Genetics of the degenerated intervertebral disc

Reviving Intervertebral Discs: Treating Degeneration Using Advanced Delivery Systems

Intervertebral disc degeneration (IVDD) is commonly associated with many spinal problems, such as low back pain, and significantly impacts a patient's quality of life. However, current treatments for IVDD, which include conservative and surgical methods, are limited in their ability to fully address degeneration. To combat IVDD, delivery-system-based therapy has received extensive attention from researchers. These delivery systems can effectively deliver therapeutic agents for IVDD, overcoming the limitations of these agents, reducing leakage and increasing local concentration to inhibit IVDD or promote intervertebral disc (IVD) regeneration. This review first briefly introduces the structure and function of the IVD, and the related pathophysiology of IVDD. Subsequently, the roles of drug-based and bioactive-substance-based delivery systems in IVDD are highlighted. The former includes natural source drugs, nonsteroidal anti-inflammatory drugs, steroid medications, and other small molecular drugs. The latter includes chemokines, growth factors, interleukin, and platelet-rich plasma. Additionally, gene-based and cell-based delivery systems are briefly involved. Finally, the limitations and future development of the combination of therapeutic agents and delivery systems in the treatment of IVDD are discussed, providing insights for future research.

Leptin Induces MMP-1 Expression Through the RhoA/ERK1/2/NF-κB Axis in Human Intervertebral Disc Cartilage Endplate-Derived Stem Cells

Purpose

Intervertebral disc (IVD) degeneration, associated with aging, may cause low back pain and disability, with obesity as a significant risk factor. In a prior study, we found a positive correlation between IVD degeneration and levels of matrix metalloproteinase-1 (MMP-1) and leptin. Yet, the interaction between MMP-1 and leptin in IVD degeneration is unclear. Our research seeks to explore leptin's influence on MMP-1 expression and the underlying mechanisms in human intervertebral disc cartilage endplate-derived stem cells, specifically SV40 cells.

Methods

The mRNA and protein expression in leptin-stimulated SV40 cells were assessed using RT-real-time PCR and Western blotting or ELISA, respectively. We examined leptin-mediated RhoA activation through a GTP-bound RhoA pull-down assay. Furthermore, the phosphorylation levels of mitogen-activated protein kinases and AKT in leptin-stimulated SV40 cells were analyzed using Western blotting. The activation of NF-κB by leptin was investigated by assessing phosphorylation of IKKα/β, IκBα, and NF-κB p65, along with the nuclear translocation of NF-κB p65. To understand the underlying mechanism behind leptin-mediated MMP-1 expression, we employed specific inhibitors.

Results

Leptin triggered the mRNA and protein expression of MMP-1 in SV40 cells. In-depth mechanistic investigations uncovered that leptin heightened RhoA activity, promoted ERK1/2 phosphorylation, and increased NF-κB activity. However, leptin did not induce phosphorylation of JNK1/2, p38, or AKT. When we inhibited RhoA, ERK1/2, and NF-κB, it resulted in a decrease in MMP-1 expression. Conversely, inhibition of reactive oxygen species and NADPH oxidase did not yield the same outcome. Additionally, inhibiting RhoA or ERK1/2 led to a reduction in leptin-induced NF-κB activation. Moreover, inhibiting RhoA also decreased leptin-mediated ERK1/2 phosphorylation.

Conclusion

These results indicated that leptin induced MMP-1 expression in SV40 cells through the RhoA/ERK1/2/NF-κB axis. This study provided the pathogenic role of leptin and suggested the potential therapeutic target for IVD degeneration.

Understanding Intervertebral Disc Degeneration: Background Factors and the Role of Initial Injury

The etiology of intervertebral disc degeneration (IVDD) is complex and multifactorial, and it is still not fully understood. A better understanding of the pathogenesis of IVDD will help to improve treatment regimens and avoid unnecessary surgical aggression. In order to summarize recent research data on IVDD pathogenesis, including genetic and immune factors, a literature review was conducted. The pathogenesis of IVDD is a complex multifactorial process without an evident starting point. There are extensive data on the role of the different genetic factors affecting the course of the disease, such as mutations in structural proteins and enzymes involved in the immune response. However, these factors alone are not sufficient for the development of the disease. Nevertheless, like mechanical damage, they can also be considered risk factors for IVDD. In conclusion, currently, there is no consensus on a single concept for the pathogenesis of IVDD. We consider the intervertebral disc autoimmune damage hypothesis to be the most promising hypothesis for clinicians, because it can be extrapolated to all populations and does not counteract other factors. The genetic factors currently known do not allow for building effective predictive models; however, they can be used to stratify the risks of individual populations.

Lumbar Disc Degeneration Affects the Risk of Rod Fracture Following PSO; A Finite Element Study

STUDY DESIGN

Finite element (FE) study.

OBJECTIVE

Pedicle subtraction osteotomy (PSO) is a surgical method to correct sagittal plane deformities. In this study, we aimed to investigate the biomechanical effects of lumbar disc degeneration on the instrumentation following PSO and assess the effects of using interbody spacers adjacent to the PSO level in a long instrumented spinal construct.

METHODS

A spinopelvic model (T10-pelvis) with PSO at the L3 level was used to generate 3 different simplified grades of degenerated lumbar discs (mild (Pfirrmann grade III), moderate (Pfirrmann grade IV), and severe (Pfirrmann grade V)). Instrumentation included eighteen pedicle screws and bilateral primary rods. To investigate the effect of interbody spacers, the model with normal disc height was modified to accommodate 2 interbody spacers adjacent to the PSO level through a lateral approach. For the models, the rods' stress distribution, PSO site force values, and the spine range of motion (ROM) were recorded.

RESULTS

The mildly, moderately, and severely degenerated models indicated approximately 10%, 26%, and 40% decrease in flexion/extension motion, respectively. Supplementing the instrumented spinopelvic PSO model using interbody spacers reduced the ROM by 22%, 21%, 4%, and 11% in flexion, extension, lateral bending, and axial rotation, respectively. The FE results illustrated lower von Mises stress on the rods and higher forces at the PSO site at higher degeneration grades and while using the interbody spacers.

CONCLUSIONS

Larger and less degenerated discs adjacent to the PSO site may warrant consideration for interbody cage instrumentation to decrease the risk of rod fracture and PSO site non-union.

Traumatic lumbar disc herniation: A systemic case review and meta-analysis

Introduction

Traumatic lumbar disc herniation (TLDH) without fracture in the in-situ motion segment is a rare occurrence compared with degenerative herniation.

Research question

This study provides a systematic discussion of various aspects related to the diagnosis of TLDH.

Material and methods

This review includes 12 cases of TLDH with MR-images since 2009 published in the PubMed and one adjunct illustration. The cases were categorized into two groups for a comprehensive analysis, TLDH with or without in-situ segment fracture. Additionally, we reported a case of a 43-year-old female patient with a recent stenosing TLDH at L5/S1, accompanied by a large sequestration (disc herniation stage-4, and Michigan State University Classification: MSU 3-AB) and an endplate compression fracture at L2 (AO A1).

Results

Isolated traumatic lumbar disc herniation is possible, but it is required exclude cases with fractures in the in-situ motion segment.

Discussion and conclusion

Trauma with related injury mechanisms is the highest priority for the diagnosis of TLDH. Low-grade disc degeneration without significant instability could be accepted for diagnosing TLDH. A TLDH on MR images might show a slightly lower T2-signal compared to the CSF and a homogeneous T1-signal like the spinal cord, as well as a similar STIR-signal of the sequestration and CSF. If necessary, a histological examination could be performed to evaluate the degenerative changes in the injured disc, especially to assist the evaluation due to legal reasons.

The role of ADAMTS6 and ADAMTS17 polymorphisms in susceptibility to lumbar disc herniation in Chinese Han population

PURPOSE

LDH caused by lumbar disc degeneration is associated with genetic factors. However, the role of ADAMTS6 and ADAMTS17 genes in LDH risk is still unknown.

METHODS

To investigate the interaction between ADAMTS6 and ADAMTS17 variants in the susceptibility of LDH, five SNPs were genotyped in 509 patients and 510 healthy individuals. The experiment used logistic regression to calculate odds ratio (OR) and 95% confidence interval (CI). Multi-factor dimensionality reduction (MDR) was chosen to evaluate impact of interaction of SNP-SNP on susceptibility to LDH.

RESULTS

ADAMTS17-rs4533267 is significantly associated with reducing risk of LDH (OR = 0.72, 95% CI = 0.57-0.90, p = 0.005). Stratified analysis indicates that ADAMTS17-rs4533267 is significantly associated with the reducing risk of LDH among participants aged ≤ 48 years old. In addition, we observed that ADAMTS6-rs2307121 was associated with increasing risk of LDH in females. MDR analysis shows that single-locus model composed by ADAMTS17-rs4533267 can be chosen as the best model for predicting susceptibility to LDH (CVC = 10/10, test accuracy = 0.543).

CONCLUSION

ADAMTS6-rs2307121 and ADAMTS17-rs4533267 are potentially associated with LDH susceptibility. In particular, ADAMTS17-rs4533267 has a strong association with reducing risk of LDH.

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

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

Exogenous Klotho ameliorates extracellular matrix degradation and angiogenesis in intervertebral disc degeneration via inhibition of the Rac1/PAK1/MMP-2 signaling axis

Intervertebral disc degeneration (IDD) is highly ubiquitous in the aged population and is an essential factor for low back pain and spinal disability. Because of the association between IDD and senescence, we investigated the ability of the anti-aging drug Klotho to inhibit age-dependent advancement of nucleus pulposus cell (NPC) degeneration. The results indicated that 400 pM exogenous Klotho significantly ameliorated extracellular matrix degradation and angiogenesis. Moreover, we demonstrated that the suppression of angiogenesis and extracellular matrix catabolism was related to inhibition of the Ras-related C3 botulinum toxin substrate 1 (Rac1)/PAK1 axis and matrix metalloproteinase 2 protein expression by exogenous Klotho cotreatment with a Rac1 inhibitor, gene overexpression in NPCs, and stimulation of human umbilical vein endothelial cells with conditioned medium from NPCs. The treatment also preserved the NPC phenotype, viability, and matrix content. In conclusion, these results suggest that the new anti-aging drug Klotho is a potential treatment strategy to mitigate IDD, and thus, provides an innovative understanding of the molecular mechanism of IDD. DATA AVAILABILITY: All data supporting the findings of this study are available from the corresponding authors upon reasonable request.

Immuno-Modulatory Effects of Intervertebral Disc Cells

Low back pain is a highly prevalent, chronic, and costly medical condition predominantly triggered by intervertebral disc degeneration (IDD). IDD is often caused by structural and biochemical changes in intervertebral discs (IVD) that prompt a pathologic shift from an anabolic to catabolic state, affecting extracellular matrix (ECM) production, enzyme generation, cytokine and chemokine production, neurotrophic and angiogenic factor production. The IVD is an immune-privileged organ. However, during degeneration immune cells and inflammatory factors can infiltrate through defects in the cartilage endplate and annulus fibrosus fissures, further accelerating the catabolic environment. Remarkably, though, catabolic ECM disruption also occurs in the absence of immune cell infiltration, largely due to native disc cell production of catabolic enzymes and cytokines. An unbalanced metabolism could be induced by many different factors, including a harsh microenvironment, biomechanical cues, genetics, and infection. The complex, multifactorial nature of IDD brings the challenge of identifying key factors which initiate the degenerative cascade, eventually leading to back pain. These factors are often investigated through methods including animal models, 3D cell culture, bioreactors, and computational models. However, the crosstalk between the IVD, immune system, and shifted metabolism is frequently misconstrued, often with the assumption that the presence of cytokines and chemokines is synonymous to inflammation or an immune response, which is not true for the intact disc. Therefore, this review will tackle immunomodulatory and IVD cell roles in IDD, clarifying the differences between cellular involvements and implications for therapeutic development and assessing models used to explore inflammatory or catabolic IVD environments.

Mesenchymal Stem Cell-Derived Exosomes and Intervertebral Disc Regeneration: Review

Intervertebral disc degeneration (IVDD) is a common cause of lower back pain (LBP), which burdens individuals and society as a whole. IVDD occurs as a result of aging, mechanical trauma, lifestyle factors, and certain genetic abnormalities, leads to loss of nucleus pulposus, alteration in the composition of the extracellular matrix, excessive oxidative stress, and inflammation in the intervertebral disc. Pharmacological and surgical interventions are considered a boon for the treatment of IVDD, but the effectiveness of those strategies is limited. Mesenchymal stem cells (MSCs) have recently emerged as a possible promising regenerative therapy for IVDD due to their paracrine effect, restoration of the degenerated cells, and capacity for differentiation into disc cells. Recent investigations have shown that the pleiotropic effect of MSCs is not related to differentiation capacity but is mediated by the secretion of soluble paracrine factors. Early studies have demonstrated that MSC-derived exosomes have therapeutic potential for treating IVDD by promoting cell proliferation, tissue regeneration, modulation of the inflammatory response, and reduced apoptosis. This paper highlights the current state of MSC-derived exosomes in the field of treatment of IVDD with further possible future developments, applications, and challenges.

Rebalance of the Polyamine Metabolism Suppresses Oxidative Stress and Delays Senescence in Nucleus Pulposus Cells

Intervertebral disk degeneration (IDD) is a major cause of low back pain that becomes a prevalent age-related disease. However, the pathophysiological processes behind IDD are rarely known. Here, we used bioinformatics analysis based on the microarray datasets (GSE34095) to identify the differentially expressed genes (DEGs) as biomarkers and therapeutic targets in degenerated discs. From the previous studies, oxidative stress has been notified as a positive inducement of IDD, which causes DNA damage and accelerates cell senescence. Polyamine oxidase (PAOX), a member of the observed 1057 DEGs, is involved in polyamine metabolism and influences the oxidative balance in cells. However, it is uncertain if the IDD is implicated in the dysregulation of PAOX and polyamine metabolism. This study firstly verified the PAOX upregulation in human degenerated disc samples and applied an IL-1β-induced nucleus pulposus (NP) cell degeneration model to demonstrate that spermidine supplementation balanced polyamine metabolism and delayed NP cell senescence. Moreover, we confirmed that spermidine/N-acetylcysteine supplementation or Cdkn2a gene deletion stabilized the polyamine metabolism, suppressed oxidative stress, and therefore delayed the progress of IDD in older mice. Collectively, our study highlights the role of polyamine metabolism in IDD and foresees spermidine would be the advanced therapeutical drug for IDD.

AMPK as a Potential Therapeutic Target for Intervertebral Disc Degeneration

As the principal reason for low back pain, intervertebral disc degeneration (IDD) affects the health of people around the world regardless of race or region. Degenerative discs display a series of characteristic pathological changes, including cell apoptosis, senescence, remodeling of extracellular matrix, oxidative stress and inflammatory local microenvironment. As a serine/threonine-protein kinase in eukaryocytes, AMP-activated protein kinase (AMPK) is involved in various cellular processes through the modulation of cell metabolism and energy balance. Recent studies have shown the abnormal activity of AMPK in degenerative disc cells. Besides, AMPK regulates multiple crucial biological behaviors in IDD. In this review, we summarize the pathophysiologic changes of IDD and activation process of AMPK. We also attempt to generalize the role of AMPK in the pathogenesis of IDD. Moreover, therapies targeting AMPK in alleviating IDD are analyzed, for better insight into the potential of AMPK as a therapeutic target.

A novel circRNA-miRNA-mRNA network reveals hsa-circ-0040039 as a biomarker for intervertebral disc degeneration

Objective

Alterations in the structure and function of intervertebral discs by multifaceted chronic processes can result in intervertebral disc degeneration (IDD). The mechanisms involved in IDD are still unknown.

Methods

We investigated the possible mechanisms underlying IDD using a bioinformatics analysis of publicly available microarray expression datasets and built a circular RNA–microRNA–mRNA (circRNA–miRNA–mRNA) network based on the results. Datasets GSE67566 and GSE116726 were downloaded from the Gene Expression Omnibus (GEO) and analyzed using the limma package in R. The CircInteractome database was used to detect miRNAs related to circRNA, and TargetScan, miRDB, and miRTarBase were used to predict target mRNAs. Key target genes were annotated using Gene Ontology terms.

Results

The circRNA hsa-circ-0040039 was found to have the top log fold-change score. Analysis using Metascape showed that the associated genes were enriched mainly in the cell cycle. The Cytoscape plugin MCODE predicted that two members of the RAS oncogene family—RAB1A and RAB1B—and multiple coagulation factor deficiency (MCFD2) may play key roles in IDD.

Conclusion

Our results suggested that hsa-circ-0040039 and the related network may be potential biomarkers for IDD.

Association between polymorphisms of collagen genes and susceptibility to intervertebral disc degeneration: a meta-analysis

Background

Collagens are important structural components of intervertebral disc. A number of studies have been performed for association between polymorphisms of collagen genes and risk of intervertebral disc degeneration (IVDD) but yielded inconsistent results. Here, we performed a meta-analysis to investigate the association of collagen IX alpha 2 (COL9A2) Trp2, collagen IX alpha 3 (COL9A3) Trp3, collagen I alpha 1 (COL1A1) Sp1 and collagen XI alpha 1 (COL11A1) C4603T polymorphisms with susceptibility to IVDD.

Method

Eligible studies were retrieved by searching MEDLINE, EMBASE, Web of Science prior to 31 March, 2021. Odds ratio (OR) and corresponding 95% confidence interval (CI) were calculated for association strength.

Results

A total of 28 eligible studies (31 datasets comprising 5497 cases and 5335 controls) were included. COL9A2 Trp2 carriers had an increased risk of IVDD than non-carriers in overall population (OR = 1.43, 95% CI 0.99–2.06, P = 0.058), which did not reach statistical significance. However, Trp2 carriers had 2.62-fold (95% CI 1.15–6.01, P = 0.022) risk than non-carriers in Caucasians. COL9A3 Trp3 was not associated with IVDD risk (OR = 1.28, 95% CI 0.81–2.02, P = 0.299). T allele and TT genotype of COL1A1 Sp1 (+ 1245G > T) were correlated with increased risk of IVDD. Significant associations were found between COL11A1 C4603T and IVDD risk under allelic (OR = 1.33, 95% CI 1.20–1.48), dominant (OR = 1.45, 95% CI 1.26–1.67), recessive (OR = 1.55, 95% CI 1.21–1.98) and homozygote model (OR = 1.81, 95% CI 1.40–2.34).

Conclusions

COL1A1 Sp1 and COL11A1 C4603T polymorphism are associated with IVDD risk while the predictive roles of collagen IX gene Trp2/3 need verification in more large-scale studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02724-8.

The Role of Polymorphisms in Collagen-Encoding Genes in Intervertebral Disc Degeneration

(1) Background: The purpose of this review is to analyze domestic and foreign studies on the role of collagen-encoding genes polymorphism in the development of intervertebral discs (IVDs) degeneration in humans. (2) Methods: We have carried out a search for full-text articles published in e-Library, PubMed, Oxford Press, Clinical Case, Springer, Elsevier and Google Scholar databases. The search was carried out using keywords and their combinations. The search depth was 5 years (2016–2021). In addition, this review includes articles of historical interest. Despite an extensive search, it is possible that we might have missed some studies published in recent years. (3) Results: According to the data of genome-wide and associative genetic studies, the following candidate genes that play a role in the biology of IVDs and the genetic basis of the processes of collagen degeneration of the annulus fibrosus and nucleus pulposus of IVDs in humans are of the greatest interest to researchers: COL1A1, COL2A1, COL9A2, COL9A3, COL11A1 and COL11A2. In addition, the role of genes COL1A2, COL9A1 and others is being actively studied. (4) Conclusions: In our review, we summarized and systematized the available information on the role of genetic factors in IVD collagen fibers turnover and also focused on the functions of different types of collagen present in the IVD. Understanding the etiology of impaired collagen formation can allow doctors to prescribe pathogenetically-based treatment, achieving the most effective results.

Prediction of a Potential Mechanism of Intervertebral Disc Degeneration Based on a Novel Competitive Endogenous RNA Network

Low back pain which resulted from intervertebral disc degeneration (IDD) is a common health problem that afflicts people all over the world. Due to the lack of an overall understanding of the molecular interactions involved in IDD, we hope to better understand the pathogenetic mechanisms that drive the degenerative process. The purpose of this study is to obtain mRNAs, miRNAs, lncRNAs, and circRNAs associated with IDD gained from public databases and to establish an interaction network. According to the results of microarray analysis and bioinformatics analysis from the contrast of IDD and normal nucleus pulposus tissues, a total of 49 mRNAs, 10 miRNAs, 30 lncRNAs, and 4 circRNAs were obtained and a lncRNA/circRNA–miRNA–mRNA interaction network was constructed. NEAT1–miR-5100–COL10A1 and miR663AHG/HEIH/hsa-circ-0003600–miR-4741–HAS2/HYAL1/LYVE1 might be potential interaction axes of the molecular mechanism in IDD. The increased expression of NEAT1 might inhibit miR-5100 and subsequently upregulate the expression of COL10A1, which leads to IDD, while the increased expression of miR663AHG/HEIH/hsa-circ-0003600 might inhibit miR-4741 and indirectly upregulate HAS2/HYAL1/LYVE1, and leads to the protection from IDD. More interaction axes are to be exploited to provide theoretical bases for further study on IDD.

The role of single nucleotide polymorphisms of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) on susceptibility to herniated nucleus pulposus: a systematic review and meta-analysis

Background: The pathogenesis of herniated nucleus pulposus (HNP) is complex and may involve the wide variety of gene polymorphism. However, the reports from the existing studies are inconclusive. The objective of this study was to determine the role of single nucleotide polymorphisms (SNPs) in interleukin 1 alpha ( IL-1A), tumor necrosis factor-alpha ( TNF-A), and vitamin D receptor ( VDR) genes on the susceptibility to herniated nucleus pulposus (HNP). Methods: Four databases (PubMed, Embase, Cochrane, and Web of Science) were searched as of April 1 st, 2021. Authors, publication year, targeted genes, genotype and allele frequency in each case and control groups were collected. Newcastle-Ottawa scale was used to evaluate the publication quality. The pooled estimates of association of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) and susceptibility to HNP were assessed using Z test. Results: We screened 3,067 unique studies for eligibility and three, two and nine case-control studies on IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI were included, respectively, in our meta-analysis. The studies consisting 369 HNP cases and 433 controls for IL-1A -889C>T, 252 cases and 259 controls for TNF-A -238G>A and 1130 cases and 2096 controls for VDR TaqI. Our pooled estimates indicated that there was no significant association of those SNPs with the susceptibility to HNP in any genotype, dominant model, recessive model, or allele comparations. Conclusion: Although individual studies suggested the important role of gene expression dysregulation associated with SNPs in IL-1A, TNF-A, and VDR, our data indicated that IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI had weak association with HNP susceptibility in both genotypes and allele distributions. However, since heterogeneity was identified among studies included in this meta-analysis, further meta-analysis with a larger population and subgroup analysis on specific population are warranted to support this finding.

The role of single nucleotide polymorphisms of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) on susceptibility to herniated nucleus pulposus

Background: The pathogenesis of herniated nucleus pulposus (HNP) is complex and may involve the wide variety of gene polymorphism. However, the reports from the existing studies are inconclusive. The objective of this study was to determine the role of single nucleotide polymorphisms (SNPs) in interleukin 1 alpha ( IL-1A), tumor necrosis factor-alpha ( TNF-A), and vitamin D receptor ( VDR) genes on the susceptibility to herniated nucleus pulposus (HNP). Methods: Four databases (PubMed, Embase, Cochrane, and Web of Science) were searched as of April 1 st, 2021. Authors, publication year, targeted genes, genotype and allele frequency in each case and control groups were collected. Newcastle-Ottawa scale was used to evaluate the publication quality. The pooled estimates of association of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) and susceptibility to HNP were assessed using Z test. Results: We screened 3,067 unique studies for eligibility and three, two and nine case-control studies on IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI were included, respectively, in our meta-analysis. The studies consisting 369 HNP cases and 433 controls for IL-1A -889C>T, 252 cases and 259 controls for TNF-A -238G>A and 1130 cases and 2096 controls for VDR TaqI. Our pooled estimates indicated that there was no significant association of those SNPs with the susceptibility to HNP in any genotype, dominant model, recessive model, or allele comparations. Conclusion: Although individual studies suggested the important role of gene expression dysregulation associated with SNPs in IL-1A, TNF-A, and VDR, our data indicated that IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI had weak association with HNP susceptibility in both genotypes and allele distributions. However, since heterogeneity was identified among studies included in this meta-analysis, further meta-analysis with a larger population and subgroup analysis on specific population are warranted to support this finding.

The role of single nucleotide polymorphisms of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) on susceptibility to herniated nucleus pulposus

Background: The objective of this study was to determine the role of single nucleotide polymorphisms (SNPs) in interleukin 1 alpha ( IL-1A), tumor necrosis factor-alpha ( TNF-A), and vitamin D receptor ( VDR) genes on the susceptibility to herniated nucleus pulposus (HNP). Methods: Four databases (PubMed, Embase, Cochrane, and Web of Science) were searched as of April 1 st, 2021. Authors, publication year, targeted genes, genotype and allele frequency in each case and control groups were collected. Newcastle-Ottawa scale was used to evaluate the publication quality. The pooled estimates of association of IL-1A -889C>T (rs1800587), TNF-A -238G>A (rs361525), and VDR TaqI (rs731236) and susceptibility to HNP were assessed using Z test and presented as odd ratio (OR) and 95% confidence intervals (95%CI). Results: We screened 3,067 unique studies for eligibility and three, two and nine studies on IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI were included, respectively, in our meta-analysis. The studies consisting 369 HNP cases and 433 controls for IL-1A -889C>T, 252 cases and 259 controls for TNF-A -238G>A and 1130 cases and 2096 controls for VDR TaqI. Our pooled estimates indicated that there was no significant association of those SNPs with the susceptibility to HNP in any genotype, dominant model, recessive model, or allele comparations. Conclusion: Although individual studies suggested the important role of gene expression dysregulation associated with SNPs in IL-1A, TNF-A, and VDR, our data indicated that IL-1A -889C>T, TNF-A -238G>A, and VDR TaqI had weak association with HNP susceptibility in both genotypes and allele distributions. However, since heterogeneity was identified among studies included in this meta-analysis, further meta-analysis with a larger population and subgroup analysis on specific population are warranted to support this finding.

Role of the Wnt pathway in the formation, development, and degeneration of intervertebral discs

Intervertebral disc degeneration (IVDD) is an age-related degenerative disease that is the main cause of low back pain. It seriously affects the quality of life of patients and places a heavy economic burden on families and society. The Wnt pathway plays an important role in the growth, development, and degeneration of intervertebral discs (IVDs). In the embryonic stage, the Wnt pathway participates in the growth and development of IVD by promoting the transformation of progenitor cells into notochord cells and the extension of the notochord. However, the activation of the Wnt pathway after birth promotes IVD cell senescence, apoptosis, and degradation of the extracellular matrix and induces the production of inflammatory factors, thereby accelerating the IVDD process. This article reviews the relationship between the Wnt pathway and IVD, emphasizing its influence on IVD growth, development, and degeneration. Targeting this pathway may become an effective strategy for the treatment of IVDD.

Interaction between occupational physical burdens and low job control on musculoskeletal pain: Analysis of the 5th Korean Working Environment Survey

OBJECTIVE

This study aimed to investigate the interactive impacts between occupational physical burdens and psychological job demand or control on musculoskeletal pain (MSP) using nationally representative data for Korean workers.

METHODS

Using 5th Korean Working Conditions Survey (KWCS), we explored the interaction between occupational physical burdens and levels of psychological job demand or control on risk of MSP in 49 572 eligible participants. For quantitative evaluation of the interaction, relative excess risk due to interaction (RERI) was calculated.

RESULTS

In a group with low job control and at least one occupational physical burden, odds ratio (OR) for neck and upper extremity pain was 2.44 (95% CI, 2.24-2.66) compared with a group with high job control and no physical burden (a reference group: lowest risk), which was the highest value among the four groups, and the RERI was 0.35 (95% CI, 0.19-0.51). Similarly, OR for lower extremity pain was 2.15 (95% CI, 1.95-2.37) and RERI was 0.26 (95% CI, 0.07-0.45). However, the RERI was not significant in the case of psychological job demand.

CONCLUSION

This study revealed significant interactions between occupational physical burdens and low job control on MSP.

Targeted therapy for intervertebral disc degeneration: inhibiting apoptosis is a promising treatment strategy

Intervertebral disc (IVD) degeneration (IDD) is a multifactorial pathological process associated with low back pain (LBP). The pathogenesis is complicated, and the main pathological changes are IVD cell apoptosis and extracellular matrix (ECM) degradation. Apoptotic cell loss leads to ECM degradation, which plays an essential role in IDD pathogenesis. Apoptosis regulation may be a potential attractive therapeutic strategy for IDD. Previous studies have shown that IVD cell apoptosis is mainly induced by the death receptor pathway, mitochondrial pathway, and endoplasmic reticulum stress (ERS) pathway. This article mainly summarizes the factors that induce IDD and apoptosis, the relationship between the three apoptotic pathways and IDD, and potential therapeutic strategies. Preliminary animal and cell experiments show that targeting apoptotic pathway genes or drug inhibition can effectively inhibit IVD cell apoptosis and slow IDD progression. Targeted apoptotic pathway inhibition may be an effective strategy to alleviate IDD at the gene level. This manuscript provides new insights and ideas for IDD therapy.

Animal models of regenerative medicine for biological treatment approaches of degenerative disc diseases

Degenerative disc disease (DDD) is a painful, chronic and progressive disease, which is characterized by inflammation, structural and biological deterioration of the intervertebral disc (IVD) tissues. DDD is specified as cell-, age-, and genetic-dependent degenerative process that can be accelerated by environmental factors. It is one of the major causes of chronic back pain and disability affecting millions of people globally. Current treatment options, such as physical rehabilitation, pain management, and surgical intervention, can provide only temporary pain relief. Different animal models have been used to study the process of IVD degeneration and develop therapeutic options that may restore the structure and function of degenerative discs. Several research works have depicted considerable progress in understanding the biological basis of disc degeneration and the therapeutic potentials of cell transplantation, gene therapy, applications of supporting biomaterials and bioactive factors, or a combination thereof. Since animal models play increasingly significant roles in treatment approaches of DDD, we conducted an electronic database search on Medline through June 2020 to identify, compare, and discuss publications regarding biological therapeutic approaches of DDD that based on intradiscal treatment strategies. We provide an up-to-date overview of biological treatment strategies in animal models including mouse, rat, rabbit, porcine, bovine, ovine, caprine, canine, and primate models. Although no animal model could profoundly reproduce the clinical conditions in humans; animal models have played important roles in specifying our knowledge about the pathophysiology of DDD. They are crucial for developing new therapy approaches for clinical applications.

Integrating multiple microarray dataset analysis and machine learning methods to reveal the key genes and regulatory mechanisms underlying human intervertebral disc degeneration

Intervertebral disc degeneration (IDD), a major cause of lower back pain, has multiple contributing factors including genetics, environment, age, and loading history. Bioinformatics analysis has been extensively used to identify diagnostic biomarkers and therapeutic targets for IDD diagnosis and treatment. However, multiple microarray dataset analysis and machine learning methods have not been integrated. In this study, we downloaded the mRNA, microRNA (miRNA), long noncoding RNA (lncRNA), and circular RNA (circRNA) expression profiles (GSE34095, GSE15227, GSE63492 GSE116726, GSE56081 and GSE67566) associated with IDD from the GEO database. Using differential expression analysis and recursive feature elimination, we extracted four optimal feature genes. We then used the support vector machine (SVM) to make a classification model with the four optimal feature genes. The ROC curve was used to evaluate the model's performance, and the expression profiles (GSE63492, GSE116726, GSE56081, and GSE67566) were used to construct a competitive endogenous RNA (ceRNA) regulatory network and explore the underlying mechanisms of the feature genes. We found that three miRNAs (hsa-miR-4728-5p, hsa-miR-5196-5p, and hsa-miR-185-5p) and three circRNAs (hsa_circRNA_100723, hsa_circRNA_104471, and hsa_circRNA_100750) were important regulators with more interactions than the other RNAs across the whole network. The expression level analysis of the three datasets revealed that BCAS4 and SCRG1 were key genes involved in IDD development. Ultimately, our study proposes a novel approach to determining reliable and effective targets in IDD diagnosis and treatment.

Analysis of key genes and pathways associated with the pathogenesis of intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IDD) is widely known as the main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. This study aims to analyze the dataset GSE23130 using bioinformatics methods to identify the pivotal genes and pathways associated with IDD.

MATERIAL/METHODS

The gene expression data of GSE23130 was downloaded, and differentially expressed genes (DEGs) were extracted from 8 samples and 15 controls. GO and KEGG pathway enrichment analyses were performed. Also, protein-protein interaction (PPI) network was constructed and visualized, followed by identification of hub genes and key module.

RESULTS

A total of 30 downregulated and 79 upregulated genes were identified. The DEGs were mainly enriched in the regulation of protein catabolic process, extracellular matrix organization, collagen fibril organization, and extracellular structure organization. Meanwhile, we found that most DEGs were primarily enriched in the PI3K-Akt signaling pathway. The top 10 hub genes were FN1, COL1A2, SPARC, COL3A1, CTGF, LUM, TIMP1, THBS2, COL5A2, and TGFB1.

CONCLUSIONS

In summary, key candidate genes and pathways were identified by using integrated bioinformatics analysis, which may provide insights into the underlying mechanisms and offer potential target genes for the treatment of IDD.

A surgical decompression procedure for effective treatment of calcified lumbar disc herniation

OBJECTIVE

To present our experience in managing calcified lumbar disc herniation (cLDH) using a surgical decompression procedure.

METHODS

Patients who had low back pain radiating to the leg, were preoperatively diagnosed with cLDH by computed tomography and/or magnetic resonance imaging, and were treated with a surgical decompression procedure were studied. Those without cLDH or who were treated with a method other than decompression were excluded. The treatment outcome was analyzed using the visual analog scale (VAS) score, Oswestry Disability Index, and modified Macnab criteria.

RESULTS

Thirty-seven patients aged 60.5 ± 9.6 years were evaluated. The VAS scores were significantly decreased 1 day after surgery and remained low at the 3-month and 1-year follow-ups. The Oswestry Disability Index was also significantly lower at the 3-month and 1-year follow-ups. Ninety-four percent of patients rated the results as "excellent" or "good" according to the modified Macnab criteria at the 3-month follow-up. The patients developed few postoperative complications and no recurrence during 1 year of follow-up.

CONCLUSION

Our data suggest that the decompression approach is effective for management of cLDH at least in the short term (1 year) with respect to reducing pain and improving patient satisfaction with few complications.

Identifying compositional and structural changes in the nucleus pulposus from patients with lumbar disc herniation using Raman spectroscopy

Lower back pain (LBP) is one of the most common musculoskeletal complaints worldwide. Intervertebral disc degeneration (IDD) is considered to be a significant contributor to LBP; however, the mechanisms underlying IDD remain to be fully elucidated. One of the major features of IDD is the decreased content of type II collagen and proteoglycans in the nucleus pulposus (NP). The present study aimed to investigate the biochemical mechanisms of IDD at the microscopic level using Raman spectroscopy. Raman spectroscopy, based on inelastic scattering of light, is an emerging optical technique that may measure the chemical composition of complex biological samples, including biofluids, cells and tissues. In the present study, 30 NP tissue samples from 30 patients who were diagnosed with lumbar disc herniation and received spinal fusion surgery to relieve LBP were obtained and analyzed. Routine pre-operative 3.0T, T2-weighed MRI was used to classify the cases according to Pfirrmann grades and the T2 signal intensity value of the NP was measured. Subsequently, all NP samples were scanned and analyzed using a Laser MicroRaman Spectrometer at room temperature. The Raman spectral results demonstrated that the relative content of proteoglycans, expressed as the relative intensity ratio of two peaks (I₁₀₆₄/I₁₀₀₄), was significantly inversely correlated with the Pfirrmann grade (ρ=-0.6462; P<0.0001), whereas the content of collagen (amide I) was significantly positively correlated with the Pfirrmann grade (ρ=0.5141; P<0.01). In conclusion, the higher relative intensity of the ratio of two peaks (I₁₆₇₀/I₁₆₄₀; Amide I) represented a higher fractional content of disordered collagen, which suggested that the defective collagen structure may lead to NP abnormalities.

A Meta-analysis Assessing the Association Between COL11A1 and GDF5 Genetic Variants and Intervertebral Disc Degeneration Susceptibility

STUDY DESIGN

Meta-analysis to collect relevant studies to assess the association between COL11A1 and GDF5 genetic variants and susceptibility to IDD.

OBJECTIVE

The aim of this study was to assess whether or not COL11A1 and GDF5 genetic variants were associated with susceptibility to IDD.

SUMMARY OF BACKGROUND DATA

IDD or LDH is a major public health problem. There have been several studies evaluating the relationship between COL11A1 and GDF5 genetic variants with risk of intervertebral disc degeneration (IDD). However, the studies were limited in discrete outcome and sample size, and some of the results were contradictory.

METHODS

We systematically searched the relevant publications in electronic databases. Eligible studies were included based on the defined criteria. The pooled odds ratios (ORs) with its 95% confidence intervals (CIs) were received using STATA 15. Subgroup analysis, sensitivity analysis, publication bias, and the "Trim and fill" method were performed in the meta-analysis.

RESULTS

A total of 3287 IDD cases and 5115 controls were incorporated into the meta-analysis. Our results demonstrated that COL11A1 rs1676486 was significantly associated with increased IDD susceptibility under all genetic models (allele model T vs. C: OR = 1.40, 95% CI 1.23-1.59, P = 0.000; homozygote model TT vs. CC: OR = 1.89, 95%CI 1.40-2.56, P = 0.000; dominant model TT+TC vs. CC: OR = 1.52, 95% CI 1.29-1.80, P = 0.000; recessive model TT vs. TC + CC: OR = 1.58, 95% CI 1.18-2.12, P = 0.002). However, GDF5 rs143383 was not (allele model T vs. C: OR = 1.15, 95% CI 0.91-1.44, P = 0.244; homozygote model TT vs. CC: OR = 1.22, 95% CI 0.75-2.00, P = 0.429; dominant model TT vs. CC+CT: OR = 1.22, 95% CI 0.95-1.57, P = 0.112; recessive model TC + TT vs. CC: OR = 1.12, 95% CI 0.73-1.73, P = 0.594). Subgroup analysis indicated ethnicity was not the source of heterogeneity. Sensitivity analysis, publication bias, and the "Trim and fill" method demonstrated the meta-analysis was of reliability.

CONCLUSION

Our results suggested that COL11A1 rs1676486 was significantly associated with IDD and the T allele was a risky factor. However, GDF5 rs143383 was not.

LEVEL OF EVIDENCE

1.

Lack of association between COL1A1 and COL9A2 single nucleotide polymorphisms and intervertebral disc degeneration

BACKGROUND

Collagens are the main components of the extracellular matrix of intervertebral discs. The genetic mutations in collagen genes could potentially play a causal role in pathophysiology of intervertebral disc degeneration (IVDD). In this study, we investigate the association of COL1A1 and COL9A2 single nucleotide polymorphisms (SNPs) with IVDD.

MATERIAL AND METHODS

ninety-six Iranian IVDD patients and 94 controls matched for age and sex were included. 5 cc of peripheral blood samples were obtained for DNA extraction using the Phenol-Chloroform method. The primers for SNPs COL1A1 rs909102 and COL9A2 were designed based on the TaqMan protocol and genotyped by real-time PCR with TaqMan.

RESULTS

The 'T' allele, 'CC' and 'TT' genotypes of COL1A1 rs909102 were more common among patients, however not significantly. Despite the similar allele distribution of COL9A2 rs137853213 in patients and controls, the homozygote genotypes were more frequent among patients, though this was not significant either.

CONCLUSION

The allele and genotype distributions of COL1A1 rs909102 and COL9A2 rs137853213 SNPs were not significantly associated with IVDD in an Iranian population.

P14ARF inhibits regional inflammation and vascularization in intervertebral disc degeneration by upregulating TIMP3

In this study, we identified P14 alternate reading frame (P14ARF) as a novel regulator of inflammation and vascularization in intervertebral disk degeneration (IVDD). We collected IVD tissues from IVDD patients and normal individuals for analysis of P14ARF expression. We also induced experimental IVDD by needle puncture injuries in the caudal intervertebral disks of Sprague-Dawley (SD) rats and achieved recombinant adenovirus-mediated P14ARF overexpression in experimental IVDD rats. Regulation relationships between P14ARF and tissue inhibitors of metalloproteinases-3 (TIMP3) were confirmed in P14ARF-overexpressed and TIMP3-depleted nucleus pulposus (NP) cells. Tube formation in vitro was evaluated in coculture systems of human umbilical vein endothelial cells (HUVECs) and rat degenerated NP cells (DNPCs). Inflammatory response was assessed from levels of TNF-α, IL-1β, and IL-6 and neovascularization from expression of endothelial growth factor (VEGF). The P14ARF and TIMP3 were downregulated in degenerated IVD tissue derived from patients and experimental IVDD rats. Overexpressed P14ARF suppressed inflammatory cytokine levels and vascularization. There was decreased in vitro tube formation in response to P14ARF overexpression and TIMP3 elevation. Finally, attenuated inflammatory responses and suppression of VEGF were achieved by P14ARF-mediated promotion of TIMP3 in rat DNPCs. Taken together, the present study reveals that P14ARF/TIMP3 modulation of inflammatory response and vascularization in the context of IVDD highlights a potential target for future therapeutic strategies.

APOE-knockout in rabbits causes loss of cells in nucleus pulposus and enhances the levels of inflammatory catabolic cytokines damaging the intervertebral disc matrix

Rabbits with naturally high levels of cholesterol ester transfer protein (CETP), unlike rodents, have become an interesting animal model for the study of lipid metabolism and atherosclerosis, as they have similarities to humans in lipid metabolism, cardiovascular physiology and susceptibility to develop atherosclerosis. Rodents, such as mice, are not prone to atherosclerosis as they lack the mass and activity of CETP, as a key player in lipoprotein metabolism. Recently, APOE-knockout in rabbits has been shown to promote atherosclerosis and associated premature IVD degeneration that mimic the symptoms of atherosclerosis and structural changes of IVDs in humans. Here we examined whether APOE-knockout promoted IVD degeneration in rabbits is associated with imbalanced inflammatory catabolic activities, as the underlying problem of biological deterioration that mimic the symptoms of advanced IVD degeneration in humans. We analysed in lumbar nucleus pulposus (NP) of APOE-knockout rabbits the cell viabilities and the intracellular levels of inflammatory, catabolic, anti-catabolic and anabolic proteins derogating IVD matrix. Grades of IVD degeneration were evaluated by magnetic resonance imaging. NP cells were isolated from homozygous APOE-knockout and wild-type New Zealand White rabbits of similar age. Three-dimensional cell culture with low-glucose was completed in alginate hydrogel. Cell proliferation and intracellular levels of target proteins were examined by MTT and ELISA assays. Alike human NP cells of different disc degeneration grades, NP cells of APOE-knockout and wild-type rabbits showed significantly different in vivo cell population densities (p<0.0001) and similar in vitro proliferation rates. Furthermore, they showed differences in overexpression of selective inflammatory and catabolic proteins (p<0.0001) similar to those found in human NP cells of different disc degeneration grades, such as IL-1β, TNF-α, ADAMTS-4, ADAMTS-5 and MMP-3. This study showed that premature IVD degeneration in APOE-knockout rabbits was promoted by the accumulation of selective inflammatory catabolic factors that enhanced imbalances between catabolic and anabolic factors mimicking the symptoms of advanced IVD degeneration in humans. Thus, APOE-knockout rabbits could be used as a promising model for therapeutic approaches of degenerative disc disorders.

Dysregulation of STAT3 signaling is associated with endplate-oriented herniations of the intervertebral disc in Adgrg6 mutant mice

Degenerative changes of the intervertebral disc (IVD) are a leading cause of disability affecting humans worldwide and has been attributed primarily to trauma and the accumulation of pathology during aging. While genetic defects have also been associated with disc degeneration, the precise mechanisms driving the initiation and progression of disease have remained elusive due to a paucity of genetic animal models. Here, we discuss a novel conditional mouse genetic model of endplate-oriented disc herniations in adult mice. Using conditional mouse genetics, we show increased mechanical stiffness and reveal dysregulation of typical gene expression profiles of the IVD in adhesion G-protein coupled receptor G6 (Adgrg6) mutant mice prior to the onset of endplate-oriented disc herniations in adult mice. We observed increased STAT3 activation prior to IVD defects and go on to demonstrate that treatment of Adgrg6 conditional mutant mice with a small molecule inhibitor of STAT3 activation ameliorates endplate-oriented herniations. These findings establish ADGRG6 and STAT3 as novel regulators of IVD endplate and growth plate integrity in the mouse, and implicate ADGRG6/STAT3 signaling as promising therapeutic targets for endplate-oriented disc degeneration.

Back pain is a leading cause of disability in humans worldwide and one of the most common culprits of these issues are the consequence of degenerative changes of the intervertebral disc. Here, we demonstrate that conditional loss of the Adgrg6 gene in cartilaginous tissues of the spine results in endplate-oriented disc herniations and degenerative changes of the intervertebral disc in mice. We further establish that these obvious degenerative changes of the disc are preceded by substantial alterations in normal gene expression profiles, including upregulation of pro-inflammatory STAT3 signaling, and increased mechanical stiffness of the intervertebral disc. Increased STAT3 activation is a signal observed in other models of degenerative musculoskeletal tissues. As such, we tested whether systemic treatment with a small-molecule STAT3 inhibitor would protect against the formation of endplate-oriented disc herniations in conditional Adgrg6 mutant mice, and report a significant positive improvement of histopathology in our treatment group. Taken together, we demonstrate a novel conditional model of endplate-oriented disc herniation in mouse. We establish ADGRG6 and STAT3 as novel regulators of endplate integrity of the intervertebral disc in mouse and suggest that modulation of ADGRG6/STAT3 signaling could provide robust disease-modifying targets for endplate-oriented disc degeneration in humans.

The relationship of the shear wave elastography findings of patients with unilateral lumbar disc herniation and clinical characteristics

Background

The aim of this study was to find out whether the shear wave elastography (SWE) findings of patients with unilateral lumbar disc herniation (LDH) were related to clinical characteristics.

Methods

For this purpose, the study group included patients (N = 20; 13 male, 7 female) with complaints of unilateral sciatica, with foraminal stenosis caused by one level of LDH (L4-L5 or L5-S1). An gender-and age-matched control group (N = 27; 16 male, 11 female) was included. All the patients were examined on both the axial and longitudinal planes bilaterally at the same level using a convex array probe (1- 6 MHz, Supersonic Imagine, Aix en Provence, France).

Results

The sciatic nerve stiffness measured on longitudinal planes of the affected side was significantly higher than unaffected side (p < 0.001) and the control group (P < 0.05). Furthermore, the symptom duration of unilateral LDH is positively correlated with the stiffness the sciatic nerve (r = 0.52, p = 0.019).

Conclusion

According to these findings, ultrasound imaging can be considered as a useful tool to detect changes in the sciatic nerve due to disc herniation. This technique will have a promising prospect for many patients with unilateral LDH in monitoring stiffness during rehabilitation and before or after surgery.

Genetic Influence in Disc Degeneration - Systematic Review of Literature

Disc degeneration is a condition that compromises the intervertebral disc functions, which can lead to several important pathological processes, such as disc herniation and canal stenosis. Although its etiology is still unknown, more and more studies have demonstrated the preponderant role of genetic factors to the detriment of environmental factors. Aiming to review the current knowledge about the genes associated with intervertebral disc degeneration, we have performed a narrative review based on the medical literature in the English language from the last 10 years regarding this subject. We have concluded that several genes have been associated with disc degeneration in humans, including the genes for collagen I α-1 ( COL1A1 ), collagen IX ( COL9A2 and COL9A3 ), collagen XI ( COL11A2 ), interleukin 6 ( IL-6 ), aggrecan ( AGC1 ), vitamin D receptor ( VDR ), and matrix metalloproteinase 3 ( MMP-3) , in addition to microRNAs. Therefore, the present review emphasizes the latest advancements in the association of genes with specific phenotypes of degenerated discs, single-nucleotide polymorphisms, heritage and genetic-environmental interactions in relation to disc degeneration to help future reviews regarding the genetic mechanisms underlying these processes.

TIGAR impedes compression-induced intervertebral disc degeneration by suppressing nucleus pulposus cell apoptosis and autophagy

To investigate whether TP53-induced glycolysis and apoptosis regulator (TIGAR) participates in compression-induced intervertebral disc (IVD) degeneration, and to determine the regulatory effect of TIGAR on nucleus pulposus (NP) cell autophagy and apoptosis following compression-induced injuries. IVD tissues were collected from human patients undergoing surgery (n = 20) and skeletally mature Sprague-Dawley rats (n = 15). Initially, the effect of compression on the expression of TIGAR was evaluated with in vivo and in vitro models. In addition, TIGAR was silenced to investigate the regulatory effect of TIGAR on compression-induced intracellular reactive oxygen species (ROS) levels, autophagy, and apoptosis in rat NP cells. Furthermore, the P53 inhibitor pifithrin-α (PFTα) and SP1 inhibitor mithramycin A were employed to detect expression level changes of TIGAR and autophagy-associated target molecules. TIGAR expression of NP cells increased gradually in human degenerative IVDs and in rat NP cells under compression both in vivo and in vitro. TIGAR knockdown enhanced compression-induced intracellular ROS generation and the NADPH/NADP⁺ and GSH/GSSG ratios. Moreover, TIGAR knockdown amplified the compression-induced caspase-3 activation and the apoptosis rate of rat NP cells. Likewise, knockdown of TIGAR significantly accelerated LC3B expression and autophagosome formation in rat NP cells during compression-induced injuries. The results also established that mithramycin A could inhibit TIGAR expression and autophagy levels in NP cells under compression conditions, while PFTα had no similar effect. Our data demonstrated that TIGAR acted as an important endogenous negative regulator of ROS levels, which might inhibit compression-induced apoptosis and autophagy through SP1-dependent mechanisms.

Current concepts for lumbar disc herniation

PURPOSE

To present the pathophysiology, biology, clinical presentation, diagnosis, and current treatment options for lumbar disc herniation.

METHODS

A thorough literature search was undertaken in PubMed and Google Scholar to summarize the current knowledge and future perspectives on lumbar disc herniation.

RESULTS

Several changes in the biology of the intervertebral disc are thought to contribute to disc herniation; nevertheless, the exact inciting event leading to disc herniation is yet to be discovered. Non-operative treatments have stood the test of time as the first-line treatment for most patients with lumbar disc herniation; however, operative treatment remains the current gold standard, with minimally invasive endoscopic microdiscectomy techniques showing best results with respect to postoperative pain and function.

CONCLUSIONS

The exact event leading to disc herniation remains unclear. Non-operative treatments should be the first-line treatment for most patients with lumbar disc herniation. Operative treatment remains the current gold standard, with minimally invasive endoscopic microdiscectomy techniques showing best results with respect to postoperative pain and function. Regenerative medicine is promising.

Meta-Analysis of the Association Between FAS Ligand and TRAIL Genetic Polymorphisms and Intervertebral Disc Degeneration Susceptibility in Chinese Han population

STUDY DESIGN

Meta-analysis to collect all the relevant studies to further investigate whether or not the FAS ligand (FASL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) genetic polymorphisms are associated with susceptibility to intervertebral disc degeneration (IDD) in Chinese Han population.

OBJECTIVE

To investigate whether or not the FASL and TRAIL genetic polymorphisms are associated with susceptibility to IDD in Chinese Han population.

SUMMARY OF BACKGROUND DATA

FASL and TRAIL are both apoptotic gene. Several studies have assessed the associations of FASL and TRAIL gene with risk of IDD in Chinese Han population, but the results are inconsistent.

METHODS

We systematically searched the PubMed, EMBASE, Medline, Scopus, Web of Science, CBM, and the Cochrane Library databases. Eligible studies assessing the polymorphisms in the FASL and TRAIL gene and risk of IDD were incorporated. The pooled odds ratio (OR) with its 95% confidence intervals (95% CI) was used.

RESULTS

Six studies with a total of 1766 IDD cases and 1533 controls were finally included in the meta-analysis. Meta-analysis of FASL-844C/T (rs763110) polymorphism was statistically associated with decreased IDD risk under all genetic models (allele model: OR = 0.68, 95% CI 0.59-0.80, P = 0.000; homozygote model: OR = 0.35, 95% CI 0.25-0.53, P = 0.000; dominant model: OR = 0.38, 95% CI 0.25-0.58, P = 0.000; recessive model: OR = 0.69, 95% CI 0.58-0.84, P = 0.000). There was a significant association between TRAIL-1595C/T (rs1131580) polymorphism with increased IDD risk under each genetic model (allele model: OR = 1.77, 95% CI 1.47-2.13, P = 0.000; homozygote model: OR = 2.44, 95% CI 1.70-3.51, P = 0.000; dominant model: OR = 1.67, 95% CI 1.22-2.29, P = 0.002; recessive model: OR = 3.13, 95% CI 2.40-4.08, P = 0.000). In addition, the association between TRAIL-1525G/A (rs1131568) polymorphism and the susceptibility of IDD was statistically significant under all genetic models.

CONCLUSION

The present meta-analysis demonstrated that FASL and TRAIL polymorphisms were significantly associated with susceptibility to IDD in Chinese Han population.

LEVEL OF EVIDENCE

1.

Cellular senescence in intervertebral disc aging and degeneration

Purpose

Age is a major risk factor for multiple disease pathologies, including chronic back pain, which stems from age-related degenerative changes to intervertebral disc tissue. Growing evidence suggest that the change in phenotype of disc cells to a senescent phenotype may be one of the major driving forces of age-associated disc degeneration. This review discusses the known stressors that promote development of senescence in disc tissue and the underlying molecular mechanisms disc cells adopt to enable their transition to a senescent phenotype.

Recent findings

Increased number of senescent cells have been observed with advancing age and degeneration in disc tissue. Additionally, in vitro studies have confirmed the catabolic nature of stress-induced senescent disc cells. Several factors have been shown to establish senescence via multiple different underlying mechanisms.

Summary

Cellular senescence can serve as a therapeutic target to combat age-associated disc degeneration. However, whether the different stressors utilizing different signaling networks establish different kinds of senescent types in disc cells is currently unknown and warrants further investigation.

Association between GDF5 rs143383 genetic polymorphism and musculoskeletal degenerative diseases susceptibility: a meta-analysis

BACKGROUND

Several studies have assessed the association between GDF5 rs143383 polymorphism and the susceptibility of musculoskeletal degenerative diseases, such as intervertebral disc degeneration (IDD) and osteoarthritis (OA), but the results are inconsistent. The aim of our study was to evaluate the association between them comprehensively.

METHODS

A systematical search was conducted on PubMed, Scopus, Web of Science (WOS), Embase, and the Cochrane Library databases updated to April 20, 2018. Eligible studies about polymorphisms in GDF5 gene and risk of IDD or OA were included. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were utilized.

RESULTS

Fifteen studies with a total of 5915 cases and 12,252 controls were finally included in our study. Meta-analysis of GDF5 rs143383 polymorphism was statistically associated with increased risk of musculoskeletal degenerative diseases under each genetic model (allele model: OR = 1.32, 95% CI 1.19-1.48, P = 0.000; homozygote model: OR = 1.80, 95%CI 1.49-2.16, P = 0.000; heterozygote model: OR = 1.37, 95%CI 1.21-1.55, P = 0.000; dominant model: OR = 1.56, 95%CI 1.39-1.75, P = 0.000; recessive model: OR = 1.39, 95%CI 1.20-1.60, P = 0.000). Stratified analyses based on disease type showed a significant association between the GDF5 rs143383 polymorphism and increased risk of IDD and OA under all genetic models studied. When stratified with ethnicity, pooled outcomes revealed that this polymorphism was significantly related with increased risk of musculoskeletal degenerative diseases in both Asian and Caucasian populations under all genetic models studied.

CONCLUSIONS

The present study suggested that GDF5 rs143383 polymorphism was significantly associated with susceptibility to musculoskeletal degenerative diseases.

Collagen IX gene polymorphisms and lumbar disc degeneration: a systematic review and meta-analysis

Background

An increasing number of studies have investigated associations between collagen IX alpha 2 chain (COL9A2) and collagen IX alpha 3 chain (COL9A3) gene polymorphisms and the risk of lumbar disc degeneration (LDD). However, these studies have yielded contradictory results. The purpose of this meta-analysis is to investigate the association between the collagen IX gene polymorphisms (rs12077871, rs12722877, rs7533552 in COL9A2; rs61734651 in COL9A3) and LDD.

Methods

All relevant articles were collected from PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI). The last electronic search was performed on September 1, 2017. The allele/genotype frequencies were extracted from each study. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength of associations under the five comparison genetic models. Statistical analysis was performed by Review Manager (RevMan) 5.31 software.

Results

The meta-analysis of 10 case-control studies, including 2102 LDD cases and 2507 controls, indicated that COL9A2 gene (rs12077871, rs12722877, rs7533552) and COL9A3 gene (rs61734651) polymorphisms were not associated with LDD (rs12077871: T vs. C, OR = 1.85, 95% CI = 0.87–3.91, P = 0.11; rs12722877: G vs. C, OR = 0.83, 95% CI = 0.69–1.01, P = 0.06; rs7533552: G vs. A, OR = 1.11, 95% CI = 0.98–1.25, P = 0.09; rs61734651: T vs. C, OR = 1.57, 95% CI = 0.51–4.84, P = 0.43). The Egger text and the Begg funnel plot did not show any evidence of publication bias.

Conclusion

rs12077871, rs12722877, and rs7533552 variants in COL9A2 and rs61734651 variant in COL9A3 were not significantly associated with a predisposition to LDD. Large-scale and well-designed studies are needed to confirm this conclusion.

Genetic background of degenerative disc disease in the lumbar spine

This is a review paper on the topic of genetic background of degenerative disc diseases in the lumbar spine. Lumbar disc diseases (LDDs), such as lumbar disc degeneration and lumbar disc herniation, are the main cause of low back pain. There are a lot of studies that tried to identify the causes of LDDs. The causes have been categorized into environmental factors and genetic factors. Recent studies revealed that LDDs are mainly caused by genetic factors. Numerous studies have been carried out using the genetic approach for LDDs. The history of these studies is divided into three periods: (1) era of epidemiological research using familial background and twins, (2) era of genomic research using DNA polymorphisms to identify susceptible genes for LDDs, and (3) era of functional research to determine how the genes cause LDDs. This review article was undertaken to present the history of genetic approach to LDDs and to discuss the current issues and future perspectives.

TRAIL gene 1595C/T polymorphisms contribute to the susceptibility and severity of intervertebral disc degeneration: a data synthesis

Background

Studies have investigated the correlation between tumor necrosis factor related apoptosis-inducing ligand (TRAIL) gene polymorphisms and the susceptibility and severity of intervertebral disc degeneration (IDD), but the results were inconsistent. To evaluate the specific relationship, we performed a meta-analysis to clarify the controversies.

Methods

Four databases were searched, and the pooled results were presented as odds ratios (ORs) with 95% confidence intervals (CIs).

Results

Three case-control studies from Han Chinese were included (565 cases and 427 controls). All the included studies reported TRAIL 1595C/T gene polymorphisms. The recessive model (CC vs. CT + TT) was the optimal model, which demonstrated a significant relationship between 1595C/T polymorphisms and increased IDD risk (OR = 2.18, 1.45 to 3.27, P = 0.000). No significant heterogeneity was found in the recessive model (I² = 48.6%, P = 0.143). Patients with lower grade IDD had more genotypes or alleles including 1595TT genotype (grade II vs. grade III: OR = 2.12, 1.18 to 3.83, P = 0.012; grade III vs. grade IV: OR = 2.59, 1.29 to 5.22, P = 0.007) and 1595 T allele (grade II vs. grade III: OR = 1.91, 1.43 to 2.55, P = 0.000; grade II vs. grade IV: OR = 2.46, 0.94 to 1.76, P = 0.000).

Conclusions

There is a significant relationship between 1595C/T polymorphisms and the susceptibility and severity of IDD in Han Chinese. Patients with lower grade IDD had higher frequency of the 1595TT genotype and 1595 T allele.

Electronic supplementary material

The online version of this article (doi: 10.1186/s12891-017-1916-3) contains supplementary material, which is available to authorized users.

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.

Lumbar Disc Herniation

PURPOSE OF REVIEW

Substantial advancements have been made in the cause, diagnosis, imaging, and treatment options available for patients with lumbar disc herniation (LDH). We examined the current evidence and highlight the concepts on the frontline of discovery in LDH.

RECENT FINDINGS

There are a myriad of novel etiologies of LDH detailed in recent literature including inflammatory factors and infectious microbes. In the clinical setting, recent data focuses on improvements in computer tomography as a diagnostic tool and non-traditional injection options including tumor necrosis alpha inhibitors and platelet-rich plasma. Operative treatment outcomes have focused on minimally invasive endoscopic approaches and demonstrated robust 5-year post-operative outcomes. Advances in the molecular etiology of LDH will continue to drive novel treatment options. The role of endoscopic treatment for LDH will continue to evolve. Further research into10-year outcomes will be necessary as this surgical approach continues to gain widespread popularity.

Bedside to bench and back to bedside: Translational implications of targeted intervertebral disc therapeutics

Spinal pain and associated disability is a leading cause of morbidity worldwide that has a strong association with degenerative disc disease (DDD). DDD can begin in early–late adolescence and has a variable course. Biologically based therapies to treat DDD face significant challenges posed by the unique milieu of the environment within the intervertebral discs. Many potential promising therapies are still in the early stages of development with a hostile microenvironment within the disc presenting unique challenges.

The translational potential of this article: Patient selection, reasonable therapeutic goals, approach, and timing will need to be discerned in order to successfully translate potential therapeutics.

Genome-Wide Identification of Long Noncoding RNAs in Human Intervertebral Disc Degeneration by RNA Sequencing

Long noncoding RNAs (lncRNAs) are emerging as crucial players in a myriad of biological processes. However, the precise mechanism and functions of most lncRNAs are poorly characterized. In this study, we presented genome-wide identification of lncRNAs in the patients with intervertebral disc degeneration (IDD) and spinal cord injury (control) using RNA sequencing (RNA-seq). A total of 124.6 million raw reads were yielded using Hiseq 2500 platform and approximately 88% clean reads could be aligned to human reference genome in both IDD and control groups. RNA-seq profiling indicated that 1,854 lncRNAs were differentially expressed (log2 fold change ≥ 1 or ≤−1, p < 0.05), in which 1,530 could potentially target 6,386 genes via cis-regulatory effects. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis for these target genes suggested that lncRNAs were involved in diverse pathways, such as lysosome, focal adhesion, and MAPK signaling. In addition, a competing endogenous RNA (ceRNA) network was constructed for analyzing the function of lncRNAs. Further, quantitative real time PCR (qRT-PCR) was used to confirm the differentially expressed lncRNAs and ceRNA network. In conclusion, our results present the first global identification of lncRNAs in IDD and may provide candidate diagnostic biomarkers for IDD treatment.