Effect of osteopontin on the mRNA expression of ADAMTS4 and ADAMTS5 in chondrocytes from patients with knee osteoarthritis

The Nrf2/HMGB1/NF-κB axis modulates chondrocyte apoptosis and extracellular matrix degradation in osteoarthritis

Osteoarthritis (OA) is a degenerative or posttraumatic condition of the joints. In OA chondrocytes, Nrf2 functions as a stress response regulator with antioxidant and anti-inflammatory effects. This study aims to investigate the role of Nrf2 and its downstream pathway in the development of osteoarthritis. IL-1β treatment suppresses Nrf2, aggrecan, and COL2A1 levels and cell viability but promotes apoptosis in chondrocytes. IL-1β stimulation induces cell apoptosis, upregulates the mRNA expression of inflammatory factors, decreases aggrecan, COL2A1, and Bcl-2 levels but increases ADAMTS-5, ADAMTS-4, MMP13, cleaved caspase 3, and BAX levels, and promotes p65 phosphorylation. Nrf2 overexpression exerts opposite effects on IL-1β-treated chondrocytes, as demonstrated by the significant attenuation of IL-1β-induced changes in chondrocytes. By binding to the HMGB1 promoter region, Nrf2 suppresses HMGB1 expression. Similar to Nrf2 overexpression, HMGB1 knockdown also attenuates IL-1β-induced changes in chondrocytes. Notably, under IL-1β stimulation, the effects of Nrf2 overexpression or tert-butylhydroquinone (TBHQ, an activator of Nrf2) on apoptosis, inflammatory factor expression, ECM and apoptosis, and NF-κB pathway activity in chondrocytes are remarkably reversed by HMGB1 overexpression or recombinant HMGB1 (rHMGB1). Similarly, rHMGB1 could partially counteract the curative effect of TBHQ on OA damage in mice. In OA cartilage tissue samples, the level of Nrf2 is lower, while the levels of HMGB1, apoptotic, and inflammatory factors are increased compared to normal cartilage tissue samples. In conclusion, for the first time, the Nrf2/HMGB1 axis was found to modulate apoptosis, ECM degradation, inflammation and activation of NF-κB signaling in chondrocytes and OA mice.

Osteopontin: A Bone-Derived Protein Involved in Rheumatoid Arthritis and Osteoarthritis Immunopathology

Osteopontin (OPN) is a bone-derived phosphoglycoprotein related to physiological and pathological mechanisms that nowadays has gained relevance due to its role in the immune system response to chronic degenerative diseases, including rheumatoid arthritis (RA) and osteoarthritis (OA). OPN is an extracellular matrix (ECM) glycoprotein that plays a critical role in bone remodeling. Therefore, it is an effector molecule that promotes joint and cartilage destruction observed in clinical studies, in vitro assays, and animal models of RA and OA. Since OPN undergoes multiple modifications, including posttranslational changes, proteolytic cleavage, and binding to a wide range of receptors, the mechanisms by which it produces its effects, in some cases, remain unclear. Although there is strong evidence that OPN contributes significantly to the immunopathology of RA and OA when considering it as a common denominator molecule, some experimental trial results argue for its protective role in rheumatic diseases. Elucidating in detail OPN involvement in bone and cartilage degeneration is of interest to the field of rheumatology. This review aims to provide evidence of the OPN’s multifaceted role in promoting joint and cartilage destruction and propose it as a common denominator of AR and OA immunopathology.

Protective effects of equol on the cartilage and subchondral bone in ovariectomized rats with osteoarthritis

Objectives

This study aimed to determine the therapeutic effect of equol (EQ) on osteoporotic osteoarthritis (OP OA).

Materials and Methods

Thirty-six 12-week-old female Sprague-Dawley rats were randomly divided into sham group, OP OA group, and EQ group (n=12). OP OA was induced by anterior cruciate ligament transection (ACLT) combined with ovariectomy (OVX). EQ was orally administrated (10 μg/g/day) after the operation for 12 weeks. The efficacy was evaluated by gross pathology and histopathologic evaluation. The underlying mechanism was investigated by immunohistochemical analysis, micro-computed tomography (micro-CT) scanning, and tartrate-resistant acid phosphatase (TRAP) staining.

Results

EQ effectively retarded cartilage degeneration, decreased the levels of matrix metalloproteinases-13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), nuclear factor-kappa B P65 (NF-κB P65) and caspase-3, and increased the levels of collagen type II (Col-II), Col-I, aggrecan (AGG), and inhibitor of NF-κB α (IκBα) in the cartilage. In addition, EQ increased bone mineral density, improved the microstructural parameters of the subchondral bone (SB), and decreased the number of osteoclasts.

Conclusion

EQ exerted a chondroprotective effect on OP OA in rats, associated with inhibition of the NF-κB signaling pathway and chondrocyte apoptosis. Furthermore, EQ showed an osteoprotective effect on SB via inhibiting osteoclastic activities.

The lncRNA MIAT/miR-181a-5p axis regulates osteopontin (OPN)-mediated proliferation and apoptosis of human chondrocytes in osteoarthritis

Osteoarthritis (OA) is a slow-progressing degenerative joint disease mainly characterized by progressive cartilage loss and subchondral bone remodeling. Osteopontin (OPN) is a matrix extracellular glyco-phosphoprotein capable of regulating the expression levels of multiple factors linked with OA pathogenesis. This study explores the upstream regulatory molecular mechanism of OPN on proliferation and apoptosis of human chondrocytes in OA. Chondrocytes were isolated from OA cartilage and identified by toluidine blue staining and immunofluorescent staining of type II collagen. An MTT assay was used for cell viability, and a BrdU assay was applied for DNA synthesis. Cell apoptosis was detected by a flow cytometry assay. A lncRNA MIAT/miR-181a-5p/OPN axis regulating OA chondrocyte proliferation and apoptosis were identified. miR-181a-5p directly targeted OPN and inhibited OPN expression in OA chondrocytes. miR-181a-5p overexpression inhibited OA chondrocyte viability, suppressed DNA synthesis, and promoted apoptosis. OPN overexpression exerted opposite effects on OA chondrocytes and significantly attenuated the roles of miR-181a-5p overexpression in OA chondrocytes. A total of six long non-coding RNAs (lncRNAs) were predicted to target miR-181a-5p, and MIAT was the most up-regulated in OA cartilage tissues among the six lncRNAs. Through direct targeting, MIAT inhibited miR-181a-5p expression. MIAT silencing inhibited cell viability, suppressed DNA synthesis, and promoted cell apoptosis. Moreover, miR-181a-5p inhibition partially reversed the effects of MIAT silencing on OA chondrocytes. The lncRNA MIAT/miR-181a-5p/OPN axis could modulate OA chondrocyte proliferation and apoptosis. The comprehensive function of this axis on OA requires further in vivo and clinical investigations.

Interrelationship of Osteopontin, MMP-9 and ADAMTS4 in Patients With Osteoarthritis Undergoing Total Joint Arthroplasty

Osteoarthritis (OA) is a degenerative joint disease characterized by loss of articular cartilage, inflammation and pain, which sometimes necessitates total joint arthroplasty (TJA). Profiling biomarkers of cartilage degradation and inflammation is a promising area of research to understand the pathogenesis of OA. This study aims to report the post-operative fluctuations of 3 biomarkers of OA, osteopontin (OPN), matrix metalloproteinase-9 (MMP-9), and ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs 4), in patients undergoing TJA to further define the interaction among these biomarkers and delineate their role in OA pathogenesis. OPN is an extracellular matrix (ECM) glycoprotein with increased activity in OA and joint damage and is upregulated by either inflammation or cleavage by MMPs and thrombin. MMP-9 is known to cleave OPN and is upregulated by inflammatory markers, such as IL-1, IL-6 and CRP. ADAMTS4 is an enzyme that degrades aggrecan, a major component of cartilage. These biomarkers were measured in deidentified blood samples collected on the day of surgery, 1 day post-operatively, and day 5-7 post-operatively. MMP-9 and OPN levels were significantly elevated at all times, and ADAMTS4 was significantly decreased at baseline versus controls. OPN and ADAMTS4 inversely fluctuated post-operatively, indicating an interrelation between these 2 biomarkers. This study suggests that the upregulation of MMP-9 and therefore OPN then results in the downregulation of ADAMTS4. The relationship between OPN and thrombin also highlights the importance of monitoring for thrombotic complications. These biomarkers, along with thrombin-mediated cleavage products, may be helpful in the prognostic management of OA patients.

The miR-302c/transforming growth factor-β receptor type-2 axis modulates interleukin-1β-induced degenerative changes in osteoarthritic chondrocytes

Chondrocyte production of catabolic and inflammatory mediators participating in extracellular matrix degradation has been regarded as a central event in osteoarthritis (OA) development. During OA pathogenesis, interleukin-1β (IL-1β) decreases the mRNA expression and protein levels of transforming growth factor-β receptor type-2 (TGFBR2), thus disrupting transforming growth factor-β signaling and promoting OA development. In the present study, we attempted to identify the differentially expressed genes in OA chondrocytes upon IL-1β treatment, investigate their specific roles in OA development, and reveal the underlying mechanism. As shown by online data analysis and experimental results, TGFBR2 expression was significantly downregulated in IL-1β-treated human primary OA chondrocytes. IL-1β treatment induced degenerative changes in OA chondrocytes, as manifested by increased matrix metalloproteinase 13 and a disintegrin and metalloproteinase with thrombospondin motifs 5 proteins, decreased Aggrecan and Collagen II proteins, and suppressed OA chondrocyte proliferation. These degenerative changes were significantly reversed by TGFBR2 overexpression. miR-302c expression was markedly induced by IL-1β treatment in OA chondrocytes. miR-302c suppressed the expression of TGFBR2 via direct binding to its 3'- untranslated region. Similar to TGFBR2 overexpression, miR-302c inhibition significantly improved IL-1β-induced degenerative changes in OA chondrocytes. Conversely, TGFBR2 silencing enhanced IL-1β-induced degenerative changes and significantly reversed the effects of miR-302c inhibition in response to IL-1β treatment. In conclusion, the miR-302c/TGFBR2 axis could modulate IL-1β-induced degenerative changes in OA chondrocytes and might become a novel target for OA treatment.

OPN Deficiency Increases the Severity of Osteoarthritis Associated with Aberrant Chondrocyte Senescence and Apoptosis and Upregulates the Expression of Osteoarthritis-Associated Genes

Objectives

A recent work has reported that the elevated osteopontin (OPN) levels in the articular cartilage and synovial fluid are correlated with the progressive osteoarthritis (OA) joint damage, and OPN has a protective effect against OA by suppressing the expressions of OA-associated genes. The present study examined whether the OPN deficiency was susceptible to OA through the regulation of chondrocyte senescence and apoptosis and the expressions of OA-associated genes.

Methods

The mRNA levels of COL2A1 and OPN were compared between human OA chondrocytes and normal chondrocytes. The effects of OPN siRNA on the SA-β-Gal expressions and the percentage of apoptotic chondrocytes were examined by using SA-β-Gal staining and apoptosis assay, and the effects on the expressions of COL2A1 and OA-associated genes (COL10A1, IL-1β, TNF-ɑ, MMP-13, and ADAMTS5) were examined by western blot analysis and quantitative real-time RT-PCR. Furthermore, an in vivo OA model was established to examine the effects of OPN siRNA on the senescence and apoptosis of OA chondrocytes and the expressions of OA-associated genes.

Results

The mRNA levels of COL2A1 and OPN were decreased in knee OA chondrocytes in comparison with those in normal chondrocytes. The OPN deficiency enhanced the senescence and apoptosis of OA chondrocytes and increased the expressions of COL10A1, IL-1β, TNF-ɑ, MMP-13, and ADAMTS5 but decreased the expression of COL2A1. Meanwhile, OPN deficiency could result in severe, accelerated OA in vivo, which was also associated with enhanced senescence and apoptosis of chondrocytes and elevated expressions of OA-associated genes.

Conclusions

The findings of this study suggest that the OPN deficiency can result in accelerated OA, which is associated with enhanced senescence and apoptosis of OA chondrocytes and the upregulated expressions of OA-associated genes.

LINC00623/miR-101/HRAS axis modulates IL-1β-mediated ECM degradation, apoptosis and senescence of osteoarthritis chondrocytes

Chondrocyte apoptosis and extracellular matrix (ECM) degeneration have been implicated in the pathogenesis of osteoarthritis (OA). Based on previously reported microarray analysis, HRAS (Harvey rat sarcoma viral oncogene homolog), a member of the RAS protein family, was chosen as a potential regulator of OA chondrocyte apoptosis and ECM degradation. HRAS expression was downregulated in OA tissues, particularly in mild-OA tissues. HRAS overexpression partially attenuated IL-1β-induced OA chondrocyte apoptosis and ECM degradation. Similar to HRAS, the long non-coding RNA LINC00623 was downregulated in OA tissues. LINC00623 knockdown enhanced IL-1β-induced OA chondrocyte apoptosis and ECM degradation, which could be partially reversed by HRAS overexpression. It has been reported that lncRNAs act as ceRNAs of miRNAs to exert their function. Herein, miR-101 was predicted to bind to both LINC00623 and HRAS, which was further confirmed by luciferase reporter and RIP assays. LINC00623 competed with HRAS for miR-101 binding, therefore reducing the inhibitory effect of miR-101 on HRAS expression. More importantly, the effect of LINC00623 was partially eliminated by miR-101 inhibition. Overall, the LINC00623/miR-101/HRAS axis modulates OA chondrocyte apoptosis, senescence and ECM degradation through MAPK signaling, which might play a critical role in OA development.

XIST/miR-376c-5p/OPN axis modulates the influence of proinflammatory M1 macrophages on osteoarthritis chondrocyte apoptosis

The inflammatory microenvironment in the joints is one of the critical issues during osteoarthritis (OA) and also the main factor that may aggravate symptoms. Under inflammatory microenvironment, M1 macrophages are activated and produce large numbers of proinflammatory mediators, leading to the production of degradative enzymes, the disturbance of chondrocyte apoptosis and cartilage catabolic processes, and finally the deterioration of OA. In the present study, we reveal that the overexpression of osteopontin (OPN), a cytokine, and a matrix protein involved in arthritis and chondrocyte apoptosis in OA, could exacerbate the inflammatory microenvironment in OA via promoting the production of proinflammation cytokines and the levels of degradative enzymes in M1 macrophages, therefore, enhancing the cytotoxicity of M1 macrophage on chondrocytes. XIST expression significantly increases in OA tissue specimens. XIST serves as a competing endogenous RNA for miR-376c-5p to compete with OPN for miR-376c-5p binding, thus counteracting miR-376c-5p-mediated OPN suppression. XIST knockdown could improve the inflammatory microenvironment in OA via acting on M1 macrophages, subsequently affecting the apoptosis of cocultured chondrocytes. miR-376c-5p inhibition exerts an opposing effect on M1 macrophages and cocultured chondrocytes, as well as significantly reverses the effect of XIST knockdown. As a further confirmation, XIST and OPN mRNA expression significantly increased in OA tissues and was positively correlated in tissue samples. In summary, we provide a novel mechanism of macrophages and the inflammatory microenvironment affecting chondrocyte apoptosis. XIST and OPN might be potential targets for OA treatment, which needs further in vivo experimental confirmation.

Genetic association analysis of Osteopontin and Matrix Gla Protein genes polymorphisms with primary knee osteoarthritis in Mexican population

Primary osteoarthritis (OA) is a complex entity in which several loci related to different molecular pathways or classes of molecules are associated with its development as demonstrated through genetic association studies. Genes involved in bone formation and mineralization, such as osteopontin (OPN) and Matrix Gla protein (MGP), could also be related with OA. The aim of this study was to evaluate the association between the genetic variants of OPN and MGP with primary knee osteoarthritis in a Mexican population. A case-control study was conducted in 296 patients with primary knee osteoarthritis and in 354 control subjects. Study groups were assessed radiologically. The rs11730582 of OPN and rs1800802, rs1800801, and rs4236 of MGP were determined by TaqMan allele discrimination assays. The haplotypes of the polymorphisms of MGP were constructed. The association was tested through univariate and multivariate non-conditional logistic regression analyses. The polymorphisms of MGP complied with Hardy-Weinberg (HW) equilibrium. The polymorphisms of OPN and MGP were not significantly associated with primary knee osteoarthritis in the codominant, dominant, and recessive models (p > 0.05). Our study suggests that there are no associations between OPN and MGP polymorphisms with primary knee osteoarthritis in Mexican population.

The role of lncRNA XIST/miR-211 axis in modulating the proliferation and apoptosis of osteoarthritis chondrocytes through CXCR4 and MAPK signaling

Long noncoding RNAs (lncRNAs) participate in multiple diverse diseases, including osteoarthritis (OA). Here, we explored the role of lncRNA XIST in OA and identified the potential molecular mechanisms. The expression of XIST in cartilage samples in patients with OA was significantly upregulated. XIST knockdown remarkably suppressed IL-1β-suppressed OA chondrocyte proliferation while promoted IL-1β-induced cell apoptosis. By employing online tools, miRNAs related to CXCR4, a major contributor to chondrocyte apoptosis, and XIST were selected. miR-211 expression could be significantly inhibited by IL-1β stimulation, and miR-211 negatively regulated XIST expression and CXCR4 protein levels. Through direct binding, XIST served as a ceRNA for miR-211 to counteract miR-211-mediated CXCR4 repression, thereby modulating chondrocyte proliferation and apoptosis through downstream MAPK signaling. In OA tissues, miR-211 expression was significantly downregulated while CXCR4 mRNA expression was upregulated. miR-211 was negatively correlated with XIST and CXCR4, respectively, while XIST and CXCR4 was positively correlated in tissue samples. In conclusion, the study revealed that lncRNA XIST can promote the proliferation of OA chondrocytes and promote apoptosis through the miR-211/CXCR4 axis. Thus, lncRNA XIST might be considered as a potential therapeutic target for OA treatment.

IL-1β-induced miR-34a up-regulation inhibits Cyr61 to modulate osteoarthritis chondrocyte proliferation through ADAMTS-4

Osteoarthritis (OA) is the most prevalent degenerative joint disease with multifactorial etiology caused by risk factors. The degradation of aggrecan by upregulated ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) is the key event in the development of OA. ADAMTS-4 contributes to aggrecan degradation in human OA. Cysteine-rich angiogenic inducer 61 (Cyr61), which is associated with diseases related to chronic inflammation, is found in articular cartilage from patients with osteoarthritis and appears to suppress ADAMTS-4 activity, possibly leading to chondrocyte cloning. Herein, we first revealed that Cyr61 and ADAMTS-4 protein levels were remarkably increased in OA cartilage tissues and OA chondrocytes, and verified Cyr61 regulation of ADAMTS-4 in normal and OA chondrocyte. Further, we revealed that Cyr61 could promote OA chondrocyte proliferation through inhibiting ADAMTS-4. Overproduction of inflammatory cytokines plays a vital role in the pathological development of OA; herein, we demonstrated that IL-1β inhibited Cyr61, while promoted ADAMTS-4 expression. By using online tools and luciferase assays, we confirmed that miR-34a, a regulatory miRNA of chondrocyte proliferation, could directly bind to the 3'-UTR of Cyr61 to inhibit its expression; further, IL-1β regulated Cyr61 and ADAMTS-4 expression through miR-34a. In OA cartilage tissues, miR-34a, and IL-1β mRNA expression was up-regulated and positively correlated; miR-34a and Cyr61 mRNA was positively correlated, further indicating that suppressing miR-34a expression might rescue IL-1β-induced Cyr61 suppression, and promote OA chondrocyte proliferation. Taken together, we provided novel experimental basis for rescuing OA chondrocyte proliferation through miR-34a/Cyr61 axis.

Effects of Artesunate on the Expressions of Insulin-Like Growth Factor-1, Osteopontin and C-Telopeptides of Type II Collagen in a Rat Model of Osteoarthritis

OBJECTIVE

The study aims to explore the effects of artesunate on insulin-like growth factor-1 (IGF-1), Osteopontin (OPN), and C-telopeptides of type II collagen (CTX-II) in serum, synovial fluid (SF), and cartilage tissues of rats with osteoarthritis (OA).

METHODS

OA models were established. Normal model, artesunate, and Viatril-S groups (20 rats respectively) were set. Enzyme-linked immunosorbent assay, IHC staining, and quantitative real-time polymerase chain reaction were conducted to calculate IGF-1, OPN, and CTX-II levels in serum, SF, and cartilage tissues of rats. The pathological changes in cartilage tissues were evaluated with Mankin score and Hematoxylin-Eosin staining.

RESULTS

Compared with the normal group, the model group showed increased IGF-1 level; decreased OPN, CTX-II levels in the serum and SF; and contrary results were seen in the cartilage tissues. A gradual ascending IGF-1 level and descending OPN and CTX-II levels existed in the serum and SF in the artesunate and Viatril-S groups after 2 weeks. The model group showed the most obvious pathological changes and highest Mankin score compared with the other groups. Higher IGF-1 level and lower OPN, CTX-II levels were exhibited in the cartilage tissue in the artesunate and Viatril-S groups but not in the model group.

CONCLUSION

Artesunate and Viatril-S inhibit OA development by elevating IGF-1 level and reducing OPN and CTX-II levels.

MALAT1/miR-127-5p Regulates Osteopontin (OPN)-Mediated Proliferation of Human Chondrocytes Through PI3K/Akt Pathway

Osteoarthritis (OA) is characterized by progressive destruction of articular cartilage, resulting in significant disability. Chondrocytes present in various types of cartilage and are responsible for the growth and maintenance of the tissue. Over-proliferation of human chondrocytes may contributes to OA pathological process. Previously, we revealed that miR-127-5p could inhibit the proliferation of human chondrocytes through osteopontin (OPN). In the present study, we used online tools to figure out several candidates lncRNAs which were potentially correlated with miR-127-5p. Through assessing the expression levels of the candidates lncRNAs, metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was chosen as a further research subject. MALAT1 knockdown significantly repressed human OA chondrocyte proliferation, as well as the protein levels of OPN, p-PI3K, and p-Akt in OA chondrocytes. As verified by luciferase assays, MALAT1 directly bound to miR-127-5p to inhibit miR-127-5p expression. Then we achieved miR-127-5p inhibition through miR-127-5p inhibitor transfection; the miR-127-5p inhibition could promote chondrocyte proliferation, as well as the protein levels of OPN, p-PI3K, and p-Akt; in addition, the MALAT1 knockdown partially reversed the promotive effect of miR-127-5p inhibition on chondrocyte proliferation, OPN and PI3K/Akt signaling-related protein levels. Taken together, MALAT1 could directly bind to miR-127-5p to inhibit its expression, so as to rescue OPN expression and promote chondrocyte proliferation through PI3K/Akt pathway. Targeting MALAT1 so as to rescue miR-127-5p expression in OA might help to inhibit chondrocyte proliferation through miR-127-5p-mediated OPN regulation and downstream PI3K/Akt pathway. J. Cell. Biochem. 119: 431-439, 2018. © 2017 Wiley Periodicals, Inc.

NEAT1/miR-181c Regulates Osteopontin (OPN)-Mediated Synoviocyte Proliferation in Osteoarthritis

Osteoarthritis (OA) is characterized by progressive destruction of articular cartilage, resulting in significant disability. Inflammatory cytokines commonly initiate the extreme changes in the synovium and cartilage microenvironment of the OA patients, subsequently resulting in cell dysfunctions, especially synoviocyte dysfunction. We revealed that the expression of osteopontin (OPN), which has been reported to regulate expression of various inflammatory factors associating with the pathogenesis of OA including matrix metalloprotease 13 (MMP13), interlukine-6 and 8 (IL-6 and IL-8), is significantly upregulated in OA tissues. In the present study, online tools were used to screen out the candidate miRNAs of OPN. Among the candidate miRNAs, miR-181c inhibited OPN mRNA expression the most strongly. Ectopic expression of miR-181c significantly repressed synoviocyte proliferation, as well as the levels of OPN, MMP13, IL-6, and IL-8. Further, the candidate lncRNAs of miR-181c were screened out by using DianaTools; among which NEAT1 showed to inversely regulate miR-181c. By performing Luciferase assays, we revealed that NEAT1 competed with OPN for miR-181c binding. After NEAT1 knockdown, MMP13, IL-6, and IL-8 expression was reduced; the synoviocyte proliferation was repressed, as well as OPN protein levels; the suppressive effect of NETA1 knockdown on synoviocyte proliferation and the indicated factors were partially reversed by miR-181c inhibition. In OA tissues, OPN mRNA, and NEAT1 expression was upregulated, whereas miR-181c expression was downregulated, indicating that targeting NEAT1 to rescue miR-181c expression so as to inhibit OPN expression and synoviocyte proliferation might be an efficient strategy for OA treatment. J. Cell. Biochem. 118: 3775-3784, 2017. © 2017 Wiley Periodicals, Inc.

Osteopontin stimulates matrix metalloproteinase expression through the nuclear factor-κB signaling pathway in rat temporomandibular joint and condylar chondrocytes

BACKGROUND

To examine the possible regulatory mechanisms of osteopontin (OPN) and the nuclear factor-κB (NF-κB) signaling pathway in the temporomandibular joint (TMJ) of rats subjected to chronic sleep deprivation (CSD).

METHODS

Rats were subjected to CSD using the modified multiple platform method. The histomorphology of the TMJ was observed by hematoxylin-eosin staining. OPN and NF-κB/p65 expression were detected by immunohistochemical and immunofluorescence staining together with western blotting. The condylar chondrocytes were isolated from the rat TMJ and treated with recombinant OPN (r-OPN) before detection for the expression of NF-κB/p65 and matrix metalloproteinases (MMPs). Western blotting and reverse transcription-polymerase chain reaction were performed to determine the expression of MMP-1, MMP-3, MMP-9, and MMP-13 in the TMJ and chondrocytes respectively.

RESULTS

There was a statistically significant difference in OPN and NF-κB/p65 expression between the CSD group and control (CON) group. OPN and NF-κB/p65 expression was increased in the CSD group as compared with in the CON group. NF-κB/p65 expression was significantly increased by r-OPN treatment in the chondrocytes. Furthermore, MMP-1, MMP-3, MMP-9, and MMP-13 production was also remarkably elevated in the CSD group as well as in the chondrocytes. Treatment with 1 μg/ml r-OPN for 48 h led to the highest production of inflammatory cytokines in chondrocytes.

CONCLUSIONS

CSD causes pathological alterations in the TMJ. OPN treatment activates the NF-κB signaling pathway and stimulates MMPs in the TMJ and condylar chondrocytes through NF-κB signaling pathway. Chondrocytes treated with 1 μg/ml r-OPN for 48 h produced the highest level of inflammatory cytokines.

Strontium ranelate causes osteophytes overgrowth in a model of early phase osteoarthritis

Background

Osteoarthritis (OA) involves cartilage changes as well as modifications of subchondral bone and synovial tissues. Strontium ranelate (SR), an anti-osteoporosis compound, which is currently in phase III clinical trial for treatment of OA. Evidences suggest that SR preferably deposited in osteophyte, other than in subchondral bone in early phase of OA. This phenomenon raises concern about its utility for OA treatment as a disease-modifying drug. To evaluate the effect of SR on cartilage, subchondral bone mass and subchondral trabecular bone structure in medial meniscectomized (MNX) guinea pigs.

Method

Thirty-six 3-month-old male Dunkin Hartley albino guinea pigs received either sham or medial meniscectomy operations. One week after the procedure, meniscectomized animals began 12 weeks of SR (625 mg/kg, daily) treatment by oral gavage for MNX + SR group, or normal saline for MNX + V group. All animals were euthanized 12 weeks later, cartilage degeneration and subchondral bone micro-architecture was analyzed.

Results

Both OARSI scores (P = 0.523 for marcoscopic scores, P = 0.297 for histological scores) and Cartilage thickness (P = 0.335) in MNX + SR group were comparable to MNX + V group. However, osteophyte sizes were larger in MNX + SR group (P = 0.014), and collapsed osteophytes in MNX + SR group (7 by 12) were significantly more than in MNX + V group (1 by 12) (P = 0.027), while immunohistochemistry indicates catabolic changes in osteophyte/plateau junction. Micro-CT analysis showed bone mineral density (BMD) (P = 0.001), bone volume fraction (BV/TV) (P = 0.008), trabecular spacing (Tb.Sp) (P = 0.020), trabecular thickness (Tb.Th) (P = 0.012) and structure model index (SMI) (P = 0.005) levels to be significantly higher in the MNX + SR group than in the MNX + V group.

Conclusions

SR (625 mg/kg/day) did not protect cartilage from degeneration in MNX guinea pigs but subchondral bone was significantly enhanced. In early phase OA, SR administration causes osteophyte overgrowth, which may be related to incorporation into mineralizing osteophytes. This adverse effect is important for future studies of SR in OA.

Osteopontin Promotes Expression of Matrix Metalloproteinase 13 through NF-κB Signaling in Osteoarthritis

Osteopontin (OPN) is associated with the severity and progression of osteoarthritis (OA); however, the mechanism of OPN in the pathogenesis of OA is unknown. In this study, we found that OA patients had higher abundance of OPN and matrix metalloproteinase 13 (MMP13). In chondrocytes, we showed that OPN promoted the production of MMP13 and activation of NF-κB pathway by increasing the abundance of p65 and phosphorylated p65 and translocation of p65 protein from cytoplasm to nucleus. Notably, inhibition of NF-κB pathway by inhibitor suppressed the production of MMP13 induced by OPN treatment. In conclusion, OPN induces production of MMP13 through activation of NF-κB pathway.

Parathyroid hormone(1-34) exhibits more comprehensive effects than celecoxib in cartilage metabolism and maintaining subchondral bone micro-architecture in meniscectomized guinea pigs

OBJECTIVE

To evaluate the effects of PTH(1-34) on cartilage, subchondral bone mass and structure in medial meniscectomized guinea pigs and compare them to those of celecoxib (CLX).

METHOD

Forty-eight 3-month-old male Hartley albino guinea pigs received either sham or medial meniscectomy (MNX) operations. One week after the procedure, meniscectomized animals began 12 weeks of treatment by oral administration of CLX (20 mg/kg, daily), subcutaneous injection of PTH (1-34) (24 μg/kg, 5 days/week), or normal saline for MNX group. All animals were euthanized 12 weeks later, cartilage degeneration and subchondral bone micro-architecture was analyzed.

RESULTS

OARSI scores indicated cartilage degeneration was partially inhibited by either CLX or PTH(1-34). Cartilage was significantly thicker in PTH(1-34)-treated animals than in CLX-treated animals. Both CLX and PTH(1-34) treatment were associated with lower ADAMTS-4 and periostin expression than MNX. MMP-13 expression in PTH(1-34) group was significantly lower than that in CLX group. However, AGG expression and the ratio of Col-II/MMP-13 expression in PTH(1-34) group were significantly higher than in the CLX group. Micro-CT analysis showed BMD, BV/TV, and Tb.Th levels to be significantly lower in the MNX group and CLX groups than in the sham group, but these parameters were significantly higher in the PTH(1-34) group than in either the MNX group or CLX group.

CONCLUSIONS

Both CLX and PTH(1-34) exhibits protective effects on cartilage degeneration in meniscectomized guinea pigs. However, PTH(1-34) exhibited superior performance to CLX not only in metabolism of cartilage tissue but also in maintenance of subchondral bone micro-architecture.

MicroRNA-127-5p regulates osteopontin expression and osteopontin-mediated proliferation of human chondrocytes

The aim of this study was to determine the specific microRNA (miRNA) that regulates expression of osteopontin (OPN) in osteoarthritis (OA). The potential regulatory miRNAs for OPN messenger RNA (mRNA) were predicted by miRNA prediction programs. Among eight potential regulatory miRNAs, miR-220b, miR-513a-3p and miR-548n increased, while miR-181a, miR-181b, miR-181c, miR-181d and miR-127-5p decreased in OA patients. miRNA-127-5p mimics suppressed OPN production as well as the activity of a reporter construct containing the 3'-UTR of human OPN mRNA. In addition, mutation of miR-127-5p binding site in the 3'-UTR of OPN mRNA abolished miR-127-5p-mediated repression of reporter activity. Conversely, treatment with miR-127-5p inhibitor increased reporter activity and OPN production. Interestingly, miR-127-5p inhibited proliferation of chondrocytes through OPN. In conclusion, miRNA-127-5p is an important regulator of OPN in human chondrocytes and may contribute to the development of OA.

Chondrocytic ephrin B2 promotes cartilage destruction by osteoclasts in endochondral ossification

The majority of the skeleton arises by endochondral ossification, whereby cartilaginous templates expand and are resorbed by osteoclasts then replaced by osteoblastic bone formation. Ephrin B2 is a receptor tyrosine kinase expressed by osteoblasts and growth plate chondrocytes that promotes osteoblast differentiation and inhibits osteoclast formation. We investigated the role of ephrin B2 in endochondral ossification using Osx1Cre-targeted gene deletion. Neonatal Osx1Cre.Efnb2(Δ/Δ) mice exhibited a transient osteopetrosis demonstrated by increased trabecular bone volume with a high content of growth plate cartilage remnants and increased cortical thickness, but normal osteoclast numbers within the primary spongiosa. Osteoclasts at the growth plate had an abnormal morphology and expressed low levels of tartrate-resistant acid phosphatase; this was not observed in more mature bone. Electron microscopy revealed a lack of sealing zones and poor attachment of Osx1Cre.Efnb2(Δ/Δ) osteoclasts to growth plate cartilage. Osteoblasts at the growth plate were also poorly attached and impaired in their ability to deposit osteoid. By 6 months of age, trabecular bone mass, osteoclast morphology and osteoid deposition by Osx1Cre.Efnb2(Δ/Δ) osteoblasts were normal. Cultured chondrocytes from Osx1Cre.Efnb2(Δ/Δ) neonates showed impaired support of osteoclastogenesis but no significant change in Rankl (Tnfsf11) levels, whereas Adamts4 levels were significantly reduced. A population of ADAMTS4(+) early hypertrophic chondrocytes seen in controls was absent from Osx1Cre.Efnb2(Δ/Δ) neonates. This suggests that Osx1Cre-expressing cells, including hypertrophic chondrocytes, are dependent on ephrin B2 for their production of cartilage-degrading enzymes, including ADAMTS4, and this might be required for attachment of osteoclasts and osteoblasts to the cartilage surface during endochondral ossification.