The imbalance between TIMP3 and matrix-degrading enzymes plays an important role in intervertebral disc degeneration

Pathogenesis and therapeutic implications of matrix metalloproteinases in intervertebral disc degeneration: A comprehensive review

Intervertebral disc (IVD) degeneration (IDD) is a common disorder that affects the spine and is a major cause of lower back pain (LBP). The extracellular matrix (ECM) is the structural foundation of the biomechanical properties of IVD, and its degradation is the main pathological characteristic of IDD. Matrix metalloproteinases (MMPs) are a group of endopeptidases that play an important role in the degradation and remodeling of the ECM. Several recent studies have shown that the expression and activity of many MMP subgroups are significantly upregulated in degenerated IVD tissue. This upregulation of MMPs results in an imbalance of ECM anabolism and catabolism, leading to the degradation of the ECM and the development of IDD. Therefore, the regulation of MMP expression is a potential therapeutic target for the treatment of IDD. Recent research has focused on identifying the mechanisms by which MMPs cause ECM degradation and promote IDD, as well as on developing therapies that target MMPs. In summary, MMP dysregulation is a crucial factor in the development of IDD, and a deeper understanding of the mechanisms involved is needed to develop effective biological therapies that target MMPs to treat IDD.

Intervertebral disc degeneration and how it leads to low back pain

The purpose of this review was to evaluate data generated by animal models of intervertebral disc (IVD) degeneration published in the last decade and show how this has made invaluable contributions to the identification of molecular events occurring in and contributing to pain generation. IVD degeneration and associated spinal pain is a complex multifactorial process, its complexity poses difficulties in the selection of the most appropriate therapeutic target to focus on of many potential candidates in the formulation of strategies to alleviate pain perception and to effect disc repair and regeneration and the prevention of associated neuropathic and nociceptive pain. Nerve ingrowth and increased numbers of nociceptors and mechanoreceptors in the degenerate IVD are mechanically stimulated in the biomechanically incompetent abnormally loaded degenerate IVD leading to increased generation of low back pain. Maintenance of a healthy IVD is, thus, an important preventative measure that warrants further investigation to preclude the generation of low back pain. Recent studies with growth and differentiation factor 6 in IVD puncture and multi-level IVD degeneration models and a rat xenograft radiculopathy pain model have shown it has considerable potential in the prevention of further deterioration in degenerate IVDs, has regenerative properties that promote recovery of normal IVD architectural functional organization and inhibits the generation of inflammatory mediators that lead to disc degeneration and the generation of low back pain. Human clinical trials are warranted and eagerly anticipated with this compound to assess its efficacy in the treatment of IVD degeneration and the prevention of the generation of low back pain.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

Inhibited microRNA-494-5p promotes proliferation and suppresses senescence of nucleus pulposus cells in mice with intervertebral disc degeneration by elevating TIMP3

It has been unraveled that microRNAs (miRNAs) played crucial roles in processes of human diseases, while the role of miR-494-5p in intervertebral disc degeneration (IDD) remains scarcely studied. We aimed to investigate the mechanisms of miR-494-5p in IDD with the involvement of tissue inhibitor of metalloproteinase 3 (TIMP3). Expression of miR-494-5p and TIMP3 in IDD clinical specimens was assessed. The IDD models were established by needle punching, which were then injected with low expression of miR-494-5p or TIMP3 overexpression lentivirus to observe their effects on pathology and apoptosis in IDD mice. The nucleus pulposus cells were isolated and, respectively, treated with miR-494-5p inhibitor or TIMP3 overexpression plasmid to determine the viability, apoptosis, and senescence in vitro. Furthermore, the expression of Aggrecan, Col-2, Caveolin-1, and SA-β-gal in nucleus pulposus cells in vitro were measured. The target relation between miR-494-5p and TIMP3 was determined. An increased expression of miR-494-5p and a decreased expression of TIMP3 were found in IDD. Downregulation of miR-494-5p or overexpression of TIMP3 could relieve pathology and suppress nucleus pulposus cell apoptosis in IDD mice, as well as promote the viability and attenuate the apoptosis and senescence of nucleus pulposus cells from IDD mice. Moreover, inhibition of miR-494-5p or overexpression of TIMP3 upregulated Aggrecan and Col-2 expression while downregulated Caveolin-1 and SA-β-gal expression, and TIMP3 was the target gene of miR-494-5p. Results of this study indicated that the degradation of miR-494-5p ameliorates the development of IDD by elevating TIPM3, which may provide new targets for IDD treatment.

The c-Jun signaling pathway has a protective effect on nucleus pulposus cells in patients with intervertebral disc degeneration

Among a range of diverse clinical symptoms, intervertebral disc degeneration (IDD) contributes mostly to the onset of lower back pain. The present study aimed to investigate the effects of c-Jun on nucleus pulposus (NP) cells of IDD and its regulation on molecular mechanisms. Intervertebral disc (IVD) tissues were collected from patients suffering from IDD disease, and NP cells were subsequently isolated and cultured. By overexpressing c-Jun in NP cells, expression levels of mRNAs and proteins of IDD-related genes and inflammatory cytokines were subjected to reverse transcription-quantitative PCR, western blot and ELISA assays. Additional transforming growth factor-β (TGF-β) antibodies were administrated to suppress the function of TGF-β. Cell proliferation and apoptosis were determined via Cell Counting Kit-8 and TUNEL assays, respectively. The results demonstrated that the overexpression of c-Jun robustly upregulated both mRNA and protein expression of TGF-β, TIMP metallopeptidase inhibitor 3, aggrecan and collagen type II alpha 1 chain and simultaneously downregulated the expression of the inflammatory cytokines TNF-α, interleukin (IL)-1β, IL-6 and IL-17. Furthermore, following c-Jun overexpression, survival rates of NP cells were increased while apoptosis rates were decreased. However, the addition of a TGF-β antibody significantly promoted apoptosis and restricted cell survival, which differed from the results of the c-Jun overexpression group. The present study hypothesized therefore that c-Jun may positively regulate TGF-β expression within NP cells of IDD, which could promote the proliferation of IDD-NP cells and accelerate cell viability via reducing apoptosis and the inflammatory response.

Upregulation of Sirt1 by tyrosol suppresses apoptosis and inflammation and modulates extracellular matrix remodeling in interleukin-1β-stimulated human nucleus pulposus cells through activation of PI3K/Akt pathway

Intervertebral disc degeneration (IDD) is the major pathogenesis of lower back pain. Tyrosol is a polyphenolic compound that exhibits anti-oxidant, anti-apoptotic, and anti-inflammatory effects. Herein, we explored the effects and mechanisms of tyrosol on IDD progression in interleukin (IL)-1β-stimulated human nucleus pulposus cells (HNPCs). Cell viability and apoptosis were detected by CCK-8 and flow cytometry analysis, respectively. The production of tumor necrosis factor-α (TNF-α), IL-6, nitric oxide (NO), and prostaglandin E2 (PGE2) was examined to evaluate inflammation. The mRNA expression of matrix metalloproteinases (MMPs) (MMP-3/9/13), collagen type II, SRY-related high mobility group box 9 (SOX-9), and aggrecan was measured by qRT-PCR. Protein levels of silent information regulator 2 homolog 1 (Sirt1), phosphorylated protein kinase B (p-Akt), Akt, collagen type II, SOX-9, and aggrecan were determined by western blot. Results showed that tyrosol attenuated IL-1β-induced viability reduction, apoptosis, and caspase-3/7 activity in HNPCs. The increase in the production of TNF-α, IL-6, NO, and PGE2 in IL-1β-treated HNPCs was abolished by tyrosol treatment. Tyrosol treatment reversed IL-1β-induced upregulation of MMP-3, MMP-9, and MMP-13, and downregulation of collagen II, SOX-9, and aggrecan in HNPCs. Additionally, tyrosol treatment activated the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in IL-1β-stimulated HNPCs. Sirt1 was upregulated by tyrosol, and Sirt1 silencing inhibited Akt phosphorylation in HNPCs. Sirt1 knockdown attenuated the effects of tyrosol on IL-1β-induced apoptosis, inflammation, and ECM remodeling in HNPCs. In summary, upregulation of Sirt1 by tyrosol suppressed apoptosis and inflammation and regulated ECM remodeling in IL-1β-stimulated HNPCs through activation of PI3K/Akt pathway.

Analysis of key genes and pathways associated with the pathogenesis of intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IDD) is widely known as the main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. This study aims to analyze the dataset GSE23130 using bioinformatics methods to identify the pivotal genes and pathways associated with IDD.

MATERIAL/METHODS

The gene expression data of GSE23130 was downloaded, and differentially expressed genes (DEGs) were extracted from 8 samples and 15 controls. GO and KEGG pathway enrichment analyses were performed. Also, protein-protein interaction (PPI) network was constructed and visualized, followed by identification of hub genes and key module.

RESULTS

A total of 30 downregulated and 79 upregulated genes were identified. The DEGs were mainly enriched in the regulation of protein catabolic process, extracellular matrix organization, collagen fibril organization, and extracellular structure organization. Meanwhile, we found that most DEGs were primarily enriched in the PI3K-Akt signaling pathway. The top 10 hub genes were FN1, COL1A2, SPARC, COL3A1, CTGF, LUM, TIMP1, THBS2, COL5A2, and TGFB1.

CONCLUSIONS

In summary, key candidate genes and pathways were identified by using integrated bioinformatics analysis, which may provide insights into the underlying mechanisms and offer potential target genes for the treatment of IDD.

Human Levels of MMP-1 in Degenerated Disks Can Be Mitigated by Signaling Peptides from Mesenchymal Stem Cells

Degradation of extracellular matrix (ECM) in intervertebral disks (IVDs) during IVD degeneration plays a vital role in low back pain (LBP). In healthy IVDs, synthesis and degradation of ECM are kept in balance by matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs. MMPs are enzymes responsible for ECM degradation, and their expression levels are known to increase in degenerated disks. However, the exact pathophysiological concentration of MMP-1 in the degenerated disks of patients with chronic LBP has not been reported previously. Factors secreted by human mesenchymal stem cells (hMSCs) have shown positive results in cell therapy of degenerated disks. The aim of this study was to investigate the pathophysiological MMP-1 concentration (in ng/mL) in degenerated disk tissue and to evaluate if conditioned media (CM) from hMSCs could mitigate the effects of MMP-1 at the detected levels in a 3D in vitro disk cell (DC) pellet model. Tissue levels of MMP-1 were quantified in disk tissue collected from 6 chronic LBP patients undergoing surgery. DC pellet cultures were performed to investigate the effects of MMP-1 alone and the effects of conditioned media (CM) in the presence of MMP-1. MMP-1 was introduced in the pellets on day 14 at concentrations of 5, 50, or 100 ng/mL. The pellets were harvested on day 28 and evaluated for cell viability, proliferation, and ECM production. The mean concentration of MMP-1 in disk tissue was 151 ng/mL. Results from pellet cultures demonstrated a higher number of viable cells, glycosaminoglycan production, and ECM accumulation in the CM group even in the presence of MMP-1 compared to the controls. However, the level decreased with increasing MMP-1 concentration. The results demonstrated that CM has the ability to mitigate matrix degradation property of MMP-1 up to 50 ng/mL suggesting that CM could potentially be used to treat early stages of disk degeneration.

Sequential CCL2 Expression Profile After Disc Injury in Mice

Macrophages produce proinflammatory cytokines in injured intervertebral discs (IVDs). We recently showed that macrophage-derived inflammatory cytokines contribute to the production of pain-related factors. However, the mechanism by which macrophages are recruited to injured IVDs has not been fully clarified. Here, we examined the expression dynamics of the chemokine CCL2 in a mouse IVD injury model and the mechanisms of its regulation. The percentage of macrophages increased from day 1 after injury and persisted up until day 28. At 1 and 3 days after injury, the expression of both Ccl2 messenger RNA (mRNA) and CCL2 protein was elevated in the IVD injury group, after which expression decreased to basal levels. Consistent with the increase in CCL2 expression, Ccr2 and Tnfa expression and various types of macrophages were also immediately elevated following disc injury. Further, tumor necrosis factor-α (TNF-α) stimulated Ccl2 mRNA and CCL2 protein expression in IVD cells in vitro. The expressions of M1 (Cd86 and Nos2) and M2a (Ym1) macrophage markers were all significantly elevated from  day 1 following injury in injured compared with control mice. Meanwhile, the expression of Cd206 (M2a and M2c marker) was significantly elevated on days 3, 7, 14, and 28 following injury. These results suggest that in IVD injury, TNF-α stimulates CCL2, which, in turn, mediates the recruitment of macrophages with the recruited macrophages subsequently differentiating into M1 and M2 subtypes. CCL2 signaling may, therefore, play an important role in IVD pathology via macrophage recruitment. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:895-901, 2020.

Loss of TIMP3 expression induces inflammation, matrix degradation, and vascular ingrowth in nucleus pulposus: A new mechanism of intervertebral disc degeneration

Low back pain (LBP) is one of the most common complains in orthopedic outpatient department and intervertebral disc degeneration (IDD) is one of the most important reasons of LBP. The mechanisms of IDD contain a complex biochemical cascade which includes inflammation, vascular ingrowth, and results in degradation of matrix. In our study, we used both in vitro and in vivo models to investigate the relation between tissue inhibitor of metalloproteinase-3 (TIMP3) expression and IDD. Loss of TIMP3 expression was found in degenerative intervertebral disc (IVD), this change of expression was closely related with the dephosphorylation of smad2/3. Overexpression of TIMP3 significantly inhibited the release of TNF-α and matrix degradation induced by Lipopolysaccharide. Vascular ingrowth was also suppressed by TIMP3 in the in vitro and in vivo models. Further, animal experiments confirmed that the degeneration of IVD was reduced after overexpression of TIMP3 in nucleus pulposus. Taken together, our results indicated TIMP-3 might play an important role in the pathogenesis of IDD and therefore be a potential therapeutic target in the future.

Inflammatory-sensitive CHI3L1 protects nucleus pulposus via AKT3 signaling during intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the main cause of low back pain and the mechanism of which is far from fully revealed. Although inflammation directed nucleus pulposus (NP) extracellular matrix metabolism dysregulation is known to be the main cause of the degeneration process, few is known about the protective factors. Using high-throughput label-free proteomics, we found that inflammation-related autocrine factor Chitinase-3-like protein 1 (CHI3L1, or YKL-40) is highly expressed in the NP cells during degeneration. Immunohistochemical analysis show that the expression of CHI3L1 is NP tissue specific, and increase significantly during degeneration. Overexpression of CHI3L1 significantly decrease the catabolism, and increase the anabolism of extracellular matrix. Knockdown of CHI3L1 using siRNAs show the opposite results, which imply that the protective role of CHI3L1 in IDD. Using high-throughput RNA sequencing and functional analyses, we find that AKT3 expression and its phosphorylation is mainly regulated by CHI3L1. And lastly, the mechanism of which is also validated using human and mouse degenerated NP tissues. In summary, our findings show that the inflammation-related autocrine factor CHI3L1 is NP specific, and it protects IDD by promoting the AKT3 signaling, which may serve as a potential therapeutic target in intervertebral disc degeneration.

Overexpression of TIMP3 inhibits discogenic pain by suppressing angiogenesis and the expression of substance P in nucleus pulposus

Approximately 50% of the cases of low back pain (LBP) are attributed to discogenic origin. The causes of discogenic pain are complicated and consist of a complex biochemical cascade. Neovascularization of intervertebral discs (IVDs) is believed to be associated with discogenic pain. The anti‑angiogenesis ability of tissue inhibitor of metalloproteinase‑3 (TIMP3) has been reported in many tumors, yet whether TIMP3 is associated with neovascularization of IVDs remains unknown. In the present study, both in vitro and in vivo models were used to investigate the association between discogenic pain and TIMP3 expression in nucleus pulposus (NP). PCR results demonstrated that inflammation induced downregulation of TIMP3 expression in NP cells. By using an adenovirus system to upregulate TIMP3 expression, the effect of TIMP3 on angiogenesis was measured by endothelial cell migration and tube formation assays. The results demonstrated that overexpression of TIMP3 suppressed angiogenesis in NP without the regulation of vascular endothelial growth factor (VEGF) expression. TNF‑α converting enzyme (TACE) expression was downregulated by TIMP3, thus inhibiting the TACE‑induced activation of TNF‑α in NP cells. Immunohistochemical staining of IVDs also confirmed that TIMP3 inhibited the expression of substance P in NP. Taken together, the present results indicated the expression of TIMP3 in NP may have a key role in the development of discogenic pain.

Long noncoding RNAs in cancer: From discovery to therapeutic targets

Long noncoding RNAs (lncRNAs) have recently gained considerable attention as key players in biological regulation; however, the mechanisms by which lncRNAs govern various disease processes remain mysterious and are just beginning to be understood. The ease of next-generation sequencing technologies has led to an explosion of genomic information, especially for the lncRNA class of noncoding RNAs. LncRNAs exhibit the characteristics of mRNAs, such as polyadenylation, 5' methyl capping, RNA polymerase II-dependent transcription, and splicing. These transcripts comprise more than 200 nucleotides (nt) and are not translated into proteins. Directed interrogation of annotated lncRNAs from RNA-Seq datasets has revealed dramatic differences in their expression, largely driven by alterations in transcription, the cell cycle, and RNA metabolism. The fact that lncRNAs are expressed cell- and tissue-specifically makes them excellent biomarkers for ongoing biological events. Notably, lncRNAs are differentially expressed in several cancers and show a distinct association with clinical outcomes. Novel methods and strategies are being developed to study lncRNA function and will provide researchers with the tools and opportunities to develop lncRNA-based therapeutics for cancer.

Inflammatory biomarkers in sera of patients with intervertebral disc degeneration

Objective:

To evaluate intervertebral disc levels of inflammatory factor (interleukin 6) and proteinase activity (cathepsin B) in patients with a degenerative disease and serum levels of interleukin 6, serum cathepsin B activity and hyaluronic acid biomarkers.

Methods:

We conducted immunohistochemistry studies of intervertebral discs to analyze interleukin 6 and cathepsin B levels of patients with degenerative disease and spine fracture (Control Group) and to measure hyaluronic acid, interleukin 6 and cathepsin B activity from sera of intervertebral disc degeneration patients, fracture patients, and healthy individuals.

Results:

Interleukin 6 and cathepsin B seem to be related with physiopathology of intervertebral disc degeneration, since the levels of both were higher in discs of patients with intervertebral disc degeneration. Interleukin 6 and cathepsin B do not represent good biomarkers of degenerative intervertebral disc disease, since the level of such compounds is increased in the plasma of patients with fractures.

Conclusion:

Hyaluronic acid can be a biomarker for intervertebral disc degeneration, because hyaluronic acid levels were higher only in sera of patients with intervertebral disc degeneration.

Knockdown of miR-222 inhibits inflammation and the apoptosis of LPS-stimulated human intervertebral disc nucleus pulposus cells

It has been demonstrated that miR‑222 is upregulated in human intervertebral disc (IVD) degeneration tissues; however, the underlying mechanisms remain unclear. In this study, we aimed to elucidate the mechanisms of action of miR‑222 in IVD tissues. Nucleus pulposus (NP) cells were treated with lipopolysaccharide (LPS) to simulate IVD degeneration. The expression level of miR‑222 was detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) in cells and tissues. Cell apoptosis was analyzed by flow cytometry. Additionally, western blot analysis was used to determine the levels of Toll‑like receptor 4 (TLR4), Iκβ‑alpha (IκBα) and p65. Interleukin (IL)‑1β, tumor necrosis factor‑α (TNF‑α) and IL‑6 protein expression levels were determined by enzyme‑linked immunosorbent assay (ELISA). The target gene of miR‑222 was determined by TargetScan7.2 and dual luciferase reporter gene analysis. Western blot analysis and RT‑qPCR were used to determine the mRNA and protein levels of tissue inhibitor of metalloproteinase 3 (TIMP3). The mRNA expression level of miR‑222 was found to be increased in IVD tissues and in LPS‑stimulated cells, and its expression was positively associated with the clinical MRI grade. In vitro, apoptosis was promoted/inhibited by miR‑222 mimics/inhibitors. Transfection with miR‑222 mimics/inhibitors significantly increased/decreased the production of TNF‑α, IL‑1β and IL‑6 and suppressed/enhanced collagen II and aggrecan expression. The protein levels of TLR4, p‑IκΒα and p‑p65 were upregulated/downregulated by transfection with the mimics/inhibitors. In addition, it was demonstrated that TIMP3 was a direct target gene of miR‑222, and was negatively regulated by miR‑222 in NP cells. The silencing of TIMP3 reversed the inhibitory effects of miR‑222 inhibitor on cell apoptosis, which was induced by LPS. Thus, on the whole, the findings of this study demonstrate that miR‑222 functions as a promoter of IVD development, partly via the regulation of TIMP3.

Mechanical loading mediates human nucleus pulposus cell viability and extracellular matrix metabolism by activating of NF-κB

Lower back pain is one of the most frequent complaints in US orthopedic outpatient departments. Intervertebral disc degeneration (IDD) is an important cause of lower back pain. Previous studies have found that mechanical loading was associated with IDD, but the underlying mechanism remains unclear. In the present study, a human nucleus pulposus cell line was used to establish an in vitro mechanical loading model. Mechanical loading, western blot analysis, quantitative PCR, ELISA, cell viability assay and IHC staining were used in the current study. It was found that a short loading time of 4 h followed by a long period of rest (20 h) exerted protective effects against matrix degradation in nucleus pulposus cells, whilst a longer loading time of 20 h followed by a shorter period of rest (4 h) resulted in cell apoptosis and extracellular matrix (ECM) degradation. Excessive mechanical loading may induce ECM degradation by activation of the NF-κB signaling pathway. Taken together, these findings demonstrated that whilst moderate mechanical loading exerted beneficial effects on nucleus pulposus cells, excessive mechanical loading inhibited human nucleus pulposus cell viability and promoted ECM degradation by activating NF-κB.

Berberine prevents human nucleus pulposus cells from IL‑1β‑induced extracellular matrix degradation and apoptosis by inhibiting the NF‑κB pathway

Intervertebral disc degeneration (IDD) is widely considered to be one of the main causes of lower back pain, which is a chronic progressive disease closely related to inflammation, nucleus pulposus (NP) cell apoptosis and extracellular matrix (ECM) degradation. Berberine (BBR) is an alkaloid compound with an anti-inflammatory effect and has been reported to exert therapeutic action in several inflammatory diseases, including osteoarthritis. Therefore, it was hypothesized that BBR may have a therapeutic effect on IDD through inhibition of the inflammatory response. The aim of the present study was to evaluate the influence of BBR on IDD in interleukin (IL)-1β-treated human NP cells in vitro. The results showed that BBR attenuated the upregulation of ECM-catabolic factors [matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-4 and ADAMTS-5], and the downregulation of ECM-anabolic factors (type II collagen and aggrecan) following stimulation of the human NP cells with IL-1β. Treatment with BBR also protected human NP cells from IL-1β-induced apoptosis, as determined by western blotting and flow cytometry. Mechanistically, the IL-1β-stimulated degradation of IκBα, and the phosphorylation and translocation of nuclear factor (NF)-κB p65 were found to be attenuated by BBR, indicating that NF-κB pathway activation was suppressed by BBR in the IL-1β-treated human NP cells. The results of the experiments revealed a therapeutic potential of BBR for the prevention or treatment of IDD.

Nuclear factor-kappa B-dependent X-box binding protein 1 signalling promotes the proliferation of nucleus pulposus cells under tumour necrosis factor alpha stimulation

OBJECTIVES

Tumour necrosis factor alpha (TNF-α) expressed by nucleus pulposus cells (NPCs) plays a critical role in intervertebral disc (IVD) degeneration. A key unfolded protein response (UPR) component, X-box binding protein 1 (XBP1) and nuclear factor-kappa B (NF-κB) are essential for cell survival and proliferation. The aim of our study was to elucidate the roles of XBP1 and NF-κB in IVD degeneration (IDD).

MATERIALS AND METHODS

Rat NPCs were cultured with TNF-α in the presence or absence of XBP1 and NF-κB-p65 small interfering RNA. The associated genes and proteins were evaluated through quantitative real-time PCR, Western blot analyses and immunofluorescence staining to monitor UPR and NF-κB signalling and identify the regulatory mechanism of p65 by XBP1. Cell counting kit-8 assay, cell cycle analysis and related gene and protein expression were performed to examine the proliferation of NPCs.

RESULTS

The acute exposure of TNF-α accelerated the proliferation of rat NPCs by activating the UPR/XBP1 pathway. XBP1 signalling favoured the phosphorylation and nuclear translocation of p65 subunit of NF-κB. The activation of NF-κB in the later phase also enhanced NPC proliferation.

CONCLUSIONS

Unfolded protein response reinforces the survival and proliferation of NPCs under TNF-α stimulation by activating the XBP1 pathway, and NF-κB serves as a vital mediator in these events. The XBP1 signalling of UPR can be a novel therapeutic target in IDD.

Dehydroepiandrosterone: Molecular mechanisms and therapeutic implications in osteoarthritis

Dehydroepiandrosterone (DHEA), a 19-carbon steroid hormone primarily synthesized in the adrenal gland, exerts a chondroprotective effect against osteoarthritis (OA) and has been considered an effective candidate of disease-modifying OA drugs (DMOADs) that slow disease progression. We and others previously demonstrated that DHEA exerted a beneficial effect on osteoarthritic cartilage by positively modulating the balance between anabolic and catabolic factors (e.g., MMPs/TIMP-1, ADAMTS/TIMP-3 and cysteine proteinases/cystatin C), inhibiting catabolic signaling pathways (e.g., Wnt/β-catenin), and suppressing proinflammatory cytokines-mediated low-grade synovial inflammation (e.g., IL-1β). However, the full picture of the pharmacological molecular mechanism(s) underlying the activity of DHEA against OA is still incomplete, and a comprehensive and up-to-date review article in this field is unavailable. In this review, recent findings (apart from the well documented pathogenesis of OA) regarding disease-related mechanisms involving low grade synovial inflammation, cartilage matrix stiffness, chondrocyte autophagy and the roles of a variety of catabolic cellular signaling pathways are discussed. Moreover, the possible relationship between these disease-related mechanisms and DHEA action is discussed. Emerging evidence from in vivo and in vitro studies were scrutinized and are concisely presented to demonstrate the investigational and putative mechanisms underlying the anti-OA potential of DHEA.

MicroRNA-194 Inhibits Lipopolysaccharide-Induced Inflammatory Response in Nucleus Pulposus Cells of the Intervertebral Disc by Targeting TNF Receptor-Associated Factor 6 (TRAF6)

Background

The dramatic increase of intervertebral disc degeneration (IDD) is considered to be a major cause of discogenic low back pain. The current study focused on the regulatory function of microRNA-194 (miR-194) on lipopolysaccharide (LPS)-induced inflammatory response in nucleus pulposus (NP) cells.

Material/Methods

LPS was used to treat NP cells to induce inflammatory responses. MiRNA and gene expression were detected by quantitative PCR. Proteins and protein expression levels were detected by Western blot and ELISA kit. Dual luciferase reporter assay was applied to identify the correlation between an miR-194- and TNF receptor-associated factor 6 (TRAF6) and to test NF-κB activity.

Results

MiR-194 expression was reduced in LPS-induced NP cells. Both miR-194 overexpression and miR-194 inhibitor could regulate extracellular matrix (ECM) genes expression (Aggrecan and collagen II), MMP3, MMP13, ADAMTS4, and ADAMTS5, as well as inflammatory cytokines-associated genes (TNF-α, IL-1, IL-6, PGE2). Through a further study of the molecular mechanism, miR-194 was proved to be involved in the regulation of TRAF6 and its downstream signal molecule, nuclear factor-kappa B (NF-κB).

Conclusions

Finding of our study suggest that miR-194 can inhibit LPS-induced inflammatory response in NP cells of the intervertebral disc (IVD) by targeting TRAF6, which may contribute development of IDD biological therapy.

Dehydroepiandrosterone and Experimental Osteoarthritis

Despite an increased understanding of the pathogenesis of osteoarthritis (OA) and the availability of a number of drugs designed to ameliorate its symptoms, a successful disease-modifying therapy remains elusive. Recent lines of evidence suggest that dehydroepiandrosterone (DHEA), a 19-carbon steroid hormone classified as an adrenal androgen, exerts a chondroprotective effect in OA patients, and it has been proven to be an effective DMOAD candidate that slows OA progression. However, the exact mechanisms underlying its anti-OA effect is largely unknown. This review summarizes emerging observations from studies of cell biology, preclinical animal studies, and preliminary clinical trials and describes the findings of investigations on this topic to develop an initial blueprint of the mechanisms by which DHEA slows OA progression. Presently, studies on DMOADs are increasing in importance but have met limited success. Encouragingly, the current data on DHEA are promising and may prove that DHEA-based treatment is efficacious for preventing and slowing human OA progression.

The Many Facets of Metzincins and Their Endogenous Inhibitors: Perspectives on Ovarian Cancer Progression

Approximately sixty per cent of ovarian cancer patients die within the first five years of diagnosis due to recurrence associated with chemoresistance. The metzincin family of metalloproteinases is enzymes involved in matrix remodeling in response to normal physiological changes and diseased states. Recently, there has been a mounting awareness of these proteinases and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), as superb modulators of cellular communication and signaling regulating key biological processes in cancer progression. This review investigates the role of metzincins and their inhibitors in ovarian cancer. We propose that understanding the metzincins and TIMP biology in ovarian cancer may provide valuable insights in combating ovarian cancer progression and chemoresistance-mediated recurrence in patients.

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.

Dysregulated miR-127-5p contributes to type II collagen degradation by targeting matrix metalloproteinase-13 in human intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IDD) is a chronic disease associated with the degradation of extracellular matrix (ECM). Matrix metalloproteinase (MMP)-13 is a major enzyme that mediates the degradation of ECM components. MMP-13 has been predicted to be a potential target of miR-127-5p. However, the exact function of miR-127-5p in IDD is still unclear.

OBJECTIVE

We designed this study to evaluate the correlation between miR-127-5p level and the degeneration of human intervertebral discs and explore the potential mechanisms.

METHODS

miR-127-5p levels and MMP-13 mRNA levels were detected by quantitative real-time polymerase chain reaction (qPCR). To determine whether MMP-13 is a target of miR-127-5p, dual luciferase reporter assays were performed. miR-127-5p mimic and miR-127-5p inhibitor were used to overexpress or downregulate miR-127-5p expression in human NP cells, respectively. Small interfering RNA (siRNA) was used to knock down MMP-13 expression in human NP cells. Type II collagen expression in human NP cells was detected by qPCR, western blotting, and immunofluorescence staining.

RESULTS

We confirmed that miR-127-5p was significantly downregulated in nucleus pulposus (NP) tissue of degenerative discs and its expression was inversely correlated with MMP-13 mRNA levels. We reveal that MMP-13 may act as a target of miR-127-5p. Expression of miR-127-5p was inversely correlated with type II collagen expression in human NP cells. Moreover, suppression of MMP-13 expression by siRNA blocked downstream signaling and increased type II collagen expression.

CONCLUSION

Dysregulated miR-127-5p contributed to the degradation of type II collagen by targeting MMP-13 in human IDD. Our findings highlight that miR-127-5p may serve as a new therapeutic target in IDD.

Tissue inhibitors of metalloproteinase-expressing cells in human anterior pituitary and pituitary adenoma

Extracellular matrix (ECM) is essential in tissue physiology and pathologic conditions such as tumorigenesis. It affects tumor cell behavior, proliferation, and metastasis. Pituitary adenomas differ in their clinical characteristics, including ECM deposition, and we recently reported that the characteristics of collagen-producing cells differed between control human anterior pituitary gland and pituitary adenomas. ECM deposition is not defined solely by production; degradation and maintenance are also important. Tissue inhibitors of metalloproteinases (TIMPs) help maintain ECM by inhibiting degradation caused by matrix metalloproteases. The present study attempted to characterize TIMP-expressing cells in the human anterior pituitary. Specimens of human pituitary adenomas and control pituitary were obtained during surgery, and in situ hybridization for TIMP1, TIMP2, TIMP3, and TIMP4, followed by immunohistochemistry, was used to characterize TIMP-expressing cells. TIMP expression exhibited a distinct pattern in the human anterior pituitary. Azan staining showed that fibrous matrix deposition varied among pituitary adenomas and that the area of fibrosis was associated with the number and number of types of TIMP3-expressing cells. These results suggest that TIMPs are important in the maintenance of ECM in human pituitary and that TIMP expressions are altered in fibrosis associated with pituitary adenoma.

Protective effects of resveratrol on autologous nucleus pulposus model of radiculopathy

Nucleus pulposus (NP) has been suggested to trigger an autoimmune response if exposed to the immune system, which plays a key role in neuropathic pain. Therefore, appropriate suppression of inflammation is a key factor for treating the radiculopathy caused by intervertebral disk (IVD) degeneration. Resveratrol, a key component of red wine, has been suggested to exhibit anti-inflammatory properties in vitro and in vivo. However, the effects of resveratrol on NP-mediated pain in vivo have not been studied. The aim of the present study was to investigate whether resveratrol may be useful in treating NP-mediated pain in an autologous NP model of radiculopathy. A total of 36 adult male Sprague-Dawley rats were allocated randomly into sham (group I), saline-treated (group II) and resveratrol-treated (group III) groups. Animal behavior in response to non-noxious mechanical stimulation with von Frey filaments was compared at days 0 (baseline), 3, 7, 14 and 21 following surgery. The expression of proinflammatory cytokines such as tumor necrosis factor α (TNF-α) and interleukin-1 (IL-1) were assessed at days 7 and 14. The data showed that resveratrol exhibited an anti-inflammatory effect on the expression of proinflammatory cytokines. Compared with group II, the expression of TNF-α and IL-1 was significantly decreased at each time point in group III. In addition, resveratrol significantly reduced pain behavior triggered by the application of NP tissue on the dorsal root ganglion for up to 14 days. These data suggest that resveratrol has potential for the treatment of NP-mediated pain, indicating a potential clinical application.