Genetic polymorphisms associated with intervertebral disc degeneration

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.

Matrisome Profiling During Intervertebral Disc Development And Ageing

Intervertebral disc (IVD) degeneration is often the cause of low back pain. Degeneration occurs with age and is accompanied by extracellular matrix (ECM) depletion, culminating in nucleus pulpous (NP) extrusion and IVD destruction. The changes that occur in the disc with age have been under investigation. However, a thorough study of ECM profiling is needed, to better understand IVD development and age-associated degeneration. As so, iTRAQ LC-MS/MS analysis of foetus, young and old bovine NPs, was performed to define the NP matrisome. The enrichment of Collagen XII and XIV in foetus, Fibronectin and Prolargin in elder NPs and Collagen XI in young ones was independently validated. This study provides the first matrisome database of healthy discs during development and ageing, which is key to determine the pathways and processes that maintain disc homeostasis. The factors identified may help to explain age-associated IVD degeneration or constitute putative effectors for disc regeneration.

Inhibition of miR-27a suppresses the inflammatory response via the p38/MAPK pathway in intervertebral disc cells

The current study aimed to investigate the role of miR-27a in intervertebral disc degeneration (IDD) and to examine the underlying mechanisms. Quantitative polymerase chain reaction (qPCR) was performed to detect the expression level of miR-27a in the nucleus pulposus (NP) tissues of patients with IDD, and the results revealed an increasing expression of miR-27a in IDD compared with the control. To further investigate the role of miR-27a in IDD, a stable human NP cell line with low miR-27a expression was generated by transfecting cells with a lentiviral antigomiR-27a inhibitor. In addition, a human NP cell inflammation model was established by lipopolysaccharide (LPS; 10 µM) stimulation. The miR-27a expression in NP cells was determined by qPCR, while the expression of its target proteins; p-p38 and nuclear factor (NF-κB) was measured by western blot analysis. Furthermore, the mRNA and protein expression levels of proinflammatory factors, including interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α), were also evaluated by qPCR and ELISA, respectively. The current results confirmed that miR-27a was significantly upregulated in IDD. In vitro, downregulation of miR-27a in LPS-stimulated NP cells by transfection with the miR-27a inhibitor resulted in suppression of p-p38 and NF-κB expression levels. Furthermore, the production of the proinflammatory factors IL-1β, IL-6 and TNF-α was significantly reduced in LPS-stimulated NP cells with downregulated miR-27a. In conclusion, miR-27a may function as a promoter in IDD development, while inhibition of miR-27a may suppress proinflammatory factors released by intervertebral disc cells by regulating the p38/mitogen-activated protein kinase (MAPK) signaling pathway.

IL-1β increases asporin expression via the NF-κB p65 pathway in nucleus pulposus cells during intervertebral disc degeneration

Disc degeneration (DD) is a multifaceted chronic process that alters the structure and function of intervertebral discs. The pathophysiology of degeneration is not completely understood, but the consensus is that changes in genes encoding extracellular matrix (ECM) proteins in the disc are the leading factors contributing to DD. Asporin is an ECM protein that has been shown to be increased in degenerated intervertebral discs, but little is known about how asporin is regulated during DD. In exploring the intricate mechanism, we confirmed that asporin was abundantly increased in patients’ degenerated nucleus pulposus. Consistently, the increased asporin expression with degeneration was also proved by rabbit intervertebral disc degeneration (IDD) model. Mechanistically, IL-1β upregulated asporin expression by activating the p65 pathway in human nucleus pulposus cells. Furthermore, p65 mediated asporin expression by binding to −41/−31 bp on asporin promoter. Functionally, asporin was the intermediator of IL-1β-inhibited aggrecan and collagen Π expression and played a negative role in TGF-β-induced aggrecan and collagen Π formation in human nucleus pulposus cells. Therefore, identifying asporin as a negative regulator of aggrecan and collagen Π and elucidating its induction mechanisms in human nucleus pulposus cells provides new insight for asporin induction during IDD.

Association between COL11A1 (rs1337185) and ADAMTS5 (rs162509) gene polymorphisms and lumbar spine pathologies in Chinese Han population: an observational study

OBJECTIVES

A previous study identified a significant association between several single nucleotide polymorphisms (SNPs) and lumbar disc degeneration (LDD) in Indians. To validate the association between these SNPs and specific lumbar spine pathologies, we performed a case-control study in Chinese Han population.

DESIGN

An observational study.

SETTING

University Hospital in Nanning, China.

PARTICIPANTS

This study included 428 patients with LDD and 400 normal controls.

OUTCOME MEASURES

Patients with LDD were classified into four subgroups, including disc herniation only (subgroup 1), discopathies or/and osteochondrosis associated with disc herniation (subgroup 2), spinal stenosis or/and spondylolisthesis (subgroup 3) and degenerative scoliosis (subgroup 4). This study was conducted by examining two aspects: environmental factors and SNP genotyping. The environmental factors were evaluated with a questionnaire survey including questions about body mass index, smoking habits, the physical demands of their job and exposure to vibrations. Rs1337185, rs5275, rs5277, rs7575934, rs3213718 and rs162509 were genotyped using a PCR-based invader assay.

RESULTS

The physical workload was significantly higher in patients with lumbar spine pathologies than in the normal controls (p=0.035). The genotype and allele frequencies of rs1337185 and rs162509 were significantly different between the patients with LDD and the normal controls. In rs1337185, a significant association was found between the C allele (risk allele) and the presence of disc herniation (OR=1.80; 95% CI 1.21 to 2.68; p=0.003, adjusted p=0.012) and the presence of spinal stenosis and spondylolisthesis (OR=1.92; 95% CI 1.29 to 2.89; p=0.001, adjusted p=0.004). In rs162509, the G allele represented 1.58-fold increased risk to suffer from disc herniation (OR=1.58; 95% CI 1.20 to 2.09; p=0.001, adjusted p=0.004).

CONCLUSION

The SNPs rs1337185 in COL11A1 and rs162509 in ADAMTS5 are associated with susceptibility to LDD. The C allele of rs1337185 is risky for patients who are affected by lumbar pathologies such as disc herniation, stenosis and spondylolisthesis. The G allele of rs16250 represents a risk factor for the development of disc herniation.

Whole-body vibration of mice induces progressive degeneration of intervertebral discs associated with increased expression of Il-1β and multiple matrix degrading enzymes

OBJECTIVE

Whole-body vibration (WBV) is a popular fitness trend based on claims of increased muscle mass, weight loss and reduced joint pain. Following its original implementation as a treatment to increase bone mass in patients with osteoporosis, WBV has been incorporated into clinical practice for musculoskeletal disorders, including back pain. However, our recent studies revealed damaging effects of WBV on joint health in a murine model. In this report, we examined potential mechanisms underlying disc degeneration following exposure of mice to WBV.

METHODS

Ten-week-old male mice were exposed to WBV (45 Hz, 0.3 g peak acceleration, 30 min/day, 5 days/week) for 4 weeks, 8 weeks, or 4 weeks WBV followed by 4 weeks recovery. Micro-computed tomography (micro-CT), histological, and gene expression analyses were used to assess the effects of WBV on spinal tissues.

RESULTS

Exposure of mice to 4 or 8 weeks of WBV did not alter total body composition or induce significant changes in vertebral bone density. On the other hand, WBV-induced intervertebral disc (IVD) degeneration, associated with decreased disc height and degenerative changes in the annulus fibrosus (AF) that did not recover within 4 weeks after cessation of WBV. Gene expression analysis showed that WBV for 8 weeks induced expression of Mmp3, Mmp13, and Adamts5 in IVD tissues, changes preceded by increased expression of Il-1β.

CONCLUSIONS

Progressive IVD degeneration induced by WBV was associated with increased expression of Il-1β within the IVD that preceded Mmp and Adamts gene induction. Moreover, WBV-induced IVD degeneration is not reversed following cessation of vibration.

Correlation Between Expression of High Temperature Requirement Serine Protease A1 (HtrA1) in Nucleus Pulposus and T2 Value of Magnetic Resonance Imaging

BACKGROUND Degrading enzymes play an important role in the process of disc degeneration. The objective of this study was to investigate the correlation between the expression of high temperature requirement serine protease A1 (HtrA1) in the nucleus pulposus and the T2 value of the nucleus pulposus region in magnetic resonance imaging (MRI). MATERIAL AND METHODS Thirty-six patients who had undergone surgical excision of the nucleus pulposus were examined by MRI before surgery. Pfirrmann grading of the target intervertebral disc was performed according to the sagittal T2-weighted imaging, and the T2 value of the target nucleus pulposus was measured according to the median sagittal T2 mapping. The correlation between the Pfirrmann grade and the T2 value was analyzed. The expression of HtrA1 in the nucleus pulposus was analyzed by RT-PCR and Western blot. The correlation between the expression of HtrA1 and the T2 value was analyzed. RESULTS The T2 value of the nucleus pulposus region was 33.11-167.91 ms, with an average of 86.64±38.73 ms. According to Spearman correlation analysis, there was a rank correlation between T2 value and Pfirrmann grade (P<0.0001), and the correlation coefficient (rs)=-0.93617. There was a linear correlation between the mRNA level of HtrA1 and T2 value in nucleus pulposus tissues (a=3.88, b=-0.019, F=112.63, P<0.0001), normalized regression coefficient=-0.88. There was a linear correlation between the expression level of HtrA1 protein and the T2 value in the nucleus pulposus tissues (a=3.30, b=-0.016, F=93.15, P<0.0001) and normalized regression coefficient=-0.86. CONCLUSIONS The expression of HtrA1 was strongly related to the T2 value, suggesting that HtrA1 plays an important role in the pathological process of intervertebral disc degeneration.

Intervertebral Disk Degeneration and Repair

Intervertebral disk (IVD) degeneration is a natural progression of the aging process. Degenerative disk disease (DDD) is a pathologic condition associated with IVD that has been associated with chronic back pain. There are a variety of different mechanisms of DDD (genetic, mechanical, exposure). Each of these pathways leads to a final common result of unbalancing the anabolic and catabolic environment of the extracellular matrix in favor of catabolism. Attempts have been made to gain an understanding of the process of IVD degeneration with in Vitro studies. These models help our understanding of the disease process, but are limited as they do not come close to replicating the complexities that exist with an in Vivo model. Animal models have been developed to help us gain further understanding of the degenerative cascade of IVD degeneration In Vivo and test experimental treatment modalities to either prevent or reverse the process of DDD. Many modalities for treatment of DDD have been developed including therapeutic protein injections, stem cell injections, gene therapy, and tissue engineering. These interventions have had promising outcomes in animal models. Several of these modalities have been attempted in human trials, with early outcomes having promising results. Further, increasing our understanding of the degenerative process is essential to the development of new therapeutic interventions and the optimization of existing treatment protocols. Despite limited data, biological therapies are a promising treatment modality for DDD that could impact our future management of low back pain.

Matrix metalloproteinase-1 promoter -1607 bp 1G/2G polymorphism associated with increased risk of spinal tuberculosis in Southern Chinese Han population

BACKGROUND

Spinal tuberculosis is the most common form of musculoskeletal tuberculosis. The expression of matrix metalloproteinase-1 (MMP-1) is increased in cells with Mycobacterium tuberculosis infection. MMP-1 plays a curial role in extracellular matrix degradation during the progression of tuberculosis. Although the 1G/2G polymorphism in MMP-1-1607 influences its transcription, its role in spinal tuberculosis remains unknown.

METHODS

Healthy controls and patients with spinal tuberculosis of Han ethnicity were recruited between January 2010 and May 2016. The MMP-1-1607 1G/2G polymorphism was genotyped using the Sequenom mass Array polymorphism analysis system.

RESULTS

The genotypes of 1G/1G, 1G/2G, and 2G/2G were found in 13.7%, 53.6%, and 32.8% of patients, and 12.2%, 37.4%, and 50.4% of controls, respectively. The 1G/2G genotype were more common in cases than in controls (P=2.05E-04). The 1G allele showed an association with an increased risk for spinal tuberculosis when compared to 2G allele (P=.004). 1G genotypes, having at least one 1G allele, were associated with the risk of developing spinal tuberculosis (1G/1G+1G/2G vs 2G/2G: OR=2.084, 95%CI=1.401-3.100, P=2.65E-04).

CONCLUSION

1G genotypes of the MMP-1-1607 may be associated with susceptibility to spinal tuberculosis in Southern Chinese Han population.

Single Nucleotide Variants of Candidate Genes in Aggrecan Metabolic Pathway Are Associated with Lumbar Disc Degeneration and Modic Changes

Introduction

Lumbar disc degeneration (LDD) is genetically determined and severity of LDD is associated with Modic changes. Aggrecan is a major proteoglycan in the intervertebral disc and end plate. Progressive reduction of aggrecan is a main feature of LDD and Modic changes.

Objectives

The study investigated the associations of single nucleotide variants (SNVs) of candidate genes in the aggrecan metabolic pathway with the severity of LDD and Modic changes. In-silico functional analysis of significant SNVs was also assessed.

Methods

A descriptive cross sectional study was carried out on 106 patients with chronic mechanical low back pain. T1, T2 sagittal lumbar MRI scans were used to assess the severity of LDD and Modic changes. 62 SNVs in ten candidate genes (ACAN, IL1A, IL1B, IL6, MMP3, ADAMTS4, ADAMTS5, TIMP1, TIMP2 and TIMP3) were genotyped on Sequenom MassARRAY iPLEX platform. Multiple linear regression analysis was carried out using PLINK 1.9 in accordance with additive genetic model. In-silico functional analysis was carried out using Provean, SIFT, PolyPhen and Mutation Taster.

Results

Mean age was 52.42±9.42 years. 74 (69.8%) were females. The rs2856836, rs1304037, rs17561 and rs1800587 variants of the IL1A gene were associated with the severity of LDD and Modic changes. The rs41270041 variant of the ADAMTS4 gene and the rs226794 variant of the ADAMTS5 gene were associated with severity of LDD while the rs34884997 variant of the ADAMTS4 gene, the rs55933916 variant of the ADAMTS5 gene and the rs9862 variant of the TIMP3 gene were associated with severity of Modic changes. The rs17561 variant of the IL1A gene was predicted as pathogenic by the PolyPhen prediction tool.

Conclusions

SNVs of candidate genes in ACAN metabolic pathway are associated with severity of LDD and Modic changes in patients with chronic mechanical low back pain. Predictions of in-silico functional analysis of significant SNVs are inconsistent.

Correlations Between COL2A and Aggrecan Genetic Polymorphisms and the Risk and Clinicopathological Features of Intervertebral Disc Degeneration in a Chinese Han Population: A Case-Control Study

OBJECTIVES

This case-control study was designed to evaluate the association of three COL2A1 single nucleotide polymorphism (SNPs) (rs1793953, rs2276454, and rs1793937) and Aggrecan variable number of tandem repeat (VNTR) polymorphisms with the risk and clinicopathological features of intervertebral disc degeneration (IVDD) in a Chinese Han population.

MATERIALS AND METHODS

Data from 295 IVDD patients (case group) and 324 healthy volunteers (control group) were collected between January 2012 and December 2014. Magnetic resonance examinations were conducted on all included subjects. The frequency distributions of the COL2A1 and Aggrecan polymorphisms were detected using direct sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, respectively.

RESULTS

The genotype and allele frequencies of the COL2A1 genetic polymorphisms (rs1793953 and rs2276454) and the Aggrecan VNTR polymorphisms differed significantly between the case group and the control group (all p < 0.05). The haplotype analysis indicated that the frequencies of ACGL (L, long) and GTCL haplotypes were lower in the case group than in the control group (both p < 0.05). In the case group, the genotype and allele frequencies of the COL2A1 genes, rs1793953 and rs2276454, and Aggrecan VNTR significantly differed in terms of Pfirrmann grades III, IV, and V (all p < 0.05). Personal history of spine sprain or crush injury, history of IVDD in a first-degree relative, and COL2A1 rs2276454 and Aggrecan VNTR presence may be independent risk factors of IVDD (all p < 0.05, odds ratio [OR] >1), whereas tea drinking habit, part-time sports participation, and COL2A1 rs1793953 presence may be protective factors of IVDD (all p < 0.05, OR <1).

CONCLUSION

Our study provides evidence that COL2A1 and Aggrecan genetic polymorphisms may be correlated with the risk and clinicopathological features of IVDD in a Chinese Han population, and ACGL and GTCL haplotypes may be protective factors of IVDD.

Can Exercise Positively Influence the Intervertebral Disc?

To better understand what kinds of sports and exercise could be beneficial for the intervertebral disc (IVD), we performed a review to synthesise the literature on IVD adaptation with loading and exercise. The state of the literature did not permit a systematic review; therefore, we performed a narrative review. The majority of the available data come from cell or whole-disc loading models and animal exercise models. However, some studies have examined the impact of specific sports on IVD degeneration in humans and acute exercise on disc size. Based on the data available in the literature, loading types that are likely beneficial to the IVD are dynamic, axial, at slow to moderate movement speeds, and of a magnitude experienced in walking and jogging. Static loading, torsional loading, flexion with compression, rapid loading, high-impact loading and explosive tasks are likely detrimental for the IVD. Reduced physical activity and disuse appear to be detrimental for the IVD. We also consider the impact of genetics and the likelihood of a 'critical period' for the effect of exercise in IVD development. The current review summarises the literature to increase awareness amongst exercise, rehabilitation and ergonomic professionals regarding IVD health and provides recommendations on future directions in research.

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.

How Reliable Are the Reported Genetic Associations in Disc Degeneration?: The Influence of Phenotypes, Age, Population Size, and Inclusion Sequence in 809 Patients

STUDY DESIGN

Prospective genetic association study.

OBJECTIVE

The aim of this study was to document the variations in the genetic associations, when different magnetic resonance imaging (MRI) phenotypes, age stratification, cohort size, and sequence of cohort inclusion are varied in the same study population.

SUMMARY OF BACKGROUND DATA

Genetic associations with disc degeneration have shown high inconsistency, generally attributed to hereditary factors and ethnic variations. However, the effect of different phenotypes, size of the study population, age of the cohort, etc have not been documented clearly.

METHODS

Seventy-one single-nucleotide polymorphisms (SNPs) of 41 candidate genes were correlated to six MRI markers of disc degeneration (annular tears, Pfirmann grading, Schmorl nodes, Modic changes, Total Endplate Damage score, and disc bulge) in 809 patients with back pain and/or sciatica. In the same study group, the correlations were then retested for different age groups, different sample, size and sequence of subject inclusion (first 404 and the second 405) and the differences documented.

RESULTS

The mean age of population (M: 455, F: 354) was 36.7 ± 10.8 years. Different genetic associations were found with different phenotypes: disc bulge with three SNPs of CILP; annular tears with rs2249350 of ADAMTS5 and rs11247361 IGF1R; modic changes with VDR and MMP20; Pfirmann grading with three SNPs of MMP20 and Schmorl node with SNPs of CALM1 and FN1 and none with Total End Plate Score.Subgroup analysis based on three age groups and dividing the total population into two groups also completely changed the associations for all the six radiographic parameters.

CONCLUSION

In the same study population, SNP associations completely change with different phenotypes. Variations in age, inclusion sequence, and sample size resulted in change of genetic associations. Our study questions the validity of previous studies and necessitates the need for standardizing the description of disc degeneration, phenotype selection, study sample size, age, and other variables in future studies.

LEVEL OF EVIDENCE

4.

Vitamin D Receptor Gene, Matrix Metalloproteinase 3 Polymorphisms and the Risk of Intervertebral Disc Degeneration Susceptibility: Meta-Analysis

Several studies have evaluated the association between vitamin D receptor, matrix metalloproteinase 3 (MMP-3) polymorphisms and the risk of intervertebral disc degeneration susceptibility. The findings were inconsistent. This meta-analysis aimed to systematically assess the association between vitamin D receptor, MMP-3 polymorphisms and the risk of intervertebral disc degeneration susceptibility. A search of various databases was done covering all papers published until December 31th, 2014. Eight, 4, 3 studies were finally included that addressed the risk of intervertebral disc degeneration susceptibility and vitamin D receptor FokI (rs2228570), ApaI (rs7975232), and MMP-3 (rs731236) polymorphisms, respectively. FokI (f vs. F: summary odds ratio [OR], 1.13; 95% confidence interval [CI], 0.76–1.69; ff vs. FF: OR, 1.02; 95% CI, 0.59–1.77; ff vs. Ff/FF: OR, 1.05; 95% CI, 0.70–1.58), ApaI (a vs. A: OR, 0.73; 95% CI, 0.45–1.19; aa vs. AA: OR, 0.53; 95% CI, 0.22–1.25 p=0.14; aa vs. AA/Aa: OR, 0.69; 95% CI, 0.53–0.89) in the vitamin D receptor gene and MMP3 polymorphisms (5A vs. 6A: OR, 1.92; 95% CI, 0.77–4.80; 5A5A vs. 6A6A: OR, 2.17; 95% CI, 0.75–6.24; 5A5A vs. 5A6A/6A6A: OR, 1.58; 95% CI, 0.72–3.44) were not obviously associated with risk of intervertebral disc degeneration susceptibility. FokI, ApaI polymorphisms in the vitamin D receptor gene and MMP-3 polymorphism are not obvious risk factors for intervertebral disc degeneration susceptibility.

Association Between Cartilage Intermediate Layer Protein and Degeneration of Intervertebral Disc: A Meta-analysis

STUDY DESIGN

Meta-analysis to collect all eligible studies for investigating whether cartilage intermediate layer protein (CILP) gene rs2073711 polymorphism is associated with susceptibility to intervertebral disc degeneration (IVD).

OBJECTIVE

To investigate the association between CILP gene rs2073711 and IVD.

SUMMARY OF BACKGROUND DATA

CILP is one of the limited genes that is being suggested to be associated with IVD. However, previous association study results of CILP and IVD are conflicted.

METHODS

The PubMed, ISI Web of Science, Science Direct Online, and China National Knowledge Infrastructure database were searched for relevant articles till November 1, 2015. The odds ratio (OR) and related 95% confidence interval (CI) were drawn out and merged to assess the strength of association by STATA version 12.0.

RESULTS

A total of 1551 IVD cases and 1793 controls from the 5 studies were used in this study, comprising four Asian populations and two European populations. Meta-analysis found that the CILP 2073711 polymorphism was significantly associated with IVD risk. The estimated OR of risk allele T of rs2073711 was 1.36. (95% CI = 1.18-1.55, P < 0.001). No significant heterogeneity and publication bias were observed in this study.

CONCLUSION

Our results confirm the positive association between CILP and IVD, providing novel clues for clarifying the role of CILP in the development of IVD.

LEVEL OF EVIDENCE

2.

Vitamin D receptor gene polymorphisms and lumbar disc degeneration: a systematic review and meta-analysis

PURPOSE

To examine the association between Vitamin D receptor (VDR) gene polymorphisms and lumbar disc degeneration (LDD) predisposition.

METHODS

A comprehensive literature search was conducted to identify all the relevant studies. The allele/genotype frequencies were extracted from each study. We calculated the pooled odds ratios (ORs) and 95 % confidence intervals (CI) to assess the strength of the association between the VDR gene polymorphisms and LDD risk. Statistical analysis was performed using RevMan 5.31 software.

RESULTS

A total of 23 case-control studies (1835 cases and 1923 controls) were included in this systematic review. For the TaqI (rs731236), FokI (rs2228570) and ApaI (rs7975232) polymorphisms of VDR gene, nine studies, seven studies, and five studies, were eventually included in the meta-analysis, respectively. There was no evidence that the VDR gene polymorphisms (TaqI, FokI, ApaI) had significant associations with LDD risk.(for TaqI allelic comparison, OR = 1.07, 95 % CI 0.81-1.40, p = 0.64; for FokI allelic comparison, OR = 1.23, 95 % CI 0.83-1.82, p = 0.31; for ApaI allelic comparison, OR = 0.79, 95 % CI 0.55-1.14, p = 0.20). For stratified analyses by ethnicity and study design, no significant associations were found in Caucasian population and Asian population, as well as the population-based studies and hospital-based studies under all genetic models.

CONCLUSIONS

TaqI, FokI, and ApaI polymorphisms of VDR gene were not significantly associated with the predisposition of LDD. Large-scale and well-designed international studies are needed to further analyze this field.

BsmI, ApaI and TaqI Polymorphisms in the Vitamin D Receptor Gene (VDR) and Association with Lumbar Spine Pathologies: An Italian Case-Control Study

Three adjacent single nucleotide polymorphisms of the vitamin D receptor gene (VDR) BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) are commonly studied in several pathologies. We aimed to evaluate the distribution of VDR BsmI, ApaI, and TaqI allele, genotype, and haplotype frequencies in an Italian cohort of 266 patients with lumbar spine disorders assessed by Magnetic Resonance Imaging and 252 asymptomatic controls. The exposure to putative risk factors was evaluated by a questionnaire. Polymorphisms were detected by PCR-RFLP and TaqMan^® SNP Genotyping Assay. The results were statistically adjusted for the identified conventional risk factors. The three SNPs were in linkage disequilibrium. For all cases BbAaTT was a 3-fold risk factor OR = 3.38), whereas bbAATT (OR = 0.22), and bbaaTT (OR = 0.47) genotypes were found to be protective. Specifically, for patients affected by disc herniation only (n = 88) and all lumbar pathologies excluding stenosis and/or spondylolistesis (n = 215) B allele, Bb, Aa, and BbAaTT genotypes were risky, whereas b allele, bb, aa, and bbaaTT genotypes were protective. In patients affected by osteochondrosis with or without disc hernation (n = 50), T allele, Aa, and bbAaTT genotypes were risky, whereas t allele, AA, tt genotypes were protective. In patients affected by stenosis and/or spondylolistesis (n = 51) no significant associations were found. This is the first study showing an association of the three genetic VDR variants BsmI, ApaI, and TaqI and lumbar spine pathologies. Our study contributes to delineate genetic risk factors for specific subgroups of patients with lumbar spine pathologies highlighting the importance of haplotype analysis, and of detailed clinical evaluation of the patients for identification of genetic biomarkers.

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.

FoxC2 Enhances BMP7-Mediated Anabolism in Nucleus Pulposus Cells of the Intervertebral Disc

Bone-morphogenetic protein-7 (BMP-7) is a growth factor that plays a major role in mediating anabolism and anti-catabolism of the intervertebral disc matrix and cell homeostasis. In osteoblasts, Forkhead box protein C2 (FoxC2) is a downstream target of BMPs and promotes cell proliferation and differentiation. However, the role FoxC2 may play in degenerative human intervertebral disc tissue and the relationship between FoxC2 and BMP-7 in nucleus pulposus (NP) cells remain to be elucidated. This study aims to investigate the presence and signaling mechanisms of FoxC2 in degenerative human intervertebral disc tissue and NP cells. Western blot and real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses were used to measure FoxC2 expression in the NP tissue and cells. Transfections were carried out to measure the effect of FoxC2 on BMP-7-mediated extracellular matrix upregulation. Adenoviral knock-down of Smad1 was performed to investigate the mechanism of BMP-7-induced FoxC2 expression. In degenerative NP tissue, FoxC2 was markedly upregulated and positively correlated with increased disc degeneration. Induction of NP cell proliferation was confirmed by using cell counting kit-8 assay, immunocytochemistry and real-time qRT-PCR for Ki67. FoxC2 led to decreased noggin expression and increased Smad1/5/8 phosphorylation. During combined treatment with BMP-7, FoxC2 greatly potentiated anabolism through synergistic mechanisms on ECM formation. Combination therapy using BMP-7 and FoxC2 may be beneficial to the treatment of intervertebral disc degeneration.

Notochord Cells in Intervertebral Disc Development and Degeneration

The intervertebral disc is a complex structure responsible for flexibility, multi-axial motion, and load transmission throughout the spine. Importantly, degeneration of the intervertebral disc is thought to be an initiating factor for back pain. Due to a lack of understanding of the pathways that govern disc degeneration, there are currently no disease-modifying treatments to delay or prevent degenerative disc disease. This review presents an overview of our current understanding of the developmental processes that regulate intervertebral disc formation, with particular emphasis on the role of the notochord and notochord-derived cells in disc homeostasis and how their loss can result in degeneration. We then describe the role of small animal models in understanding the development of the disc and their use to interrogate disc degeneration and associated pathologies. Finally, we highlight essential development pathways that are associated with disc degeneration and/or implicated in the reparative response of the tissue that might serve as targets for future therapeutic approaches.

Serum levels of the proinflammatory cytokine interleukin-6 vary based on diagnoses in individuals with lumbar intervertebral disc diseases

BACKGROUND

Many intervertebral disc diseases cause low back pain (LBP). Proinflammatory cytokines and matrix metalloproteinases (MMPs) participate in disc pathology. In this study, we examined levels of serum cytokines and MMPs in human subjects with diagnoses of disc herniation (DH), spinal stenosis (SS), or degenerative disc disease (DDD) relative to levels in control subjects. Comparison between subjects with DH and those with other diagnoses (Other Dx, grouped from SS and DDD) was performed to elaborate a pathological mechanism based on circulating cytokine levels.

METHODS

Study participants were recruited from a spine neurosurgery practice (n = 80), a back pain management practice (n = 27), or a control cohort (n = 26). Serum samples were collected before treatment and were assayed by multiplex assays for levels of interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, interferon-γ, tumor necrosis factor-α, MMP-1, MMP-3, and MMP-9. Inflammatory and degradative mediator levels were compared for subjects with LBP and control subjects, by diagnosis and by treatment groups, controlling for effects of sex, age, and reported history of osteoarthritis. Spearman's correlation coefficient was used to examine relationships with age, body mass index (BMI), symptom duration, and smoking history.

RESULTS

Serum levels of IL-6 were significantly higher in subjects with LBP compared with control subjects. Participants with LBP due to Other Dx had significantly higher levels of IL-6 than DH and controls. Serum levels of MMP-1 were significantly lower in LBP subjects, specifically those with DH, than in control subjects. Positive correlations were found between IL-6 levels and BMI, symptom duration, and age. MMP-1 levels were positively correlated with age.

CONCLUSIONS

The findings of the present clinical study are the results of the first examination of circulating cytokine levels in DDD and SS and provide evidence for a more extensive role of IL-6 in disc diseases, where patients with DDD or SS have higher serum cytokine levels than those with DH or control subjects. These findings suggest that LBP subjects have low-grade systemic inflammation, and biochemical profiling of circulating cytokines may assist in refining personalized diagnoses of disc diseases.

Association Between VDR FokI Polymorphism and Intervertebral Disk Degeneration

Intervertebral disk degeneration (IDD) is strongly associated with genetic predisposition and environmental susceptibility. Several studies been conducted to investigate the potential association between IDD and FokI polymorphism located in the gene encoding the vitamin D receptor (VDR), and inconsistent conclusions had been reached among different ethnic populations. In order to assess the association between the FokI polymorphism and the risk of IDD, we performed a comprehensive and systematic meta-analysis. Candidate articles were retrieved from PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), and China Biology Medical (CBM) with strict inclusion criteria in January 2015. Among the 54 articles that were retrieved, only eight studies met the inclusion criteria. The pooled data analysis based on allele contrast, homozygote, heterozygote, dominant, and recessive models revealed no significant correlation between the FokI polymorphism and the risk of IDD. However, when stratified by ethnicity, significant associations were detected for Hispanics based on allele contrast (OR=1.395, 95% CI=1.059-1.836, P=0.018), homozygote (OR=1.849, 95% CI=1.001-3.416, P=0.049), heterozygote (OR=1.254, 95% CI=1.049-1.498, P=0.013), and dominant (OR=1.742, 95% CI=1.174-2.583, P=0.006) models, and for Asians using the dominant model (OR=1.293, 95% CI=1.025-1.632, P=0.030), whereas there is no significant association detected for Caucasians. In conclusion, FokI polymorphism is not generally associated with IDD, but there is increased risk for IDD in Hispanics and Asians carrying FokI allele T.

Association of collagen I, IX and vitamin D receptor gene polymorphisms with radiological severity of intervertebral disc degeneration in Southern European Ancestor

PURPOSE

Several genomic loci have been previously found to be associated with intervertebral disc degeneration, so far. Data are mostly derived from northern European countries whereas data derived from Southern European Ancestor are limited. This study aimed to evaluate the association between radiological disease severity of lumbar disc degeneration and certain genetic loci in a sample of participants from Southern Europe.

METHODS

Seventy-five patients with mild to severe lumbar disc degeneration and 25 healthy controls were enrolled into the study. In each subject, each lumbar intervertebral disc was separately examined to obtain a total radiological score for disease severity. In addition, single-nucleotide polymorphisms of predefined genetic samples were analyzed in all participants: COL1A1 Sp1, COL9a2 Trp2, COL9a3 Trp3, and VDR TaqI.

RESULTS

Degeneration scores were significantly worse in cases with COL1A1 Sp1, COL9a3 Trp3, and VDR TaqI mutations; however, COL9a2 Trp2 mutation was not associated with a difference in the severity of disc degeneration. In addition, subjects with mutation in more than one gene sample (n = 20) had significantly worse degeneration scores than the remaining study participants (n = 80) (17.70 ± 2.72 vs. 21.81 ± 1.81, p < 0.001).

CONCLUSION

Single-nucleotide polymorphisms occurring in COL1A1, COL9a3 and VDR genes seem to be associated with the development of lumbar disc degeneration in this cohort, possibly with even more pronounced association when multiple mutations are present in the same individual. By further prospective twin studies in associated genes and analyses of their relationship with environmental factors in an internationally sampled large cohort will make a more clear-minded conclusion about their association with disc degeneration, which would yield better appreciation and clinical planning of some predisposed people for these pathologies.

Age and pro-inflammatory gene polymorphisms influence adjacent segment disc degeneration more than fusion does in patients treated for chronic low back pain

PURPOSE

Does lumbar fusion lead to accelerated adjacent segment disc degeneration (ASDD) or is it explained by genetics and aging? The influence of genetics on ASDD remains to be explored. This study assesses whether the disc space height adjacent to a fused segment is associated with candidate gene single nucleotide polymorphisms (SNPs).

METHODS

Patients with low back pain from four RCTs (N = 208 fusion; 77 non-operative treatment) underwent standing plain radiography and genetic analyses at 13 ± 4 years follow-up. Disc space height was measured using a validated computer-assisted distortion-compensated roentgen analysis technique and reported in standard deviations from normal values. Genetic association analyses included 34 SNPs in 25 structural, inflammatory, matrix degrading, apoptotic, vitamin D receptor and OA-related genes relevant to disc degeneration. These were analysed for their association with disc space height (after adjusting for age, gender, smoking, duration of follow-up and treatment group) first, separately, and then together in a stepwise multivariable model.

RESULTS

Two SNPs from the IL18RAP gene (rs1420106 and rs917997) were each associated with a lower disc space height at the adjacent level (B = -0.34, p = 0.04 and B = -0.35, p = 0.04, respectively) and the MMP-9 gene SNP rs20544 was associated with a greater disc space height (B = 0.35, p = 0.04). Age (p < 0.001) and fusion (p < 0.008) were also significant variables in each analysis. The total explained variance in disc space height was for each SNP model 13-14 %, with 11-12 % of this being accounted for by the given SNP, 64-67 % by age and 19-22 % by fusion. In the multivariable regression analysis (with nine SNPs selected for entry, along with the covariates) the total explained variance in disc space height was 23 %, with the nine SNPs, age and fusion accounting for 45, 45 and 7 % of this, respectively.

CONCLUSIONS

Age was the most significant determinant of adjacent segment disc space height followed by genetic factors, specifically inflammatory genes. Fusion explained a statistically significant but small proportion of the total variance. Much of the variance remained to be explained.

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.

Mechanics and biology in intervertebral disc degeneration: a vicious circle

Intervertebral disc degeneration is a major cause of low back pain. Despite its long history and large socio-economical impact in western societies, the initiation and progress of disc degeneration is not well understood and a generic disease model is lacking. In literature, mechanics and biology have both been implicated as the predominant inductive cause; here we argue that they are interconnected and amplify each other. This view is supported by the growing awareness that cellular physiology is strongly affected by mechanical loading. We propose a vicious circle of mechanical overloading, catabolic cell response, and degeneration of the water-binding extracellular matrix. Rather than simplifying the disease, the model illustrates the complexity of disc degeneration, because all factors are interrelated. It may however solve some of the controversy in the field, because the vicious circle can be entered at any point, eventually leading to the same pathology. The proposed disease model explains the comparable efficacy of very different animal models of disc degeneration, but also helps to consider the consequences of therapeutic interventions, either at the cellular, material or mechanical level.

Association between TRAIL gene polymorphisms and the susceptibility and severity of lumbar disc degeneration

AIM

The aim of the present study was to investigate the association between tumor necrosis factor related apoptosis-inducing ligand (TRAIL) gene polymorphisms and the susceptibility and severity of lumbar disc degeneration (LDD) in the Chinese Han population.

METHODS

A total of 153 patients with LDD and 131 healthy subjects were enrolled in the study. Four single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3'UTR) of TRAIL gene, including 1289 C/A, 1525 G/A, 1588 G/A and 1595 C/T, were genotyped with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The genotypes and alleles frequencies of TRAIL at 1525 and 1595 positions in all subjects were the same. There was a significant association between TRAIL 1525/1595 polymorphisms and the susceptibility of LDD. The frequencies of 1525 GG /1595 CC genotype, and 1525 G/1595 C allele were higher in the patients group than that in the control group. In addition, we found patients with the 1525 AA /1595 TT genotype, as well as 1525 A/1595 T allele exhibit significantly low frequency of high grades of disc degeneration. However, there were no significant differences in the genotype or allele distribution of TRAIL 1289 C/A or 1588 G/A between the patients and the control group.

CONCLUSION

TRAIL 1525/1595 polymorphisms were associated with the susceptibility and severity of LDD in the Chinese Han population.

Inhibitory effects of platelet-rich plasma on intervertebral disc degeneration: a preclinical study in a rabbit model

Background

Platelet-rich plasma (PRP) contains multiple growth hormones that may stimulate tissue repair. This study aimed to assess the effects of PRP in a rabbit model of IDD (annulus fibrosus puncture).

Material/Methods

Thirty-six adult New Zealand white rabbits were randomly divided into 3 groups: 0.1 mL PRP (group A), 0.1 mL phosphate-buffered saline (group B), and control (group C) (n=12/group). Annulus fibrosus puncture was performed to establish L4/5 and L5/6 IDD models. Two and 4 weeks later, 6 rabbits from each group were given an IVD injection at L4/5 and L5/6. Two or 4 weeks after injection, rabbits were scanned with X-ray and MRI before being sacrificed. IVDs were collected for hematoxylin and eosin, Masson’s trichrome, and Safranin O staining, and type II collagen immunohistochemistry.

Results

Over time, IVD height and disc imaging signal intensity decreased gradually in groups B and C, but only slightly in group A (baseline: 100% for all groups; A: 95.9±4.2% at 4 weeks, 90.1±8.4 at 6 weeks; B: 75.3±5.7% at 4 weeks, 70.8±6.4% at 6 weeks; C: 74.7±5.5% at 4 weeks, 69.9±6.2% at 6 weeks; all P<0.001, P<0.01 between A vs. B and C). Degenerative histological changes in IVDs in groups B and C were more severe compared with group A.

Conclusions

Platelet-rich plasma interventions can effectively attenuate the IDD process in rabbits.

Scavenger receptor class A member 5 (SCARA5) and suprabasin (SBSN) are hub genes of coexpression network modules associated with peripheral vein graft patency

OBJECTIVE

Approximately 30% of autogenous vein grafts develop luminal narrowing and fail because of intimal hyperplasia or negative remodeling. We previously found that vein graft cells from patients who later develop stenosis proliferate more in vitro in response to growth factors than cells from patients who maintain patent grafts. To discover novel determinants of vein graft outcome, we have analyzed gene expression profiles of these cells using a systems biology approach to cluster the genes into modules by their coexpression patterns and to correlate the results with growth data from our prior study and with new studies of migration and matrix remodeling.

METHODS

RNA from 4-hour serum- or platelet-derived growth factor (PDGF)-BB-stimulated human saphenous vein cells obtained from the outer vein wall (20 cell lines) was used for microarray analysis of gene expression, followed by weighted gene coexpression network analysis. Cell migration in microchemotaxis chambers in response to PDGF-BB and cell-mediated collagen gel contraction in response to serum were also determined. Gene function was determined using short-interfering RNA to inhibit gene expression before subjecting cells to growth or collagen gel contraction assays. These cells were derived from samples of the vein grafts obtained at surgery, and the long-term fate of these bypass grafts was known.

RESULTS

Neither migration nor cell-mediated collagen gel contraction showed a correlation with graft outcome. Although 1188 and 1340 genes were differentially expressed in response to treatment with serum and PDGF, respectively, no single gene was differentially expressed in cells isolated from patients whose grafts stenosed compared with those that remained patent. Network analysis revealed four unique groups of genes, which we term modules, associated with PDGF responses, and 20 unique modules associated with serum responses. The "yellow" and "skyblue" modules, from PDGF and serum analyses, respectively, correlated with later graft stenosis (P = .005 and P = .02, respectively). In response to PDGF, yellow was also associated with increased cell growth. For serum, skyblue was also associated with inhibition of collagen gel contraction. The hub genes for yellow and skyblue (ie, the gene most connected to other genes in the module), scavenger receptor class A member 5 (SCARA5) and suprabasin (SBSN), respectively, were tested for effects on proliferation and collagen contraction. Knockdown of SCARA5 increased proliferation by 29.9% ± 7.8% (P < .01), whereas knockdown of SBSN had no effect. Knockdown of SBSN increased collagen gel contraction by 24.2% ± 8.6% (P < .05), whereas knockdown of SCARA5 had no effect.

CONCLUSIONS

Using weighted gene coexpression network analysis of cultured vein graft cell gene expression, we have discovered two small gene modules, which comprise 42 genes, that are associated with vein graft failure. Further experiments are needed to delineate the venous cells that express these genes in vivo and the roles these genes play in vein graft healing, starting with the module hub genes SCARA5 and SBSN, which have been shown to have modest effects on cell proliferation or collagen gel contraction.

MicroRNA in intervertebral disc degeneration

Aetiology of intervertebral disc degeneration (IDD) is complex, with genetic, developmental, biochemical and biomechanical factors contributing to the disease process. It is becoming obvious that epigenetic processes influence evolution of IDD as strongly as the genetic background. Deregulated phenotypes of nucleus pulposus cells, including differentiation, migration, proliferation and apoptosis, are involved in all stages of progression of human IDD. Non-coding RNAs, including microRNAs, have recently been recognized as important regulators of gene expression. Research into roles of microRNAs in IDD has been very active over the past 5 years. Our review summarizes current research enlightenment towards understanding roles of microRNAs in regulating nucleus pulposus cell functions in IDD. These exciting findings support the notion that specific modulation of microRNAs may represent an attractive approach for management of IDD.

Stem cell therapy for intervertebral disc regeneration: obstacles and solutions

Intervertebral disc (IVD) degeneration is frequently associated with low back and neck pain, which accounts for disability worldwide. Despite the known outcomes of the IVD degeneration cascade, the treatment of IVD degeneration is limited in that available conservative and surgical treatments do not reverse the pathology or restore the IVD tissue. Regenerative medicine for IVD degeneration, by injection of IVD cells, chondrocytes or stem cells, has been extensively studied in the past decade in various animal models of induced IVD degeneration, and has progressed to clinical trials in the treatment of various spinal conditions. Despite preliminary results showing positive effects of cell-injection strategies for IVD regeneration, detailed basic research on IVD cells and their niche indicates that transplanted cells are unable to survive and adapt in the avascular niche of the IVD. For this therapeutic strategy to succeed, the indications for its use and the patients who would benefit need to be better defined. To surmount these obstacles, the solution will be identified only by focused research, both in the laboratory and in the clinic.

Gender differences in the VDR-FokI polymorphism and conventional non-genetic risk factors in association with lumbar spine pathologies in an Italian case-control study

Recently, the FokI polymorphism (rs2228570) in the vitamin D receptor gene (VDR) and conventional risk factors were associated with spine disorders in the Italian population, but without gender analysis. Two-hundred and sixty-seven patients (149 males, 118 females) with lumbar spine disorders were assessed by magnetic resonance imaging (MRI) and 254 (127 males, 127 females) asymptomatic controls were enrolled. The exposure to putative risk factors was evaluated and FokI polymorphism was detected by PCR-restriction fragment length polymorphism (PCR-RFLP). An association between lumbar spine pathologies and higher than average age; overweight; family history; lower leisure physical activity; smoking habit; higher number of hours/day exposure to vibration and more sedentary or intense physical job demand was observed in male patients. In contrast, in females, only higher age, overweight, family history and lower leisure physical activity were risk factors. FF genotype was a 2-fold risk factor to develop discopathies and/or osteochondrosis concomitant with disc herniation for both gender patients, while heterozygous Ff was protective for females only. In males only ff genotype was protective for discopathies and/or osteochondrosis and F allele was a 2-fold risk factor for hernia; discopathies; discopathies and/or osteochondrosis. Sex-related differences in voluntary behaviors, exposure to environmental risks and genetic background could be crucial for a gender-differentiated management of patients with spine disorders.

Degenerated intervertebral disc prolapse and its association of collagen I alpha 1 Spl gene polymorphism: A preliminary case control study of Indian population

BACKGROUND

Degenerated disc disease (DDD) is a common disorder responsible for increased morbidity in a productive age group. Its etiology is multifactorial and genetic factors have been predominantly implicated. Disc prolapse results due to tear in the annulus, which is a fibrous structure composed largely of type I collagen. Functional polymorphism at the Sp1 site of the collagen I alpha 1 (COL1A1) gene has shown a positive association with DDD in Dutch and Greek populations. The purpose of this study was to assess COL1A1 Sp1 gene polymorphism in the Indian population.

MATERIALS AND METHODS

Fifty clinically and radiologically proven patients with disc prolapse requiring surgery were included as cases and 50 healthy, age-matched volunteers served as controls. After isolating DNA from their blood sample, genotyping for COL1A1 polymorphism (rs1800012) was performed and identified as GG, GT, and TT.

RESULTS

The mean age and body mass index in cases and controls were similar. 76% of the patients were males. The most common site of disc degeneration was L4-L5 (36%), followed by L5-S1 (34%). Homozygous-GG, heterozygous GT, and homozygous TT genotypes were seen in 38 (76%), 10 (20%) and 2 (4%) cases respectively, controls had similar percentage of genotypes as well. The alleles in cases and the control group showed no significant difference (P = 0.6744) and followed the Hardy-Weinberg Equilibrium in the study population.

CONCLUSION

The COL1A1 (rs1800012) is in Hardy-Weinberg equilibrium in the present subset of Indian population. But taken as a single factor, it was not found to be associated with DDD in this preliminary study. Disc degeneration is multifactorial and also anticipated to be a result of multiple genes involvement and gene-gene interaction.

Role of growth differentiation factor-5 and bone morphogenetic protein type II receptor in the development of lumbar intervertebral disc degeneration

The present study was designed to evaluate the role of growth differentiation factor-5 (GDF-5) and bone morphogenetic protein type II receptor (BMPR-II) in the development of lumbar intervertebral disc degeneration (IDD). A total of 24 patients with lumbar IDD (experiment group) and 6 patients with lumbar vertebral fracture (control group) were enrolled in the study. Tissue samples of IVD from the experiment group and control group were obtained during lumbar fusion operation, respectively. Fixation and decalcification of IVD tissue were performed, and then HE staining was carried out to observe the morphological changes of the lumbar IVD tissues. The expression of GDF-5 and BMPRII in human lumbar IVD was detected by immunohistochemical staining. HE staining results showed that non- and minimal degeneration was found in 11 cases (score range, 0-3), moderate degeneration in 12 cases (score range, 4-8), and severe degeneration in 7 cases (score range, 9-12). According to the immunohistochemical results, the positive expression rates of GDF-5 and BMPRII in NP were higher than those in AF of the non- and minimal degeneration group, moderate degeneration group and severe degeneration group (all P < 0.05). However, no significant difference in GDF-5 or BMPRII positive expression was observed among the normal, non- and minimal, moderate and severe degeneration groups in neither NP area nor AF area (all P > 0.05). In conclusion, our results showed that GDF-5 and BMPRII expressed both in normal and degenerated IVD tissues, and GDF-5 might have an inhibition effect on degenerated lumbar IVD, suggesting that gene therapy may be a useful approach in producing physiological effects during early- and late-phase of lumbar IDD.

Genetic and functional studies of the intervertebral disc: a novel murine intervertebral disc model

Intervertebral disc (IVD) homeostasis is mediated through a combination of micro-environmental and biomechanical factors, all of which are subject to genetic influences. The aim of this study is to develop and characterize a genetically tractable, ex vivo organ culture model that can be used to further elucidate mechanisms of intervertebral disc disease. Specifically, we demonstrate that IVD disc explants (1) maintain their native phenotype in prolonged culture, (2) are responsive to exogenous stimuli, and (3) that relevant homeostatic regulatory mechanisms can be modulated through ex-vivo genetic recombination. We present a novel technique for isolation of murine IVD explants with demonstration of explant viability (CMFDA/propidium iodide staining), disc anatomy (H&E), maintenance of extracellular matrix (ECM) (Alcian Blue staining), and native expression profile (qRT-PCR) as well as ex vivo genetic recombination (mT/mG reporter mice; AdCre) following 14 days of culture in DMEM media containing 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin/streptomycin. IVD explants maintained their micro-anatomic integrity, ECM proteoglycan content, viability, and gene expression profile consistent with a homeostatic drive in culture. Treatment of genetically engineered explants with cre-expressing adenovirus efficaciously induced ex vivo genetic recombination in a variety of genetically engineered mouse models. Exogenous administration of IL-1ß and TGF-ß3 resulted in predicted catabolic and anabolic responses, respectively. Genetic recombination of TGFBR1^fl/fl explants resulted in constitutively active TGF-ß signaling that matched that of exogenously administered TGF-ß3. Our results illustrate the utility of the murine intervertebral disc explant to investigate mechanisms of intervertebral disc degeneration.

Genetic polymorphisms of interleukin-1 alpha and the vitamin d receptor in mexican mestizo patients with intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the most common diagnosis in patients with back pain, a leading cause of musculoskeletal disability worldwide. Several conditions, such as occupational activities, gender, age, and obesity, have been associated with IDD. However, the development of this disease has strong genetic determinants. In this study, we explore the possible association between rs1800587 (c.-949C>T) of interleukin-1 alpha (IL1A) and rs2228570 (c.2T>V) and rs731236 (c.1056T>C) of vitamin D receptor (VDR) gene polymorphisms and the development of IDD in northwestern Mexican Mestizo population. Gene polymorphisms were analyzed by polymerase chain reaction followed by restriction fragment length polymorphism, in two groups matched by age and gender: patients with symptomatic lumbar IDD (n = 100) and subjects with normal lumbar-spine MRI-scans (n = 100). Distribution of the mutated alleles in patients and controls was 27.0% versus 28.0% (P = 0.455) for T of rs1800587 (IL1A); 53.0% versus 58.0% (P = 0.183) for V of rs2228570 (VDR); and 18.0% versus 21.0% (P = 0.262) for C of rs731236 (VDR). Our results showed no association between the studied polymorphisms and IDD in this population. This is the first report on the contribution of gene polymorphisms on IDD in a Mexican population.

Early intervertebral disc degeneration changes in asymptomatic weightlifters assessed by t1ρ-magnetic resonance imaging

STUDY DESIGN

Case-control study.

OBJECTIVE

To evaluate early intervertebral disc degeneration quantified by T1ρ- and T2-weighted magnetic resonance imaging (MRI) in asymptomatic weightlifters compared with a healthy control group matched for sex and age.

SUMMARY OF BACKGROUND DATA

Athletes consistently recruit or transfer high levels of repetitive forces through the spine, and MRI has documented a higher rate of intervertebral disc degeneration in athletes compared with matched controls. This study aims to analyze the potential role of T1ρ-MRI in the assessment of early degenerative changes occurring in intervertebral discs of young asymptomatic weightlifters compared with healthy controls.

METHODS

Twenty-six asymptomatic young male weightlifters versus a sedentary control group matched for age and sex, both having no lower back pain nor any spinal symptoms, underwent MRI (1.5 T). Degenerative grade was assessed using T2-weighted images, according to the Pfirrmann scale. T1ρ mapping and values in the nucleus pulposus (n=130) were obtained. Differences in T1ρ value between among the groups and linear regression analyses with degenerative grade were determined.

RESULTS

Pfirrmann degenerative grade did not show significant differences among groups. Instead, T1ρ values were significantly lower in the lumbar spine of weightlifters compared with controls (P<0.05). T1ρ values decreased linearly with degenerative grade.

CONCLUSION

T1ρ values were significantly lower in athletes compared with a sedentary matched control group showing differences in intervertebral disc degeneration onset among individuals with lifestyle and environmental factors leading to back pain. T1ρ can be potentially used as a valid clinical tool to identify early changes in intervertebral disc on the verge of new emerging intervertebral discs regenerative strategies and treatments.

LEVEL OF EVIDENCE

4.

Structure, function, aging and turnover of aggrecan in the intervertebral disc

BACKGROUND

Aggrecan is the major non-collagenous component of the intervertebral disc. It is a large proteoglycan possessing numerous glycosaminoglycan chains and the ability to form aggregates in association with hyaluronan. Its abundance and unique molecular features provide the disc with its osmotic properties and ability to withstand compressive loads. Degradation and loss of aggrecan result in impairment of disc function and the onset of degeneration.

SCOPE OF REVIEW

This review summarizes current knowledge concerning the structure and function of aggrecan in the normal intervertebral disc and how and why these change in aging and degenerative disc disease. It also outlines how supplementation with aggrecan or a biomimetic may be of therapeutic value in treating the degenerate disc.

MAJOR CONCLUSIONS

Aggrecan abundance reaches a plateau in the early twenties, declining thereafter due to proteolysis, mainly by matrix metalloproteinases and aggrecanases, though degradation of hyaluronan and non-enzymic glycation may also participate. Aggrecan loss is an early event in disc degeneration, although it is a lengthy process as degradation products may accumulate in the disc for decades. The low turnover rate of the remaining aggrecan is an additional contributing factor, preventing protein renewal. It may be possible to retard the degenerative process by restoring the aggrecan content of the disc, or by supplementing with a bioimimetic possessing similar osmotic properties.

GENERAL SIGNIFICANCE

This review provides a basis for scientists and clinicians to understand and appreciate the central role of aggrecan in the function, degeneration and repair of the intervertebral disc.

Asporin and the mineralization process in fluoride-treated rats

Microarray analysis of odontoblastic cells treated with sodium fluoride has identified the asporin gene as a fluoride target. Asporin is a member of the small leucine-rich repeat proteoglycan/protein (SLRP) family that is believed to be important in the mineralization process. In this study, asporin expression and distribution were investigated by systematic analysis of dentin and enamel, with and without fluoride treatment. Specific attention was focused on a major difference between the two mineralized tissues: the presence of a collagenous scaffold in dentin, and its absence in enamel. Normal and fluorotic, continually growing incisors from Wistar rats treated with 2.5 to 7.5 mM sodium fluoride (NaF) were studied by immunochemistry, in situ hybridization, Western blotting, and RT-qPCR. Asporin was continuously expressed in odontoblasts throughout dentin formation as expected. Asporin was also found, for the first time, in dental epithelial cells, particularly in maturation-stage ameloblasts. NaF decreased asporin expression in odontoblasts and enhanced it in ameloblasts, both in vivo and in vitro. The inverse response in the two cell types suggests that the effector, fluoride, is a trigger that elicits a cell-type-specific reaction. Confocal and ultrastructural immunohistochemistry evidenced an association between asporin and type 1 collagen in the pericellular nonmineralized compartments of both bone and dentin. In addition, transmission electron microscopy revealed asporin in the microenvironment of all cells observed. Thus, asporin is produced by collagen-matrix-forming and non-collagen-matrix-forming cells but may have different effects on the mineralization process. A model is proposed that predicts impaired mineral formation associated with the deficiency and excess of asporin.

Invoking the power of thrombospondins: regulation of thrombospondins expression

Increasing evidence suggests critical functions of thrombospondins (TSPs) in a variety of physiological and pathological processes. With the growing understanding of the importance of these matricellular proteins, the need to understand the mechanisms of regulation of their expression and potential approaches to modulate their levels is also increasing. The regulation of TSP expression is multi-leveled, cell- and tissue-specific, and very precise. However, the knowledge of mechanisms modulating the levels of TSPs is fragmented and incomplete. This review discusses the known mechanisms of regulation of TSP levels and the gaps in our knowledge that prevent us from developing strategies to modulate the expression of these physiologically important proteins.

A novel catechol-O-methyltransferase variant associated with human disc degeneration

BACKGROUND

Disc degeneration and its associated low back pain are a major health care concern causing disability with a prominent role in this country's medical, social and economic structure. Low back pain is devastating and influences the quality of life for millions. Low back pain lifetime prevalence approximates 80% with an estimated direct cost burden of $86 billion per year. Back pain patients incur higher costs, greater health care utilization, and greater work loss than patients without back pain.

METHODS

Research was performed following approval of our Institutional Review Board. DNA was isolated, processed and amplified using routine techniques. Amplified DNA was hybridized to Affymetrix Genome-Wide Human SNP Arrays. Quality control and genotyping analysis were performed using Affymetrix Genotyping Console. The Birdseed v2 algorithm was used for genotyping analysis. 2589 SNPs were selected a priori to enter statistical analysis using lotistic regression in SAS.

RESULTS

Our objective was to search for novel single nucleotide polymorphisms (SNPs) associated with disc degeneration. Four SNPs were found to have a significant relationship to disc degeneration; three are novel. Rs165656, a new SNP found to be associated with disc degeneration, was in catechol-O-methyltransferase (COMT), a gene with well-recognized pain involvement, especially in female subjects (p=0.01). Analysis confirmed the previously association between COMT SNP rs4633 and disc degeneration. We also report two novel disc degeneration-related SNPs (rs2095019 and rs470859) located in intergenic regions upstream to thrombospondin 2.

CONCLUSIONS

Findings contribute to the challenging field of disc degeneration and pain, and are important in light of the high clinical relevance of low back pain and the need for improved understanding of its fundamental basis.