Roles of inflammatory and anabolic cytokines in cartilage metabolism: signals and multiple effectors converge upon MMP-13 regulation in osteoarthritis

Kaempferol inhibits interleukin‑1β stimulated matrix metalloproteinases by suppressing the MAPK‑associated ERK and P38 signaling pathways

Osteoarthritis (OA) is a common degenerative joint disease in older adults. A number of previous studies have demonstrated that natural flavonoids can serve as promising therapeutic drugs for OA. Kaempferol, a phytochemical ingredient mainly present in various fruits, has exhibited its prominent anti-inflammatory and antioxidant effects in numerous diseases. However, whether Kaempferol ameliorates the deterioration of arthritis remains to be elucidated. The aim of the present study was to investigate the therapeutic role of Kaempferol on OA in rat chondrocytes. The results revealed that Kaempferol significantly inhibited the interleukin (IL)-1β-induced protein expression of inflammatory mediators such as inducible nitric oxide synthase and cyclo-oxygenase-2. In addition, the common matrix degrading enzymes [matrix metalloproteinase (MMP)-1, MMP-3, MMP-13 and a disintegrin and metalloproteinase with thrombospondin motif-5] induced by IL-1β were also suppressed by Kaempferol, and consequently abolished the degradation of collagen II. Furthermore, the anti-inflammatory effect of Kaempferol was mediated by the inhibition of the mitogen activated protein kinase-associated extracellular signal-regulated kinase and P38 signaling pathways. These results collectively indicated that Kaempferol can potentially prevent OA development and serve as a novel pharmacological target in the treatment of OA.

Fetal articular cartilage regeneration versus adult fibrocartilaginous repair: secretome proteomics unravels molecular mechanisms in an ovine model

Osteoarthritis (OA), a degenerative joint disease characterized by progressive cartilage degeneration, is one of the leading causes of disability worldwide owing to the limited regenerative capacity of adult articular cartilage. Currently, there are no disease-modifying pharmacological or surgical therapies for OA. Fetal mammals, in contrast to adults, are capable of regenerating injured cartilage in the first two trimesters of gestation. A deeper understanding of the properties intrinsic to the response of fetal tissue to injury would allow us to modulate the way in which adult tissue responds to injury. In this study, we employed secretome proteomics to compare fetal and adult protein regulation in response to cartilage injury using an ovine cartilage defect model. The most relevant events comprised proteins associated with the immune response and inflammation, proteins specific for cartilage tissue and cartilage development, and proteins involved in cell growth and proliferation. Alarmins S100A8, S100A9 and S100A12 and coiled-coil domain containing 88A (CCDC88A), which are associated with inflammatory processes, were found to be significantly upregulated following injury in adult, but not in fetal animals. By contrast, cartilage-specific proteins like proteoglycan 4 were upregulated in response to injury only in fetal sheep postinjury. Our results demonstrate the power and relevance of the ovine fetal cartilage regeneration model presented here for the first time. The identification of previously unrecognized modulatory proteins that plausibly affect the healing process holds great promise for potential therapeutic interventions.

Summary: Secretome proteomics identifies differential regulation of inflammation modulators during fetal and adult articular cartilage defect healing, offering novel strategies for therapy.

Initial In Vitro Development of a Potassium-Based Intra-Articular Injection for Osteoarthritis

The long-term goal of this work is to develop a potassium (K⁺)-based intra-articular (IA) injection for osteoarthritis treatment. Within this context, the objectives of this study were to (1) demonstrate that hyperosmolar K⁺ solutions can suppress proinflammatory macrophage activation and (2) evaluate the therapeutic potential of a hyperosmolar K⁺ solution relative to a clinically utilized drug-based (methylprednisolone acetate [MPA]-a corticosteroid) or cell-based (human mesenchymal stem cell [hMSC]) IA injectable. A 3D in vitro model with poly(ethylene glycol) diacrylate hydrogels encapsulated with proinflammatory interferon-gamma (IFN)-stimulated macrophages (M(IFN)s) was utilized. Long-term changes in cell phenotype in response to short-term stimulation (i.e., mimicking an IA injection) were assessed following treatment with 80 mM K⁺ gluconate, hMSCs, or MPA. Addition of 80 mM K⁺ gluconate to culture media significantly reduced iNOS and TNF protein levels in M(IFN)s. Furthermore, short-term stimulation with K⁺ gluconate elicited a significant increase in the anti/proinflammatory cytokine profile in M(IFN)s, a response that is not noticed with either clinically utilized MPA or an hMSC injectable. Hyperosmolar K⁺ solutions are capable of attenuating proinflammatory macrophage activation. Moreover, when evaluated in an in vitro setting mimicking an IA injection, K⁺ performed significantly better than hMSCs or the corticosteroid MPA. Cumulatively, these results support further development and application of a K⁺-based IA injection toward osteoarthritis research.

SOST/Sclerostin Improves Posttraumatic Osteoarthritis and Inhibits MMP2/3 Expression After Injury

Patients with anterior cruciate ligament (ACL) rupture are two times as likely to develop posttraumatic osteoarthritis (PTOA). Annually, there are ∼900,000 knee injuries in the United States, which account for ∼12% of all osteoarthritis (OA) cases. PTOA leads to reduced physical activity, deconditioning of the musculoskeletal system, and in severe cases requires joint replacement to restore function. Therefore, treatments that would prevent cartilage degradation post-injury would provide attractive alternatives to surgery. Sclerostin (Sost), a Wnt antagonist and a potent negative regulator of bone formation, has recently been implicated in regulating chondrocyte function in OA. To determine whether elevated levels of Sost play a protective role in PTOA, we examined the progression of OA using a noninvasive tibial compression overload model in SOST transgenic (SOST^TG ) and knockout (Sost^-/- ) mice. Here we report that SOST^TG mice develop moderate OA and display significantly less advanced PTOA phenotype at 16 weeks post-injury compared with wild-type (WT) controls and Sost^-/- . In addition, SOST^TG built ∼50% and ∼65% less osteophyte volume than WT and Sost^-/- , respectively. Quantification of metalloproteinase (MMP) activity showed that SOST^TG had ∼2-fold less MMP activation than WT or Sost^-/- , and this was supported by a significant reduction in MMP2/3 protein levels, suggesting that elevated levels of SOST inhibit the activity of proteolytic enzymes known to degrade articular cartilage matrix. Furthermore, intra-articular administration of recombinant Sost protein, immediately post-injury, also significantly decreased MMP activity levels relative to PBS-treated controls, and Sost activation in response to injury was TNFα and NF-κB dependent. These results provide in vivo evidence that sclerostin functions as a protective molecule immediately after joint injury to prevent cartilage degradation. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Piceatannol inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes and ameliorates osteoarthritis in mice by activating Nrf2

Osteoarthritis (OA) is a complex process, to which an inflammatory environment contributes markedly. Piceatannol exerts anti-inflammatory effects on several diseases. In the current study, we explored the protective effects of piceatannol on the progression of OA and investigated its molecular target. In vitro, piceatannol not only attenuated the over-production of inflammatory mediators and cytokines-such as nitric oxide (NO), prostaglandin E2 (PGE₂), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6)-but also suppressed the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) at both the mRNA and protein levels. Piceatannol also decreased the expression of metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS5), which mediate extracellular matrix degradation. Mechanistically, we found that piceatannol inhibited IL-1β-induced nuclear factor kappa B (NF-κB) activation by activating the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway. Furthermore, piceatannol exerted protective effects in a mouse model of OA. Taken together, these findings indicate that piceatannol may be a potential therapeutic agent for OA.

Mithramycin A Alleviates Osteoarthritic Cartilage Destruction by Inhibiting HIF-2α Expression

Osteoarthritis (OA) is the most common and increasing joint disease worldwide. Current treatment for OA is limited to control of symptoms. The purpose of this study was to determine the effect of specificity protein 1 (SP1) inhibitor Mithramycin A (MitA) on chondrocyte catabolism and OA pathogenesis and to explore the underlying molecular mechanisms involving SP1 and other key factors that are critical for OA. Here, we show that MitA markedly inhibited expressions of matrix-degrading enzymes induced by pro-inflammatory cytokine interleukin-1β (IL-1β) in mouse primary chondrocytes. Intra-articular injection of MitA into mouse knee joint alleviated OA cartilage destruction induced by surgical destabilization of the medial meniscus (DMM). However, modulation of SP1 level in chondrocyte and mouse cartilage did not alter catabolic gene expression or cartilage integrity, respectively. Instead, MitA significantly impaired the expression of HIF-2α known to be critical for OA pathogenesis. Such reduction in expression of HIF-2α by MitA was caused by inhibition of NF-κB activation, at least in part. These results suggest that MitA can alleviate OA pathogenesis by suppressing NF-κB-HIF-2α pathway, thus providing insight into therapeutic strategy for OA.

Chondroprotective effects of aqueous extract of Anthriscus sylvestris leaves on osteoarthritis in vitro and in vivo through MAPKs and NF-κB signaling inhibition

Osteoarthritis (OA) is a common degenerative joint disease, characterized by cartilage degradation and inflammation, in the elderly population. Anthriscus sylvestris has been used in Korean traditional medicine and contains many polyphenolic compounds such as cynaroside and chlorogenic acid, which are major active components responsible for its antioxidant effect. In this study, we aimed to evaluate the chondroprotective effect of an aqueous extract of A. sylvestris leaves (AE-ASL) on OA, both in vitro and in vivo. Rat primary chondrocytes were pretreated with AE-ASL for 1 h before interleukin-1β (20 ng/mL) stimulation. The production of nitrite, PGE₂, aggrecan, and collagen type II were detected by Griess reagent and ELISAs. The mRNA levels of iNOS, COX-2, MMP-3, and MMP-13 were measured by RT-PCR. In addition, protein levels of iNOS, COX-2, MMP-3, MMP-13, ADAMTS-4, MAPKs, and NF-κB p65 subunit were measured by western blot analysis. Sulfated glycosaminoglycan (sGAGs) were detected by dimethylmethylene blue (DMMB) assay. During in vivo study, the effects of AE-ASL were evaluated for 8 weeks in a rat model of destabilization of the medial meniscus (DMM) surgery-induced OA. AE-ASL significantly inhibited expression of nitrite, iNOS, PGE₂, COX-2, MMP-3, MMP-13, and ADAMTS-4 in IL-1β-stimulated chondrocytes. Moreover, it decreased the IL-1β-induced degradation of aggrecan, collagen type II, and proteoglycan. In addition, AE-ASL suppressed IL-1β-induced phosphorylation of MAPKs and NF-κB p65 subunit translocation to nucleus. In vivo, AE-ASL inhibited DMM surgery-induced cartilage destruction and proteoglycan loss. Taken together, these results suggest that AE-ASL may be a potential therapeutic agent for the alleviation of OA progression.

Bioluminescence and second harmonic generation imaging reveal dynamic changes in the inflammatory and collagen landscape in early osteoarthritis

Osteoarthritis (OA) is a leading cause of chronic disability whose mechanism of pathogenesis is largely elusive. Local inflammation is thought to play a key role in OA progression, especially in injury-associated OA. While multiple inflammatory cytokines are detected, the timing and extent of overall inflammatory activities in early OA and the manner by which joint inflammation correlates with cartilage structural damage are still unclear. We induced OA via destabilization of the medial meniscus (DMM) in NFκB luciferase reporter mice, whose bioluminescent signal reflects the activity of NFκB, a central mediator of inflammation. Bioluminescence imaging data showed that DMM and sham control joints had a similar surge of inflammation at 1-week post-surgery, but the DMM joint exhibited a delay in resolution of inflammation in subsequent weeks. A similar trend was observed with synovitis, which we found to be mainly driven by synovial cell density and inflammatory infiltration rather than synovial lining thickness. Interestingly, an association between synovitis and collagen structural damage was observed in early OA. Using Second Harmonic Generation (SHG) imaging, we analyzed collagen fiber organization in articular cartilage. Zonal differences in collagen fiber thickness and organization were observed as soon as OA initiated after DMM surgery, and persisted over time. Even at 1-week post-surgery, the DMM joint showed a decrease in collagen fiber thickness in the deep zone and an increase in collagen fiber disorganization in the superficial zone. Since we were able detect and quantify collagen structural changes very early in OA development by SHG imaging, we concluded that SHG imaging is a highly sensitive tool to evaluate pathological changes in OA. In summary, this study uncovered a dynamic profile of inflammation and joint cartilage damage during OA initiation and development, providing novel insights into OA pathology.

Time-dependent changes in gene expression induced in vitro by interleukin-1β in equine articular cartilage

Osteoarthritis is an inflammatory and degenerative joint disease commonly affecting horses. To identify genes of relevance for cartilage pathology in osteoarthritis we studied the time-course effects of interleukin (IL)-1β on equine articular cartilage. Articular cartilage explants from the distal third metacarpal bone were collected postmortem from three horses without evidence of joint disease. The explants were stimulated with IL-1β for 27 days and global gene expression was measured by microarray. Gene expression was compared to that of unstimulated explants at days 3, 9, 15, 21 and 27. Release of inflammatory proteins was measured using Proximity Extension Assay. Stimulation with IL-1β led to time-dependent changes in gene expression related to inflammation, the extracellular matrix (ECM), and phenotypic alterations. Gene expression and protein release of cytokines, chemokines, and matrix-degrading enzymes increased in the stimulated explants. Collagen type II was downregulated from day 15, whereas other ECM molecules were downregulated earlier. In contrast molecules involved in ECM signaling (perlecan, chondroitin sulfate proteoglycan 4, and syndecan 4) were upregulated. At the late time points, genes related to a chondrogenic phenotype were downregulated, and genes related to a hypertrophic phenotype were upregulated, suggesting a transition towards hypertrophy later in the culturing period. The data suggest that this in vitro model mimics time course events of in vivo inflammation in OA and it may be valuable as an in vitro tool to test treatments and to study disease mechanisms.

Celecoxib-mediated reduction of prostanoid release in Hoffa's fat pad from donors with cartilage pathology results in an attenuated inflammatory phenotype

OBJECTIVE

The Hoffa's fat pad (HFP) is an intra-articular adipose tissue which is situated under and behind the patella. It contains immune cells next to adipocytes and secretes inflammatory factors during osteoarthritis (OA). In this study, we compared the release profile of prostanoids, which are involved in inflammation, of HFP from OA patients vs patients with a focal cartilage defect (CD) without evidence for OA on MRI and investigated the prostanoid modulatory anti-inflammatory action of celecoxib on HFP.

DESIGN

Prostanoid release was analyzed in conditioned medium of HFP explant cultures from 17 osteoarthritic patients and 12 CD patients, in the presence or absence of celecoxib. Furthermore, gene expression of COX enzymes and expression of genes indicative of a pro-inflammatory or anti-inflammatory phenotype of HFP was analyzed.

RESULTS

Prostanoid release by HFP from knee OA patients clustered in two subgroups with high and low prostanoid producers. HFP from high prostanoid producers released higher amounts of PGE₂, PGF_2α and PGD₂ compared to HFP from CD patients. PGE₂ release by OA HFP was positively associated with expression of genes known to be expressed by M1 macrophages, indicating a role for macrophages. Celecoxib modulated prostanoid release by HFP, and also modulated the inflammation ratio towards a more favorable anti-inflammatory M2 phenotype, most effectively in patients with higher prostanoid release profiles.

CONCLUSION

In knee OA patients with inflamed HFP's, celecoxib may exert positive effects in the knee joint via decreasing the release of prostanoids produced by the HFP and by favorably modulating the anti-inflammatory marker expression in HFP.

Elf3 Contributes to Cartilage Degradation in vivo in a Surgical Model of Post-Traumatic Osteoarthritis

The E-74 like factor 3 (ELF3) is a transcription factor induced by inflammatory factors in various cell types, including chondrocytes. ELF3 levels are elevated in human cartilage from patients with osteoarthritis (OA), and ELF3 contributes to the IL-1β-induced expression of genes encoding Mmp13, Nos2, and Ptgs2/Cox2 in chondrocytes in vitro. Here, we investigated the contribution of ELF3 to cartilage degradation in vivo, using a mouse model of OA. To this end, we generated mouse strains with cartilage-specific Elf3 knockout (Col2Cre:Elf3^f/f) and Comp-driven Tet-off-inducible Elf3 overexpression (TRE-Elf3:Comp-tTA). To evaluate the contribution of ELF3 to OA, we induced OA in 12-week-old Col2Cre:Elf3^f/f and 6-month-old TRE-Elf3:Comp-tTA male mice using the destabilization of the medial meniscus (DMM) model. The chondrocyte-specific deletion of Elf3 led to decreased levels of IL-1β- and DMM-induced Mmp13 and Nos2 mRNA in vitro and in vivo, respectively. Histological grading showed attenuation of cartilage loss in Elf3 knockout mice compared to wild type (WT) littermates at 8 and 12 weeks following DMM surgery that correlated with reduced collagenase activity. Accordingly, Elf3 overexpression led to increased cartilage degradation post-surgery compared to WT counterparts. Our results provide evidence that ELF3 is a central contributing factor for cartilage degradation in post-traumatic OA in vivo.

The role of inhibition by phosphocitrate and its analogue in chondrocyte differentiation and subchondral bone advance in Hartley guinea pigs

Phosphocitrate (PC) and its analogue, PC-β ethyl ester, inhibit articular cartilage degeneration in Hartley guinea pigs. However, the underlying molecular mechanisms remain unclear. The present study aimed to investigate the hypothesis that PC exerted its disease-modifying effect on osteoarthritis (OA), in part, by inhibiting a molecular program similar to that in the endochondral pathway of ossification. The results demonstrated that severe proteoglycan loss occurred in the superficial and middle zones, as well as in the calcified zone of articular cartilage in the Hartley guinea pigs. Subchondral bone advance was greater in the control Hartley guinea pigs compared with PC- or PC analogue-treated guinea pigs. Resorption of cartilage bars or islands and vascular invasion in the growth plate were also greater in the control guinea pigs compared with the PC- or PC analogue-treated guinea pigs. The levels of matrix metalloproteinase-13 and type X collagen within the articular cartilage and growth plate were significantly increased in the control guinea pigs compared with PC-treated guinea pigs (P<0.05). These results indicated that articular chondrocytes in Hartley guinea pigs exhibited a hypertrophic phenotype and recapitulated a developmental molecular program similar to the endochondral pathway of ossification. Activation of this molecular program resulted in resorption of calcified articular cartilage and subchondral bone advance. This suggests that PC and PC analogues exerted their OA disease-modifying activity, in part, by inhibiting this molecular program.

Interplay of Inflammatory Mediators with Epigenetics and Cartilage Modifications in Osteoarthritis

Osteoarthritis (OA), a degenerative disease of diarthrodial joints, is influenced by mechanical and inflammatory factors with aging, obesity, chronic injuries, and secondary diseases thought to be major factors driving the process of articular cartilage degeneration. Chondrocytes, the cellular component of cartilage, reside in an avascular environment and normally have limited potential to replicate. However, extrinsic factors such as injury to the joint or intrinsic alterations to the chondrocytes themselves can lead to an altered phenotype and development of OA. Synovial inflammation is also a pivotal element of the osteoarthritic, degenerative process: influx of pro-inflammatory cytokines and production of matrix metalloproteinases accelerate advanced cellular processes such as synovitis and cartilage damage. As well as a genetic input, recent data have highlighted epigenetic factors as contributing to disease. Studies conducted over the last decade have focused on three key aspects in OA; inflammation and the immune response, genome-wide association studies that have identified important genes undergoing epigenetic modifications, and finally how chondrocytes transform in their function during development and disease. Data highlighted here have identified critical inflammatory genes involved in OA and how these factors impact chondrocyte hypertrophy in the disease. This review also addresses key inflammatory factors in synovial inflammation, epigenetics, and chondrocyte fate, and how agents that inhibit epigenetic mechanisms like DNA methylation and histone modifications could aid in development of long-term treatment strategies for the disease.

Interaction with macrophages attenuates equine fibroblast-like synoviocyte ADAMTS5 (aggrecanase-2) gene expression following inflammatory stimulation

The joint synovium consists of a heterogeneous cell population, chiefly comprised of macrophages, and fibroblast-like synoviocytes (FLS). An inter-species co-culture model was developed to examine interactions between these cells. Equine FLS and the canine macrophage line DH82 were differentially labeled using fluorescent markers and results from direct co-culture compared with those from both indirect co-culture, and conditioned media experiments. The transcript expression of IL-1β, IL-6, ADAMTS4, and ADAMTS5 in each cell type were determined using species-specific qPCR assays. Lipopolysaccharide stimulation of EFLS rapidly increased IL-1β, IL-6, ADAMTS4, and ADAMTS5 mRNAs. The induction of ADAMTS5 was significantly reduced when equine FLS were cultured with DH82 cells directly or indirectly. Exposure of equine FLS to denatured conditioned media also significantly reduced ADAMTS5 induction. DH82 cells increased interleukin-1β expression substantially following LPS stimulation. However, knockdown of interleukin-1β in DH82 cells, or inhibition of NF-κB in equine FLS prior to co-culture did not change the inhibitory effect on equine FLS ADAMTS5 gene expression. This work indicates that macrophages can influence FLS gene expression through a soluble mediator, and modulate the expression of an enzyme critical in osteoarthritis pathology during inflammatory stimulation. © 2018 The Authors. Journal of Orthopaedic Research® Published by WileyPeriodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 9999:1-8, 2018.

MicroRNA-193b-3p regulates matrix metalloproteinase 19 expression in interleukin-1β-induced human chondrocytes

Micro(mi)RNAs are small, non-coding RNA molecules known to play a significant role in osteoarthritis (OA) initiation and development, and similar to matrix metalloproteinases (MMPs), they participate in cartilage degeneration and cleave multiple extracellular matrices. The aim of this study was to determine whether the expression of MMP-19 in interleukin (IL)-1β-induced human chondrocytes is directly regulated by miR-193b-3p. Expression levels of miR-193b-3p and MMP-19 in normal and osteoarthritis (OA) human cartilage, and interleukin-1 β (IL-1β)-induced human chondrocytes were determined by real-time polymerase chain reaction. Additionally, expression level of MMP-19 in IL-1β-induced human chondrocytes was estimated by Western blotting and immunohistochemistry analyses. The effect of miR-193b-3p on MMP-19 expression was evaluated using transient transfection of normal human chondrocytes with miR-193b-3p mimic or its antisense inhibitor (miR-193b-3p inhibitor), and siMMP-19. The putative binding site of miR-193b-3p in the 3'-untranslated region (UTR) of MMP-19 mRNA was validated by luciferase reporter assay. miR-193b-3p expression was reduced in OA cartilage compared to that in normal chondrocytes, while the opposite was observed for MMP-19. Upregulation of MMP-19 expression was correlated with downregulation of miR-193b-3p in IL-1β-stimulated normal chondrocytes. Increase in miR-193b-3p levels was associated with silencing of MMP-19. Overexpression of miR-193b-3p suppressed the activity of the reporter construct containing the 3'-UTR of human MMP-19 mRNA and inhibited the IL-1β-induced expression of MMP-19 and iNOS in chondrocytes, while treatment with miR-193b-3p inhibitor enhanced MMP-19 expression. MiR-193b-3p is an important regulator of MMP-19 in human chondrocytes and may relieve the inflammatory response in OA.

Spinacia oleracea extract attenuates disease progression and sub-chondral bone changes in monosodium iodoacetate-induced osteoarthritis in rats

Background

Spinacia oleracea is an important dietary vegetable in India and throughout the world and has many beneficial effects. It is cultivated globally. However, its effect on osteoarthritis that mainly targets the cartilage cells remains unknown. In this study we aimed to evaluate the anti-osteoarthritic and chondro-protective effects of SOE on chemically induced osteoarthritis (OA).

Methods

OA was induced by intra-patellar injection of monosodium iodoacetate (MIA) at the knee joint in rats. SOE was then given orally at 250 and 500 mg.kg^− 1 day^− 1 doses for 28 days to these rats. Anti-osteoarthritic potential of SOE was evaluated by micro-CT, mRNA and protein expression of pro-inflammatory and chondrogenic genes, clinically relevant biomarker’s and behavioural experiments.

Results

In vitro cell free and cell based assays indicated that SOE acts as a strong anti-oxidant and an anti-inflammatory agent. Histological analysis of knee joints at the end of the experiment by safranin-o and toluidine blue staining established its protective effect. Radiological data corroborated the findings with improvement in the joint space and irregularity of the articular and atrophied femoral condyles and tibial plateau. Micro-CT analysis of sub-chondral bone indicated that SOE had the ability to mitigate OA effects by increasing bone volume to tissue volume (BV/TV) which resulted in decrease of trabecular pattern factor (Tb.Pf) by more than 200%. SOE stimulated chondrogenic marker gene expression with reduction in pro-inflammatory markers. Purified compounds isolated from SOE exhibited increased Sox-9 and Col-II protein expression in articular chondrocytes. Serum and urine analysis indicated that SOE had the potential to down-regulate glutathione S-transferase (GST) activity, clinical markers of osteoarthritis like cartilage oligometric matrix protein (COMP) and CTX-II. Overall, this led to a significant improvement in locomotion and balancing activity in rats as assessed by Open-field and Rota rod test.

Conclusion

On the basis of in vitro and in vivo experiments performed with Spinacea oleracea extract we can deduce that SOE has the ability to alleviate the MIA induced deleterious effects.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2117-9) contains supplementary material, which is available to authorized users.

Zhuangguguanjie formulation protects articular cartilage from degeneration in joint instability-induced murine knee osteoarthritis

Zhuangguguanjie formulation (ZG) can provide noticeable relief from joint pain in patients suffering from knee osteoarthritis (OA). However, the underlying mechanism has not been fully described. Male C57BL/6 mice were administered either ZG or normal saline (NS) following surgical destabilization of the medial meniscus (DMM). At weeks 4, 6 and 8 (post-surgery), knee joints were harvested and assessed with Safranin-O staining. Blood serum was collected and tested. In vitro analysis was carried out to evaluate the effects of ZG on the expression of the OA-related genes. DMM mice indicated reduced cartilage destruction and lower blood serum biomarkers of OA (COMP1 and CTX-1) following ZG treatment. Moreover, the femoral condyle and tibial plateau histological scores were significantly reduced following ZG treatment of the DMM mice. ZG could markedly downregulate the expression of OA-related genes namely, ADAMTS5, MMP3 and MMP13, while it simultaneously upregulated collagen II as demonstrated by in vitro assays. Moreover, chondrocyte apoptosis was significantly decreased following ZG treatment. These results may be caused by the up-regulation of p-AKT expression levels, since the anti-apoptotic effects of ZG can be blocked by treatment with an AKT inhibitor. ZG is capable of preventing and/or reducing the progression of OA by inhibiting chondrocyte apoptosis via the p-AKT/Caspase 3 pathway.

Glucagon-like peptide-1 receptor regulates endoplasmic reticulum stress-induced apoptosis and the associated inflammatory response in chondrocytes and the progression of osteoarthritis in rat

Treatments for osteoarthritis (OA) are designed to restore chondrocyte function and inhibit cell apoptosis. Previous studies have shown that activation of the glucagon-like peptide-1 receptor (GLP-1R) leads to anti-inflammatory and anti-apoptotic effects. However, the role of GLP-1R in the pathological process of OA is unclear. In present work, we aimed to demonstrate the potential effect of GLP-1R on chondrocytes and elucidate its underlying mechanisms. We found that activation of GLP-1R with liraglutide could protect chondrocytes against endoplasmic reticulum stress and apoptosis induced by interleukin (IL)-1β or triglycerides (TGs). These effects were partially attenuated by GLP-1R small interfering RNA treatment. Moreover, inhibiting PI3K/Akt signaling abolished the protective effects of GLP-1R by increase the apoptosis activity and ER stress. Activating GLP-1R suppressed the nuclear factor kappa-B pathway, decreased the release of inflammatory mediators (IL-6, tumor necrosis factor α), and reduced matrix catabolism in TG-treated chondrocytes; these effects were abolished by GLP-1R knockdown. In the end, liraglutide attenuated rat cartilage degeneration in an OA model of knee joints in vivo. Our results indicate that GLP-1R is a therapeutic target for the treatment of OA, and that liraglutide could be a therapeutic candidate for this clinical application.

Emerging Players at the Intersection of Chondrocyte Loss of Maturational Arrest, Oxidative Stress, Senescence and Low-Grade Inflammation in Osteoarthritis

The prevalence of Osteoarthritis (OA) is increasing because of the progressive aging and unhealthy lifestyle. These risk factors trigger OA by removing constraints that keep the tightly regulated low turnover of the extracellular matrix (ECM) of articular cartilage, the correct chondrocyte phenotype, and the functionality of major homeostatic mechanisms, such as mitophagy, that allows for the clearance of dysfunctional mitochondria, preventing increased production of reactive oxygen species, oxidative stress, and senescence. After OA onset, the presence of ECM degradation products is perceived as a “danger” signal by the chondrocytes and the synovial macrophages that release alarmins with autocrine/paracrine effects on the same cells. Alarmins trigger innate immunity in the joint, with important systemic crosstalks that explain the beneficial effects of dietary interventions and improved lifestyle. Alarmins also boost low-grade inflammation: the release of inflammatory molecules and chemokines sustained by continuous triggering of NF-κB within an altered cellular setting that allows its higher transcriptional activity. Chemokines exert pleiotropic functions in OA, including the recruitment of inflammatory cells and the induction of ECM remodeling. Some chemokines have been successfully targeted to attenuate structural damage or pain in OA animal models. This represents a promising strategy for the future management of human OA.

Biochemical alterations in inflammatory reactive chondrocytes: evidence for intercellular network communication

Chondrocytes are effectively involved in the pathophysiological processes of inflammation in joints. They form cellular processes in the superficial layer of the articular cartilage and form gap junction coupled syncytium to facilitate cell-to-cell communication. However, very little is known about their physiological cellular identity and communication. The aim with the present work is to evaluate the physiological behavior after stimulation with the inflammatory inducers interleukin-1β and lipopolysaccharide. The cytoskeleton integrity and intracellular Ca²⁺ release were assessed as indicators of inflammatory state. Cytoskeleton integrity was analyzed through cartilage oligomeric matrix protein and actin labeling with an Alexa 488-conjugated phalloidin probe. Ca²⁺ responses were assessed through the Ca²⁺ sensitive fluorophore Fura-2/AM. Western blot analyses of several inflammatory markers were performed. The results show reorganization of the actin filaments. Glutamate, 5-hydoxytryptamine, and ATP evoked intracellular Ca²⁺ release changed from single peaks to oscillations after inflammatory induction in the chondrocytes. The expression of toll-like receptor 4, the glutamate transporters GLAST and GLT-1, and the matrix metalloproteinase-13 increased. This work demonstrates that chondrocytes are a key part in conditions that lead to inflammation in the cartilage. The inflammatory inducers modulate the cytoskeleton, the Ca²⁺ signaling, and several inflammatory parameters. In conclusion, our data show that the cellular responses to inflammatory insults from healthy and inflammatory chondrocytes resemble those previously observed in astrocyte and cardiac fibroblasts networks.

Low-intensity vibration increases cartilage thickness in obese mice

Obesity is associated with an elevated risk of osteoarthritis (OA). We examined here whether high fat diet administered in young mice, compromised the attainment of articular cartilage thickness. Further, we sought to determine if low-intensity vibration (LIV) could protect the retention of articular cartilage in a mouse model of diet-induced obesity. Five-week-old, male, C57BL/6 mice were separated into three groups (n = 10): Regular diet (RD), High fat diet (HF), and HF + LIV (HFv; 90 Hz, 0.2g, 30 min/d, 5 d/w) administered for 6 weeks. Additionally, an extended HF diet study was run for 6 months (LIV at 15 m/d). Articular cartilage and subchondral bone morphology, and sulfated GAG content were quantified using contrast agent enhanced μCT and histology. Gene expression within femoral condyles was quantified using real-time polymerase chain reaction. Contrary to our hypothesis, HF cartilage thickness was not statistically different from RD. However, LIV increased cartilage thickness compared to HF, and the elevated thickness was maintained when diet and LIV were extended into adulthood. RT-PCR analysis showed a reduction of aggrecan expression with high fat diet, while application of LIV reduced the expression of degradative MMP-13. Further, long-term HF diet resulted in subchondral bone thickening, compared to RD, providing early evidence of OA pathology-LIV suppressed the thickening, such that levels were not significantly different from RD. These data suggest that dynamic loading, via LIV, protected the retention of cartilage thickness, potentially resulting in joint surfaces better suited to endure the risks of elevated loading that parallel obesity. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:751-759, 2018.

Inflammation-induced transgene expression in genetically engineered equine mesenchymal stem cells

BACKGROUND

Osteoarthritis, a chronic and progressive degenerative joint disorder, ranks amongst the top five causes of disability. Given the high incidence, associated socioeconomic costs and the absence of effective disease-modifying therapies of osteoarthritis, cell-based treatments offer a promising new approach. Owing to their paracrine, differentiation and self-renewal abilities, mesenchymal stem cells (MSCs) have great potential for regenerative medicine, which might be further enhanced by targeted gene therapy. Hence, the development of systems allowing transgene expression, particularly when regulated by natural disease-dependent occuring substances, is of high interest.

METHODS

Bone marrow-isolated equine MSCs were stably transduced with an HIV-1 based lentiviral vector expressing the luciferase gene under control of an inducible nuclear factor κB (NFκB)-responsive promoter. Marker gene expression was analysed by determining luciferase activity in transduced cells stimulated with different concentrations of interleukin (IL)-1β or tumour necrosis factor (TNF)α.

RESULTS

A dose-dependent increase in luciferase expression was observed in transduced MSCs upon cytokine stimulation. The induction effect was more potent in cells treated with TNFα compared to those treated with IL-1β. Maximum transgene expression was obtained after 48 h of stimulation and the same time was necessary to return to baseline luciferase expression levels after withdrawal of the stimulus. Repeated cycles of induction allowed on-off modulation of transgene expression without becoming refractory to induction. The NFκB-responsive promoter retained its inducibility also in chondrogenically differentiated MSC/Luc cells.

CONCLUSIONS

The results of the present study demonstrate that on demand transgene expression from the NFκB-responsive promoter using naturally occurring inflammatory cytokines can be induced in undifferentiated and chondrogenically differentiated equine MSCs. Copyright © 2016 John Wiley & Sons, Ltd.

Calcium-phosphate complex increased during subchondral bone remodeling affects earlystage osteoarthritis

An activation of osteoclasts and subchondral bone remodeling is a major histologic feature of early-stage osteoarthritis (OA), which can be accompanied by an increase of calcium (Ca) and phosphate (Pi) level in the subchondral milieu. Considering articular cartilage gets most of nutrition from subchondral bone by diffusion, these micro-environmental changes in subchondral bone can affect the physiology of articular chondrocytes. Here, we have shown that Ca is increased and co-localized with Pi in articular cartilage of early-stage OA. The Ca-Pi complex increased the production of MMP-3 and MMP-13 in the hypertrophic chondrocytes, which was dependent on nuclear factor-kappa B (NF-kB), p38 and extracellular signal-regulated kinase (Erk) 1/2 mitogen-activated protein (MAP) kinase and Signal transducer and activator of transcription 3 (STAT3) signaling. The Ca-Pi complexes increased the expression of endocytosis markers, and the inhibition of the formation of the Ca-Pi complex ameliorated the Ca-Pi complex-mediated increases of MMPs expression in hypertrophic chondrocytes. Our data provide insight regarding the Ca-Pi complex as a potential catabolic mediator in the subchondral milieu and support the pathogenic role of subchondral bone in the early stages of cartilage degeneration.

Osteoarthritis: Trauma vs Disease

Osteoarthritis (OA) is the most prevalent joint disease characterized by pain and degenerative lesions of the cartilage, subchondral bone, and other joint tissues. The causes of OA remain incompletely understood. Over the years, it has become recognized that OA is a multifactorial disease. In particular, aging and trauma are the main risk factors identified for the development of OA; however, other factors such as genetic predisposition, obesity, inflammation, gender and hormones, or metabolic syndrome contribute to OA development and lead to a more severe outcome. While this disease mainly affects people older than 60 years, OA developed after joint trauma affects all range ages and has a particular impact on young individuals and people who have highest levels of physical activity such as athletes. Traumatic injury to the joint often results in joint instability or intra-articular fractures which lead to posttraumatic osteoarthritis (PTOA). In response to injury, several molecular mechanisms are activated, increasing the production and activation of different factors that contribute to the progression of OA.In this chapter, we have focused on the interactions and contribution of the multiple factors involved in joint destruction and progression of OA. In addition, we overview the main changes and molecular mechanisms related to OA pathogenesis.

Clinical Outcomes of Knee Osteoarthritis Treated With an Autologous Protein Solution Injection: A 1-Year Pilot Double-Blinded Randomized Controlled Trial

BACKGROUND

Osteoarthritis (OA) is a debilitating disease resulting in substantial pain and functional limitations. A novel blood derivative has been developed to concentrate both growth factors and antagonists of inflammatory cytokines, with promising preliminary findings in terms of safety profile and clinical improvement.

PURPOSE

To investigate if one intra-articular injection of autologous protein solution (APS) can reduce pain and improve function in patients affected by knee OA in a multicenter, randomized, double-blind, saline-controlled study.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

Forty-six patients with unilateral knee OA (Kellgren-Lawrence 2 or 3) were randomized into the APS group (n = 31), which received a single ultrasound-guided injection of APS, and the saline (control) group (n = 15), which received a single saline injection. Patient-reported outcomes and adverse events were collected at 2 weeks and at 1, 3, 6, and 12 months through visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee injury and Osteoarthritis Outcome Score (KOOS), Short Form-36 (SF-36), Clinical Global Impression of Severity/Change (CGI-S/C), Patient Global Impression of Severity/Change (PGI-S/C), and Outcome Measures in Rheumatology-Osteoarthritis Research Society International (OMERACT-OARSI) responder rate. Imaging evaluation was also performed with radiograph and magnetic resonance imaging (MRI) before and after treatment (12 months and 3 and 12 months, respectively).

RESULTS

The safety profile was positive, with no significant differences in frequency and severity of adverse events between groups. The improvement from baseline to 2 weeks and to 1, 3, and 6 months was similar between treatments. At 12 months, improvement in WOMAC pain score was 65% in the APS group and 41% in the saline group ( P = .02). There were no significant differences in VAS pain improvement between groups. At 12 months, APS group showed improved SF-36 Bodily Pain subscale ( P = .0085) and Role Emotional Health subscale ( P = .0410), as well as CGI-C values ( P = .01) compared with saline control. Significant differences between groups were detected in change from baseline to 12 months in bone marrow lesion size as assessed on MRI and osteophytes in the central zone of the lateral femoral condyle, both in favor of the APS group ( P = .041 and P = .032, respectively). There were no significant differences between APS and control groups in other measured secondary endpoints.

CONCLUSION

This study provides evidence to support the safety and clinical improvement at 1-year follow-up of a single intra-articular injection of APS in patients affected by knee OA. Treatment with APS or a saline injection provided significant pain relief over the course of the study with differences becoming apparent at between 6 and 12 months after treatment.

TRIAL REGISTRATION

NCT02138890 ( ClinicalTrials.gov identifier).

Downregulating PI3K/Akt/NF-κB signaling with allicin for ameliorating the progression of osteoarthritis:in vitroandvivostudies

A schematic illustration of the potential protective effects of allicin on osteoarthritis development.

Modulation of Gene Expression in Infrapatellar Fat Pad-Derived Mesenchymal Stem Cells in Osteoarthritis

Aim In the osteoarthritis (OA) disease, all structures of the joint are involved. The infrapatellar Hoffa fat pad is rich in macrophages and granulocytes, which also represents a source of adipose mesenchymal progenitor cells (ASC) cells. In our study, we analyze how OA affects the ability of ASC-derived from Hoffa's fat pad to differentiate into chondrocytes. Material and methodology We took knee Hoffa's pad samples and adipose tissue from the proximal thigh from 6 patients diagnosed with severe OA and from another 6 patients with an anterior cruciate ligament (ACL) rupture without OA. From all the patients, we took subcutaneous adipose tissue from the thigh, as the control group. Samples of synovial fluid (SF) were also extracted. The gene expression was analyzed by real-time quantitative polymerase chain reaction. Results PTH1R and MMP13 expression during chondrogenic differentiation were similar between OA and ACL groups, while the expression of OPG, FGF2, TGFβ, MMP3 were significantly lower in the OA group. Exposure of differentiated ASC to OA SF induced an increase in the expression of OPG, PTH1R, and MMP13 and a decrease in the expression of FGF2 in cell culture of the ACL group. However, expression of none of these factors was altered by the OA synovial fluid in ASC cells of the OA group. Conclusion OA of the knee also affects the mesenchymal stem cells of Hoffa fat, suggesting that Hoffa fat is a new actor in the OA degenerative process that can contribute to the origin, onset, and progression of the disease.

Inflammatory cytokine response is greater in acute tibial plafond fractures than acute tibial plateau fractures

The purpose of the study was to compare the inflammatory cytokine and matrix metalloproteinase (MMP) concentrations in synovial fluid after acute plafond fracture with acute tibial plateau fracture. Between December 2011 and August 2014, we prospectively enrolled patients with acute tibial plateau and plafond fractures. Synovial fluid aspirations were obtained from injured and uninjured joints. The concentrations of IL-1β, IL-1RA, IL-6, IL-8, IL-10, MCP-1, TNF-α, MMP-1, -3, -9, -10, -12, and -13 were quantified using multiplex assays. A Bonferroni correction was used so that the adjusted alpha level for significance was p < 0.004. We enrolled 45 tibial plateau fractures and 19 plafond fractures. Mean patient age was 42 years (range, 20-60) and 64% were male patients. There were 24 low-energy (OTA 41B) plateau fractures and eight low-energy (OTA 43B) plafond fractures. There were 21 high-energy (6 OTA 41B3 and 15 OTA 41C) plateau fractures and 11 high-energy (OTA43C) plafond fractures. All cytokines and MMPs except MMP-13 were significantly elevated in plafond fractures compared to uninjured ankles. When comparing acutely injured joints, IL-8 (p < 0.001), IL-1β (p = 0.002), and MMP-12 (p = 0.001) were significantly higher in plafond fractures compared to plateau fractures. Concentrations of IL-1RA (p = 0.008) and MCP-1 (p = 0.005) were higher in plafond fractures, and MMP-10 (p = 0.01) was higher in plateau fractures, but these differences did not reach significance. In conclusion, several cytokines and MMPs were significantly elevated in acute plafond fractures as compared to acute tibial plateau fractures. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2613-2619, 2017.

New insights on the MMP-13 regulatory network in the pathogenesis of early osteoarthritis

Osteoarthritis (OA) is the most common joint disorder and affects approximately half of the aged population. Current treatments for OA are largely palliative until the articular cartilage has been deeply damaged and irreversible morphological changes appear. Thus, effective methods are needed for diagnosing and monitoring the progression of OA during its early stages when therapeutic drugs or biological agents are most likely to be effective. Various proteinases involved in articular cartilage degeneration in pre-OA conditions, which may represent the earliest reversible measurable changes, are considered diagnostic and therapeutic targets for early OA. Of these proteinases, matrix metalloproteinase 13 (MMP-13) has received the most attention, because it is a central node in the cartilage degradation network. In this review, we highlight the main MMP-13-related changes in OA chondrocytes, including alterations in the activity and expression level of MMP-13 by upstream regulatory factors, DNA methylation, various non-coding RNAs (ncRNAs), and autophagy. Because MMP-13 and its regulatory networks are suitable targets for the development of effective early treatment strategies for OA, we discuss the specific targets of MMP-13, including upstream regulatory proteins, DNA methylation, non-coding RNAs, and autophagy-related proteins of MMP-13, and their therapeutic potential to inhibit the development of OA. Moreover, the various entities mentioned in this review might be useful as early biomarkers and for personalized approaches to disease prevention and treatment by improving the phenotyping of early OA patients.

Panax quinquefolium saponin inhibits endoplasmic reticulum stress-induced apoptosis and the associated inflammatory response in chondrocytes and attenuates the progression of osteoarthritis in rat

Treatments for osteoarthritis (OA) seek to restore chondrocyte function and inhibit cell apoptosis. Panax quinquefolium saponin (PQS) is the major active ingredient of Radix panacis quinquefolii (American ginseng), and has been demonstrated to exert anti-inflammatory and anti-apoptotic effects in various diseases. However, any potential effect of PQS on the pathological process of OA remains unclear. This work aimed to explore the role of PQS in chondrocytes and to clarify its potential mechanisms. We showed that PQS treatment could protect chondrocytes against endoplasmic reticulum (ER) stress and associated apoptosis induced by interleukin (IL)-1β. Also, PQS further attenuated triglyceride (TG)-induced ER stress and associated apoptosis. Moreover, PQS may inhibit the ER stress-activated NF-κB pathway and associated inflammatory response in chondrocytes. Finally, PQS abolished rat cartilage degeneration in an in-vivo OA model of the knee joint. Our results indicate that PQS may be a potential novel treatment for OA.

Histopathological assessment of primary osteoarthritic knees in large patient cohort reveal the possibility of several potential patterns of osteoarthritis initiation

OBJECTIVE

The two main objectives of the study include (1) Test the hypothesis that the lateral femoral condyle (LFC) in patients with primary OA and varus knees undergoing total knee arthroplasty (TKA) can be used as a model to better characterize varying histological features of human OA, (2) Correlate characteristic OA features using the established histopathological scoring systems (HHGS and OARSI) to understand potential histopathological patterns of OA initiation.

DESIGN

Two osteochondral specimens (4×4×8mm) were collected from fifty patient's LFC at the time of TKA (total 100 specimens), who presented preserved lateral knee compartment with joint space width>2mm. Three independent readers graded the sections on three different occasions using HHGS and OARSI systems. The correlation between individual parameters of the two scoring systems and their inter- and intra-reader variability, reliability and reproducibility were estimated.

RESULTS

All samples in this cohort showed abnormal histopathological features. Total histopathological scores of the LFC ranged from HHGS median=4.6 (range=0 to 11), and OARSI median=5.2 (range=0 to 19.5). The four individual sub-items of HHGS scoring system (structure, cells, safraninO staining, tidemark) were weakly correlated, with the correlation between structure and cellularity being the strongest (r=0.40). Both the scoring systems had similar repeatability and reproducibility coefficients of<21%.

CONCLUSIONS

OA changes in the LFC are not confined to any one region, and maybe seen in different regions of cartilage, tidemark, subchondral bone, and/or the marrow space vascularity. These variations may point to the possibility of several potential patterns of initiation in OA.

Danshen attenuates cartilage injuries in osteoarthritis in vivo and in vitro by activating JAK2/STAT3 and AKT pathways

Articular cartilage degradation is a main feature of osteoarthritis (OA). The effects of Danshen, a traditional Chinese herb, in mitigating cartilage damage have been reported before. This study was conducted to investigate the effects of Danshen on cartilage injuries in OA. Rabbit OA models were established by surgical destabilization of the medial meniscus and the anterior and posterior cruciate ligaments in the left knee joint. Injection of Danshen into the articular cavity attenuated OA cartilage destruction in vivo. The levels of phosphorylated Janus kinase 2 (JAK2) and phosphorylated signal transducer and activator of transcription 3 (STAT3) were decreased in osteoarthritic cartilage, while they were rescued upon Danshen treatment. Furthermore, chondrocytes isolated from normal rabbit cartilage were exposed to 2 mM sodium nitroprusside (SNP) to establish an OA model in vitro. We found that the oxidative stress and chondrocyte apoptosis induced by SNP were suppressed by Danshen. The phosphorylation levels of JAK2 and STAT3 were decreased in response to SNP treatment, whereas they were rescued by Danshen. Additionally, AG490, a specific JAK2 inhibitor, counteracted the anti-apoptotic effect of Danshen. The phosphorylation level of protein kinase B (AKT) was also altered in response to SNP and reversed by Danshen. The anti-apoptotic effect of Danshen was counteracted by AKT pathway inhibitor LY194002. Taken together, Danshen attenuates OA cartilage destruction by regulating the JAK2/STAT3 and AKT signaling pathways.

Effects of baicalein on IL-1β-induced inflammation and apoptosis in rat articular chondrocytes

In osteoarthritis (OA), activated synoviocytes and articular chondrocytes produce pro-inflammatory cytokines, such as IL-1β, that promote chondrocyte apoptosis and activate the NF-κB signaling pathway to induce catabolic factors. In this study, we examined the anti-inflammatory and anti-apoptotic effect of baicalein on IL-1β signaling and NF-κB-regulated gene products in rat chondrocytes. Rat chondrocytes were pretreated with 10 ng/ml IL-1β for 24 h and then co-treated with 10 ng/ml IL-1β and 50 μM baicalein for 0, 12, 24, 36 and 48h. The expression levels of poly(ADP-ribose) polymerase (PARP), Bcl-2, caspase-3, matrix metalloproteinase (MMP)-9, MMP-3, cyclooxygenase (COX)-2 and SOX-9 were detected by Western blot and quantitative reverse transcription-PCR (qPCR). The effects of baicalein on the translocation and phosphorylation of the NF-κB system were studied by Western blotting and immunofluorescence. Baicalein stimulated the expression of anti-apoptotic genes and reduced the pro-apoptotic and pro-inflammatory gene products in chondrocytes. Baicalein promoted SOX-9 expression in a time-dependent manner in chondrocytes. Baicalein inhibited the NF-κB activation that was induced by IL-1β in a time-dependent manner in chondrocytes. Our results suggest that the anti-inflammatory and anti-apoptotic effects of baicalein are mediated through the inhibition of the translocation of phosphorylated p65 to the nucleus.

Isoliquiritigenin suppresses IL-1β induced apoptosis and inflammation in chondrocyte-like ATDC5 cells by inhibiting NF-κB and exerts chondroprotective effects on a mouse model of anterior cruciate ligament transection

Isoliquiritigenin (ISL), a natural flavonoid extracted from licorice, has been demonstrated to exert attenuation of the nuclear factor-κB (NF-κB) signaling pathway and anti-inflammatory activity in a wide variety of cells. In the present study, the authors first evaluated the effects of ISL on cartilage degeneration in interleukin-1β (IL-1β)-stimulated chondrocyte-like ATDC5 cells and in a mouse model of osteoarthritis (OA). The data of a cell counting kit-8 and flow cytometry assay indicated that ISL suppressed the inhibitory effect of IL-1β on cell viability. The mRNA and protein expression levels of cyclooxygenase-2 and matrix metalloproteinase-13 were significantly decreased, while the expression of collagen II was increased, as indicated by RT-qPCR and western blot analysis following the chondrocyte-like ATDC5 cells were co-intervened with IL-1β and ISL for 48 h. Also, ISL attenuated protein expressions level of pro-apoptotic Bax, cleaved-caspase-3 and cleaved-caspase-9 and promoted expression of anti-apoptotic Bcl-2. Moreover, ISL inhibited NF-κB p65 phosphorylation induced by IL-1β. In addition, ISL also increased improved the thickness of hyaline cartilage and the production of proteoglycans in the cartilage matrix in a mouse OA model. These results indicated that ISL exerted anti-inflammatory and anti-apoptotic effects on IL-1β-stimulated chondrocyte-like ATDC5 cells, which may be associated with the downregulation of the NF-κB signaling pathway. In this way, the data supported the conclusion that ISL may be a novel potential preventive agent suitable for use in OA therapy.

Salivary MMP-13 gender differences in periodontitis: A cross-sectional study from Sweden

We investigated serum and saliva concentrations of matrix metalloproteinases, MMP-8, MMP-9, and MMP-13, and their tissue inhibitor TIMP-1, in a group of patients with and without periodontitis from Sweden. The hypothesis was that these biomarkers are higher in the periodontitis patients. Ninety patients participated in this cross-sectional study. Fifty-one patients had periodontitis whereas 39 were periodontally healthy. Saliva and serum samples were analyzed with immunofluorometric, enzyme-linked immunosorbent assay and western blot. Results were statistically analyzed with independent t test, Mann-Whitney U test, Bonferroni corrections, and regression analyses. MMP-13 was not detected in serum, but in saliva, higher values were found among the periodontally healthy compared with periodontitis subjects (0.32 ± 0.26 vs. 0.21 ± 0.23 ng/ml, p < .05). Female gender and clinical attachment loss were the explanatory factors for higher salivary MMP-13 values with odds ratio 3.08 (95% confidence interval [1.17, 8.11]) and 3.57 (95% confidence interval [1.08, 11.82]), respectively. No statistically significant differences between groups were found in serum and saliva values of MMP-8, MMP-9, and TIMP-1. Contrary to our hypothesis, no statistically significant differences between patients with and without periodontitis were seen in MMP-8, MMP-9, and TIMP-1 values. However, higher MMP-13 concentrations in saliva were associated with female gender and higher clinical attachment loss. Metabolism of MMP-13 may thus have some gender implications in periodontitis.

Saikosaponin A inhibits IL-1β-induced inflammatory mediators in human osteoarthritis chondrocytes by activating LXRα

Saikosaponin a (SSa), one of the main active components of Bupleurum falcatum, has been reported to have anti-inflammatory effect. In the present study, we investigated the anti-inflammatory effect of SSa on IL-1β-stimulated human osteoarthritis chondrocytes. The cells were pretreated with SSa 12 h before IL-1β treatment. The production of PGE2 and NO were detected by ELISA and Griess method. The levels of MMP1, MMP3, and MMP13 were measured by ELISA and qRT-PCR. The expression of NF-κB and LXRα were tested by western blot analysis. The results showed that SSa inhibited IL-1β-induced PGE2 and NO production in a concentration-dependent manner. SSa also suppressed IL-1β-induced MMP1, MMP3, and MMP13 production. Furthermore, SSa significantly attenuated IL-1β-induced phosphorylation levels of NF-κB p65 and IκBα. SSa also up-regulated the expression of LXRα. The inhibition of SSa on PGE2, NO, MMP1, MMP3, and MMP13 production were reversed by LXRα siRNA or GGPP, the inhibitor of LXRα. In conclusion, our results demonstrated that SSa inhibited inflammatory responses in human chondrocytes in vitro. SSa might be a potential therapeutic drug for osteoarthritis.

Glycogen Synthase Kinase-3β Inhibition Links Mitochondrial Dysfunction, Extracellular Matrix Remodelling and Terminal Differentiation in Chondrocytes

Following inflammatory stimuli, GSK3 inhibition functions as a hub with pleiotropic effects leading to cartilage degradation. However, little is known about the effects triggered by its direct inhibition as well as the effects on mitochondrial pathology, that contributes to osteoarthritis pathogenesis. To this aim we assessed the molecular mechanisms triggered by GSK3β inactivating stimuli on 3-D (micromass) cultures of human articular chondrocytes. Stimuli were delivered either at micromass seeding (long term) or after maturation (short term) to explore “late” effects on terminal differentiation or “early” mitochondrial effects, respectively. GSK3β inhibition significantly enhanced mitochondrial oxidative stress and damage and endochondral ossification based on increased nuclear translocation of Runx-2 and β-catenin, calcium deposition, cell death and enhanced remodelling of the extracellular matrix as demonstrated by the increased collagenolytic activity of supernatants, despite unmodified (MMP-1) or even reduced (MMP-13) collagenase gene/protein expression. Molecular dissection of the underlying mechanisms showed that GSK3β inhibition achieved with pharmacological/silencing strategies impacted on the control of collagenolytic activity, via both decreased inhibition (reduced TIMP-3) and increased activation (increased MMP-10 and MMP-14). To conclude, the inhibition of GSK3β enhances terminal differentiation via concerted effects on ECM and therefore its activity represents a tool to keep articular cartilage homeostasis.

Cartilage matrix remodelling differs by disease state and joint type

Dramatic alterations in mechanical properties have been documented for osteoarthritic (OA) cartilage. However, the matrix composition underlying these changes has not been mapped and their aetiology is not entirely understood. We hypothesised that an understanding of the cartilage matrix heterogeneity could provide insights into the origin of these OA-related alterations. We generated serial transverse cryo sections for 7 different cartilage conditions: 2 joint sites (knee and hip), 2 disease states (healthy and OA) and 3 tissue depths (superficial, middle and deep). By laser capture microscopy, we acquired ~200 cartilage matrix specimens from territorial (T) and interterritorial (IT) regions for all 7 conditions. A standardised matrix area was collected for each condition for a total of 0.02 ± 0.001 mm3 (corresponding to 20 µg of tissue) from a total of 4800 specimens. Extracted proteins were analysed for abundance by targeted proteomics. For most proteins, a lower IT/T ratio was observed for the OA disease state and knee joint type. A major cause of the altered IT/T ratios was the decreased protein abundance in IT regions. The collagenase-derived type III collagen neo-epitope, indicative of collagen proteolysis, was significantly more abundant in OA cartilage. In addition, it was enriched on average of 1.45-fold in IT relative to T matrix. These results were consistent with an elevated proteolysis in IT regions of OA cartilage, due to degenerative influences originating from synovial tissue and/or produced locally by chondrocytes. In addition, they offered direct evidence for dynamic remodelling of cartilage and provided a cogent biochemical template for understanding the alterations of matrix mechanical properties.

Articular cartilage degradation is prevented by tanshinone IIA through inhibiting apoptosis and the expression of inflammatory cytokines

The present study aimed to investigate the effect of tanshinone IIA on the degradation of articular cartilage in a rat model of osteoarthritis (OA). The OA rat model was established by anterior cruciate ligament transection (ACLT) and medial meniscus resection (MMx). The animals were treated for 28 days with 0.25‑0.5 mg/kg doses of tanshinone IIA following ACLT + MMx. The knee joints of the rats in the ACLT + MMx group exhibited marked alterations in articular cartilage histopathology and higher Mankin scores, compared with those in the normal group. Tanshinone IIA treatment at a dose of 0.5 mg/kg significantly inhibited cartilage degradation and improved Mankin scores in the OA rat model (P<0.002). Tanshinone IIA treatment completely inhibited the ACLT + MMx‑induced accumulation of inflammatory cells and disintegration of synovial lining in the rats. An increase in the dose of tanshinone IIA between 0.25 and 0.5 mg/kg reduced the proportion of apoptotic chrondrocytes from 41 to 2% on day 29. Treatment of the rats in the ACLT + MMx group with 0.5 mg/kg doses of tanshinone IIA markedly inhibited the expression level of matrix metalloproteinase and increased the expression of tissue inhibitor of metalloproteinase in the rat articular cartilage tissues. Tanshinone IIA treatment significantly reduced the levels of inflammatory cytokines, including interleukin‑1β, tumor necrosis factor‑α and nitric oxide in rat serum samples. The protein expression levels of bone morphogenetic protein and transforming growth factor‑β were significantly increased by tanshinone IIA in the ACLT + MMx rats. Therefore, tanshinone IIA inhibited articular cartilage degradation through inhibition of apoptosis and expression levels of inflammatory cytokines, offering potential for use in the treatment of OA.

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

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

Knockdown of PRMT1 suppresses IL-1β-induced cartilage degradation and inflammatory responses in human chondrocytes through Gli1-mediated Hedgehog signaling pathway

Osteoarthritis (OA) is characterized by articular cartilage degradation and joint inflammation. The purpose of the present study is to elucidate the role of the specific function of PRMT1 in chondrocytes and its association with the pathophysiology of OA. We observed that the expression of PRMT1 was apparently upregulated in OA cartilage, as well as in chondrocytes stimulated with IL-1β. Additionally, knockdown of PRMT1 suppressed interleukin 1 beta (IL-1β)-induced extracellular matrix (ECM) metabolic imbalance by regulating the expression of MMP-13, ADAMTS-5, COL2A1, and ACAN. Furthermore, silencing of PRMT1 dramatically declined the production of prostaglandin E2 (PGE2) and nitric oxide as well as the level of pro-inflammatory cytokine IL-6 and TNF-α. Mechanistic analyses further revealed that IL-1β-induced activation of the Hedgehog/Gli-1 signaling is suppressed upon PRMT1 knockdown. However, the effects of inhibition of PRMT1-mediated IL-1β-induced cartilage matrix degradation and inflammatory response in OA chondrocytes were obviously abolished by Hedgehog agonist Purmorphamine (Pur). Our data collectively suggest that silencing of PRMT1 exerts anti-catabolic and anti-inflammatory effects on IL-1β-induced chondrocytes via suppressing the Gli-1 mediated Hedgehog signaling pathway, indicating that PRMT1 plays a critical role in OA development and serves as a promising therapeutic target for OA.

Analysis of cytokine profile and growth factors in platelet-rich plasma obtained by open systems and commercial columns

Objective:

To evaluate growth factors and cytokines in samples of platelet-rich plasma obtained by three different centrifugation methods.

Methods:

Peripheral blood of six individuals with no hematological diseases, aged 18 to 68 years, was drawn to obtain platelet-rich plasma, using the open method and commercial columns by Medtronic and Biomet. The products obtained with the different types of centrifugation were submitted to laboratory analysis, including pro-inflammatory cytokines and chemokines by flow cytometry assays, the concentration of fibroblast growth factors-2 (FGF-2) and transforming growth factor-beta1 (TGF-β1).

Results:

The diverse separation methods generated systematically different profiles regarding number of platelets and leukocytes. The Medtronic system yielded a product with the highest concentration of platelets, and the open method, with the lowest concentration of platelets. The results of cytokine analysis showed that the different types of centrifugation yielded products with high concentrations of interleukin 8, interleukin 1β. The open system resulted in a product with high levels of interleukin 6. Other cytokines and chemokines measured were similar between systems. The product obtained with the open method showed higher levels of TGF-β1 in relation to other systems and low FGF-2 levels.

Conclusion:

The formed elements, growth factors and cytokines in samples of platelet-rich plasma varied according to the centrifugation technique used.

Objetivo:

Avaliar fatores de crescimento e citocinas em amostras de plasma rico em plaquetas obtidas por três diferentes métodos de centrifugação.

Métodos:

Foi coletado sangue periférico de seis indivíduos, sem doença hematológica, com idades entre 18 e 68 anos, para obtenção de plasma rico em plaquetas, utilizando o método aberto e sistemas comerciais das empresas Medtronic e Biomet. Os produtos obtidos com os diferentes tipos de centrifugação foram submetidos às análises laboratoriais, incluindo citocinas próinflamatórias e quimiocinas, por meio de ensaios de citometria de fluxo, concentração do fator de crescimento fibroblástico-2 (FGF-2) e fator de crescimento transformador-beta1 (TGF-β1).

Resultados:

As diferentes centrifugações geraram perfis sistematicamente diferentes referentes ao número de plaquetas e de leucócitos. O sistema da Medtronic originou produto com a maior concentração de plaquetas, e o método aberto com a menor concentração de plaquetas. Os resultados da análise de citocinas demonstraram que os diferentes tipos de centrifugação originaram produtos com elevadas concentrações de interleucina 8 e interleucina 1β. O sistema aberto resultou em produto com elevados níveis de interleucina 6. As demais citocinas e quimiocinas mensuradas foram similares entre os sistemas. O produto obtido com o método aberto apresentou níveis superiores de TGF-β1 em relação aos demais sistemas e reduzidos níveis de FGF-2.

Conclusão:

Os elementos figurados, fatores de crescimento e citocinas, em amostras de plasma rico em plaquetas, variaram conforme a técnica de centrifugação utilizada.

Carthamin yellow inhibits matrix degradation and inflammation induced by LPS in the intervertebral disc via suppression of MAPK pathway activation

Carthamin yellow (CY), which is a flavonoid compound isolated from safflower, has various pharmacological effects including promoting blood circulation to remove blood stasis and alleviating pain. CY is a herb used in Chinese traditional medicines. Intervertebral disc degeneration (IDD) is a common spinal disorder and degeneration of nucleus pulposus (NP) cells and inflammation are significant parts of the pathological cascade. The curative effect of CY on NP cells in association with degeneration and inflammation remains to be elucidated. In the present study, rat NP cells were isolated, cultured and used to detect the suppressive effects of CY on lipopolysaccharide (LPS)-induced genetic expression variation and the expression of matrix degradation enzymes, including matrix metallopeptidase-3, ADAM metallopeptidase with thrombospondin type 1 motif (ADAMTS)-4 and ADAMTS-5. A protective effect of CY on NP cells was observed against LPS-induced matrix degradation and inflammation. Western blotting results demonstrated that pretreatment with CY significantly suppressed the LPS-induced activation of the mitogen activated protein kinase (MAPK) pathway. The results of the present study suggested that CY exerted anti-degenerative and anti-inflammatory effects on NP cells via inhibition of MAPK pathway activation. Therefore, CY may be a potential therapeutic drug for the treatment of IDD in the future.

MicroRNAs and Autophagy: Fine Players in the Control of Chondrocyte Homeostatic Activities in Osteoarthritis

Osteoarthritis (OA) is a debilitating degenerative disease of the articular cartilage with a multifactorial etiology. Aging, the main risk factor for OA development, is associated with a systemic oxidative and inflammatory phenotype. Autophagy is a central housekeeping system that plays an antiaging role by supporting the clearance of senescence-associated alterations of macromolecules and organelles. Autophagy deficiency has been related to OA pathogenesis because of the accumulation of cellular defects in chondrocytes. Microribonucleic acids (microRNAs or miRs) are a well-established class of posttranscriptional modulators belonging to the family of noncoding RNAs that have been identified as key players in the regulation of cellular processes, such as autophagy, by targeting their own cognate mRNAs. Here, we present a state-of-the-art literature review on the role of miRs and autophagy in the scenario of OA pathogenesis. In addition, a comprehensive survey has been performed on the functional connections of the miR network and the autophagy pathway in OA by using "microRNA," "autophagy," and "osteoarthritis" as key words. Discussion of available evidence sheds light on some aspects that need further investigation in order to reach a more comprehensive view of the potential of this topic in OA.

IL37 dampens the IL1β-induced catabolic status of human OA chondrocytes

Objective

A crucial feature of OA is cartilage degradation. This process is mediated by pro-inflammatory cytokines, among other factors, via induction of matrix-degrading enzymes. Interleukin 37 (IL37) is an anti-inflammatory cytokine and is efficient in blocking the production of pro-inflammatory cytokines during innate immune responses. We hypothesize that IL37 is therapeutic in treating the inflammatory cytokine cascade in human OA chondrocytes and can act as a counter-regulatory cytokine to reduce cartilage degradation in OA.

Methods

Human OA cartilage was obtained from patients undergoing total knee or hip arthroplasty. Immunohistochemistry was applied to study IL37 protein expression in cartilage biopsies from OA patients. Induction of IL37 expression by IL1β, OA synovium-conditioned medium and TNFα was investigated in human OA chondrocytes. Adenoviral overexpression of IL37 followed by IL1β stimulation was performed to investigate the anti-inflammatory potential of IL37.

Results

IL37 expression was detected in cartilage biopsies of OA patients and induced by IL1β. After IL1β stimulation, increased IL1β, IL6 and IL8 expression was observed in OA chondrocytes. Elevated IL37 levels diminished the IL1β-induced IL1β , IL6 and IL8 gene levels and IL1β and IL8 protein levels. In addition to the reduction in pro-inflammatory cytokine expression, IL37 reduced MMP1 , MMP3 , MMP13 and disintegrin and metalloproteinase with thrombospondin motifs 5 gene levels and MMP3 and MMP13 protein levels.

Conclusion

IL37 is induced by IL1β, and IL37 itself reduced IL1β, IL6 and IL8 production, indicating that IL37 is able to induce a counter-regulatory anti-inflammatory feedback loop in chondrocytes. In addition, IL37 dampens catabolic enzyme expression. This supports IL37 as a potential therapeutic target in OA.

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

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

Melatonin inhibits Sirt1-dependent NAMPT and NFAT5 signaling in chondrocytes to attenuate osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease mainly characterized by cartilage degradation. Interleukin-1β (IL-1β) contributes to OA pathogenesis by enhancing oxidative stress and inflammation. Melatonin reportedly elicits potent protection against OA. However, the role of melatonin and underlying mechanism in IL-1β-stimulated chondrocytes remain largely unclear. In this study, we found that melatonin inhibited IL-1β-induced toxicity and sirtuin 1 (Sirt1) enhancement in human chondrocytes. Melatonin reduced the IL-1β-increased nicotinamide phosphoribosyltransferase (NAMPT) expression and the NAD⁺ level in chondrocytes in a Sirt1-dependent manner. In turn, the inhibitory effect of melatonin on Sirt1 was mediated by NAMPT. Moreover, melatonin suppressed IL-1β-induced Sirt1-mediated matrix metalloproteinase (MMP)-3 and MMP-13 production. Melatonin also decreased the Sirt1-steered nuclear factor of activated T cells 5 (NFAT5) expression in IL-1β-challenged chondrocytes. NFAT5 depletion mimicked the suppressive effects of melatonin on IL-1β-elevated production of inflammatory mediators, including tumor necrosis factor-α (TNF-α), IL-1β, prostaglandin E2 (PGE₂), and nitric oxide (NO) in chondrocytes. TNF-α, IL-1β, PGE₂, or NO decrease caused the similar reduction of MMP-3 and MMP-13 by melatonin in IL-1β-insulted chondrocytes. Highly consistent with in vitro findings, in vivo results demonstrated that melatonin repressed the expression of relevant genes in rat OA pathogenesis in anterior cruciate ligament transection model. Overall, these results indicate that melatonin effectively reduced IL-1β-induced MMP production by inhibiting Sirt1-dependent NAMPT and NFAT5 signaling in chondrocytes, suggesting melatonin as a potential therapeutic alternative for chondroprotection of OA patients.