Association between the -1306C/T polymorphism of matrix metalloproteinase-2 gene and lumbar disc disease in Chinese young adults

Pathogenesis and therapeutic implications of matrix metalloproteinases in intervertebral disc degeneration: A comprehensive review

Intervertebral disc (IVD) degeneration (IDD) is a common disorder that affects the spine and is a major cause of lower back pain (LBP). The extracellular matrix (ECM) is the structural foundation of the biomechanical properties of IVD, and its degradation is the main pathological characteristic of IDD. Matrix metalloproteinases (MMPs) are a group of endopeptidases that play an important role in the degradation and remodeling of the ECM. Several recent studies have shown that the expression and activity of many MMP subgroups are significantly upregulated in degenerated IVD tissue. This upregulation of MMPs results in an imbalance of ECM anabolism and catabolism, leading to the degradation of the ECM and the development of IDD. Therefore, the regulation of MMP expression is a potential therapeutic target for the treatment of IDD. Recent research has focused on identifying the mechanisms by which MMPs cause ECM degradation and promote IDD, as well as on developing therapies that target MMPs. In summary, MMP dysregulation is a crucial factor in the development of IDD, and a deeper understanding of the mechanisms involved is needed to develop effective biological therapies that target MMPs to treat IDD.

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

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.

Investigation of multiple populations highlight VEGFA polymorphisms to modulate anterior cruciate ligament injury

Polymorphisms in VEGFA and KDR encoding proteins have been associated with anterior cruciate ligament (ACL) injury risk. We leveraged a collective sample from Sweden, Poland, and Australia to investigate the association of functional polymorphisms in VEGFA and KDR with susceptibility to ACL injury risk. Using a case-control genetic association approach, polymorphisms in VEGFA and KDR were genotyped and haplotypes inferred from 765 controls, and 912 cases clinically diagnosed with ACL rupture. For VEGFA, there was a significant overrepresentation of the rs2010963 CC genotype (p = 0.0001, false discovery rate [FDR]: p = 0.001, odds ratio [OR]: 2.16, 95% confidence interval [CI]: 1.47-3.19) in the combined ACL group (18%) compared to the combined control group (11%). The VEGFA (rs699947 C/A, rs1570360 G/A, rs2010963 G/C) A-A-G haplotype was significantly (p = 0.010, OR: 0.85, 95% CI: 0.69-1.05) underrepresented in the combined ACL group (23%) compared to the combined control group (28%). In addition, the A-G-G construct was significantly (p = 0.036, OR: 0.81, 95% CI: 0.64-1.02) underrepresented in the combined ACL group (12%) compared to the combined CON group (16%). Our findings support the association of the VEGFA rs2010963 CC genotype with increased risk and (ii) the VEGFA A-A-G haplotype with a reduced risk, and are in alignment with the a priori hypothesis. Collectively identifying a genetic interval within VEGFA to be implicated in ACL risk modulation and highlight further the importance of vascular regulation in ligament biology.

Genetic Predictors of Early-Onset Spinal Intervertebral Disc Degeneration: Part One of Two

Intervertebral disc (IVD) degeneration is a progressive and painful pathology that can root from mechanical, biochemical, and environmental stressors. However, recent advancements in biogenetics have now found a predominating genetic influence. Nevertheless, despite these advancements, the pathophysiology of IVD degeneration remains poorly understood. In the first of our two-part series, we will characterize some of the most recent and best-studied genes in the context of intervertebral disc degeneration. We will attempt to formulate the first contemporary gene guide that characterizes the genetic profile of IVD degeneration. The genes of interest include aggrecan (ACAN), matrix metalloproteinase 2 (MMP2), vitamin D receptor (VDR), interleukin 1 alpha (IL1A), and those encoded for collagens such as collagen type XI alpha 1 chain (COL11A1), collagen type I alpha 1 chain (COL1A1), collagen type IX alpha 2 chain (COL9A2), and collagen type IX alpha 3 chain (COL9A3). Genetic analysis studies reveal that these genes play vital roles in maintaining the structural integrity of the intervertebral disc, activating enzymes involved in the extracellular matrix, and promoting connective tissue formation. Nevertheless, characterizing these genes alone is not enough to understand the pathophysiology of IVD degeneration. Therefore, further studies are warranted to understand molecular signalling pathways of IVD degeneration better and ultimately create more sophisticated genetic and cell-based therapies to improve patient outcomes.

Risk Factors of Intervertebral Disc Pathology-A Point of View Formerly and Today-A Review

Intervertebral disc pathology is a common disorder that can be caused by genetic, mechanical, and behavioral factors; however, it is possible to slow its progression. Although environmental and behavioral factors were previously considered to be the sole causes of intervertebral disc pathologies such as disc herniation, recent studies have shown that genetic factors also play an important role. This review compares the perception of major risk factors from the last and present centuries. It also examines individual genetic and non-genetic factors acting as risk factors, as well as some approaches for preventing intervertebral disc pathologies, and compares available statistics regarding disc herniation.

Can Implementation of Genetics and Pharmacogenomics Improve Treatment of Chronic Low Back Pain?

Etiology of back pain is multifactorial and not completely understood, and for the majority of people who suffer from chronic low back pain (cLBP), the precise cause cannot be determined. We know that back pain is somewhat heritable, chronic pain more so than acute. The aim of this review is to compile the genes identified by numerous genetic association studies of chronic pain conditions, focusing on cLBP specifically. Higher-order neurologic processes involved in pain maintenance and generation may explain genetic contributions and functional predisposition to formation of cLBP that does not involve spine pathology. Several genes have been identified in genetic association studies of cLBP and roughly, these genes could be grouped into several categories, coding for: receptors, enzymes, cytokines and related molecules, and transcription factors. Treatment of cLBP should be multimodal. In this review, we discuss how an individual's genotype could affect their response to therapy, as well as how genetic polymorphisms in CYP450 and other enzymes are crucial for affecting the metabolic profile of drugs used for the treatment of cLBP. Implementation of gene-focused pharmacotherapy has the potential to deliver select, more efficacious drugs and avoid unnecessary, polypharmacy-related adverse events in many painful conditions, including cLBP.

Alterations in ECM signature underscore multiple sub-phenotypes of intervertebral disc degeneration

The intervertebral disc is a specialized connective tissue critical for absorption of mechanical loads and providing flexibility to the spinal column. The disc ECM is complex and plays a vital role in imparting tissue its biomechanical function. The central NP is primarily composed of large aggregating proteoglycans (PGs) while surrounding AF is composed of fibrillar collagens, I and II. Aggrecan and versican in particular, due to their high concentration of sulfated GAG chains form large aggregates with hyaluronic acid (HA) and provide water binding capacity to the disc. Degradation of aggrecan core protein due to aggrecanase and MMP activity, SNPs that affect number of chondroitin sulfate (CS) substitutions and alteration in enzymes critical in synthesis of CS chains can impair the aggrecan functionality. Similarly, levels of many matrix and matrix-related molecules e.g. Col2, Col9, HAS2, ccn2 are dysregulated during disc degeneration and genetic animal models have helped establish causative link between their expression and disc health. In the degenerating and herniated discs, increased levels of inflammatory cytokines such as TNF-α, IL-1β and IL-6 are shown to promote matrix degradation through regulating expression and activity of critical proteases and stimulate immune cell activation. Recent studies of different mouse strains have better elucidated the broader impact of spontaneous degeneration on disc matrix homeostasis. SM/J mice showed an increased cell apoptosis, loss of cell phenotype, and cleavage of aggrecan during early stages followed by tissue fibrosis evident by enrichment of several collagens, SLRPs and fibronectin. In summary, while disc degeneration encompasses wide spectrum of degenerative phenotypes extensive matrix degradation and remodeling underscores all of them.

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The intervertebral disc absorbs loads and provides flexibility to the spine.

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The ECM is complex and vital for imparting tissue its biomechanical function.

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Numerous types of proteoglycans and collagens designate the quality of the disc.

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Many matrix and matrix-related molecules are dysregulated during disc degeneration.

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Matrix degradation and remodeling underscores wide spectrum of phenotype.

Pathomechanism of intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the main contributor to low back pain, which is a leading cause of disability worldwide. Although substantial progress has been made in elucidating the molecular mechanisms of IDD, fundamental and long-lasting treatments for IDD are still lacking. With increased understanding of the complex pathomechanism of IDD, alternative strategies for treating IDD can be discovered. A brief overview of the prevalence and epidemiologic risk factors of IDD is provided in this review, followed by the descriptions of anatomic, cellular, and molecular structure of the intervertebral disc as well as the molecular pathophysiology of IDD. Finally, the recent findings of intervertebral disc progenitors are reviewed and the future perspectives are discussed.

The impact of changes in serum levels of metalloproteinase-2 and metalloproteinase-9 on pain perception in patients with disc herniation before and after surgery

Purpose: The aim of our research was to investigate the link between serum levels of metalloproteinase-2 (MMP-2) and MMP-9, and the degree of pain experienced before and 1 and 3 months after microdiscectomy in 70 patients with disc herniation (DH). Patients and methods: The control group (group C) consisted of 70 healthy subjects and the DH group consisted of 70 patients with sciatica pain caused by lumbar DH. Before (DH0) and 1 and 3 months after surgery, the patients were assessed in terms of the following biochemical parameters: MMP-2, tissue inhibitors of metalloproteinases-2 (TIMP-2), MMP-2/TIMP-2, MMP-9, TIMP-1, and MMP-9/TIMP1, and the following clinical parameters: Numeric Rating Scale for the back (NRS-B) and the leg (NRS-L) and the Pain Rating Index (PRI) and Present Pain Intensity (PPI) of the McGill Pain Questionnaire. Results: No statistically significant correlations were observed following the biochemical and clinical assessments performed in group C and the DH group before surgery. After surgery (1 month), higher levels of TIMP-1 correlated with higher levels of NRS-B (rs =0.27; p<0.05). At 3 months after surgery higher levels of TIMP-2 and lower levels of MMP-2/TIMP-2 were correlated with higher levels of NRS-L (rs =0.27, p<0.05 and rs =-0.31, p<0.05, respectively) and higher levels of TIMP-2 were correlated with higher PRI scores (rs =0.27; p<0.005) and PPI scores (rs =0.35; p<0.01). Conclusion: The results showed that MMPs are involved in DH and play a significant role in the perception of pain after DH surgery. However, the value of MMPs as a potential therapeutic target in pain treatment should be considered cautiously.

The Evaluation of Proteoglycan Levels and the Possible Role of ACAN Gene (c.6423T>C) Variant in Patients with Lumbar Disc Degeneration Disease

BACKGROUND/AIM

The present study aimed to investigate the role of an aggrecan (ACAN) gene variant and proteoglycan levels in the risk of lumbar degenerative disc disease (LDDD).

MATERIALS AND METHODS

A total of 108 patients with LDDD and 103 healthy controls were enrolled. Molecular assessment of the ACAN gene (c.6423T>C) variant was determined by real time-polymerase chain reaction. Proteoglycan levels in serum were measured with enzyme-linked immunosorbent assay.

RESULTS

The frequency of all alleles and genotypes in all study groups were distributed according to the Hardy-Weinberg equilibrium. In addition, no association between the ACAN gene (c.6423T>C) variant and presence of risk factors for LDDD was detected. However, proteoglycan levels were significantly lower in patients with LDDD compared to the control group (p<0.00001).

CONCLUSION

Our findings suggest that proteoglycan has emerged as a potential novel biomarker which might be used for prediction of LDDD risk.

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.

Genetic Alterations in Intervertebral Disc Disease

BACKGROUND

Intervertebral disc degeneration (IVDD) is considered a multifactorial disease that is influenced by both environmental and genetic factors. The last two decades of research strongly demonstrate that genetic factors contribute about 75% of the IVDD etiology. Recent total genome sequencing studies have shed light on the various single-nucleotide polymorphisms (SNPs) that are associated with IVDD.

AIM

This review presents comprehensive and updated information about the diversity of genetic factors in the inflammatory, degradative, homeostatic, and structural systems involved in the IVDD. An organized collection of information is provided regarding genetic polymorphisms that have been identified to influence the risk of developing IVDD. Understanding the proteins and signaling systems involved in IVDD can lead to improved understanding and targeting of therapeutics.

MATERIALS AND METHODS

An electronic literature search was performed using the National Library of Medicine for publications using the keywords genetics of IVDD, lumbar disc degeneration, degenerative disc disease, polymorphisms, SNPs, and disc disease. The articles were then screened based on inclusion criteria that included topics that covered the correlation of SNPs with developing IVDD. Sixty-five articles were identified as containing relevant information. Articles were excluded if they investigated lower back pain or just disc herniation without an analysis of disc degeneration. This study focuses on the chronic degeneration of IVDs.

RESULTS

Various genes were identified to contain SNPs that influenced the risk of developing IVDD. Among these are genes contributing to structural proteins, such as COL1A1, COL9A3, COL9A3, COL11A1, and COL11A2, ACAN, and CHST3. Furthermore, various SNPs found in the vitamin-D receptor gene are also associated with IVDD. SNPs related to inflammatory cytokine imbalance are associated with IVDD, although some effects are limited by sex and certain populations. SNPs in genes that code for extracellular matrix-degrading enzymes, such as MMP-1, MMP-2, MMP-3, MMP-9, MMP-14, ADAMTS-4, and ADAMTS-5 are also associated with IVDD. Apoptosis-mediating genes, such as caspase 9 gene (CASP9), TRAIL, and death receptor 4 (DR4), as well as those for growth factors, such as growth differentiation factor 5 and VEGF, are identified to have polymorphisms that influence the risk of developing IVDD.

CONCLUSION

Within the last 10 years, countless new SNPs have been identified in genes previously unknown to be associated with IVDD. Furthermore, the last decade has also revealed new SNPs identified in genes already known to be involved with increased risk of developing IVDD. Improved understanding of the numerous genetic variants behind various pathophysiological elements of IVDD could help advance personalized care and pharmacotherapeutic strategies for patients suffering from IVDD in the future.

Genetic aspects of intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is one of the common causes of low back pain. Similar to many other multifactorial diseases, it is affected by environmental and genetic factors. Although not completely understood, genetic factors include a wide spectrum of variations, such as single nucleotide polymorphisms, which could play a significant role in the etiology of this disease. Besides, the interactions with environmental factors could make the role of genetic factors more complicated. Genetic variations in disc components could participate in developing degenerative disc disease through altering the normal homeostasis of discs. Gene polymorphisms in disc proteins (collagens I, II, III, IX, and XI), proteoglycans (aggrecan), cytokines (interleukins I, VI, and X), enzymes (matrix metalloproteinases II, III, and IX), and vitamin D receptor seem to play considerable roles in the pathology of this disease. There are also many other investigated genes that could somehow take part in the process. However, it seems that more studies are needed to clarify the exact role of genetics in IVDD.

Genetic Factors in Intervertebral Disc Degeneration

Low back pain (LBP) is a major cause of disability and imposes huge economic burdens on human society worldwide. Among many factors responsible for LBP, intervertebral disc degeneration (IDD) is the most common disorder and is a target for intervention. The etiology of IDD is complex and its mechanism is still not completely understood. Many factors such as aging, spine deformities and diseases, spine injuries, and genetic factors are involved in the pathogenesis of IDD. In this review, we will focus on the recent advances in studies on the most promising and extensively examined genetic factors associated with IDD in humans. A number of genetic defects have been correlated with structural and functional changes within the intervertebral disc (IVD), which may compromise the disc's mechanical properties and metabolic activities. These genetic and proteomic studies have begun to shed light on the molecular basis of IDD, suggesting that genetic factors are important contributors to the onset and progression of IDD. By continuing to improve our understanding of the molecular mechanisms of IDD, specific early diagnosis and more effective treatments for this disabling disease will be possible in the future.

The role of matrix metalloproteinase 14 polymorphisms in susceptibility to intervertebral disc degeneration in the Chinese Han population

INTRODUCTION

Matrix metalloproteinase 14 (MMP14) plays an important role in the pathophysiology of intervertebral disc degeneration (IVDD). The present study aimed to determine whether two single nucleotide polymorphisms (-378 T/C and -364 G/T) of MMP14 were associated with the risk and severity of IVDD in the Chinese Han population.

MATERIAL AND METHODS

A total of 908 patients with IVDD and 906 healthy controls were enrolled in this study. The grade of disc degeneration was determined according to Schneiderman's classification for magnetic resonance imaging. The polymorphisms of MMP14 were genotyped using polymerase chain reaction and direct sequencing.

RESULTS

The genotype distribution of -364G/T did not show a significant difference between IVDD patients and healthy controls. The frequencies of the -378T/C and CC genotypes were significantly lower among IVDD patients compared with healthy controls (p < 0.001); unconditional logistic regression analysis revealed that the CT and CC genotypes were significantly associated with a decreased risk of IVDD compared with the TT genotype (p < 0.001). Patients with IVDD showed significantly higher frequencies of the T allele at -378T/C than healthy controls (p < 0.001). In addition, the -375 CC genotype, as well as the C allele, was associated with lower degenerative grades of IVDD compared with the TT genotype and the T allele, respectively (both p < 0.001).

CONCLUSIONS

The -378T/C polymorphism of MMP14 may be associated with the risk and severity of IVDD in the Chinese Han population. It shows potential to become a biomarker to predict risk and severity of IVDD.

MMPs and ADAMTSs in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the most common diagnosis in patients with low back pain, a leading cause of musculoskeletal disability worldwide. The major components of extracellular matrix (ECM) within the discs are type II collagen (Col II) and aggrecan. Excessive destruction of ECM, especially loss of Col II and aggrecan, plays a critical role in promoting the occurrence and development of IDD. Matrix metalloproteinases (MMPs) and a disintegrin and metalloprotease with thrombospondin motifs (ADAMTSs) are primary enzymes that degrade collagens and aggrecan. There is a large and growing body of evidence that many members of MMPs and ADAMTSs are highly expressed in degenerative IVD tissue and cells, and are closely involved in ECM breakdown and the process of disc degeneration. In contrast, targeting these enzymes has shown promise for promoting ECM repair and mitigating disc regeneration. In the current review, after a brief description regarding the biology of MMPs and ADAMTSs, we mainly focus on their expression profiles, roles and therapeutic potential in IDD. A greater understanding of the catabolic pathways involved in IDD will help to develop potential prophylactic or regenerative biological treatment for degenerative disc disease in the future.

Expression of matrix metalloproteinases is positively related to the severity of disc degeneration and growing age in the East Asian lumbar disc herniation patients

Matrix metalloproteinases (MMPs) have been known to play a pivotal role in the age- and/or disease-related degradation of intervertebral discs. We aimed to explore as to whether the expression of these enzymes is correlated to disc degeneration caused by increasing age and severity of herniation in the East Asian population. Thus, we studied the expressions of MMP-1 (collagenase), MMP-2 (gelatinase) and MMP-14 (membrane-type protease) in 65 patients diagnosed with lumbar disc herniation. The patients were divided into 3 groups according to their age, and the severity of herniation was graded on the basis of magnetic resonance imaging (MRI). Immunohistochemistry analysis was conducted to determine the expression of different MMPs in the post-surgery disc specimens. The results showed that expressions of these three enzymes were directly and positively related to the degree of disc degradation. Whereas, the MMP-1 expression was found to be elevated with the increasing age, the MMP-2 and MMP-14 remained unchanged in groups of different ages. A direct correlation between the expressions of MMP-2 and MMP-14 suggested a role of MMP-14 in the modulation of MMP-2 expression.

A preliminary association study of fat mass and obesity associated gene polymorphisms and degenerative disc disease in a Chinese Han population

OBJECTIVE

To assess whether polymorphisms of the fat mass and obesity associated gene (FTO) are associated with the presence and severity of degenerative disc disease (DDD) in a Chinese Han population.

METHODS

In this case-control study, patients with DDD and controls matched for age, sex and body mass index were genotyped for six single nucleotide polymorphisms (SNPs) of FTO. Disease severity was measured using the Japanese Orthopaedic Association score. Allelic, genotypic and genotype-phenotype association analyses were performed.

RESULTS

A total of 80 patients with DDD and 80 controls were studied. All six SNPs were in Hardy-Weinberg equilibrium. The frequencies of allele G and genotype G/G of the SNP rs11076008 were significantly associated with DDD after Bonferroni correction. No associations were shown between the SNPs studied and sex or disease severity.

CONCLUSION

The SNP rs11076008 of FTO may play an important role in the development of DDD in a Chinese Han population. The G/G genotype and/or G allele may be a risk factor for DDD. These results suggest that FTO is a DDD predisposition gene and may support a close relationship between obesity and DDD.

Genetic polymorphisms associated with intervertebral disc degeneration

BACKGROUND CONTEXT

Disc degeneration (DD) is a multifaceted chronic process that alters the structure and function of the intervertebral discs and can lead to painful conditions. The pathophysiology of degeneration is not well understood, but previous studies suggest that certain genetic polymorphisms may be important contributing factors leading to an increased risk of DD.

PURPOSE

To review the genetic factors in DD with a focus on polymorphisms and their putative role in the pathophysiology of degeneration. Elucidating the genetic components that are associated with degeneration could provide insights into the mechanism of the process. Furthermore, defining these relationships and eventually using them in a clinical setting may allow an identification and early intervention for those who are at a high risk for painful DD.

STUDY DESIGN

Literature review.

METHODS

This literature review focused on the studies concerning genetic polymorphisms and their associations with DD.

RESULTS

Genetic polymorphisms in 20 genes have been analyzed in association with DD, including vitamin D receptor, growth differentiation factor 5 (GDF5), aggrecan, collagen Types I, IX, and XI, fibronectin, hyaluronan and proteoglycan link protein 1 (HAPLN1), thrombospondin, cartilage intermediate layer protein (CILP), asporin, MMP1, 2, and 3, parkinson protein 2, E3 ubiquitin protein ligase (PARK2), proteosome subunit β type 9 (PSMB9), tissue inhibitor of metalloproteinase (TIMP), cyclooxygenase-2 (COX2), and IL1α, IL1β, and IL6. Each genetic polymorphism codes for a protein that has a functional role in the pathogenesis of DD.

CONCLUSIONS

There are known associations between several genetic polymorphisms and DD. Of the 20 genes analyzed, polymorphisms in vitamin D receptor, aggrecan, Type IX collagen, asporin, MMP3, IL1, and IL6 show the most promise as functional variants. Genetic studies are crucial for understanding the mechanism of the degeneration. This genetic information could eventually be used as a predictive model for determining a patient's risk for symptomatic DD.

Expression and regulation of metalloproteinases and their inhibitors in intervertebral disc aging and degeneration

BACKGROUND CONTEXT

Destruction of extracellular matrix (ECM) leads to intervertebral disc degeneration (IDD), which underlies many spine-related disorders. Matrix metalloproteinases (MMPs), and disintegrins and metalloproteinases with thrombospondin motifs (ADAMTSs) are believed to be the major proteolytic enzymes responsible for ECM degradation in the intervertebral disc (IVD).

PURPOSE

To summarize the current literature on gene expression and regulation of MMPs, ADAMTSs, and tissue inhibitors of metalloproteinases (TIMPs) in IVD aging and IDD.

METHODS

A comprehensive literature review of gene expression of MMP, ADAMTS, and TIMP in human IDD and reported studies on regulatory factors controlling their expressions and activities in both human and animal model systems.

RESULTS

Upregulation of specific MMPs (MMP-1, -2, -3, -7, -8, -10, and -13) and ADAMTS (ADAMTS-1, -4, and -15) were reported in human degenerated IVDs. However, it is still unclear from conflicting published studies whether the expression of ADAMTS-5, the predominant aggrecanase, is increased with IDD. Tissue inhibitors of metalloproteinase-3 is downregulated, whereas TIMP-1 is upregulated in human degenerated IVDs relative to nondegenerated IVDs. Numerous studies indicate that the expression levels of MMP and ADAMTS are modulated by a combination of many factors, including mechanical, inflammatory, and oxidative stress, some of which are mediated in part through the p38 mitogen-activated protein kinase pathway. Genetic predisposition also plays an important role in determining gene expression of MMP-1, -2, -3, and -9.

CONCLUSIONS

Upregulation of MMP and ADAMTS expression and enzymatic activity is implicated in disc ECM destruction, leading to the development of IDD. Future IDD therapeutics depends on identifying specific MMPs and ADAMTSs whose dysregulation result in pathological proteolysis of disc ECM.

Single-nucleotide gene polymorphisms involving cell death pathways: a study of Chinese patients with lumbar disc herniation

OBJECTIVE

To evaluate the effect of polymorphisms of death pathway genes FAS and FASL on the risk of developing lumbar disc herniation (LDH) in a Northern Chinese population.

BACKGROUND DATA

The FAS receptor-ligand system plays a key role to regulate apoptosis of cell. There is evidence that the apoptosis-mediated FAS receptor-ligand system is involved in the pathogenesis of disc degeneration. Some research considered single-nucleotide polymorphisms of FAS-1377G/A, FAS-670A/G, FASL-844T/C, and FASL INV2nt-124A/G may increase the risk of developing cancer. We therefore assess these four single-nucleotide polymorphisms as candidate susceptibility for LDH.

METHODS

A total of 475 patients with LDH and 533 control subjects were selected. Genotypes were determined by polymerase chain reaction-based restriction fragment length polymorphism and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Associations with the risk of LDH were estimated by logistic regression model.

RESULTS

Significant differences were found in genotypic distributions between cases and controls for FASL-844T/C, but not for other three polymorphisms. When compared with CC genotype, subjects with the TT genotype had a higher risk to develop LDH (odds ratio = 3.12; 95% confidence interval: 1.73-5.40). Moreover, an association was found between this genotype of FASL-844TT and more severe grades of disc degeneration. We observed statistically significant interactions between polymorphisms of FASL-844T/C and lumbar load, tobacco smoking, and age.

CONCLUSION

Genetic polymorphisms of FASL-844T/C may be associated with an increased risk of developing disc degeneration and LDH.

Genetic association studies in lumbar disc degeneration: a systematic review

Objective

Low back pain is associated with lumbar disc degeneration, which is mainly due to genetic predisposition. The objective of this study was to perform a systematic review to evaluate genetic association studies in lumbar disc degeneration as defined on magnetic resonance imaging (MRI) in humans.

Methods

A systematic literature search was conducted in MEDLINE, MEDLINE In-Process, SCOPUS, ISI Web of Science, The Genetic Association Database and The Human Genome Epidemiology Network for information published between 1990–2011 addressing genes and lumbar disc degeneration. Two investigators independently identified studies to determine inclusion, after which they performed data extraction and analysis. The level of cumulative genetic association evidence was analyzed according to The HuGENet Working Group guidelines.

Results

Fifty-two studies were included for review. Forty-eight studies reported at least one positive association between a genetic marker and lumbar disc degeneration. The phenotype definition of lumbar disc degeneration was highly variable between the studies and replications were inconsistent. Most of the associations presented with a weak level of evidence. The level of evidence was moderate for ASPN (D-repeat), COL11A1 (rs1676486), GDF5 (rs143383), SKT (rs16924573), THBS2 (rs9406328) and MMP9 (rs17576).

Conclusions

Based on this first extensive systematic review on the topic, the credibility of reported genetic associations is mostly weak. Clear definition of lumbar disc degeneration phenotypes and large population-based cohorts are needed. An international consortium is needed to standardize genetic association studies in relation to disc degeneration.

An Association Study of Interleukin 18 Receptor Genes (IL18R1 and IL18RAP) in Lumbar Disc Degeneration

Objectives:

To examine association of candidate genetic variants in structural, inflammatory, matrix modifying, vitamin D receptor genes and variants associated with osteoarthritis, with surgical candidates and surgical patients with lumbar disc degeneration (LDD), in light of their previously reported susceptibility for LDD.

Methods:

Genotyping of 146 Norwegian LDD patients and 188 Norwegian controls was performed for 20 single-nucleotide polymorphisms (SNPs) from collagen, aggrecan, interleukin, VDR, MMP3 and COX2 genes and 7 SNPs from osteoarthritic genes.

Results:

The neighboring genes IL18R1 and IL18RAP polymorphisms (rs2287037 and rs1420100), showed a statistically non-significant risk for developing LDD (OR 1.36 [95 % CI 0.99 – 1.87]; p=0.06 and OR 1.33 [95 % CI 0.98-1.81]; p=0.07). Homozygosity of these risk alleles was associated with LDD (p=0.023 and p=0.027). The non-risk alleles at these SNPs were situated on a haplotype negatively associated with LDD (p=0.008). Carriage of at least one non-risk allele at both loci also reduces the risk of developing LDD (OR 0.51 [95 % CI 0.33-0.80]; p=0.003).

Conclusion:

Our findings support the polygenic nature of LDD and suggest that variation in interleukin 18 receptor genes could affect the risk of severe LDD and associated low back pain.

Rat tail static compression model mimics extracellular matrix metabolic imbalances of matrix metalloproteinases, aggrecanases, and tissue inhibitors of metalloproteinases in intervertebral disc degeneration

Introduction

The longitudinal degradation mechanism of extracellular matrix (ECM) in the interbertebral disc remains unclear. Our objective was to elucidate catabolic and anabolic gene expression profiles and their balances in intervertebral disc degeneration using a static compression model.

Methods

Forty-eight 12-week-old male Sprague-Dawley rat tails were instrumented with an Ilizarov-type device with springs and loaded statically at 1.3 MPa for up to 56 days. Experimental loaded and distal-unloaded control discs were harvested and analyzed by real-time reverse transcription-polymerase chain reaction (PCR) messenger RNA quantification for catabolic genes [matrix metalloproteinase (MMP)-1a, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5], anti-catabolic genes [tissue inhibitor of metalloproteinases (TIMP)-1, TIMP-2, and TIMP-3], ECM genes [aggrecan-1, collagen type 1-α1, and collagen type 2-α1], and pro-inflammatory cytokine genes [tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, and IL-6]. Immunohistochemistry for MMP-3, ADAMTS-4, ADAMTS-5, TIMP-1, TIMP-2, and TIMP-3 was performed to assess their protein expression level and distribution. The presence of MMP- and aggrecanase-cleaved aggrecan neoepitopes was similarly investigated to evaluate aggrecanolytic activity.

Results

Quantitative PCR demonstrated up-regulation of all MMPs and ADAMTS-4 but not ADAMTS-5. TIMP-1 and TIMP-2 were almost unchanged while TIMP-3 was down-regulated. Down-regulation of aggrecan-1 and collagen type 2-α1 and up-regulation of collagen type 1-α1 were observed. Despite TNF-α elevation, ILs developed little to no up-regulation. Immunohistochemistry showed, in the nucleus pulposus, the percentage of immunopositive cells of MMP-cleaved aggrecan neoepitope increased from 7 through 56 days with increased MMP-3 and decreased TIMP-1 and TIMP-2 immunopositivity. The percentage of immunopositive cells of aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with decreased TIMP-3 immunopositivity. In the annulus fibrosus, MMP-cleaved aggrecan neoepitope presented much the same expression pattern. Aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with increased ADAMTS-4 and ADAMTS-5 immunopositivity.

Conclusions

This rat tail sustained static compression model mimics ECM metabolic imbalances of MMPs, aggrecanases, and TIMPs in human degenerative discs. A dominant imbalance of MMP-3/TIMP-1 and TIMP-2 relative to ADAMTS-4 and ADAMTS-5/TIMP-3 signifies an advanced stage of intervertebral disc degeneration.

Genetics of the degenerated intervertebral disc

BACKGROUND

Given the genetic and proteomic advances of the past decade, understanding of the molecular etiopathogenesis of several complex diseases is increasing. Intervertebral disc disease (IVDD) is no different from other complex diseases where both environmental and genetic constituents are considered causes. This concept has challenged the traditional view that age, occupation, smoking, obesity, and primarily wear and tear are the only sources of disc degeneration.

METHODS

We conducted a systematic Medline review of the most current articles related to gene involvement in the development of IVDD in humans.

RESULTS

Candidate gene linkage and association studies involving the functional components of the intervertebral disc, including collagen I, collagen IX, collagen XI, aggrecan, extracellular matrix-degrading enzymes, inflammatory cytokines (IL-1, IL-6, and TNFα), Fas/FasL and vitamin D receptors, have had promising results.

CONCLUSIONS

This review emphasizes the latest advances in gene association with specific degenerated disc phenotypes, single nucleotide polymorphisms, disease heredity, and gene-environmental interactions in relation to IVDD to help improve future studies related to the genetic mechanisms underlying IVDD.

Genetics of lumbar disk degeneration: technology, study designs, and risk factors

Lumbar disk degeneration (LDD) is a common musculoskeletal condition. Genetic risk factors have been suggested to play a major role in its cause. This article reviews the main research strategies that have been used to study the genetics of LDD, and the genes that thus far have been identified to influence susceptibility to LDD. With the rapid progress in genomic technologies, further advances in the genetics of LDD are expected in the next few years.

Association of FAS and FAS ligand polymorphisms with the susceptibility and severity of lumbar disc degeneration in Chinese Han population

CONTEXT

Apoptosis is involved in the mechanism of lumbar disc degeneration (LDD).

OBJECTIVE

We aim to determine whether the polymorphisms of FAS and FASL are associated with the presence and severity of LDD.

METHODS

A total of 348 patients with LDD and 215 healthy controls were genotyped.

RESULTS

Patients with LDD showed higher frequency of-1377GA and AA, as well as-844CT and TT genotypes than normal controls. These genotypes were found to be associated with the risk of higher grades of LDD.

CONCLUSION

The polymorphisms of FAS and FASL may be associated with the presence and severity of LDD.

Association between Caspase-9 promoter region polymorphisms and discogenic low back pain

Caspase-9 (CASP-9) is an initiator caspase protease for apoptosis, and plays an important role in the development and progression of lumbar disc disease (LDD). The expression and/or activity of CASP-9 are significantly enhanced in the degenerated disc. The polymorphism in the promoter region of CASP-9 enhances the transcriptional activity of this gene, thereby modulating the susceptibility to LDD. The current study investigated the relationship between the CASP-9 -1263A/G (rs4645978) and -712C/T (rs4645981) polymorphisms and discogenic low back pain (LBP). The CASP-9 -1263A/G and -712C/T genotypes in this study were defined by polymerase chain reaction in 154 patients with discogenic LBP and 216 controls that were frequency-matched by age, gender, and occupation. The results showed that the CASP-9 -1263 GG genotype, compared with the AA and AG genotypes [odds ratio (OR) = 1.997, 95% confidence interval (95% CI) = 1.216-3.279, p = 0.006] or the AA genotype (OR = 2.760, 95% CI = 1.464-5.203, p = 0.002), is associated with a significant increased risk of discogenic LBP, but the -712 TT or TT and CT genotypes do not contribute to discogenic LBP compared with the CC genotype (OR = 0.547, 95% CI = 0.200-1.494, p = 0.234 and OR = 0.669, 95% CI = 0.439-1.021, p = 0.062, respectively). These results indicated that the CASP-9 -1263A/G polymorphism is associated with a high risk of discogenic LBP.

Metalloproteinases and their inhibitors-diagnostic and therapeutic opportunities in orthopedics

Matrix metalloproteinases (MMPs) and related enzymes (ADAMs, ADAMTS) and their inhibitors control matrix turnover and function. Recent advances in our understanding of musculoskeletal conditions such as tendinopathy, arthritis, Dupuytren's disease, degenerative disc disease, and bone and soft tissue healing suggest that MMPs have prominant roles. Importantly, MMPs are amenable to inhibition by cheap, safe, and widely available drugs such as the tetracycline antibiotics and the bisphosphonates. This indicates that these MMP inhibitors, if proven effective for any novel indication, may be quickly brought into clinical practice.

Association between the -1562 C/T polymorphism of matrix metalloproteinase-9 gene and lumbar disc disease in the young adult population in North China

Many studies have demonstrated that matrix metalloproteinase-9(MMP-9) is involved in the development of lumbar disc disease (LDD). The expression and activity of MMP-9 are significantly enhanced in degenerative discs. The polymorphism -1562C/T in the promoter region of MMP-9 gene alters the transcriptional activity of this gene. In this study we assessed the relationship between the -1562C/T polymorphism of matrix metalloproteinase-9 gene and the extent of degenerative disc disease in the young adult population in North China. Genotypes were defined by polymerase chain reaction and direct DNA sequencing in 408 young patients with LDD and 451 control subjects. The resulting genotypes were correlated with the presence of lumbar disc degeneration on MRI. The frequency of the MMP-9 -1562T genotype in patients with LDD was significantly higher than in healthy controls. Compared with CC genotype, subjects with the CT/TT genotype had a higher risk to develop LDD (odds ratio 2.14; 95% confidence interval 1.55-2.96). Moreover, an association was found between this genotype and more severe grades of disc degeneration observed on magnetic resonance imaging scan. These results indicated that the -1562C/T polymorphism of the MMP-9 gene is associated with a high risk of degenerative disc disease in the young adult population in North China.