Smoking and BMI mediate the causal effect of education on lower back pain: observational and Mendelian randomization analyses.

Objective: Low back pain (LBP) has been associated with education in previous observational studies, but the causality remains unclear. This study aims to assess the impact of education on LBP and to explore mediation by multiple lifestyle factors. Design: Univariable Mendelian randomization (MR) was performed to examine the overall effect of education on LBP. Subsequently, multivariable MR was conducted to assess both the direct effect of education on LBP and the influence of potential mediators. Indirect effects were estimated using either the coefficient product method or the difference method, and the proportion of mediation was calculated by dividing the indirect effect by the total effect. The observational study utilized data from the NHANES database collected between 1999 and 2004, and included 15,580 participants aged 20 years and above. Results: Increasing education by 4.2 years leads to a 48% reduction in the risk of LBP (OR=0.52; 95% CI: 0.46 to 0.59). Compared to individuals with less than a high school education, those with education beyond high school have a 28% lower risk of LBP (OR=0.72; 95% CI: 0.63 to 0.83). In the MR study, smoking accounts for 12.8% (95% CI: 1.04% to 20.8%) of the total effect, while BMI accounts for 5.9% (95% CI: 2.99% to 8.55%). The combined mediation effect of smoking and BMI is 27.6% (95% CI: 23.99% to 32.7%). In the NHANES study, only smoking exhibits a mediating effect, accounting for 34.3% (95% CI: 21.07% to 41.65%) of the effect, while BMI does not demonstrate a mediating role. Conclusions: Higher levels of education provide a protective effect against the risk of LBP. Additionally, implementing interventions to reduce smoking and promote weight loss among individuals with lower levels of education can also decrease this risk.

The Genetic Causal Association between Educational Attainment and Risk of 12 Common Musculoskeletal Disorders: A Two-Sample Mendelian Randomization.

OBJECTIVE: In numerous observational studies, there has been an indication that educational attainment (EA) can impact the intensity of pain and disability resulting from chronic musculoskeletal disorders. Nonetheless, the association observed in these studies is not entirely conclusive. The aim of this study was to investigate the genetic causal relationship between educational attainment and 12 musculoskeletal disorders using Mendelian randomization (MR). METHODS: The meta-analysis of genome-wide association studies (GWAS) identified 3952 single-nucleotide polymorphisms (SNPs) associated with educational attainment (EA) from the Social Science Genetic Association Consortium (SSGAC). Genetic data for 12 musculoskeletal disorders, including osteonecrosis, osteoporosis, osteomyelitis, low back pain, gout, spinal stenosis, rheumatoid arthritis, meniscus derangement, rotator cuff syndrome, ankylosing spondylitis, cervicobrachial syndrome, and lateral epicondylitis, were obtained from the FinnGen consortium. We conducted a two-sample Mendelian randomization analysis to examine the causal effect of EA on the risk of these musculoskeletal disorders using the TwoSampleMR package in R. RESULTS: Based on the inverse-variance weighted (IVW) method, we found that a genetically predicted per standard deviation (SD) increase in EA was inversely associated with low back pain [odds ratio (OR) 0.46, 95% confidence interval (Cl) 0.51-0.61, p < 0.001], spinal stenosis (OR 0.62, 95% Cl 0.54-0.71, p < 0.001), rheumatoid arthritis (OR 0.65, 95% Cl 0.55-0.76, p < 0.001), meniscus derangement (OR 0.73, 95% Cl 0.65-0.82, p < 0.001), rotator cuff syndrome (OR 0.55, 95% Cl 0.49-0.61, p < 0.001), cervicobrachial syndrome (OR 0.50, 95% Cl 0.42-0.60, p < 0.001), and lateral epicondylitis (OR 0.30, 95% Cl 0.24-0.37, p < 0.001). There was no causal association between EA and osteonecrosis (OR 1.11, 95% CI 0.76-1.72, p = 0.60), osteoporosis (OR 0.91, 95% CI 0.65-1.27, p = 0.59), or osteomyelitis (OR 0.90, 95% CI 0.75-1.01, p = 0.22). Genetic predisposition to EA had a suggestive causal association with gout (OR 0.80, 95% CI 0.68-0.95, p = 0.01) and ankylosing spondylitis (OR 0.64, 95% CI 0.45-0.91, p = 0.01) after Bonferroni correction. None of the analyses revealed any horizontal pleiotropy or heterogeneity. CONCLUSION: In our investigation, we have uncovered evidence supporting a causal relationship between low level of EA and the incidence of certain musculoskeletal disorders. In the future, it is imperative to ascertain risk factors such as lifestyle patterns linked with EA to uncover the underlying causal relationship and offer informed interventions for individuals.

Assessing the causal relationship between genetically determined inflammatory biomarkers and low back pain risk: a bidirectional two-sample Mendelian randomization study.

Background: Observational studies have suggested an association between inflammatory markers and low back pain (LBP), but the causal relationship between these factors remains uncertain. Methods: We conducted a bidirectional two-sample Mendelian randomization analysis (MR) study to investigate whether there is a causal relationship between inflammatory markers and low back pain. We obtained genetic data for CRP, along with its upstream inflammatory markers IL-6, IL-8, and IL-10, as well as low back pain from publicly available genome-wide association studies (GWAS). We applied several MR methods, including inverse variance weighting, weighted median, MR-Egger, Wald Ratio, and MR-PRESSO, to test for causal relationships. Sensitivity analyses were also conducted to assess the robustness of the results. Results: Our analyses utilizing the Inverse Variance Weighted (IVW) method, the MR-Egger method, and the weighted median method indicated that IL-6 may be associated with an increased risk of LBP (Effect Size: -0.009, 95% Confidence Interval: -0.013-0.006, p = 9.16e-08); however, in the reverse direction, there was no significant causal effect of LBP on inflammatory markers. Conclusion: Our study used a Mendelian randomization approach and found that elevated IL-6 levels may reduce the risk of LBP.

Causal relationship between leisure sedentary behaviors and low back pain risk: a Mendelian randomization study.

PURPOSE: This study aims to assess the causal associations of leisure sedentary behaviors with low back pain (LBP). METHODS: A Mendelian randomization (MR) study was carried out utilizing genetic instruments to determine whether leisure sedentary behaviors (including leisure television watching, leisure computer use, and driving) are causally associated with LBP. All instrumental variables were selected from publicly available genetic summary data. The inverse variance weighted (IVW) was used as the main method to conduct univariable MR analyses. Further sensitivity analyses were utilized to test the stability of the results. Moreover, multivariable MR was performed to evaluate the independent causal relationship between leisure sedentary behaviors and LBP when body mass index (BMI), waist circumference, smoking initiation, and vigorous physical activity were taken into account. RESULTS: The MR analyses showed evidence that television watching increased the risk for LBP (OR: 1.97, 95% CI 1.45, 2.66; P = 1.19 × 10-5). Genetically determined computer use is causally associated with a decreased risk of LBP (OR: 0.53, 95% CI 0.41, 0.68; P = 4.79 × 10-7). However, no evidence was found of a causal relationship between driving and LBP (OR: 2.27, 95% CI 0.75, 6.81; P = 0.145). After adjusting for BMI, waist circumference, smoking initiation, and vigorous physical activity, only television maintained its causal effect on LBP. CONCLUSIONS: This study indicated that genetically predicted television watching was a risk factor for LBP independent of BMI, waist circumference, smoking initiation, and vigorous physical activity. This finding may be helpful for the diagnosis and management of LBP.

Network Pharmacology-Based Dissection of the Mechanism of Drynariae Rhizoma for Low Back Pain.

Objective: To explain the potential mechanisms of Drynariae Rhizoma (DR) in the treatment of low back pain (LBP). Design: Network pharmacology was used to reveal the potential mechanisms including collecting the active ingredients of DR, analyzing the common gene targets of LBP and DR, constructing protein-protein interaction (PPI) network, collecting protein classification, performing Gene Ontology (GO) functional analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and verifying significant gene targets. Results: 234 different gene targets and 18 active compounds altogether were obtained. AKT1, VEGFA, and HIF1A were deemed to be major gene targets based on the degree values. According to GO analysis, steroid metabolic process involved 42 (18.10%) potential therapeutic LBP targets, neuronal cell body involved 24 (10.30%) potential therapeutic LBP targets, and protein serine/threonine kinase activity involved 28 (12.02%) potential therapeutic LBP targets in biological process (BP), cellular component (CC), and molecular function (MF), respectively. According to KEGG and pathway interaction analyses, the PI3K-Akt signaling pathway involved 34 (15.89%) potential therapeutic LBP targets, and PI3K-Akt signaling pathway played a significant role in the treatment of LBP. The mRNA expression levels of AKT1 and HIF1A were upregulated in healthy nucleus pulposus (NP) tissue than in degenerative NP tissue. In contrast, the mRNA expression level of VEGFA was downregulated in healthy NP tissue than in degenerative NP tissue. Conclusions: In this study, we identified a potential relationship between LBP and DR in this work, as well as a synergistic mechanism of DR in the treatment of LBP, which serves as a benchmark for further in vivo and in vitro research.

Association between single-nucleotide polymorphism rs145497186 related to NDUFV2 and lumbar disc degeneration: a pilot case-control study.

OBJECTIVE: The association between the single-nucleotide polymorphisms (SNPs) rs28742109, rs12955018, rs987850, rs8093805, rs12965084 and rs145497186 related to gene named NADH dehydrogenase [ubiquinone] flavoprotein 2 (NDUFV2) and lumbar disc degeneration (LDD) was preliminary investigated in a small sample size. METHODS: A total of 46 patients with LDD and 45 controls were recruited at Qilu Hospital of Shandong University, and each participant provided 5 mL peripheral venous blood. NA was extracted from the blood of each participant for further genotyping. The frequency of different genotypes in the case group and control group was determined, and analysis of the risk of LDD associated with different SNP genotypes was performed. The visual analogue scale (VAS) scores of the patients' degree of chronic low back pain were calculated, and the relationship between VAS scores and SNPs was analysed. RESULTS: After excluding the influence of sex, age, height, and weight on LDD, a significant association between SNP rs145497186 related to NDUFV2 and LDD persisted (P = 0.006). Simultaneously, rs145497186 was found to be associated with chronic low back pain in LDD populations. CONCLUSION: NDUFV2 rs145497186 SNP could be associated with susceptibility to LDD and the degree of chronic low back pain.

Smoking, alcohol and coffee consumption and risk of low back pain: a Mendelian randomization study.

PURPOSE: Low back pain (LBP) is a common health problem in the global population. This study aims to assess whether smoking initiation, alcohol consumption, and coffee consumption are causally with an increased risk of LBP. METHODS: A two-sample Mendelian Randomization (MR) study was designed, based on summary-level data from the largest published genome-wide association studies. Single nucleotide polymorphisms with genome-wide significance level (P < 5.0 × 10-8) were selected as instrumental variables for each exposure. Standard inverse-variance weighted (IVW) method was used as the primary statistical method. The weighted median, MR-Egger regression, and MR-PRESSO methods, which relax some IV assumptions, were used for sensitivity analysis. RESULTS: Genetically predicted smoking initiation was causally associated with higher odds of LBP. The pooled OR of LBP using IVW method was 1.36 (95%CI 1.22 1.52; P = 6.0 × 10-8) for one SD increase in the prevalence of smoking initiation, which was supported by the weighted median method (OR: 1.41, 95%CI 1.22, 1.64; P = 5.7 × 10-6). Sensitivity analysis confirmed the robustness of pooled OR of LBP. There was no evidence to suggest a causal effect of alcohol and coffee consumption on LBP. The pooled ORs of LBP were 1.36 (95%CI 0.94, 1.97; P = 0.10) for alcohol consumption and 1.00 (95%CI 0.99, 1.00; P = 0.17) for coffee consumption, respectively. CONCLUSION: Smoking is casually associated with an increased risk of LBP. Smoking control should be recommended in LBP patients to avoid worsening the disease. The safety of LBP with moderate alcohol and coffee consumption merits more study.

Epigenome-wide DNA methylation profiling of conditioned pain modulation in individuals with non-specific chronic low back pain.

BACKGROUND: The pathoanatomic cause of chronic low back pain (cLBP) cannot be identified for up to 90% of individuals. However, dysfunctional processing of endogenous nociceptive input, measured as conditioned pain modulation (CPM), has been associated with cLBP and may involve changes in neuronal gene expression. Epigenetic-induced changes such as DNA methylation (DNAm) have been associated with cLBP. METHODS: In the present study, the relationship between CPM and DNAm changes in a sample of community-dwelling adults with nonspecific cLBP (n = 48) and pain-free controls (PFC; n = 50) was examined using reduced representation bisulfite sequencing. Gene ontology (GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were applied to identify key pathways involved in efficient versus deficient CPM. RESULTS: Based on CPM efficiency, we identified 6006 and 18,305 differentially methylated CpG sites (DMCs) with q values < 0.01 among individuals with cLBP and PFCs, respectively. Most of the DMCs were hypomethylated and annotated to genes of relevance to pain, including OPRM1, ADRB2, CACNA2D3, GNA12, LPL, NAXD, and ASPHD1. In both cLBP and PFC groups, the DMCs annotated genes enriched many GO terms relevant to pain processing, including transcription regulation by RNA polymerase II, nervous system development, generation of neurons, neuron differentiation, and neurogenesis. Both groups also enriched the pathways involved in Rap1-signaling, cancer, and dopaminergic neurogenesis. However, MAPK-Ras signaling pathways were enriched in the cLBP, not the PFC group. CONCLUSIONS: This is the first study to investigate the genome-scale DNA methylation profiles of CPM phenotype in adults with cLBP and PFCs. Based on CPM efficiency, fewer DMC enrichment pathways were unique to the cLBP than the PFCs group. Our results suggest that epigenetically induced modification of neuronal development/differentiation pathways may affect CPM efficiency, suggesting novel potential therapeutic targets for central sensitization. However, CPM efficiency and the experience of nonspecific cLBP may be independent. Further mechanistic studies are required to confirm the relationship between CPM, central sensitization, and nonspecific cLBP.

Association Between Family History of Surgically Treated Low Back Pain and Adolescent Low Back Pain.

STUDY DESIGN: Cross-sectional. OBJECTIVE: To study the associations between a family history of surgically treated low back pain (LBP) and adolescent LBP. SUMMARY OF BACKGROUND DATA: A family history of LBP is related to adolescent LBP, but whether a family history of back surgery is relevant to adolescent LBP is not known. METHODS: A subpopulation of the Northern Finland Birth Cohort 1986 was contacted when they were aged between 18 and 19years. The postal questionnaire asked the participants to report their LBP and a relative's (mother, father, sibling) LBP and back surgery, and to provide data on potential covariates. The association between a family history of LBP ("no family history of LBP," "family history of LBP but no surgery," and "family history of LBP and surgery") and adolescent LBP (no LBP, occasional LBP, and frequent LBP) were evaluated using logistic regression analysis with odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for sex, smoking, and psychological distress. RESULTS: Of the 1374 adolescents in the study, 33% reported occasional LBP and 9% frequent LBP. Both the "family history of LBP but no surgery" and "family history of LBP and surgery" categories were associated with frequent LBP (adjusted OR [aOR] 2.09, 95% CI 1.38-3.16; aOR 2.23, 95% CI 1.02-4.90, respectively). Occasional LBP was associated with the "family history of LBP and surgery" category. A subgroup analysis of adolescents with a family history of LBP found no statistically significant associations between family history of back surgery and adolescent LBP. CONCLUSION: Our findings suggest that adolescents who report a family history of LBP have higher odds of frequent LBP irrespectively of a family history of back surgery.Level of evidence: 4.

Differentially Expressed Circular RNAs in Degenerative Diseases Related to Low Back Pain: Potential of Circular RNAs as Biomarkers.

Low back pain (LBP) is a major cause of disability worldwide. Nevertheless, given the complex pathophysiology of LBP, its etiological diagnosis remains a challenging process. Thus, identifying appropriate biomarkers and/or therapeutic targets is crucial for LBP research. Recently, circular RNAs (circRNAs) which are both abundant and sphysiologically stable have received a great deal of attention as potential molecular biomarkers. This is part because they can serve as microRNA (miRNA) sponges, inhibit normal miRNA activity. Indeed, it has been reported that circulating and/or tissue-specific circRNAs can be used for diagnosing multiple human diseases, including cancers, neurological diseases, and inflammatory diseases. Since 2015, research on circRNAs involved in LBP-related diseases has been a very active endeavor. Moreover, specific roles for some of the differentially expressed circRNAs have been demonstrated. Thus, the involvement of circRNAs in LBP-related diseases suggests that some of the dysregulated ones may have the potential to serve as therapeutic targets and/or diagnostic biomarkers. This review summarizes the current progress on differentially expressed circRNAs in diseases related to LBP.

Correlation between gene expression and MRI STIR signals in patients with chronic low back pain and Modic changes indicates immune involvement.

Disability and distress caused by chronic low back pain (LBP) lacking clear pathoanatomical explanations cause huge problems both for patients and society. A subgroup of patients has Modic changes (MC), identifiable by MRI as vertebral bone marrow lesions. The cause of such changes and their relationship to pain are not yet understood. We explored the pathobiology of these lesions using profiling of gene expression in blood, coupled with an edema-sensitive MRI technique known as short tau inversion recovery (STIR) imaging. STIR images and total RNA from blood were collected from 96 patients with chronic LBP and MC type I, the most inflammatory MC state. We found the expression of 37 genes significantly associated with STIR signal volume, ten genes with edema abundancy (a constructed combination of STIR signal volume, height, and intensity), and one gene with expression levels significantly associated with maximum STIR signal intensity. Gene sets related to interferon signaling, mitochondrial metabolism and defense response to virus were identified as significantly enriched among the upregulated genes in all three analyses. Our results point to inflammation and immunological defense as important players in MC biology in patients with chronic LBP.

Identification of significant gene biomarkers of low back pain caused by changes in the osmotic pressure of nucleus pulposus cells.

The incidence of intervertebral disc (IVD) degeneration disease, caused by changes in the osmotic pressure of nucleus pulposus (NP) cells, increases with age. In general, low back pain is associated with IVD degeneration. However, the mechanism and molecular target of low back pain have not been elucidated, and there are no data suggesting specific biomarkers of low back pain. Therefore, the research aims to identify and verify the significant gene biomarkers of low back pain. The differentially expressed genes (DEGs) were screened in the Gene Expression Omnibus (GEO) database, and the identification and analysis of significant gene biomarkers were also performed with various bioinformatics programs. A total of 120 patients with low back pain were recruited. Before surgery, the degree of pain was measured by the numeric rating scale (NRS), which enables comparison of the pain scores from individuals. After surgery, IVD tissues were obtained, and NP cells were isolated. The NP cells were cultured in two various osmotic media, including iso-osmotic media (293 mOsm/kg H2O) to account for the morbid environment of NP cells in IVD degeneration disease and hyper-osmotic media (450 mOsm/kg H2O) to account for the normal condition of NP cells in healthy individuals. The relative mRNA expression levels of CCL5, OPRL1, CXCL13, and SST were measured by quantitative real-time PCR in the in vitro analysis of the osmotic pressure experiments. Finally, correlation analysis and a neural network module were employed to explore the linkage between significant gene biomarkers and pain. A total of 371 DEGs were identified, including 128 downregulated genes and 243 upregulated genes. Furthermore, the four genes (CCL5, OPRL1, SST, and CXCL13) were identified as significant gene biomarkers of low back pain (P < 0.001) based on univariate linear regression, and CCL5 (odds ratio, 34.667; P = 0.003) and OPRL1 (odds ratio, 19.875; P < 0.001) were significantly related to low back pain through multivariate logistic regression. The expression of CCL5 and OPRL1 might be correlated with low back pain in patients with IVD degeneration disease caused by changes in the osmotic pressure of NP cells.

Absence of VEGFR-1/Flt-1 signaling pathway in mice results in insensitivity to discogenic low back pain in an established disc injury mouse model.

Although degenerative disc disease (DDD) and related low back pain (LBP) are growing public health problems, the underlying disease mechanisms remain unclear. An increase in the vascular endothelial growth factor (VEGF) levels in DDD has been reported. This study aimed to examine the role of VEGF receptors (VEGFRs) in DDD, using a mouse model of DDD. Progressive DDD was induced by anterior stabbing of lumbar intervertebral discs in wild type (WT) and VEGFR-1 tyrosine-kinase deficient mice (vegfr-1TK-/- ). Pain assessments were performed weekly for 12 weeks. Histological and immunohistochemical assessments were made for discs, dorsal root ganglions, and spinal cord. Both vegfr-1TK-/- and WT mice presented with similar pathological changes in discs with an increased expression of inflammatory cytokines and matrix-degrading enzymes. Despite the similar pathological patterns, vegfr-1TK-/- mice showed insensitivity to pain compared with WT mice. This insensitivity to discogenic pain was related to lower levels of pain factors in the discs and peripheral sensory neurons and lower spinal glial activation in the vegfr-1TK- /- mice than in the WT mice. Exogenous stimulation of bovine disc cells with VEGF increased inflammatory and cartilage degrading enzyme. Silencing vegfr-1 by small-interfering-RNA decreased VEGF-induced expression of pain markers, while silencing vegfr-2 decreased VEGF-induced expression of inflammatory and metabolic markers without changing pain markers. This suggests the involvement of VEGFR-1 signaling specifically in pain transmission. Collectively, our results indicate that the VEGF signaling is involved in DDD. Particularly, VEGFR-1 is critical for discogenic LBP transmission independent of the degree of disc pathology.

Persistent lumbar radicular and low back pain; impact of genetic variability versus emotional distress.

OBJECTIVE: Earlier studies documenting the effect of candidate genes on recovery have seldom taken into consideration the impact of emotional distress. Thus, we aimed to assess the modifying effect of emotional distress on genetic variability as a predictor for pain recovery in lumbar radicular (LRP) and low back pain (LBP). RESULTS: The study population comprised 201 patients and mean age was 41.7 years. The significant association between MMP9 rs17576 (B = 0.71, 95% CI 0.18 to 1.24, p = 0.009) and pain recovery remained statistically significant after adjusting for pain intensity at baseline, age, gender, smoking, body mass index, pain localization and emotional distress (B = 0.68, 95% CI 0.18 to 1.18, p = 0.008). In contrast, the association between OPRM1 (B = - 0.85, 95% CI - 1.66 to - 0.05, p = 0.038) and pain recovery was abolished in the multivariate analysis (B = - 0.72, 95% CI - 1.46 to 0.02, p = 0.058). Hence, MMP9 rs17576 and emotional distress independently seem to predict persistent back pain. The predictive effect of OPRM1 rs179971 with regard to the same outcome is probably dependent on other factors including emotional processing. Trial registration The Regional Committee for Medical Research and Ethics reference number 2014/1754.

Polydatin suppresses nucleus pulposus cell senescence, promotes matrix homeostasis and attenuates intervertebral disc degeneration in rats.

Intervertebral disc degeneration (IVDD) is one of the major causes of low back pain. Polydatin (PD) has been shown to exert multiple pharmacological effects on different diseases; here, we test the therapeutic potential of PD for IVDD. In in-vitro experiments, we confirmed PD is nontoxic to nucleus pulposus cells (NPCs) under the concentration of 400 µmol/L. Furthermore, PD was able to decrease the level of senescence in TNF-α-treated NPCs, as indicated by ß-gal staining as well as senescence markers p53 and p16 expression. In the aspect of extracellular matrix (ECM), PD not only reduced metalloproteinase 3 (MMP-3), metalloproteinase 13 (MMP-13) and a disintegrin-like and metalloproteinase thrombospondin type 1 motif 4 (ADAMTS-4) expression, but also increased aggrecan and collagen II levels. Mitochondrion is closely related to cellular senescence and ECM homeostasis; mechanistically, we found PD may rescue TNF-α-induced mitochondrial dysfunction, and it may also promote Nrf2 expression and activity. Silencing Nrf2 partly abolished the protective effects of PD on mitochondrial homeostasis, senescence and ECM homeostasis in TNF-α-treated NPCs. Correspondingly, PD ameliorated IVDD in rat model by promoting Nrf2 activity, preserving ECM and inhibiting senescence in nucleus pulposus cells. To sum up, our study suggests that PD exerts protective effects in NPCs against IVDD and reveals the underlying mechanism of PD on Nrf2 activation in NPCs.

Protective properties of spliced X box binding protein 1 in ozone­induced spinal cord neuronal death.

Administration of ozone (O3) is often used in the treatment of low back pain. Administration of O3 can, however, cause neurotoxicity in spinal cord neurons via induction of endoplasmic reticulum (ER) calcium (Ca2+) release and activation of the Ca2+/calmodulin­dependent protein kinase II (CaMKII)/mitogen­activated protein kinase (MAPK) pathway. The aim of the current study was to confirm whether administration of O3 causes ER stress and if the consequential overexpression of adenovirus­mediated spliced X box binding protein 1 (XBP1s), which is the effector of ER stress and a crucial transcriptional factor gene in charge of cell survival, has a protective effect on spinal cord neurons after O3 exposure. To address this aim, the expression of GRP78, an ER chaperone and signaling regulator, and the expression of XBP1s in rat primary spinal cord neurons that underwent O3 exposure were investigated. Primary neurons exposed to O3 exhibited increased GRP78 and XBP1s expression levels. Interestingly, the effect of decreased neuron viability was blocked when cells were pretreated with Adv­XBP1s. Moreover, overexpression of XBP1s suppressed cell death caused by O3 exposure. These results suggest that overexpression of activated XBP1s protects against neuronal cell death following O3 exposure and that activation of the XBP1s pathway may offer a preventative way for prophylactic treatment of spinal cord neurons exposed to O3.

Common Missense Variant of SCN9A Gene Is Associated with Pain Intensity in Patients with Chronic Pain from Disc Herniation.

Objective: Lumbar intervertebral disk herniation (LDH) is considered one of the major risk factors for lower back pain, mainly caused by irritation of a spinal nerve or its root. One of the genes related to pain perception is SCN9A, which encodes the voltage gated sodium channel NaV1.7, a key molecule involved in peripheral pain processing. It had been presented before that a common polymorphism within SCN9A (rs6746030: G > A, R1150W) might influence nociception in the general population. Hence, the present study was aimed at investigating the association between SCN9A polymorphism and pain sensitivity. Methods: Pain intensity was measured by means of the visual analog pain scale (VAS) in 176 Caucasian patients with a history of leg and back pain who had been diagnosed with LDH and underwent lumbar discectomy. SCN9A polymorphism was determined by means of TaqMan assay. Results: A significantly higher preoperative back pain intensity was observed among rs6746030 A minor allele carriers, compared with GG homozygotes (VAS = 7.5 ± 2.4 vs 6.5 ± 2.7, P = 0.012). Similarly, A allele carriers were characterized by higher values of leg pain prior to surgery (VAS = 7.8 ± 2.3 vs 6.8 ± 2.6, P = 0.013). However, postoperative improvement in pain reduction was similar in both groups. Conclusions: Our results suggest that the SCN9A rs6746030 polymorphism may be associated with pain intensity in patients suffering from symptomatic disc herniation.

Development of an in vivo mouse model of discogenic low back pain.

Discogenic low back pain (DLBP) is extremely common and costly. Effective treatments are lacking due to DLBP's unknown pathogenesis. Currently, there are no in vivo mouse models of DLBP, which restricts research in this field. The aim of this study was to establish a reliable DLBP model in mouse that captures the pathological changes in the disc and allows longitudinal pain testing. The model was generated by puncturing the mouse lumbar discs (L4/5, L5/6, and L6/S1) and removing the nucleus pulposus using a microscalpel under the microscope. Histology, molecular pathways, and pain-related behaviors were examined. Over 12 weeks post-surgery, animals displayed the mechanical, heat, and cold hyperalgesia along with decreased burrowing and rearing. Histology showed progressive disc degeneration with loss of disc height, nucleus pulposus reduction, proteoglycan depletion, and annular fibrotic disorganization. Immunohistochemistry revealed a substantial increase in inflammatory mediators at 2 and 4 weeks. Nerve growth factor was upregulated from 2 weeks to the end of the experiment. Nerve fiber ingrowth was induced in the injured discs after 4 weeks. Disc-puncture also produced an upregulation of neuropeptides in dorsal root ganglia neurons and an activation of glial cells in the spinal cord dorsal horn. These findings indicate that the cellular and structural changes in discs, as well as peripheral and central nervous system plasticity, paralleled persistent, and robust behavioral pain responses. Therefore, this mouse DLBP model could be used to investigate mechanisms underlying discogenic pain, thereby facilitating effective drug screening and development of treatments for DLBP.

Mast Cell-Intervertebral disc cell interactions regulate inflammation, catabolism and angiogenesis in Discogenic Back Pain.

Low back pain (LBP) is a widespread debilitating disorder of significant socio-economic importance and intervertebral disc (IVD) degeneration has been implicated in its pathogenesis. Despite its high prevalence the underlying causes of LBP and IVD degeneration are not well understood. Recent work in musculoskeletal degenerative diseases such as osteoarthritis have revealed a critical role for immune cells, specifically mast cells in their pathophysiology, eluding to a potential role for these cells in the pathogenesis of IVD degeneration. This study sought to characterize the presence and role of mast cells within the IVD, specifically, mast cell-IVD cell interactions using immunohistochemistry and 3D in-vitro cell culture methods. Mast cells were upregulated in painful human IVD tissue and induced an inflammatory, catabolic and pro-angiogenic phenotype in bovine nucleus pulposus and cartilage endplate cells at the gene level. Healthy bovine annulus fibrosus cells, however, demonstrated a protective role against key inflammatory (IL-1ß and TNFα) and pro-angiogenic (VEGFA) genes expressed by mast cells, and mitigated neo-angiogenesis formation in vitro. In conclusion, mast cells can infiltrate and elicit a degenerate phenotype in IVD cells, enhancing key disease processes that characterize the degenerate IVD, making them a potential therapeutic target for LBP.

Variants of ACAN are associated with severity of lumbar disc herniation in patients with chronic low back pain.

INTRODUCTION: Disc herniation is a complex spinal disorder associated with disability and high healthcare cost. Lumbar disc herniation is strongly associated with disc degeneration. Candidate genes of the aggrecan metabolic pathway may associate with the severity of lumbar disc herniation. OBJECTIVES: This study evaluated the association of single nucleotide variants (SNVs) of the candidate genes of the aggrecan metabolic pathway with the severity of lumbar disc herniation in patients with chronic mechanical low back pain. In addition, we assessed the in-silico functional analysis of the significant SNVs and association of their haplotypes with the severity of lumbar disc herniation. METHODS: A descriptive cross sectional study was carried out on 106 patients. Severity of disc herniation and disc degeneration were assessed on T2-weighted mid sagittal lumbar MRI scan. Sixty two exonic SNVs of ten candidate genes of aggrecan metabolic pathway (ACAN, IL1A, IL1B, IL6, MMP3, ADAMTS4, ADAMTS5, TIMP1, TIMP2 and TIMP3) were genotyped on a Sequenom MassARRAY iPLEX platform. Multivariable linear regression analysis was carried out using PLINK 1.9 software adjusting for age, gender, body mass index and severity of disc degeneration. Four online bioinformatics tools (Provean, SIFT, PolyPhen and Mutation Taster) were used for in-silico functional analysis. RESULTS: Mean age was 52.42 ± 9.42 years and 69.8% were females. The mean severity of disc herniation was 2.81 ± 1.98. The rs2272023, rs35430524, rs2882676, rs2351491, rs938609, rs3825994, rs1042630, rs698621 and rs3817428 variants and their haplotypes of ACAN were associated with the severity of lumbar disc herniation. However, only the rs35430524, rs938609 and rs3817428 variants of ACAN were detected as pathogenic by in-silico functional analysis. CONCLUSIONS: SNVs of ACAN and their haplotypes are associated with the severity of lumbar disc herniation. Functional genetic studies are necessary to identify the role of these significant SNVs in the pathogenesis of disc herniation.