Tumor necrosis factor-α levels correlate with postoperative pain severity in lumbar disc hernia patients: opposite clinical effects between tumor necrosis factor receptor 1 and 2

TNFR1-mediated senescence and lack of TNFR2-signaling limit human intervertebral disc cell repair in back pain conditions

Poor intervertebral disc (IVD) healing causes IVD degeneration (IVDD) and progression to herniation and back pain. This study identified distinct roles of TNFα-receptors (TNFRs) in contributing to poor healing in painful IVDD. We first isolated IVDD tissue of back pain subjects and determined the complex pro-inflammatory mixture contained many chemokines for recruiting inflammatory cells. Single-cell RNA-sequencing of human IVDD tissues revealed these pro-inflammatory cytokines were dominantly expressed by a small macrophage-population. Human annulus fibrosus (hAF) cells treated with IVDD-conditioned media (CM) underwent senescence with greatly reduced metabolic rates and limited inflammatory responses. TNFR1 inhibition partially restored hAF cell metabolism sufficiently to enable a robust chemokine and cytokine response to CM. We showed that the pro-reparative TNFR2 was very limited on hIVD cell membranes so that TNFR2 inhibition with blocking antibodies or activation using Atsttrin had no effect on hAF cells with CM challenge. However, TNFR2 was expressed in high levels on macrophages identified in scRNA-seq analyses, suggesting their role in repair responses. Results therefore point to therapeutic strategies for painful IVDD involving immunomodulation of TNFR1 signaling in IVD cells to enhance metabolism and enable a more robust inflammatory response including recruitment or delivery of TNFR2 expressing immune cells to enhance IVD repair.

Intradiscal inflammatory stimulation induces spinal pain behavior and intervertebral disc degeneration in vivo

Degeneration of the intervertebral disc (IVD) results in a range of symptomatic (i.e., painful) and asymptomatic experiences. Components of the degenerative environment, including structural disruption and inflammatory cytokine production, often correlate with pain severity. However, the role of inflammation in the activation of pain and degenerative changes has been complex to delineate. The most common IVD injury model is puncture; however, it initiates structural damage that is not representative of the natural degenerative cascade. In this study, we utilized in vivo injection of lipopolysaccharide (LPS), a pro-inflammatory stimulus, into rat caudal IVDs using 33G needles to induce inflammatory activation without the physical tissue disruption caused by puncture using larger needles. LPS injection increased gene expression of pro-inflammatory cytokines (Tnfa, Il1b) and macrophage markers (Inos, Arg1), supported by immunostaining of macrophages (CD68, CCR7, Arg1) and systemic changes in blood cytokine and chemokine levels. Disruption of the IVD structural integrity after LPS injection was also evident through changes in histological grading, disc height, and ECM biochemistry. Ultimately, intradiscal inflammatory stimulation led to local mechanical hyperalgesia, demonstrating that pain can be initiated by inflammatory stimulation of the IVD. Gene expression of nociceptive markers (Ngf, Bdnf, Cgrp) and immunostaining for neuron ingrowth (PGP9.5) and sensitization (CGRP) in the IVD were also shown, suggesting a mechanism for the pain exhibited. To our knowledge, this rat IVD injury model is the first to demonstrate local pain behavior resulting from inflammatory stimulation of caudal IVDs. Future studies will examine the mechanistic contributions of inflammation in mediating pain.

Repair of degenerative nucleus pulposus by polyphenol nanosphere-encapsulated hydrogel gene delivery system

Intervertebral disc degeneration (IDD) progresses due to local inflammatory response, gradually unbalanced anabolic/catabolic activity, and progressive functional impairment within the nucleus pulposus. Antagomir-21, a cholesterol-modified miRNA-21 inhibitor, has potential extracellular matrix (ECM) regenerative ability, but its application for IDD is limited by inadequate local delivery systems. An injectable hydrogel gene delivery system encapsulating a modified tannic acid nanoparticles (TA NPs) vector was engineered for on-demand and sustained delivery of antagomir-21 into the nucleus pulposus. After nucleus pulposus cell uptake, antagomir-21 was released from TA NPs and regulated the ECM metabolic balance by inhibiting the MAPK/ERK signaling pathway. TA NPs scavenged intracellular ROS and reduced inflammation by downregulating TNF-α expression. In vivo, synergistic anti-inflammatory effects and ECM regeneration effectively promoted therapeutic efficacy against IDD. This hydrogel gene delivery system represents a creative, promising strategy for IDD repair.

Regulatory Effect of Inflammatory Mediators in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is a major contributor to back, neck, and radicular pain. It is related to changes in tissue structure and function, including the breakdown of the extracellular matrix (ECM), aging, apoptosis of the nucleus pulposus, and biomechanical tissue impairment. Recently, an increasing number of studies have demonstrated that inflammatory mediators play a crucial role in IDD, and they are being explored as potential treatment targets for IDD and associated disorders. For example, interleukins (IL), tumour necrosis factor-α (TNF-α), chemokines, and inflammasomes have all been linked to the pathophysiology of IDD. These inflammatory mediators are found in high concentrations in intervertebral disc (IVD) tissues and cells and are associated with the severity of LBP and IDD. It is feasible to reduce the production of these proinflammatory mediators and develop a novel therapy for IDD, which will be a hotspot of future research. In this review, the effects of inflammatory mediators in IDD were described.

Investigation of macrophage polarization in herniated nucleus pulposus of patients with lumbar intervertebral disc herniation

Macrophage infiltration and polarization during lumbar intervertebral disc herniation (LDH) have attracted increased attention but their role remains unclear. To explore macrophage polarization in herniated nucleus pulposus (NP) tissue of patients with LDH and investigate the association between cell frequency and different clinical characteristics or symptoms, we conducted a retrospective study by analyzing NP tissue samples from 79 patients. Clinical features and symptoms, using the visual analog scale (VAS) and Oswestry disability index (ODI), were collected. The macrophage markers CD68, CCR7, CD163, and CD206; pro-inflammatory cytokine TNF-α; and anti-inflammatory factor IL-4 were analyzed by immunohistochemistry. The frequency of polarized macrophages and positivity rate of pro- and anti-inflammatory cytokines showed significant differences in some of clinical characteristics. Specifically, higher CCR7⁺ and TNF-α + proportions were identified in the high-intensity zone (HIZ) and the type of extrusion and sequestration NP tissue than in non-HIZ and protrude NP tissue. Higher CD206⁺ and IL-4+ proportion were detected in Modic changes. However, no differences in gender, age, smoking status, Pfirrmann grade, analgesic use, leg pain duration, and segments were found between groups. CD68⁺ , CCR7⁺ , and CD206⁺ cell proportions, and TNF-α and IL-4 showed positive associations with VAS scores preoperation. Associations between ODI and the macrophages markers were weak/insignificant. Our results indicated that macrophage polarization or macrophage-like cells contribute to LDH pathological features. Macrophage populations displaying significant associations with VAS score reflected continuous M1/M2 transition contributing to pain during LDH. These findings may contribute to enhanced/personalized pharmacological interventions for patients with LDH considering pain heterogeneity.

Intervertebral Disc-on-a-Chip as Advanced In Vitro Model for Mechanobiology Research and Drug Testing: A Review and Perspective

Discogenic back pain is one of the most diffused musculoskeletal pathologies and a hurdle to a good quality of life for millions of people. Existing therapeutic options are exclusively directed at reducing symptoms, not at targeting the underlying, still poorly understood, degenerative processes. Common intervertebral disc (IVD) disease models still do not fully replicate the course of degenerative IVD disease. Advanced disease models that incorporate mechanical loading are needed to investigate pathological causes and processes, as well as to identify therapeutic targets. Organs-on-chip (OoC) are microfluidic-based devices that aim at recapitulating tissue functions in vitro by introducing key features of the tissue microenvironment (e.g., 3D architecture, soluble signals and mechanical conditioning). In this review we analyze and depict existing OoC platforms used to investigate pathological alterations of IVD cells/tissues and discuss their benefits and limitations. Starting from the consideration that mechanobiology plays a pivotal role in both IVD homeostasis and degeneration, we then focus on OoC settings enabling to recapitulate physiological or aberrant mechanical loading, in conjunction with other relevant features (such as inflammation). Finally, we propose our view on design criteria for IVD-on-a-chip systems, offering a future perspective to model IVD mechanobiology.

Distinctive roles of tumor necrosis factor receptor type 1 and type 2 in a mouse disc degeneration model

Background

Elevated tumor necrosis factor alpha (TNF-α) expression is correlated with the progression of intervertebral disc degeneration (IVDD). Progranulin binding to tumor necrosis factor receptor (TNFR) and its derivative Atsttrin are effective for treating inflammatory arthritis. We hypothesize that Atsttrin has a protective effect in IVDD through different roles of TNFR receptor type 1 (TNFR1) and TNFR receptor type 2 (TNFR2) in degenerated discs.

Methods

IVDD models were established in TNFR1^−/−, TNFR2^−/− mice and their control littermates. Nucleus Pulpous (NP) samples from human patients and IVDD murine models were evaluated by X-ray, micro-MRI, μCT, histological staining and immunofluorescence staining. NP cells isolated from wild-type (WT), TNFR1^−/− and TNFR2^−/− mice were treated with TNF-α or Atsttrin and then assayed by Western blotting, qRT–PCR, and ELISA.

Results

TNFR1 and TNFR2 expression was significantly elevated in the disc tissues of both human patients and IVDD murine models. TNFR1 knockout contributed to reduced disc degeneration. In contrast, TNFR2 knockout was associated with enhanced IVDD severity, including degraded cellular composition, increased cell apoptosis and elevated vertebral destruction. Atsttrin protected against IVDD in WT and TNFR1^−/− mouse models but had no effect in TNFR2^−/− IVDD models. Additionally, in vitro NP cell-based assays demonstrated that TNF-α-stimulated catabolism and Atsttrin-activated anabolism depended on TNFR1 and TNFR2, respectively.

Conclusion

TNFR1 is associated with the degenerative progression of IVDD, while TNFR2 contributes to the protective effect on the discs. Atsttrin protects against IVDD at least partially by inhibiting the TNFα/TNFR1 inflammatory/catabolic pathway and activating the TNFR2 protective/anabolic pathway.

The translational potential of this article

This study demonstrates that TNFR1 and TNFR2 have disparate roles in disc degeneration and hlights the potential use of Atsttrin as a therapeutic agent against IVDD in mice.

Degenerative disc disease in young adults: cytokine profile and angiogenic factors

Back pain (BP), associated with the degenerative disc disease (DDD), poses a heavy social and economic burden due to early disability and indications to surgery, emerging in young adults. Pathophysiological basis of premature intervertebral disc (IVD) degeneration is being actively studied. The study was aimed to define the profiles of inflammatory cytokines in DDD, as well as their relationship to the structural spine diseases. The molecular genetic analysis of the mRNA gene abundance in patients with BP and herniated IVD after discectomy and healthy individuals was performed by the quantitative polymerase chain reaction method. High expression of TNFα, IL17 was revealed in the IVD tissues of the affected patients (p < 0.01); the levels of TNFα and IL1β correlated with the DDD severity (r = 0.301 and 0.37; p < 0.05). Elevated expression of IL1β, IL6 was found in peripheral white blood cells (p < 0.01); the levels of IL6 negatively correlated with Modic type 1 and 2 changes (r = –0.31; p < 0.05), and the levels of IL17 positively correlated with the IVD herniation in combination with erosions of the adjacent vertebral body endplates and Modic changes (r = 0.401; p < 0.05). The expression of VEGF-А in the IVD tissues and white blood cells negatively correlated with the DDD grades (r = –0.85; p < 0.001), indicating reduced vascularization in the terminal phase of the disease. The findings on DDD demonstrate the contribution of the local low-immune inflammation, coupled with the intense disc vascularization at the earlier stages, and associated with the reactive inflammation in vertebral bodies. The results are prerequisites for developing the anti-inflammatory and reparative therapy based on the DDD grade and the presence of Modic changes in young adults with BP.

TNF-ɑ Induces Methylglyoxal Accumulation in Lumbar Herniated Disc of Patients With Radicular Pain

Lumbar disc herniation (LDH) with radicular pain is a common and complicated musculoskeletal disorder. Our previous study showed that LDH-induced methylglyoxal (MG) accumulation contributed to radicular pain. The underlying mechanisms through which MG accumulates are poorly understood. In the present study, we found that both MG and tumor necrosis factor-alpha (TNF-ɑ) levels in the herniated disc of patients with radicular pain were significantly increased, and the activity of Glyoxalase 1 (GLO1), the rate-limiting enzyme that metabolizes MG, was decreased. In rats, the LDH model was mimicked by implantation of autologous nucleus pulposus (NP) to the left lumbar five spinal nerve root. The mechanical allodynia was observed in LDH rats. Besides, MG and TNF-ɑ levels were increased, and GLO1 activity was significantly decreased in the implanted NP. In cultured rat NP cells, stimulation with the inflammatory mediator TNF-ɑ reduced GLO1 activity and expression. These results suggested that TNF-ɑ-induced GLO1 activity decrease contributed to MG accumulation in the herniated disc of patients with radicular pain.

Study protocol: effect of infection, Modic and inflammation on clinical outcomes in surgery for radiculopathy (EIMICOR)

BACKGROUND

Evidence indicates that inflammatory processes are involved in radicular pain as well as in resorption of herniated disc tissue. Furthermore there are indications that the presence of vertebral end plate pathology (Modic changes; MC) is associated with a negative effect on inflammation. It is hypothesized that in patients with MC, the (possibly bacterial induced) inflammation will be accompanied by pro inflammatory cytokines that worsen the outcome, and that in patients without MC, the inflammation is accompanied by cytokines that induce a resorption process to accelerate recovery.

METHODS

This prospective cohort study will include 160 lumbar and 160 cervical patients (total of 320), which are scheduled for surgery for either a lumbar or cervical herniated disc with ages between 18 and 75. The main and interaction effects of local bacterial infection (culture), inflammatory cells in disc material (immunohistology), MC (MRI), and blood biomarkers indicating inflammation or infection (blood sample evaluation) will be evaluated. Clinical parameters to be evaluated are leg pain on the 11 point NRS pain scale, Oswestry (lumbar spine) or Neck (cervical spine) Disability Index, Global Perceived Recovery, Womac Questionnaire, and medication status, at baseline, and after 6, 16, 26 and 52 weeks.

DISCUSSION

Gaining insight in the aetiology of pain and discomfort in radiculopathy caused by a herniated disc could lead to more effective management of patients. If the type of inflammatory cells shows to be of major influence on the rate of recovery, new immunomodulating treatment strategies can be developed to decrease the duration and intensity of symptoms. Moreover, identifying a beneficial inflammatory response in the disc through a biomarker in blood could lead to early identification of patients whose herniations will resorb spontaneously versus those that require surgery.

TRIAL REGISTRATION

prospectively enrolled at trialregister.nl, ID: NL8464 .

Pathomechanism and Biomechanics of Degenerative Disc Disease: Features of Healthy and Degenerated Discs

The human intervertebral disc (IVD) is a complex organ composed of fibrous and cartilaginous connective tissues, and it serves as a boundary between 2 adjacent vertebrae. It provides a limited range of motion in the torso as well as stability during axial compression, rotation, and bending. Adult IVDs have poor innate healing potential due to low vascularity and cellularity. Degenerative disc disease (DDD) generally arises from the disruption of the homeostasis maintained by the structures of the IVD, and genetic and environmental factors can accelerate the progression of the disease. Impaired cell metabolism due to pH alteration and poor nutrition may lead to autophagy and disruption of the homeostasis within the IVD and thus plays a key role in DDD etiology. To develop regenerative therapies for degenerated discs, future studies must aim to restore both anatomical and biomechanical properties of the IVDs. The objective of this review is to give a detailed overview about anatomical, radiological, and biomechanical features of the IVDs as well as discuss the structural and functional changes that occur during the degeneration process.

Inhibition of TNFR1 Attenuates LPS Induced Apoptosis and Inflammation in Human Nucleus Pulposus Cells by Regulating the NF-KB and MAPK Signalling Pathway

Intervertebral disc degeneration (IDD) is accompanied by nucleus pulposus (NP) cell apoptosis, inflammation, and extracellular matrix degradation. Tumour necrosis factor receptor 1 (TNFR1) is a receptor of TNF-α, and is deeply involved in the processes of IDD. However, the effect of TNFR1 inhibition on IDD is not clear. Herein, we report that TNFR1 was increased in LPS-treated HNPCs. The aim of this study was to investigate the potential therapeutic effect of TNFR1 siRNA and selective antagonists of TNFR1 (GSK1995057) on HNPC damage. The results showed that the blockade of TNFR1 by TNFR1 siRNA and GSK1995057 effectively suppressed the cell viability loss, apoptosis, and inflammation induced by LPS in HNPCs. Furthermore, we found that TNFR1 siRNA and GSK1995057 inhibited activation of the NF-KB and MAPK signalling pathways in LPS-stimulated HNPCs. In summary, the blockade of TNFR1 effectively suppressed LPS-induced apoptosis and inflammation in HNPCs through the NF-KB and MAPK signalling pathways. This revealed that the blockade of TNFR1 may provide a potential therapeutic treatment for IDD.

Inflammation in the intervertebral disc herniation

Up until fairly recently, it was thought that sciatic pain in the lumbar herniated disc was caused by compression on the nerve root. However, the lumbar herniated disc shows mixed pictures which are difficult to explain by simple mechanical compromise. In recent years various immunology, immunohistochemistry and molecular biology studies have shown that the herniated tissue is not an inert material, but rather it Is biologically very active with the capability of expressing a series of inflammatory mediators: cytokines such as interleukin-1, interleukin-6, interleuquin-8 and tumor necrosis factor being the ones which stand out. The inflammation is not only induced by the chemical irritation of the bioactive substances released by the nucleus pulposus but also by an autoimmune response against itself. Thus, in addition to the mechanical factor, the biomechanical mediation plays an important role in the pathophysiology of sciatic pain and of radiculopathy. Through a review of a wide range of literature, we researched the cellular molecular mediators involved in this inflammatory process around the lumbar herniated disc and its involvement in sciatic pain.

Radionuclide tumor necrosis factor-alpha activity in herniated lumbar disc correlates with severe leg pain

Background

Lumbar disc herniation is often associated with an inflammatory process. In this context, inflammation has been considered a key factor in the modulation of pain. Here, we present a case of inflammatory activity directly documented in a patient with a lumbar disc herniation.

Case Description

A 49-year-old male presented with progressive low back pain and left-sided S1 radiculopathy, without a focal neurological deficit. The lumbar MR revealed a prominent herniated disc at the L5-S1 level, with compression of the left S1 root. The patient underwent a L5-S1 discectomy using a standard interlaminar approach. Although initially he was pain free, he required three additional operations to address recurrent pain complaints. As research indicates that local inflammation contributes to neuropathic pain, we had the patient undergoes single-photon emission computed tomography (SPECT) imaging using technetium-99m-labeled-infliximab (an anti-tumor necrosis factor [TNF]-alpha monoclonal antibody) before a proposed fourth operation. The SPECT study documented a strong signal at the site of the herniated disc, thus confirming the diagnosis of a pro-inflammatory process involving the S1 nerve root. Nine months after the fourth operation, the patient was pain free. Of interest, the second SPECT study in the now asymptomatic patient demonstrated no detectable/ residual signal at the operative/disc site.

Conclusion

Absence of a SPECT TNF-alpha signal in a pain-free patient following a lumbar discectomy correlates with the reduction/resolution of the local preoperative inflammatory response.

TNFAIP8 family gene expressions in the mouse tail intervertebral disc injury model

INTRODUCTION

The TNF-α-induced protein-8 (TNFAIP8, also known as TIPE) family of molecules comprises four members: TNFAIP8 and TIPEs1-3. Since the first description of these proteins, their roles in fine-tuning inflammation and in directing leukocyte migration have been described in several organ systems. However, their relationship with intervertebral disc (IVD) is unknown.

MATERIALS AND METHODS

Here, we describe the expression of TNFAIP8 family genes in the nucleus pulposus (NP) and annulus fibrosus (AF) of the normal adult murine IVD. We further describe the expression of these genes in the injured male and female murine IVD.

RESULTS

Tnfaip8 gene expression was decreased, and Tipe1 gene expression was essentially unchanged, in response to injury. Tipe2 and Tipe3 gene expression was markedly elevated in response to IVD injury, along with those encoding known inflammatory markers (ie, Tnfa, Il6, Cxcl1, and Adam8). Additionally, sex-related differences were also observed for some of these genes in intact and injured mouse IVDs. Future studies include examining tissue distribution of TNFAIP8 family proteins and identifying cells that produce them. In addition, examining mice that are deficient in TNFAIP8 molecules, in relation to gene expression, tissue morphology and mouse behavior, may further delineate the roles of these molecules in IVD inflammation and degeneration.

The contradictory effect of macrophage-related cytokine expression in lumbar disc herniations: a systematic review

PURPOSE

Sciatic symptoms due to lumbar disc herniation are likely to be caused not solely by mechanical compression of the nerve root, but also by pain-inducing elements from inflammatory processes. Key components in the inflammatory reaction are M1 and M2 macrophages, with the M1 type being associated with pro-inflammatory processes and M2 with anti-inflammatory-processes.

METHOD

The present systematic review summarizes all studies on associations between M1 and M2 macrophages and their related inflammation factors and pain symptoms in lumbar disc herniations. Literature search was performed using an optimally sensitive search string. Studies were selected for inclusion by means of predefined inclusion and exclusion criteria and subsequently graded for risk of bias. A total of 14 studies were included. Overall risk of bias was moderate (8/14), and three studies had high risk of bias and three has low risk of bias.

RESULTS

Regarding M1-related cytokines, high levels of TNF-α, TNFR1, IL-6, IL-8, and IFN-γ were all associated high VAS scores. In contrast, high levels of TNFR2 were associated with lower VAS scores. Moreover, no associations were found for IL-1a and IL-1β. Results regarding M2-related cytokines revealed the opposite: high levels of both IL-4 and IL-10 were associated with lower VAS scores. No associations were established for TGF-β. Moreover, the presence of macrophages (CD68) was negatively associated with VAS scores.

CONCLUSION

While M1-related pro-inflammatory cytokines worsen pain symptoms, M2-related anti-inflammatory cytokines alleviate pain symptoms. Nevertheless, the present evidence is limited, and further research on the underlying pathophysiological mechanism in sciatica is required. These slides can be retrieved under Electronic Supplementary Material.

Aging of mouse intervertebral disc and association with back pain

With the increased burden of low back pain (LBP) in our globally aging population there is a need to develop preclinical models of LBP that capture clinically relevant features of physiological aging, degeneration, and disability. Here we assess the validity of using a mouse model system for age-related LBP by characterizing aging mice for features of intervertebral disc (IVD) degeneration, molecular markers of peripheral sensitization, and behavioral signs of pain. Compared to three-month-old and one-year-old mice, two-year-old mice show features typical of IVD degeneration including loss of disc height, bulging, innervation and vascularization in the caudal lumbar IVDs. Aging is also associated with the loss of whole-body bone mineral density in both male and female mice, but not associated with percent lean mass or body fat. Additionally, two-year-old mice have an accumulation of TRPA1 channels and sodium channels NaV1.8 and NaV1.9 in the L4 and L5 lumbar dorsal root ganglia consistent with changes in nociceptive signaling. Lastly, the effect of age, sex, and weight on mobility, axial stretching and radiating pain measures was assessed in male and female mice ranging from two months to two years in a general linear model. The model revealed that regardless of sex or weight, increased age was a predictor of greater reluctance to perform axial stretching and sensitivity to cold, but not heat in mice.

Hypotonicity differentially affects inflammatory marker production by nucleus pulposus tissue in simulated disc degeneration versus herniation

Inflammatory cytokines play an important role in intervertebral disc degeneration. Although largely produced by immune cells, nucleus pulposus (NP) cells can also secrete them under various conditions, for example, under free swelling. Thus, tissue hypotonicity may be an inflammatory trigger for NP cells. The aim of this study was to investigate whether decreased tonicity under restricted swelling conditions (as occurring in early disc degeneration) could initiate an inflammatory cascade that mediates further degeneration. Healthy bovine NP tissue was balanced against different PEG concentrations (0-30%) to obtain various tissue tonicities. Samples were then placed in an artificial annulus (fixed volume) and were cultured for 3, 7, or 21 days, with free swelling NP as control. Tissue content (water, glycosaminoglycan, collagen) was analyzed, and both the tissue and medium were screened for tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), prostaglandin-E₂ (PGE₂ ), and nitric oxide (NO). A range of tonicities (isotonic to hypotonic) was present at day 3 in the PEG-treated samples. However, during culture, the tonicity range narrowed as GAGs leached from the tissue. TNF-α and IL-1β were below detection limits in all conditions, while mid- and downstream inflammatory cytokines were detected. This may suggest that the extracellular environment directly affects NP cells instead of inducing a classical inflammatory cascade. Furthermore, IL-8 increased in swelling restricted samples, while IL-6 and PGE₂ were elevated in free swelling controls. These findings may suggest the involvement of different mechanisms in disc degeneration with intact AF compared to herniation, and encourage further investigation. © 2019 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res.

Inflammatory biomarkers in patients with sciatica: a systematic review

BACKGROUND

This systematic review focusses on inflammation as an underlying pathogenic mechanism in sciatica. We addressed two questions in particular: (1) what inflammatory biomarkers have been identified in patients with sciatica in the literature so far? 2) is there an association between the level of inflammatory activity and clinical symptoms?

METHODS

The search was conducted up to December 19th 2018 in MEDLINE, EMBASE, CENTRAL and Web of Science. The study selection criteria: (1) observational cohort studies, cross-sectional studies and randomized clinical trials (RCT), (2) adult population (≥ 18 years) population with sciatica, (3) concentrations of inflammatory biomarkers measured in serum, cerebrospinal fluid (CSF) or biopsies, and (4) evaluation of clinically relevant outcome measures (pain or functional status). Three reviewers independently selected studies and extracted data regarding the study characteristics and the outcomes. Risk of Bias was evaluated using an adjusted version of the Quality in Prognosis Studies (QUIPS) tool.

RESULTS

In total 16 articles fulfilled the criteria for inclusion: 7 cross sectional observational studies and 9 prospective cohort studies that included a total of 1212 patients. With regard to question 1) the following markers were identified: interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17, IL-21, tumor necrosis factor-α (TNF-α), phospholipase A2, high sensitivity C-reactive protein (hsCRP), C-X-C motif chemokine 5 (CXCM5), CX3CL1, CCL2, epidermal growth factor (EGF), and monocyte chemotactic protein 4 (MCP-4). With regard to question 2) several positive correlations were found in longitudinal studies: a strong positive correlation between inflammatory mediators or byproducts and pain (measured by visual analogue scale, VAS) was found for IL-21 in two studies (r > 0,8), and moderate positive correlations for TNF-a in both serum (r = 0,629) and biopsy (r = 0.65); severe pain (VAS > 4) is associated with increased hsCRP levels among patients with sciatica (adjusted OR = 3.4 (95% CI, 1.1 to 10).

CONCLUSION

In this systematic review there was considerable heterogeneity in the type of biomarkers and in the clinical measurements in the included studies. Taking into account the overall risk of bias of the included studies there is insufficient evidence to draw firm conclusions regarding the relationship between inflammation and clinical symptoms in patients with sciatica.

Progranulin Is Positively Associated with Intervertebral Disc Degeneration by Interaction with IL-10 and IL-17 Through TNF Pathways

Progranulin (PGRN) is a widely expressed growth factor that effectively inhibits tumor necrosis factor α (TNFα)-mediated inflammatory response. TNFα is involved in intervertebral disc degeneration (IDD) and plays a key role. This study aims to determine the role of PGRN in the intervertebral disc degeneration process. We collected intervertebral discs (IVDs) from humans and mice with different genetic backgrounds. We examined the expression of PGRN in IVD tissues by immunohistochemistry staining and Western blotting assay. We examined the peripheral serum level of PGRN by ELISA assay. Murine IVD tissue samples were taken to undergo safranin O, HE, and immunohistochemistry staining. Primary human nucleus pulposus cells were used for ELISA and RT-PCR assays. PGRN as well as interlukin-10 (IL-10) and interlukin-17 (IL-17) expressions were elevated in degenerative discs and peripheral blood sera. Loss of PGRN led to accelerated disc degeneration in the animal model, along with decreased expression of IL-10 and increased expression of IL-17. Additionally, the PGRN level was positively related to levels of IL-10 and IL-17. In vitro study suggested that PGRN protected against disc degeneration by inducing IL-10 and reducing IL-17. PGRN is associated with intervertebral disc degeneration through interfering with IL-10 and IL-17; thus, PGRN could be an interesting biomarker for diagnosis and a potential treatment target.

Transgenic mice overexpressing human TNF-α experience early onset spontaneous intervertebral disc herniation in the absence of overt degeneration

There is a well-established link between cytokine expression and the progression of intervertebral disc degeneration. Among these cytokines, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) are the most commonly studied. To investigate whether systemic hTNF-α overexpression affects intervertebral disc health, we studied the spine phenotype of Tg197 mice, a widely used hTNF-α transgenic line. These mice were studied at 12–16 weeks of age using comprehensive histochemical and immunohistological analysis of the spinal motion segment. Micro-CT analysis was performed to quantify vertebral trabecular bone architecture. The Tg197 mice evidenced spontaneous annular tears and herniation with increased vascularity in subchondral bone and significant immune cell infiltration. The full-thickness annular tear without nucleus pulposus (NP) extrusion resulted in neutrophil, macrophage, and mast cell infiltration into the disc, whereas the disc with full-thickness tear and pronounced NP herniation showed additional presence of CD4+ and CD8+ T cells. While the observed defects involved failure of the annular, endplate, and vertebral junction, there were no obvious alterations in the collagen or aggrecan content in the NP and annulus fibrosus or the maturity of collagen fibers in Tg197 mice. Despite elevated systemic inflammation and pronounced loss of trabecular bone in the vertebrae, intact Tg197 discs were healthy and showed an increase in NP cell number. The NP cells in intact discs preserved expression of phenotypic markers: CAIII, Glut1, and Krt19. In conclusion, elevated systemic TNF-α increases the susceptibility of mice to spontaneous disc herniation and possibly radiculopathy, without adversely affecting intact intervertebral disc health.

Elevated inflammatory cytokine expression in CSF from patients with symptomatic thoracic disc herniation correlates with increased pain scores

BACKGROUND

The pathophysiology of pain in patients with symptomatic thoracic disc herniation (TDH) remains poorly understood. Mere mechanical compression of the spinal cord and/or the exiting nerve root by a prolapsed disc cannot explain the pathogenesis of pain in all cases. Previous studies report a direct correlation between the levels of proinflammatory cytokines in disc biopsies and the severity of leg pain in patients with lumbar disc herniation. A similar correlation in patients with TDH has not been investigated.

PURPOSE

To correlate the cerebrospinal fluid (CSF) expression of cytokines and pain-related amino acids with preoperative pain scores in patients with symptomatic TDH.

STUDY DESIGN

A prospective human study of CSF samples and clinical outcome scores.

METHODS

Using enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC), we determined inflammatory cytokine levels (TNF-α, IL-1β, and IL-10) and amino acid levels (glutamate, aspartate, gamma-aminobutyric acid, glycine, and arginine) in CSF samples from 10 patients with TDH and 10 control subjects who did not suffer an inflammatory disease nor pain related to spinal cord compression and subsequently correlated these levels with preoperative pain scores. Differences between both groups were evaluated by a Mann-Whitney U test. In order to estimate the correlation between cytokine or amino acid expression and pain scores, data were analyzed using a linear regression analysis.

RESULTS

No inflammatory cytokines were found in CSF samples from control subjects, whereas TNF-α, IL-1β, and IL-10 were detectable by ELISA in all CSF samples from patients with TDH. TNF-α and IL-10 but not IL-1β levels moderately correlated with preoperative pain scores. Elevated TNF-αlevels positively correlated with high pain scores; elevated IL-10 levels negatively correlated with high pain scores. Amino acids were detectable in all samples from both groups. There were no significant differences between the groups in any of the amino acids measured with HPLC.

CONCLUSION

Increased proinflammatory cytokine expression is associated with elevated pain scores in patients with symptomatic TDH. On the other hand, there is no conclusive correlation between the intensity of pain and the local or systemic presence of amino acids associated with pain transmission.

Mechanical loading of intervertebral disc modulates microglia proliferation, activation, and chemotaxis

OBJECTIVE

The aim of the study is to assess the effects of the neuroinflammatory microenvironment of a mechanically-induced degenerating intervertebral disc (IVD) on neuroinflammatory like cells such as microglia, in order to comprehend the role of microglial cells in degenerative disc disease.

METHODS

Bovine caudal IVDs were kept in culture in an ex vivo bioreactor under high frequency loading and limited nutrition or in free swelling conditions as control samples. Conditioned media (CM) were collected, analysed for cytokine and neurotrophin content and applied to microglial cells for neuroinflammatory activation assessment.

RESULTS

Degenerative conditioned medium (D-CM) induced a higher production of interleukin (IL)-8, nerve growth factor (NGF), interferon (IFN)-γ, IL-17 from IVD cells than unloaded control conditioned medium (U-CM). Upon 48 h of co-incubation with microglia, D-CM stimulated microglia proliferation, activation, with increased expression of ionized calcium binding adaptor molecule 1 (IBA1) and CD68, and chemotaxis. Moreover, an increment of nitrite production was observed. Interestingly, D-CM caused an upregulation of IL-1β, IL-6, tumour necrosis factor α (TNFα), inducible NO synthase (iNOS), IBA1, and vascular endothelial growth factor (VEGF) genes in microglia. Similar results were obtained when microglia were treated with the combination of the measured cytokines.

CONCLUSIONS

Our findings show that in IVD degenerative microenvironment, IL-8, NGF, IFN-γ, IL-17 drive activation of microglia in the spinal cord and increase upregulation of neuroinflammatory markers. This, in turn, enhances the inflammatory milieu within IVD tissues and in the peridiscal space, aggravating the cascade of degenerative events. This study provides evidence for an important role of microglia in maintaining IVD neuroinflammatory microenvironment and probably inducing low back pain.

Looking beyond the intervertebral disc: the need for behavioral assays in models of discogenic pain

Orthopedic research into chronic discogenic back pain has commonly focused on aging- and degeneration-related changes in intervertebral disc structure, biomechanics, and biology. However, the primary spine-related reason for physician office visits is pain. The ambiguous nature of the human condition of discogenic low back pain motivates the use of animal models to better understand the pathophysiology. Discogenic back pain models must consider both emergent behavioral changes following pain induction and changes in the nervous system that mediate such behavior. Looking beyond the intervertebral disc, we describe the different ways to classify pain in human patients and animal models. We describe several behavioral assays that can be used in rodent models to augment disc degeneration measurements and characterize different types of pain. We review rodent models of discogenic pain that employed behavioral pain assays and highlight a need to better integrate neuroscience and orthopedic science methods to extend current understanding of the complex and multifactorial pathophysiology of discogenic back pain.

Nanoparticle fullerol alleviates radiculopathy via NLRP3 inflammasome and neuropeptides

The present study aimed to evaluate the analgesic effect of the antioxidant nanoparticle fullerol in a mouse radiculopathy and a dorsal root ganglion (DRG) culture models. Intervertebral disk degeneration causes significant hyperalgesia and nerve inflammation. Pain sensitization and inflammatory reaction were counteracted by fullerol when disk material was bathed in 10 or 100μM of fullerol prior to implantation. Immunohistochemistry showed similar massive IBA1 positive macrophage infiltration surrounding implanted disk material among groups, but IL-1β and IL-6 expression was decreased in the fullerol treated group. In the DRG explant culture, after treatment with TNF-α, the expression of IL-1β, NLRP3, and caspase 1 was significantly increased but this was reversed by the addition of fullerol. In addition, fullerol also decreased the expression of substance P and CGRP in the cultured DRGs. Nanoparticle fullerol effectively counteracts pain sensitization and the inflammatory cascade caused by disk degeneration.

Tumor necrosis factor-α: a key contributor to intervertebral disc degeneration

Intervertebral disc (IVD) degeneration (IDD) is the most common cause leading to low back pain (LBP), which is a highly prevalent, costly, and crippling condition worldwide. Current treatments for IDD are limited to treat the symptoms and do not target the pathophysiology. Tumor necrosis factor-α (TNF-α) is one of the most potent pro-inflammatory cytokines and signals through its receptors TNFR1 and TNFR2. TNF-α is highly expressed in degenerative IVD tissues, and it is deeply involved in multiple pathological processes of disc degeneration, including matrix destruction, inflammatory responses, apoptosis, autophagy, and cell proliferation. Importantly, anti-TNF-α therapy has shown promise for mitigating disc degeneration and relieving LBP. In this review, following a brief description of TNF-α signal transduction, we mainly focus on the expression pattern and roles of TNF-α in IDD, and summarize the emerging progress regarding its inhibition as a promising biological therapeutic approach to disc degeneration and associated LBP. A better understanding will help to develop novel TNF-α-centered therapeutic interventions for degenerative disc disease.

Genes associated with persistent lumbar radicular pain; a systematic review

Background

The aim of the present study was to provide an overview of the literature addressing the role of genetic factors and biomarkers predicting pain recovery in newly diagnosed lumbar radicular pain (LRP) patients.

Methods

The search was performed in Medline OVID, Embase, PsycInfo and Web of Science (2004 to 2015). Only prospective studies of patients with LRP addressing the role of genetic factors (genetic susceptibility) and pain biomarkers (proteins in serum) were included. Two independent reviewers extracted the data and assessed methodological quality.

Results

The search identified 880 citations of which 15 fulfilled the inclusion criteria. Five genetic variants; i.e., OPRM1 rs1799971 G allele, COMT rs4680 G allele, MMP1 rs1799750 2G allele, IL1α rs1800587 T allele, IL1RN rs2234677 A allele, were associated with reduced recovery of LRP. Three biomarkers; i.e., TNFα, IL6 and IFNα, were associated with persistent LRP.

Conclusion

The present results indicate that several genetic factors and biomarkers may predict slow recovery in LRP. Still, there is a need for replication of the findings. A stricter use of nomenclature is also highly necessary.

Trial registration

The review is registered PROSPERO 20^th of November 2015. Registration number is CRD42015029125.

Cytokine profile in degenerated painful intervertebral disc: variability with respect to duration of symptoms and type of disease

BACKGROUND CONTEXT

Neuroinflammation is supposed to play a crucial role in the generation of chronic pain. Numerous trials have documented the contribution of proinflammatory cytokines in the pathophysiology of pain associated with peripheral and central nociception. Local and systemic expressions of proinflammatory cytokines have been implicated as mediators of pain. Among these cytokines, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) are especially notable because of their hyperalgesic impacts after nerve damage.

PURPOSE

The aim of the present study was to evaluate and compare the tissue levels of IL-1β, IL-6, interleukin-10 (IL-10), and TNF-α in subligamentous and free fragment types of degenerated intervertebral disc in acute and chronic periods.

STUDY DESIGN

This was a cross-sectional study.

PATIENT SAMPLE

A cross-sectional study was implemented on a total of 49 patients (24 women, 25 men) with an average age of 38.2±4.9 treated surgically by means of microdiscectomy.

OUTCOME MEASURES

Of these cases, 19 had complaints for less than 6 months, whereas 30 patients had been suffering from low back pain and leg pain for more than 6 months. Thirty-eight patients have been diagnosed with subligamentous type and 11 patients had free fragment type of disc degeneration.

METHODS

The levels of IL-1β, IL-6, IL-10, and TNF-α were assessed in tissue samples prepared from nucleus pulposus tissue obtained during microdiscectomy. Results were compared in patients with acute and chronic duration of complaints, as well as subligamentous and free fragment types of intervertebral disc degeneration.

RESULTS

The levels of IL-1β (p<.001), IL-6 (p<.001), IL-10 (p<.001), and TNF-α (p<.001) were significantly higher in patients with acute duration of complaints. Similarly, free fragment type of intervertebral disc degeneration displayed remarkably higher levels of IL-1β (p=.009), IL-6 (p<.001), IL-10 (p=.024), and TNF-α (p=.017) compared with the subligamentous type.

CONCLUSIONS

Inflammatory cytokines seem to have a more apparent role in intervertebral disc degeneration especially in acute period and in free fragment type. Further trials should be performed for elucidation of pathophysiology at the molecular level and the development of more effective diagnostic and therapeutic measures.

Relationship between Neuropathic Pain and Obesity

Objectives. Overweight negatively affects musculoskeletal health; hence obesity is considered a risk factor for osteoarthritis and chronic low back pain. This was conducted to determine if obesity affects neuropathic pain, usually considered unrelated to the weight-load on the musculoskeletal system. Methods. Using a cut-off body mass index value of 25, 44 patients with neuropathic pain were grouped into a "high-BMI" group and a "normal-BMI" group. Results. The numeric rating scale of the high-BMI group was significantly higher than that of the normal-weight group (P < 0.05). The total NPSI scores were significantly higher (P < 0.01), and the paroxysmal pain and the negative symptoms were more serious in the high-BMI group than in the normal-BMI group. The high-BMI subjects also had significantly higher SF-MPQ scores (P < 0.05). However, both physical and mental health status on the SF-36 were comparable between the groups. Discussion. Neuropathic pain that did not arise from musculoskeletal damage was higher in the high-BMI patients. Paroxysmal pain was more severe, suggesting that neural damage might be aggravated by obesity-associated inflammation. These findings should have needed to be confirmed in future studies.

IL-17 mediates inflammatory reactions via p38/c-Fos and JNK/c-Jun activation in an AP-1-dependent manner in human nucleus pulposus cells

BACKGROUND

Low back pain and sciatica caused by intervertebral disc (IVD) disease are associated with inflammatory responses. The cytokine interleukin 17 (IL-17) is elevated in herniated and degenerated IVD tissues and acts as a regulator of disc inflammation. The objective of this study was to investigate the involvement of IL-17A in IVD inflammatory response and to explore the mechanisms underlying this response.

METHODS

Cells were isolated from nucleus pulposus (NP) tissues collected from patients undergoing surgeries for IVD degeneration. The concentrations of COX2 and PGE2, as well as of select proteins involved in the mitogen-activated protein kinase (MAPK)/activating protein-1 (AP-1) pathway, were quantified in NP cells after exposure to IL-17 with or without pretreatment with MAPK or AP-1 inhibitors.

RESULTS

Our results showed that IL-17A increased COX2 expression and PGE2 production via the activation of MAPKs, including p38 kinase and Jun N-terminal kinase (JNK). Moreover, IL-17A-induced COX2 and PGE2 production was shown to rely on p38/c-Fos and JNK/c-Jun activation in an AP-1-dependent manner.

CONCLUSION

In summary, our results indicate that IL-17A enhances COX2 expression and PGE2 production via the p38/c-Fos and JNK/c-Jun signalling pathways in NP cells to mediate IVD inflammation.

Elevated levels of tumor necrosis factor-α and TNFR1 in recurrent herniated lumbar discs correlate with chronicity of postoperative sciatic pain

BACKGROUND CONTEXT

Sciatica is a condition characterized by radicular pain that can be secondary to a lumbar disc herniation (LDH). More than 10% of patients report persistent pain after surgery. The underlying mechanisms of postoperative sciatica remain unclear. There is evidence demonstrating that inflammation plays a role in the pathophysiology of sciatica.

PURPOSE

The study aimed to assess if the expression of tumor necrosis factor (TNF)-α and its receptors (TNFR) was correlated with the severity of pre- and postoperative leg pain in LDH patients who underwent single or multiple decompressive discectomies.

SETTING

This is an experimental prospective human study of intraoperative intervertebral disc (IVD) samples, as well as a clinical scores evaluation.

METHODS

We analyzed the mRNA and protein levels of TNF-α, TNFR1, and TNFR2 in IVD biopsies, and correlated them with visual analogue scale (VAS) scores 1 day before surgery to 6 weeks and 6 months postoperatively.

RESULTS

We evaluated the correlation between the inflammation in IVD with pre- and postoperative pain scores after discectomy in LDH patients operated for the first time (fLDH, N=12) and for recurrent cases (rLDH, N=8). This analysis showed that TNF-α and TNFR1 mRNA levels were significantly greater in rLDH patients; there was a twofold increase for TNF-α and a 50% increase for TNFR1. Similarly, protein levels in IVD samples positively correlated with postoperative VAS scores, whereas TNFR2 protein levels negatively correlated with postoperative VAS scores.

CONCLUSIONS

These findings indicate that rLDH patients present higher postoperative VAS scores compared with fLDH patients, and also that these scores are correlated with increased inflammation and may contribute to pain chronicity.

Reduced tonicity stimulates an inflammatory response in nucleus pulposus tissue that can be limited by a COX-2-specific inhibitor

In intervertebral disc herniation with nucleus pulposus (NP) extrusion, the elicited inflammatory response is considered a key pain mechanism. However, inflammatory cytokines are reported in extruded herniated tissue, even before monocyte infiltration, suggesting that the tissue itself initiates the inflammation. Since herniated tissue swells, we investigated whether this simple mechanobiological stimulus alone could provoke an inflammatory response that could cause pain. Furthermore, we investigated whether sustained-release cyclooxygenase-2 (COX2) inhibitor would be beneficial in such conditions. Healthy bovine NP explants were allowed to swell freely or confined. The swelling explants were treated with Celecoxib, applied either as a bolus or in sustained-release. Swelling explants produced elevated levels of interleukin-6 (IL-6) and prostaglandin E2 (PGE2 ) for 28 days, while confined explants did not. Both a high concentration bolus and 10 times lower concentration in sustained release completely inhibited PGE2 production, but did not affect IL-6 production. Swelling of NP tissue, without the inflammatory system response, can trigger cytokine production and Celecoxib, even in bolus form, may be useful for pain control in extruded disc herniation.

Sciatica: detection and confirmation by new method

We need to overcome limitations of present assessment and also integrate newer research in our work about sciatica. Inflammation induces changes in the DRG and nerve root. It sensitizes the axons. Nociceptor is a unique axon. It is pseudo unipolar: both its ends, central and peripheral, behave in similar fashion. The nerve in periphery which carries these axons may selectively become sensitive to mechanical pressure--"mechanosensitized," as we coin the phrase. Many pain questionnaires are used and are effective in identifying neuropathic pain solely on basis of descriptors but they do not directly physically correlate nerve root and pain. A thorough neurological evaluation is always needed. Physical examination is not direct pain assessment but testing mobility of nerve root and its effect on pain generation. There is a dogmatic dominance of dermatomes in assessment of leg pain. They are unreliable. Images may not correlate with symptoms and pathology in about 28% of cases. Electrophysiology may be normal in purely inflamed nerve root. Palpation may help in such inflammatory setting to refine our assessment further. Confirmation of sciatica is done by selective nerve root block (SNRB) today but it is fraught with several complications and needs elaborate inpatient and operating room set up. We have used the unique property of the pseudo unipolar axon that both its ends have similar functional properties and so inject along its peripheral end sodium channel blockers to block the basic cause of the mechanosensitization namely upregulated sodium channels in the root or DRG. Thus using palpation we may be able to detect symptomatic nerve in stage of inflammation and with distal end injection, along same inflamed nerve we may be able to abolish and so confirm sciatica. Discussions of sciatica pain diagnosis tend to immediately shift and centre on the affected disc rather than the nerve. Theoretically it may be possible to detect the affected nerve by palpating the nerve and relieve pain moment we desensitize the nerve.

Clinical significance of tumor necrosis factor-α inhibitors in the treatment of sciatica: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Currently, no satisfactory treatment is available for sciatica caused by herniated discs and/or spinal stenosis. The objective of this study is to assess the value of tumor necrosis factor (TNF)-α inhibitors in the treatment of sciatica.

METHODS

Without language restrictions, we searched PubMed, OVID, EMBASE, the Web of Science, the Clinical Trials Registers, the Cochrane Central Register of Controlled Trials and the China Academic Library and Information System. We then performed a systematic review and meta-analysis on the enrolled trials that met the inclusion criteria.

RESULTS

Nine prospective randomized controlled trials (RCTs) and two before-after controlled trials involving 531 patients met our inclusion criteria and were included in this study. Our systematic assessment and meta-analysis demonstrated that in terms of the natural course of the disease, compared with the control condition, TNF-α inhibitors neither significantly relieved lower back and leg pain (both p > 0.05) nor enhanced the proportion of patients who felt overall satisfaction (global perceived effect (satisfaction)) or were able to return to work (return to work) (combined endpoint; p > 0.05) at the short-term, medium-term and long-term follow-ups. In addition, compared with the control condition, TNF-α inhibitors could reduce the risk ratio (RR) of discectomy or radicular block (combined endpoint; RR = 0.51, 95% CI 0.26 to 1.00, p = 0.049) at medium-term follow-up, but did not decrease RR at the short-term (RR = 0.64, 95% CI 0.17 to 2.40, p = 0.508) and long-term follow-ups (RR = 0.64, 95% CI 0.40 to 1.03, p = 0.065).

CONCLUSION

The currently available evidence demonstrated that other than reducing the RR of discectomy or radicular block (combined endpoint) at medium-term follow-up, TNF-α inhibitors showed limited clinical value in the treatment of sciatica caused by herniated discs and/or spinal stenosis.

Th17 cell frequency and IL-17 concentration correlate with pre- and postoperative pain sensation in patients with intervertebral disk degeneration

Numerous studies have revealed the presence of T helper 17 (Th17) cells in pathologic intervertebral disk (IVD) tissues and the contribution of Th17-associated cytokines to the development of this disease. However, the pre- and postoperative changes in the proportion of Th17 cells and the concentration of IL-17 in the peripheral blood of patients with IVD degeneration are not clear. The levels of Th17 frequency and the interleukin-17 (IL-17) concentration in peripheral blood from patients and volunteers were examined by flow cytometry and by enzyme-linked immunosorbent assay (ELISA), respectively. The clinical results were evaluated using the visual analogue scale (VAS). These results were subjected to a correlation analysis. Compared with the normal controls, the proportion of Th17 cells and the concentration of IL-17 were significantly increased preoperatively in patients with IVD degeneration. Postoperatively, the levels of Th17 cells and the expression of IL-17 were dramatically decreased. The correlation analysis of the VAS pain scores, Th17 cell frequency, and IL-17 concentration, including the pre- and postoperative levels and the changes induced by the surgery, revealed a positive correlation. The authors' results explain the contribution of Th17 cells and IL-17 to the pain sensation experienced by patients with IVD degeneration. These 2 factors may be good indicators for the evaluation of the surgical outcome of patients with lumbar disk herniation.

Tumor necrosis factor-α inhibitors alleviation of experimentally induced neuropathic pain is associated with modulation of TNF receptor expression

Inflammation plays a key role in the development of sensitization after peripheral nerve damage. We recently demonstrated that tumor necrosis factor-α receptor (TNFR) levels in the spinal cord correlate with pain sensation in herniated disc patients in a rat chronic constriction injury (CCI) model. By using the sciatic nerve CCI model, we studied the effect of anti-TNF-α treatment on recovery from hypersensitivity and TNFR expression in the dorsal root ganglion (DRG) and dorsal horn (DH). Experimental groups consisted of sham-operated and CCI-operated rats that received two s.c. injections (one immediately after surgery, the other 5 days later), both containing saline, etanercept (3 mg/kg body weight), or infliximab (10 mg/kg body weight). Mechanical allodynia (with von Frey filaments) and thermal hyperalgesia (Hargreaves test) were assessed preoperatively and weekly during the first 4 postoperative weeks. DRG and DH samples were collected 2 and 4 weeks after surgery and analyzed for TNFR1 and TNFR2 protein levels by Western blotting and analyzed for mRNA levels by quantitative real-time polymerase chain reaction. Anti-TNF-α treatment resulted in a significant alleviation of pain. TNFR levels were increased five- to sixfold in CCI rats compared with sham controls. Both treatments significantly diminished these increased levels. Treated animals that showed a ≥50% alleviation of pain exhibited a significantly reduced TNF R1/R2 mRNA ratio compared with treated animals that recovered less well. These results demonstrate that attenuation of TNFR expression is associated with recovery from nerve injury and suggest that this may be one of the working mechanisms of anti-TNF therapies.

Can proinflammatory cytokine gene expression explain multifidus muscle fiber changes after an intervertebral disc lesion?

STUDY DESIGN

Longitudinal case-controlled animal study.

OBJECTIVE

To investigate the effect of an intervertebral disc (IVD) lesion on the proportion of slow, fast, and intermediate muscle fiber types in the multifidus muscle in sheep, and whether muscle fiber changes were paralleled by local gene expression of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1-β.

SUMMARY OF BACKGROUND DATA

Structure and behavior of the multifidus muscle change in acute and chronic back pain, but the mechanisms are surprisingly poorly understood and the link between structure and behavior is tenuous. Although changes in muscle fiber types have the potential to unify the observations, the effect of injury on muscle fiber distribution has not been adequately tested, and understanding of possible mechanisms is limited.

METHODS

The L1-L2, L3-L4, and L5-L6 IVDs of 11 castrated male sheep received anterolateral lesions. Six control sheep underwent no surgical procedures. Multifidus muscle tissue was harvested at L4 for muscle fiber analysis using immunohistochemistry and L2 for cytokine analysis with polymerase chain reaction for local gene expression of TNF-α and interleukin-1β.

RESULTS

The proportion of slow muscle fibers in multifidus was significantly less in the lesioned animals both ipsilateral and contralateral to the IVD lesion. The greatest reduction in slow fibers was in the deep medial muscle region. A greater prevalence of intermediate fibers on the uninjured side implies a delayed fiber-type transformation on that side. TNF-α gene expression in multifidus was greater on both sides in the lesion animals than in the muscle of control animals. Interleukin-1β was increased only on the injured side.

CONCLUSION

These data provide evidence of muscle fiber changes after induction of an IVD lesion and a parallel increase in TNF-α expression. Proinflammatory cytokine changes provide a novel mechanism to explain behavioral and structural changes in multifidus.

LEVEL OF EVIDENCE

N/A.

Influence of low back pain and prognostic value of MRI in sciatica patients in relation to back pain

BACKGROUND

Patients with sciatica frequently complain about associated back pain. It is not known whether there are prognostic relevant differences in Magnetic Resonance Imaging (MRI) findings between sciatica patients with and without disabling back pain.

METHODS

The study population contained patients with sciatica who underwent a baseline MRI to assess eligibility for a randomized trial designed to compare the efficacy of early surgery with prolonged conservative care for sciatica. Two neuroradiologists and one neurosurgeon independently evaluated all MR images. The MRI readers were blinded to symptom status. The MRI findings were compared between sciatica patients with and without disabling back pain. The presence of disabling back pain at baseline was correlated with perceived recovery at one year.

RESULTS

Of 379 included sciatica patients, 158 (42%) had disabling back pain. Of the patients with both sciatica and disabling back pain 68% did reveal a herniated disc with nerve root compression on MRI, compared to 88% of patients with predominantly sciatica (P<0.001). The existence of disabling back pain in sciatica at baseline was negatively associated with perceived recovery at one year (Odds ratio [OR] 0.32, 95% Confidence Interval 0.18-0.56, P<0.001). Sciatica patients with disabling back pain in absence of nerve root compression on MRI at baseline reported less perceived recovery at one year compared to those with predominantly sciatica and nerve root compression on MRI (50% vs 91%, P<0.001).

CONCLUSION

Sciatica patients with disabling low back pain reported an unfavorable outcome at one-year follow-up compared to those with predominantly sciatica. If additionally a clear herniated disc with nerve root compression on MRI was absent, the results were even worse.

Role of cytokines in intervertebral disc degeneration: pain and disc content

Degeneration of the intervertebral discs (IVDs) is a major contributor to back, neck and radicular pain. IVD degeneration is characterized by increases in levels of the proinflammatory cytokines TNF, IL-1α, IL-1β, IL-6 and IL-17 secreted by the IVD cells; these cytokines promote extracellular matrix degradation, chemokine production and changes in IVD cell phenotype. The resulting imbalance in catabolic and anabolic responses leads to the degeneration of IVD tissues, as well as disc herniation and radicular pain. The release of chemokines from degenerating discs promotes the infiltration and activation of immune cells, further amplifying the inflammatory cascade. Leukocyte migration into the IVD is accompanied by the appearance of microvasculature tissue and nerve fibres. Furthermore, neurogenic factors, generated by both disc and immune cells, induce expression of pain-associated cation channels in the dorsal root ganglion. Depolarization of these ion channels is likely to promote discogenic and radicular pain, and reinforce the cytokine-mediated degenerative cascade. Taken together, an enhanced understanding of the contribution of cytokines and immune cells to these catabolic, angiogenic and nociceptive processes could provide new targets for the treatment of symptomatic disc disease. In this Review, the role of key inflammatory cytokines during each of the individual phases of degenerative disc disease, as well as the outcomes of major clinical studies aimed at blocking cytokine function, are discussed.

Molecular targeting of NOX4 for neuropathic pain after traumatic injury of the spinal cord

Neuropathic pain is a well-known type of chronic pain caused by damage to the nervous system. Until recently, many researchers have primarily focused on identifying cellular or chemical sources of neuropathic pain or have approached neuropathic pain via the basis of biological study. We investigated whether both mmu-mir-23b (miR23b) and NADPH oxidase 4 (NOX4) antibody infusion can alleviate neuropathic pain by compensating for abnormally downregulated miR23b via reducing the expression of its target gene, NOX4, a reactive oxygen species (ROS) family member overexpressed in neuropathic pain. Ectopic miR23b expression effectively downregulated NOX4 and finally normalized glutamic acid decarboxylase 65/67 expression. Moreover, animals with neuropathic pain showed significantly improved paw withdrawal thresholds (PWTs) following miR23b infusion. Normalizing miR23b expression in tissue lesions, caused by neuropathic pain induction, reduced inflammatory mediators and increased several ROS scavengers. Moreover, γ-aminobutyric acid (GABA)ergic neurons coexpressed suboptimal levels of miR23b and elevated NOX4/ROS after pain induction at the cellular level. MiR23b finally protects GABAergic neurons against ROS/p38/c-Jun N-terminal kinase (JNK)-mediated apoptotic death. By evaluating the functional behavior of mice receiving pain/miR23b, normal/anti-miR23b, anti-miR23b/si-NOX4, pain/NOX4 antibody, pain/ascorbic acid, and pain/ascorbic acid/NOX4 antibody, the positive role of miR23b and the negative role of NOX4 in neuropathic pain were confirmed. Based on this study, we conclude that miR23b has a crucial role in the amelioration of neuropathic pain in injured spinal cord by inactivating its target gene, NOX4, and protection of GABAergic neurons from cell death. We finally suggest that infusion of miR23b and NOX4 antibody may provide attractive diagnostic and therapeutic resources for effective pain modulation in neuropathic pain.