IL-1β promotes ADAMTS enzyme-mediated aggrecan degradation through NF-κB in human intervertebral disc

Protective effects of Shensuitongzhi formula on intervertebral disc degeneration via downregulation of NF-κB signaling pathway and inflammatory response

Low back pain (LBP) is a common orthopedic disease over the world. Lumbar intervertebral disc degeneration (IDD) is regarded as an important cause of LBP. Shensuitongzhi formula (SSTZF) is a drug used in clinical treatment for orthopedic diseases. It has been found that SSTZF can have a good treatment for IDD. But the exact mechanism has not been clarified. The results showed that SSTZF protects against LSI-induced degeneration of cartilage endplates and intervertebral discs. Meanwhile, SSTZF treatment dramatically reduces the expression of inflammatory factor as well as the expression of catabolism protein and upregulates the expression of anabolism protein in LSI-induced mice. In addition, SSTZF delayed the progression of LSI-induced IDD via downregulation the level of NF-κB signaling key gene RELA and phosphorylation of key protein P65 in endplate chondrocytes. Our study has illustrated the treatment as well as the latent mechanism of SSTZF in IDD.

Curcumenol Mitigates the Inflammation and Ameliorates the Catabolism Status of the Intervertebral Discs In Vivo and In Vitro via Inhibiting the TNFα/NFκB Pathway

Low back pain (LBP) caused by intervertebral disc degeneration (IVDD) is accredited to the release of inflammatory cytokines followed by biomechanical and structural deterioration. In our study, we used a plant-derived medicine, curcumenol, to treat IVDD. A cell viability test was carried out to evaluate the possibility of using curcumenol. RNA-seq was used to determine relative pathways involved with curcumenol addition. Using TNFα as a trigger of inflammation, the activation of the NF-κB signaling pathway and expression of the MMP family were determined by qPCR and western blotting. Nucleus pulposus (NP) cells and the rats’ primary NP cells were cultured. The catabolism status was evaluated by an ex vivo model. A lumbar instability mouse model was carried out to show the effects of curcumenol in vivo. In general, RNA-seq revealed that multiple signaling pathways changed with curcumenol addition, especially the TNFα/NF-κB pathway. So, the NP cells and primary NP cells were induced to suffer inflammation with the activated TNFα/NF-κB signaling pathway and increased expression of the MMP family, such as MMP3, MMP9, and MMP13, which would be mitigated by curcumenol. Owing to the protective effects of curcumenol, the height loss and osteophyte formation of the disc could be prevented in the lumbar instability mouse model in vivo.

Acidic and basic self-assembling peptide and peptide-graphene oxide hydrogels: characterisation and effect on encapsulated nucleus pulposus cells

Extracellular pH can have a profound effect on cell metabolism, gene and protein expression. Nucleus pulposus (NP) cells, for example, under acidic conditions accelerate the production of degradative enzymes and pro-inflammatory cytokines, leading ultimately to intervertebral disc degeneration, a major cause of back pain. Self-assembling peptide hydrogels constitute a well-established class of biomaterials that could be exploited as pH-tunable platform to investigate cell behaviour under normal and non-physiological pH. In this paper we formulated acidic (pH = 4) and basic (pH = 9) hydrogels, from the same octapeptide FEFKFEFK (F8) (F = phenyalanine, E = glutamic acid, K = lysine), to test the effect of non-physiological pH on encapsulated NP cells. Similarly, graphene oxide-containing F8 hydrogels (GO-F8) were formulated as stiffer analogues. Acidic and basic hydrogels showed peculiar morphologies and rheological properties, with all systems able to buffer within 30 minutes of exposure to cell culture media. NP cells seeded in acidic F8 hydrogels showed a more catabolic phenotype compared to basic hydrogels, with increased gene expression of degradative enzymes (MMP-3, ADAMTS-4), neurotrophic factors (NGF and BDNF) and NF-κB p65 phosphorylation. Acidic GO-F8 hydrogels also induced a catabolic response, although milder than basic counterparts and with the highest gene expression of characteristic NP-matrix components, aggrecan and collagen II. In all systems, the cellular response had a peak within 3 days of encapsulation, thereafter decreasing over 7 days, suggesting a 'transitory' effect of hydrogel pH on encapsulated cells. This work gives an insight on the effect of pH (and pH buffering) on encapsulated NP cells and offers new designs of low and high pH peptide hydrogels for 3D cell culture studies. STATEMENT OF SIGNIFICANCE: We have recently shown the potential of graphene oxide - self-assembling peptide hybrid hydrogels for NP cell culture and regeneration. Alongside cell carrier, self-assembling peptide hydrogels actually provide a versatile pH-tunable platform for biological studies. In this work we decided to explore the effect of non-physiological pH (and pH buffering) on encapsulated NP cells. Our approach allows the formulation of both acidic and basic hydrogels, starting from the same peptide sequence. We showed that the initial pH of the scaffold does not affect significantly cell response to encapsulation, but the presence of GO results in lower inflammatory levels and higher NP matrix protein production. This platform could be exploited to study the effect of pH on different cell types whose behaviour can be pH-dependent.

Curcumenol mitigates chondrocyte inflammation by inhibiting the NF‑κB and MAPK pathways, and ameliorates DMM‑induced OA in mice

At present, an increasing number of individuals are affected by osteoarthritis (OA), resulting in a heavy socioeconomic burden. OA in knee joints is caused by the release of inflammatory cytokines and subsequent biomechanical and structural deterioration. To determine its anti‑inflammatory function, the current study investigated the use of the plant‑derived medicine, curcumenol, in OA treatment. Curcumenol was not cytotoxic to ATDC5 chondrocytes and primary chondrocytes, as determined using a cell viability test. When these cells were treated with TNF‑α and IL‑1β to induce inflammation, curcumenol treatment inhibited the progression of inflammation by inactivating the NF‑κB and MAPK signaling pathways, as well as decreasing the expression levels of MMP3 (as indicated by reverse transcription‑quantitative PCR and western blotting). Moreover, to analyze metabolic and catabolic status in high‑density and pellet culture, catalytic changes and the degradation of the extracellular matrix induced by TNF‑α and IL‑1β, were evaluated by alcian blue staining. These catalytic deteriorations were ameliorated by curcumenol. Using curcumenol in disease management, the mechanical and metabolic disruption of cartilage caused in the destabilization of medial meniscus (DMM) model was prevented in vivo. Thus, curcumenol mitigated inflammation in ATDC5 chondrocytes and primary mice chondrocytes, and also ameliorated OA in a DMM‑induced mouse model.

Suramin attenuates intervertebral disc degeneration by inhibiting NF-κB signalling pathway

Aims

Interleukin (IL)-1β is one of the major pathogenic regulators during the pathological development of intervertebral disc degeneration (IDD). However, effective treatment options for IDD are limited. Suramin is used to treat African sleeping sickness. This study aimed to investigate the pharmacological effects of suramin on mitigating IDD and to characterize the underlying mechanism.

Methods

Porcine nucleus pulposus (NP) cells were treated with vehicle, 10 ng/ml IL-1β, 10 μM suramin, or 10 μM suramin plus IL-1β. The expression levels of catabolic and anabolic proteins, proinflammatory cytokines, mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-κB-related signalling molecules were assessed by Western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), and immunofluorescence analysis. Flow cytometry was applied to detect apoptotic cells. The ex vivo effects of suramin were examined using IDD organ culture and differentiation was analyzed by Safranin O-Fast green and Alcian blue staining.

Results

Suramin inhibited IL-1β-induced apoptosis, downregulated matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5, and upregulated collagen 2A (Col2a1) and aggrecan in IL-1β-treated NP cells. IL-1β-induced inflammation, assessed by IL-1β, IL-8, and tumour necrosis factor α (TNF-α) upregulation, was alleviated by suramin treatment. Suramin suppressed IL-1β-mediated proteoglycan depletion and the induction of MMP-3, ADAMTS-4, and pro-inflammatory gene expression in ex vivo experiments.

Conclusion

Suramin administration represents a novel and effectively therapeutic approach, which could potentially alleviate IDD by reducing extracellular matrix (ECM) deposition and inhibiting apoptosis and inflammatory responses in the NP cells.

Cite this article: Bone Joint Res 2021;10(8):498–513.

Activation of nuclear factor-kappa B by TNF promotes nucleus pulposus mineralization through inhibition of ANKH and ENPP1

Spontaneous mineralization of the nucleus pulposus (NP) has been observed in cases of intervertebral disc degeneration (IDD). Inflammatory cytokines have been implicated in mineralization of multiple tissues through their modulation of expression of factors that enable or inhibit mineralization, including TNAP, ANKH or ENPP1. This study examines the underlying factors leading to NP mineralization, focusing on the contribution of the inflammatory cytokine, TNF, to this pathologic event. We show that human and bovine primary NP cells express high levels of ANKH and ENPP1, and low or undetectable levels of TNAP. Bovine NPs transduced to express TNAP were capable of matrix mineralization, which was further enhanced by ANKH knockdown. TNF treatment or overexpression promoted a greater increase in mineralization of TNAP-expressing cells by downregulating the expression of ANKH and ENPP1 via NF-κB activation. The increased mineralization was accompanied by phenotypic changes that resemble chondrocyte hypertrophy, including increased RUNX2 and COL10A1 mRNA; mirroring the cellular alterations typical of samples from IDD patients. Disc organ explants injected with TNAP/TNF- or TNAP/shANKH-overexpressing cells showed increased mineral content inside the NP. Together, our results confirm interactions between TNF and downstream regulators of matrix mineralization in NP cells, providing evidence to suggest their participation in NP calcification during IDD.

Safflower Seed Extract Attenuates the Development of Osteoarthritis by Blocking NF-κB Signaling

Although safflower seed extract exhibits pharmacological activity against various diseases, the effects of its individual compounds on osteoarthritis (OA) have not been elucidated. Here, we evaluated the effects of these extracts and their single compounds on OA. N-(p-Coumaroyl) serotonin and N-feruloyl serotonin, main components of safflower seed extract, were isolated by high-performance liquid chromatography. Under in vitro OA mimic conditions, the expression of the matrix metalloproteinases (MMPs) MMP3/13 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) ADAMTS5 were reduced in mouse chondrocytes treated with safflower seed extract. Furthermore, the oral administration of safflower seed extract attenuated cartilage destruction in a mouse OA model induced by destabilization of the medial meniscus. N-(p-Coumaroyl) serotonin and N-feruloyl serotonin, but not serotonin, reduced MMP3, MMP13, and ADAMTS5 expression in IL-1β-treated chondrocytes. Additionally, they significantly blocked the nuclear factor-κB (NF-κB) pathway by inhibiting IκB degradation and p65 phosphorylation. Our results suggest that safflower seed extract and its single compounds can attenuate cartilage destruction by suppressing MMP and ADMATS5 expression. The anti-arthritic effects are mediated by NF-κB signaling and involve the inhibition of IκB degradation and p65 phosphorylation. These results indicate that safflower seed extract may serve as a novel therapeutic agent against OA.

Pro-Inflammatory and Neurotrophic Factor Responses of Cells Derived from Degenerative Human Intervertebral Discs to the Opportunistic Pathogen Cutibacterium acnes

Previously, we proposed the hypothesis that similarities in the inflammatory response observed in acne vulgaris and degenerative disc disease (DDD), especially the central role of interleukin (IL)-1β, may be further evidence of the role of the anaerobic bacterium Cutibacterium (previously Propionibacterium) acnes in the underlying aetiology of disc degeneration. To investigate this, we examined the upregulation of IL-1β, and other known IL-1β-induced inflammatory markers and neurotrophic factors, from nucleus-pulposus-derived disc cells infected in vitro with C. acnes for up to 48 h. Upon infection, significant upregulation of IL-1β, alongside IL-6, IL-8, chemokine (C-C motif) ligand 3 (CCL3), chemokine (C-C motif) ligand 4 (CCL4), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), was observed with cells isolated from the degenerative discs of eight patients versus non-infected controls. Expression levels did, however, depend on gene target, multiplicity and period of infection and, notably, donor response. Pre-treatment of cells with clindamycin prior to infection significantly reduced the production of pro-inflammatory mediators. This study confirms that C. acnes can stimulate the expression of IL-1β and other host molecules previously associated with pathological changes in disc tissue, including neo-innervation. While still controversial, the role of C. acnes in DDD remains biologically credible, and its ability to cause disease likely reflects a combination of factors, particularly individualised response to infection.

New insights into the interplay between miRNAs and autophagy in the aging of intervertebral discs

Intervertebral disc degeneration (IDD) has been widely known as a main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in the ageing process of intervertebral disc. Autophagy is an evolutionarily conserved process that maintains cellular homeostasis through recycling of nutrients and degradation of damaged or aged cytoplasmic organelles. Autophagy has been proposed as a "double-edged sword" and autophagy dysfunction of IVD cells is considered as a crucial reason of IDD. A rapidly growing number of recent studies demonstrate that both miRNAs and autophagy play important roles in the progression of IDD. Furthermore, accumulated research has indicated that miRNAs target autophagy-related genes and influence the onset and development of IDD. Hence, this review focuses mainly on the current findings regarding the correlations between miRNA, autophagy, and IDD and provides new insights into the role of miRNA-autophagy pathway involved in IDD pathophysiology.

NF-ĸβ upregulates ADAMTS5 expression by direct binding after TNF-α treatment in OUMS-27 chondrosarcoma cell line

Inflammation caused-aggrecan degradation is a critical event in the pathogenesis of osteoarthritis (OA). The aggrecanases like a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) are assumed to be key players in the aggrecan destruction. To develop the comprehensive therapy method for OA, it is essential to elucidate the activation mechanism of ADAMTS5 gene after stimulation of inflammatory cytokines like tumor necrosis factor-α (TNF-α). The cell lines of human chondrosarcoma (OUMS-27) and embryonic kidney (HEK293T) were incubated with tumor necrosis factor-α (TNF-α) for certain time periods, and the expression level of ADAMTS5 was measured in both mRNA and protein levels. Tissue-specific ADAMTS5 activation was founded to be induced after TNF-α treatment. Then, the constructs for the promoter region of ADAMTS5 were prepared and luciferase assay was conducted to understand the involvement mechanism of nuclear factor-kappa beta (NF-ĸβ) in ADAMTS5 activation. It was demonstrated that NF-ĸβ induces the ADAMTS5 expression level by directly binding the promoter region of ADAMTS5. Although the TNF-α blocker is used for OA treatment, the development of a more comprehensive treatment strategy is an urgent need. Our experimental data contributes in terms of selecting NF-ĸβ as a target molecule. Up to date, NF-ĸβ has been proven to involve in the ADAMTS5 up-regulation after several pro-inflammatory cytokines stimulation. In conclusion, our findings make important contributions to the knowledge about the roles of NF-ĸβ in ADAMTS5 activation under inflammatory conditions. So, NF-ĸβ could be considered to be a potential target for OA treatment.

Morusin Ameliorates IL-1β-Induced Chondrocyte Inflammation and Osteoarthritis via NF-κB Signal Pathway

Purpose

Osteoarthritis (OA) is one of the most common degenerative joint diseases in the world, characterized primarily by the progressive degradation of articular cartilage. Accumulating evidence has shown that Morusin, a flavonoid derived from the root bark of Morus alba (mulberry) plants, exerts unique protective properties in several diseases. However, its effects on OA, specifically, have not yet been characterized.

Methods

In this study, we evaluated the anti-inflammatory effect of Morusin on mouse chondrocytes and its underlying mechanism in vitro. In addition, the protective effect of Morusin on destabilization of the medial meniscus (DMM) model was also explored in vivo.

Results

In vitro, IL-1β-induced activation of inflammatory factors (TNF-α, IL-6, INOS and COX2) was dramatically suppressed by Morusin. Further, Morusin treatment inhibited the expression of ADAMTS5 and metalloproteinase (MMPs), both of which regulate extracellular matrix degradation. Morusin also decreased IL-1β-induced p65 phosphorylation and IκBα degradation. In vivo, degradation of the articular cartilage following surgical DMM, which mimicked OA pathology, was abrogated following treatment with Morusin, thus demonstrating a protective effect in the DMM model.

Conclusion

Herein, we demonstrate that Morusin reduces the OA inflammatory response in vitro and protects against articular cartilage degradation in vivo potentially via regulation of the NF-κB pathway. Hence, Morusin may prove to be an effective candidate for novel OA therapeutic strategies.

Baicalein Inhibits the IL-1β-Induced Inflammatory Response in Nucleus Pulposus Cells and Attenuates Disc Degeneration In vivo

Intervertebral disc degeneration (IDD) is widely considered one of the main causes of low back pain, which is a chronic progressive disease closely related to inflammation and degeneration of nucleus pulposus (NP) cells. Baicalein is a natural bioactive compound with anti-inflammatory effects in different diseases, including inhibition of the inflammatory response in chondrocytes, whose morphology and avascular supply are similar to those of NP cells. Therefore, we hypothesized that baicalein may have a therapeutic effect on IDD by suppressing the inflammatory response. In vitro, NP cells were pretreated with baicalein for 2 h and then incubated with IL-1β for 24 h. We found that baicalein not only inhibited the overexpression of inflammatory cytokine production, including NO, PGE2, TNF-α, and IL-6, but also suppressed the expression of COX-2 and iNOS. The IL-1β-induced overexpression of MMP13 and ADAMTS5 and degradation of aggrecan and type II collagen were reversed by baicalein in a dose-dependent manner. Mechanistically, we found that baicalein suppressed the IL-1β-induced activation of the NF-κB and MAPK pathways. Moreover, an in vivo study demonstrated that baicalein treatment could ameliorate IDD in a puncture-induced rat model. Thus, baicalein has great value as a potential therapeutic agent for IDD.

Elevated expression of hypoxia-inducible factor-2alpha regulated catabolic factors during intervertebral disc degeneration

HEADINGS AIMS

The present study determined whether nucleus pulposus (NP) cells express hypoxia-inducible factor-2alpha (HIF-2α) and assessed its role in regulating the expression of catabolic factors during intervertebral disc degeneration.

MATERIALS AND METHODS

Human degenerated NP tissues were acquired to examine the HIF-2α expression levels using immunohistochemistry, western blotting, and Real-time PCR. Human NP cells were cultivated under normoxic or hypoxic conditions, and the HIF-2α expression was determined. Then, human NP cells were treated with HIF-2α plasmids, HIF-2α siRNA, and tumor necrosis factor-alpha (TNF-α) to evaluate the role of HIF-2α in regulating matrix metalloproteinase (MMP) and aggrecanase expression. An in vivo rabbit disc degeneration model was established to demonstrate that HIF-2α plays a critical role in disc degeneration.

KEY FINDINGS

We found that HIF-2α had a markedly elevated expression in human degenerated discs in the Grade III stage. HIF-2α protein and gene transcript levels in vitro were relatively higher under hypoxic conditions. The expression of MMP-13, ADAMTS-4 was decreased significantly in HIF-2α silencing condition, while the over-expression resulted in significantly increased levels of MMP-13 and ADAMTS-4. When cytokine TNF-α was added, HIF-2α was induced by nuclear factor-κB (NF-κB). The in vivo experiments showed that the HIF-2α controlled the catabolic factors MMP-13 and ADAMTS-4 that regulated the collagen II and aggrecan metabolism in disc degeneration.

SIGNIFICANCE

HIF-2α is a catabolic regulator in disc degeneration and directly controls the catabolic genes. The suppression of HIF-2α expression leads to decelerates extracellular matrix degradation that might represent a therapeutic target for the degenerative disc.

Molecular Relationships among Obesity, Inflammation and Intervertebral Disc Degeneration: Are Adipokines the Common Link?

Intervertebral disc degeneration (IVDD) is a chronic, expensive, and high-incidence musculoskeletal disorder largely responsible for back/neck and radicular-related pain. It is characterized by progressive degenerative damage of intervertebral tissues along with metabolic alterations of all other vertebral tissues. Despite the high socio-economic impact of IVDD, little is known about its etiology and pathogenesis, and currently, no cure or specific treatments are available. Recent evidence indicates that besides abnormal and excessive mechanical loading, inflammation may be a crucial player in IVDD. Furthermore, obese adipose tissue is characterized by a persistent and low-grade production of systemic pro-inflammatory factors. In this context, chronic low-grade inflammation associated with obesity has been hypothesized as an important contributor to IVDD through different, but still unknown, mechanisms. Adipokines, such as leptin, produced prevalently by white adipose tissues, but also by other cells of mesenchymal origin, particularly cartilage and bone, are cytokine-like hormones involved in important physiologic and pathophysiological processes. Although initially restricted to metabolic functions, adipokines are now viewed as key players of the innate and adaptative immune system and active modulators of the acute and chronic inflammatory response. The goal of this review is to summarize the most recent findings regarding the interrelationships among inflammation, obesity and the pathogenic mechanisms involved in the IVDD, with particular emphasis on the contribution of adipokines and their potential as future therapeutic targets.

Protective effects of alogliptin against TNF-α-induced degradation of extracellular matrix in human chondrocytes

Osteoarthritis (OA) is a common debilitating disease most prevalent among the elderly population worldwide. Excessive degradation of the articular extracellular matrix is a pivotal event in the development of OA. Preventative treatments against the destruction of type II collagen and aggrecan, the two main components of the articular extracellular matrix, may serve as a novel therapy against the progression of OA. In the current study, we investigated whether the DPP-4 inhibitor alogliptin could prevent degradation of the articular extracellular matrix in human primary chondrocytes. Pretreatment with alogliptin successfully prevented degradation of type II collagen and aggrecan in a dose-dependent manner by reducing increased expression of MMP-1, -3, and -13 as well as ADAMTS-4 and -5 induced by treatment with TNF-α. Furthermore, pretreatment with alogliptin also reduced TNF-α-induced expression of IKKα/β, IκBα and NF-κB in human primary chondrocytes. This suggests that DPP-4 inhibitors such as alogliptin may be used as an effective preventative therapy against continued destruction of the articular extracellular matrix in OA.

Andrographolide prevents human nucleus pulposus cells against degeneration by inhibiting the NF-κB pathway

Intervertebral disc degeneration (IDD) is among the most common spinal disorders, pathologically characterized by excessive cell apoptosis and production of proinflammatory factors. Pharmacological targeting of nucleus pulposus (NP) degeneration may hold promise in IDD therapy, but it is limited by adverse side effects and nonspecificity of drugs. In this study, we used a natural compound, andrographolide (ANDRO), which has been widely used to intervene inflammatory and apoptotic diseases in the investigation of NP degeneration based on IDD-patients-derived NP cells by lipopolysaccharide (LPS) treatment for the preservation of degeneration. The results showed that LPS maintained the degeneration status of NP cells as evidenced by a high apoptosis rate and the expression of degenerative and inflammatory mediators after LPS treatment. ANDRO reversed the effects of LPS-caused degeneration of NP cells and maintained the phenotype of NP cells, as demonstrated by flow cytometry, degenerative mediators (ADAMTS4 and ADAMTS5), inflammatory factors (COX2, PGE2, MMP-13, and MMP-3), biomarkers of NP cells (SOX9, ACAN, and COL2A1) expressions, and glycosaminoglycan secretion. We also found the involvement of the nuclear factor kappa-light-chain-enhancer of the activated B cells (NF-κB) pathway in ANDRO treatment, indicating that ANDRO prevented the LPS-preserved degeneration of NP cells by inhibiting the NF-κB pathway. This study may provide a reference for clinic medication of IDD therapy.

Long non-coding RNAs in nucleus pulposus cell function and intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the major cause of low back pain which incurs a significant public-health and economic burden. The aetiology of IDD is complex, with developmental, genetic, biomechanical and biochemical factors contributing to the disease development. Deregulated phenotypes of nucleus pulposus cells, including aberrant differentiation, apoptosis, proliferation and extracellular matrix deposition, are involved in the initiation and progression of IDD. Non-coding RNAs, including long non-coding RNAs (lncRNAs), have recently been identified as important regulators of gene expression. Research into their roles in IDD has been very active over the past 5 years. Our review summarizes current research regarding the roles of deregulated lncRNAs (eg, RP11-296A18.3, TUG1, HCG18) in modulating nucleus pulposus cell functions in IDD. These exciting findings suggest that specific modulation of lncRNAs or their downstream signalling pathways might be an attractive approach for developing novel therapeutics for IDD.

Combined detection of COMP and CS846 biomarkers in experimental rat osteoarthritis: a potential approach for assessment and diagnosis of osteoarthritis

Background

To comprehensively evaluate the diagnostic value of serum cartilage oligomeric matrix protein (COMP) and chondroitin sulfate 846 epitope (CS846) biomarkers in osteoarthritis (OA), longitudinal and combined measurement of serum COMP and CS846 were performed at different stages in the pathological process of OA in a rat model of anterior cruciate ligament transection (ACLT).

Methods

Sixty male Sprague-Dawley rats were randomly divided into two groups, including a model group (n = 30) and a control group (n = 30). Rat models were established by ACLT surgery, and sham operations were performed on rats in the control group. Prior to surgery and at 2, 4, 6, 8, and 10 weeks after ACLT surgery, serum levels of COMP and CS846 biomarkers were determined using an enzyme-linked immunosorbent assay approach. Five rats per group were euthanized at 2, 4, 6, 8, and 10 weeks after surgery, after which tibial plateau specimens were collected. Macroscopic observation and histological examination were employed for rat tibial plateau. Histological changes in articular cartilage were evaluated according to Osteoarthritis Research Society International (OARSI) scoring criteria. The area under the curve (AUC) of COMP, CS846, and combined biomarkers was compared using receiver operating characteristic (ROC) curve.

Results

Within 10 weeks after surgery, serum levels of COMP and CS846 in the model group were significantly higher when compared to those in the control group. Moreover, a significant correlation was observed between changes in COMP and CS846 levels. At each time point, macroscopic observations and OARSI scores were significantly increased in the development of OA. The AUC of combined biomarkers was higher compared to that of COMP and CS846 alone. Finally, a positive relationship was found between levels of COMP and CS846 and the OARSI score.

Conclusions

In this study, we found that combined detection of serum CS846 and COMP levels can be used for diagnosis and monitoring of OA progression.

Co-culturing nucleus pulposus mesenchymal stem cells with notochordal cell-rich nucleus pulposus explants attenuates tumor necrosis factor-α-induced senescence

Background

Cell therapy for the treatment of intervertebral disc degeneration (IDD) faces serious barriers since tissue-specific adult cells such as nucleus pulposus cells (NPCs) have limited proliferative ability and poor regenerative potential; in addition, it is difficult for exogenous adult stem cells to survive the harsh environment of the degenerated intervertebral disc. Endogenous repair by nucleus pulposus mesenchymal stem cells (NPMSCs) has recently shown promising regenerative potential for the treatment of IDD. Notochordal cells (NCs) and NC-conditioned medium (NCCM) have been proven to possess regenerative ability for the treatment of IDD, but this approach is limited by the isolation and passaging of NCs. Our previous study demonstrated that modified notochordal cell-rich nucleus pulposus (NC-rich NP) has potential for the repair of IDD. However, whether this can protect NPMSCs during IDD has not been evaluated.

Methods

In the current study, tumor necrosis factor (TNF)-α was used to mimic the inflammatory environment of IDD. Human NPMSCs were cocultured with NC-rich NP explants from healthy rabbit lumbar spine with or without TNF-α. Cell proliferation and senescence were analyzed to investigate the effect of NC-rich NP explants on TNF-α-treated NPMSCs. The expression of mRNA encoding proteins related to matrix macromolecules (such as aggrecan, Sox-9, collagen Iα, and collagen IIα), markers related to the nucleus pulposus cell phenotype (including CA12, FOXF1, PAX1, and HIF-1α), and senescence markers (such as p16, p21, and p53), senescence-associated proinflammatory cytokines (IL-6), and extracellular proteases (MMP-13, ADAMTS-5) was assessed. The protein expression of CA12 and collagen II was also evaluated.

Results

After a 7-day treatment, the NC-rich NP explant was found to enhance cell proliferation, decrease cellular senescence, promote glycosaminoglycan (GAG), collagen II, and CA12 production, upregulate the expression of extracellular matrix (ECM)-related genes (collagen I, collagen II, SOX9, and ACAN), and enhance the expression of nucleus pulposus cell (NPC) markers (HIF-1α, FOXF1, PAX1, and CA12).

Conclusion

Modified NC-rich NP explants can attenuate TNF-α-induced degeneration and senescence of NPMSCs in vitro. Our findings provide new insights into the therapeutic potential of NC-rich NP for the treatment of IDD.

Restoring the IL-1β/NF-κB-induced impaired chondrogenesis by diallyl disulfide in human adipose-derived mesenchymal stem cells via attenuation of reactive oxygen species and elevation of antioxidant enzymes

Strategies based on mesenchymal stem cell (MSC) therapy for restoring injured articular cartilage are not effective enough in osteoarthritis (OA). Due to the enhanced inflammation and oxidative stress in OA microenvironment, differentiation of MSCs into chondrocytes would be impaired. This study aims to explore the effects of diallyl disulfide (DADS) on IL-1β-mediated inflammation and oxidative stress in human adipose derived mesenchymal stem cells (hADSCs) during chondrogenesis. MTT assay was employed to examine the effects of various concentrations of DADS on the viability of hADSCs at different time scales to obtain non-cytotoxic concentration range of DADS. The effects of DADS on IL-1β-induced intracellular ROS generation and lipid peroxidation were evaluated in hADSCs. Western blotting was used to analyze the protein expression levels of IκBα (np), IκBα (p), NF-κB (np) and NF-κB (p). Furthermore, the gene expression levels of antioxidant enzymes in hADSCs and chondrogenic markers at days 7, 14 and 21 of differentiation were measured using qRT-PCR. The results showed that addition of DADS significantly enhanced the mRNA expression levels of antioxidant enzymes as well as reduced ROS elevation, lipid peroxidation, IκBα activation and NF-κB nuclear translocation in hADSCs treated with IL-1β. In addition, DADS could significantly increase the expression levels of IL-1β-induced impaired chondrogenic marker genes in differentiated hADSCs. Treatment with DADS may provide an effective approach to prevent the pro-inflammatory cytokines and oxidative stress as catabolic causes of chondrocyte cell death and enhance the protective anabolic effects by promoting chondrogenesis associated gene expressions in hADSCs exposed to OA condition.

Simvastatin Inhibits IL-1β-Induced Apoptosis and Extracellular Matrix Degradation by Suppressing the NF-kB and MAPK Pathways in Nucleus Pulposus Cells

Statins are widely used hypocholesterolemic drugs that block the mevalonate pathway. Some studies have shown that statins may have the potential to inhibit intervertebral disk (IVD) degeneration (IDD). Interleukin (IL)-1β, a catabolic cytokine, is a key regulator of IDD. This study aimed to investigate the mechanism underlying the effect of simvastatin on IDD. The viability of nucleus pulposus (NP) cells was determined by the methyl-thiazolyl-tetrazolium (MTT) assay. The apoptosis of NP cells was measured by flow cytometric analysis, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and western blotting of relevant apoptotic proteins. The protein levels of catabolic factors and anabolic factors were determined by western blotting. The cells were stimulated with IL-1β in the absence or presence of simvastatin to investigate the effects on matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, ADAMTS-5, type II collagen, and aggrecan expression. Our findings indicate that simvastatin considerably inhibited IL-1β-induced apoptosis in NP cells. We also found that simvastatin attenuated IL-1β-induced expression and MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5 activities and also reduced the decrease in type II collagen and aggrecan expression. In addition, simvastatin considerably suppressed the nuclear translocation and activation of nuclear factor-kappa B (NF-KB) by inhibiting p65 phosphorylation and translocation and blocking inhibitor kB-α degradation. It also inhibited MAPK pathway activation by blocking c-Jun N-terminal kinase (JNK), p38, and ERK phosphorylation. The results of our study revealed that simvastatin is a potential agent for IDD prevention and treatment.

HtrA1 up-regulates expression of MMPs via Erk1/2/Rock-dependent pathways

BACKGROUND

There are few studies that have identified the potential role of a high temperature requirement A1 (HtrA1) in intervertebral disc degeneration (IDD). This study was undertaken to investigate the regulatory role of HtrA1 in the pathogenesis of IDD.

MATERIAL AND METHODS

The mRNA levels of HtrA1 and matrix metalloproteinases (MMPs) of human intervertebral disc degeneration tissues were measured by real-time quantitative PCR, and a correlation between the expression level of HtrA1 and MMPs was also investigated. Human nucleus pulposus cells (HNPCs) were challenged with rHtrA1, and expression of MMPs was measured by real-time quantitative PCR, Western blotting, and ELISA. Moreover, to analyze the mechanism by which HtrA1 up-regulates MMPs, ERK1/2/ROCK signaling pathway inhibitors were also used.

RESULTS

We found significant increases in mRNA expression of HtrA1 and MMP1, 3, 9, and 13 in IDD tissues compared with control. HtrA1 expression level was associated with the levels of MMP1, 3, and 13. Expression of MMP1, 3, and 13 mRNA and protein were significantly increased in HNPCs treated by rHtrA1. Moreover, administration of the ERK1/2 signaling pathway inhibitor or ROCK signaling pathway inhibitor decreased rHtrA1-induced MMPs production. Therefore, changes in HtrA1 expression could be involved in the pathogenesis of IDD.

CONCLUSION

Our findings indicate that HtrA1 can induce increases in MMPs in HNPCs via the ERK1/2/ROCK signaling pathway, thus providing new insights into the role of HtrA1 in the pathogenesis of IDD.

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.

Icariin Prevents IL-1β-Induced Apoptosis in Human Nucleus Pulposus via the PI3K/AKT Pathway

Purpose

To explore the effect and possible mechanism of icariin, a prenylated flavonol glycoside derived from the Chinese herb Epimedium sagittatum that was applied to IL-1β pretreated human nucleus pulposus (NP) cells.

Methods

Human NP cells were isolated from intervertebral discs of patients with scoliosis and lumbar spondylolisthesis. The cells were divided into five groups: A (blank control); B (20 ng/ml IL-1β); C (20 ng/ml IL-1β + 20 μM icariin); D (20 μM icariin + 20 ng/ml IL-1β + 25 μM LY294002); E (20 ng/ml IL-1β + 25 μM LY294002). For each of the five groups, the CCK8, apoptosis rates, ROS rates, and JC-1 rates were determined and an electron micrograph was performed. Different expression levels of apoptosis proteins and proteins in the PI3K/AKT pathway were detected via western blot.

Results

We found that the damage effects on human nucleus pulposus cells from 20 ng/ml of IL-1β exposure were attenuated by icariin. When the PI3K/AKT pathway was blocked by LY294002, a specific inhibitor of this pathway, the protective effect of icariin was impaired. In summary, icariin might be a protective traditional Chinese medicine, which prevents inflammation-induced degeneration of intervertebral discs partly through the PI3K/AKT pathway.

Mechanism of microRNA-146a-mediated IL-6/STAT3 signaling in lumbar intervertebral disc degeneration

The aim of the study was to investigate the mechanism of microRNA (miR)-146a-mediated activation of interleukin-6/signal transducer and activator of transcription 3 (IL-6/STAT3) in lumbar intervertebral disc degeneration. To obtain intervertebral tissue, we recruited 5 patients with lumbar intervertebral disc herniation (experimental group) and 5 patients with lumbar burst fracture (control group). Nucleus pulposus tissue was extracted by surgery and cultured. miR-146a empty vector, mimic, and inhibitor were transfected into the two groups of cells for 24 h and the levels of IL-6, type II collagen (Col II), aggrecan, STAT3, matrix metalloproteinase (MMP)-3, and a disintegrin and metalloproteinase with thrombospondin type I motifs (ADAMTS) were detected. We found no differences in the levels of IL-6, Col II, aggrecan, STAT3, MMP-3, and ADAMTS before and after treatment in the control group. However, the levels of miR-146a, IL-6, STAT3, MMP-3, and ADAMTS were significantly elevated, whereas Col II and aggrecan levels were lower in the experimental group before treatment. The levels of IL-6, STAT3, MMP-3, and ADAMTS were elevated after treatment with miR-146a mimic when compared with the miR-146a empty vector in the experimental group, and Col II and aggrecan levels were decreased. However, the cells treated with miR-146a inhibitor had the opposite result. Thus, the IL-6/STAT3 signaling pathway can be mediated by a high expression of miR-146a to regulate the occurrence of lumbar intervertebral disc degeneration.

Inhibiting IL-1 signaling pathways to inhibit catabolic processes in disc degeneration

Intervertebral disc degeneration is characterized by an imbalance between catabolic and anabolic signaling, with an increase in catabolic cytokines particularly IL-1β, a key regulator of IVD degeneration. This study aimed to investigate intracellular signaling pathways activated by IL-1β, and GDF-5 in the degenerate IVD to identify potential new therapeutic targets. Human NP cells were cultured in alginate beads to regain in vivo phenotype prior to stimulation with IL-1β or GDF-5 for 30 min, a proteasome profiler array was initially utilized to screen activation status of 46 signaling proteins. Immunoflourescence was used to investigate activation of the NFκB pathway. Cell-based ELISAs were then deployed to confirm results for ERK1/2, p38 MAPK, c-jun, and IκB signaling. IHC was utilized to investigate native activation status within human IVD tissue between grades of degeneration. Finally, cells were stimulated with IL-1β in the absence or presence of p38 MAPK, c-jun, JNK, and NFκB inhibitors to investigate effects on MMP3, MMP13, IL-1β, IL-6, and IL-8 mRNA expression. This study demonstrated three key signaling pathways which were differentially activated by IL-1β but not GDF-5; namely p38 MAPK, c-jun, and NFκB. While ERK 1/2 was activated by both GDF-5 and IL-1. Immunohistochemistry demonstrated p38 MAPK, c-jun, and NFκB were activated during human IVD degeneration and inhibition of these pathways reduced or abrogated the catabolic effects of IL-1β, with inhibition of NFκB signaling demonstrating most widespread inhibition of IL-1β catabolic effects. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:74-85, 2017.

Genetic Alterations in Intervertebral Disc Disease

BACKGROUND

Intervertebral disc degeneration (IVDD) is considered a multifactorial disease that is influenced by both environmental and genetic factors. The last two decades of research strongly demonstrate that genetic factors contribute about 75% of the IVDD etiology. Recent total genome sequencing studies have shed light on the various single-nucleotide polymorphisms (SNPs) that are associated with IVDD.

AIM

This review presents comprehensive and updated information about the diversity of genetic factors in the inflammatory, degradative, homeostatic, and structural systems involved in the IVDD. An organized collection of information is provided regarding genetic polymorphisms that have been identified to influence the risk of developing IVDD. Understanding the proteins and signaling systems involved in IVDD can lead to improved understanding and targeting of therapeutics.

MATERIALS AND METHODS

An electronic literature search was performed using the National Library of Medicine for publications using the keywords genetics of IVDD, lumbar disc degeneration, degenerative disc disease, polymorphisms, SNPs, and disc disease. The articles were then screened based on inclusion criteria that included topics that covered the correlation of SNPs with developing IVDD. Sixty-five articles were identified as containing relevant information. Articles were excluded if they investigated lower back pain or just disc herniation without an analysis of disc degeneration. This study focuses on the chronic degeneration of IVDs.

RESULTS

Various genes were identified to contain SNPs that influenced the risk of developing IVDD. Among these are genes contributing to structural proteins, such as COL1A1, COL9A3, COL9A3, COL11A1, and COL11A2, ACAN, and CHST3. Furthermore, various SNPs found in the vitamin-D receptor gene are also associated with IVDD. SNPs related to inflammatory cytokine imbalance are associated with IVDD, although some effects are limited by sex and certain populations. SNPs in genes that code for extracellular matrix-degrading enzymes, such as MMP-1, MMP-2, MMP-3, MMP-9, MMP-14, ADAMTS-4, and ADAMTS-5 are also associated with IVDD. Apoptosis-mediating genes, such as caspase 9 gene (CASP9), TRAIL, and death receptor 4 (DR4), as well as those for growth factors, such as growth differentiation factor 5 and VEGF, are identified to have polymorphisms that influence the risk of developing IVDD.

CONCLUSION

Within the last 10 years, countless new SNPs have been identified in genes previously unknown to be associated with IVDD. Furthermore, the last decade has also revealed new SNPs identified in genes already known to be involved with increased risk of developing IVDD. Improved understanding of the numerous genetic variants behind various pathophysiological elements of IVDD could help advance personalized care and pharmacotherapeutic strategies for patients suffering from IVDD in the future.

The NLRP3/Caspase-1/Interleukin-1β Axis Is Active in Human Lumbar Cartilaginous Endplate Degeneration

BACKGROUND

Modic changes are the MRI signal changes of degenerative lumbar vertebral endplate and which lead to or accelerate intervertebral disc degeneration. NLRP3, caspase-1, and interleukin-1β (IL-1β) play a pivotal role in the pathogenesis of many inflammatory diseases, such as osteoarthritis. However, the roles of IL-1β and its activators caspase-1 and NLRP3 are unclear in the degenerative endplate.

QUESTIONS/PURPOSES

We asked: (1) What are the degenerative changes of the histologic features and chondrogenic markers' gene expressions between the cartilaginous endplates of patients with Modic changes and trauma (control)? (2) How does the NLRP3/caspase-1/IL-1β axis in the cartilaginous endplates of patients with Modic changes compare with control (trauma) specimens?

METHODS

Surgical specimens of cartilaginous endplates were divided into Modic changes (n = 56) and the trauma control (n = 16) groups. Hematoxylin and eosin and safranin O staining of cartilaginous endplate tissues were done to evaluate the extracellular matrix. Reverse transcription-polymerase chain reaction was performed on these tissues to investigate mRNA expression of type II collagen (Col II), SOX-9, matrix metalloproteinase-3, and a disintegrin like and metalloproteinase thrombospondin type I motifs-5. NLRP3, caspase-1, and IL-1β were evaluated by reverse transcription-polymerase chain reaction and immunohistochemistry.

RESULTS

Hematoxylin and eosin and safranin O staining showed the extracellular matrix degraded in the cartilaginous endplates of patients with Modic changes but not in the control cartilaginous endplates. Chondrogenic Col II (p = 0.024) and SOX9 (p = 0.053) were downregulated in the Modic changes group compared with the control group. In contrast to the control group, the transcriptional levels of NLRP3 (p < 0.001), caspase-1 (p = 0.054), and IL-1β (p = 0.001) were all upregulated in the Modic changes group.

CONCLUSIONS

The expression of NLRP3, caspase-1, and IL-1β was upregulated in the patients with low back pain and Modic changes on MRI compared with patients with vertebral burst fracture without degenerative changes on MRI. The data suggest the NLRP3/caspase-1/IL-1β axis may be implicated in lumbar cartilaginous endplate degeneration.

CLINICAL RELEVANCE

The NLRP3/caspase-1/IL-1β axis is active in cartilaginous endplates of patients with Modic changes and inflammatory cascades can exacerbate the cartilaginous endplate degeneration which may act as a trigger for intervertebral disc degeneration and low back pain. If these findings can be confirmed by others, we hope that new and effective therapy could be developed directed against this target.