Cytokine inhibition and time-related influence of inflammatory stimuli on the hyperalgesia induced by the nucleus pulposus

Effect of local epidural application of methylprednisolone acetate on time to ambulation in non-ambulatory dogs with thoracolumbar intervertebral disc disease: A prospective randomised, blinded control trial

BACKGROUND

The objective of this study was to analyse the potential benefit of the epidural application of steroids on time to ambulation in non-ambulatory dogs affected by intervertebral disc disease (IVDD) treated with decompressive surgery.

METHODS

This prospective, randomised, blinded control trial involved 41 dogs with thoracolumbar disc extrusion, which were randomly allocated into two groups. In the control group, saline was locally applied after surgical decompression of the spinal cord (n = 23). In the treatment group (n = 18), local epidural application of methylprednisolone acetate (1 mg/kg) was used. Ambulation time was the primary outcome measure, defined as the ability to take 10 independent steps.

RESULTS

The median number of days to ambulation was 7 days (range: 1‒17 days) for the control group and 3 days (range: 1‒8 days) for the treatment group. One dog from the treatment group developed discospondylitis and abscess formation.

LIMITATIONS

The study's heterogeneity in dog breeds, ages and pre-existing health conditions could affect the generalisability of the findings.

CONCLUSION

Epidural methylprednisolone acetate applied locally at the time of surgery may accelerate recovery in dogs following IVDD surgery.

Evaluation of the effect of phellodendrin application on rats creating an experimental model of non-compression lumbar disc herniation on the NF-κB-related inflammatory signaling pathway

OBJECTIVE

To explore the therapeutic effects of phellodendrine on non-compression lumbar disc herniation (NCLDH).

METHODS

The Sprague Dawley rat model of NCLDH was established via autologous caudal nucleus pulposus transplantation. Behavioral observations and neurological function scoring were conducted in Sprague Dawley rats, and the serum levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured via enzyme-linked immunosorbent assay (ELISA). Real-time quantitative polymerase chain reaction (RT‒qPCR) was used to detect the expression of nuclear factor kappa-B (NF-κB) p65 mRNA in L5 nerve roots and surrounding tissues. Western blotting was used to assess the protein expression of NF-κB p65 and TNF-α. Immunofluorescence and immunohistochemical analyses were performed to investigate the distribution and expression of the NF-κB p65 protein in the L5 nerve and its surrounding tissues.

RESULTS

In this animal study, phellodendrine was found to downregulate the expression of p65 mRNA, decrease the release of inflammatory factors, and alleviate motor dysfunction caused by lumbar disc herniation(LDH). Therefore, the phellodendrine technique has potential value for the treatment of NCLDH.

CONCLUSION

In this animal experiment, phellodendrine was found to significantly reduce the expression level of p65 mRNA, decrease the release of inflammatory cytokines, and alleviate lumbar disc pain.

CLINICAL TRIAL NUMBER

Not applicable.

Evidence from Mendelian randomization analysis combined with meta-analysis for the causal validation of the relationship between 91 inflammatory factors and lumbar disc herniation

Lumbar disc herniation (LDH) is a common spinal disease. In recent years, an increasing number of observational studies have reported the impact of inflammatory factors on LDH. By conducting Mendelian randomization (MR) analysis on 91 inflammatory factors, it is possible to reveal their causal relationship with LDH, providing new insights for prevention and treatment strategies. In this study, a two-sample MR analysis was performed, using 91 inflammatory factors as exposure data, and LDH data from 2 different sources as outcome data. Subsequently, the most significant results from the inverse-variance weighted analysis were subjected to meta-analysis, with multiple corrections applied to the thresholds to ensure result accuracy. Finally, reverse causality MR analysis was conducted to validate the causal relationship between the identified positive inflammatory factors and LDH. Ninety-one cytokines were analyzed in relation to LDH using MR with data from the Finngen and UK Biobank databases. The inverse-variance weighted results from both analyses were then meta-analyzed, and multiple corrections were applied to the significance threshold of the meta-analysis results. Ultimately, only 1 cytokine, tumor necrosis factor-beta levels (genome-wide association study ID: GCST90274840), showed a significant association after the combined MR analysis and multiple corrections, with an odds ratio of 1.073 (95% confidence interval: 1.034-1.113, P = .0154). Furthermore, this positive cytokine did not display any reverse causality with LDH from either data source. Tumor necrosis factor-beta levels are a risk factor for LDH, potentially increasing the risk of developing the condition and exacerbating its symptoms.

Long-term changes of Th17 and regulatory T cells in peripheral blood of dogs with spinal cord injury after intervertebral disc herniation

BACKGROUND

Intervertebral disc herniation (IVDH) is one of the most common causes of spinal cord injury (SCI) in dogs. As a result of acute SCI, a complex inflammatory response occurs in the spinal cord. Th17 cells (Th17) produce pro-inflammatory cytokines, while regulatory T cells (Treg) have opposite effects producing anti-inflammatory cytokines. Therefore, the aim of this study was to determine whether Th17- and Treg cells are involved in the pathogenesis of SCI or whether cellular changes occur due to coexisting inflammatory diseases. We hypothesized that chronic alterations in the Th17/Treg ratio are associated with a worse outcome after SCI.

METHODS

Twenty-six paretic or plegic dogs with IVDH with and without coexisting inflammatory disease were investigated in the acute stage of the disease and after recovery of SCI. In addition, a healthy control group was included (n = 14). Quantification of Th17 and Treg cells, from peripheral blood samples, was performed by multicolor flow cytometry and IL17 was measured using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

After recovery significantly higher levels of Th17 (p = 0.0265) and Treg cells (p = 0.00025) were detected compared to acute IVDH but Th17/Treg ratio did not differ significantly. Recovered dogs and the control group did not differ significantly from each other. No association between an imbalance in the ratio and neurologic severity or underlying inflammatory diseases was found.

CONCLUSION

This study demonstrated that altered Th17 and Treg levels in peripheral blood are altered in the acute stage of IVDH, preexisting inflammatory diseases seem not to influence these cell populations. Th17 and Treg cells could be considered when evaluating new treatment strategies for SCI.

Clinical Effectiveness of Single Lumbar Periradicular Infiltration in Patients with Sciatica

Periradicular therapy (PRT) is a minimally invasive radiological procedurein patients with chronic lumbar pain.The aim of the study is to identify clinical and radiological predictive factors for treatment success after a single PRT treatment in patients with sciatica.The study includes a prospective follow-up of 166 patients treated with PRT. The pain intensity is determined according to the VAS scale and the degree of improvement is presented as excellent (over 75%), good (50-70%), moderate (25-49%), and weak (less than 25%). The follow up of the treated patients was done at 2 weeks, 3 and 6 months. In patients with pain duration up to 3 months, the improvement was excellent in n=32 (58.18%) after 2 weeks, after 3 months n=41 (74.55%) and after 6 months n=41 (74.55%). This stands in contrast to patients with pain over 1 year. The percentage of improvement after 6 months, post-intervention, was highest in patients without nerve root compression (86.25±19.2),and the highest improvement after 6 months was in patients with localization of pain at the L4-L5 level (69.69±29.7), the greatest improvement after six months was in patients with extraforaminal hernia (62.82±34.3), and the lowest in patients with central stenosis (40.21±30.7).Our study results suggest that the shorter a pain duration, low-grade root compression, injection level and type of herniation area predictor the more favourable response patients have to transforaminal epidural steroid injection in patients with sciatica.

Monomeric CRP regulates inflammatory responses in human intervertebral disc cells

CRP is an acute-phase protein that is used as a biomarker to follow severity and progression in infectious and inflammatory diseases. Its pathophysiological mechanisms of action are still poorly defined. CRP in its pentameric form exhibits weak anti-inflammatory activity. The monomeric isoform (mCRP) exerts potent proinflammatory properties in chondrocytes, endothelial cells, and leucocytes. No data exist regarding mCRP effects in human intervertebral disc (IVD) cells. This work aimed to verify the pathophysiological relevance of mCRP in the aetiology and/or progression of IVD degeneration. We investigated the effects of mCRP and the signalling pathways that are involved in cultured human primary annulus fibrosus (AF) cells and in the human nucleus pulposus (NP) immortalized cell line HNPSV-1. We determined messenger RNA (mRNA) and protein levels of relevant factors involved in inflammatory responses, by quantitative real-time polymerase chain reaction (RT-qPCR) and western blot. We also studied the presence of mCRP in human AF and NP tissues by immunohistochemistry. We demonstrated that mCRP increases nitric oxide synthase 2 (NOS2), cyclooxygenase 2 (COX2), matrix metalloproteinase 13 (MMP13), vascular cell adhesion molecule 1 (VCAM1), interleukin (IL)-6, IL-8, and Lipocalin 2 (LCN2) expression in human AF and NP cells. We also showed that nuclear factor-κβ (NF-κβ), extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphoinositide 3-kinase (PI3K) are at play in the intracellular signalling of mCRP. Finally, we demonstrated the presence of mCRP in human AF and NP tissues. Our results indicate, for the first time, that mCRP can be localized in IVD tissues, where it triggers a proinflammatory and catabolic state in degenerative and healthy IVD cells, and that NF-κβ signalling may be implicated in the mediation of this mCRP-induced state.

Heterogeneous macrophages contribute to the pathology of disc herniation induced radiculopathy

BACKGROUND CONTEXT

Macrophages play important roles in the progression of intervertebral disc herniation and radiculopathy.

PURPOSE

To better understand the roles of macrophages in this process, we developed a new mouse model that mimics human radiculopathy.

STUDY DESIGN/SETTING

A preclinical randomized animal study.

METHODS

Three types of surgeries were performed in randomly assigned Balb/c mice. These were spinal nerve exposure, traditional anterior disc puncture, and lateral disc puncture with nerve exposure (n=16/group). For the nerve exposure group, the left L5 spinal nerve was exposed without disc injury. For the traditional anterior puncture, L5/6 disc was punctured by an anterior approach as previously established. For lateral puncture with nerve exposure, the left L5 spinal nerve was exposed by removing the psoas major muscle fibers, and the L5/6 disc was punctured laterally on the left side with a 30G needle, allowing the nucleus to protrude toward the L5 spinal nerve. Mechanical hyperalgesia (pain sensitivity) of hind paws was assessed with electronic von Frey assay on alternative day for up to 2 weeks. MRI, histology, and immunostaining were performed to confirm disc herniation and inflammation.

RESULTS

Ipsilateral pain in the lateral puncture with nerve exposure group was significantly greater than the other groups. Pro-inflammatory cytokines IL-1β and IL-6 were markedly elevated at the hernia sites of both puncture groups and the spinal nerve of lateral puncture with never exposure group on postoperative day 7. Heterogeneous populations of macrophages were detected in the infiltration tissue of this mouse model and in tissue from patients undergone discectomy.

CONCLUSIONS

We have established a new mouse model that mimics human radiculopathy and demonstrated that a mixed phenotype of macrophages contribute to the pathogenesis of acute discogenic radiculopathy.

CLINICAL SIGNIFICANCE

This study provides a clinically relevant in vivo animal model to elucidate complex interactions of disc herniation and radicular pain, which may present opportunities for the development of macrophage-anchored therapeutics to manage radiculopathy.

TNFAIP3 alleviates pain in lumbar disc herniation rats by inhibiting the NF-κB pathway

Background

It’s been reported that the tumor necrosis factor alpha inducible protein 3 (TNFAIP3) gene played an important role in the pathogenesis of autoimmune and chronic inflammation diseases. Moreover, in degenerative diseases of the lumbar spine the nuclear factor-κB (NF-κB) pathway is significantly activated. This study aimed to explore the role of the tumor necrosis protein-induced zinc finger protein A20 (A20) protein in degenerative diseases of the lumbar spine on the NF-κBp65 pathway.

Methods

A total of 96 rats were randomly divided into 4 groups. Lumbar disc herniation (DH) was set as a sham operation group (Sham group), DH + A20 group and DH + control group (Control group); measured changes in rat paw withdrawal threshold (PWT) and paw withdrawal latency (PWL); detected the proportion of apoptotic cells in a single nucleus pulposus cell suspension, analyzed the correlation between tumor necrosis factor-α (TNF-α) content and pain in DH rats, and the expression changes of NF-κB pathway in nucleus pulposus tissue.

Results

compared with the DH + Control group, the PWT and PWL of the DH + A20 group increased significantly (P<0.05); apoptosis in the DH + A20 group was significantly reduced (P<0.01); the nucleus pulposus tissue and serum levels of TNF-α and interleukin-6 (IL-6) in the DH + A20 rat group were significantly lower than those in the DH + Control group (P<0.05); the protein expression of rats in the DH + A20 group (p-p65) was significantly lower than that in the DH + Control group (P<0.05).

Conclusions

The pain of lumbar disc herniation rats is related to TNF-α, and overexpression of A20 protein can reduce the pain of lumbar disc herniation by inhibiting the NF-κB pathway.

Keywords

Lumbar disc herniation (lumbar DH); tumor necrosis factor-α (TNF-α); interleukin-6 (IL-6); tumor necrosis factor alpha inducible protein 3 (TNFAIP3)

Trifluoro-icaritin alleviates mechanical hypersensitivity and improves motor coordination and balance in rats with spared nerve injury-induced neuropathic pain

Neuropathic pain is still one of the unsolved public health problems worldwide. Although the current reagents can attenuate neuropathic pain to a certain extent, their clinical application is very limited owing to larger toxicity and serious side effects. Trifluoro-icaritin (ICTF) has been documented to possess profound anti-inflammatory and neuroprotective activities, but whether ICTF exerts an anti-nociceptive effect on neuropathic pain remains unknown. Here, a rat model of spared nerve injury (SNI)-induced neuropathic pain was used. SNI rats were administrated with ICTF (i.p.) once daily lasting for 21 days, and subsequently the pain-related behaviors were evaluated by applying mechanical or thermal pain threshold, CatWalk gait parameter, and rotarod test on day 1 before and day 1, 3, 7, 10, 14, and 21 after SNI surgery, respectively. The results showed that ICTF (0.5 mg/kg, 1.5 mg/kg, and 5.0 mg/kg, i.p.) treatment alleviated SNI-induced mechanical allodynia but not thermal hyperalgesia in a dose-dependent manner. After administration of ICTF at the most effective dose of 5.0 mg/kg to SNI rats, CatWalk gait analysis revealed that ICTF not only significantly enhanced gait parameters including max contact max intensity, max intensity, print area, and stand time but also decreased the swing time; Rotarod test further exhibited that ICTF could effectively prolong the time on rod and increase the rotating speed in SNI rats. Additionally, following ICTF (5.0 mg/kg) treatment of SNI rats for 21 consecutive days, the max contact max intensity was found to be positively correlated with the rotating speed. Taken together, ICTF successfully ameliorates mechanical hypersensitivity and improves the motor coordination and balance in SNI rats, suggesting that ICTF may be exploited as a potential candidate in the management of neuropathic pain.

Effects of external low intensity focused ultrasound on inflammatory markers in neuropathic pain

BACKGROUND

Changes in inflammatory cytokine levels contribute to the induction and maintenance of neuropathic pain. We have shown that external low intensity focused ultrasound (liFUS) reduces allodynia in a common peroneal nerve injury (CPNI). Here, we investigate an underlying mechanism of action for this treatment and measure the effect of liFUS on inflammatory markers.

METHODS

Male rats were divided into four groups: CPNI/liFUS, CPNI/shamliFUS, shamCPNI/liFUS, and shamCPNI/shamliFUS. Mechanical nociceptive thresholds were measured using Von Frey filaments (VFF) to confirm the absence/presence of allodynia at baseline, after CPNI, and after liFUS. Commercial microarray and ELISA assays were used to assess cytokine expression in the treated L5 dorsal root ganglion (DRG) and dorsal horn (DH) tissue 24 and 72 h after liFUS.

RESULTS

VFF thresholds were significantly reduced following CPNI in both groups that received the injury (p < 0.001). After liFUS, only the CPNI/liFUS cohort showed a significant increase in mechanical thresholds (p < 0.001). CPNI significantly increased TNFa, IL6, CNTF, IL1b (p < 0.05 for all) levels in the DRG and DH, compared to baseline, consistent with previous work in sciatic nerve injury. LiFUS in CPNI rats resulted in a decrease in these cytokines in DRG 72 h post-therapy (TNFa, IL6, CNTF and IL1b, p < 0.001). In the DH, IL1b, CNTF, and TNFa (p < 0.05 for all) decreased 72 h after liFUS.

CONCLUSION

We have demonstrated that liFUS modifies inflammatory cytokines in both DRG and DH in CPNI rats. These data provide evidence that liFUS, reverses the allodynic phenotype, in part, by altering inflammatory cytokine pathways.

The Wnt/β-Catenin Pathway Regulated Cytokines for Pathological Neuropathic Pain in Chronic Compression of Dorsal Root Ganglion Model

Neuropathic pain is one of the important challenges in the clinic. Although a lot of research has been done on neuropathic pain (NP), the molecular mechanism is still elusive. We aimed to investigate whether the Wnt/β-catenin pathway was involved in NP caused by sustaining dorsal root ganglion (DRG) compression with the chronic compression of dorsal root ganglion model (CCD). Our RNA sequencing results showed that several genes related to the Wnt pathway have changed in DRG and spinal cord dorsal horn (SCDH) after CCD surgery. Therefore, we detected the activation of the Wnt/β-catenin pathway in DRG and SCDH and found active β-catenin significantly upregulated in DRG and SCDH 1 day after CCD surgery and peaked on days 7-14. Immunofluorescence results also confirmed nuclear translocalization of active β-catenin in DRG and SCDH. Additionally, rats had obvious mechanical induced pain after CCD surgery and the pain was significantly alleviated after the application of the Wnt/β-catenin pathway inhibitor XAV939. Furthermore, we found that the levels of proinflammatory factors tumor necrosis factor-α (TNF-α) and interleukin-18 (IL-18) were significantly elevated in CCD rat serum, while the levels of them were correspondingly decreased after the Wnt/β-catenin pathway being inhibited. The results of Spearman correlation coefficient analysis showed that the levels of TNF-α and IL-18 were negatively correlated with the mechanical withdrawal thresholds (MWT) after CCD surgery. Collectively, our findings suggest that the Wnt/β-catenin pathway plays a critical role in the pathogenesis of NP and may be an effective target for the treatment of NP.

Growing a backbone - functional biomaterials and structures for intervertebral disc (IVD) repair and regeneration: challenges, innovations, and future directions

Back pain and associated maladies can account for an immense amount of healthcare cost and loss of productivity in the workplace. In particular, spine related injuries in the US affect upwards of 5.7 million people each year. The degenerative disc disease treatment almost always arises due to a clinical presentation of pain and/or discomfort. Preferred conservative treatment modalities include the use of non-steroidal anti-inflammatory medications, physical therapy, massage, acupuncture, chiropractic work, and dietary supplements like glucosamine and chondroitin. Artificial disc replacement, also known as total disc replacement, is a treatment alternative to spinal fusion. The goal of artificial disc prostheses is to replicate the normal biomechanics of the spine segment, thereby preventing further damage to neighboring sections. Artificial functional disc replacement through permanent metal and polymer-based components continues to evolve, but is far from recapitulating native disc structure and function, and suffers from the risk of unsuccessful tissue integration and device failure. Tissue engineering and regenerative medicine strategies combine novel material structures, bioactive factors and stem cells alone or in combination to repair and regenerate the IVD. These efforts are at very early stages and a more in-depth understanding of IVD metabolism and cellular environment will also lead to a clearer understanding of the native environment which the tissue engineering scaffold should mimic. The current review focusses on the strategies for a successful regenerative scaffold for IVD regeneration and the need for defining new materials, environments, and factors that are so finely tuned in the healthy human intervertebral disc in hopes of treating such a prevalent degenerative process.

Is There Any Relationship Between Cervical Disc Herniation and Blood Inflammatory Response?

Objective Inflammation plays an important role in the pathophysiology of disc herniation. The aim of this study was to evaluate blood neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and C-reactive protein (CRP) levels in cervical disc herniation (CDH) patients. Materials and methods We retrospectively analyzed the medical records of 126 patients with neck pain who were treated as inpatients at the Neurosurgery Department of Harran University Faculty of Medicine. The NLR, PLR, and CRP levels during hospital admissions were documented. Results The study included 73 patients with CDH and neck pain, 53 patients with normal cervical MR examination and neck pain, and 50 healthy control subjects. The group with cervical disc hernia had a significantly higher mean serum leucocyte count, neutrophil count, NLR, and CRP level compared to those with a normal MR but neck pain and the control group. NLR was significantly higher in the multi-level CDH group compared to the control group, while the single-level CDH and multi-level CDH had no significant difference with respect to mean serum inflammatory parameters. Conclusion Higher NLR and CRP in patients with CDH compared to patients with neck pain but normal cervical MR and the controls may be due to a developing inflammatory response. It may be speculated that among patients with neck pain, those with non-elevated NLR and CRP levels may have normal neck MR imaging, and in patients with elevated NLR and CRP levels, early protective approaches may play a preventive role in disc degeneration and cervical disc hernia development.

Signal Intensity of Lumbar Disc Herniations: Correlation With Age of Herniation for Extrusion, Protrusion, and Sequestration

Background

There is presently insufficient data on small groups of patients, without focus on time since herniation occurred and without establishing a valid method of measurement for signal intensity (SI) of a lumbar disc herniation (LDH) in a standard magnetic resonance imaging (MRI). SI could be reported in relation to SI of nucleus pulposus of herniated intervertebral disc, nucleus pulposus of a healthy "control" intervertebral disc, cerebral spinal fluid, or anterior anulus fibrosus. It is not known which signal intensity ratio (SIR) shows the highest correlation with time since onset of pain and how SIR of different Combined Task Forces (CTF)-types of herniation develop over time.

Methods

Out of 1053 patients, we enrolled 151 patients to a retrospective single-center analysis of standard MRIs of consecutive patients treated for LDH from February 2008 to December 2017 with confirmed (surgery, injection, or electrophysiologic testing) radicular pain by LDH and known exact date of onset of pain. We excluded patients < 18 or  > 70 years, with chronical pain syndrome, spinal deformity, and history of prior spinal surgery on the affected spinal level. Because data did not show normal distribution, we assessed correlation by Spearman rank correlation coefficient. Correlation (R) and coefficient of correlation (CC) are reported.

Results

SI of LDH referenced by SI of nucleus pulposus of the affected intervertebral disc and CTF type "extrusion" showed the highest correlations with time since onset of pain (R: -0.893; CC: 79.7), followed by CTF-type "sequestration" (R: -0.356; CC: 12.7).

Conclusions

SIR of extrusion referenced by nucleus pulposus of the affected intervertebral disc does show a high correlation with days since onset of herniation and may be applied to monitor changes of SI of LDH after herniation in standard MRIs of the lumbar spine.

Understanding sciatica: illness and treatment beliefs in a lumbar radicular pain population. A qualitative interview study

BACKGROUND

Several pathological processes contribute to lumbar radicular pain (LRP), commonly known as sciatica. It is not known how patients rationalise the experience of sciatica or understand the diagnosis. Providing clinicians with a better understanding of how patients conceptualise sciatica will help them to tailor information for patients on the management and treatment of the condition.

AIM

To understand patients' beliefs regarding their illness following a diagnosis of LRP, how these beliefs were developed, and the impact of illness beliefs on treatment beliefs.

DESIGN & SETTING

Qualitative interview study from a single NHS musculoskeletal interface service (in Wales, UK).

METHOD

Thirteen patients recently diagnosed with LRP were consecutively recruited. Individual semi-structured interviews were recorded and transcribed. Data were analysed using a thematic approach.

RESULTS

Four main themes were generated: (1) the illness experience (2) the concept of sciatica, (3) treatment beliefs, and (4) the desire for credible information.

CONCLUSION

The diagnosis of LRP is often communicated and understood within a compressive conceptual illness identity. Explaining symptoms with a compressive pathological model is easily understood by patients but may not accurately reflect the spectrum of pathological processes known to contribute to radicular pain. This model appears to inform patient beliefs about treatments. Clinicians should take care to fully explain the pathology prior to shared decision-making with patients.

Annular closure device lowers reoperation risk 4 years after lumbar discectomy

Objective

To determine whether implanting an annular closure device (ACD) following a lumbar discectomy procedure in patients with large defects in the annulus fibrosus lowers the risk of reoperation after 4 years.

Methods

In a multicenter randomized trial, patients with large annular defects following single-level lumbar discectomy were intraoperatively randomized to additionally receive an ACD or no treatment (Controls). Clinical and imaging follow-up were performed at routine intervals over 4 years of follow-up. Main outcomes included reoperations at the treated lumbar level, leg pain scores on a visual analog scale, Oswestry Disability Index (ODI), and Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the SF-36 questionnaire.

Results

Among 550 patients (ACD 272, Control 278), the risk of reoperation over 4 years was 14.4% with ACD and 21.1% with Controls (P=0.03). The reduction in reoperation risk with ACD was not significantly influenced by patient age (P=0.51), sex (P=0.34), body mass index (P=0.21), smoking status (P=0.85), level of herniation (P=0.26), leg pain severity at baseline (P=0.90), or ODI at baseline (P=0.54). All patient-reported outcomes improved in each group from baseline to 4 years (all P<0.001). The percentage of patients who achieved the minimal clinically important difference without a reoperation was proportionally higher in the ACD group compared to Controls for leg pain (P=0.07), ODI (P=0.10), PCS (P=0.02), and MCS (P=0.06).

Conclusion

The addition of a bone-anchored ACD following lumbar discectomy in patients with large post-surgical annular defects reduces the risk of reoperation and provides better long-term pain and disability relief over 4 years compared to lumbar discectomy only.

Effects of swimming on pain and inflammatory factors in rats with lumbar disc herniation

The aim of the present study was to identify the effect of swimming on nerve root pain in rats with lumbar disc herniation (LDH). A total of 72 male Sprague Dawley rats (215±15 g) were randomly divided into three groups (n=24/group): The sham operation, model and exercise intervention groups, with the latter undergoing 4 weeks of swimming training. On days 0, 7, 14 and 28 following surgery, the changes in the post-limb mechanical claw threshold, the phospholipase A2 (PLA2), interleukin (IL)-6 and tumor necrosis factor (TNF)-α mRNA expression levels, the secretory PLA2 (sPLA2) expression, the IL-6 and TNF-α content, the nuclear factor (NF)-κBp65 protein expression level in the nucleus pulposus, and the apoptotic rate of the nucleus pulposus cells were detected. The results demonstrated that, in the model group, the threshold of hind paw withdrawal was decreased, and that the sPLA2 expression, IL-6 and TNF-α content, PLA2, IL-6 and TNF-α mRNA and NF-κBp65 protein expression levels in the nucleus pulposus were increased. The apoptotic rate of the nucleus pulposus cells was increased from day 7 following surgery, as compared with the sham operation group. In the exercise intervention group, the hind paw withdrawal threshold increased and the TNF-α and IL-6 content, sPLA2 expression and PLA2, IL-6 and TNF-α mRNA and NF-κBp65 protein expression levels were decreased from day 14 following surgery, and the apoptotic nucleus pulposus cells were decreased from day 7 following surgery, as compared with the model group. Collectively, the present data suggest that swimming can significantly reduce nerve root pain and inhibit inflammatory reaction in LDH, which can have positive effects on the treatment of LDH.

Interleukin-1 Receptor Associated Kinase 1 Mediates the Maintenance of Neuropathic Pain after Chronic Constriction Injury in Rats

Neuropathic pain (NP) has complicated pathogenesis as it mainly involves a lesion or dysfunction of the somatosensory nervous system and its clinical treatment remains challenging. Chronic constriction injury (CCI) model is a widely used neuropathic pain model and involved in mechanisms including both nerve inflammatory and injury. Cytokines and their receptors play essential roles in the occurrence and persistence of neuropathic pain, but the underlying mechanisms have not well been understood. Therefore, Interleukin-1 receptor-associated kinase 1 (IRAK1) is chosen to explore the possible mechanisms of NP. In the present study, IRAK1 was found to persistently increase in the dorsal root ganglion (DRG) and spinal cord (SC) during CCI detected by western blot. The staining further confirmed that IRAK1 was mainly co-located in the DRG astrocytes or SC neurons, but less in the DRG microglia or SC astrocytes. Moreover, the region of increased IRAK1 expression was observed in superficial laminae of the spinal dorsal horn, which was the nociceptive neuronal expression domain, suggesting that IRAK1 may mediated CCI-induced pain by nociceptive primary afferent. In addition, intrathecal injection of Toll-like receptor 4 (TLR4) inhibitor or IRAK1 siRNA decreased the expression of IRAK1 accompanied with the alleviation of CCI-induced neuropathic pain. The upregulation of p-NF-κB expression was reversed by IRAK1 siRNA in SC, and intrathecal injection of p-NF-κB inhibitor relieved neuropathic pain. Taking together, targeting IRAK1 may be a potential treatment for chronic neuropathic pain.

Mineralocorticoid Antagonist Improves Glucocorticoid Receptor Signaling and Dexamethasone Analgesia in an Animal Model of Low Back Pain

Low back pain, a leading cause of disability, is commonly treated by epidural steroid injections that target the anti-inflammatory glucocorticoid receptor (GR). However, their efficacy has been controversial. All currently used epidural steroids also activate the pro-inflammatory mineralocorticoid receptor (MR) with significant potency. Local inflammation of the dorsal root ganglia (DRG), a rat model of low back pain, was used. This model causes static and dynamic mechanical allodynia, cold allodynia and guarding behavior (a measure of spontaneous pain), and activates the MR, with pro-nociceptive effects. In this study, effects of local Dexamethasone (DEX; a glucocorticoid used in epidural injections), and eplerenone (EPL; a second generation, more selective MR antagonist) applied to the DRG at the time of inflammation were examined. Mechanical and spontaneous pain behaviors were more effectively reduced by the combination of DEX and EPL than by either alone. The combination of steroids was particularly more effective than DEX alone or the model alone (3-fold improvement for mechanical allodynia) at later times (day 14). Immunohistochemical analysis of the GR in the DRG showed that the receptor was expressed in neurons of all size classes, and in non-neuronal cells including satellite glia. The GR immunoreactivity was downregulated by DRG inflammation (48%) starting on day 1, consistent with the reduction of GR (57%) observed by Western blot, when compared to control animals. On day 14, the combination of DEX and EPL resulted in rescue of GR immunoreactivity that was not seen with DEX alone, and was more effective in reducing a marker for satellite glia activation/neuroinflammation. The results suggest that EPL may enhance the effectiveness of clinically used epidural steroid injections, in part by enhancing the availability of the GR. Thus, the glucocorticoid-mineralocorticoid interactions may limit the effectiveness of epidural steroids through the regulation of the GR in the DRG.

Epidural versus intravenous steroids application following percutaneous endoscopic lumbar discectomy

Retrospectively study.The purpose of this study was to compare the effects of intraoperative epidural steroids and single dose intravenous steroids following a percutaneous endoscopic lumbar discectomy (PELD).Inflammatory irritation of dorsal root ganglia or sensory nerve roots may cause postoperative pain. Epidural steroids have been applied after a lumbar discectomy for more than 20 years. Epidural steroid application after a PELD is easier to perform and safer because the operations are under observation of the scope.We retrospectively reviewed the medical records of patients with lumbar intervertebral disc herniation who had undergone transforaminal PELD at our department. There are 60 patients in epidural steroid group, intravenous steroid group, and control group, respectively. Visual analog scores (VAS) and the Oswestry Disability Index (ODI) were collected. Successful pain control is defined as 50% or more reduction in back and leg pain (VAS scores).VAS scores (back and leg) and ODI showed a significant decrease in all groups when comparing pre- and postoperatively. Epidural steroid group had a significant improvement in successful pain control compared with the control group at 2 weeks of follow-up. VAS scores (leg) in the epidural steroid group showed a significant decrease compared with the intravenous steroids group at 1, 3, and 7 days after the surgery, but this difference had no statistical significance at 1, 6, and 12 months of follow-up. All groups did not show a significant difference in ODI at 1, 6, and 12 months follow-up.Epidural application of steroid has a better effect on controlling the postoperative pain of PELD in the short term. The epidural application of steroid did not show a tendency to cause infection.

Follistatin-like protein 1 promotes inflammatory reactions in nucleus pulposus cells by interacting with the MAPK and NFκB signaling pathways

Objective

Follistatin-like protein 1 (FSTL1) is a well-known mediator of inflammation. Intervertebral disc disease is an inflammatory disorder. Here, we investigated the role of FSTL1 in the intervertebral discs inflammation.

Methods

Expression of FSTL1 in nucleus pulposus tissues from rats and human was determined by immunohistochemistry staining and western blot analysis. The expression levels of tumor necrosis factor-α (TNF-α), interleukin1-β (IL-1β) and matrix metalloproteinase 13 (MMP-13) in human and rat nucleus pulposus tissues were measured by immunohistochemistry staining. The mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NFκB) signaling pathways were detected by western blotting.

Results

FSTL1 serum levels were significantly increased in lumbar disc herniation patients and had a positive correlation with Visual Analogue Scores. Additionally, FSTL1 expression was significantly increased in extrusion group compared with protrusion and control groups. Furthermore, FSTL1 expression was significantly increased in intervertebral disc degeneration models of rats. Immunohistochemistry staining demonstrated that the levels of TNF-α, IL-1β and MMP-13 were increased in the pathogenesis of intervertebral disc disease. Recombinant human FSTL1 significantly increased the production of proinflammatory cytokines in vitro. In addition, FSTL1 promoted inflammation by activating c-Jun N-terminal kinase (JNK), extracellular regulated protein kinases 1/2(ERK1/2) and NFκB signaling.

Conclusions

These data imply that FSTL1 expression was increased in the pathogenesis of intervertebral disc disease. Importantly, FSTL1 promoted inflammatory catabolism in the nucleus pulposus by activating JNK, ERK 1/2/MAPK and NFκB signaling.

Cytokine Involvement in Biological Inflammation Related to Degenerative Disorders of the Intervertebral Disk: A Narrative Review

Objective

The purpose of this narrative literature review is to discuss the literature regarding the potential role that cytokines play in degenerative disk disease.

Methods

The inclusion criteria were studies that used inflammatory mediators in advancing disk disease processes. Research studies were limited to the last 3 decades that had free full-text available online in English. Exclusion criteria were review articles and articles pertaining to temporomandibular joints and other joints of the body other than the intervertebral disk. The following databases were searched: PubMed, EBSCOhost, and Google Scholar through March 13, 2017.

Results

A total of 82 studies were included in this review. The papers were reviewed for complex mechanisms behind the degenerative cascade, emphasizing the role of proinflammatory cytokines, which may be instrumental in processes of inflammation, neurologic pain, and disk degeneration. Interleukin-1β and tumor necrosis factor α were among the more notable cytokines involved in this cascade. Because monocyte chemoattractant protein-1 stimulates and activates macrophages in the event of infiltration, additional proinflammatory cytokines are released to act on molecules to promote blood and nerve ingrowth, resulting in pain signaling and tissue degradation. Excessive inflammation and/or tissue damage initiates a pathologic imbalance between anabolic and catabolic processes.

Conclusions

This literature review describes how inflammatory and biochemical changes may trigger disk degeneration. Proinflammatory cytokines stimulate microvascular blood and nerve ingrowth, resulting in pain signaling and tissue degradation. This may sensitize a person to chemical and/or mechanical stimuli, contributing to severe low back pain.

Kinesio Taping in patients with lumbar disc herniation: A randomised, controlled, double-blind study

BACKGROUND

Lumbar disc herniation (LDH) causes pain and working day loss when activated. Patients spend most of their time in the hospital. And also it may limit patients' daily living activities. Kinesio Taping (KT) is a method that can be easily applied to the patients and does not interfere with their daily activities or movements of body.

OBJECTIVE

This study investigated the effects of KT in patients with low back pain due to LDH.

METHODS

Randomised-placebo controlled double blind clinical trial. Sixty Patients with low back pain due to LDH were randomised as KT group or placebo taping group. Taping was performed once a week for three weeks. Patients were followed up during twelve weeks. Numeric rating scale (NRS), lumbar flexion, Health Assessment Questionnaire (HAQ), Oswestry Disability Index (ODI) and paracetamol tablets taken were used for outcome measurements.

RESULTS

Demographic and clinical features of the groups were similar. There were significant improvements in all parameters during intervention period in groups. Improvements in NRS-activity, HAQ and ODI continued to twelfth weeks only in KT group. In KT group, analgesic need was significantly less at follow-up.

CONCLUSIONS

KT reduced analgesic need of patients with LDH when compared with placebo taping.

Inflammatory Processes Associated with Canine Intervertebral Disc Herniation

Intervertebral disc herniation (IVDH) is an important pathology in humans and also in dogs. While the molecular disease mechanisms are well investigated in humans, little is known about the inflammatory mediators in naturally occurring canine IVDH. The objective of this study was to investigate whether the involved proinflammatory cytokines in human IVDH are also key cytokines in canine IVDH and thus to elucidate the suitability of the dog as a model for human trials. 59 samples from 25 dogs with surgically confirmed thoracolumbar IVDH were collected and classified in three subgroups: herniated (H), affected non-herniated (NH) disc, and adjacent non-affected (NA) disc. Discs from 11 healthy dogs acted as controls (C). Samples were analyzed for IL-1, IL-6, IL-8, and TNF-α expression (qPCR/ELISA) as well as cell infiltration and activation of the MAP kinase pathways (immunohistochemistry). Gene and protein expression of all key cytokines could be detected in IVDH affected dogs. Canine IVDH was significantly associated with a higher gene expression of IL-6 (H > C, NH > C) and TNF-α (H > C, NH > C, NA > C) and a significant down-regulation of IL-1β (H < C). Dogs with spontaneous pain had significantly higher IL-6 mRNA compared to those with pain arising only upon palpation. An inter-donor comparison (H and HN relative to NA) revealed a significant increase of IL-6 gene expression (H > NA, NH > NA). IL-8 (H > C, NA > C) and TNF-α (NH > C) protein levels were significantly increased in diseased dogs while inversely, IL-6 protein levels were significantly higher in patients with better clinical outcome. Aside from resident IVD cells, mostly monocytes and macrophages were found in extruded material, with concomitant activation of extracellular signal-regulated kinase p38 in the majority of samples. Dogs with spontaneous IVDH might provide a useful model for human disc diseases. Although the expression of key cytokines found in human IVDH was also demonstrated in canine tissue, the inflammatory mechanisms accompanying canine IVDH diverges partially from humans, which will require further investigations in the future. In dogs, IL-6 seems to play an important pathological role and may represent a new potential therapeutic target for canine patients.

TNF-α promotes nuclear enrichment of the transcription factor TonEBP/NFAT5 to selectively control inflammatory but not osmoregulatory responses in nucleus pulposus cells

Intervertebral disc degeneration (IDD) causes chronic back pain and is linked to production of proinflammatory molecules by nucleus pulposus (NP) and other disc cells. Activation of tonicity-responsive enhancer-binding protein (TonEBP)/NFAT5 by non-osmotic stimuli, including proinflammatory molecules, occurs in cells involved in immune response. However, whether inflammatory stimuli activate TonEBP in NP cells and whether TonEBP controls inflammation during IDD is unknown. We show that TNF-α, but not IL-1β or LPS, promoted nuclear enrichment of TonEBP protein. However, TNF-α-mediated activation of TonEBP did not cause induction of osmoregulatory genes. RNA sequencing showed that 8.5% of TNF-α transcriptional responses were TonEBP-dependent and identified genes regulated by both TNF-α and TonEBP. These genes were over-enriched in pathways and diseases related to inflammatory response and inhibition of matrix metalloproteases. Based on RNA-sequencing results, we further investigated regulation of novel TonEBP targets CXCL1, CXCL2, and CXCL3 TonEBP acted synergistically with TNF-α and LPS to induce CXCL1-proximal promoter activity. Interestingly, this regulation required a highly conserved NF-κB-binding site but not a predicted TonE, suggesting cross-talk between these two members of the Rel family. Finally, analysis of human NP tissue showed that TonEBP expression correlated with canonical osmoregulatory targets TauT/SLC6A6, SMIT/SLC5A3, and AR/AKR1B1, supporting in vitro findings that the inflammatory milieu during IDD does not interfere with TonEBP osmoregulation. In summary, whereas TonEBP participates in the proinflammatory response to TNF-α, therapeutic strategies targeting this transcription factor for treatment of disc disease must spare osmoprotective, prosurvival, and matrix homeostatic activities.

Localized Sympathectomy Reduces Mechanical Hypersensitivity by Restoring Normal Immune Homeostasis in Rat Models of Inflammatory Pain

Some forms of chronic pain are maintained or enhanced by activity in the sympathetic nervous system (SNS), but attempts to model this have yielded conflicting findings. The SNS has both pro- and anti-inflammatory effects on immunity, confounding the interpretation of experiments using global sympathectomy methods. We performed a "microsympathectomy" by cutting the ipsilateral gray rami where they entered the spinal nerves near the L4 and L5 DRG. This led to profound sustained reductions in pain behaviors induced by local DRG inflammation (a rat model of low back pain) and by a peripheral paw inflammation model. Effects of microsympathectomy were evident within one day, making it unlikely that blocking sympathetic sprouting in the local DRGs or hindpaw was the sole mechanism. Prior microsympathectomy greatly reduced hyperexcitability of sensory neurons induced by local DRG inflammation observed 4 d later. Microsympathectomy reduced local inflammation and macrophage density in the affected tissues (as indicated by paw swelling and histochemical staining). Cytokine profiling in locally inflamed DRG showed increases in pro-inflammatory Type 1 cytokines and decreases in the Type 2 cytokines present at baseline, changes that were mitigated by microsympathectomy. Microsympathectomy was also effective in reducing established pain behaviors in the local DRG inflammation model. We conclude that the effect of sympathetic fibers in the L4/L5 gray rami in these models is pro-inflammatory. This raises the possibility that therapeutic interventions targeting gray rami might be useful in some chronic inflammatory pain conditions.

SIGNIFICANCE STATEMENT

Sympathetic blockade is used for many pain conditions, but preclinical studies show both pro- and anti-nociceptive effects. The sympathetic nervous system also has both pro- and anti-inflammatory effects on immune tissues and cells. We examined effects of a very localized sympathectomy. By cutting the gray rami to the spinal nerves near the lumbar sensory ganglia, we avoided widespread sympathetic denervation. This procedure profoundly reduced mechanical pain behaviors induced by a back pain model and a model of peripheral inflammatory pain. One possible mechanism was reduction of inflammation in the sympathetically denervated regions. This raises the possibility that therapeutic interventions targeting gray rami might be useful in some inflammatory conditions.

Celastrol reduces IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo

Celastrol has been reported to exert therapeutic potential on pro-inflammatory diseases including asthma, Crohn's disease, arthritis and neurodegenerative disorders via inhibiting NF-κB pathway. While the effect of celastrol on intervertebral disc degeneration (IDD), which is also a pro-inflammatory disease, remains unknown. In this study, we evaluated the effect of celastrol on IDD in IL-1β treated human nucleus pulposus cells in vitro as well as in puncture induced rat IDD model in vivo. Our results showed that celastrol reduced the expression of catabolic genes (MMP-3, 9, 13, ADAMTS-4, 5), oxidative stress factors (COX-2, iNOS) and pro-inflammatory factors (IL-6, TNF-a) induced by IL-1β in nucleus pulposus cells, also phosphorylation of IκBα and p65 were attenuated by celastrol, indicating NF-κB pathway was inhibited by celastrol in nucleus pulposus cells. In vivo study showed that celastrol treated rats had stronger T2-weighted signal than vehicle-treated rats at 2 weeks and 6 weeks' time point, suggesting celastrol could attenuate intervertebral disc degeneration in vivo. Together, our study demonstrates that celastrol could reduce IL-1β induced matrix catabolism, oxidative stress and inflammation in human nucleus pulposus cells and attenuates rat intervertebral disc degeneration in vivo, which shows its potential to be a therapeutic drug for IDD.

Protective role of 17β-estradiol on tumor necrosis factor-α-induced apoptosis in human nucleus pulposus cells

The molecular mechanisms underlying protection and pathogenesis in spinal degenerative diseases remain unclear. Tumor necrosis factor-α (TNF-α) has been demonstrated to induce apoptosis of intervertebral disc (IVD) cells during IVD degeneration, and 17β-estradiol (17β-E2) has a protective effect against IVD cell apoptosis. However, the underlying molecular mechanism by which 17β-E2 protects nucleus pulposus (NP) cells remains to be investigated. The aim of the present study was to evaluate whether 17β-E2 modulates apoptosis of human NP cells induced by TNF-α. In addition, the concentration-response effect of 17β-E2 on human NP cells was investigated. Human NP cells were cultured in complete medium, which was replaced every three days until the culture was ~80% confluent. Cells were treated with 100 ng/ml TNF-α for 48 h, with or without pretreatment with various concentrations of 17β-E2, and ICI 182,780, for 30 min. Morphologic alterations characteristic of apoptosis were observed by inverted phase-contrast microscopy and Hoechst 33258 staining; the apoptosis rate was analyzed by flow cytometry. A Cell Counting kit-8 assay was used to assess cell proliferation. Furthermore, caspase-3 activity was determined and proteins associated with apoptosis were analyzed by western blotting. The level of apoptosis and caspase-3 activity in human NP cells increased, whereas proliferation and the expression of poly ADP-ribose polymerase decreased following TNF-α treatment. These effects of TNF-α were abolished by pretreatment with 17β-E2 in a concentration-dependent manner. The results of the present study indicated that 17β-E2 serves a critical role in the survival of degenerative human NP cells.

Animal models for disc degeneration-an update

Intervertebral disc degeneration is considered a major cause of back pain that places a heavy burden on society, both because of its effect on the physiology of individuals and its consequences on the world economy. During the past few decades, research findings in the pre-clinical setting have led to a significant increase in the understanding of intervertebral disc degeneration, although many aspects of the disease remain unclear. The goal of this review is to summarize existing animal models for disc degeneration studies and the difficulties that are associated with the use of such models. A firm understanding of the cellular and molecular events that ensue as a result of injuries, as well as environmental factors, could be instrumental in the development of targeted therapies for the treatment of intervertebral disc degeneration.

Inhibition of cystathionine β-synthetase suppresses sodium channel activities of dorsal root ganglion neurons of rats with lumbar disc herniation

The pathogenesis of pain in lumbar disc herniation (LDH) remains poorly understood. We have recently demonstrated that voltage-gated sodium channels (VGSCs) in dorsal root ganglion (DRG) neurons were sensitized in a rat model of LDH. However, the detailed molecular mechanism for sensitization of VGSCs remains largely unknown. This study was designed to examine roles of the endogenous hydrogen sulfide synthesizing enzyme cystathionine β-synthetase (CBS) in sensitization of VGSCs in a previously validated rat model of LDH. Here we showed that inhibition of CBS activity by O-(Carboxymethyl) hydroxylamine hemihydrochloride (AOAA) significantly attenuated pain hypersensitivity in LDH rats. Administration of AOAA also reduced neuronal hyperexcitability, suppressed the sodium current density, and right-shifted the V_1/2 of the inactivation curve, of hindpaw innervating DRG neurons, which is retrogradely labeled by DiI. In vitro incubation of AOAA did not alter the excitability of acutely isolated DRG neurons. Furthermore, CBS was colocalized with Na_V1.7 and Na_V1.8 in hindpaw-innervating DRG neurons. Treatment of AOAA markedly suppressed expression of Na_V1.7 and Na_V1.8 in DRGs of LDH rats. These data suggest that targeting the CBS-H₂S signaling at the DRG level might represent a novel therapeutic strategy for chronic pain relief in patients with LDH.

Serum Levels of the Inflammatory Cytokines in Patients with Lumbar Radicular Pain Due to Disc Herniation

Study Design

Cohort study.

Purpose

This study primarily aimed to evaluate the serum levels of tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-4 in patients with lumbar radiculopathy 1 and 12 months after microdiscectomy.

Overview of Literature

Lumbar radiculopathy is possibly caused by inflammatory changes in the nerve root. The intraneural application of pro-inflammatory cytokines induces behavioral signs associated with pain. Anti-inflammatory cytokine treatment effectively reduces hyperalgesia.

Methods

The role of TNF-α and IL-4 in long-lasting lumbar radiculopathy was addressed. A total of 262 patients were recruited from Anqing Hospital, Anhui Medical University. During inclusion at 1 and 12 months, serum concentrations of TNF-α and IL-4 were analyzed by enzyme-linked immunosorbent assay, and pain intensity was reported on a 0–10 cm visual analog scale (VAS).

Results

Sixty six patients had VAS <3 and 196 patients had VAS ≥3. Serum concentrations of pro-inflammatory TNF-α and anti-inflammatory IL-4 in patients with lumbar radiculopathy related to disc herniation were measured at 1- and 12-month follow-up. TNF-α decreased in both VAS groups with time. In contrast, IL-4 increased in both groups at 1 month and then decreased gradually until month 12. The changes in serum levels of TNF-α and IL-4 over time between the VAS ≥3 and VAS <3 groups were significantly different.

Conclusions

Chronic lumbar radiculopathy may be associated with high level of pro-inflammatory substances, such as TNF-α, in serum after disc herniation, and elevated anti-inflammatory cytokine in patients with lumbar radiculopathy may indicate a favorable outcome.

Mineralocorticoid Receptor, A Promising Target for Improving Management of Low Back Pain by Epidural Steroid Injections

AIM OF REVIEW

Low back pain is a major health problem in United States and worldwide. In this review, we aim to show that mineralocorticoid receptor (MR) activation has a critical role in the initiation of immune and inflammatory responses, which in turn can impact the effectiveness of the currently used steroids for epidural injections in low back pain management since most steroids activate MR in addition to the primary target, glucocorticoid receptor (GR). Moreover, we would like to determine some of the benefits of blocking the MR-induced negative effects. Overall, we propose a novel therapeutic approach for low back pain management by using a combination of a MR antagonist and a GR agonist in the epidural injections.

METHOD

We will first introduce the societal cost of low back pain and discuss how epidural steroid injections became a popular treatment for this condition. We will then describe several preclinical models used for the study of low back pain conditions and the findings with respect to the role of MR in the development of inflammatory low back pain.

RECENT FINDINGS

MR has pro-inflammatory effects in many tissues which can counteract the anti-inflammatory effects induced by GR activation. Blocking MR using the selective MR antagonist eplerenone can reduce pain and sensory neuron excitability in experimental models of low back pain. Moreover, combining the MR antagonist with clinically used steroids is more effective in reducing pain behaviors than using the steroids alone.

SUMMARY

MR antagonists are promising candidates to increase the effectiveness of currently used steroids. Since the activation of the MR is evident in preclinical models of low back pain, blocking its deleterious effects can be beneficial in managing inflammatory pain conditions.

Reduction of Leg Pain by Oxiplex Gel After Lumbar Discectomy in Patients With Predominant Leg Pain and Elevated Levels of Lower Back Pain: A Prospective, Randomized, Blinded, Multicenter Clinical Study

STUDY DESIGN

A prospective, randomized, blinded, multicenter clinical study.

OBJECTIVE

To evaluate carboxymethylcellulose/polyethylene oxide gel (Oxiplex) in improving clinical outcomes in subjects having predominant leg pain and elevated low back pain undergoing first-time lumbar discectomy for disk herniation.

SUMMARY OF BACKGROUND DATA

Clinical studies in the United States and Italy found that Oxiplex reduced leg pain after decompression surgery.

METHODS

A total of 68 subjects with herniated lumbar disk were enrolled and randomized into treatment (surgery plus gel) or surgery-only control groups. A prospective statistical analysis assessed the effect of gel in the severe back pain subgroup (prespecified as greater than or equal to median baseline back pain of the population studied). All subjects except 2 controls lost to follow-up completed the study. Preoperative and postoperative visual analogue scale leg pain scores were analyzed and compared between groups at 60 days after surgery.

RESULTS

There were no serious adverse events or neurological safety concerns reported in any patients. Gel-treated patients had statistically significantly lower visual analogue scale leg pain scores at study end compared with controls (P=0.0240), representing a 21% additional reduction in leg pain compared with surgery alone in the severe baseline back pain subgroup (P=0.0240). The proportion of subgroup patients experiencing zero leg pain at study end was significantly higher in the gel treatment group (60%) than in the control group (23%) (P=0.0411).

CONCLUSIONS

The data from this study confirm and extend results of 2 previous studies in Italy and the United States that reported statistically significantly greater reductions in leg pain in gel-treated patients with severe preoperative low back pain compared with patients who only underwent decompression surgery.

Hyperexcitability and sensitization of sodium channels of dorsal root ganglion neurons in a rat model of lumber disc herniation

PURPOSE

Low back pain and sciatica are the most common symptoms of patients with lumbar disc herniation (LDH). The pathophysiology of lumbocrural pain and sciatica is not fully understood. The aim of the present study was to define the membrane properties and activities of voltage-gated sodium channels of dorsal root ganglion (DRG) neurons in a rat model of LDH.

METHODS

LDH was established by transplantation of autologous nucleus pulposus (NP) to lumbar 5 and 6 spinal nerves (L5-L6 DRG) of adult male rats. Mechanical paw withdrawal threshold (PWT) and thermal paw withdrawal latency (PWL) were measured 1 day before and through 35 days after transplantation of NP. Changes in expression of VGSCs were determined by western blotting. L5-L6 DRGs neurons innervating the hindpaw were labeled with DiI and acutely dissociated for measuring excitability and sodium channel currents under whole-cell patch clamp configurations.

RESULTS

NP transplantation significantly reduced the PWT and PWL in association with a significant reduction in rheobase and an increase in numbers of action potentials evoked by 2X and 3X rheobase current stimulation. Voltage-gated sodium current density was significantly enhanced in L5-L6 DRG neurons from LDH rats. The inactivation curve showed a leftward shift in LDH rats while activation curve did not significantly alter. However, NP transplantation remarkably enhanced expression of NaV1.7 and NaV1.8 in L5-L6 DRGs but not in T10-12 DRGs.

CONCLUSION

These data suggest that NP application produces pain-related behavior and potentiates sodium current density of DRG neurons, which is most likely mediated by enhanced expression of NaV1.7 and NaV1.8.

Lipoxin A4 attenuates radicular pain possibly by inhibiting spinal ERK, JNK and NF-κB/p65 and cytokine signals, but not p38, in a rat model of non-compressive lumbar disc herniation

Inflammatory response induced by protrused nucleus pulposus (NP) has been shown to play a crucial role in the process of radicular pain. Lipoxins represent a unique class of lipid mediators that have anti-inflammatory and pro-resolving action. The present study was undertaken to investigate if intrathecal lipoxin A4 (LXA4) could alleviate mechanical allodynia in the rat models of application of NP to the L5 dorsal root ganglion (DRG). Non-compressive models of application of NP to L5 DRG were established and intrathecal catheterization for drug administration was performed in rats. Daily intrathecal injection of vehicle or LXA4 (10ng or 100ng) was performed for three successive days post-operation. Mechanical thresholds were tested and the ipsilateral lumbar (L4-L6) segment of spinal dorsal horns were removed for the determination of tumor necrosis factor-α (TNF-α), IL-1β, transforming growth factor-β1 (TGF-β1) and IL-10 expression and NF-κB/p65, extracellular signal-regulated kinase (ERK), C-Jun N-terminal kinase (JNK) and P38 expression. Application of NP to DRG in rats induced mechanical allodynia, increased the expression of pro-inflammatory factors (TNF-α and IL-1β), NF-κB/p65, the phosphorylated-ERK (p-ERK), -JNK (p-JNK) and -P38 (p-p38) and decreased the expression of anti-inflammatory cytokines (TGF-β1 and IL-10) in the ipsilateral lumbar (L4-L6) segment of spinal dorsal horns. Intrathecal injection of LXA4 alleviated the development of neuropathic pain, inhibited the upregulation of pro-inflammatory cytokines (TNF-α and IL-1β), upregulated the expression of anti-inflammatory cytokines (TGF-β1 and IL-10) and attenuated the activation of NF-κB/p65, p-ERK, p-JNK, but not p-p38, in a dose-dependent manner. In this study, we have demonstrated that LXA4 potently alleviate radicular pain in a rat model of non-compressive lumbar disc herniation. The anti-inflammatory and pro-resolution properties of LXA4 have shown a great promise for the management of radicular pain caused by intervertebral disc herniation.

Advancing the cellular and molecular therapy for intervertebral disc disease

The healthy intervertebral disc (IVD) fulfils the essential function of load absorption, while maintaining multi-axial flexibility of the spine. The interrelated tissues of the IVD, the annulus fibrosus, the nucleus pulposus, and the cartilaginous endplate, are characterised by their specific niche, implying avascularity, hypoxia, acidic environment, low nutrition, and low cellularity. Anabolic and catabolic factors balance a slow physiological turnover of extracellular matrix synthesis and breakdown. Deviations in mechanical load, nutrient supply, cellular activity, matrix composition and metabolism may initiate a cascade ultimately leading to tissue dehydration, fibrosis, nerve and vessel ingrowth, disc height loss and disc herniation. Spinal instability, inflammation and neural sensitisation are sources of back pain, a worldwide leading burden that is challenging to cure. In this review, advances in cell and molecular therapy, including mobilisation and activation of endogenous progenitor cells, progenitor cell homing, and targeted delivery of cells, genes, or bioactive factors are discussed.

Sensitization of P2X3 receptors by cystathionine β-synthetase mediates persistent pain hypersensitivity in a rat model of lumbar disc herniation

Lumbar disc herniation (LDH) is a major cause of discogenic low back pain and sciatica, but the underlying mechanisms remain largely unknown. Hydrogen sulfide (H₂S) is becoming recognized for its involvement in a wide variety of processes including inflammation and nociception. The present study was designed to investigate the roles of the H₂S signaling pathway in the regulation of expression and function of purinergic receptors (P2XRs) in dorsal root ganglion (DRG) neurons from rats with LDH. LDH was induced by implantation of autologous nucleus pulposus (NP), harvested from rat tail, in lumbar 5 and 6 spinal nerve roots. Implantation of autologous NP induced persistent pain hypersensitivity, which was partially reversed by an intrathecal injection of A317491, a potent inhibitor of P2X3Rs and P2X2/3Rs. The NP induced persistent pain hypersensitivity was associated with the increased expression of P2X3Rs, but not P2X1Rs and P2X2Rs, receptors in L5-6 DRGs. NP implantation also produced a 2-fold increase in ATP-induced intracellular calcium signals in DRG neurons when compared to those of controls (P < 0.05). Interestingly, NP implantation significantly enhanced expression of the endogenous hydrogen sulfide producing enzyme, cystathionine-β-synthetase (CBS). Systematic administration of O-(Carboxymethyl) hydroxylamine hemihydrochloride (AOAA), an inhibitor of CBS, suppressed the upregulation of P2X3R expression and the potentiation of ATP-induced intracellular calcium signals in DRG neurons (P < 0.05). Intrathecal injection of AOAA markedly attenuated NP induced- persistent pain hypersensitivity. Our results suggest that sensitization of P2X3Rs, which is likely mediated by CBS-H₂S signaling in primary sensory neurons, contributes to discogenic pain. Targeting CBS/H₂S-P2X3R signaling may represent a potential treatment for neuropathic pain caused by LDH.

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.

Protective effects of cannabidiol on lesion-induced intervertebral disc degeneration

Disc degeneration is a multifactorial process that involves hypoxia, inflammation, neoinnervation, accelerated catabolism, and reduction in water and glycosaminoglycan content. Cannabidiol is the main non-psychotropic component of the Cannabis sativa with protective and anti-inflammatory properties. However, possible therapeutic effects of cannabidiol on intervertebral disc degeneration have not been investigated yet. The present study investigated the effects of cannabidiol intradiscal injection in the coccygeal intervertebral disc degeneration induced by the needle puncture model using magnetic resonance imaging (MRI) and histological analyses. Disc injury was induced in the tail of male Wistar rats via a single needle puncture. The discs selected for injury were punctured percutaneously using a 21-gauge needle. MRI and histological evaluation were employed to assess the results. The effects of intradiscal injection of cannabidiol (30, 60 or 120 nmol) injected immediately after lesion were analyzed acutely (2 days) by MRI. The experimental group that received cannabidiol 120 nmol was resubmitted to MRI examination and then to histological analyses 15 days after lesion/cannabidiol injection. The needle puncture produced a significant disc injury detected both by MRI and histological analyses. Cannabidiol significantly attenuated the effects of disc injury induced by the needle puncture. Considering that cannabidiol presents an extremely safe profile and is currently being used clinically, these results suggest that this compound could be useful in the treatment of intervertebral disc degeneration.

Dominance of chemokine ligand 2 and matrix metalloproteinase-2 and -9 and suppression of pro-inflammatory cytokines in the epidural compartment after intervertebral disc extrusion in a canine model

BACKGROUND CONTEXT

In canine intervertebral disc (IVD) disease, a useful animal model, only little is known about the inflammatory response in the epidural space.

PURPOSE

To determine messenger RNA (mRNA) expressions of selected cytokines, chemokines, and matrix metalloproteinases (MMPs) qualitatively and semiquantitatively over the course of the disease and to correlate results to neurologic status and outcome.

STUDY DESIGN/SETTING

Prospective study using extruded IVD material of dogs with thoracolumbar IVD extrusion.

PATIENT SAMPLE

Seventy affected and 13 control (24 samples) dogs.

OUTCOME MEASURES

Duration of neurologic signs, pretreatment, neurologic grade, severity of pain, and outcome were recorded. After diagnostic imaging, decompressive surgery was performed.

METHODS

Messenger RNA expressions of interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor (TNF), interferon (IFN)γ, MMP-2, MMP-9, chemokine ligand (CCL)2, CCL3, and three housekeeping genes was determined in the collected epidural material by Panomics 2.0 QuantiGene Plex technology. Relative mRNA expression and fold changes were calculated. Relative mRNA expression was correlated statistically to clinical parameters.

RESULTS

Fold changes of TNF, IL-1β, IL-2, IL-4, IL-6, IL-10, IFNγ, and CCL3 were clearly downregulated in all stages of the disease. MMP-9 was downregulated in the acute stage and upregulated in the subacute and chronic phase. Interleukin-8 was upregulated in acute cases. MMP-2 showed mild and CCL2 strong upregulation over the whole course of the disease. In dogs with severe pain, CCL3 and IFNγ were significantly higher compared with dogs without pain (p=.017/.020). Dogs pretreated with nonsteroidal anti-inflammatory drugs revealed significantly lower mRNA expression of IL-8 (p=.017).

CONCLUSIONS

The high CCL2 levels and upregulated MMPs combined with downregulated T-cell cytokines and suppressed pro-inflammatory genes in extruded canine disc material indicate that the epidural reaction is dominated by infiltrating monocytes differentiating into macrophages with tissue remodeling functions. These results will help to understand the pathogenic processes representing the basis for novel therapeutic approaches. The canine IVD disease model will be rewarding in this process.

The effects of glucocorticoids on neuropathic pain: a review with emphasis on intrathecal methylprednisolone acetate delivery

Methylprednisolone acetate (MPA) has a long history of use in the treatment of sciatic pain and other neuropathic pain syndromes. In several of these syndromes, MPA is administered in the epidural space. On a limited basis, MPA has also been injected intrathecally in patients suffering from postherpetic neuralgia and complex regional pain syndrome. The reports on efficacy of intrathecal administration of MPA in neuropathic pain patients are contradictory, and safety is debated. In this review, we broadly consider mechanisms whereby glucocorticoids exert their action on spinal cascades relevant to the pain arising after nerve injury and inflammation. We then focus on the characteristics of the actions of MPA in pharmacokinetics, efficacy, and safety when administered in the intrathecal space.

Effect of low level laser therapy on chronic compression of the dorsal root ganglion

Dorsal root ganglia (DRG) are vulnerable to physical injury of the intervertebral foramen, and chronic compression of the DRG (CCD) an result in nerve root damage with persistent morbidity. The purpose of this study was to evaluate the effects of low level laser therapy (LLLT) on the DRG in a CCD model and to determine the mechanisms underlying these effects. CCD rats had L-shaped stainless-steel rods inserted into the fourth and fifth lumbar intervertebral foramen, and the rats were then subjected to 0 or 8 J/cm2 LLLT for 8 consecutive days following CCD surgery. Pain and heat stimuli were applied to test for hyperalgesia following CCD. The levels of TNF-α, IL-1β and growth-associated protein-43 (GAP-43) messenger RNA (mRNA) expression were measured via real-time PCR, and protein expression levels were analyzed through immunohistochemical analyses. Our data indicate that LLLT significantly decreased the tolerable sensitivity to pain and heat stimuli in the CCD groups. The expression levels of the pro-inflammatory cytokines TNF-α and IL-1β were increased following CCD, and we found that these increases could be reduced by the application of LLLT. Furthermore, the expression of GAP-43 was enhanced by LLLT. In conclusion, LLLT was able to enhance neural regeneration in rats following CCD and improve rat ambulatory behavior. The therapeutic effects of LLLT on the DRG during CCD may be exerted through suppression of the inflammatory response and induction of neuronal repair genes. These results suggest potential clinical applications for LLLT in the treatment of compression-induced neuronal disorders.

Contribution of chemokine CCL2/CCR2 signaling in the dorsal root ganglion and spinal cord to the maintenance of neuropathic pain in a rat model of lumbar disc herniation

Lumbar disc herniation (LDH) is a major cause of sciatica, but the underlying mechanisms are not well understood. Chemokine CCL2 has been implicated to play a vital role in the neuroinflammation and central sensitization after spinal nerve ligation. Here we investigated the expression and the role of CCL2 and its receptor CCR2 in LDH-induced pain. Implantation of autologous nucleus pulposus induced persistent pain hypersensitivity, associated with increased mRNA expression of CCL2 and CCR2 in the dorsal root ganglion and spinal cord. Interestingly, CCL2 was increased in neurons and CCR2 was mainly increased in macrophages in the dorsal root ganglion, whereas CCL2 and CCR2 were increased in astrocytes and neurons, respectively, in the spinal cord. Intrathecal injection of CCR2 antagonist RS504393 at 3 days or 10 days significantly attenuated nucleus pulposus-induced mechanical allodynia. The results suggest that CCL2/CCR2 in the dorsal root ganglion and spinal cord is involved in the maintenance of LDH-induced pain. Targeting CCL2/CCR2 signaling may be a potential treatment for chronic radicular neuropathic pain.

PERSPECTIVE

These results suggest that CCL2/CCR2 signaling in the dorsal root ganglion and spinal cord is involved in LDH-induced pain via distinct mechanisms. These findings provide evidence of the antinociceptive effect of CCR2 antagonist on radicular neuropathic pain.