Target For Treatment Of Osteoarthritis Research Articles

IGF2BP1 Bolsters the Chondrocytes Ferroptosis of Osteoarthritis by Targeting m6A/MMP3 Axis.

Chondrocyte degeneration and senescence are characteristics of osteoarthritis (OA) and other joint degenerative diseases, and ferroptosis has been observed to regulate the development of OA. However, the role of the N6-methyladenosine (m6A) modification in OA ferroptosis remains unclear. This study performed series of assays to investigate the function of the m6A reader IGF2BP1 in OA ferroptosis, including m6A quantitative analysis, Iron (Fe2+) release analysis, Malondialdehyde (MDA) measurement, lipid peroxidation (ROS) detection and Glutathione (GSH) measurement. The molecular interaction and mechanism analysis was performed by Luciferase reporter assay, mRNA stability analysis and RNA immunoprecipitation (RIP) assay. These results indicate that IGF2BP1 is upregulated in IL-1β-induced chondrocytes. Functionally, IGF2BP1 silencing represses ferroptosis, including iron (Fe2+) accumulation, malondialdehyde, and reactive oxygen species (ROS). Mechanistically, among the potential downstream targets, matrix metalloproteinase-3 (MMP3) was observed to harbor a significant m6A modified site in the 3'-UTR. IGF2BP1 combines with MMP3 through the binding of m6A sites, thereby enhancing MMP3 mRNA stability. In conclusion, our findings revealed the functions and mechanisms of m6A regulator IGF2BP1 in OA chondrocyte's ferroptosis, providing a novel target for OA treatment.

The immune role of the intestinal microbiome in knee osteoarthritis: a review of the possible mechanisms and therapies.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage damage and synovial inflammation and carries an enormous public health and economic burden. It is crucial to uncover the potential mechanisms of OA pathogenesis to develop new targets for OA treatment. In recent years, the pathogenic role of the gut microbiota in OA has been well recognized. Gut microbiota dysbiosis can break host-gut microbe equilibrium, trigger host immune responses and activate the "gut-joint axis", which aggravates OA. However, although the role of the gut microbiota in OA is well known, the mechanisms modulating the interactions between the gut microbiota and host immunity remain unclear. This review summarizes research on the gut microbiota and the involved immune cells in OA and interprets the potential mechanisms for the interactions between the gut microbiota and host immune responses from four aspects: gut barrier, innate immunity, adaptive immunity and gut microbiota modulation. Future research should focus on the specific pathogen or the specific changes in the gut microbiota composition to identify the related signaling pathways involved in the pathogenesis of OA. In addition, future studies should include more novel interventions on immune cell modifications and gene regulation of specific gut microbiota related to OA to validate the application of gut microbiota modulation in the onset of OA.

Mechanism of HIFs in osteoarthritis.

Osteoarthritis (OA) is a common disabling disease which has a high incidence rate in the elderly. Studies have found that many factors are involved in the pathogenesis of OA. Hypoxia-inducible factors (HIFs) are core regulators that induce hypoxia genes, repair the cellular oxygen environment, and play an important role in the treatment of OA. For example, HIF-1α can maintain the stability of the articular cartilage matrix, HIF-2α is able to cause chondrocyte apoptosis and intensify in-flammatory response, and HIF-3α may be the target gene of HIF-1α and HIF-2α, thereby playing a negative regulatory role. This review examines the mechanism of HIFs in cartilage extracellular matrix degradation, apoptosis, inflammatory reaction, autophagy and then further expounds on the roles of HIFs in OA, consequently providing theoretical support for the pathogenesis of OA and a new target for OA treatment.

Identification of CaMK4 as a sex-difference-related gene in knee osteoarthritis.

Osteoarthritis (OA) is a common degenerative joint disease with a higher prevalence in females than in males. Sex may be a key factor affecting the progression of OA. This study aimed to investigate critical sex-difference-related genes in patients with OA and confirm their potential roles in OA regulation. OA datasets GSE12021, GSE55457, and GSE36700 were downloaded from the Gene Expression Omnibus database to screen OA-causing genes that are differentially expressed in the two sexes. Cytoscape was used to construct a protein-protein interaction network and determine hub genes. Synovial tissues of patients (male and female) with OA and female non-OA healthy controls were obtained to confirm the expression of hub genes and screen the key genes among them. Destabilization of the medial meniscus (DMM)-induced OA mice model was established to verify the screened key genes. Hematoxylin and eosin (HE) staining and Safranin O-fast green dye staining were employed to observe synovial inflammation and pathological cartilage status. The abovementioned three datasets were intersected to obtain 99 overlapping differentially expressed genes, of which 77 were upregulated and 22 were downregulated in female patients with OA. The hub genes screened were EGF, AQP4, CDC42, NTRK3, ERBB2, STAT1, and CaMK4. Among them, Ca2+/calmodulin-dependent protein kinase-4 (CaMK4) was identified as a key sex-related gene for OA. It was significantly higher in female OA patients than in the cases of male patients. Moreover, CaMK4 was significantly increased in female patients with OA compared with the female non-OA group. These results suggest that CaMK4 plays an important role in the progression of OA. OA mouse models demonstrated that CaMK4 expression in the mice knee joint synovial tissue elevated after DMM, with aggravated synovial inflammation and significant cartilage damage. Cartilage damage improved after intraperitoneal administration of the CaMK4 inhibitor KN-93. CaMK4 is a key sex-related gene influencing the progression and pathogenesis of OA and may be considered as a new target for OA treatment.

New Developments in Research on the Relationship Between Osteoarthritis and Oral-Gut Microbes

Osteoarthritis (OA) is the most common type of arthritis. The prevalence and the incidence of OA have been continuously growing along with increased life expectancy and the emerging problem of an aging population around the global. Reported findings have confirmed that osteoarthritis is a chronic inflammatory disease and its major risk factors included genetic susceptibility, aging, and environmental factors. However, the pathogenic mechanisms of osteoarthritis remain unclear. Recent studies have shown that oral-gut microbes are associated with the onset and development of osteoarthritis and may provide new targets for osteoarthritis treatment. Herein, we reviewed the latest developments in research on the relationship between oral-gut microbes and the onset and development of osteoarthritis, with a view to creating new perspectives for further elucidation of the pathogenesis of osteoarthritis and exploration of effective treatments in the future.

Circ_0136474 promotes the progression of osteoarthritis by sponging mir-140-3p and upregulating MECP2.

Circular RNAs (circRNAs) have pivotal roles in the progression of many diseases, including osteoarthritis (OA). The detained function and regulatory mechanism of circ_0136474 in OA are still largely unknown. The chondrocytes (CHON-001 cells) were exposed to interleukin-1 beta (IL-1β) to mimic the injury in OA. The expression levels of circ_0136474, microRNA-140-3p (miR-140-3p), methyl-CpG-binding protein 2 (MECP2) mRNA were measured by qRT-PCR. Cell proliferation was assessed using CCK-8 assay. Flow cytometry was employed for measuring cell apoptosis. All protein levels were evaluated via western blot analysis. ELISA was used for detecting the concentrations of the inflammatory cytokines. Dual-luciferase reporter analysis and RNA Immunoprecipitation analysis were conducted for confirming the association between miR-140-3p and circ_0136474 or MECP2. Circ_0136474 was upregulated in IL-1β-induced CHON-001 cells and OA cartilage tissues. Circ_0136474 deficiency alleviated IL-1β-stimulated CHON-001 cell damage via enhancing cell proliferation and reducing extracellular matrix (ECM) degradation, apoptosis, and inflammation. Circ_0136474 was a sponge of miR-140-3p, and miR-140-3p inhibition reversed the roles of circ_0136474 knockdown in IL-1β-treated CHON-001 cells. Moreover, miR-140-3p directly targeted MECP2, and upregulation of miR-140-3p attenuated L-1β-triggered CHON-001 cell injury via targeting MECP2. Additionally, circ_0136474 regulated MECP2 level via sponging miR-140-3p. Circ_0136474 knockdown alleviated IL-1β-triggered CHON-001 cell damage through modulation of miR-140-3p/MECP2 axis, indicating a new target for treatment of OA.

YAP activation inhibits inflammatory signalling and cartilage breakdown associated with reduced primary cilia expression

To clarify the role of YAP in modulating cartilage inflammation and degradation and the involvement of primary cilia and associated intraflagellar transport (IFT). Isolated primary chondrocytes were cultured on substrates of different stiffness (6-1000kPa) or treated with YAP agonist lysophosphatidic acid (LPA) or YAP antagonist verteporfin (VP), or genetically modified by YAP siRNA, all±IL1β. Nitric oxide (NO) and prostaglandin E2 (PGE2) release were measured to monitor IL1β response. YAP activity was quantified by YAP nuclear/cytoplasmic ratio and percentage of YAP-positive cells. Mechanical properties of cartilage explants were tested to confirm cartilage degradation. The involvement of primary cilia and IFT was analysed using IFT88 siRNA and ORPK cells with hypomorphic mutation of IFT88. Treatment with LPA, or increasing polydimethylsiloxane (PDMS) substrate stiffness, activated YAP nuclear expression and inhibited IL1β-induced release of NO and PGE2, in isolated chondrocytes. Treatment with LPA also inhibited IL1β-mediated inflammatory signalling in cartilage explants and prevented matrix degradation and the loss of cartilage biomechanics. YAP activation reduced expression of primary cilia, knockdown of YAP in the absence of functional cilia/IFT failed to induce an inflammatory response. We demonstrate that both pharmaceutical and mechanical activation of YAP blocks pro-inflammatory signalling induced by IL1β and prevents cartilage breakdown and the loss of biomechanical functionality. This is associated with reduced expression of primary cilia revealing a potential anti-inflammatory mechanism with novel therapeutic targets for treatment of osteoarthritis (OA).

The Role of Mitochondrial Metabolism, AMPK-SIRT Mediated Pathway, LncRNA and MicroRNA in Osteoarthritis.

Osteoarthritis (OA) is the most common joint disease characterized by degeneration of articular cartilage and causes severe joint pain, physical disability, and impaired quality of life. Recently, it was found that mitochondria not only act as a powerhouse of cells that provide energy for cellular metabolism, but are also involved in crucial pathways responsible for maintaining chondrocyte physiology. Therefore, a growing amount of evidence emphasizes that impairment of mitochondrial function is associated with OA pathogenesis; however, the exact mechanism is not well known. Moreover, the AMP-activated protein kinase (AMPK)–Sirtuin (SIRT) signaling pathway, long non-coding RNA (lncRNA), and microRNA (miRNA) are important for regulating the physiological and pathological processes of chondrocytes, indicating that these may be targets for OA treatment. In this review, we first focus on the importance of mitochondria metabolic dysregulation related to OA. Then, we show recent evidence on the AMPK-SIRT mediated pathway associated with OA pathogenesis and potential treatment options. Finally, we discuss current research into the effects of lncRNA and miRNA on OA progression or inhibition.

Inhibition of Cpt1a alleviates oxidative stress-induced chondrocyte senescence via regulating mitochondrial dysfunction and activating mitophagy

Osteoarthritis (OA) is an age-related chronic degenerative disease, and chondrocyte senescence has been established to play an important role in the pathological process. There is ample evidence to suggest that lipid metabolism plays an important role in the aging process. However, the effect of lipid metabolism on chondrocyte senescence and OA remains unclear. Accordingly, we constructed a TBHP-induced senescent chondrocytes model and a destabilization of the medial meniscus (DMM) mouse model. We found that lipid accumulation and fatty acid oxidation were enhanced in senescent chondrocytes. Interestingly, carnitine palmitoyltransferase 1A (Cpt1a), the rate-limiting enzyme for fatty acid oxidation, was highly expressed in senescent chondrocytes and murine knee cartilage tissue. Suppressing Cpt1a expression using siRNA or Etomoxir, an inhibitor of Cpt1a, could attenuate oxidative stress-induced premature senescence and OA phenotype of primary murine chondrocytes, decrease cellular ROS levels, restore mitochondrial function, and maintain mitochondrial homeostasis via activating mitophagy. In vivo, pharmacological inhibition of Cpt1a by Etomoxir attenuated cartilage destruction, relieved joint space narrowing and osteophyte formation in the DMM mouse model. Overall, these findings suggested that knockdown of Cpt1a alleviated chondrocyte senescence by regulating mitochondrial dysfunction and promoting mitophagy, providing a new therapeutic strategy and target for OA treatment.

LncRNA LEMD1-AS1 relieves chondrocyte inflammation by targeting miR-944/PGAP1 in osteoarthritis

ABSTRACT Osteoarthritis (OA) is a common degenerative disease characterized by reducing articular chondrocytes and destruction of joint matrix, it’s detailed pathogenesis remains unclear. Emerging evidences have demonstrated that long non-coding RNAs (lncRNAs) are closely related to the progression of OA. This study aims to explore the expression of long non-coding RNA LEMD1 antisense RNA 1 (LEMD1-AS1) in OA tissues and chondrocytes and investigate the possible mechanisms of LEMD1-AS1 in OA, which will provide a new target for the treatment of OA. In our study, LEMD1-AS1 and post-GPI attachment to protein (PGAP1) were lowly expressed, but miR-944 was highly expressed both in OA tissues and in Lipopolysaccharide (LPS) -treated chondrocytes detected by qRT-PCR. Over-expression of LEMD1-AS1 or down-regulation of miR-944 significantly promoted viability, proliferation and inhibited cell apoptosis, cell cycle arrest and inflammatory responses of chondrocytes treated with LPS by CCK-8, EdU, flow cytometry and an ELISA assay. Over-expression of LEMD1-AS1 or down-regulation of miR-944 remarkably increased the protein levels of PCNA, Ki-67, Cyclin A1, Cyclin B1, Cyclin D2 and Bcl-2, while decreasing the protein levels of p27, Bax, Cleaved-caspase-3 and Cleaved-caspase-9 in chondrocytes treated with LPS. LEMD1-AS1 bound to miR-944 and regulated its expression, and PGAP1 presented as a direct target gene of miR-944, which was confirmed by a dual-luciferase reporter assay. Inhibition of PGAP1 partially restored the effects of LEMD1-AS1/miR-944 on the proliferation, cell apoptosis, cell cycle distribution and inflammatory responses of LPS-treated chondrocytes. To conclude, the LEMD1-AS1/miR-944/PGAP1 axis may be a novel therapeutic candidate to target in OA treatment.

Toll-like receptor 3 activation promotes joint degeneration in osteoarthritis

Osteoarthritis (OA) is characterized by cartilage degradation that is induced by inflammation. Sterile inflammation can be caused by damage-associated molecular patterns that are released by chondrocytes and activate pattern recognition receptors. We evaluate the role of toll-like receptor-3-activating RNA in the pathogenesis of OA. Toll-like receptor 3 (TLR3) was detected by semiquantitative reverse transcriptase PCR, western blotting and microscopy. Rhodamine-labelled poly(I:C) was used to image uptake in chondrocytes and full-thickness cartilage. The production of IFNβ in chondrocytes after stimulation with poly(I:C) as well as in the synovial fluid of OA patients was measured using ELISA. Chondrocyte apoptosis was chemically induced using staurosporine. Immunohistochemistry was performed to examine TLR3 expression and apoptosis in human and murine OA cartilage. RNA in synovial fluid was quantified by RiboGreen assay. Destabilisation of the medial meniscus was performed in TLR3−/− and wildtype mice. OA was assessed after eight weeks using OARSI score. TLR3 expression was confirmed by western blot and RT-PCR. Poly(I:C) was internalised by chondrocytes as well as cartilage and caused an increase of IFNβ production in murine (11.46 ± 11.63 (wo) to 108.7 ± 25.53 pg/ml; N = 6) and human chondrocytes (1.88 ± 0.32 (wo) to 737.6 ± 130.5 pg/ml; N = 3; p < 0.001). OA cartilage showed significantly more TLR3-positive (KL0 = 0.22 ± 0.24; KL4 = 6.02 ± 6.75; N ≥ 15) and apoptotic chondrocytes (KL0 = 0.6 ± 1.02; KL4 = 9.78 ± 7.79; N ≥ 12) than healthy cartilage (p < 0.001). Staurosporine-induced chondrocyte apoptosis causes a dose-dependent RNA release (0 ng/ml = 1090 ± 39.1 ng/ml; 1000 ng/ml=2014 ± 160 ng/ml; N = 4; p < 0.001). Human OA synovial fluid contained increased concentrations of RNA (KL0-2 = 3408 ± 1129 ng/ml; KL4 = 4870 ± 1612ng/ml; N ≥ 7; p < 0.05) and IFNβ (KL0-2 = 41.95 ± 92.94 ng/ml; KL3 = 1181 ± 1865ng/ml; N ≥ 8; p < 0.05). TLR3−/− mice showed reduced cartilage degradation eight weeks after OA induction (OARSI WT = 5.5 ± 0.04; TLR3−/− = 3.75 ± 1.04; N ≥ 6) which was accompanied by gradually decreasing levels of TUNEL-positive cells (WT = 34.87 ± 24.10; TLR3−/ = 19.64 ± 7.89) resulting in decreased IFNβ expression (WT = 12.57 ± 5.43; TLR3−/− = 6.09 ± 2.07) in cartilage (p < 0.05). The release of RNA by apoptotic chondrocytes thus activating TLR3 signalling is one possible way of perpetuating inflammatory cartilage changes. The inhibition of TLR3 could be a possible therapeutic target for OA treatment.

Bone marrow mesenchymal stem cell-derived exosomal miR-206 promotes osteoblast proliferation and differentiation in osteoarthritis by reducing Elf3.

MicroRNAs (miRNAs) serve as gene silencers involved in essential cell functions. The role of miR‐206 and E74‐like factor 3 (Elf3) has been identified in osteoarthritis (OA), while the effect of exosomal miR‐206 from bone marrow mesenchymal stem cells (BMSCs) in OA remains largely unknown. Thus, we aim to explore the role of exosomal miR‐206 from BMSCs in OA with the involvement of Elf3. BMSCs and BMSC‐derived exosomes (BMSC‐exos) were obtained and identified. OA mouse models were constructed by anterior cruciate ligament transection and then treated with BMSC‐exos or BMSC‐exos containing miR‐206 mimic/inhibitor. The expression of miR‐206, Elf3, inflammatory factors, osteocalcin (OCN) and bone morphogenetic protein 2 (BMP2) in mouse femoral tissues was assessed. The pathological changes in mouse femur tissues were observed. The mouse osteoblasts were identified and treated with untransfected or transfected BMSC‐exos, and then, the expression of miR‐206, Elf3, OCN and BMP2 was determined. The alkaline phosphatase (ALP) activity, calcium deposition level, OCN secretion, proliferation, apoptosis and cell cycle arrest in osteoblasts were measured. MiR‐206 was down‐regulated while Elf3 was up‐regulated in OA animal and cellular models. Exosomal miR‐206 ameliorated inflammation and increased expression of OCN and BMP2 in mouse femoral tissues. Moreover, exosomal miR‐206 promoted ALP activity, calcium deposition level, OCN secretion and proliferation and inhibited apoptosis in OA osteoblasts. Overexpressed Elf3 reversed miR‐206 up‐regulation‐induced effects on OA osteoblasts. BMSC‐derived exosomal miR‐206 promotes proliferation and differentiation of osteoblasts in OA by reducing Elf3. Our research may provide novel targets for OA treatment.

Proteomic Analysis of Synovial Fibroblasts and Articular Chondrocytes Co-Cultures Reveals Valuable VIP-Modulated Inflammatory and Degradative Proteins in Osteoarthritis.

Osteoarthritis (OA) is the most common musculoskeletal disorder causing a great disability and a reduction in the quality of life. In OA, articular chondrocytes (AC) and synovial fibroblasts (SF) release innate-derived immune mediators that initiate and perpetuate inflammation, inducing cartilage extracellular matrix (ECM) degradation. Given the lack of therapies for the treatment of OA, in this study, we explore biomarkers that enable the development of new therapeutical approaches. We analyze the set of secreted proteins in AC and SF co-cultures by stable isotope labeling with amino acids (SILAC). We describe, for the first time, 115 proteins detected in SF-AC co-cultures stimulated by fibronectin fragments (Fn-fs). We also study the role of the vasoactive intestinal peptide (VIP) in this secretome, providing new proteins involved in the main events of OA, confirmed by ELISA and multiplex analyses. VIP decreases proteins involved in the inflammatory process (CHI3L1, PTX3), complement activation (C1r, C3), and cartilage ECM degradation (DCN, CTSB and MMP2), key events in the initiation and progression of OA. Our results support the anti-inflammatory and anti-catabolic properties of VIP in rheumatic diseases and provide potential new targets for OA treatment.

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.

Comparative transcriptomics and network pharmacology analysis to identify the potential mechanism of celastrol against osteoarthritis.

Celastrol is a promising therapeutic agent for the treatment of osteoarthritis (OA). However, the mechanism of action of celastrol is unclear. This study was aiming to identify the potential function of celastrol on OA and determine its underlying mechanism. Celastrol targets were collected from web database searches and literature review, while pathogenic OA targets were obtained from Online Mendelian Inheritance in Man (OMIM) and GeneCards databases. Transcriptomics data was sequenced using an Illumina HiSeq 4000 platform. Celastrol-OA overlapping genes were then identified followed by prediction of the potential function and signaling pathways associated with celastrol using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. A celastrol-target network was constructed to identify the candidate core targets of celastrol. The predictions were then validated by performing molecular docking and molecular dynamics simulation studies. In total, 96 genes were identified as the putative celastrol targets for treatment of OA. These genes were possibly involved in cell phenotype changes including response to lipopolysaccharide and oxidative stress as well as in cell apoptosis and aging. The genes also induced the mTOR pathway and AGE-RAGE signaling pathway at the intracellular level. Additionally, results indicated that 13 core targets including mTOR, TP53, MMP9, EGFR, CCND1, MAPK1, STAT3, VEGFA, CASP3, TNF, MYC, ESR1, and PTEN were likely direct targets of celastrol in OA. Finally, mTOR was determined as the most likely therapeutic target of celastrol in OA. This study provides a basic understanding and novel insight into the potential mechanism of celastrol against OA. Key Points • Our study provides a strong indication that further study of celastrol therapy in OA is required. • mTOR is the most likely therapeutic target of celastrol in OA.

Iron Overload Is Associated With Accelerated Progression of Osteoarthritis: The Role of DMT1 Mediated Iron Homeostasis

Objective: Iron overload is common in elderly people which is associated with an increased prevalence of osteoarthritis (OA), but the exact role of iron in the development of OA has not been established. The aim of the present study is to elucidate the connection between iron overload and OA using an iron overloaded mice model, as well as to explore the role of iron homeostasis, iron transporters dependent iron influx in OA pathogenesis.Methods: The iron overloaded mice model was established and OA was surgically induced. OA progression was assessed at 8 weeks after surgery. Next, primary chondrocytes were treated with pro-inflammatory cytokines and iron regulators mediated iron homeostasis were evaluated. Involvement of iron transporters was analyzed using chondrocytes mimicking an osteoarthritis-related phenotype in vitro.Results: Iron overloaded mice exhibited greater cartilage destruction and elevated ADAMTS5 as well as MMP13 expression along with increased iron accumulation and dysregulated iron regulators. Pro-inflammatory cytokines could disturb cellular iron homeostasis via upregulating iron import proteins, TFR1 and DMT1, downregulating iron efflux protein FPN, thus result in cellular iron overload. Among iron transporters, DMT1 was found to play pivotal roles in iron overload induced OA progress. Inhibition of DMT1 suppressed IL-1β induced inflammatory response and ECM degradation via blockade of MAPK and PI3K/AKT/NF-κB pathways.Conclusions: Our results suggest that iron takes parts in the development of OA and cutting iron influx via inhibiting DMT1 activity could be an attractive new target for OA treatment.

CircSERPINE2 weakens IL-1β-caused apoptosis and extracellular matrix degradation of chondrocytes by regulating miR-495/TGFBR2 axis.

The dysregulated circular RNAs (circRNAs) are relevant to the development of osteoarthritis (OA). The circRNA serpin family E member 2 (circSERPINE2) is dysregulated in OA, while the role and mechanism of circSERPINE2 in OA are largely unknown. The aim of our research is to explore how and whether circSERPINE2 regulates interleukin-1β (IL-1β)-caused chondrocyte damage in OA. In the present study, the chondrocytes (CHON-001 cells) were exposed to IL-1β to mimic the injury in OA. CircSERPINE2, microRNA-495 (miR-495) and transforming growth factor-β receptor 2 (TGFBR2) abundances were detected via quantitative reverse-transcription polymerase chain reaction (qRT-PCR) or Western blot. Cell apoptosis was assessed via viability, apoptotic rate and caspase-3 activity. Extracellular matrix was investigated by levels of Sry-type high-mobility-group box 9 (SOX9), collagen type II α 1 (COL2A1) and Aggrecan using Western blot. The interaction among circSERPINE2, miR-495 and TGFBR2 was assessed via dual-luciferase reporter analysis and RNA immunoprecipitation (RIP). The results showed that circSERPINE2 expression was reduced in OA patients and IL-1β-treated chondrocytes. CircSERPINE2 overexpression mitigated IL-1β-caused apoptosis and extracellular matrix degradation. miR-495 was targeted by circSERPINE2 and up-regulated in OA patients and IL-1β-treated chondrocytes. miR-495 up-regulation reversed overexpression of circSERPINE2-mediated inhibition of apoptosis and extracellular matrix degradation. TGFBR2 was targeted by miR-495 and lowly expressed in OA patients and IL-1β-treated chondrocytes. CircSERPINE2 could mediate TGFBR2 expression by binding with miR-495. As a conclusion, circSERPINE2 attenuated IL-1β-caused apoptosis and extracellular matrix degradation of chondrocytes by regulating miR-495/TGFBR2 axis, indicating a new target for OA treatment.

Biomaterial strategies for improved intra-articular drug delivery.

Osteoarthritis (OA) is a joint degenerative disease that has become one of the leading causes of disability in the world. It is estimated that OA affects 50 million adults in the United States. Currently, there are no FDA-approved treatments that slow OA progression and its treatment is limited to pain management strategies and life style changes. Despite the discovery of several disease-modifying OA drugs (DMOADs) and promising results in preclinical studies, their clinical translation has been significantly limited because of poor intra-articular (IA) bioavailability and challenges in delivering these compounds to tissues of interest within the joint. Here, we review current OA treatments and their effectiveness at reducing joint pain, as well as novel targets for OA treatment and the challenges related to their clinical translation. Moreover, we discuss intra-articular (IA) drug delivery as a promising route of administration, describe its inherent challenges, and review recent advances in biomaterial-based IA drug delivery for OA treatment. Finally, we highlight the potential of tissue targeting in the development of effective IA drug delivery systems.

The New Role of Sirtuin1 in Human Osteoarthritis Chondrocytes by Regulating Autophagy.

The aim of this study is to investigate the role of Sirtuin1 (Sirt1) in the regulation of autophagy for human osteoarthritis (OA) chondrocytes. All cartilage samples were collected from human donors, including young group, aged group, and OA group. Primary chondrocytes were isolated and cultured with Sirt1 activator or inhibitor. Sirt1 expression in cartilage tissue and chondrocytes was evaluated, and the deacetylation activity of Sirt1 was determined. The alteration of autophagy activity after upregulating or downregulating Sirt1 was detected. Chondrocytes were treated with autophagy activator and inhibitor, and then the protein level of Sirt1 was examined. The interactions between Sirt1 and autophagy-related proteins Atg7, microtubule associated protein 1 light chain 3 (LC3), and Beclin-1 were determined by using immunoprecipitation. The assay of articular cartilage revealed that the expression of Sirt1 might be age-related: highly expressed in of younger people, and respectively decreased in the elderly people and OA patients. In vitro study was also validated this result. Further study confirmed that higher levels of Sirt1 significantly increased autophagy in aged chondrocytes, while the lower expression of Sirt1 reduced autophagy in young chondrocytes. Of note, the high levels of Sirt1 reduced autophagy in OA chondrocytes. When the chondrocytes were treated with autophagy activator or inhibitor, we found the expression of Sirt1 was not affected. In addition, we found that Sirt1 could interact with Atg7. These results suggest that Sirt1 in human chondrocytes regulates autophagy by interacting with autophagy related Atg7, and Sirt1 may become a more important target in OA treatment.

EGFR Signaling: Friend or Foe for Cartilage?

ABSTRACTRecent studies using genetically modified mice, pharmacological approaches, and human samples have highlighted an important role for the epidermal growth factor receptor (EGFR), selected ligands, and downstream components in endochondral bone formation and joint homeostasis. Although most data demonstrate an important function of this pathway in endochondral ossification and articular cartilage growth, conflicting results on its role in osteoarthritis have been reported. In some contexts, inactivation of EGFR signaling has been shown to protect joints from surgically induced osteoarthritis, whereas in others, similar manipulations worsened joint pathology. The current review summarizes recent studies of cartilage EGFR signaling in long bone development and diseases, provides potential explanations for the reported discrepancies, and suggests directions for future work to clarify the potential of this pathway as target for osteoarthritis treatment. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.