Single Intradiscal Administration of the Tumor Necrosis Factor-Alpha Inhibitor, Etanercept, for Patients with Discogenic Low Back Pain

Pharmacokinetics of PP353, a formulation of linezolid for intervertebral disc administration, in patients with chronic low back pain and Modic change Type 1: A first-in-human, Phase 1b, open-label, single-dose study

Background

Bacterial infection of the intervertebral disc is difficult to treat because the tissue is usually not vascularized and systemic antibiotic therapy may not reach optimal antibacterial exposure. Here we characterize the safety, tolerability, and pharmacokinetics of PP353, a suspension of micronized linezolid, formulated for direct intervertebral disc administration.

Methods

The safety, tolerability, and pharmacokinetics of an intradiscal administration of PP353, was assessed in Part A of a Phase 1b study and consisted of a single injection of study drug (3 mL of PP353 and 150 mg linezolid). Clinical assessment included initial safety and tolerability of PP353 with continued follow-up for 12 months. Assessment of linezolid concentration in plasma samples enabled characterization of the pharmacokinetics. Deconvolution of systemic linezolid was used to estimate intervertebral disc linezolid concentration.

Results

Intradiscal administration of 3 mL of PP353 (linezolid 50 mg/mL) to the nucleus pulposus was well tolerated with no reported study treatment-related severe or serious adverse events and resulted in an average geometric mean linezolid plasma C max of 1300 ng/mL at 7.27 h post-administration. The linezolid plasma C max observed with intradiscal PP353 is approximately 10% that observed with a standard oral or iv administration of 600 mg linezolid. Pharmacokinetic deconvolution estimated that a single dose of PP353 (150 mg linezolid) provided intradiscal bactericidal concentration of linezolid for 96 h and bacteriostatic exposure for up to 120 h after dosing.

Conclusion

Intradiscal administration of 3 mL of PP353 is well-tolerated and based on the pharmacokinetics following a single injection, a two-dose regimen of PP353 (150 mg linezolid) on Day 1 and Day 5 ± 1 was selected to explore safety, tolerability, pharmacokinetics, and efficacy in Part B of the Persica 002 study.

Regenerative therapies for lumbar degenerative disc diseases: a literature review

This review aimed to summarize the recent advances and challenges in the field of regenerative therapies for lumbar disc degeneration. The current first-line treatment options for symptomatic lumbar disc degeneration cannot modify the disease process or restore the normal structure, composition, and biomechanical function of the degenerated discs. Cell-based therapies tailored to facilitate intervertebral disc (IVD) regeneration have been developed to restore the IVD extracellular matrix or mitigate inflammatory conditions. Human clinical trials on Mesenchymal Stem Cells (MSCs) have reported promising outcomes exhibited by MSCs in reducing pain and improving function. Nucleus pulposus (NP) cells possess unique regenerative capacities. Biomaterials aimed at NP replacement in IVD regeneration, comprising synthetic and biological materials, aim to restore disc height and segmental stability without compromising the annulus fibrosus. Similarly, composite IVD replacements that combine various biomaterial strategies to mimic the native disc structure, including organized annulus fibrosus and NP components, have shown promise. Furthermore, preclinical studies on regenerative medicine therapies that utilize cells, biomaterials, growth factors, platelet-rich plasma (PRP), and biological agents have demonstrated their promise in repairing degenerated lumbar discs. However, these therapies are associated with significant limitations and challenges that hinder their clinical translation. Thus, further studies must be conducted to address these challenges.

Development of a Multimodal, Personalized Intervention of Virtual Reality Integrated Within Physiotherapy for Patients With Complex Chronic Low-Back Pain

Background

Chronic low-back pain (CLBP) is the leading cause of years lived with disability. Physiotherapy is the most common treatment option for CLBP, but effects are often unsatisfactory. Virtual reality (VR) offers possibilities to enhance the effectiveness of physiotherapy treatment. Primary aim was to develop and test a personalized VR intervention integrated within a physiotherapy treatment for patients with CLBP.

Methods

This study describes an intervention development process using mixed methods design that followed the Medical Research Council (MRC) framework. This involved a cocreation process with patients, physiotherapists, and researchers. A draft intervention was constructed based on a literature review and focus groups, and subsequently tested in a feasibility study and evaluated in focus groups. Focus group data were analyzed using thematic analysis. This intervention development process resulted in a final intervention.

Results

Focus group data showed that VR and physiotherapy can strengthen each other when they are well integrated, and that VR needs to be administered under the right conditions including flawless technology, physiotherapists with sufficient affinity and training, and the right expectations from patients. The draft intervention was considered feasible after evaluation by four patients and three physiotherapists and was further complemented by expanding the training for physiotherapists and improving the protocols for physiotherapists and patients. The final intervention consisted of a 12-week physiotherapy treatment with three integrated VR modules: pain education, physical exercise, and relaxation.

Conclusion

Using the MRC framework in cocreation with the end users, a personalized VR intervention integrated within a physiotherapy treatment for patients with CLBP was developed. This intervention was found to be feasible and will subsequently be evaluated for (cost-)effectiveness in a cluster randomized controlled trial.

Therapeutic TNF-alpha Delivery After CRISPR Receptor Modulation in the Intervertebral Disc

Low back pain (LBP) ranks among the leading causes of disability worldwide and generates a tremendous socioeconomic cost. Disc degeneration, a leading contributor to LBP, can be characterized by the breakdown of the extracellular matrix of the intervertebral disc (IVD), disc height loss, and inflammation. The inflammatory cytokine TNF-α has multiple pathways and has been implicated as a primary mediator of disc degeneration. We tested our ability to regulate the multiple TNF-α inflammatory signaling pathways in vivo utilizing CRISPR receptor modulation to slow the progression of disc degeneration in rats. Sprague-Dawley rats were treated with CRISPRi-based epigenome-editing therapeutics targeting TNFR1 and showed a decrease in behavioral pain in a disc degeneration model. Surprisingly, while treatment with the vectors alone was therapeutic, TNF-α injection itself became therapeutic after TNFR1 modulation. These results suggest direct inflammatory receptor modulation, to harness beneficial inflammatory signaling pathways, as a potent strategy for treating disc degeneration.

Application of platelet-rich plasma in spinal surgery

With the aging of the population and changes in lifestyle, the incidence of spine-related diseases is increasing, which has become a major global public health problem; this results in a huge economic burden on the family and society. Spinal diseases and complications can lead to loss of motor, sensory, and autonomic functions. Therefore, it is necessary to identify effective treatment strategies. Currently, the treatment of spine-related diseases includes conservative, surgical, and minimally invasive interventional therapies. However, these treatment methods have several drawbacks such as drug tolerance and dependence, adjacent spondylosis, secondary surgery, infection, nerve injury, dural rupture, nonunion, and pseudoarthrosis. Further, it is more challenging to promote the regeneration of the interstitial disc and restore its biomechanical properties. Therefore, clinicians urgently need to identify methods that can limit disease progression or cure diseases at the etiological level. Platelet-rich plasma (PRP), a platelet-rich form of plasma extracted from venous blood, is a blood-derived product. Alpha granules contain a large number of cytokines, such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor, platelet factor 4 (PF-4), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β (TGF-β). These growth factors allow stem cell proliferation and angiogenesis, promote bone regeneration, improve the local microenvironment, and enhance tissue regeneration capacity and functional recovery. This review describes the application of PRP in the treatment of spine-related diseases and discusses the clinical application of PRP in spinal surgery.

Presence of Tumor Necrosis Factor-Alpha in Urine Samples of Patients With Chronic Low Back Pain Undergoing Chiropractic Care: Preliminary Findings From a Prospective Cohort Study

Background and aims

Low back pain is the leading cause of years lived with disability worldwide. Chiropractors employ different interventions to treat low back pain, including spinal manipulative therapy, although the mechanisms through which chiropractic care improves low back pain are still unclear. Clinical research and animal models suggest that spinal manipulation might modulate plasma levels of inflammatory cytokines, which have been involved in different stages of low back pain. More specifically, serum levels of Tumor Necrosis Factor-alpha (TNF-α) have been found to be elevated in patients with chronic low back pain. We aimed to investigate whether urine from chronic low back pain patients could be an appropriate medium to measure concentrations of TNF-α and to examine possible changes in its levels associated to chiropractic care.

Methods

Urine samples were collected from 24 patients with chronic low back pain and TNF-α levels were analyzed by ELISA before and after 4-6 weeks of care compared to a reference value obtained from 5 healthy control subjects, by means of a Welch's t-test. Simultaneously, pain intensity and disability were also evaluated before and after care. Paired t-tests were used to compare mean pre and post urinary concentrations of TNF-α and clinical outcomes.

Results

Significantly higher baseline levels of urinary TNF-α were observed in chronic low back pain patients when compared to our reference value (p < 0.001), which were significantly lower after the period of chiropractic treatment (p = 0.03). Moreover, these changes were accompanied by a significant reduction in pain and disability (both p < 0.001). However, levels of urinary TNF-α were not correlated with pain intensity nor disability.

Conclusion

These results suggest that urine could be a good milieu to assess TNF-α changes, with potential clinical implications for the management of chronic low back pain.

Intradiscal injection for the management of low back pain

Low back pain (LBP) is a common clinical problem and a major cause of physical disability, imposing a prominent socioeconomic burden. Intervertebral disc degeneration (IDD) has been considered the main cause of LBP. The current treatments have limited efficacy because they cannot address the underlying degeneration. With an increased understanding of the complex pathological mechanism of IDD, various medications and biological reagents have been used for intradiscal injection for the treatment of LBP. There is increasing clinical evidence showing the benefits of these therapies on symptomatic relief and their potential for disc repair and regeneration by targeting the disrupted pathways underlying the cause of the disease. A brief overview of the potential and limitations for these therapies are provided in this review, based on the recent and available data from clinical trials and systematic reviews. Finally, future perspectives are discussed.

Intervertebral disc therapies for non-specific chronic low back pain: a systematic review and meta-analysis

Objectives

We aim to evaluate the benefits and harms of intervertebral disc therapies (IDTs) in people with non-specific chronic low back pain (NScLBP).

Methods

We conducted a systematic review and meta-analysis of randomized trials of IDTs versus placebo interventions, active comparators or usual care. EMBASE, MEDLINE, CENTRAL and CINHAL databases and conference abstracts were searched from inception to June 2020. Two independent investigators extracted data. The primary outcome was LBP intensity at short term (1 week-3 months), intermediate term (3-6 months) and long term (after 6 months).

Results

Of 18 eligible trials (among 1396 citations), five assessed glucocorticoids (GCs) IDTs and were included in a quantitative synthesis; 13 assessed other products including etanercept (n = 2), tocilizumab (n = 1), methylene blue (n = 2), ozone (n = 2), chymopapaine (n = 1), glycerol (n = 1), stem cells (n = 1), platelet-rich plasma (n = 1) and recombinant human growth and differentiation factor-5 (n = 2), and were included in a narrative synthesis. Standardized mean differences (95% CI) for GC IDTs for LBP intensity and activity limitations were -1.33 (-2.34; -0.32) and -0.76 (-1.85; 0.34) at short term, -2.22 (-5.34; 0.90) and -1.60 (-3.51; 0.32) at intermediate term and -1.11 (-2.91; 0.70) and -0.63 (-1.68; 0.42) at long term, respectively. Odds ratios (95% CI) for serious and minor adverse events with GC IDTs were 1.09 (0.25; 4.65) and 0.97 (0.49; 1.91).

Conclusion

GC IDTs are associated with a reduction in LBP intensity at short term in people with NScLBP. Positive effects are not sustained. IDTs have no effect on activity limitations. Our conclusions are limited by high heterogeneity and a limited methodological quality across studies.

Registration

PROSPERO: CRD42019106336.

Orofacial Neuropathic Pain-Basic Research and Their Clinical Relevancies

Trigeminal nerve injury is known to cause severe persistent pain in the orofacial region. This pain is difficult to diagnose and treat. Recently, many animal studies have reported that rewiring of the peripheral and central nervous systems, non-neuronal cell activation, and up- and down-regulation of various molecules in non-neuronal cells are involved in the development of this pain following trigeminal nerve injury. However, there are many unknown mechanisms underlying the persistent orofacial pain associated with trigeminal nerve injury. In this review, we address recent animal data regarding the involvement of various molecules in the communication of neuronal and non-neuronal cells and examine the possible involvement of ascending pathways in processing pathological orofacial pain. We also address the clinical observations of persistent orofacial pain associated with trigeminal nerve injury and clinical approaches to their diagnosis and treatment.

The Technique of Intradiscal Injection: A Narrative Review

Background

Low back pain (LBP) is one of the most common spine diseases and represents the most frequent cause of absence from work in developed countries. Approximately 40% of chronic LBP is related to discogenic origin. The goal of the study is producing a review of literature to describe analytically the techniques of intradiscal injections.

Methods

PubMed database was searched for clinical studies with the different key terms: “intradiscal”, “injection”, “steroid” “procedures”, “techniques”, “CT”, “MRI”, “fluoroscopy”, “fluoroscopic”, “guidance”, “ozone”, “ultrasound”, “images”. Only studies written in English, French, or Italian in which the intradiscal injection represents the main procedure for the low back discopathy treatment on humans were considered. We excluded the articles that do not mention this procedure; those which indicated that the intradiscal injection had happened accidentally during other treatments; those reporting the patient’s pain was determined by other causes than the discopathy (facet joint syndrome, tumor, spondylodiscitis).

Results

Thirty-one articles dated from 1969 to 2018 met the criteria. The examined population was 6843 subjects, 52.3% male and 47.7% female, with a mean age of 45.9±10.1 years. The techniques are highly variable in terms of procedure: different operators, needle guidance, injection sites, drugs, tilt angle of the needle).

Conclusion

The efficacy and the safety of the intradiscal procedures are not easily comparable due to different types of studies and their limited number. Further studies are needed to standardize the intradiscal injection technique/procedure to improve safety, repeatability and effectiveness, and last but not least to reduce peri- and postoperative care and health-care costs.

Proinflammatory intervertebral disc cell and organ culture models induced by tumor necrosis factor alpha

Inflammation plays an important role in the pathogenesis of intervertebral disc (IVD) degeneration. The proinflammatory cytokine tumor necrosis factor alpha (TNF-α) has shown markedly higher expression in degenerated human disc tissue compared with healthy controls. Anti-inflammatory treatment targeting TNF-α has shown to alleviate discogenic pain in patients with low back pain. Therefore, in vitro and ex vivo inflammatory models utilizing TNF-α provide relevant experimental conditions for drug development in disc degeneration research. The current method article addressed several specific questions related to the model establishment. (a) The effects of bovine and human recombinant TNF-α on bovine nucleus pulposus (NP) cells were compared. (b) The required dose for an inflammatory IVD organ culture model with intradiscal TNF-α injection was studied. (c) The effect of TNF-α blocking at different stages of inflammation was evaluated. Outcomes revealed that bovine and human recombinant TNF-α induced equivalent inflammatory effects in bovine NP cells. A bovine whole IVD inflammatory model was established by intradiscal injection of 100 ng TNF-α/ cm3 disc volume, as indicated by increased nitric oxide, glycosaminoglycan, interleukin 6 (IL-6), and interleukin 8 (IL-8) release in culture media, and upregulation of MMP3, ADAMTS4, IL-8, IL-6, and cyclooxygenase (COX)-2 expression in NP tissue. However, results in human NP cells showed that the time point of anti-inflammatory treatment was crucial to achieve significant effects. Furthermore, anticatabolic therapy in conjunction with TNF-α inhibition would be required to slow down the pathologic cascade of disc degeneration.

Preclinical ex-vivo Testing of Anti-inflammatory Drugs in a Bovine Intervertebral Degenerative Disc Model

Discogenic low back pain (LBP) is a main cause of disability and inflammation is presumed to be a major driver of symptomatic intervertebral disc degeneration (IDD). Anti-inflammatory agents are currently under investigation as they demonstrated to alleviate symptoms in patients having IDD. However, their underlying anti-inflammatory and regenerative activity is poorly explored. The present study sought to investigate the potential of Etanercept and Tofacitinib for maintaining disc homeostasis in a preclinical intervertebral disc (IVD) organ culture model within IVD bioreactors allowing for dynamic loading and nutrient exchange. Bovine caudal IVDs were cultured in a bioreactor system for 4 days to simulate physiological or degenerative conditions: (1) Phy—physiological loading (0.02–0.2 MPa; 0.2 Hz; 2 h/day) and high glucose DMEM medium (4.5 g/L); (2) Deg+Tumor necrosis factor α (TNF-α)—degenerative loading (0.32–0.5 MPa; 5 Hz; 2 h/day) and low glucose DMEM medium (2 g/L), with TNF-α injection. Etanercept was injected intradiscally while Tofacitinib was supplemented into the culture medium. Gene expression in the IVD tissue was measured by RT-qPCR. Release of nitric oxide (NO), interleukin 8 (IL-8) and glycosaminoglycan (GAG) into the IVD conditioned medium were analyzed. Cell viability in the IVD was assessed using lactate dehydrogenase and ethidium homodimer-1 staining. Immunohistochemistry was performed to assess protein expression of IL-1β, IL-6, IL-8, and collagen type II in the IVD tissue. Etanercept and Tofacitinib downregulated the expression of IL-1β, IL-6, IL-8, Matrix metalloproteinase 1 (MMP1), and MMP3 in the nucleus pulposus (NP) tissue and IL-1β, MMP3, Cyclooxygenase-2 (COX2), and Nerve growth factor (NGF) in the annulus fibrosus (AF) tissue. Furthermore, Etanercept significantly reduced the IL-1β positively stained cells in the outer AF and NP regions. Tofacitinib significantly reduced IL-1β and IL-8 positively stained cells in the inner AF region. Both, Etanercept and Tofacitinib reduced the GAG loss to the level under physiological culture condition. Etanercept and Tofacitinib are able to neutralize the proinflammatory and catabolic environment in the IDD organ culture model. However, combined anti-inflammatory and anabolic treatment may be required to constrain accelerated IDD and relieving inflammation-induced back pain.

Correlation of Early Outcomes and Intradiscal Interleukin-6 Expression in Lumbar Fusion Patients

Objective

To determine if there is correlation between intradiscal levels of interleukin-6 (IL-6) and early outcome measures in patients undergoing lumbar fusion for painful disc degeneration.

Methods

Intervertebral disc tissue was separated into annulus fibrosus/nucleus pulposus and cultured separately in vitro in serum-free medium (Opti-MEM). Conditioned media was collected after 48 hours. The concentration of IL-6 was quantified using enzyme-linked immunosorbent assay. Pearson correlation coefficients quantified relationships between IL-6 levels and pre- and postoperative visual analogue scale (VAS) back pain and Oswestry Disability Index (ODI), as well as change in VAS/ODI.

Results

Sixteen discs were harvested from 9 patients undergoing anterior lumbar interbody fusion (mean age, 47.4 years; range, 21–70 years). Mean preoperative and 6-month postoperative VAS were 8.1 and 3.7, respectively. Mean preoperative and postoperative ODI were 56.2 and 25.6, respectively. There were significant positive correlations between IL-6 expression and postoperative VAS (ρ = 0.38, p = 0.048) and ODI (ρ = 0.44, p = 0.02). No significant correlations were found between intradiscal IL-6 expression and preoperative VAS (ρ = -0.12, p = 0.54). Trends were seen associating IL-6 expression and change in VAS/ODI (ρ = -0.35 p = 0.067; ρ = -0.34, p = 0.08, respectively). A trend associated IL-6 and preoperative ODI (ρ = 0.36, p = 0.063).

Conclusion

The direct association between IL-6 expression and VAS/ODI suggests patients with elevated intradiscal cytokine expression may have worse early outcomes than those with lower expression of IL-6 after surgery for symptomatic disc degeneration.

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

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

Multiplex Epigenome Editing of Dorsal Root Ganglion Neuron Receptors Abolishes Redundant Interleukin 6, Tumor Necrosis Factor Alpha, and Interleukin 1β Signaling by the Degenerative Intervertebral Disc

Back pain is the leading cause of disability worldwide and contributes to significant socioeconomic impacts. It has been hypothesized that the degenerative intervertebral disc (IVD) contributes to back pain by sensitizing nociceptive neurons innervating the IVD to stimuli that would not be painful to healthy patients. However, the inflammatory signaling networks mediating this sensitization remain poorly understood. A better understanding of the underlying mechanisms of degenerative IVD-induced changes in nociception is required to improve the understanding and treatment of back pain. Toward these ends, a novel in vitro model was developed to investigate degenerative IVD-induced changes in dorsal root ganglion (DRG) neuron activation by measuring DRG neuron activity following neuron seeding on human degenerative IVD tissue collected from patients undergoing surgical treatment for back pain. Lentiviral clustered regularly interspaced palindromic repeat (CRISPR) epigenome editing vectors were built to downregulate the inflammatory receptors TNFR1, IL1R1, and IL6st in DRG neurons in single- and multiplex. Multiplex CRISPR epigenome editing of inflammatory receptors demonstrated that degenerative IVD tissue drives thermal sensitization through the simultaneous and redundant signaling of interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), and IL-1β. This work elucidates redundant signaling pathways in neuron interactions with the degenerative IVD and suggests the need for multiplex targeting of IL-6, TNF-α, and IL-1β for pain modulation in the degenerative IVD.

Serum biomarkers in people with chronic low back pain and Modic 1 changes: a case-control study

We aimed to compare serum biomarkers of inflammation, redox status and cartilage degradation between chronic low back pain (cLBP) patients with and without Modic 1 changes. We used a convenience sample of patients recruited from a single center, case-control study, conducted in a tertiary care center. From December, 2014 to May, 2016, 2,292 patients were consecutively screened, 34 met inclusion criteria and were prospectively enrolled in the present study. Cases (n = 13) were defined as patients with Modic 1 changes detected on MRI and controls (n = 21) as cLBP patients without (Modic 0). To assess serum biomarkers of inflammation, redox status and cartilage degradation, fasting serum samples were collected in a standardized manner and analyzed by immunoassays and spectrophotometry. Mean (95% CI) age was 44.1 (40.0–48.1) years and mean LBP duration was 72.5 (53.0–91.9) months. Serum biomarkers of inflammation (IL-1β, IL-6, IL-8 and TNF-α), redox status (total thiols, advanced oxidation protein products and carbonyl groups) and cartilage degradation (Coll2-1 and Coll2-1NO₂) did not differ between cLBP patients with and without Modic 1 changes. In summary, we did not find any differences in serum biomarkers between cLBP patients with and without Modic 1 changes. Interpretation is limited by convenience sampling and small sample size.

Neuroinflammation and Central Sensitization in Chronic and Widespread Pain

Chronic pain is maintained in part by central sensitization, a phenomenon of synaptic plasticity, and increased neuronal responsiveness in central pain pathways after painful insults. Accumulating evidence suggests that central sensitization is also driven by neuroinflammation in the peripheral and central nervous system. A characteristic feature of neuroinflammation is the activation of glial cells, such as microglia and astrocytes, in the spinal cord and brain, leading to the release of proinflammatory cytokines and chemokines. Recent studies suggest that central cytokines and chemokines are powerful neuromodulators and play a sufficient role in inducing hyperalgesia and allodynia after central nervous system administration. Sustained increase of cytokines and chemokines in the central nervous system also promotes chronic widespread pain that affects multiple body sites. Thus, neuroinflammation drives widespread chronic pain via central sensitization. We also discuss sex-dependent glial/immune signaling in chronic pain and new therapeutic approaches that control neuroinflammation for the resolution of chronic pain.

Macrophage polarization contributes to local inflammation and structural change in the multifidus muscle after intervertebral disc injury

PURPOSE

Intervertebral disk (IVD) lesion and its subsequent degeneration have a profound effect on the multifidus muscle. The subacute/early chronic phase of multifidus remodeling after IVD lesion has been proposed to be regulated by inflammatory processes. The balance between pro-inflammatory (M1) and anti-inflammatory (M2) macrophages plays an important role in maintaining tissue integrity after injury. The localization, polarization of macrophage subtypes and their mediation of the pro-inflammatory cytokine tumor necrosis factor (TNF) are unknown in paraspinal muscles during IVD degeneration. A sheep model of IVD degeneration was used to investigate the role of macrophages and TNF in the structural alterations that occur within the multifidus muscle.

METHODS

Anterolateral lesions were induced at L3-4 IVD in sheep. Multifidus muscle tissue at L4 was harvested 3 and 6 months after lesion and used for immunofluorescence assays to examine total macrophage number, macrophage polarization between M1 and M2, and to assess the localization of TNF expression in muscle, adipose and connective tissues from injured and naïve control animals.

RESULTS

A greater proportion of M1 macrophages is present in muscle at both 3 and 6 months after IVD lesion, and adipose tissue at 6 months. Total number of macrophages is unchanged. At 6 months, expression of TNF is increased in adipose and connective tissue and the proportion of TNF expressed by M1 macrophages is increased.

CONCLUSIONS

These data support the proposal that macrophages and TNF (pro-inflammatory cytokine) play an active role in the subacute/early chronic phase of remodeling in muscle, adipose and connective tissues of the multifidus during IVD degeneration. This presents a novel target for treatment. These slides can be retrieved under Electronic Supplementary Material.

Inhibiting tumor necrosis factor-alpha at time of induced intervertebral disc injury limits long-term pain and degeneration in a rat model

Background

Painful intervertebral disc (IVD) degeneration has tremendous societal costs and few effective therapies. Intradiscal tumor necrosis factor‐alpha (TNFα) is commonly associated with low back pain, but the direct relationship remains unclear.

Purpose

Treatment strategies for low back pain require improved understanding of the complex relationships between pain, intradiscal pro‐inflammatory cytokines, and structural IVD degeneration. A rat in vivo lumbar IVD puncture model was used to 1) determine the role of TNFα in initiating painful IVD degeneration, and 2) identify statistical relationships between painful behavior, IVD degeneration, and intradiscal pro‐inflammatory cytokine expression.

Methods

Lumbar IVDs were punctured anteriorly and injected with TNFα, anti‐TNFα, or saline and compared with sham and naive controls. Hindpaw mechanical hyperalgesia was assayed weekly to determine pain over time. 6‐weeks post‐surgery, animals were sacrificed, and IVD degeneration, IVD height, and intradiscal TNFα and interleukin‐1 beta (IL‐1β) expressions were assayed.

Results

Intradiscal TNFα injection increased pain and IVD degeneration whereas anti‐TNFα alleviated pain to sham level. Multivariate step‐wise linear regression identified pain threshold was predicted by IVD degeneration and intradiscal TNFα expression. Pain threshold was also linearly associated with IVD height loss and IL‐1β.

Discussion

The significant associations between IVD degeneration, height loss, inflammation, and painful behavior highlight the multifactorial nature of painful IVD degeneration and the challenges to diagnose and treat a specific underlying factor. We concluded that TNFα is an initiator of painful IVD degeneration and its early inhibition can mitigate pain and degeneration. Intradiscal TNFα inhibition following IVD injury may warrant investigation for its potential to alter downstream painful IVD degeneration processes.

Active discopathy: a clinical reality

In the late 1980s, the description by Modic and colleagues of elementary discovertebral changes detected on MRI (Modic classification) suggested for the first time a possible correlation between anatomical and clinical features in a subgroup of patients with non-specific chronic low back pain. Degenerative disc disease is frequent and usually asymptomatic, but Modic 1 changes in the vertebral endplates adjacent to a degenerated disc are associated with inflammatory-like chronic low back pain and low-grade local and systemic inflammation, which led to the concept of ‘active discopathy’. Active discopathy shares some similarities with acute flares of peripheral osteoarthritis. Likewise, what triggers disc activation and how it self-limits remain unknown. A better understanding of mechanisms underlying disc activation and its self-limitation is of clinical relevance because it may enable the design of more targeted pharmacological and non-pharmacological interventions for the subgroup of patients with chronic low back pain and active discopathy. Here, we narratively review current disc-centred biomechanical and biochemical hypotheses of disc activation and discuss evidence of interactions with adverse personal and environmental factors.

Sensory nerve ingrowth, cytokines, and instability of discogenic low back pain: A review

Introduction

Many patients suffer from discogenic low back pain. However, the mechanisms, diagnosistic strategy, and treatment of discogenic low back pain all remain controversial. The purpose of this paper was to review the pathological mechanisms of discogenic low back pain.

Methods

Many authors have investigated the pathological mechanisms of discogenic low back pain using animal models and examining human patients. Central to most investigations is understanding the innervation and instabilities of diseased intervertebral discs and the role of inflammatory mediators. We discuss three pathological mechanisms of discogenic low back pain: innervation, inflammation, and mechanical hypermobility of the intervertebral disc.

Results

Sensory nerve fibers include C-fibers and A delta-fibers, which relay pain signals from the innervated outer layers of the intervertebral disc under normal conditions. However, ingrowth of these sensory nerve fibers into the inner layers of intervertebral disc occurs under disease conditions. Levels of neurotrophic factors and some cytokines are significantly higher in diseased discs than in normal discs. Stablization of the segmental hypermobility, which can be induced by intervertebral disc degeneration, suppresses inflammation and prevents sensitization of sensory nerve fibers innervating the disc.

Conclusions

Pathological mechanisms of discogenic low back pain include sensory nerve ingrowth into inner layers of the intervertebral disc, upregulation of neurotrophic factors and cytokines, and instability. Inhibition of these mechanisms is important in the treatment of discogenic low back pain.

Sarcopenia in elderly patients with chronic low back pain

Objectives

The prevalence of chronic low back pain (CLBP) increases with age and several mechanisms are involved in the development of CLBP, including osteoporosis; however, no associations with sarcopenia have yet been identified.

Methods

In total, 100 patients with CLBP and 560 patients without CLBP (nCLBP) aged over 65 years were studied. Skeletal muscle mass index (SMI) and percentage of body fat were evaluated using whole-body dual-energy X-ray absorptiometry. Sarcopenia was diagnosed when the relative SMI was more than 2 standard deviations below the mean in young adults. Thus, the cutoff value for sarcopenia was defined according to Sanada's Japanese population data. Paraspinal muscle cross-sectional areas of the lumbar multifidus and the erector spinae muscles were calculated using magnetic resonance imaging.

Results

Forty patients (40.0%) from the CLBP group and 149 (26.6%) from the nCLBP group met the criteria of sarcopenia. SMI was significantly lower and the body fat ratio was significantly higher in the CLBP group compared with the nCLBP group. Sarcopenic obesity was significantly observed in the CLBP group. Lumbar multifidus and the erector spinae muscle cross sectional area were significantly lower in the CLBP group.

Conclusions

Elderly patients with CLBP have significantly lower skeletal muscle mass, and age-related mechanisms in sarcopenia are considered to be associated with chronic pain. Therapeutic procedures that are used to treat elderly aging muscle, including muscle strengthening and performance training, can possibly be a treatment for or used to prevent elderly CLBP.

Changes and significance of inflammatory cytokines in a rat model of cervical spondylosis

The aim of the present study was to dynamically observe and discuss the significance of inflammatory cytokines in cervical degenerative disease induced by unbalanced dynamic and static forces in rats. A total of 60 Sprague Dawley rats were randomized into test (n=45) and control (n=15) groups, which were randomly subdivided into three groups corresponding to assessment at one, three and six months post-operation. The test group included 10, 15 and 20 rats at the corresponding post-operative stage and the control group had five rats at each time-point. By excising cervicodorsal muscles and ligaments, an unbalanced dynamic and static rat model was established in the test group. At one, three and six-months post-operation, venous serum of test and control group rats was collected and inflammatory cytokines in the serum of all rats were quantitatively determined by ELISA. The results revealed that compared with the control group, the interleukin (IL)-1β, IL-10 and tumor necrosis factor-α levels in the test group were significantly increased at one and three months (P<0.05, <0.01 or <0.001), and that IL-12 was significantly increased at three months (P<0.05). However, transforming growth factor-β1 increased at one month but was significantly decreased at three months (P<0.01). IL-6 did not change significantly throughout the observation period (P>0.05). In conclusion, cervical vertebral stability may be accompanied with changes of inflammatory cytokines.

Inhibiting Vascular Endothelial Growth Factor in Injured Intervertebral Discs Attenuates Pain-Related Neuropeptide Expression in Dorsal Root Ganglia in Rats

STUDY DESIGN

An experimental animal study.

PURPOSE

To evaluate effects of anti-vascular endothelial growth factor (VEGF) on the content and distribution of the calcitonin gene-related peptide (CGRP) in the dorsal ganglia in a rat model.

OVERVIEW OF LITERATURE

Increased expression of VEGF in degenerative disc disease increases the levels of inflammatory cytokines and nerve ingrowth into the damaged discs. In animal models, increased levels of VEGF can persist for up to 2 weeks after an injury.

METHODS

Through abdominal surgery, the dorsal root ganglia (DRG) innervating L5/L6 intervertebral disc were labeled (FluoroGold neurotracer) in 24, 8-week old Sprague Dawley rats. The rats were randomly allocated to three groups of eight rats each. The anti-VEGF group underwent L5/6 intervertebral disc puncture using a 26-gauge needle, intradiscal injection of 33.3 µg of the pegaptanib sodium, a VEGF165 aptamer. The control-puncture group underwent disc puncture and intradiscal injection of 10 µL saline solution, and the sham-surgery group underwent labeling but no disc puncture. Two rats in each group were sacrificed on postoperative days 1, 7, 14, and 28 after surgery. L1-L6 DRGs were harvested, sectioned, and immunostained to detect the content and distribution of CGRP.

RESULTS

Compared with the control, the percentage of CGRP-positive cells was lower in the anti-VEGF group (p<0.05; 40.6% and 58.1% on postoperative day 1, 44.3% and 55.4% on day 7, and 42.4% and 59.3% on day 14). The percentage was higher in the control group compared with that of the sham group (p<0.05; sham group, 34.1%, 40.7%, and 33.7% on postoperative days 1, 7, and 14, respectively).

CONCLUSIONS

Decreasing CGRP-positive cells using anti-VEGF therapy provides fundamental evidence for a possible therapeutic role of anti-VEGF in patients with discogenic lower back pain.

Dose Optimization for Single Intradiscal Administration of the Tumor Necrosis Factor-α Inhibitor, Etanercept, in Rat Disc Injury Models

Study Design

Experimental animal study.

Purpose

We aimed to determine the optimal dose of a single direct injection of the tumor necrosis factor (TNF)-α inhibitor, etanercept, by using the rat model of degenerative intervertebral disc from injury.

Overview of Literature

The pain-related peptide expression was suppressed in the etanercept (100 µg and 1,000 µg)-administered groups in a dose-dependent manner.

Methods

The neurotracer FluoroGold (FG) was applied to the surfaces of L4/5 discs to label their innervating dorsal root ganglion (DRG) neurons (n=50). Ten rats were included in the nonpunctured disc sham surgery control group, whereas the other 40 were included in the experimental group in which intervertebral discs were punctured with a 23-gauge needle. Saline or etanercept (10 µg, 100 µg, or 1,000 µg) was injected into the punctured discs (n=10 for each treatment). After 14 days of surgery, DRGs from L1 to L6 were harvested, sectioned, and immunostained for calcitonin gene-related peptide (CGRP). The proportion of FG-labeled CGRP-immunoreactive DRG neurons was evaluated in all the groups.

Results

There were no significant differences between the puncture+saline group and the puncture+10-µg etanercept group (p >0.05). However, a significant decrease in the percentage of FG and CGRP double-positive cells in FG-positive cells was observed in the etanercept (100 µg and 1,000 µg)-administered groups in a dose-dependent manner (p <0.05).

Conclusions

When a low dose of the TNF-α inhibitor (10 µg of etanercept) was directly administered to the rat intervertebral disc in the rat model of degenerative intervertebral disc from injury, no suppressive effect on the pain-related peptide expression was observed. However, when a higher dose of etanercept (100 µg and 1,000 µg) was administered, the pain-related peptide expression was suppressed in a dose-dependent manner.

Prevalence and Location of Neuropathic Pain in Lumbar Spinal Disorders: Analysis of 1804 Consecutive Patients With Primary Lower Back Pain

STUDY DESIGN

A cross-sectional study of 1804 consecutive patients.

OBJECTIVE

The aim of this study was to investigate the prevalence of pathological pain and its distribution features in patients with chronic lumbar spinal disorders.

SUMMARY OF BACKGROUND DATA

Clinical spinal disorders can involve pathological neuropathic pain (NeP) as well as physiological nociceptive pain (NocP), as they have varied pathology, including spinal cord injury, stenosis, and compression. A study conducted by the Japanese Society for Spine Surgery and Related Research (JSSR) has determined a prevalence of 29.4% for NeP in patients with lumbar spinal disorder. However, the data did not include information on pain location.

METHODS

Patients aged 20 to 79 years with chronic lower back pain (≥3 months, visual analog scale score ≥30) were recruited from 137 JSSR-related institutions. Patient data included an NeP screening questionnaire score and pain location (lower back, buttock, and legs). The association between the pain pathology and its location was analyzed statistically using the unpaired t test and Chi-square test followed by Fisher test. P < 0.05 was considered significant.

RESULTS

Low back pain subjects showed 31.9% of NeP prevalence, and the pain distribution showed [NocP(%)/NeP(%)] low back pain only cases: 44/22, while low back pain with leg pain cases showed a prevalence of 56/78. This indicates that low back pain alone can significantly induce NocP rather than NeP (P < 0.01). Buttock pain was revealed to significantly induce both lower back pain and leg pain with NeP properties (P < 0.01). Leg pain was revealed to be predominantly neuropathic, especially when it included peripheral pain (P < 0.01).

CONCLUSION

Low back pain with no buttock pain induces NocP rather than NeP. Buttock pain is significantly associated with NeP prevalence whether or not leg pain exists. Leg pain can increase the prevalence of NeP, especially when it contains a peripheral element.

LEVEL OF EVIDENCE

3.

Perispinal Delivery of CNS Drugs

Perispinal injection is a novel emerging method of drug delivery to the central nervous system (CNS). Physiological barriers prevent macromolecules from efficiently penetrating into the CNS after systemic administration. Perispinal injection is designed to use the cerebrospinal venous system (CSVS) to enhance delivery of drugs to the CNS. It delivers a substance into the anatomic area posterior to the ligamentum flavum, an anatomic region drained by the external vertebral venous plexus (EVVP), a division of the CSVS. Blood within the EVVP communicates with the deeper venous plexuses of the CSVS. The anatomical basis for this method originates in the detailed studies of the CSVS published in 1819 by the French anatomist Gilbert Breschet. By the turn of the century, Breschet's findings were nearly forgotten, until rediscovered by American anatomist Oscar Batson in 1940. Batson confirmed the unique, linear, bidirectional and retrograde flow of blood between the spinal and cerebral divisions of the CSVS, made possible by the absence of venous valves. Recently, additional supporting evidence was discovered in the publications of American neurologist Corning. Analysis suggests that Corning's famous first use of cocaine for spinal anesthesia in 1885 was in fact based on Breschet's anatomical findings, and accomplished by perispinal injection. The therapeutic potential of perispinal injection for CNS disorders is highlighted by the rapid neurological improvement in patients with otherwise intractable neuroinflammatory disorders that may ensue following perispinal etanercept administration. Perispinal delivery merits intense investigation as a new method of enhanced delivery of macromolecules to the CNS and related structures.