Correlation of matrix metalloproteinases-1 and -3 with patient age and grade of lumbar disc herniation

Understanding the etiopathogenesis of lumbar intervertebral disc herniation: From clinical evidence to basic scientific research

Lumbar intervertebral disc herniation, as a leading cause of low back pain, productivity loss, and disability, is a common musculoskeletal disorder that results in significant socioeconomic burdens. Despite extensive clinical and basic scientific research efforts, herniation etiopathogenesis, particularly its initiation and progression, is not well understood. Understanding herniation etiopathogenesis is essential for developing effective preventive measures and therapeutic interventions. Thus, this review seeks to provide a thorough overview of the advances in herniation-oriented research, with a discussion on ongoing challenges and potential future directions for clinical, translational, and basic scientific investigations to facilitate innovative interdisciplinary research aimed at understanding herniation etiopathogenesis. Specifically, risk factors for herniation are identified and summarized, including familial predisposition, obesity, diabetes mellitus, smoking tobacco, selected cardiovascular diseases, disc degeneration, and occupational risks. Basic scientific experimental and computational research that aims to understand the link between excessive mechanical load, catabolic tissue remodeling due to inflammation or insufficient nutrient supply, and herniation, are also reviewed. Potential future directions to address the current challenges in herniation-oriented research are explored by combining known progressive development in existing research techniques with ongoing technological advances. More research on the relationship between occupational risk factors and herniation, as well as the relationship between degeneration and herniation, is needed to develop preventive measures for working-age individuals. Notably, researchers should explore using or modifying existing degeneration animal models to study herniation etiopathogenesis, as such models may allow for a better understanding of how to prevent mild-to-moderately degenerated discs from herniating.

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.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a prevalent cause of low back pain. IVDD is characterized by abnormal expression of extracellular matrix components such as collagen and aggrecan. In addition, it results in dysfunctional growth, senescence, and death of intervertebral cells. The biological pathways involved in the development and progression of IVDD are not fully understood. Therefore, a better understanding of the molecular mechanisms underlying IVDD could aid in the development of strategies for prevention and treatment. Autophagy is a cellular process that removes damaged proteins and dysfunctional organelles, and its dysfunction is linked to a variety of diseases, including IVDD and osteoarthritis. In this review, we describe recent research findings on the role of autophagy in IVDD pathogenesis and highlight autophagy-targeting molecules which can be exploited to treat IVDD. Many studies exhibit that autophagy protects against and postpones disc degeneration. Further research is needed to determine whether autophagy is required for cell integrity in intervertebral discs and to establish autophagy as a viable therapeutic target for IVDD.

Emerging Issues Questioning the Current Treatment Strategies for Lumbar Disc Herniation

Lumbar disc herniation is among the common phenotypes of degenerative lumbar spine diseases, significantly affecting patients' quality of life. The practice pattern is diverse. Choosing conservative measures or surgical treatments is still controversial in some areas. For those who have failed conservative treatment, surgery with or without instrumentation is recommended, causing significant expenditures and frustrating complications, that should not be ignored. In the article, we performed a literature review and summarized the evidence by subheadings to unravel the cons of surgical intervention for lumbar disc herniation. There are tetrad critical issues about surgical treatment of lumbar disc herniation, i.e., favorable natural history, insufficient evidence in a recommendation of fusion surgery for patients, metallosis, and implant removal. Firstly, accumulating evidence reveals immune privilege and auto-immunity hallmarks of human lumbar discs within the closed niche. Progenitor cells within human discs further expand the capacity with the endogenous repair. Clinical watchful follow-up studies with repeated diagnostic imaging reveal spontaneous resolution for lumbar disc herniation, even calcified tissues. Secondly, emerging evidence indicates long-term complications of lumbar fusion, such as adjacent segment disease, pseudarthrosis, implant failure, and sagittal spinal imbalance, which get increasing attention. Thirdly, systemic and local reactions (metallosis) for metal instrumentation have been noted with long-term health concerns and toxicity. Fourthly, the indications and timing for spinal implant removal have not reached a consensus. Other challenging issues include postoperative lumbar stiffness. The review provided evidence from a negative perspective for surgeons and patients who attempt to choose surgical treatment. Collectively, the emerging underlying evidence questions the benefits of traditional surgery for patients with lumbar disc herniation. Therefore, the long-term effects of surgery should be closely observed. Surgical decisions should be made prudently for each patient.

Severity of intervertebral disc herniation regulates cytokine and chemokine levels in patients with chronic radicular back pain

OBJECTIVE

The contributions of intervertebral disc disease and subject-specific covariates to systemic inflammation in low back pain are unknown. We examined the effects of symptomatic disc herniation (DH) and MRI herniation severity on serum cytokine levels in clinical subjects.

DESIGN

Cytokine levels from lumbar DH subjects (N = 78) were compared to control subjects (N = 57) accounting for effects of DH, age, body mass index (BMI) and gender. Effect of DH severity on cytokine levels was analyzed on subsets of subjects with acute or chronic pain. Serum cytokines were also analyzed in a subset of patients between pre- and 3 months post-surgery.

RESULTS

Cytokine levels were elevated in the serum of patients with symptomatic DH, and the covariates age, BMI and gender significantly contributed to levels of some cytokines. Severity of herniation was a significant contributor to pain intensity (VAS), serum levels of HMGB1, PDGFbb, and IL-9. The relationship between DH severity and cytokine levels was confirmed in subjects with chronic, but not acute symptoms. Serum levels of macrophage migration inhibitory factor (MIF) decreased, whereas levels of CCL3, CCL11, CXCL1, and CXCL10 were significantly elevated post surgery.

CONCLUSIONS

This study is the first to show that DH severity is coordinately associated with changes in serum levels of inflammatory cytokines in chronic pain subjects. HMGB1, PDGFbb and IL-9 are novel mediators of increasing DH severity, indicative of cellular damage, neuro-inflammation and angiogenesis. Resolution of inflammation was observed with decrease in MIF post surgery. However, elevated chemokine levels indicate ongoing remodeling and wound healing at 3-month time point.

Expression of degenerative markers in intervertebral discs of young and elderly asymptomatic individuals

Intervertebral disc (IVD) degeneration is a remodeling process mediated by several growth factors and cytokines. This process has been extensively studied in vitro and with pathologic specimens obtained during surgery for scoliosis or back pain. However, the occurrence and temporal evolution of these molecules during normal aging, particularly in the cervical segment, is not known. Our objective was to study and compare the presence of putative mediators in the IVD of young (<35 years, G1) and elderly (>65 years, G2) presumably asymptomatic individuals. Thirty C4-5 and C5-6 discs and thirty L4-5 and L5-S1 discs per group were collected during the autopsy of individuals whose family members denied a history of neck or back pain. Discs were divided into anterior, central (lumbar only) and posterior sectors for analysis. Immunohistochemistry for TNF-α, IL-1β, VEGF, NGF-β, BDNF, TIMP-1, MMP-1, -2 and -3 was performed and reactivity compared between groups and sectors. All of these molecules were detected in every disc sector of both G1 and G2. Most statistical comparisons (25/45, 55.6%) revealed an increase in mediator expression in G2 in relation to G1. Regional differences in the expression of remodeling enzymes were rare; NGF-β and BDNF had slightly higher expression in the cervical segment of elderly individuals. A senescent profile with elevated VEGF, MMP-2 and MMP-3 was observed across most G2 disc regions and were generally elevated from G1. In conclusion, the mere presence of any of the studied molecules inside the IVD cannot be considered pathologic. Expression of remodeling enzymes and inflammatory mediators is relatively similar across different vertebral segments and disc regions leading to a common degenerated pattern, while neurotrophins have slightly higher expression in cervical discs. These findings support the concept that disc remodeling in different segments follows a similar pathway that can be potentially mediated to avoid structural failure.

Increased lactic acid content associated with extracellular matrix depletion in a porcine disc degeneration induced by superficial annular lesion

Background

Degenerative intervertebral disc (IVD) disease can cause lower back pain. However, the change of lactic acid content during disc degeneration process still unclear. The objective of this study was to investigate whether the change of the content of lactic acid is associated with depletion of degenerative intervertebral disc extracellular matrix.

Methods

A total of 18 miniature pigs were equally divided into annular lesion surgery (AL) and sham group. The lateral superficial annulus fibrosus (AF) of T12-L4 discs in AL group were penetrated by 3.5 mm trepan with the depth of 3 mm, the same IVD were only exposed without any injury in the sham group. At 4, 8 and 12 weeks after surgery, the degree of intervertebral disc degeneration was evaluated by magnetic resonance, histological and biochemical analysis.

Results

No obvious degeneration was found in sham group. However, disc degeneration was found and gradually worsened in AL group after surgery. Histological analysis showed that the AF was rupture and disorder, the number of cells in nucleus pulposus (NP) was decreased in AL group. Compared with the sham group, the extent of type II collagen (Col-II) and aggrecan in NP tissue was dramatically decreased in AL group, consistent with the results of Col -II immunohistochemistry staining and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Besides, the gene expression of matrix metallopeptidase 3 and 13 also continuous increased in AL group. The amount of lactic acid and nerve growth factor in NP tissue was gradually increased after operation in AL group.

Conclusions

The content of lactic acid gradually increased after annular lesion, associated with the damage of AF structural and the decrease of Col -II and aggrecan in NP tissue, which leading to the disc degeneration. Depletion of extracellular matrix is consistent with lactic acid accumulation inside of IVD.

Galectins-1 and -3 in Human Intervertebral Disc Degeneration: Non-Uniform Distribution Profiles and Activation of Disease Markers Involving NF-κB by Galectin-1

Degeneration of the human intervertebral disc (IVD) is assumed to underlie severe clinical symptoms, in particular chronic back pain. Since adhesion/growth-regulatory galectins are linked to arthritis/osteoarthritis pathogenesis by activating a pro-degradative/-inflammatory gene expression signature, we hypothesized a similar functional involvement of galectins in IVD degeneration. Immunohistochemical evidence for the presence of galectins-1 and -3 in IVD is provided comparatively for specimens of spondylochondrosis, spondylolisthesis, and spinal deformity. Immunopositivity was detected in sections of fixed IVD specimens in each cellular compartment with age-, disease-, and galectin-type-related differences. Of note, presence of both galectins correlated with IVD degeneration, whereas correlation with age was seen only for galectin-3. In addition, staining profiles for these two galectins showed different distribution patterns in serial sections, an indication for non-redundant functionalities. In vitro, both galectins bound to IVD cells in a glycan-dependent manner. However, exclusively galectin-1 binding triggered a significant induction of functional disease markers (i.e., IL6, CXCL8, and MMP1/3/13) with involvement of the nuclear factor-kB pathway. This study thus gives direction to further network analyses and functional studies on galectins in IVD degeneration. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2204-2216, 2019.

MiR-202-3p regulates interleukin-1β-induced expression of matrix metalloproteinase 1 in human nucleus pulposus

MicroRNAs (miRNAs), small noncoding RNA molecules, have emerged as important factors during intervertebral disc degeneration. This study was to determine whether miR-202-3p regulates interleukin-1β (IL-1β)-induced expression of matrix metalloproteinase 1 (MMP-1) in human nucleus pulposus (NP) cells. Human NP cells were stimulated with IL-1β in vitro. MicroRNA arrays were used to determine the expression profile of 1971 human miRNAs and the miRNAs targets were identified using bioinformatics. In IL-1β-stimulated NP cells, 10 microRNAs were down-regulated, 2 microRNAs were up-regulated. There was a significant reduction in hsa-miR-202-3p (miR-202-3p) expression in the severe degenerative disc compared with mild degenerative disc. Down-regulation of miR-202-3p expression by IL-1β was correlated with up-regulation of MMP-1 expression in human NP cells. IL-1β-induced activation of MAP kinase (MAPK) and nuclear factor-κB (NF-κB) decreased miR-202-3p expression and induced MMP-1 expression. MiR-202-3p suppressed IL-1β-induced MMP-1 production. Conversely, treatment with anti-miR-202-3p remarkably increased MMP-1 production. In addition, mutation of the miR-202-3p binding site in the 3'-UTR of MMP-1 mRNA abolished miR-202-3p-mediated repression of reporter activity. Functional analysis showed that miR-202-3p could decrease type II collagen degradation, whereas overexpression of MMP-1 by Lentiviral-shMMP-1 abolished the effect of miR-202-3p on type II collagen degradation. These results suggest that miR-202-3p is an important regulator of MMP-1 in human nucleus pulposus and may contribute to the development of intervertebral disc degeneration.

Expression and Mechanism of Interleukin 1 (IL-1), Interleukin 2 (IL-2), Interleukin 8 (IL-8), BMP, Fibroblast Growth Factor 1 (FGF1), and Insulin-Like Growth Factor (IGF-1) in Lumbar Disc Herniation

BACKGROUND The expression and mechanism of IL-1, IL-2, IL-8, BMP, FGF1, and IGF-1 in Sprague-Dawley (SD) rats with lumbar disc herniation were investigated. MATERIAL AND METHODS Immunohistochemical methods were applied to identify IL-1, IL-2, IL-8, BMP, FGF1, and IGF-1. PI3K, AKT protein, and mRNA expression were detected and analyzed by Western blot analysis. We selected 30 healthy SD rats and divided them into 2 groups to construct an animal model that was validated by immediate CT scanning. Cartilage tissues from the lumbar disc herniation (experimental) group and control group were obtained and compared. RESULTS The expression of BMP was not significantly different between the control group and the experimental group (P>0.05). FGF1: There was no significant difference in the expression of FGF1 (P>0.05) between the control group and the experimental group. Compared with the control group, the expression of IGF-1 in the experimental group was significantly higher (P<0.05); the expression of IL-1 in the experimental group was significantly higher (P<0.05); and the expression of IL-2 in the experimental group was also significantly higher (P<0.05). There was no significant difference in IL-8 between the experimental group and the control group (P>0.05). The expression levels of PI3K and AKT protein and mRNA were significantly higher than those in healthy controls (P<0.05). CONCLUSIONS After lumbar disc herniation occurred, the IGF-1 was first activated; the PI3K/AKT signaling pathway was later activated, which resulted in the expression of IL-1 and IL-2 inflammation-related factors being increased.

Differences in the Incidence of Symptomatic Cervical and Lumbar Disc Herniation According to Age, Sex and National Health Insurance Eligibility: A Pilot Study on the Disease's Association with Work

The aim of this research was to identify the differences in the incidence of symptomatic cervical and lumbar disc herniation according to age, sex, and national health insurance eligibility. We evaluated the hospital documents of patients who received medical treatment for symptomatic cervical and lumbar disc herniation between 2004 and 2010 and excluded those who claimed to have expenses at oriental medical clinics or pharmacies. Furthermore, any duplicate documents from the labor force population aged 20⁻69 years were excluded from the analysis. The results showed that the number of individuals diagnosed with symptomatic cervical and lumbar disc herniation increased with age, and the incidence of these diseases was higher in women than in men. Additionally, the incidence differed depending on the subject's qualification for health insurance. The incidence of lumbar disc herniation showed differences depending on the degree of the lumbar burden. The present study findings may help determine whether lumbar disc herniation is associated with tasks performed at the patient's workplace. Further research is needed to classify the risk of lumbar disk herniation in the workplace into detailed categories such as types of business, types of occupation, and lumbar compression force.

Correlation of matrix metalloproteinase (MMP)-1, -2, -3, and -9 expressions with demographic and radiological features in primary lumbar intervertebral disc disease

Degeneration of IVD is a progressive and irreversible process and can be evaluated with immunohistochemical examination or radiological grading. MMPs are a family of proteolytic enzymes and involved in the degradation of the matrix components of the IVD. We aimed to compare MMP-1, -2, -3, and -9 expressions with demographic features, visual analogue scale (VAS), Oswestry Disability Index (ODI) and radiological (MRI) grades. The study involved 60 participants. We recorded data about age, complaint, radiological imaging, expression levels of MMP-1, -2, -3, and -9, ODI and VAS for back pain retrospectively. Intervertebral disc degeneration was graded on a 0-5 scale according to the Pfirrmann classification. As a result of the study, the median age was 52.09±12.74years. There were statistical significances between age and MMP-1, and MMP-2. There was a close correlation between grade and MMP-9. We found correlation between the VAS and the MMP-9 expression. In addition, there was relationship between expression of MMP-2 and MMP-1, MMP-3, MMP-9. In conclusion, the expressions of MMP-1 and -2 are increased with aging. There was no relationship between radiological evaluation of IVDD and aging. Increased expression of MMPs affected IVDD positively. The relationship with MMPs is not explained. This study adds to our understanding of the interaction between MMPs and IVDD.

Spontaneous regression of herniated lumbar discs: Report of one illustrative case and review of the literature

Lumbar disc herniation (LDH) is a common disease that induces back pain and radicular pain. The most efficient method for the treatment of lumbar disc herniation is still controversial. Spontaneous regression of LDH has been recognized with the advancement of radiological diagnostic tools and can explain the reason of spontaneous relief of symptoms without treatment. The proposed hypotheses are; dehydration, retraction of the disc to the hernia in the annulus fibrosis, enzymatic catabolism and phagocytosis. In this study, the case of a patient with huge lumbar disc hernia regressing by itself has been presented and the potential mechanisms of disc regression have been discussed.

Aging and degeneration of the intervertebral disc: review of basic science

<p>Currently there is a growing interest in the study of intervertebral discs due to loss of manpower brought to society by low back and neck pains. These papers seek to delineate the difference between normal aging and disc degeneration, trying to understand what factor would be determining for the second condition. Thus, the morphology field was expanded and knowledge on the structure of intervertebral discs currently uses the research field of cell and molecular biology, and genetics. The results indicate that regardless of age or condition, the intervertebral disc undergoes long and extensive remodeling of its constituents, which are influenced by several factors: environmental, soluble, cell growth and extracellular matrix. In this literature review we describe the biological characteristics of the cervical and lumbar intervertebral disc with a focus on basic science of aging and degeneration, selecting the latest findings and discussions of the area, which influence future research and clinical thoughts.</p>

MicroRNA-93 regulates collagen loss by targeting MMP3 in human nucleus pulposus cells

OBJECTIVES

Degenerated disc disease is one of the most common medical conditions in patients suffering from low back pain. Recent studies have shown that microRNAs can regulate cell function in many pathological conditions. The aim of this study was to investigate expression and role of miR-93 in disc degeneration.

MATERIALS AND METHODS

Quantitative RT-PCR was employed to investigate level of miR-93 in degenerative nucleus pulposus (NP) tissues. Then, functional analysis of miR-93 in regulating collagen II expression was performed. Subsequently, western blotting and luciferase reporter assay were used to detect the target gene.

RESULTS

We showed that miR-93 was significantly down-regulated in degenerative NP tissues and its levels were associated with grade of disc degeneration. Overexpression of miR-93 stimulated type II collagen expression in NP cells. Moreover, MMP3 was identified as a putative target of miR-93. MiR-93 inhibited MMP3 expression by directly targeting its 3'UTR, and this was abolished by miR-93 binding site mutations. Additionally, restoration of MMP3 in miR-93-overexpressed NP cells reversed effects of type II collagen expression. Expression of MMP3 inversely correlated with miR-93 expression in degenerative NP tissues.

CONCLUSIONS

Taken together, we demonstrated that miR-93 contributed to abnormal NP cell type II collagen expression by targeting MMP3, involved in intervertebral disc degeneration.

Developments in intervertebral disc disease research: pathophysiology, mechanobiology, and therapeutics

Low back pain is a leading cause of disability worldwide and the second most common cause of physician visits. There are many causes of back pain, and among them, disc herniation and intervertebral disc degeneration are the most common diagnoses and targets for intervention. Currently, clinical treatment outcomes are not strongly correlated with diagnoses, emphasizing the importance for characterizing more completely the mechanisms of degeneration and their relationships with symptoms. This review covers recent studies elucidating cellular and molecular changes associated with disc mechanobiology, as it relates to degeneration and regeneration. Specifically, we review findings on the biochemical changes in disc diseases, including cytokines, chemokines, and proteases; advancements in disc disease diagnostics using imaging modalities; updates on studies examining the response of the intervertebral disc to injury; and recent developments in repair strategies, including cell-based repair, biomaterials, and tissue engineering. Findings on the effects of the omega-6 fatty acid, linoleic acid, on nucleus pulposus tissue engineering are presented. Studies described in this review provide greater insights into the pathogenesis of disc degeneration and may define new paradigms for early or differential diagnostics of degeneration using new techniques such as systemic biomarkers. In addition, research on the mechanobiology of disease enriches the development of therapeutics for disc repair, with potential to diminish pain and disability associated with disc degeneration.

Trend of the incidence of lumbar disc herniation: decreasing with aging in the elderly

BACKGROUND

Compelling evidence has shown that the incidence of lumbar disc herniation (LDH) increases with age. In this study, retrospective clinical analysis of 601 cases of LDH has been conducted to investigate the role of age in the incidence of LDH in the elderly. The aim of the study is to investigate the relationship between the process of aging and the occurrence of LDH in old adults.

METHODS

Clinical cases (n = 601) of LDH were retrospectively analyzed.

RESULTS

The imaging examination with computed tomography and/or magnetic resonance imaging showed the occurrence of degeneration in LDH patients over 65 years of age. The most common site of LDH is toward the bottom of the spine at L4-L5 and/or L5-S1. The incidence of LDH drops with age in the elderly, especially after the age of 80 years. There is an obvious decrease in LDH in the elderly female.

CONCLUSION

A decreasing incidence of LDH with aging occurs in the elderly. This investigation indicates that aging is not a contributor to the performance of LDH in the elderly although the incidence of LDH is proportional to age.

Relationship between neovascularization and degenerative changes in herniated lumbar intervertebral discs

PURPOSE

Lumbar disc degeneration may be associated with intensity of neovascularization in disc herniations. Our study was designed to evaluate how much the severity of histodegeneration is related to the development of neovascularization and to the level of pleiotrophin in the herniated lumbar discs.

METHODS

Surgically excised lumbar disc specimens were obtained from 29 patients with noncontained (i.e., extruding through the posterior longitudinal ligament) and 21 patients with contained disc herniations. The histodegeneration scores and levels of neovascularization were estimated according to semiquantitative analysis in lumbar disc and endplate samples. Immunohistochemical staining were performed to identify the newly formed blood vessels and to detect the presence of pleiotrophin in the specimens.

RESULTS

Higher levels of disc and endplate neovascularity were registered in noncontained herniations. The level of neovascularization was significantly related to the score of histodegeneration in the herniated disc tissues but not in the endplate specimens. Both contained and noncontained herniations had the highest values of histodegeneration in conjunction with the highest level of neovascularization but the relations between neovascularity and degenerative changes remained to be significant only in the group of noncontained herniations. Registration or frequency of pleiotrophin positive cells did not correlate significantly with histodegeneration or level of neovascularization in the disc samples.

CONCLUSION

Severe histodegeneration of the lumbar disc herniations is associated with enhanced neovascularization and potentially also spontaneous regression of the herniated tissue.

Investigation of the relationship between chromobox homolog 8 and nucleus pulposus cells degeneration in rat intervertebral disc

Here, we aimed to investigate the expression of chromobox homolog 8 (CBX8) in nucleus pulposus (NP) cells from rat intervertebral disc (IVD) and its function in DNA damage and repair. NP cells were isolated from healthy rat IVD for immunohistochemistry staining. Small interfering RNA (siRNA) of CBX8 was applied for gene silencing, and reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to determine mRNA levels of CBX8, type II collagen, and proteoglycans. Cell proliferation and cell cycle were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony-forming assay, and flow cytometry. Hydrogen peroxide (H2O2) was added to simulate DNA oxidative damage, and expression of CBX8 was examined using RT-PCR and Western blot. After five passages, mRNA levels of type II collagen and proteoglycans decreased but that of CBX8 increased. When CBX8 was silenced by siRNA, the expressions of CBX8, type II collagen and proteoglycans declined, and the cell growth was inhibited. Besides, cell cycle was slowed down as most cells were arrest in G0/G1 phase. Furthermore, CBX8 expression went up responding to DNA oxidative damage caused by H2O2. The data indicated that CBX8 plays important roles in cell proliferation and DNA damage. Cell proliferation and cell cycle were stimulated by CBX8, which may be associated with INK4A-ARF pathway. Moreover, CBX8 plays a role in DNA damage which made it a potential gene therapy target for treatment of disc degeneration.

Association of endothelin-1 expression and cartilaginous endplate degeneration in humans

Background

Inflammatory cytokines are involved in intervertebral disc (IVD) degeneration. Endothelin-1 (ET-1), a 21-amino-acid cytokine implicated with cartilage degradation, is secreted by vascular endothelial cells and also by many other cell types. The expression of ET-1 in human IVD cartilage endplate (CEP) and its role in disc degeneration have not been explored.

Methods and Findings

The expression of ET-1 in degenerated CEP was analyzed by immunohistochemical staining and Western blotting; ET-1 was demonstrated in cartilaginous endplate cells (CECs) by immunofluorescent staining. The ET-1 mRNA expression and protein production by CECs stimulated by tumor necrosis factor alpha (TNF-α), a pro-inflammatory cytokine, were determined by real-time PCR analysis and Western blotting, respectively. The matrix metalloprotease-1 (MMP-1), MMP-13 and tissue inhibitor of metalloproteases-1 (TIMP-1) levels in the supernatant of cultured CECs treated with ET-1 were determined using enzyme-linked immunosorbent assays. Nitric oxide (NO) release and nitric oxide synthase (NOS) activity were measured using a spectrophotometric assay. The apoptosis of CECs by ET-1 was measured by an Annexin V-FITC detection assay. The production of ET-1 in degenerated cartilage endplate was significantly higher than normal CEP. The results showed that ET-1 was expressed by CECs and modulated by TNF-α in a dose-dependent manner. ET-1 increased production of MMP-1 and MMP-13, decreased TIMP-1 production, and induced NO and NOS release by cultured CECs. The direct stimulation of CECs by ET-1 did not promote cell apoptosis.

Conclusion

The study results suggest that ET-1 played a pivotal role in human CEP degeneration, and may be a new target for development of therapies for this condition.

Osthole, a herbal compound, alleviates nucleus pulposus-evoked nociceptive responses through the suppression of overexpression of acid-sensing ion channel 3 (ASIC3) in rat dorsal root ganglion

BACKGROUND

Osthole (Ost), a natural coumarin derivative, has been shown to inhibit many pro-inflammatory mediators and block voltage-gated Na+ channels. During inflammation, acidosis is an important pain inducer which activates nociceptors by gating depolarizing cationic channels, such as acid-sensing ion channel 3 (ASIC3). The aim of this study was to examine the effects of Ost on nucleus pulposus-evoked nociceptive responses and ASIC3 over-expression in the rat dorsal root ganglion, and to investigate the possible mechanism.

MATERIAL/METHODS

Radicular pain was generated with application of nucleus pulposus (NP) to nerve root. Mechanical allodynia was evaluated using von Frey filaments with logarithmically incremental rigidity to calculate the 50% probability thresholds for mechanical paw withdrawal. ASIC3 protein expression in dorsal root ganglions (DRGs) was assessed with Western blot and immunohistochemistry. Membrane potential (MP) shift of DRG neurons induced by ASIC3-sensitive acid (pH6.5) was determined by DiBAC(4) (3) fluorescence intensity (F.I.).

RESULTS

The NP-evoked mechanical hyperalgesia model showed allodynia for 3 weeks, and ASIC3 expression was up-regulated in DRG neurons, reaching peak on Day 7. Epidural administration of Ost induced a remarkable and prolonged antinociceptive effect, accompanied by an inhibition of over-expressed ASIC3 protein and of abnormal shift of MP. Amiloride (Ami), an antagonist of ASIC3, strengthened the antinociceptive effect of Ost.

CONCLUSIONS

Up-regulation of ASIC3 expression may be associated with NP-evoked mechanical hyperalgesia. A single epidural injection of Ost decreased ASIC3 expression in DGR neurons and the pain in the NP-evoked mechanical hyperalgesia model. Osthole may be of great benefit for preventing chronic pain status often seen in lumbar disc herniation (LDH).

The role of matrix metalloproteinase 9 in intervertebral disc degeneration

The present study investigates the histological alterations and expression of matrix metalloproteinase 9 (MMP-9) in disc specimens of 43 patients who underwent surgery for lumbar disc herniation. The immunostaining for MMP-9 was evaluated semi-quantitatively. Histologic degeneration was scored between 0 and 12 depending on the degree of chondrocyte proliferation and presence of tears and clefts, granular changes and mucous degeneration. Herniation was graded as grade 1 (protrusion), grade 2 (extrusion) or grade 3 (sequestration) on MRI. Although there was no significant statistical difference between the histologic degeneration score and age, degenerative changes were more pronounced in higher grade of herniation (p<0.0001). MMP-9 expression was related to histologic degenerative score in all age groups (p=0.0065). MMP-9 was also related to herniation grade in patients younger than 30 years of age (p=0.0037). No significant association was found between MMP-9 expression and herniation grade in patients who were 30-60 years or over 60 years of age.