Target For Osteoarthritis Therapy Research Articles

MIA/CD-RAP Regulates MMP13 and Is a Potential New Disease-Modifying Target for Osteoarthritis Therapy.

Melanoma inhibitory activity/cartilage-derived retinoicacid-sensitive protein (MIA/CD-RAP) is a protein expressed and secreted by chondrocytes and cartilaginous tissues. MIA/CD-RAP-deficient mice develop milder osteoarthritis than wildtype mice. In this study, we investigated MIA/CD-RAP downstream targets to explain this reduced disease development. As a possible mediator, we could detect matrix metalloproteinase 13 (MMP13), and the influence of MIA/CD-RAP on MMP13 regulation was analyzed in vitro using SW1353 chondrosarcoma cells and primary chondrocytes. The femoral head cartilage of WT and MIA/CD-RAP -/- mice were cultured ex vivo to further investigate MMP13 activity. Finally, osteoarthritis was surgically induced via DMM in C57BL/6 mice, and the animals were treated with an MIA/CD-RAP inhibitory peptide by subcutaneously implanted pellets. MMP13 was regulated by MIA/CD-RAP in SW1353 cells, and MIA/CD-RAP -/- murine chondrocytes showed less expression of MMP13. Further, IL-1β-treated MIA/CD-RAP -/- chondrocytes displayed less MMP13 expression and activity. Additionally, MIA/CD-RAP-deficient ex vivo cultured cartilage explants showed less MMP13 activity as well as reduced cartilage degradation. The mice treated with the MIA/CD-RAP inhibitory peptide showed less osteoarthritis development. Our findings revealed MIA/CD-RAP as a new regulator of MMP13 and highlighted its role as a potential new target for osteoarthritis therapy.

Inhibition of nuclear receptor ROR\u03b1 attenuates cartilage damage in osteoarthritis by modulating IL-6/STAT3 pathway

Osteoarthritis (OA) is characterized by cartilage destruction, chronic inflammation, and local pain. Evidence showed that retinoic acid receptor-related orphan receptor-α (RORα) is crucial in cartilage development and OA pathogenesis. Here, we investigated the role and molecular mechanism of RORα, an important member of the nuclear receptor family, in regulating the development of OA pathologic features. Investigation into clinical cartilage specimens showed that RORα expression level is positively correlated with the severity of OA and cartilage damage. In an in vivo OA model induced by anterior crucial ligament transaction, intra-articular injection of si-Rora adenovirus reversed the cartilage damage. The expression of cartilage matrix components type II collagen and aggrecan were elevated upon RORα blockade. RNA-seq data suggested that the IL-6/STAT3 pathway is significantly downregulated, manifesting the reduced expression level of both IL-6 and phosphorylated STAT3. RORα exerted its effect on IL-6/STAT3 signaling in two different ways, including interaction with STAT3 and IL-6 promoter. Taken together, our findings indicated the pivotal role of the RORα/IL-6/STAT3 axis in OA progression and confirmed that RORα blockade improved the matrix catabolism in OA chondrocytes. These results may provide a potential treatment target in OA therapy.

Isovitexin Depresses Osteoarthritis Progression via the Nrf2/NF-κB Pathway: An in vitro Study.

PurposeOsteoarthritis (OA) is a multifactorial joint disease and inflammatory processes contribute to joint destruction. Isovitexin (IVX) is a flavone component found in passion flower, Cannabis and, and the palm that is known for its anti-inflammatory properties.Materials and MethodsThis study investigated in vitro the role and underlying mechanism used by IVX in its regulation of OA development. Effects of IVX on the viability of chondrocytes were measured by CCK-8 assays. The phenotypes of extracellular matrix (ECM) degeneration and inflammation were measured by qPCR, Western blot, and ELISA; and NF-κB pathway was detected by immunofluorescence and Western blot. Molecular docking was applied to predict the interacting protein of IVX, while Nrf2 was knocked down by siRNAs to confirm its role.ResultsWe demonstrated that IVX suppressed ECM degeneration and suppressed pro-inflammatory factors in IL-1β-treated chondrocytes. Additionally, IVX impact on NF-κB signaling in IL-1β-exposed chondrocytic cells; Mechanistically, it was also demonstrated in molecular docking and knock down studies that IVX might bind to Nrf2 to suppress NF-κB pathway.ConclusionOur data suggest that IVX halts OA disease advancement through the Nrf2/NF-κB axis, suggesting a possibility of IVX as a target for OA therapy.

Downregulation of MicroRNA-495 Alleviates IL-1β Responses among Chondrocytes by Preventing SOX9 Reduction.

PurposeOur previous work demonstrated that miRNA-495 targets SOX9 to inhibit chondrogenesis of mesenchymal stem cells. In this study, we aimed to investigate whether miRNA-495-mediated SOX9 regulation could be a novel therapeutic target for osteoarthritis (OA) using an in vitro cell culture model.Materials and MethodsAn in vitro model mimicking the OA environment was established using TC28a2 normal human chondrocyte cells. Interleukin-1β (IL-1β, 10 ng/mL) was utilized to induce inflammation-related changes in TC28a2 cells. Safranin O staining and glycosaminoglycan assay were used to detect changes in proteoglycans among TC28a2 cells. Expression levels of COX-2, ADAMTS5, MMP13, SOX9, CCL4, and COL2A1 were examined by qRT-PCR and/or Western blotting. Immunohistochemistry was performed to detect SOX9 and CCL4 proteins in human cartilage tissues obtained from patients with OA.ResultsmiRNA-495 was upregulated in IL-1β-treated TC28a2 cells and chondrocytes from damaged cartilage tissues of patients with OA. Anti-miR-495 abolished the effect of IL-1β in TC28a2 cells and rescued the protein levels of SOX9 and COL2A1, which were reduced by IL-1β. SOX9 was downregulated in the damaged cartilage tissues of patients with OA, and knockdown of SOX9 abolished the effect of anti-miR-495 on IL-1β-treated TC28a2 cells.ConclusionWe demonstrated that inhibition of miRNA-495 alleviates IL-1β-induced inflammatory responses in chondrocytes by rescuing SOX9 expression. Accordingly, miRNA-495 could be a potential novel target for OA therapy, and the application of anti-miR-495 to chondrocytes could be a therapeutic strategy for treating OA.

Jumonji domain containing-3 (JMJD3)inhibition attenuatesIL-1β-inducedchondrocytes damage in vitro and protects osteoarthritis cartilage in vivo.

This study aimed to explore the effects and relative mechanism of JMJD3 on knee osteoarthritis (OA). In this study, we first analyzed the expression of JMJD3 in OA cartilage using western blot and immunohistochemistry. In an in vitro study, the effects of GSK-J4, JMJD3 inhibitor, on ATDC-5 chondrocytes were evaluated by CCK-8 assay. Real-time PCR and western blot were used to examine the inhibitory effect of GSK-J4 on the inflammation and ECM degradation of chondrocytes. NF-κB p65 phosphorylation and nuclear translocation were measured by western blot and immunofluorescence. In the animal study, twenty mice were randomized into four experimental groups: sham group, DMM-induced OA + DMSO group, OA + low-dose GSK-J4 group, and OA + high-dose GSK-J4 group. After the treatment, hematoxylin-eosin and safranin O/fast green staining were used to evaluate cartilage degradation of knee joint, with OARSI scores for quantitative assessment of cartilage damage. Our results revealed that JMJD3 was overexpressed in OA cartilage and GSK-J4 could suppress the IL-1β-induced production of pro-inflammatory cytokines and catabolic enzymes, including IL-6, IL-8, MMP-9 and ADAMTS-5. Consistent with these findings, GSK-J4 could inhibit IL-1β-induced degradation of collagen II and aggrecan. Mechanistically, GSK-J4 dramatically suppressed IL-1β-stimulated NF-κB signal pathway activation. In vivo, GSK-J4 prevented cartilage damage in mouse DMM-induced OA model. This study elucidates the important role of JMJD3 in cartilage degeneration in OA, and our results indicate that JDJM3 may become a novel therapeutic target in OA therapy.

Long Non-coding RNA HOTTIP Promotes CCL3 Expression and Induces Cartilage Degradation by Sponging miR-455-3p.

Long non-coding RNAs (lncRNAs) play pivotal roles in diseases such as osteoarthritis (OA). However, knowledge of the biological roles of lncRNAs is limited in OA. We aimed to explore the biological function and molecular mechanism of HOTTIP in chondrogenesis and cartilage degradation. We used the human mesenchymal stem cell (hMSC) model of chondrogenesis, in parallel with, tissue biopsies from normal and OA cartilage to detect HOTTIP, CCL3, and miR-455-3p expression in vitro. Biological interactions between HOTTIP and miR-455-3p were determined by RNA silencing and overexpression in vitro. We evaluated the effect of HOTTIP on chondrogenesis and degeneration, and its regulation of miR-455-3p via competing endogenous RNA (ceRNA). Our in vitro ceRNA findings were further confirmed within animal models in vivo. Mechanisms of ceRNAs were determined by bioinformatic analysis, a luciferase reporter system, RNA pull-down, and RNA immunoprecipitation (RIP) assays. We found reduced miR-455-3p expression and significantly upregulated lncRNA HOTTIP and CCL3 expression in OA cartilage tissues and chondrocytes. The expression of HOTTIP and CCL3 was increased in chondrocytes treated with interleukin-1β (IL-1β) in vitro. Knockdown of HOTTIP promoted cartilage-specific gene expression and suppressed CCL3. Conversely, HOTTIP overexpression reduced cartilage-specific genes and increased CCL3. Notably, HOTTIP negatively regulated miR-455-3p and increased CCL3 levels in human primary chondrocytes. Mechanistic investigations indicated that HOTTIP functioned as ceRNA for miR-455-3p enhanced CCL3 expression. Taken together, the ceRNA regulatory network of HOTTIP/miR-455-3p/CCL3 plays a critical role in OA pathogenesis and suggests HOTTIP is a potential target in OA therapy.

The Function of PPARγ/AMPK/SIRT-1 Pathway in Inflammatory Response of Human Articular Chondrocytes Stimulated by Advanced Glycation End Products.

Accumulation of advanced glycation end products (AGEs) in the articular cartilage is a major risk factor for osteoarthritis (OA). To determine the mechanistic basis of AGE action in OA, we treated human articular chondrocytes with AGEs, and found that they not only up-regulated the pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, but also inhibited AMP-activated protein kinase (AMPK) phosphorylation and decreased sirtuin 1 (SIRT-1) levels in a concentration- and time-dependent manner. Pioglitazone, a peroxisome proliferator-activated receptor-γ (PPARγ) agonist restored the inhibited AMPK and SIRT-1 by AGEs. Pre-treatment of the cells with the agonists or antagonists of AMPK and SIRT-1 respectively abolished and augmented the inflammatory state induced by AGEs. Furthermore, AMPK agonist also restored the levels of SIRT-1 in the AGE-stimulated chondrocytes. Our findings indicate AGEs induce an inflammatory response in human articular chondrocytes via the PPARγ/AMPK/SIRT-1 pathway, which is therefore a potential target in OA therapy.

MicroRNA‑31 promotes chondrocyte proliferation by targeting C‑X‑C motif chemokine ligand 12.

The present study aimed to investigate the biological function and underlying molecular mechanisms of miR-31 in osteoarthritis (OA). Reverse transcription-quantitative polymerase chain reaction was used to detect miR-31 expression, and it was found that miR-31 was downregulated in the cartilage tissues of OA patients. microRNA.org was used to predict the gene targets of miR-31, and dual luciferase reporter assays were used to verify that C-X-C motif chemokine ligand 12 (CXCL12) was a direct target of miR-31. The human chondrocyte cell line CHON-001 was used to perform MTT and cell migration assays. Western blotting was used to measure the protein expression of CXCL12, type I collagen and aggrecan. The results suggested that CXCL12 was a target of miR-31, and the expression of CXCL12 was negatively regulated by miR-31 in CHON-001 cells. miR-31 increased CHON-001 cell viability and migration, as well as the expression of type I collagen and aggrecan. Furthermore, the overexpression of CXCL12 eliminated the effects of miR-31 mimics on CHON-001 cells. In conclusion, the data indicated that miR-31 promoted chondrocyte viability and migration by directly targeting CXCL12, which provided evidence for CXCL12 as a potential target in OA therapy.

CircRNA.33186 Contributes to the Pathogenesis of Osteoarthritis by Sponging miR-127-5p.

Osteoarthritis (OA), the most prevalent age-related joint disorder, is characterized by chronic inflammation, progressive articular cartilage destruction, and subchondral bone sclerosis. Accumulating evidences indicate that circular RNAs (circRNAs) play a critical role in various diseases, but the function of circRNAs in OA remains largely unknown. Here we showed that circRNA.33186 was significantly upregulated in IL-1β)-treated chondrocytes and in cartilage tissues of a destabilized medial meniscus (DMM)-induced OA mouse model. Knockdown of circRNA.33186 increased anabolic factor (type II collagen) expression and decreased catabolic factor (MMP-13) expression. Knockdown of circRNA.33186 also promoted proliferation and inhibited apoptosis in IL-1β-treated chondrocytes. Silencing of circRNA.33186 invivo markedly alleviated DMM-induced OA. Mechanistic study showed that circRNA.33186 directly binds to and inhibits miR-127-5p, thereby increasing MMP-13 expression, and contributes to OA pathogenesis. Taken together, our findings demonstrated a fundamental role of circRNA.33186 in OA progression and provide a potential drug target in OA therapy.

Circular RNA Related to the Chondrocyte ECM Regulates MMP13 Expression by Functioning as a MiR-136 'Sponge' in Human Cartilage Degradation.

Circular RNAs (circRNAs) are involved in the development of various diseases, but there is little knowledge of circRNAs in osteoarthritis (OA). The aim of study was to identify circRNA expression in articular cartilage and to explore the function of chondrocyte extracellular matrix (ECM)-related circRNAs (circRNA-CER) in cartilage. To identify circRNAs that are specifically expressed in cartilage, we compared the expression of circRNAs in OA cartilage with that in normal cartilage. Bioinformatics was employed to predict the interaction of circRNAs and mRNAs in cartilage. Loss-of-function and rescue experiments for circRNA-CER were performed in vitro. A total of 71 circRNAs were differentially expressed in OA and normal cartilage. CircRNA-CER expression increased with interleukin-1 and tumor necrosis factor levels in chondrocytes. Silencing of circRNA-CER using small interfering RNA suppressed MMP13 expression and increased ECM formation. CircRNA-CER could compete for miR-136 with MMP13. Our results demonstrated that circRNA-CER regulated MMP13 expression by functioning as a competing endogenous RNA (ceRNA) and participated in the process of chondrocyte ECM degradation. We propose that circRNA-CER could be used as a potential target in OA therapy.

MicroRNA-26a-5p regulates the expression of inducible nitric oxide synthase via activation of NF-κB pathway in human osteoarthritis chondrocytes

Inducible nitric oxide synthase (iNOS) expression is associated with the pathogenesis of osteoarthritis (OA). This study was undertaken to investigate whether interleukin-1β (IL-1β)-mediated induction of iNOS can be regulated by microRNA-26a-5p (hsa-miR-26a-5p) in OA. Bioinformatics approaches show that 3′UTR of iNOS mRNA contained the ‘seed-matched-sequence’ for hsa-miR-26a-5p. IL-1β-induced expression of iNOS correlated with the down-regulation of miR-26a-5p in human OA chondrocytes. hsa-miR-26a-5p directly suppressed the luciferase activity of 3′UTR-iNOS reporter clone. Transfection with pre-miR-26a-5p induced marked silencing of iNOS expression. Activation of NF-κB pathway down-regulated the expression of hsa-miR-26a-5p and induced iNOS expression. In short, this is the first report that shows hsa-miR-26a-5p is a direct regulator of iNOS expression in human chondrocytes. hsa-miR-26a-5p may be an important regulator of human cartilage homeostasis and a new target for OA therapy.

Long noncoding RNA related to cartilage injury promotes chondrocyte extracellular matrix degradation in osteoarthritis.

Long noncoding RNAs (lncRNAs) play crucial regulatory roles in diverse biologic processes, but knowledge of lncRNAs in osteoarthritis (OA) is limited. The aim of this study was to identify lncRNA expression in articular cartilage and to explore the function of cartilage injury-related lncRNAs (lncRNA-CIR) in OA. To identify lncRNAs specifically expressed in OA cartilage, we compared the expression of lncRNAs in OA cartilage with that in normal cartilage using microarray and quantitative polymerase chain reaction (qPCR) analyses. In OA cartilage, lncRNA-CIR was specifically, differentially, and highly expressed. The function of lncRNA-CIR was determined by silencing and overexpression in vitro. Extracellular matrix (ECM)-related molecules were detected by qPCR, Western blot, and immunofluorescence analyses. Up to 152 lncRNAs were found to be differentially expressed (>8-fold) in OA and normal cartilage (82 lncRNAs more highly expressed and 70 less highly expressed in OA cartilage than in normal cartilage). A specific differentially expressed lncRNA-CIR was selected according to the results of the higher expression in OA cartilage and OA chondrocytes. The expression of lncRNA-CIR increased in chondrocytes with in vitro treatment with interleukin-1β and tumor necrosis factor α. Silencing of lncRNA-CIR by small interfering RNA promoted the formation of collagen and aggrecan and reduced the expression of matrix-degrading enzymes, such as MMP13 and ADAMTS5. The expression of collagen and aggrecan was reduced, whereas the expression of matrix-degrading enzymes was increased, after overexpression of lncRNA-CIR. The results indicate that lncRNA-CIR contributes to ECM degradation and plays a key role in the pathogenesis of OA. We propose that lncRNA-CIR could be used as a potential target in OA therapy.

SAT0330 Sclerostin concentrations in plasma and synovial fluid inversely correlate with disease severity in knee osteoarthritis

BackgroundOsteoarthritis (OA) is characterized by the progressive destruction of articular cartilage with joint space narrowing and osteophyte formation (1). Although the etiology and pathogenesis of OA remain poorly understood, recent...

Anti-angiogenic action of chondroitin sulfate: a novel target for osteoarthritis therapy

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S271 changed to serum-free labeling medium containing also chondrogenic inducers. Expression of cartilage specific genes such as type I and II collagen and proteoglycans were used to verify the chondrogenicity of hBMSCs. Proteins in the CM harvested on day 2 and 14 of differentiation were precipitated and combined at a 1:1 ratio. Each mixture was then separated by 1D-SDS-PAGE and subjected to in-gel trypsin digestion using an automatic digester. The resulting peptide mixtures were analyzed by nanoscale liquid chromatography coupled on-line to an LTQ-Orbitrap XLmass spectrometer and quantified using the MaxQuant software. Results: A progressive increase of type II collagen, agreccan and chondroitin-6-sulfate during the course of 14 days of differentiation was detected by immunohistochemical assays, suggesting that hMSCs maintain their chondrogenic capacity in SILAC medium. Using the metabolic labeling strategy, we compared the secretomes at two different time points of chondrogenesis. More than 1000 proteins were identified with high confidence parameters. 20% of them were previously known ECM-related proteins. Among these, 34 exhibited a significant modulation of their levels during the process of chondrogenesis, including cartilage ECM proteins such as COMP, lumican, prolargin, fibromodulin and matrix gla protein (MGP), which could be involved in the organization and/or stabilization of cartilage matrix. All these proteins were increased at day 14 of chondrogenesis. Finally, pentraxin-related protein (PTX3), which plays a role in the regulation of inflammatory response, resulted decreased at day 14. Conclusions: This study was focused on characterizing the specific modulations in the secretome of hBMSCs undergoing chondrogenesis using the SILAC method. The identification and quantification of these secreted proteins provide information about the changes in the ECM synthesis during the differentiation process. Moreover, these findings enhance our knowledge of extracellular regulation of this process and allow the identification of extracellular markers of chondrogenesis, which might have potential value in cartilage regeneration strategies. 527 ANTI-ANGIOGENIC ACTION OF CHONDROITIN SULFATE: A NOVEL TARGET FOR OSTEOARTHRITIS THERAPY V. Calamia y, J. Mateos y, P. Fernandez-Puente y, L. Lourido y, B. Rocha y, C. Fernandez-Costa y, E. Montell z, J. Verges z, C. Ruiz-Romero y, F.J. Blanco y. yOsteoarticular and Aging Res. Lab., Proteomics Unit-Associated Node to ProteoRed-ISCIII, INIBIC-CHUAC, A Coruna, Spain; z Pre-clinical R&D Area, Pharma Sci. Div., Bioiberica, Barcelona, Spain Purpose: Recent works by our group provide evidences of the usefulness of proteomics techniques for antiosteoarthritis (OA) drug screening. The aim of this study is to identify protein markers for monitoring chondroitin sulfate (CS) treatment by OA chondrocytes secretome analysis using the iTRAQ technique. Methods:Human articular chondrocytes (HACs) released from three OA cartilages were cultured in DMEM supplemented with antibiotics and 10% FBS. At confluence, OA chondrocytes were treated with 200 mg/mL of CS (100% purity, bovine origin). 48 hours later, conditioned media were collected and their proteins were concentrated and quantified. Trypsin digestion and labeling with isobaric tags using iTRAQ reagents were performed. Then, peptides from the two conditions (untreated,

PPARdelta as a novel target for osteoarthritis therapy

PPARdelta as a novel target for osteoarthritis therapy

MicroRNA-199a* regulates the expression of cyclooxygenase-2 in human chondrocytes

ObjectiveCyclooxygenase-2 (COX-2) expression is associated with the pathogenesis of chronic inflammation and pain in osteoarthritis (OA). A study was undertaken to determine whether interleukin-1β (IL-1β)-mediated induction of COX-2 can be...

To Seek Shelter from the Wnt in Osteoarthritis? Wnt-Signaling as a Target for Osteoarthritis Therapy

Recent evidence from animal experiments and clinical samples points at a role for Wnt-signaling in osteoarthritis (OA) pathology. These pathways are key inducers and regulators of joint development, and are involved in formation of bone, cartilage and also synovium. Disregulation of members from this pathways have been described in OA. This makes the Wnt-family of proteins and signaling pathways an attractive target for therapy. Although knowledge is increasing rapidly it is still a challenge to decide on the best approach in targeting Wnt signaling. Activation of the canonical signaling pathway, which features intra-cellular accumulation of beta-catenin, is most often implicated in recent studies in OA pathology, in experimental OA and spondyloarthritis. However, direct targeting of beta-catenin is anticipated to be too hazardous, because of its importance for the maintenance of stability of articular chondrocyte phenotype and because of its proven role in carcinogenesis. A more attractive approach will be identifying the misexpression of specific Wnt-proteins or their inhibitors in various tissues that are important in OA, bone, cartilage and synovium, to point out targets for therapy. For example, recently it was shown that Wnt16 is strongly upregulated in cartilage after injury and in synovium in experimental OA, and the expression of this canonical Wnt may be responsible for OA-like changes. Alternatively, identifying more down stream Wnt signaling effector molecules, like WISP-1, for more specific therapy promises to be a safer and more efficient approach to find a treatment for this disease that heavily constrains millions of people each year.

Use of Nurse Practitioners and Physician Extenders in Rheumatology: A Western North Carolina Perspective

### Objective Cyclooxygenase-2 (COX-2) expression is associated with the pathogenesis of chronic inflammation and pain in osteoarthritis (OA). A study was undertaken to determine whether interleukin-1β (IL-1β)-mediated induction of COX-2 can be regulated by microRNAs (miRNAs) in OA. ### Methods Human chondrocytes were stimulated with IL-1β in vitro. Total RNA was prepared using Trizol reagent. Gene expression was quantified using TaqMan Assays and miRNA targets were identified using bioinformatics. Transfection with reporter construct and premiRNA and antimiRNA was employed to verify suppression of target mRNA. Expression of COX-2 proteins was determined by immunoblotting. The role of activated p38-MAPKs was evaluated using specific inhibitor. ### Results The 3′UTR of COX-2 mRNA contained the 'seed-matched' sequences for miR-199a\* and miR-101_3. Increased expression of COX-2 correlated with the downregulation of miR-199a\* and miR-101_3 in IL-1β-stimulated normal and OA chondrocytes. miR-199a\* directly suppressed the luciferase activity of a COX-2 3′UTR reporter construct and inhibited the IL-1β-induced expression of COX-2 protein in OA chondrocytes. Modulation of miR-199a\* expression also caused significant inhibition of IL-1β-induced upregulation of mPGES1 and prostaglandin E~2~ production in OA chondrocytes. Activation of p38-MAPK downregulated the expression of miR-199a\* and induced COX-2 expression. Treatment with antimiR-101_3 increased COX-2 expression in IL-1β-stimulated chondrocytes, but overexpression of miR-101_3 had no significant effect on COX-2 protein expression. ### Conclusions miR-199a\* is a direct regulator of COX-2 expression in OA chondrocytes. IL-1β-induced activation of p38-MAPK correlates inversely with miR199a\* expression levels. miR-199a\* may be an important regulator of human cartilage homeostasis and a new target for OA therapy.

Up-regulation of microsomal prostaglandin E synthase 1 in osteoarthritic human cartilage: critical roles of the ERK-1/2 and p38 signaling pathways.

Microsomal prostaglandin E synthase 1 (mPGES-1) is the final enzyme of the cascade that produces prostaglandin E(2) (PGE(2)), a key actor in arthritis. To study mPGES-1 synthesis in human cartilage and its regulation by interleukin-1beta (IL-1beta), we used human cartilage and an immortalized human chondrocyte cell line. Furthermore, we investigated the signaling pathways involved in mPGES-1 expression. We used real-time quantitative reverse transcription-polymerase chain reaction, Northern blotting, and Western blotting to measure mPGES-1 messenger RNA (mRNA) and protein expression in human chondrocytes. PGE(2) production was measured by enzyme-linked immunosorbent assay. Cartilage specimens from osteoarthritis (OA) patients contained far greater amounts of mPGES-1 and cyclooxygenase 2 (COX-2) mRNA than did normal cartilage. Incubation with IL-1beta markedly increased mPGES-1 mRNA and protein in a dose-dependent and time-dependent manner, in parallel with an increase in PGE(2) levels. Both PD98059, an ERK pathway inhibitor, and SB203580, a p38alpha/beta MAPK inhibitor, abolished the increases in mPGES-1 mRNA and protein in response to IL-1beta. The specific p38alpha MAPK inhibitor SC906 suppressed IL-1beta-induced COX-2 expression but not IL-1beta-induced mPGES-1 expression, suggesting preferential involvement of p38beta MAPK in IL-1beta-induced mPGES-1 expression. This study is the first to show that mPGES-1 is stimulated in human chondrocytes by the proinflammatory cytokine IL-1beta via activation of both ERK-1/2 and p38 MAPK in an isoform-specific manner. We postulate that mPGES-1 may be a novel target for OA therapy.

AGEing and osteoarthritis: a different perspective.

Across the world, osteoarthritis is the most commonly occurring musculoskeletal disease of the elderly, affecting more than 25% of the population older than 60 years of age. By far the single greatest risk factor for the development of osteoarthritis is age, but a mechanism to explain this relation has not yet been identified. If such a mechanism is identified, this potentially also provides a novel target for osteoarthritis therapy. The identification of new therapeutic targets is of utmost importance, because a disease-modifying treatment for osteoarthritis is not available and, because of the graying of the population, the number of patients with osteoarthritis will continue to increase, which will pose an enormous social and economic burden on society. Advanced glycation end products accumulate in human articular cartilage with increasing age, and affect biomechanical, biochemical, and cellular characteristics of the tissue. As an illustration, accumulation of advanced glycation end products increase cartilage stiffness and brittleness while decreasing the synthesis and degradation of cartilage matrix constituents. Articular cartilage becomes more prone to damage, and thus osteoarthritis, at elevated concentrations of advanced glycation end products. The reviewed literature demonstrates that the age-related accumulation of advanced glycation end products in articular cartilage may provide a molecular mechanism capable of (at least in part) explaining the age-related increase in the incidence of osteoarthritis. This conclusion paves the way for new strategies to prevent or treat osteoarthritis via inhibition and/or reversal of this process.