways, the mRNA and protein level of matix-degrading enzymes (MMP-2, 3, 9,13 and aggrecanses) and chondrocyte-specific proteins (Collagen II and aggrecan) were evaluated by qRT-PCR and Western blot, and key protein level of Wnt/β-catenin and Hedgehog pathways including β-catenin, GSK-3β, DKK-1, IHH, SHH, and Gli-2 were evaluated by Western blot. Dickkopf-1 (DKK-1) and Cyclopamine were used as antagonist of Wnt/β-catenin and Hedgehog pathways to perform pathway inhibition tests. In addition, location and expression of β-catenin, GSK-3β, Gli-2 and Smo were assessed by Immunofluorescence microscopy. The results showed up-regulation of matix-degrading enzymes (MMP-2, 3, 9,13 and aggrecanses) and down-regulation of chondrocyte-specific proteins (Collagen II and aggrecan) at both mRNA and protein level and activation of Wnt/β-catenin and Hedgehog pathways in the inflammatory reaction on rat chondrocytes caused by IL-18 treatment was observed. As conclusion, Wnt/β-catenin and Hedgehog pathways are involved in the inflammatory effect of IL-18 in vitro.

Subcellular domain-dependent molecular hierarchy of SFK and FAK in mechanotransduction and cytokine signaling

Focal adhesion kinase (FAK) and Src family kinases (SFK) are known to play critical roles in mechanotransduction and other crucial cell functions. Recent reports indicate that they reside in different microdomains of the plasma membrane. However, little is known about their subcellular domain-dependent roles and responses to extracellular stimuli. Here, we employed fluorescence resonance energy transfer (FRET)-based biosensors in conjunction with collagen-coupled agarose gels to detect subcellular activities of SFK and FAK in three-dimensional (3D) settings. We observed that SFK and FAK in the lipid rafts and nonrafts are differently regulated by fluid flow and pro-inflammatory cytokines. Inhibition of FAK in the lipid rafts blocked SFK response to fluid flow, while inhibition of SFK in the non-rafts blocked FAK activation by the cytokines. Ex-vivo FRET imaging of mouse cartilage explants showed that intermediate level of interstitial fluid flow selectively decreased cytokine-induced SFK/FAK activation. These findings suggest that SFK and FAK exert distinctive molecular hierarchy depending on their subcellular location and extracellular stimuli.

Suppressive Effect of the n-Hexane Extract of Litsea japonica Fruit Flesh on Monosodium-Iodoacetate-Induced Osteoarthritis in Rats

We examined the antiosteoarthritic effect of the n-hexane extract of Litsea japonica fruit flesh (LJF-HE) in a rat model of monosodium-iodoacetate- (MIA-) induced osteoarthritis. LJF-HE significantly reduced the difference in weight-bearing capabilities of the hind paws between healthy and MIA-treated rats. Histological examination of the knee joints indicated that LJF-HE suppressed cartilage and bone destruction. Additionally, there were decreases in the expression of matrix metalloproteinase-2 and metalloproteinase-9 and cyclooxygenase-2 in the joints. The serum levels of deoxypyridinoline (DPD) and osteocalcin, which are markers of bone metabolism, also decreased. Furthermore, LJF-HE significantly suppressed infiltration of inflammatory cells into the synovium and inhibited the expression of proinflammatory cytokines such as tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1, and IL-6 in the joints and serum. The serum levels of leukotriene B4 and lipoxygenase were also significantly lowered by LJF-HE. Finally, LJF-HE inhibited the production of nitric oxide, prostaglandin E2, IL-6, and TNF-α in lipopolysaccharide-activated macrophages, which might be associated with inhibited phosphorylation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase. Our data suggest that LJF-HE has an anti-inflammatory effect and may have potential as an antiosteoarthritic agent.

Effects of Tribulus terrestris on monosodium iodoacetate‑induced osteoarthritis pain in rats

Tribulus terrestris L. (T. terrestris) has been used as a traditional medicine for the treatment of diuretic, lithontriptic, edema and urinary infections. Previous studies have indicated that it is effective in improving inflammation by regulating tumor necrosis factor‑α (TNF)‑α, interleukin (IL)‑6, IL‑10, nitric oxide (NO) and cyclooxygenase (COX)‑2. However, the effects and mechanism of action of T. terrestris on osteoarthritis (OA) remain unknown. Therefore, the present study aimed to evaluate the effects of the ethanolic extract of T. terrestris (ETT) in a monosodium iodoacetate (MIA)‑induced OA animal model. OA was induced in LEW/SSNHSD rats by intra‑articular injection of MIA. Morphometric changes and parameters of the tibial trabecular bone were determined using micro‑computed tomography. The molecular mechanisms of ETT in OA were investigated using reverse transcription‑polymerase chain reaction, western blotting and gelatin zymogram analysis. Treatment with ETT attenuated MIA‑induced OA, and this effect was mediated by the downregulation of NO synthase 2, COX‑2, TNF‑α and IL‑6. Furthermore, the ETT‑mediated attenuation of OA was also dependent on the expression of matrix metalloproteinases‑2 and ‑9. The results of the current study indicate that further evaluation of the mechanisms underlying the attenuation of MIA‑induced OA by ETT are required, and may support the development of ETT as a potential therapeutic agent for the treatment of inflammatory diseases such as OA.

Integrative epigenomics, transcriptomics and proteomics of patient chondrocytes reveal genes and pathways involved in osteoarthritis

Osteoarthritis (OA) is a common disease characterized by cartilage degeneration and joint remodeling. The underlying molecular changes underpinning disease progression are incompletely understood. We investigated genes and pathways that mark OA progression in isolated primary chondrocytes taken from paired intact versus degraded articular cartilage samples across 38 patients undergoing joint replacement surgery (discovery cohort: 12 knee OA, replication cohorts: 17 knee OA, 9 hip OA patients). We combined genome-wide DNA methylation, RNA sequencing, and quantitative proteomics data. We identified 49 genes differentially regulated between intact and degraded cartilage in at least two -omics levels, 16 of which have not previously been implicated in OA progression. Integrated pathway analysis implicated the involvement of extracellular matrix degradation, collagen catabolism and angiogenesis in disease progression. Using independent replication datasets, we showed that the direction of change is consistent for over 90% of differentially expressed genes and differentially methylated CpG probes. AQP1, COL1A1 and CLEC3B were significantly differentially regulated across all three -omics levels, confirming their differential expression in human disease. Through integration of genome-wide methylation, gene and protein expression data in human primary chondrocytes, we identified consistent molecular players in OA progression that replicated across independent datasets and that have translational potential.

Thermoresponsive Elastin-b-Collagen-Like Peptide Bioconjugate Nanovesicles for Targeted Drug Delivery to Collagen-Containing Matrices

Over the past few decades, (poly)peptide block copolymers have been widely employed in generating well-defined nanostructures as vehicles for targeted drug delivery applications. We previously reported the assembly of thermoresponsive nanoscale vesicles from an elastin-b-collagen-like peptide (ELP-CLP). The vesicles were observed to dissociate at elevated temperatures, despite the LCST-like behavior of the tethered ELP domain, which is suggested to be triggered by the unfolding of the CLP domain. Here, the potential of using the vesicles as drug delivery vehicles for targeting collagen-containing matrices is evaluated. The sustained release of an encapsulated model drug was achieved over a period of 3 weeks, following which complete release could be triggered via heating. The ELP-CLP vesicles show strong retention on a collagen substrate, presumably through collagen triple helix interactions. Cell viability and proliferation studies using fibroblasts and chondrocytes suggest that the vesicles are highly cytocompatible. Additionally, essentially no activation of a macrophage-like cell line is observed, suggesting that the vesicles do not initiate an inflammatory response. Endowed with thermally controlled delivery, the ability to bind collagen, and excellent cytocompatibility, these ELP-CLP nanovesicles are suggested to have significant potential in the controlled delivery of drugs to collagen-containing matrices and tissues.

LncRNA-UCA1 enhances MMP-13 expression by inhibiting miR-204-5p in human chondrocytes

Osteoarthritis (OA) is a common degenerative disease characterized by degeneration of articular cartilage. Increasing studies showed that long noncoding RNAs (lncRNAs) play important roles in the cartilage damage. However, little is known about the role of UCA1 in the osteoarthritis. The expression level of UCA1 was upregulated in the OA cartilage. Overexpression of UCA1 suppressed the miR-204-5p expression in the chondrocytes. The expression of miR-204-5p was downregulated in the OA cartilage. Moreover, the expression of miR-204-5p was negatively correlated with the UCA1 expression in the OA cartilage. Elevated expression of UCA1 promoted the chondrocytes cell proliferation and overexpression of miR-204-5p suppressed chondrocytes cell proliferation. In addition, overexpression of UCA1 decreased the expression of the type II collagen and type IV collagen expression in the chondrocytes. Elevated expression of miR-204-5p promoted the type II collagen and type IV collagen expression in the chondrocytes. We idetified MMP-13 was a direct target gene of miR-204-5p in the chondrocytes. Overexpression of UCA1 enhanced the MMP-13 expression in the chondrocytes. Elevated expression of UCA1 regulated the chondrocytes cell proliferation and collagen expression through inhibiting the miR-204-5p expression.These results suggested that UCA1 played as an important regulator of survival and matrix synthesis of chondrocytes partly through suppressing the miR-204-5p expression.

3'-Sialyllactose protects against osteoarthritic development by facilitating cartilage homeostasis

3′‐Sialyllactose has specific physiological functions in a variety of tissues; however, its effects on osteoarthritic development remain unknown. Here, we demonstrated the function of 3′‐sialyllactose on osteoarthritic cartilage destruction. In vitro and ex vivo, biochemical and histological analysis demonstrated that 3′‐sialyllactose was sufficient to restore the synthesis of Col2a1 and accumulation of sulphated proteoglycan, a critical factor for cartilage regeneration in osteoarthritic development, and blocked the expression of Mmp3, Mmp13 and Cox2 induced by IL‐1β, IL‐6, IL‐17 and TNF‐α, which mediates cartilage degradation. Further, reporter gene assays revealed that the activity of Sox9 as a transcription factor for Col2a1 expression was accelerated by 3′‐sialyllactose, whereas the direct binding of NF‐κB to the Mmp3, Mmp13 and Cox2 promoters was reduced by 3′‐sialyllactose in IL‐1β‐treated chondrocytes. Additionally, IL‐1β induction of Erk phosphorylation and IκB degradation, representing a critical signal pathway for osteoarthritic development, was totally blocked by 3′‐sialyllactose in a dose‐dependent manner. In vivo, 3′‐sialyllactose protected against osteoarthritic cartilage destruction in an osteoarthritis mouse model induced by destabilization of the medial meniscus, as demonstrated by histopathological analysis. Our results strongly suggest that 3′‐sialyllactose may ameliorate osteoarthritic cartilage destruction by cartilage regeneration via promoting Col2a1 production and may inhibit cartilage degradation and inflammation by suppressing Mmp3, Mmp13 and Cox2 expression. The effects of 3′‐sialyllactose could be attributed in part to its regulation of Sox9 or NF‐κB and inhibition of Erk phosphorylation and IκB degradation. Taken together, these effects indicate that 3′‐sialyllactose merits consideration as a natural therapeutic agent for protecting against osteoarthritis.

Effect of Naringin on Monosodium Iodoacetate-Induced Osteoarthritis Pain in Rats

Background

The aim of the current study was to evaluate the anti-osteoarthritic and anti-inflammatory effect of naringin in a monosodium iodoacetate (MIA)- induced osteoarthritis (OA) model in rats. The anti-osteoarthritic potential of naringin was evaluated against the MIA-induced OA rat model.

Material/Methods

Wistar rats were used for the study and were divided into the following groups: normal control (saline-treated); group II (MIA-treated): group III (MIA+Naringin), and group IV (MIA+Indomethacin). The potential effect of naringin was evaluated via its effect on the level of proinflammatory cytokines, measuring the weight-bearing distribution, and histopathological analysis.

Result

The anti-inflammatory effect of naringin was assessed in vitro in lipopolysaccharide-induced RAW 264.6 cells. The results suggest that naringin exerts an anti-inflammatory effect via reducing the production of the prostaglandin E₂ (PGE₂), nitric oxide (NO), interlukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in LPS-induced RAW cells. Additionally, naringin also supported the recovery of hind-limb weight-bearing, reduced the generation or production of inflammatory mediator and proinflammatory cytokines, and protected the tissue from the damage in the OA model.

Conclusions

Naringin appears to be an effective therapeutic drug for the treatment of the OA and OA-related symptoms.

A bioinformatic analysis of microRNAs role in osteoarthritis

OBJECTIVE

To evaluate the underlying function of microRNAs (miRNAs) in osteoarthritis (OA).

DESIGN

A bioinformatic analysis of miRNAs-OA studies was completed in multiple databases. All identified articles were assessed using specific inclusion and exclusion criteria (Eligible case-control studies for the present study included those which investigated miRNAs differential expression in cartilage tissues and cells of OA and controls. Abstracts, case reports, conference presentations, editorials, and expert opinions were excluded.). We performed bioinformatic analysis and assessed which miRNAs are commonly elevated or decreased in cartilage of OA, and assessed putative targets of these miRNAs using TargetScan, Database for Annotation, Visualization and Integrated Discovery (DAVID), FunRich and String.

RESULTS

Fifty seven studies were included in this study. Our current review has identified 46 differentially expressed miRNAs involved in autophagy, inflammation, chondrocyte apoptosis, chondrocyte differentiation & homeostasis, chondrocyte metabolism and degradation of the extracellular matrix (ECM). Additionally, our literature search identified a wide range of miRNAs that have been shown to be differentially expressed in OA. The function of up-regulated miRNAs primarily target nucleus, whereas the function of down-regulated miRNAs primarily target transcription.

CONCLUSIONS

Comprehensive analysis of all miRNAs studies reveals cooperation in miRNA signatures and suggests that there may be two biologically synergic classes of miRNAs that are associated with OA. This finding suggests that miRNAs may be useful as diagnostic biomarkers and/or may provide new therapeutic targets in OA. Furthermore, a better understanding of the targets of these miRNAs will accelerate biomedical discoveries and improve clinical care based on new knowledge of OA-related disease mechanisms.

* CRISPR-Based Epigenome Editing of Cytokine Receptors for the Promotion of Cell Survival and Tissue Deposition in Inflammatory Environments

Musculoskeletal diseases have been associated with inflammatory cytokine action, particularly action by TNF-α and IL-1β. These inflammatory cytokines promote apoptosis and senescence of cells in diseased tissue and extracellular matrix breakdown. Stem cell-based therapies are being considered for the treatment of musculoskeletal diseases, but the presence of these inflammatory cytokines will have similar deleterious action on therapeutic cells delivered to these environments. Methods that prevent inflammatory-induced apoptosis and proinflammatory signaling, in cell and pathway-specific manners are needed. In this study we demonstrate the use of clustered regularly interspaced short palindromic repeats (CRISPR)-based epigenome editing to alter cell response to inflammatory environments by repressing inflammatory cytokine cell receptors, specifically TNFR1 and IL1R1. We targeted CRISPR/Cas9-based repressors to TNFR1 and IL1R1 gene regulatory elements in human adipose-derived stem cells (hADSCs) and investigated the functional outcomes of repression of these genes. Efficient signaling regulation was demonstrated in engineered hADSCs, as activity of the downstream transcription factor NF-κB was significantly reduced or maintained at baseline levels in the presence of TNF-α or IL-1β. Pellet culture of undifferentiated hADSCs demonstrated improved survival in engineered hADSCs treated with TNF-α or IL-1β, while having little effect on their immunomodulatory properties. Furthermore, engineered hADSCs demonstrated improved chondrogenic differentiation capacity in the presence of TNF-α or IL-1β, as shown by superior production of glycosaminglycans in this inflammatory environment. Overall this work demonstrates a novel method for modulating cell response to inflammatory signaling that has applications in engineering cells delivered to inflammatory environments, and as a direct gene therapy to protect endogenous cells exposed to chronic inflammation, as observed in a broad spectrum of degenerative musculoskeletal pathology.

An overview of benzo[b]thiophene-based medicinal chemistry

Among sulfur containing heterocycles, benzothiophene and its derivatives are at the focus as these candidates have structural similarities with active compounds to develop new potent lead molecules in drug design. Benzo[b]thiophene scaffold is one of the privileged structures in drug discovery as this core exhibits various biological activities allowing them to act as anti-microbial, anti-cancer, anti-inflammatory, anti-oxidant, anti-tubercular, anti-diabetic, anti-convulsant agents and many more. Further, numerous benzothiophene-based compounds as clinical drugs have been extensively used to treat various types of diseases with high therapeutic potency, which has led to their extensive developments. Due to the wide range of biological activities of benzothiophene, their structure activity relationships (SAR) have generated interest among medicinal chemists, and this has culminated in the discovery of several lead molecules against numerous diseases. The present review is endeavoring to highlight the progress in the various pharmacological activities of benzo[b]thiophene derivatives. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic benzothiophene-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes. Also, SAR studies that highlight the chemical groups responsible for evoking the potential activities of benzothiophene derivatives are studied and compared.

Isorhamnetin inhibits IL‑1β‑induced expression of inflammatory mediators in human chondrocytes

Isorhamnetin (ISH) is a flavonoid primarily obtained from the fruit of Hippophae rhamnoides L., which possesses anti‑inflammatory properties. However, the effect of ISH on the expression of inflammatory mediators in response to interleukin (IL)‑1β stimulation has not been elucidated. The present study investigated the effects of ISH on the expression of inflammatory mediators in human chondrocytes, induced by IL‑1β. The results of the present study demonstrated that pretreatment with ISH inhibited the expression of stromelysin‑1 and collagenase 3 in chondrocytes, induced by IL‑1β. Pretreatment with ISH inhibited the IL‑1β‑stimulated synthesis of NO and prostaglandin E2 induced by IL‑1β, in addition to the expression of inducible nitric oxide synthase and prostaglandin G/H synthase 2 in chondrocytes. Additionally, ISH inhibited the expression of nuclear factor (NF)‑κB and transcription factor p65, and the degradation of NF‑κB inhibitor α induced by IL‑1β in chondrocytes. In conclusion, the results of the present study indicated that ISH exhibited anti‑inflammatory and chondroprotective effects in IL‑1β‑stimulated chondrocytes. The results of the present study suggest that ISH may be a potential agent in the future treatment of osteoarthritis.

Increased Activity of the Chondrocyte Translational Apparatus Accompanies Osteoarthritic Changes in Human and Rodent Knee Cartilage

OBJECTIVE

Degeneration of articular cartilage is central to the pathology of osteoarthritis (OA). However, the molecular mechanisms leading to these irreversible changes are still poorly understood. This study was undertaken to investigate how changes in the chondrocyte translational apparatus may contribute to the development and progression of knee OA.

METHODS

Articular cartilage from the knees of normal healthy subjects and patients with OA was used to analyze the activity of different components of the translational machinery. Chondrocytes isolated from lesional and nonlesional areas of the human OA cartilage were used to estimate the relative rate of protein synthesis by metabolic labeling. Experimental OA was induced by transection of the anterior cruciate ligament of rats to investigate changes in the translational apparatus associated with OA. The role of interleukin-1β (IL-1β) signaling was assessed in vitro using rat articular chondrocytes. In human or rodent knee cartilage, messenger RNA expression was analyzed by quantitative polymerase chain reaction, and protein levels were determined by immunohistochemistry and Western blotting.

RESULTS

Several novel traits of OA chondrocytes were identified, including up-regulation of the serine/threonine kinases Akt-2 and Akt-3 at the posttranscriptional level and an increased rate of total protein synthesis, likely attributable to inactivation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1), a known repressor of cap-dependent translation. Inactivation of 4E-BP1 was dependent on the activity of mechanistic target of rapamycin and was crucial for the up-regulation of protein synthesis in general and expression of matrix metalloproteinase 13 and ADAMTS-5 in particular. In addition, treatment of articular chondrocytes with IL-1β led to inactivation of 4E-BP1 and up-regulation of protein synthesis.

CONCLUSION

Precise control of protein synthesis is vital for cartilage homeostasis, and its dysregulation contributes to the molecular pathology of OA. The results of this study therefore identify a novel set of potential therapeutic targets to ameliorate the effects of knee OA.

Role of Fibulin 3 in Aging-Related Joint Changes and Osteoarthritis Pathogenesis in Human and Mouse Knee Cartilage

OBJECTIVE

The EFEMP1 gene encoding fibulin 3 is specifically expressed in the superficial zone (SZ) of articular cartilage. The aims of this study were to examine the expression patterns of fibulin 3 in the knee joints during aging and during osteoarthritis (OA) and to determine the role of fibulin 3 in the pathogenesis of OA.

METHODS

Immunohistochemical analysis was performed on normal and OA knee cartilage samples from humans and mice. Experimental OA was induced in wild-type and fibulin 3^-/- mice, and the severity of OA was evaluated by histologic scoring. To examine fibulin 3 function, human chondrocyte monolayer cultures were transfected with small interfering RNA (siRNA), followed by quantitative polymerase chain reaction and Western blot analyses. Human bone marrow-derived mesenchymal stem cells (BM-MSCs) were transduced with an EFEMP1 lentivirus and analyzed for markers of chondrogenesis.

RESULTS

Fibulin 3 was specifically expressed in the SZ of normal knee joint cartilage from humans and mice, and the expression levels declined with aging. Both aging-related OA and experimental OA were significantly more severe in fibulin 3^-/- mice compared with wild-type mice. Fibulin 3 expression was high in undifferentiated human BM-MSCs and decreased during chondrogenesis. Suppression of fibulin 3 by siRNA significantly increased the expression of SOX9, type II collagen, and aggrecan in human articular chondrocytes, while overexpression of fibulin 3 inhibited chondrogenesis in BM-MSCs.

CONCLUSION

Fibulin 3 is specifically expressed in the SZ of articular cartilage and its expression is reduced in aging and OA. Fibulin 3 regulates differentiation of adult progenitor cells, and its aging-related decline is an early event in the pathogenesis of OA. Preventing aging-associated loss of fibulin 3 or restoring it to normal levels in SZ chondrocytes has the potential to delay or prevent the onset of OA.

Rapamycin Maintains the Chondrocytic Phenotype and Interferes with Inflammatory Cytokine Induced Processes

Osteoarthritis (OA) is hallmarked by a progressive degradation of articular cartilage. Besides risk factors including trauma, obesity or genetic predisposition, inflammation has a major impact on the development of this chronic disease. During the course of inflammation, cytokines such as tumor necrosis factor-alpha(TNF-α) and interleukin (IL)-1β are secreted by activated chondrocytes as well as synovial cells and stimulate the production of other inflammatory cytokines and matrix degrading enzymes. The mTORC1 inhibitor rapamycin is a clinical approved immunosuppressant and several studies also verified its chondroprotective effects in OA. However, the effect of blocking the mechanistic target of rapamycin complex (mTORC)1 on the inflammatory status within OA is not well studied. Therefore, we aimed to investigate if inhibition of mTORC1 by rapamycin can preserve and sustain chondrocytes in an inflammatory environment. Patient-derived chondrocytes were cultured in media supplemented with or without the mTORC1 inhibitor rapamycin. To establish an inflammatory environment, either TNF-α or IL-1β was added to the media (=OA-model). The chondroprotective and anti-inflammatory effects of rapamycin were evaluated using sulfated glycosaminoglycan (sGAG) release assay, Caspase 3/7 activity assay, lactate dehydrogenase (LDH) assay and quantitative real time polymerase chain reaction (PCR). Blocking mTORC1 by rapamycin reduced the release and therefore degradation of sGAGs, which are components of the extracellular matrix secreted by chondrocytes. Furthermore, blocking mTORC1 in OA chondrocytes resulted in an enhanced expression of the main chondrogenic markers. Rapamycin was able to protect chondrocytes from cell death in an OA-model shown by reduced Caspase 3/7 activity and diminished LDH release. Furthermore, inhibition of mTORC1 preserved the chondrogenic phenotype of OA chondrocytes, but also reduced inflammatory processes within the OA-model. This study highlights that blocking mTORC1 is a new and promising approach for treating OA. Low side effects make rapamycin an attractive implementation to existing therapeutic strategies. We showed that rapamycin's chondroprotective property might be due to an interference with IL-1β triggered inflammatory processes.

Increased DNA Methylation and Reduced Expression of Transcription Factors in Human Osteoarthritis Cartilage

OBJECTIVE

To analyze the methylome of normal and osteoarthritic (OA) knee articular cartilage and to determine the role of DNA methylation in the regulation of gene expression in vitro.

METHODS

DNA was isolated from human normal (n = 11) and OA (n = 12) knee articular cartilage and analyzed using the Infinium HumanMethylation450 BeadChip array. To integrate methylation and transcription, RNA sequencing was performed on normal and OA cartilage and validated by quantitative polymerase chain reaction. Functional validation was performed in the human TC28 cell line and primary chondrocytes that were treated with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-dC).

RESULTS

DNA methylation profiling revealed 929 differentially methylated sites between normal and OA cartilage, comprising a total of 500 individual genes. Among these, 45 transcription factors that harbored differentially methylated sites were identified. Integrative analysis and subsequent validation showed a subset of 6 transcription factors that were significantly hypermethylated and down-regulated in OA cartilage (ATOH8, MAFF, NCOR2, TBX4, ZBTB16, and ZHX2). Upon 5-aza-dC treatment, TC28 cells showed a significant increase in gene expression for all 6 transcription factors. In primary chondrocytes, ATOH8 and TBX4 were increased after 5-aza-dC treatment.

CONCLUSION

Our findings reveal that normal and OA knee articular cartilage have significantly different methylomes. The identification of a subset of epigenetically regulated transcription factors with reduced expression in OA may represent an important mechanism to explain changes in the chondrocyte transcriptome and function during OA pathogenesis.

Coculture of bovine cartilage with synovium and fibrous joint capsule increases aggrecanase and matrix metalloproteinase activity

Background

A hallmark of osteoarthritis is increased proteolytic cleavage of aggrecan. Cross talk between cartilage and the synovium + joint capsule (SJC) can drive cartilage degradation by activating proteases in both tissues. We investigated aggrecan proteolysis patterns in cartilage explants using a physiologically relevant explant model of joint injury combining cartilage mechanical compression and coincubation with SJC.

Methods

Bovine cartilage explants were untreated; coincubated with SJC; or subjected to mechanical injury and coincubated with SJC, mechanical injury alone, or mechanical injury and incubated with tumor necrosis factor-α (TNF-α). To compare the patterns of aggrecan proteolysis between 6 h and 16 days, release of sulfated glycosaminoglycans and specific proteolytic aggrecan fragments into medium or remaining in cartilage explants was measured by dimethylmethylene blue and Western blot analysis.

Results

Aggrecanase activity toward aggrecan was observed in all conditions, but it was directed toward the TEGE↓ARGS interglobular domain (IGD) site only when cartilage was coincubated with SJC or TNF-α. Matrix metalloproteinase (MMP) activity at the aggrecan IGD site (IPES↓FFGV) was not detected when cartilage was exposed to TNF-α (up to 6 days), but it was in all other conditions. Compared with when bovine cartilage was left untreated or subjected to mechanical injury alone, additional aggrecan fragment types were released into medium and proteolysis of aggrecan started at an earlier time when SJC was present.

Conclusions

Indicative of different proteolytic pathways for aggrecan degradation, the SJC increases both aggrecanase and MMP activity toward aggrecan, whereas TNF-α inhibits MMP activity against the IGD of aggrecan.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1318-9) contains supplementary material, which is available to authorized users.

Recent developments in emerging therapeutic targets of osteoarthritis

Purpose of review

Despite the tremendous individual suffering and socioeconomic burden caused by osteoarthritis, there are currently no effective disease-modifying treatment options. This is in part because of our incomplete understanding of osteoarthritis disease mechanism. This review summarizes recent developments in therapeutic targets identified from surgical animal models of osteoarthritis that provide novel insight into osteoarthritis pathology and possess potential for progression into preclinical studies.

Recent findings

Several candidate pathways and processes that have been identified include chondrocyte autophagy, growth factor signaling, inflammation, and nociceptive signaling. Major strategies that possess therapeutic potential at the cellular level include inhibiting autophagy suppression and decreasing reactive oxygen species (ROS) production. Cartilage anabolism and prevention of cartilage degradation has been shown to result from growth factor signaling modulation, such as TGF-β, TGF-α, and FGF; however, the results are context-dependent and require further investigation. Pain assessment studies in rodent surgical models have demonstrated potential in employing anti-NGF strategies for minimizing osteoarthritis-associated pain.

Summary

Studies of potential therapeutic targets in osteoarthritis using animal surgical models are helping to elucidate osteoarthritis pathology and propel therapeutics development. Further studies should continue to elucidate pathological mechanisms and therapeutic targets in various joint tissues to improve overall joint health.

Different doses of strontium ranelate and mechanical vibration modulate distinct responses in the articular cartilage of ovariectomized rats

OBJECTIVE

To investigate the effects of different strontium ranelate (SrR) doses alone or in combination with low-intensity and high-frequency mechanical vibration (MV) on articular cartilage in ovariectomized rats.

DESIGN

Fifty 6-month-old female Wistar rats underwent ovariectomy (OVX) and after 3 months were divided into: control group (Control); SrR 300 mg/kg/day (SrR300); SrR 625 mg/kg/day (SrR625); MV; SrR 625 mg/kg/day plus MV (SrR625 + MV). The vehicle and the SrR were administered by gavage 7 days/week and vibration (0.6 g/60 Hz) was performed for 20 min/day, 5 days/week. Bone mineral density (BMD) and body composition were evaluated by densitometry. Changes in cartilage were assessed 90 days after treatment by histomorphometry; immunohistochemistry analysis evaluating cell death (caspase-3), tumor necrosis factor-α (TNF-α), metalloproteinase 9 (MMP-9) and type II collagen; Osteoarthritis Research Society International (OARSI) grading system and glycosaminoglycans (GAGs) analyses.

RESULTS

SrR-treated groups exhibited a lower OARSI grade, a smaller number of chondrocyte clusters, increased levels of chondroitin sulfate (CS) and decreased expression of caspase-3. Additionally, compared to all the groups, SrR300 exhibited increased levels of hyaluronic acid (HA). Vibration applied alone or in combination accelerated cartilage degradation, as demonstrated by increased OARSI grade, reduced number of chondrocytes, increased number of clusters, elevated expression of type II collagen and cell death, and was accompanied by decreased amounts of CS and HA; however, MV alone was able to reduce MMP-9.

CONCLUSIONS

SrR and vibration modulate distinct responses in cartilage. Combined treatment accelerates degeneration. In contrast, SrR treatment at 300 mg/kg/day attenuates osteoarthritis (OA) progression, improving cartilage matrix quality and preserving cell viability in ovariectomized rats.

Correlations between ultrasonographic findings, clinical scores, and depression in patients with knee osteoarthritis

OBJECTIVE

This study aimed to explore correlations between the presence of depression, clinical scores, and ultrasonographic (US) grading in osteoarthritis (OA) patients and to clarify if depressive symptoms might cause a discrepancy between US findings and clinical scores.

MATERIAL AND METHODS

Two hundred patients with primary knee OA and 100 healthy hospital volunteers of the same age and sex not complaining of knee troubles participated in this study. We evaluated depressive symptoms in all participants using the Beck Depression Inventory (BDI) scale. Thorough clinical examination was performed, including assessment using the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC) for disability. All patients underwent US examination of their affected knees.

RESULTS

Depression was detected in 60 patients with knee OA (30%) and in 5 controls (5%). The mean of BDI score was 12.8±12.2 in OA patients and 5.8±3.2 in controls, and this difference was statistically significant (p=0.03). Correlations of BDI with both body mass index (BMI) (p=0.04) and Numerical Rating Scale of Pain (NRSP) score (p=0.006) were significant, while correlations of BDI with both the ages of our patients (p=0.74) and their disease duration (p=0.88) were insignificant. There were statistically significant correlations between patients' disease duration and US measurements regarding osteophyte length, lateral femoral cartilage thickness, medial femoral cartilage thickness, and thickness of the quadriceps tendon despite of the presence of insignificant correlations between disease duration and both the effusion volume and volume of Baker's cysts. There were statistically significant correlations between patients' disease duration and US measurements except for effusion volume and volume of Baker's cysts. There were statistically significant correlations between the NRSP score in OA patients and BDI (p=0.006) and all US measurements apart from lateral femoral cartilage thickness, medial femoral cartilage thickness, and thickness of quadriceps tendon. There were statistically significant correlations between BDI in OA patients and the WOMAC (p=0.005), Kellgren-Lawrence (KL) grading (p=0.034), and US grading (p=0.041).

CONCLUSION

The presence of knee effusion, Baker's cysts, osteophytes, and high BMI have a great impact on the pain and disability associated with OA. Higher clinical scores, radiographic scores, and US scores correlate with the emergence of depression in OA patients.

Natural antioxidant polyphenols on inflammation management: Anti-glycation activity vs metalloproteinases inhibition

The diet polyphenols are a secondary metabolites of plants able to act on inflammation process. Their anti-inflammatory activity is articulated through several mechanisms that are related to their antioxidative and radical scavengers properties. Our work is focused on a novel approach to inflammatory disease management, based on anti-glycative and matrix metalloproteinases (MMPs) inhibition effects, as a connected phenomena. To better understand these correlation, polyphenols Structure-Activity Relationship (SAR) studies were also reported. The antioxidant polyphenols inhibit the AGEs at different levels of the glycation process in the following ways: (1) prevention of Amadori adduct oxidation; (2) trapping reactive dycarbonyl compounds; (3) attenuation of receptor for AGEs (RAGE) expression. Moreover, several flavonoids with radical scavenging property showed also MMPs inhibition interact directly with MMPs or indirectly via radical scavengers and AGEs reduction. The essential polyphenols features involved in these mechanisms are C2-C3 double bond and number and position of hydroxyl, glycosyl and O-methyl groups. These factors induce a change in molecular planarity interfering with the hydrogen bond formation, electron delocalization and metal ion chelation. In particular, C2-C3 double bond improve the antioxidant and MMPs inhibition, while the hydroxylation, glycosylation and methylation induce a positive and negative correlation, respectively.

Wogonoside inhibits IL-1β induced catabolism and hypertrophy in mouse chondrocyte and ameliorates murine osteoarthritis

The inflammatory environment is correlated with extracellular matrix (ECM) degradation and chondrocyte hypertrophy in the development of osteoarthritis (OA). Previous studies have reported the anti-inflammatory effects of wogonoside in several diseases. In the present study, we investigated the protective effects of wogonoside in relation to the development of OA and delineated the potential mechanism. In vitro, wogonoside decreased the production of pro-inflammatory cytokines like Nitric oxide (NO), prostaglandin E2 (PGE₂), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6). It also inhibited the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) both at gene and protein levels. Wogonoside also inhibited hypertrophy and the generation of vascular endothelial growth factor (VEGF) in interleukin-1β (IL-1β)-induced chondrocytes. Moreover, wogonoside promoted the expression of anabolic factors Sox-9, type two collagen and aggrecan while inhibiting the expression of catabolic factors such as matrix metalloproteinases (MMPs) and thrombospondin motifs 5 (ADAMTS-5) in mouse chondrocytes. Mechanistically, we found that wogonoside inhibited nuclear factor kappa B/ hypoxia-inducible factor two alpha (NF-κB/HIF-2α) activation via the phosphatidylinositol 3 kinase (PI3K) /AKT pathway. The protective effects of wogonoside were also observed in vivo and the pharmacokinetic results of wogonoside indicated that good systemic exposure was achievable after oral administration of wogonoside. In conclusion, our stduy demonstrates that wogonoside attenuates IL-1β-induced ECM degradation and hypertrophy in mouse chondrocytes via suppressing the activation of NF-κB/HIF-2α by the PI3K/AKT pathway. Moreover, wogonoside ameliorates OA progression in vivo, indicating that wogonoside may serve as a promising therapeutic agent for the treatment of OA.

Adipokines induce pro-inflammatory factors in activated Cd4+ T cells from osteoarthritis patient

Osteoarthritis (OA) is a chronic systemic musculoskeletal disorder involving inflammation, immunity, and metabolic alterations. OA is commonly regarded as non-inflammatory disease; still inflammation is recognized as contributing to the symptoms and progression of OA. New evidence suggests that adipokines are involved in the pathophysiology of OA and might modulate the production of inflammatory mediators including in immune cells. However, the role of immune component in osteoarthritis is still poorly investigated. To gain further insights into the interaction of immune cells in OA and the role of adipokines on these cells, we performed experiments aimed to determine the cytokine profile in activated CD4⁺ T cells from OA patients. For completeness, we also explored the cross talk between T lymphocytes and chondrocytes in OA by co-culturing human primary chondrocytes with activated CD4⁺ T cells in two ways: the first by incubating the cells by direct contact (D.C.) or by transwell system. Our results show that the exposure of activated CD4⁺ T cells to adipokines modulates IL-6, IL-8, and CCL-3 production. In addition, the production of key macromolecules of ECM (aggrecan and collagen-2) and matrix metalloproteinase 13 (MMP-13) in co-cultured chondrocytes with activated CD4⁺ T cells was altered. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1299-1303, 2017.

Molecular mechanisms underlying osteoarthritis development: Notch and NF-κB

Osteoarthritis (OA) is a multi-factorial and highly prevalent joint disorder worldwide. Since the establishment of murine surgical knee OA models in 2005, many of the key molecules and signalling pathways responsible for OA development have been identified. Here we review the roles of two multi-functional signalling pathways in OA development: Notch and nuclear factor kappa-light-chain-enhancer of activated B cells. Previous studies have identified various aspects of articular chondrocyte regulation by these pathways. However, comprehensive understanding of the molecular networks regulating articular cartilage homeostasis and OA pathogenesis is needed.

CCL2/CCR2, but not CCL5/CCR5, mediates monocyte recruitment, inflammation and cartilage destruction in osteoarthritis

OBJECTIVES

While various monocyte chemokine systems are increased in expression in osteoarthritis (OA), the hierarchy of chemokines and chemokine receptors in mediating monocyte/macrophage recruitment to the OA joint remains poorly defined. Here, we investigated the relative contributions of the CCL2/CCR2 versus CCL5/CCR5 chemokine axes in OA pathogenesis.

METHODS

Ccl2-, Ccr2-, Ccl5- and Ccr5-deficient and control mice were subjected to destabilisation of medial meniscus surgery to induce OA. The pharmacological utility of blocking CCL2/CCR2 signalling in mouse OA was investigated using bindarit, a CCL2 synthesis inhibitor, and RS-504393, a CCR2 antagonist. Levels of monocyte chemoattractants in synovial tissues and fluids from patients with joint injuries without OA and those with established OA were investigated using a combination of microarray analyses, multiplexed cytokine assays and immunostains.

RESULTS

Mice lacking CCL2 or CCR2, but not CCL5 or CCR5, were protected against OA with a concomitant reduction in local monocyte/macrophage numbers in their joints. In synovial fluids from patients with OA, levels of CCR2 ligands (CCL2, CCL7 and CCL8) but not CCR5 ligands (CCL3, CCL4 and CCL5) were elevated. We found that CCR2+ cells are abundant in human OA synovium and that CCR2+ macrophages line, invade and are associated with the erosion of OA cartilage. Further, blockade of CCL2/CCR2 signalling markedly attenuated macrophage accumulation, synovitis and cartilage damage in mouse OA.

CONCLUSIONS

Our findings demonstrate that monocytes recruited via CCL2/CCR2, rather than by CCL5/CCR5, propagate inflammation and tissue damage in OA. Selective targeting of the CCL2/CCR2 system represents a promising therapeutic approach for OA.

Local clearance of senescent cells attenuates the development of post-traumatic osteoarthritis and creates a pro-regenerative environment

Senescent cells (SnCs) accumulate in many vertebrate tissues with age and contribute to age-related pathologies, presumably through their secretion of factors contributing to the senescence-associated secretory phenotype (SASP). Removal of SnCs delays several pathologies and increases healthy lifespan. Aging and trauma are risk factors for the development of osteoarthritis (OA), a chronic disease characterized by degeneration of articular cartilage leading to pain and physical disability. Senescent chondrocytes are found in cartilage tissue isolated from patients undergoing joint replacement surgery, yet their role in disease pathogenesis is unknown. To test the idea that SnCs might play a causative role in OA, we used the p16-3MR transgenic mouse, which harbors a p16^INK4a (Cdkn2a) promoter driving the expression of a fusion protein containing synthetic Renilla luciferase and monomeric red fluorescent protein domains, as well as a truncated form of herpes simplex virus 1 thymidine kinase (HSV-TK). This mouse strain allowed us to selectively follow and remove SnCs after anterior cruciate ligament transection (ACLT). We found that SnCs accumulated in the articular cartilage and synovium after ACLT, and selective elimination of these cells attenuated the development of post-traumatic OA, reduced pain and increased cartilage development. Intra-articular injection of a senolytic molecule that selectively killed SnCs validated these results in transgenic, non-transgenic and aged mice. Selective removal of the SnCs from in vitro cultures of chondrocytes isolated from patients with OA undergoing total knee replacement decreased expression of senescent and inflammatory markers while also increasing expression of cartilage tissue extracellular matrix proteins. Collectively, these findings support the use of SnCs as a therapeutic target for treating degenerative joint disease.

Daily oral consumption of hydrolyzed type 1 collagen is chondroprotective and anti-inflammatory in murine posttraumatic osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease modifying therapies. Thus, strategies that offer chondroprotective or regenerative capability represent a critical unmet need. Recently, oral consumption of a hydrolyzed type 1 collagen (hCol1) preparation has been reported to reduce pain in human OA and support a positive influence on chondrocyte function. To evaluate the tissue and cellular basis for these effects, we examined the impact of orally administered hCol1 in a model of posttraumatic OA (PTOA). In addition to standard chow, male C57BL/6J mice were provided a daily oral dietary supplement of hCol1 and a meniscal-ligamentous injury was induced on the right knee. At various time points post-injury, hydroxyproline (hProline) assays were performed on blood samples to confirm hCol1 delivery, and joints were harvested for tissue and molecular analyses were performed, including histomorphometry, OARSI and synovial scoring, immunohistochemistry and mRNA expression studies. Confirming ingestion of the supplements, serum hProline levels were elevated in experimental mice administered hCol1. In the hCol1 supplemented mice, chondroprotective effects were observed in injured knee joints, with dose-dependent increases in cartilage area, chondrocyte number and proteoglycan matrix at 3 and 12 weeks post-injury. Preservation of cartilage and increased chondrocyte numbers correlated with reductions in MMP13 protein levels and apoptosis, respectively. Supplemented mice also displayed reduced synovial hyperplasia that paralleled a reduction in Tnf mRNA, suggesting an anti-inflammatory effect. These findings establish that in the context of murine knee PTOA, daily oral consumption of hCol1 is chondroprotective, anti-apoptotic in articular chondrocytes, and anti-inflammatory. While the underlying mechanism driving these effects is yet to be determined, these findings provide the first tissue and cellular level information explaining the already published evidence of symptom relief supported by hCol1 in human knee OA. These results suggest that oral consumption of hCol1 is disease modifying in the context of PTOA.

miR-146a facilitates osteoarthritis by regulating cartilage homeostasis via targeting Camk2d and Ppp3r2

Osteoarthritis (OA), characterized by insufficient extracellular matrix synthesis and cartilage degeneration, is known as an incurable disease because its pathogenesis is poorly elucidated. Thus far, limited information is available regarding the pathophysiological role of microRNAs (miRNAs) in OA. In this study, we investigated the specific function of miR-146a in OA pathophysiology using mouse OA models. We found that the articular cartilage degeneration of miR-146a knockout (KO) mice was alleviated compared with that of the wild-type (WT) mice in spontaneous and instability-induced OA models. We demonstrate that miR-146a aggravated pro-inflammatory cytokines induced suppressing the expression of cartilage matrix-associated genes. We further identified calcium/calmodulin-dependent protein kinase II delta (Camk2d) and protein phosphatase 3, regulatory subunit B, beta isoform (Ppp3r2, also known as calcineurin B, type II) were essential targets of miR-146a in regulating cartilage homeostasis. Moreover, we found that surgical-induced OA mice treated with a miR-146a inhibitor significantly alleviated the destruction of articular cartilage via targeting Camk2d and Ppp3r2. These results suggested that miR-146a has a crucial role in maintaining cartilage homeostasis. MiR-146a inhibition in chondrocytes can be a potential therapeutic strategy to ameliorate OA.

Concentrations of synovial fluid biomarkers and the prediction of knee osteoarthritis 16 years after anterior cruciate ligament injury

OBJECTIVE

To describe the longitudinal patterns of release, and investigate the association between a set of synovial fluid biomarkers at the acute and chronic stage and the development of radiographic knee osteoarthritis (OA) after an anterior cruciate ligament (ACL) injury.

DESIGN

Synovial fluid was aspirated from the acutely ACL-injured knee within the first 2weeks (acute samples), and yearly (chronic samples) up to 7.5 years after injury in 88 subjects (60% men). Non-injured subjects (n = 12) were used as reference group. Aggrecan, cartilage oligomeric matrix protein (COMP), matrix metalloproteinase (MMP)-3 and tissue inhibitor of metalloproteinase (TIMP)-1 in synovial fluid were quantified by immunoassays. The presence of radiographic tibiofemoral (TF) or patellofemoral (PF) OA [Kellgren and Lawrence (K&L) ≥2] was examined with weight-bearing knee radiography 16 years after the ACL injury.

RESULTS

The average acute and chronic SF concentrations of COMP and aggrecan were elevated in comparison with the reference group (P < 0.001). The levels of COMP and aggrecan clearly decreased approximately half a year after the ACL injury, and returned to reference values during the 7.5 years of follow-up. Using logistic regression analysis neither acute nor chronic concentrations of the four biomarkers were associated with the development of radiographic knee OA at the 16 year follow-up.

CONCLUSION

Increased synovial fluid concentrations of aggrecan and COMP was related to knee injury, but acute and chronic synovial fluid concentrations of aggrecan, COMP, MMP-3 and TIMP-1 failed to predict knee OA 16 years after ACL injury.

Coptisine Prevented IL-β-Induced Expression of Inflammatory Mediators in Chondrocytes

Interleukin 1β (IL-1β) is a pleiotropic pro-inflammatory cytokine that plays a critical role in the development of osteoarthritis (OA). Coptisine is an isoquinoline alkaloid extracted from Coptidis rhizome and has been reported to possess anti-inflammatory activity. However, the anti-inflammatory effects of coptisine on interleukin-1 beta (IL-1β)-stimulated chondrocytes have not been reported. Therefore, the aim of this study was to investigate the effects of coptisine on IL-1β-induced inflammation in human articular chondrocytes. Our results showed that coptisine greatly inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2), as well as suppressed the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in human OA chondrocytes induced by IL-1β. It also inhibited the expression of matrix metalloproteinase-3 (MMP-3) and MMP-13 in IL-1β-stimulated human OA chondrocytes. Furthermore, coptisine significantly inhibited the IL-1β-induced NF-kB activation in human OA chondrocytes. Taken together, these data suggest that coptisine inhibits the IL-1β-induced inflammatory response by suppressing the NF-kB signaling pathway. Thus, coptisine may be a potential agent in the treatment of OA.

Corticosterone suppresses IL-1β-induced mPGE2 expression through regulation of the 11β-HSD1 bioactivity of synovial fibroblasts in vitro

The aim of the present study was to investigate the correlation between glucocorticoid activity regulation, prostaglandin E2 (PGE₂) synthesis, and synovial inflammation inhibition activity, through microsomal prostaglandin E synthase-1 (mPGES-1) expression regulated by the glucocorticoid pre-receptor regulator, 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1). In the present study, fibroblast-like synovial cells of rats were studied as a cell model. Cells were stimulated with 10 ng/ml interleukin (IL)-1β for 24 h, and were subsequently, within the next 24 h, treated with or without 10^-6 mmol/l corticosterone alone or with 100 nmol/l PF915275. At the end of the second 24 h, PGE₂ levels in culture supernatants were assayed. Cells were harvested for mRNA evaluation of 11β-HSD1, mPGES-1, IL-1β and tumor necrosis factor (TNF)-α, and protein detection of 11β-HSD1 and mPGES-1 using reverse transcription-qualitative polymerase chain reaction and western blot analysis, respectively. Corticosterone was demonstrated to suppress the mRNA expression levels of inflammatory factors, such as TNF-α and PGE₂, induced by IL-1β in vitro. Simultaneously, expression levels of 11β-HSD1 decreased significantly at the mRNA and protein levels (P<0.05). Cortisol concentration in the medium of the group treated with corticosterone was significantly increased (P<0.05) compared with that of the control group; however, the cortisol concentration was decreased in the medium when the conversion bioactivity of 11β-HSD1 was inhibited by PF915275, while the changes in 11β-HSD1 and mPGES-1 mRNA expression levels and PGE₂ content were reversed in the medium. These results indicated that a significant positive correlation (P<0.01) may exist between mRNA and protein expression levels. To conclude, 11β-HSD1 is a key regulator for the synthesis of mPGES-1 and PGE₂ in the inflammatory synovial cells in vitro, suggesting a potential interference target for osteoarthritis.

Schisandrae Fructus ethanol extract ameliorates inflammatory responses and articular cartilage damage in monosodium iodoacetate-induced osteoarthritis in rats

Schisandrae Fructus, the fruit of Schisandra chinensis (Turcz.) Baill., is widely used in traditional medicine for the treatment of a number of chronic diseases. Although, Schisandrae Fructus was recently reported to attenuate the interleukin (IL)-1β-induced inflammatory response in chondrocytes in vitro, its protective and therapeutic potential against osteoarthritis (OA) in an animal model remains unclear. Therefore, we investigated the effects of the ethanol extract of Schisandrae Fructus (SF) on inflammatory responses and cartilage degradation in a monosodium iodoacetate (MIA)-induced OA rat model. Our results demonstrated that administration with SF had a tendency to attenuate MIA-induced damage of articular cartilage as determined by a histological grade of OA. SF significantly suppressed the production of pro-inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in MIA-induced OA rats. SF also effectively inhibited expression of inducible nitric oxide (NO) synthase and cyclooxygenase-2, thereby inhibiting the release of NO and prostaglandin E₂. In addition, the elevated levels of matrix metalloproteinases-13 and two biomarkers for diagnosis and progression of OA, such as cartilage oligomeric matrix protein and C-telopeptide of type II collagen, were markedly ameliorated by SF administration. These findings indicate that SF could be a potential candidate for the treatment of OA.

A hyaluronic acid-based hydrogel enabling CD44-mediated chondrocyte binding and gapmer oligonucleotide release for modulation of gene expression in osteoarthritis

Hyaluronic acid (HA) is an attractive biomaterial for osteoarthritis (OA) treatment due to inherent functional and compatibility properties as an endogenous knee joint component. In this work, we describe a HA-based hydrogel with the dual functionality of increased CD44-dependent chondrocyte binding and controlled release of gapmer antisense oligonucleotides for unassisted cellular entry and subsequent gene silencing activity. A Schiff base-mediated gelation method was used to produce a panel of hydrogels varying in the aldehyde-modified HA (900kDa) to chitosan ratios (3:7, 5:5 and 7:3) for identifying designs displaying optimal engagement of OA patient-derived CD44-expressing chondrocytes. Correlation was found between cell binding and CD44 expression, with maximal binding exhibited at a HA/chitosan ratio of 7:3, that was 181% higher than CD44-negative MCF-7 cell control cells. Transfection agent-free uptake into OA chondrocytes of fluorescent 13-mer DNA oligonucleotides with a flanked locked nucleic acid (LNA) gapmer design, in contrast to naked siRNA, was demonstrated by confocal and flow cytometric analysis. A sustained and complete release over 5days was found with the 7:3 hydrogel, in contrast, the 5:5 and 3:7 hydrogel released 60% and 43% of loaded gapmers, respectively over the same period. A COX-2-specific gapmer designed with maximal chondrocyte gene silencing (~70% silencing efficiency at 500nM compared with a mismatch gapmer sequence) resulted in effective COX-2 silencing over 14days in hydrogels seeded with OA chondrocytes, with significant difference exhibited between day 3 and 10. This work introduces a novel HA-based CD44-mediated cellular binding and gapmer controlled release platform to modulate cellular gene expression.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.

Cartilage oligomeric matrix protein neoepitope in the synovial fluid of horses with acute lameness: A new biomarker for the early stages of osteoarthritis

Background

Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking.

Objectives

We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neoepitope in the synovial fluid from the joints of healthy horses and those with different stages of OA.

Study design

In vitro quantitative proteomics and assay development with application in synovial fluids samples obtained from biobanks of well‐characterised horses.

Methods

Articular cartilage explants were incubated with or without interleukin‐1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid was obtained from either normal joints (n = 15) or joints causing lameness (n = 17) or with structural OA lesions (n = 7) and analysed for concentrations of the COMP neoepitope using a custom‐developed inhibition enzyme‐linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neoepitopes.

Results

Semitryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neoepitope of the N‐terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition ELISA was developed to quantify the COMP neoepitope in synovial fluid. The mean concentration of the COMP neoepitope significantly increased in the synovial fluid from the joints responsible for acute lameness compared with normal joints and the joints of chronically lame horses and in joints with chronic structural OA. Immunolabelling for the COMP neoepitope revealed a pericellular staining in the interleukin‐1β‐stimulated explants.

Main limitations

The ELISA is based on polyclonal antisera rather than a monoclonal antibody.

Conclusions

The increase in the COMP neoepitope in the synovial fluid from horses with acute lameness suggests that this neoepitope has the potential to be a unique candidate biomarker for the early molecular changes in articular cartilage associated with OA.

The involvement and possible mechanism of NR4A1 in chondrocyte apoptosis during osteoarthritis

Osteoarthritis (OA) is a joint disease caused by the breakdown of joint cartilage and underlying bone, and places great burdens to daily life of patients. Nuclear orphan receptor nuclear receptor subfamily 4, group A, member 1 (NR4A1) is vital for cell apoptosis, but little is known about its role in OA. This study aims to reveal the expression and function of NR4A1 during OA chondrocyte apoptosis. NR4A1 expression by qRT-PCR and western blot, and chondrocyte apoptosis by TUNEL assay were detected in normal and OA joint cartilage. NR4A1 was located in cartilage sections by immunohistofluorescence. Chondrocytes from normal joint cartilage were cultured in vitro for interleukin 6 (IL6) or tumor necrosis factor (TNF) treatment and si-NR4A1 transfection, after which the possible mechanism involving NR4A1 was analyzed. Results showed that NR4A1 expression and chondrocyte apoptosis were significantly elevated in OA cartilage (P < 0.05 and P < 0.01). NR4A1 was located in nuclei of normal cartilage chondrocytes, but was translocated to mitochondria and co-located with B-cell lymphoma 2 in OA chondrocytes. NR4A1 expression in cultured chondrocytes could be promoted by both IL6 and TNF treatment. si-NR4A1 partly reduced TNF-induced cell apoptosis. Inhibiting p38 by SB203580 could decrease TNF-induced NR4A1 to some extent, while inhibiting JNK could not. So NR4A1 is likely to facilitate OA chondrocyte apoptosis, which is associated with p38 MAPK and mitochondrial apoptosis pathway. This study provides a potential therapeutic target for OA treatment and offers information for regulatory mechanisms in OA.

Wnt7a Inhibits IL-1β Induced Catabolic Gene Expression and Prevents Articular Cartilage Damage in Experimental Osteoarthritis

Wnt7a is a protein that plays a critical role in skeletal development. However, its effect on cartilage homeostasis under pathological conditions is not known. In this study, we found a unique inverse correlation between Wnt7a gene expression and that of MMP and IL-1β in individual human OA cartilage specimens. Upon ectopic expression in primary human articular chondrocytes, Wnt7a inhibited IL-1β-induced MMP and iNOS gene expression. Western blot analysis indicated that Wnt7a induced both canonical Wnt signaling and NFAT and Akt non-canonical signaling. Interestingly, inhibiting the canonical and Akt pathway did not affect Wnt7a activity. However, inhibiting the NFAT pathway impaired Wnt7a’s ability to inhibit MMP expression, suggesting that Wnt7a requires NFAT signaling to exert this function. In vivo, intraarticular injection of lentiviral Wnt7a strongly attenuated articular cartilage damage induced by destabilization of the medial meniscus (DMM) OA-inducing surgery in mice. Consistently, Wnt7a also inhibited the progressive increase of joint MMP activity in DMM animals. These results indicate that Wnt7a signaling inhibits inflammatory stimuli-induced catabolic gene expression in human articular chondrocytes and is sufficient to attenuate MMP activities and promote joint cartilage integrity in mouse experimental OA, demonstrating a novel effect of Wnt7a on regulating OA pathogenesis.