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ObjectivesCircular RNAs (circRNAs) have emerged as significant biological regulators. Herein, we aimed to elucidate the role of an unidentified circRNA (circPDE4B) that is reportedly downregulated in osteoarthritis (OA) tissues.MethodsThe effects of circPDE4B were explored in human and mouse chondrocytes in vitro. Specifically, RNA pull-down (RPD)-mass spectrometry analysis (MS), immunoprecipitation, glutathione-S-transferase (GST) pull-down, RNA immunoprecipitation and RPD assays were performed to verify the interactions between circPDE4B and the RIC8 guanine nucleotide exchange factor A (RIC8A)/midline 1 (MID1) complex. A mouse model of OA was also employed to confirm the role of circPDE4B in OA pathogenesis in vivo.ResultscircPDE4B regulates chondrocyte cell viability and extracellular matrix metabolism. Mechanistically, FUS RNA binding protein (FUS) was found to promote the splicing of circPDE4B, while downregulation of circPDE4B in OA is partially caused by upstream inhibition of FUS. Moreover, circPDE4B facilitates the association between RIC8A and MID1 by acting as a scaffold to promote RIC8A degradation through proteasomal degradation. Furthermore, ubiquitination of RIC8A at K415 abrogates RIC8A degradation. The circPDE4B–RIC8A axis was observed to play an important role in regulating downstream p38 mitogen-activated protein kinase (MAPK) signalling. Furthermore, delivery of a circPDE4B adeno-associated virus (AAV) abrogates the breakdown of cartilage matrix by medial meniscus destabilisation in mice, whereas a RIC8A AAV induces the opposite effect.ConclusionThis work highlights the function of the circPDE4B–RIC8A axis in OA joints, as well as its regulation of MAPK-p38, suggesting this axis as a potential therapeutic target for OA.

Osteoarthritis (OA), characterized as an end-stage syndrome caused by risk factors accumulated with age, significantly impacts quality of life in the elderly. Circular RNAs (circRNAs) are receiving increasing attention regarding their role in OA progression and development; however, their role in the regulation of age-induced and oxidative stress-related OA remains unclear. Methods: Herein, we explored oxidative stress in articular cartilage obtained from patients of different ages. The presence of circRSU1 was detected using RNA sequencing of H2O2-stimulated primary human articular chondrocytes (HCs), and validated in articular cartilage and HCs using fluorescence in situ hybridization (FISH) staining. miR-93-5p and mitogen-activated protein kinase kinase kinase 8 (MAP3K8) were identified as interactive circRSU1 partners based on annotation and target prediction databases, and their associations were identified through dual-luciferase reporter analysis. The effect of the circRSU1-miR-93-5p-MAP3K8 axis on HCs was confirmed using western blot, quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and reactive oxygen species (ROS) analyses. CircRSU1 and its mutant were ectopically expressed in mice to assess their effects in destabilization of the medial meniscus (DMM) in mice. Results: We found a marked upregulation of circRSU1 in H2O2-treated HCs and OA articular cartilage from elderly individuals. circRSU1 was induced by IL-1β and H2O2 stimulation, and it subsequently regulated oxidative stress-triggered inflammation and extracellular matrix (ECM) maintenance in HCs, by modulating the MEK/ERK1/2 and NF-κB cascades. Ectopic expression of circRSU1 in mouse joints promoted the production of ROS and loss of ECM, which was rescued by mutation of the mir-93-5p target sequence in circRSU1. Conclusion: We identified a circRSU1-miR-93-5p-MAP3K8 axis that modulates the progression of OA via oxidative stress regulation, which could serve as a potential target for OA therapy.

Osteoarthritis (OA) is a common chronic degenerative joint disease associated with a variety of risk factors including aging, genetics, obesity, and mechanical disturbance. This study aimed to elucidate the function of a patient-derived Circular RNA (circRNA), circFNDC3B, in OA progression and its relationship with the NF-κB signaling pathway and oxidative stress. The circFNDC3B/miR-525-5p/HO-1 axis and its relationship with the NF-κB signaling pathway and oxidative stress were investigated and validated using fluorescence in situ hybridization, real-time PCR, western blotting, immunofluorescence analysis, luciferase reporter assays, pull-down assays, and reactive oxygen species analyses. The functions of circFNDC3B in OA was investigated in vitro and in vivo. These evaluations demonstrated that circFNDC3B promotes chondrocyte proliferation and protects the extracellular matrix (ECM) from degradation. We also revealed that circFNDC3B defends against oxidative stress in OA by regulating the circFNDC3B/miR-525-5p/HO-1 axis and the NF-κB signaling pathway. Further, we found that overexpression of circFNDC3B alleviated OA in a rabbit model. In summary, we identified a new circFNDC3B/miR-525-5p/HO-1 signaling pathway that may act to relieve OA by alleviating oxidative stress and regulating the NF-κB pathway, resulting in the protection of the ECM in human chondrocytes, highlighting it as a potential therapeutic target for the treatment of OA.

Particle-induced implant loosening is a major challenge to long-term survival of joint prostheses. Administration of intermittent parathyroid hormone (PTH) has shown potential in the treatment of cases of early-stage periprosthetic osteolysis, while sequential administration of intermittent PTH (iPTH) and bisphosphonates (Bps) has achieved significant effects on treatment of postmenopausal osteoporosis. The objective of this study was to determine whether sequential treatment could preserve bone mass and implant fixation during a pathological course of peri-implant osteolysis in a rat model. Ninety male Sprague Dawley rats were randomly divided into nine groups, four of which were used for confirmation of establishment of the peri-implant osteolysis model at two time points, while the other five were used to determine the efficiency of the sequential treatment on peri-implant osteolysis. Implant fixation and peri-implant bone mass were evaluated using biomechanical testing, micro-CT analysis, and histology at 6 and 12 weeks postoperative. The biomechanical test demonstrated that the maximum loading force during a push-out test was significantly elevated in the sequential treatment group compared to the osteolysis group and iPTH withdrawal group at 12 weeks. Peri-implant bone morphology also indicated a robust increase in bone volume in the sequential treatment group. Sequential administration of iPTH and Bps was effective in preventing experimental peri-implant osteolysis, resulting in improved implant fixation and increased peri-implant bone volume. Clinical significance: The innovative application of sequential treatment in peri-implant osteolysis could be used clinically to improve the prognosis of patients with early-stage periprosthetic osteolysis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1489-1497, 2019.

ObjectivesCircular RNAs (circRNA) expression aberration has been identified in various human diseases. In this study, we investigated whether circRNAs could act as competing endogenous RNAs to regulate the pathological process of osteoarthritis (OA).MethodsCircRNA deep sequencing was performed to the expression of circRNAs between OA and control cartilage tissues. The regulatory and functional role of CircSERPINE2 upregulation was examined in OA and was validated in vitro and in vivo, downstream target of CircSERPINE2 was explored. RNA pull down, a luciferase reporter assay, biotin-coupled microRNA capture and fluorescence in situ hybridisation were used to evaluate the interaction between CircSERPINE2 and miR-1271-5 p, as well as the target mRNA, E26 transformation-specific-related gene (ERG). The role and mechanism of CircSERPINE2 in OA was also explored in rabbit models.ResultsThe decreased expression of CircSERPINE2 in the OA cartilage tissues was directly associated with excessive apoptosis and imbalance between anabolic and catabolic factors of extracellular matrix (ECM). Mechanistically, CircSERPINE2 acted as a sponge of miR-1271-5 p and functioned in human chondrocytes (HCs) through targeting miR-1271-5 p and ERG. Intra-articular injection of adeno-associated virus-CircSERPINE2-wt alleviated OA in the rabbit model.ConclusionsOur results reveal an important role for a novel circRNA-CircSERPINE2 in OA progression. CircSERPINE2 overexpression could alleviate HCs apoptosis and promote anabolism of ECM through miR-1271-ERG pathway. It provides a potentially effective therapeutic strategy for OA progression.

Kümmell disease (KD) causes serious vertebral body collapse in patients. However, only a few case reports have been conducted and the number of patients with KD investigated was limited. Additionally, the frequently used poly(methyl methacrylate) (PMMA) bone cement for KD is limited by excessive modulus and poor biocompatibility. Herein, we aimed to modify PMMA bone cement with mineralized collagen (MC), and compare the clinical effects, image performance and finite element analysis between the modified bone cement and PMMA bone cement for the treatment of phase I and II KD. Thirty-nine KD patients treated with PMMA bone cement and 40 KD patients treated with MC-modified PMMA bone cement from June 2015 to March 2017 were retrospectively analyzed. The surgical procedure, intraoperative blood loss, hospital stay and complications were compared between different groups. Visual analog scale, Oswestry disability index, anterior vertebral height, posterior vertebral height, computed tomography value, adjacent vertebral re-fracture, Cobb angle and wedge-shaped correction angle were evaluated. Additionally, the representative sample was selected for finite element analysis. We found that the MC-modified PMMA bone cement could achieve the same effect as that of PMMA bone cement and was associated with better vertebral height restoration in the long term.

Osteoarthritis (OA) is a degenerative joint disease. Currently, apart from symptomatic treatment or joint replacement, no other effective treatments for OA exist. The mechanisms underlying OA remain elusive and require further research. Circular RNAs (circRNAs) are known to be involved in many diseases; however, their function in OA is not yet fully understood. Here, we identified a novel circRNA, Circ0083429. The role of Circ0083429 in OA was confirmed via western blot (WB), quantitative real-time PCR (qRT-PCR), and immunofluorescence (IF) through knockdown and overexpression experiments. The binding of Circ0083429 to downstream miR-346 and its target gene SMAD3 was predicted via bioinformatics analysis and verified using a luciferase reporter assay and RNA pulldown experiments. Finally, the function of Circ0083429 was evaluated in mouse OA models. In our study, we found that Circ0083429 regulates the homeostasis of the extracellular matrix (ECM) in human chondrocytes. Mechanistically, Circ0083429 affects OA by regulating the mRNA level of SMAD3 through the sponging of microRNA (miRNA)-346. Injecting adeno-associated virus Circ0083429 into the intra-junction of the mouse knee alleviated OA. In conclusion, Circ0083429 regulates the ECM via the regulation of the downstream miRNA-346/SMAD3 in human chondrocytes, which provides a new therapeutic strategy for OA.

Rationale: Osteoarthritis (OA) is the most common joint disease worldwide. Previous studies have identified the imbalance between extracellular matrix (ECM) catabolism and anabolism in cartilage tissue as the main cause. To date, there is no cure for OA despite a few symptomatic treatments. This study aimed to investigate the role of CircCDK14, a novel circRNA factor, in the progression of OA, and to elucidate its underlying molecular mechanisms. Methods: The function of CircCDK14 in OA, as well as the interaction between CircCDK14 and its downstream target (miR-125a-5p) and mRNA target (Smad2), was evaluated by western blot (WB), immunofluorescence (IF), RNA immunoprecipitation (RIP), quantitative RT-PCR, luciferase assay and fluorescence in situ hybridization (FISH). Rabbit models were introduced to examine the function and mechanism of CircCDK14 in OA in vivo. Results: In our present study, we found that CircCDK14, while being down-regulated in the joint wearing position, regulated metabolism, inhibited apoptosis and promoted proliferation in the cartilage. Mechanically, the protective effect of CircCDK14 was mediated by miR-125a-5p sponging, which downregulated the Smad2 expression and led to the dysfunction of TGF-β signaling pathway. Intra-articular injection of adeno-associated virus-CircCDK14 also alleviated OA in the rabbit model. Conclusion: Our study revealed an important role of CircCDK14/miR-125a-5p/Smad2 axis in OA progression and provided a potential molecular therapeutic strategy for the treatment of OA.

Aims Postmenopausal osteoporosis is a bone metabolism disease that is caused by an imbalance between bone-resorbing osteoclast and bone-forming osteoblast actions. Herein, we describe the role of troxerutin (TRX), a trihydroxyethylated derivative of rutin, in ovariectomy (OVX)-induced osteoporosis and its effects on the regulation of osteoclasts and osteoblasts. Main methods In vivo, OVX female mice were intraperitoneally injected with either saline, 50 mg/kg TRX, or 150 mg/kg TRX for 6 weeks and then sacrificed for micro-computed tomography analyses, histological analyses, and biomechanical testing. In vitro, RAW264.7 cell-derived osteoclasts and MC3T3-E1 cell-derived osteoblasts were treated with different concentrations of TRX to examine the effect of TRX on osteoclastogenesis and bone resorption, as well as on osteogenesis and mineralization. Key findings In this study, we demonstrated that TRX prevented cortical and trabecular bone loss in ovariectomized mice by reducing osteoclastogenesis and promoting osteogenesis in vivo. In vitro, TRX inhibited the formation and activity of RAW264.7-derived osteoclasts and the expression of nuclear factor of activated T-cells 1 and cathepsin K. Meanwhile, TRX improved the osteogenesis and mineralization of MC3T3-E1 by enhancing the expression of Runt-related transcription factor 2, Osterix, and collagen type 1 alpha 1. Significance Our data demonstrated that TRX could prevent OVX-induced osteoporosis and be used in a novel treatment for postmenopausal osteoporosis.

Background and Purpose Aseptic prosthesis loosening, caused by wear particles, is one of the most common causes of arthroplasty failure. Extensive and over-activated osteoclast formation and physiological functioning are regarded as the mechanism of prosthesis loosening. Therapeutic modalities based on inhibiting osteoclast formation and bone resorption have been confirmed to be an effective way of preventing aseptic prosthesis loosening. In this study, we have investigated the effects of sophocarpine (SPC, derived from Sophora flavescens) on preventing implant loosening and further explored the underlying mechanisms. Experimental Approach The effects of SPC in inhibiting osteoclastogenesis and bone resorption were evaluated in RANKL-induced osteoclast formation in vitro. A rat femoral particle-induced peri-implant osteolysis model was established. Subsequently, micro-CT, histology, mechanical testing and bone turnover were used to assess the effects of SPC in preventing implant loosening. Key Results In vitro, we found that SPC suppressed osteoclast formation, bone resorption, F-actin ring formation and osteoclast-associated gene expression by inhibiting NF-κB signaling, specifically by targeting IκB kinases (IKKs). Our in vivo study showed that SPC prevented particle-induced prosthesis loosening by inhibiting osteoclast formation, resulting in reduced periprosthetic bone loss, diminished pseudomembrane formation, improved bone-implant contact, reduced bone resorption-related turnover, and enhanced stability of implants. Inhibition of NF-κB signaling by SPC was further confirmed in vivo. Conclusion and Implications Our data demonstrated that SPC can prevent implant loosening through inhibiting osteoclast formation and bone resorption. Thus,SPC might be a novel therapeutic agent to prevent prosthesis loosening and for osteolytic diseases.

Osteoporosis results from an imbalance between bone formation and bone resorption. Traditional drugs for treating osteoporosis are associated with serious side effects, and thus, new treatment methods are required. This study investigated the role of differentially expressed microRNAs during osteoclast differentiation and osteoclast activity during osteoarthritis as well as the associated underlying mechanisms. We used a microarray to screen microRNAs that decreased in the process of osteoclast differentiation and verified miR-21-5p to decrease significantly using RT-qPCR. In follow-up experiments, we found that miR-21-5p targets SKP2 to regulate osteoclast differentiation. In vivo, ovariectomized mice were used to simulate perimenopausal osteoporosis induced by estrogen deficiency, and miR-21-5p treatment inhibited bone resorption and maintained bone cortex and trabecular structure. These results suggest that miR-21-5p is a new therapeutic target for osteoporosis.

Following the publication of the original paper [1], one corresponding author was inadvertently missed.

Postmenopausal osteoporosis is initiated by estrogen withdrawal and is characterized mainly by overactivated osteoclastic bone resorption. Targeting TNF receptor-associated factor 6 (TRAF6) or its downstream signaling pathways to modulate osteoclast formation and function is an appealing strategy for osteoclast-related disorders. In the present study, we determined the effect of tomatidine, a steroidal alkaloid derived from Solanaceae, on the formation and function of receptor activator of NF-κB (RANK) ligand-induced osteoclasts and the underlying mechanism. Tomatidine inhibited osteoclast formation in a dose-dependent manner and decreased the expression of osteoclast marker genes. Actin ring formation and osteoclastic bone resorption were attenuated in the presence of tomatidine in vitro. Eight weeks after ovariectomy, tomatidine prevented estrogen deficiency-induced bone loss and restored the mechanical properties of the femur. At the molecular level, tomatidine abrogated phosphorylation of c-Jun N-terminal kinase (JNK)/p38, NF-κB, and protein kinase B (Akt) pathway proteins by suppressing RANK expression, inhibiting the binding of TRAF6 to RANK, and downregulating the osteoclastogenesis marker-related protein expression. In summary, these data demonstrated that tomatidine attenuated osteoclast formation and function by modulating multiple TRAF6-mediated pathways. Therefore, tomatidine could be a novel candidate for the treatment of osteoclast-related disorders, including osteoporosis.-Hu, B., Sun, X., Yang, Y., Ying, Z., Meng, J., Zhou, C., Jiang, G., Li, S., Wu, F., Zhao, X., Zhu, H., Wu, H., Cai, X., Shi, Z., Yan, S. Tomatidine suppresses osteoclastogenesis and mitigates estrogen deficiency-induced bone mass loss by modulating TRAF6-mediated signaling.

Objective Several studies have been performed to investigate the association between SMAD3 gene polymorphism and osteoarthritis (OA), but the results were inconclusive. This study aims to determine whether SMAD3 polymorphism is associated with risk of OA. Method A comprehensive literature search in PubMed, Embase, and ISI Web of Science for relevant studies was performed. After extracting data from eligible studies, we chose the fixed or random effect model according to the heterogeneity test. Estimation of publication bias and sensitivity analysis were conducted to confirm the stability of this meta-analysis. Results In total, 10 studies from 6 articles with 5093 OA patients and 5699 controls were enrolled in this meta-analysis. The combined results revealed significant association between SMAD3 rs12901499 polymorphism and the risk of OA (allele model: OR 1.21, 95% CI 1.07–1.38). Subgroup analysis revealed that G allele increased the risk of OA in Caucasians, but not in Asians (allele model: Caucasians: OR 1.31, 95% CI 1.18–1.44; Asians: OR 1.24, 95% CI 0.95–1.61). And the pooled results revealed significant association between SMAD3 rs12901499 polymorphism and both knee and hip OA (knee OA: OR 1.18, 95% CI 1.04–1.34; hip OA: OR 1.31, 95% CI 1.18–1.44). Conclusion The current meta-analysis revealed that the G variant of SMAD3 rs12901499 polymorphism increased the risk of OA in Caucasians. Further well-designed studies with larger sample size in different ethnic populations are required to confirm these results. Electronic supplementary material The online version of this article (10.1186/s13018-018-0939-2) contains supplementary material, which is available to authorized users.

As a chronic disease, osteoarthritis (OA) leads to the degradation of both cartilage and subchondral bone, its development being mediated by proinflammatory cytokines like interleukin-1β. In the present study, the anti-inflammatory effect of specnuezhenide (SPN) in OA and its underlying mechanism were studied in vitro and in vivo. The results showed that SPN decreases the expression of cartilage matrix-degrading enzymes and the activation of NF-κB and wnt/β-catenin signaling, and increases chondrocyte-specific gene expression in IL-1β-induced inflammation in chondrocytes. Furthermore, SPN treatment prevents the degeneration of both cartilage and subchondral bone in a rat model of OA. To the best of our knowledge, this study is the first to report that SPN decreases interleukin-1β-induced inflammation in rat chondrocytes by inhibiting the activation of the NF-κB and wnt/β-catenin pathways, and, thus, has therapeutic potential in the treatment of OA.

Osteolysis is an osteolytic lesion featured by enhanced osteoclast formation and potent bone erosion. Lacking of effective regimen for treatment of the pathological process highlights the importance of identifying agents that can suppress the differentiation and function of osteoclast. Artemether is a natural compound derived from Artemisia annua L. and it is popularized for the treatment of malaria. In present study, we demonstrated that artemether could suppress RANKL-induced osteoclastogenesis and expression of osteoclast marker genes such as tartrate-resistant acid phosphatase, cathepsin K, matrix metalloproteinase 9, nuclear factor of activated T-cell cytoplasmic 1, and dendritic cell-specific transmembrane protein. It inhibited the osteoclastic bone resorption in a dose-dependent manner in vitro. Furthermore, artemether attenuated RANKL-induced MAPKs (ERK, JNK, p-38) activity. In addition, we have showed that artemether was able to mitigate bone erosion in a murine model of LPS-induced inflammatory bone loss. Taken together, these findings suggest that artemether reduces inflammatory bone loss via inhibition of MAPKs activation during osteoclast differentiation, and it might be a potential candidate for the treatment of osteoclast-related disorders.

Spinel LiMn 2 O 4 cathode material has been synthesized by a spray-drying method for lithium ion batteries. During the entire process, the as-prepared powders were characterized using TGA/DTA, XRD, FTIR, SEM and TEM. The results showed that this method not only reduces the sintering time to 5 h at 750 °C, but also decreases the average particle size of LiMn 2 O 4 powders to the order of nanometers. The electrochemical performance of nanosized LiMn 2 O 4 was investigated by the galvanostatic charge–discharge tests. The data indicate that the nanosized LiMn 2 O 4 has a specific capacity of about 130 mA h g − 1 (1/5 C), and at higher rate (1 C), still has good cycling stability.