Progression of lumbar disc degeneration over a decade: a heritability study

Bodily growth and the intervertebral disc: a longitudinal MRI study in healthy adolescents

BACKGROUND CONTEXT

Low back pain (LBP) among children and adolescents is a growing global concern. Disc degeneration (DD) is considered a significant factor in the clinical symptom of LBP. Both LBP and DD become more prevalent as adolescents transition into emerging adulthood. However, the relationship between growth during the pubertal growth spurt and the morphology of lumbar discs has yet to be elucidated.

PURPOSE

This study aimed to assess the relationship between bodily growth during the pubertal growth spurt and the morphology of lumbar discs at age 18.

STUDY DESIGN

This study was a prospective longitudinal cohort study.

PATIENT SAMPLE

A randomly selected cohort of healthy children was examined at ages 8, 11 and 18. Participants with complete data sets (semi-structured interview, anthropometric measurements and lumbar spine MRI) at age 11 and 18 were included in this analysis (n=59).

OUTCOME MEASURES

The morphological characteristics of lumbar discs were evaluated on MRI. Anthropometric measures including height, sitting height and weight were obtained to calculate the Body Surface Area (BSA) and the Body Mass Index (BMI).

METHODS

The morphology of the lumbar discs was evaluated on T2-weighted mid-sagittal MRI using the Pfirrmann classification. A disc with a Pfirrmann grade of 3 or higher was considered degenerated at age 18. The relationship between relative growth between ages 11 and 18 (adjusted to sex and baseline values) and DD at age 18 was assessed. To analyze the relationship between the relative increase in BSA and DD, the participants were categorized into three equal-sized categories (tertiles). For all other anthropometric measures, the analysis was based on the relative increase in each measure between ages 11 and 18.

RESULTS

In the highest tertile of relative increase in BSA (≥43%), 76% of participants had at least one disc with a Pfirrmann grade 3 or higher at age 18 while only 10% and 21% of participants in the lowest and medium tertiles had DD, respectively. The sex- and baseline-adjusted odds ratio (OR) for DD at age 18 for every additional 10% increase in BSA was 1.08 (1.02 to 1.15). The sex- and baseline-adjusted OR (95% CI) for DD at age 18 was 10.5 (1.60 to 68.7) and 7.92 (1.19 to 52.72) with every additional 10% increase in height and sitting height, respectively. For every additional 10% increase in weight, the adjusted OR for DD at age 18 was 1.51 (1.12 to 2.04) and for BMI 1.05 (1.01 to 1.09).

CONCLUSIONS

More relative growth between ages 11 and 18 is significantly associated with the occurrence of DD in emerging adulthood. Among the measures investigated, height and sitting height are non-modifiable. Maintaining an ideal body weight during the pubertal growth spurt may be beneficial for the health of the lumbar discs.

No evidence of association between either Modic change or disc degeneration and five circulating inflammatory proteins

Introduction

Intervertebral disc degeneration and Modic change are the main spinal structural changes associated with chronic low back pain (LBP). Both conditions are thought to manifest local inflammation and if inflammatory proteins translocate to the blood circulation could be detected systemically. The work here assesses whether the presence of disc degeneration is associated with detectable blood level changes of five inflammatory markers and whether chronic LBP is associated with these changes.

Materials and Methods

Two hundred and forty TwinsUK cohort participants with both MRI disc degeneration grade and Modic change extent, and IL-6, IL-8, IL-8 TNF, and CX3CL1 protein blood concentration measurements were included in this work. Linear mixed effects models were used to test the association of blood cytokine concentration with disc degeneration score and Modic change volumetric score. Association of chronic LBP status from questionnaires with disc degeneration, Modic change, and cytokine blood concentration was also tested.

Results

No statistically significant association between disc degeneration or Modic change with cytokine blood concentration was found. Instead, regression analysis pointed strong association between cytokine blood concentration with body mass index for IL-6 and with age for IL-6 and TNF. Mild association was found between IL-8 blood concentration and body mass index. Additionally, LBP status was associated with Modic change volumetric score but not associated with any cytokine concentration.

Conclusions

We found no evidence that Modic change and disc degeneration are able to produce changes in tested blood cytokine concentration. However, age and body mass index have strong influence on cytokine concentration and both are associated with the conditions studied which may confound associations found in the literature. It is then unlikely that cytokines produced in the disc or vertebral bone marrow induce chronic LBP.

Causal effects of body mass index, education, and lifestyle behaviors on intervertebral disc disorders: Mendelian randomization study

This study aimed to investigate the causal risk factors for intervertebral disc disorders (IVDD) to help establish prevention strategies for IVDD-related diseases. We performed two-sample Mendelian randomization analyses to investigate the causal effects of body mass index (BMI), education, and lifestyle behaviors (sedentary behavior, smoking, and sleeping) on thoracic/thoracolumbar/lumbosacral IVDD (TTL-IVDD) and cervical IVDD. The inverse-variance weighted (IVW) method was conducted as the primary model to pool effect sizes using odds ratio and 95% confidence interval. The strength of causal evidence was evaluated from the effect size and different Mendelian randomization methods (MR-Egger/weighted median/weighted mode method, Cochran's Q test, leave-one-out analysis, MR Steiger, MR-PRESSO and radial IVW analyses). We found strong evidence for the causal associations between IVDD and BMI (TTL-IVDD, 1.27 [1.18, 1.37], p = 2.40 × 10-10 ; cervical IVDD, 1.24 [1.12, 1.37, p = 6.58 × 10-5 ), educational attainment (TTL-IVDD, 0.57 [0.51, 0.64], p = 9.64 × 10-21 ; cervical IVDD, 0.58 [0.49, 0.68], p = 1.78 × 10-10 ), leisure television watching (TTL-IVDD, 1.54 [1.29, 1.84], p = 7.80 × 10-6 ; cervical IVDD, 1.65 [1.29, 2.11], p = 0.0001), smoking initiation (TTL-IVDD, 1.37 [1.25, 1.50], p = 1.78 × 10-10 ; cervical IVDD, 1.32 [1.16, 1.51], p = 6.49 × 10-5 ), short sleep (TTL-IVDD, 1.28 [1.09, 1.49], p = 0.0027; cervical IVDD, 1.53 [1.21, 1.94], p = 0.0008), or frequent insomnia (TTL-IVDD, 1.20 [1.11, 1.30], p = 1.54 × 10-5 ; cervical IVDD, 1.37 [1.20, 1.57], p = 7.80 × 10-6 ). This study provided genetic evidence that increased BMI, low educational attainment, sedentary behavior by leisure television watching, smoking initiation, short sleep, and frequent insomnia were causal risk factors for IVDD. More efforts should be directed toward increasing public awareness of these modifiable risk factors and mobilizing individuals to adopt healthy lifestyles.

Application and development of hydrogel biomaterials for the treatment of intervertebral disc degeneration: a literature review

Low back pain caused by disc herniation and spinal stenosis imposes an enormous medical burden on society due to its high prevalence and refractory nature. This is mainly due to the long-term inflammation and degradation of the extracellular matrix in the process of intervertebral disc degeneration (IVDD), which manifests as loss of water in the nucleus pulposus (NP) and the formation of fibrous disc fissures. Biomaterial repair strategies involving hydrogels play an important role in the treatment of intervertebral disc degeneration. Excellent biocompatibility, tunable mechanical properties, easy modification, injectability, and the ability to encapsulate drugs, cells, genes, etc. make hydrogels good candidates as scaffolds and cell/drug carriers for treating NP degeneration and other aspects of IVDD. This review first briefly describes the anatomy, pathology, and current treatments of IVDD, and then introduces different types of hydrogels and addresses "smart hydrogels". Finally, we discuss the feasibility and prospects of using hydrogels to treat IVDD.

A Review: Methodologies to Promote the Differentiation of Mesenchymal Stem Cells for the Regeneration of Intervertebral Disc Cells Following Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD), a highly prevalent pathological condition worldwide, is widely associated with back pain. Treatments available compensate for the impaired function of the degenerated IVD but typically have incomplete resolutions because of their adverse complications. Therefore, fundamental regenerative treatments need exploration. Mesenchymal stem cell (MSC) therapy has been recognized as a mainstream research objective by the World Health Organization and was consequently studied by various research groups. Implanted MSCs exert anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects and promote extracellular component production, as well as differentiation into IVD cells themselves. Hence, the ultimate goal of MSC therapy is to recover IVD cells and consequently regenerate the extracellular matrix of degenerated IVDs. Notably, in addition to MSC implantation, healthy nucleus pulposus (NP) cells (NPCs) have been implanted to regenerate NP, which is currently undergoing clinical trials. NPC-derived exosomes have been investigated for their ability to differentiate MSCs from NPC-like phenotypes. A stable and economical source of IVD cells may include allogeneic MSCs from the cell bank for differentiation into IVD cells. Therefore, multiple alternative therapeutic options should be considered if a refined protocol for the differentiation of MSCs into IVD cells is established. In this study, we comprehensively reviewed the molecules, scaffolds, and environmental factors that facilitate the differentiation of MSCs into IVD cells for regenerative therapies for IDD.

Aberrant mechanical loading induces annulus fibrosus cells apoptosis in intervertebral disc degeneration via mechanosensitive ion channel Piezo1

BACKGROUND

Intervertebral disc degeneration (IVDD) is closely associated with the structural damage in the annulus fibrosus (AF). Aberrant mechanical loading is an important inducement of annulus fibrosus cells (AFCs) apoptosis, which contributes to the AF structural damage and aggravates IVDD, but the underlying mechanism is still unclear. This study aims to investigate the mechanism of a mechanosensitive ion channel protein Piezo1 in aberrant mechanical loading-induced AFCs apoptosis and IVDD.

METHODS

Rats were subjected to lumbar instability surgery to induce the unbalanced dynamic and static forces to establish the lumbar instability model. MRI and histological staining were used to evaluate the IVDD degree. A cyclic mechanical stretch (CMS)-stimulated AFCs apoptosis model was established by a Flexcell system in vitro. Tunel staining, mitochondrial membrane potential (MMP) detection, and flow cytometry were used to evaluate the apoptosis level. The activation of Piezo1 was detected using western blot and calcium fluorescent probes. Chemical activator Yoda1, chemical inhibitor GSMTx4, and a lentiviral shRNA-Piezo1 system (Lv-Piezo1) were utilized to regulate the function of Piezo1. High-throughput RNA sequencing (RNA-seq) was used to explore the mechanism of Piezo1-induced AFCs apoptosis. The Calpain activity and the activation of Calpain2/Bax/Caspase3 axis were evaluated by the Calpain activity kit and western blot with the siRNA-mediated Calapin1 or Calpain2 knockdown. Intradiscal administration of Lv-Piezo1 was utilized to evaluate the therapeutic effect of Piezo1 silencing in IVDD rats.

RESULTS

Lumbar instability surgery promoted the expression of Piezo1 in AFCs and stimulated IVDD in rats 4 weeks after surgery. CMS elicited distinct apoptosis of AFCs, with enhanced Piezo1 activation. Yoda1 further promoted CMS-induced apoptosis of AFCs, while GSMTx4 and Lv-Piezo1 exhibited opposite effects. RNA-seq showed that knocking down Piezo1 inhibited the calcium signaling pathway. CMS enhanced Calpain activity and elevated the expression of BAX and cleaved-Caspase3. Calpain2, but not Calpain1 knockdown, inhibited the expression of BAX and cleaved-Caspase3 and alleviated AFCs apoptosis. Lv-Piezo1 significantly alleviated the progress of IVDD in rats after lumbar instability surgery.

CONCLUSIONS

Aberrant mechanical loading induces AFCs apoptosis to promote IVDD by activating Piezo1 and downstream Calpain2/BAX/Caspase3 pathway. Piezo1 is expected to be a potential therapeutic target in treating IVDD.

Association between anemia and lumbar disc degeneration in patients with low back pain: an observational retrospective study

OBJECTIVE

The goal of this study was to evaluate the possible associations between anemia and morphologic features of lumbar disc degeneration (LDD) in subjects with low back pain.

MATERIALS AND METHODS

A total of 131 patients with normocytic or microcytic anemia (mean age 41.0 ± 6.4 yrs, BMI: 24.8 ± 3.3 kg/m², 12.2% men) and a matched control group of 131 patients without anemia (mean age 41.0 ± 6.4 yrs, BMI: 24.9 ± 3.1 kg/m², 12.2% men) were evaluated for LDD according to the Pfirrmann scoring system. The primary outcome was the difference of radiological features of LDD between two groups. The second outcome was the correlation between the hemoglobin (Hb) value and disc degeneration (DD). Statistical associations were assessed by Student's t-test, Chi-square test, and Spearman correlation.

RESULTS

Anemic patients had a significantly higher number of degenerated discs than non-anemic patients in the level of L2/3 and L3/4 (p < 0.05). We also found that the severe DD occurred more frequently in the level of L2/3, L3/4 and L5/S1 among anemic patients (p < 0.05). In addition, we noticed that the incidence of multilevel LDD happened much more frequently in patients with anemia (p < 0.05). The Hb value showed a borderline negative correlation with the total score of DD (p = 0.056).

CONCLUSION

The results suggested that patients with anemia, and those without are radiologically different with varying patterns of DD. Patients with back pain and anemia were more likely to have extensive and severe DD. Although relevant mechanisms are not yet well understood, this study improved our understandings of the pathophysiology for LDD.

Genetics of Intervertebral Disc Degeneration

PURPOSE OF REVIEW

Intervertebral disc degeneration is a contributor to chronic back pain. While a part of the natural aging process, early or rapid intervertebral disc degeneration is highly heritable. In this review, we summarize recent progress towards unraveling the genetics associated with this degenerative process.

RECENT FINDINGS

Use of large cohorts of patient data to conduct genome-wide association studies (GWAS) for intervertebral disc disease, and to lesser extent for aspects of this process, such as disc height, has resulted in a large increase in our understanding of the genetic etiology. Genetic correlation suggests that intervertebral disc disease is pleiotropic with risk factors for other diseases such as osteoporosis. The use of Mendelian Randomization is slowly establishing what are the causal relationships between intervertebral disc disease and factors previously correlated with this disease. The results from these human genetic studies highlight the complex nature of this disease and have the potential to lead to improved clinical management of intervertebral disc disease. Much additional work should now be focused on characterizing the causative relationship various co-morbid conditions have with intervertebral disc degeneration and on finding interventions to slow or halt this disease.

Elucidation of effect of spinopelvic parameters in degenerative disc disease

INTRODUCTION

This study aims to find out if there is any relationship between disc pathology and spinopelvic morphology, respectively.

METHODS

A total of 152 patients who complained about low back pain were assessed retrospectively. Patients were divided into three groups based on the presence of disc pathology: non-degenerative (ND) (n=34), degenerative disc disease (DDD) (n=80), and lumbar disc herniation (LDH) (n=38). Spinopelvic parameters were measured on the lateral standing radiographs using Surgimap® Software. The degree of degeneration of each disc was evaluated using T2-weighted images according to the Pfirmann classification. Correlation analyses were performed.

RESULTS

No significant difference was observed between the three groups in terms of sagittal spinal and pelvic parameters. Age and BMI were positively correlated with DDD and LDH. PI and proximal lombar lordosis (PLL) were the only effective variables in predicting DDD. PT and distal lumbar lordosis (DLL) were found to be effective variables in predicting LDH. PI and PT values in patients with L1, L2, and L3 DDD were statistically significantly higher than those without degeneration (P<0.05). Although there were no statistical differences between PI and PT values (P>0.05), DLL values in L4 and L5 DDD patients were significantly lower than those without degeneration (P=0.041; P=0.046; P<0.05).

CONCLUSIONS

The sagittal morphology of the spine directly influences the extent of lumbar disc degeneration. As the values of PI and PT increase, disc degeneration tends to occur at higher levels (L1-2-3). Disc degeneration at lower levels (L4-5) was associated with low DLL levels.

LEVEL OF EVIDENCE

Level III, retrospective study.

Relationship between lumbar disc degeneration on MRI and low back pain: A cross-sectional community study

Purpose:

Although an association has been suggested between disc degeneration (DD) and low back pain (LBP), some DD is thought to be an age-related change unrelated to symptoms. Age-inappropriate DD, however, may be associated with LBP. The purpose of this study was to investigate whether there is a difference in LBP and LBP-related quality of life between age-appropriate and age-inappropriate DD, as assessed by magnetic resonance imaging (MRI).

Participants and methods:

In this cross-sectional study, degenerative change in the lumbar intervertebral discs of 382 subjects (age range, 27-82 years) was evaluated by MRI. Degenerative Disc Disease (DDD) scores were assigned using the Schneiderman classification, as the sum of grades for all intervertebral levels (0-15). We classified subjects into three groups according to age and DDD score: Low DD (mild DD relative to age), Appropriate (age-appropriate DD), and High DD (severe DD relative to age). We compared the three groups in terms of LBP prevalence, LBP intensity, LBP-specific quality of life (QOL) according to the Roland-Morris Disability Questionnaire (RDQ), and the Short Form-36 Item Health Survey (SF-36).

Results:

Of 382 subjects, there were 35% in the Low DD group, 54% in the Appropriate group, and 11% in the High DD group. There were no significant differences among the groups in terms of prevalence of LBP, LBP intensity, RDQ score, or SF-36 score.

Conclusion:

No association was found between age-inappropriate DD (Low or High DD group) and age-appropriate DD (Appropriate group) in terms of prevalence of LBP, LBP intensity, RDQ, or SF-36.

Learning-based fully automated prediction of lumbar disc degeneration progression with specified clinical parameters and preliminary validation

BACKGROUND

Lumbar disc degeneration (LDD) may be related to aging, biomechanical and genetic factors. Despite the extensive work on understanding its etiology, there is currently no automated tool for accurate prediction of its progression.

PURPOSE

We aim to establish a novel deep learning-based pipeline to predict the progression of LDD-related findings using lumbar MRIs.

MATERIALS AND METHODS

We utilized our dataset with MRIs acquired from 1,343 individual participants (taken at the baseline and the 5-year follow-up timepoint), and progression assessments (the Schneiderman score, disc bulging, and Pfirrmann grading) that were labelled by spine specialists with over ten years clinical experience. Our new pipeline was realized by integrating the MRI-SegFlow and the Visual Geometry Group-Medium (VGG-M) for automated disc region detection and LDD progression prediction correspondingly. The LDD progression was quantified by comparing the Schneiderman score, disc bulging and Pfirrmann grading at the baseline and at follow-up. A fivefold cross-validation was conducted to assess the predictive performance of the new pipeline.

RESULTS

Our pipeline achieved very good performances on the LDD progression prediction, with high progression prediction accuracy of the Schneiderman score (Accuracy: 90.2 ± 0.9%), disc bulging (Accuracy: 90.4% ± 1.1%), and Pfirrmann grading (Accuracy: 89.9% ± 2.1%).

CONCLUSION

This is the first attempt of using deep learning to predict LDD progression on a large dataset with 5-year follow-up. Requiring no human interference, our pipeline can potentially achieve similar predictive performances in new settings with minimal efforts.

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.

Anemia was associated with multilevel lumbar disc degeneration in patients with low back pain: a single-center retrospective study

PURPOSE

It has not been determined which factors were related to multilevel lumbar disc degeneration (MLDD). The objective of this study was to determine the prevalence of MLDD among symptomatic patients using the magnetic resonance imaging method. The study also aimed to clarify the associations between MLDD and suspected risk factors through a multivariate model.

METHODS

A total of 530 young and middle-aged patients, suffered from low back pain were retrospectively assessed by 2 independent observers, who used sagittal T2-weighted MR imaging. Subjects were divided into two groups, MLDD group and non-MLDD group, according to the number of degenerated discs. Demographic and radiological data included age, gender, weight, height, body mass index, smoking status, alcohol drinking, lumbar lordosis, presence of hypertension (HT), diabetes mellitus and anemia.

RESULTS

There were 309 men and 221 women with an average age of 37.5  ±  8.5 years. In general, 37.7% of patients were diagnosed with disc degeneration (DD) at more than two levels. Triple level DD was the most common pattern and was more prevalent in women (p <0.05). Using multivariate analyses, age (odds ratio [OR]: 1.14; 95% confidence interval [CI] 1.11-1.18; p <0.001), hypertension (OR: 2.67; 95% CI 1.38-5.16; p = 0.03) and anemia (OR: 3.84; 95% CI 2.03-7.28; p <0.001) were significantly associated with MLDD.

CONCLUSION

Despite the young age of this cohort, MLDD is common among patients with low back pain. A significant independent association exists between age, HT, anemia and multilevel disc degeneration in the lumbar region.

Sodium Tanshinone IIA Sulfonate Ameliorates Injury-Induced Oxidative Stress and Intervertebral Disc Degeneration in Rats by Inhibiting p38 MAPK Signaling Pathway

Objective

Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of tanshinone IIA, a representative traditional Chinese medicine. The aim of the study was to investigate the capability of STS to reverse injury-induced intervertebral disc degeneration (IDD) and explore the potential mechanisms.

Methods

Forty adult rats were randomly allocated into groups (control, IDD, STS10, and STS20). An IDD model was established by puncturing the Co8-9 disc using a needle. Rats in the STS groups were administered STS by daily intraperitoneal injection (10 or 20 mg/kg body weight) while rats in the control and IDD groups received the same quantity of normal saline. After four weeks, the entire spine from each rat was scanned for X-ray and MRI analysis. Each Co8-9 IVD underwent histological analysis (H&E, Safranin-O Fast green, and alcian blue staining). A tissue was analyzed by immunohistochemical (IHC) staining to determine the expression levels of collagen II (COL2), aggrecan, matrix metalloproteinase-3/13 (MMP-3/13), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α). Levels of oxidative stress were measured using an ELISA while activity of the p38 MAPK pathway was assessed using Western blot analysis.

Results

Compared with the control group, needle puncture significantly decreased IVD volume and T-2 weighted MR signal intensity, confirming disc degeneration. These alterations were significantly attenuated by treatment with 10 or 20 mg/kg STS. Lower COL2 and aggrecan and higher MMP-3/13, IL-1β, IL-6, and TNF-α levels in the IDD group were substantially reversed by STS. In addition, treatment with STS increased antioxidative enzyme activity and decreased levels of oxidative stress induced by needle puncture. Furthermore, STS inhibited the p38 MAPK pathway in the rat model of IDD.

Conclusions

STS ameliorated injury-induced intervertebral disc degeneration and displayed anti-inflammatory and antioxidative properties in a rat model of IDD, possibly via inhibition of the p38 MAPK signaling pathway.

Tissue physiology revolving around the clock: circadian rhythms as exemplified by the intervertebral disc

Circadian clocks in the brain and peripheral tissues temporally coordinate local physiology to align with the 24 hours rhythmic environment through light/darkness, rest/activity and feeding/fasting cycles. Circadian disruptions (during ageing, shift work and jet-lag) have been proposed as a risk factor for degeneration and disease of tissues, including the musculoskeletal system. The intervertebral disc (IVD) in the spine separates the bony vertebrae and permits movement of the spinal column. IVD degeneration is highly prevalent among the ageing population and is a leading cause of lower back pain. The IVD is known to experience diurnal changes in loading patterns driven by the circadian rhythm in rest/activity cycles. In recent years, emerging evidence indicates the existence of molecular circadian clocks within the IVD, disruption to which accelerates tissue ageing and predispose animals to IVD degeneration. The cell-intrinsic circadian clocks in the IVD control key aspects of physiology and pathophysiology by rhythmically regulating the expression of ~3.5% of the IVD transcriptome, allowing cells to cope with the drastic biomechanical and chemical changes that occur throughout the day. Indeed, epidemiological studies on long-term shift workers have shown an increased incidence of lower back pain. In this review, we summarise recent findings of circadian rhythms in health and disease, with the IVD as an exemplar tissue system. We focus on rhythmic IVD functions and discuss implications of utilising biological timing mechanisms to improve tissue health and mitigate degeneration. These findings may have broader implications in chronic rheumatic conditions, given the recent findings of musculoskeletal circadian clocks.

LncRNA FAM83H-AS1 maintains intervertebral disc tissue homeostasis and attenuates inflammation-related pain via promoting nucleus pulposus cell growth through miR-22-3p inhibition

Background

Intervertebral disc degeneration (IVDD) is regarded as the leading cause of low back pain, resulting in disability and a heavy burden on public health. Several studies have unveiled that long noncoding RNAs (lncRNAs) play a key role in the pathogenesis and progression of IVDD. In this study, we aimed to investigate the biological function and latent molecular mechanism of the lncRNA FAM83H antisense RNA 1 (FAM83H-AS1) in IVDD development.

Methods

Firstly, we established an IVDD model in rats using advanced glycation end products (AGEs) intradiscal injection. Subsequently, gain-of-function assays were conducted to investigate the role of FAM83H-AS1 in the progression of IVDD. Bioinformatics analysis, RNA pull down assay and rescue experiments were employed to shed light on the molecular mechanism underlying FAM83H-AS1 involving in IVDD.

Results

Our findings verified that AGEs treatment aggravated IVDD damage, and FAM83H-AS1 was downregulated in the IVDD group. Additionally, overexpression of FAM83H-AS1 contributed to the growth of nucleus pulposus (NP) cells and ameliorated IVDD injury. It was revealed that FAM83H-AS1 possessed the speculated binding sites of miR-22-3p. More importantly, we confirmed that FAM83H-AS1 functioned as a sponge of miR-22-3p in IVDD. Lastly, we demonstrated that miR-22-3p mediated the impact of FAM83H-AS1 on cell proliferation, ECM degradation, and inflammation.

Conclusions

Our study indicated that FAM83H-AS1 relieved IVDD deterioration through sponging miR-22-3p, and provides novel insights into the mechanisms underlying FAM83H-AS1 in IVDD progression.

The treatment of intervertebral disc degeneration using Traditional Chinese Medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Intervertebral disc degeneration (IDD) is one of the most common causes of chronic low back pain that spending a lot of workforces and financial resources, seriously affecting human physical and mental health. Clinically used drug treatments and surgical treatments cannot fundamentally relieve the disease and have a risk of recurrence. Traditional Chinese Medicine (TCM) has a history of more than a thousand years in the prevention and treatment of IDD. However, so far, there are few reviews on the treatment of IDD by TCM. Therefore, it is crucial and necessary to systematically mine the existing literature on the treatment of IDD with TCM. This paper strives to systematically describe the modern medicine and TCM theoretical research on IDD, progress in the treatment of IDD and focuses on the treatment of IDD by TCM, which would lay some theoretical foundation and provide new directions for future research.

MATERIALS AND METHODS

Information on clinical observations, animal experiments and relevant pharmacology data about the treatment of IDD were gathered from various sources including traditional Chinese books and Chinese Pharmacopoeia, scientific databases (Elsevier, PubMed, Science Direct, Baidu Scholar, CNKI, Spring Link, Web of Science) and from different professional websites.

RESULTS

This review mainly introduces the current research on the theoretical research on IDD, the combination principle of the TCM formula, and the underlying mechanism of the formula and active ingredients.

CONCLUSIONS

At present, domestic and foreign scholars have carried out a lot of research in different ways, such as the molecular mechanism and predisposing factors of IDD, which provides theoretical development and clinical practice significance for future research. TCM, as a multi-component and multi-targeted drug, can produce synergistic effects to exert its efficacy. Therefore, the development of TCM with more specific functions and practical data will not only become a significant trend in the world market but also has an irreplaceable role in the future treatment of IDD.

No evidence of a correlation between lumbar spinal subtypes and intervertebral disc degeneration among asymptomatic middle-aged and aged patients

The aim of the present study was to identify whether lumbar spinal subtypes (LSS) were associated with lumbar disc degeneration (LDD) among asymptomatic middle-aged and aged subjects. A cohort of 158 asymptomatic Chinese adults aged >40 years was recruited and 97 volunteers that met the inclusion criteria with complete information available were selected for inclusion. According to spinal morphology, volunteers were divided into four subtypes based on the classification of Roussouly. After baseline information was collected and spinopelvic parameters were measured, the data were compared among the four groups. According to the Pfirrmann classification, the degree of LDD was evaluated at each level on the MRI. For grades I-V, LDD at each level was effectively compared. Each of the four LSS from I to IV according to Roussouly classification from types I to IV were comprised of 25 (25.8%), 19 (19.6%), 38 (39.2%) and 15 (15.5%) of volunteers, respectively. Lumbar lordosis, sacral slope and pelvic incidence were significantly different among the four sub-types (P<0.001 for each), but no difference in pelvic tilt was observed (P=0.21). From types I to IV LSS, the proportion of disc degeneration was found to be 44, 52, 50 and 48%, respectively, which exhibited no statistically significant difference among LSS. No correlation between LSS and intervertebral disc degeneration was obtained among the asymptomatic middle-aged and aged subjects. The present study provides a reference for spinal surgery and indicated that additional risk factors should be assessed in the asymptomatic population of this age group, particularly in terms of differentially expressed genes.

Long-term pain relief following percutaneous steroid treatment of spinal synovial cysts: a population-based cohort study

BACKGROUND

Spinal synovial cysts are fluid-filled sacs that develop after facet joint degeneration and can give rise to radicular pain. If resistant to conservative management, surgical decompression or percutaneous steroid treatment is usually recommended. Percutaneous treatment minimizes the risk of spinal instability, but it has been uncertain whether it provides any long-term symptom relief. Moreover, it is unclear whether cyst rupture provides any added benefit.

OBJECTIVE

To assess long-term pain relief in patients with spinal synovial cysts who were treated with percutaneous intra-articular steroid treatment without cyst rupture.

METHODS

A population-based cohort-study was conducted of all patients with symptomatic synovial cysts who were treated with percutaneous intra-articular steroid treatment without cyst rupture between 1995 and 2014.

RESULTS

Thirty-eight patients were included. All patients had variations of lower back and radicular pain. Intra-articular access was achieved in 35 (92%) patients, and there were no treatment-related complications. At short-term assessment, 30 (79%) had pain relief. During the median follow-up of 11 years, 12 (32%) patients showed sustained pain relief without the need for decompressive surgery.

CONCLUSIONS

Percutaneous intra-articular steroid treatment without cyst rupture is a safe treatment for symptomatic spinal synovial cysts and eliminates the need for surgery in a substantial number of patients. It can be suggested as a first line of treatment.

Loss of tenomodulin expression is a risk factor for age-related intervertebral disc degeneration

The intervertebral disc (IVD) degeneration is thought to be closely related to ingrowth of new blood vessels. However, the impact of anti-angiogenic factors in the maintenance of IVD avascularity remains unknown. Tenomodulin (Tnmd) is a tendon/ligament-specific marker and anti-angiogenic factor with abundant expression in the IVD. It is still unclear whether Tnmd contributes to the maintenance of IVD homeostasis, acting to inhibit vascular ingrowth into this normally avascular tissue. Herein, we investigated whether IVD degeneration could be induced spontaneously by the absence of Tnmd. Our results showed that Tnmd was expressed in an age-dependent manner primarily in the outer annulus fibrous (OAF) and it was downregulated at 6 months of age corresponding to the early IVD degeneration stage in mice. Tnmd knockout (Tnmd-/- ) mice exhibited more rapid progression of age-related IVD degeneration. These signs include smaller collagen fibril diameter, markedly lower compressive stiffness, reduced multiple IVD- and tendon/ligament-related gene expression, induced angiogenesis, and macrophage infiltration in OAF, as well as more hypertrophic-like chondrocytes in the nucleus pulposus. In addition, Tnmd and chondromodulin I (Chm1, the only homologous gene to Tnmd) double knockout (Tnmd-/- Chm1-/- ) mice displayed not only accelerated IVD degeneration, but also ectopic bone formation of IVD. Lastly, the absence of Tnmd in OAF-derived cells promoted p65 and matrix metalloproteinases upregulation, and increased migratory capacity of human umbilical vein endothelial cells. In sum, our data provide clear evidences that Tnmd acts as an angiogenic inhibitor in the IVD homeostasis and protects against age-related IVD degeneration. Targeting Tnmd may represent a novel therapeutic strategy for attenuating age-related IVD degeneration.

A population-based study identifies an association of THBS2 with intervertebral disc degeneration

OBJECTIVE

To clarify the genetic mechanisms underlying intervertebral disc degeneration (IDD), we examined the associations between single-nucleotide polymorphisms (SNPs) and indicated as coefficient of interaction term (IDD) in a general population in Japan.

METHODS

This was a cross-sectional study. In 1,605 participants, C2-3 to L5/S1 in the total spine magnetic resonance imaging (MRI) were evaluated using the Pfirrmann's scoring system. Disc scores of 4 and 5 were defined as IDD. Eight SNPs in eight genes associated with IDD were examined at each disc level, considering the non-genetic risk factors of age, sex, and body mass index (BMI).

RESULTS

The highest odds ratio was found for rs9406328 in the THBS2 gene at disc level T12-L1 (OR 1.27, 95%CI 1.05 to 1.53), and this association was strengthened after adjustment for age using logistic regression (OR 1.37, 95%CI 1.12 to 1.67). Among participants aged <50 years and 50-59, the average IDD score in those with 2 risk alleles of rs9406328 was markedly higher than in those with 0 or 1 risk allele, and the difference is much wider than the elderly participants. It indicates the genetic effect of rs9406328 is stronger in the younger age groups. Finally, multiple linear regression analyses of the association between rs9406328 and IDD, adjusted for age, sex, and BMI at each disc level, showed a statistical interaction between age and the number of risk alleles at C7-T1, T3-4 and T4-T5 as well as T12-L1.

CONCLUSION

CONCLUSION: The association between rs9406328 in THBS2 and IDD was replicated. The contributions of genetic and environmental factors to IDD differed by disc level.

Prognostic factors in the progression of intervertebral disc degeneration: Which patient should be targeted with regenerative therapies?

OBJECTIVE

Possible regenerative treatments for lumbar intervertebral disc degeneration (DD) are rapidly emerging. There is consensus that the patient that would benefit most has early-stage DD, with a predicted deterioration in the near future. To identify this patient, the aim of this study was to identify prognostic factors for progression of DD.

STUDY DESIGN

Systematic review.

METHODS

A systematic search was performed on studies evaluating one or more prognostic factor(s) in the progression of DD. The criteria for inclusion were (a) patients diagnosed with DD on MRI, (b) progression of DD at follow-up, and (c) reporting of one or more prognostic factor(s) in progression of DD. Two authors independently assessed the methodological quality of the included studies. Due to heterogeneity in DD determinants and outcomes, only a best-evidence synthesis could be conducted.

RESULTS

The search generated 3165 references, of which 16 studies met our inclusion criteria, involving 2.423 patients. Within these, a total of 23 clinical and environmental and 12 imaging factors were identified. There was strong evidence that disc herniation at baseline is associated with progression of DD at follow-up. There is limited evidence that IL6 rs1800795 genotype G/C male was associated with no progression of DD. Some clinical or environmental factors such as BMI, occupation and smoking were not associated with progression.

CONCLUSIONS

Disc herniation is strongly associated with the progression of DD. Surprisingly, there was strong evidence that smoking, occupation, and several other factors were not associated with the progression of DD. Only one genetic variant may have a protective effect on progression, otherwise there was conflicting or only limited evidence for most prognostic factors. Future research into these prognostic factors with conflicting and limited evidence is not only needed to determine which patients should be targeted by regenerative therapies, but will also contribute to spinal phenotyping.

Systematic identification of lncRNAs and circRNAs-associated ceRNA networks in human lumbar disc degeneration

Lumbar disc degeneration (LDD) is a common cause of low back and neck pain. The molecular mechanisms underlying LDD, however, are unclear. Noncoding RNAs have been reported to participate in human diseases. We investigated a series of public datasets (GSE67566, GSE56081 and GSE63492) and identified 568 mRNAs, 55 microRNAs (miRNAs), 765 long noncoding RNAs (lncRNAs), and 586 circular RNAs (circRNAs) that were expressed differently in LDD than in normal discs. We constructed lncRNAs and circRNAs regulated competing endogenous RNAs (ceRNA) networks in LDD. Four lncRNAs, DANCR, CASK-AS1, SCARNA2, and LINC00638), and three circRNAs, hsa_circ_0005139, hsa_circ_0037858, and hsa_circ_0087890, were identified as key regulators of LDD progression. We found that hsa-miR-486-5p regulated the crosstalk among circRNA hsa_circ_0000189, lncRNA DANCR and 6 mRNAs, PYCR2, TOB1, ARHGAP5, RBPJ, CD247, SLC34A1. Gene ontology (GO) analysis demonstrated that these differently expressed lncRNAs and circRNAs were involved in cellular component organization or biogenesis, gene expression and negative regulation of metabolic processes. Our findings provide useful information for exploring new mechanisms for LDD and candidates for therapeutic targets.

Endplate Defect Is Heritable, Associated With Low Back Pain and Triggers Intervertebral Disc Degeneration: A Longitudinal Study From TwinsUK

STUDY DESIGN

Longitudinal study of spine magnetic resonance imaging (MRI) in a large-scale population-based study.

OBJECTIVE

To determine the order of appearance of degenerative change in vertebral bodies and intervertebral discs. We also sought to define the influence of endplate defect on low back pain (LBP) and to determine whether there is a genetic influence on endplate defect.

SUMMARY OF BACKGROUND DATA

Endplate defect is a magnetic resonance imaging trait, found to be associated with intervertebral disc degeneration. There is a lack of understanding regarding the mechanism underlying lumbar disc degeneration (LDD). Recent attention has shifted to vertebral endplate defects and their role in spine degeneration pathology.

METHODS

Individuals from the TwinsUK spine study having longitudinal T2-weighted lumbar MR scans at baseline (n = 996) and a decade later (n = 438) were included. LDD, vertebral endplate defect by calculating a total endplate score, and Modic change (MC) were assessed using standard techniques. Mixed-effects models were used to determine the association between the features of spine pathology, adjusted for covariates. Endplate defect heritability was estimated using variance component analysis.

RESULTS

Significant association was found between endplate defect, LDD, MRI features of LDD and MC was observed. Endplate defect was associated with severe disabling LBP (P ≤ 0.013) in multivariate analysis. An association between disc degeneration (DD) at baseline and MC at follow-up was shown at upper lumbar levels. Total endplate score was heritable with estimated additive genetic component A = 55.3% (95% CI 43.0-65.4).

CONCLUSION

Endplate defect, LDD, and MC are all independent risk factors for episodes of severe and disabling LBP. Longitudinal analysis showed DD is followed by MC. Endplate defect has significant heritability of 55%. However, whether endplate defect triggers DD or these pathological changes occur concurrently could not be conclusively determined.

LEVEL OF EVIDENCE

2.

Genetic epidemiology and Mendelian randomization for informing disease therapeutics: Conceptual and methodological challenges

The past decade has been proclaimed as a hugely successful era of gene discovery through the high yields of many genome-wide association studies (GWAS). However, much of the perceived benefit of such discoveries lies in the promise that the identification of genes that influence disease would directly translate into the identification of potential therapeutic targets, but this has yet to be realized at a level reflecting expectation. One reason for this, we suggest, is that GWAS, to date, have generally not focused on phenotypes that directly relate to the progression of disease and thus speak to disease treatment.

A Whole Exome Study Identifies Novel Candidate Genes for Vertebral Bone Marrow Signal Changes (Modic Changes)

STUDY DESIGN

A family-based study.

OBJECTIVE

The aim of this study was to identify rare genetic factors predisposing to Modic changes (MCs).

SUMMARY OF BACKGROUND DATA

Lumbar disc degeneration (LDD) is one of the contributing factors behind low back pain (LBP). Lumbar MC visualized as bone marrow signal intensity changes on magnetic resonance imaging (MRI) represent a specific phenotype of LDD, which has a stronger association with LBP than LDD without MC.

METHODS

The study set consisted of two Finnish families: Family I included seven affected and four unaffected individuals and Family II eight affected and seven unaffected individuals. MCs were evaluated in 26 individuals using MRI. Whole exome sequencing was used to identify alleles cosegregating with MC. Annotate variation was used to carry out functional annotation of alleles and their frequencies were evaluated using 1000Genomes, Sequencing Initiative Suomi (SISu), and the Exome Aggregation Consortium (ExAC) databases.

RESULTS

We identified predisposing genetic alleles for MC in two Finnish families. In each family, only single allele cosegregated with MC. In Family I, the observed allele was an insertion and deletion in the HSPG2 gene, resulting in a premature termination codon. In Family II, a single nucleotide polymorphism (rs61753465) in the MAML1 gene was identified in all affected family members.

CONCLUSION

We have identified two novel candidate genes, MAML1 and HSPG2, associating with MC. These genes are important in cartilage structure and joint cartilage maintenance. Our findings are novel among lumbar spine degenerative phenotypes.

LEVEL OF EVIDENCE

N/A.

Progression, incidence, and risk factors for intervertebral disc degeneration in a longitudinal population-based cohort: the Wakayama Spine Study

OBJECTIVE

The present study examined the progression, incidence, and risk factors for intervertebral disc degeneration (DD) throughout the lumbar spine using magnetic resonance imaging (MRI) in a large population-based cohort.

METHODS

We followed up 617 subjects for more than 4 years as part of the Wakayama Spine Study. 1) "Progression of DD" in each of the entire, upper (L1/2 to L3/4) and lower (L4/5 and L5/S1) lumbar spine was defined as Pfirrmann grade progression at follow-up in at least one disc in the affected region. 2) "Incidence of DD" in each of these regions was defined if all discs were grade 3 or lower (white disc) at baseline, and at least one disc had progressed to grade 4 or higher (black disc) at follow-up. Logistic regression analyses were used to determine the risk factors for progression and incidence of DD.

RESULTS

DD progression and incidence in the entire lumbar spine were 52.0% and 31.6% in men, and 60.4% and 44.7% in women, respectively. Women was associated with DD progression in the upper lumbar spine (odds ratio [OR] = 1.68, 95% confidence interval [CI] = 1.18-2.42). Aging was associated with the incidence of DD in each region (entire: OR = 1.14, CI = 1.06-1.14; upper: OR = 1.10, CI = 1.05-1.15; lower: OR = 1.11, CI = 1.05-1.19). Diabetes mellitus (DM) was associated with the incidence of DD in the upper lumbar spine (OR = 6.83, CI = 1.07-133.7).

CONCLUSION

This 4-year longitudinal study is the first to demonstrate DD progression and incidence in the lumbar spine and their risk factors in a large population-based cohort.

Association of Mild Leg Length Discrepancy and Degenerative Changes in the Hip Joint and Lumbar Spine

OBJECTIVE

The purpose of this study was to evaluate the correlation between mild leg length discrepancy (LLD) and degenerative joint disease (DJD) or osteoarthritis.

METHODS

We evaluated standard postural lumbopelvic radiographs from 255 adults (121 women and 134 men) who had presented with spinal pain for chiropractic care. Symmetry of femoral head diameters was used to exclude magnification errors. Pearson's partial correlation was used to control for age and derive effect sizes for LLD on DJD in the hip and lower lumbar motion segments. Krippendorff's α was used for intraobserver and interobserver reliability.

RESULTS

A strong correlation was found between LLD and hip DJD in men (r = 0.532) and women (r = 0.246). We also found a strong correlation between LLD and DJD at the L5-S1 motion segment in men (r = 0.395) and women (r = 0.246). At the L4-5 spinal level this correlation was much attenuated in men (r = 0.229) and women (r = 0.166).

CONCLUSIONS

These findings suggest an association between LLD and hip and lumbar DJD. Cause-effect relationships between mild LLD and DJD deserve to be properly evaluated in future longitudinal cohort studies.

AGEs induce ectopic endochondral ossification in intervertebral discs

Ectopic calcifications in intervertebral discs (IVDs) are known characteristics of IVD degeneration that are not commonly reported but may be implicated in structural failure and dysfunctional IVD cell metabolic responses. This study investigated the novel hypothesis that ectopic calcifications in the IVD are associated with advanced glycation end products (AGEs) via hypertrophy and osteogenic differentiation. Histological analyses of human IVDs from several degeneration stages revealed areas of ectopic calcification within the nucleus pulposus and at the cartilage endplate. These ectopic calcifications were associated with cells positive for the AGE methylglyoxal-hydroimidazolone-1 (MG-H1). MG-H1 was also co-localised with Collagen 10 (COL10) and Osteopontin (OPN) suggesting osteogenic differentiation. Bovine nucleus pulposus and cartilaginous endplate cells in cell culture demonstrated that 200 mg/mL AGEs in low-glucose media increased ectopic calcifications after 4 d in culture and significantly increased COL10 and OPN expression. The receptor for AGE (RAGE) was involved in this differentiation process since its inhibition reduced COL10 and OPN expression. We conclude that AGE accumulation is associated with endochondral ossification in IVDs and likely acts via the AGE/RAGE axis to induce hypertrophy and osteogenic differentiation in IVD cells. We postulate that this ectopic calcification may play an important role in accelerated IVD degeneration including the initiation of structural defects. Since orally administered AGE and RAGE inhibitors are available, future investigations on AGE/RAGE and endochondral ossification may be a promising direction for developing non-invasive treatment against progression of IVD degeneration.

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.

Does type 2 diabetes mellitus promote intervertebral disc degeneration?

PURPOSE

LDD is an important cause of low back pain. Many people believe there is an adverse influence of type 2 diabetes (T2D) on lumbar intervertebral disc degeneration (LDD). We examined a population sample for epidemiological evidence of association.

METHODS

Twin volunteers from the TwinsUK cohort having spine magnetic resonance (MR) scans coded for LDD and information about T2D were investigated in two ways. First, as a population sample and second as a cotwin case control study in twin pairs discordant for T2D. Other risk factors for LDD considered were age, body-mass index (BMI), smoking, and alcohol.

RESULTS

In 956 twin volunteers T2D had a prevalence of 6.6 %. LDD score was higher in T2D twins (14.9 vs 13.1 p = 0.04) but was not an independent risk factor if the influence of age and BMI were included in the model. Discordant twin analysis (n = 33 pairs) showed no significant difference in LDD between twins having T2D and their unaffected cotwins.

CONCLUSIONS

Twins having T2D did manifest higher LDD scores but the effect was abrogated once BMI was included in multivariable analysis, showing it is not an independent risk factor for LDD. The population study had 80 % power at 0.1 significance level to detect a difference of 1.8 in LDD score (range of 0-60), so if there is an effect of T2D on LDD, it is likely to be small.

The relationship between obesity, low back pain, and lumbar disc degeneration when genetics and the environment are considered: a systematic review of twin studies

BACKGROUND CONTEXT

The relationships between obesity and low back pain (LBP) and lumbar disc degeneration (LDD) remain unclear. It is possible that familial factors, including genetics and early environment, affect these relationships.

PURPOSE

To investigate the relationship between obesity-related measures (eg, weight, body mass index [BMI]) and LBP and LDD using twin studies, where the effect of genetics and early environment can be controlled.

STUDY DESIGN

A systematic review with meta-analysis.

METHODS

MEDLINE, CINAHL, Scopus, Web of Science, and EMBASE databases were searched from the earliest records to August 2014. All cross-sectional and longitudinal observational twin studies identified by the search strategy were considered for inclusion. Two investigators independently assessed the eligibility, conducted the quality assessment, and extracted the data. Metaanalyses (fixed or random effects, as appropriate) were used to pool studies' estimates of association.

RESULTS

In total, 11 articles met the inclusion criteria. Five studies were included in the LBP analysis and seven in the LDD analysis. For the LBP analysis, pooling of the five studies showed that the risk of having LBP for individuals with the highest levels of BMI or weight was almost twice that of people with a lower BMI (odds ratio [OR] 1.8; 95% confidence interval [CI] 1.6-2.0; I(2)=0%). A dose-response relationship was also identified. When genetics and the effects of a shared early environment were adjusted for using a within-pair twin case-control analysis, pooling of three studies showed a reduced but statistically positive association between obesity and prevalence of LBP (OR 1.5; 95% CI 1.1-2.1; I(2)=0%). However, the association was further diminished and not significant (OR 1.4; 95% CI 0.8-2.3; I(2)=0%) when pooling included two studies on monozygotic twin pairs only. Seven studies met the inclusion criteria for LDD. When familial factors were not controlled for, body weight was positively associated with LDD in all five cross-sectional studies. Only two cross-sectional studies investigated the relationship between obesity-related measures and LDD accounting for familial factors, and the results were conflicting. One longitudinal study in LBP and three longitudinal studies in LDD found no increase in risk in obese individuals, whether or not familial factors were controlled for.

CONCLUSIONS

Findings from this review suggest that genetics and early environment are possible mechanisms underlying the relationship between obesity and LBP; however, a direct causal link between these conditions appears to be weak. Further longitudinal studies using the twin design are needed to better understand the complex mechanisms underlying the associations between obesity, LBP, and LDD.

Chronic ingestion of advanced glycation end products induces degenerative spinal changes and hypertrophy in aging pre-diabetic mice

Intervertebral disc (IVD) degeneration and pathological spinal changes are major causes of back pain, which is the top cause of global disability. Obese and diabetic individuals are at increased risk for back pain and musculoskeletal complications. Modern diets contain high levels of advanced glycation end products (AGEs), cyto-toxic components which are known contributors to obesity, diabetes and accelerated aging pathologies. There is little information about potential effects of AGE rich diet on spinal pathology, which may be a contributing cause for back pain which is common in obese and diabetic individuals. This study investigated the role of specific AGE precursors (e.g. methylglyoxal-derivatives (MG)) on IVD and vertebral pathologies in aging C57BL6 mice that were fed isocaloric diets with standard (dMG+) or reduced amounts of MG derivatives (dMG-; containing 60-70% less dMG). dMG+ mice exhibited a pre-diabetic phenotype, as they were insulin resistant but not hyperglycemic. Vertebrae of dMG+ mice displayed increased cortical-thickness and cortical-area, greater MG-AGE accumulation and ectopic calcification in vertebral endplates. IVD morphology of dMG+ mice exhibited ectopic calcification, hypertrophic differentiation and glycosaminoglycan loss relative to dMG- mice. Overall, chronic exposure to dietary AGEs promoted age-accelerated IVD degeneration and vertebral alterations involving ectopic calcification which occurred in parallel with insulin resistance, and which were prevented with dMG- diet. This study described a new mouse model for diet-induced spinal degeneration, and results were in support of the hypothesis that chronic AGE ingestion could be a factor contributing to a pre-diabetic state, ectopic calcifications in spinal tissues, and musculoskeletal complications that are more generally known to occur with chronic diabetic conditions.

Magnetic resonance imaging evaluation of L5-s1 intervertebral disc degeneration in Japanese women

Study Design

Retrospective case series.

Purpose

To calculate the prevalence of L5-S1 intervertebral disc degeneration (IDD) by evaluating gynecological disease findings, obtained by pelvic magnetic resonance imaging (MRI), and reveal the risk factors for IDD by analyzing its relationship with age, sacral structure, body mass index (BMI), number of deliveries, and intrapelvic space-occupying lesions.

Overview of Literature

Age, obesity, height, smoking history, occupation, and lumbosacral structure are reportedly the main factors of lumbar IDD. However, in women, the relationship of IDD with obstetric and gynecological history is unclear.

Methods

The presence of L5-S1 IDD was evaluated on sagittal T2-weighted pelvic MRI during gynecological evaluations in 660 Japanese women. We measured the sacral table angle (STA), sacral kyphosis angle (SKA), and intrapelvic space-occupying lesion size. Age, height, weight, BMI, number of deliveries, lumbosacral structure, size of space-occupying lesions, and presence of uterine leiomyoma based on medical records were compared between the IDD-positive and IDD-negative groups.

Results

Lumbosacral IDD was observed in 405 cases (61.4%), and its prevalence increased with age. Differences in age, height, weight, BMI, and number of deliveries between the IDD-positive and -negative groups were significant, but differences in STA, SKA, and presence of uterine leiomyoma and space-occupying lesion size were not. Logistic regression analysis indicated that age, BMI, and STA were risk factors for lumbosacral IDD.

Conclusions

Age is the biggest risk factor for lumbosacral IDD in Japanese women, with BMI and STA also contributing to its development. However, SKA and obstetric and gynecological history were not significantly involved.

Vertebral endplate change as a feature of intervertebral disc degeneration: a heritability study

PURPOSE

To study the prevalence of vertebral endplate or Modic change (MC), the progression of MC over a 10-year follow-up and the heritability of MC prevalence in a classical twin study.

METHODS

The study population was recruited from TwinsUK register between 1996 and 2000. MC was evaluated from T2-weighted lumbar magnetic resonance imaging (MRI) at baseline and follow-up. Heritability was estimated using variance components analysis. Baseline MRI with appropriate data was available for 831 twins and follow-up for 436 twins. In total, both baseline and follow-up imaging were available for 347 twins.

RESULTS

Mean age of the study population was 54.1 years (range 45.7-62.5) and females comprised 96%. The prevalence of MC at baseline was 32.1% and at follow-up 48.4%. The incidence of MC during the 10-year follow-up was 21.6% and was highest at L4-5 and L5-S1. MC regressed totally in 3.5% of twins. Twins with prevalent MC at baseline demonstrated a higher incidence of MC at upper lumbar levels during follow-up compared to twins without baseline MC (p = 0.009). Probandwise concordance rates were higher in monozygotic (0.56) than dizygotic twin pairs (0.39) suggestive of familial influence. Heritability of MC prevalence was estimated at 30 (16-43) %.

CONCLUSIONS

The results suggest that MC is generally progressive in middle age and furthermore is heritable. Since MC is associated with disc degeneration, which is also heritable, further work on potential shared mechanisms is needed.

Identification of novel nucleus pulposus markers: Interspecies variations and implications for cell-based therapiesfor intervertebral disc degeneration

Mesenchymal stem-cell based therapies have been proposed as novel treatments for intervertebral disc degeneration, a prevalent and disabling condition associated with back pain. The development of these treatment strategies, however, has been hindered by the incomplete understanding of the human nucleus pulposus phenotype and by an inaccurate interpretation and translation of animal to human research. This review summarises recent work characterising the nucleus pulposus phenotype in different animal models and in humans and integrates their findings with the anatomical and physiological differences between these species. Understanding this phenotype is paramount to guarantee that implanted cells restore the native functions of the intervertebral disc. Cite this article: Bone Joint Res 2013;2:169-78.

Genetics of disc-related disorders: current findings and lessons from other complex diseases

Disc-related disorders are highly genetic conditions with heritability estimates of up to 75 % and yet, few genomic locations have been moderately associated with the disorders. Candidate gene studies have shown possible disease associations on loci and genes of 1p21.1 (COL11A1), 6q27 (THBS2), 9q22.31 (ASPN), 10p12.31 (SKT), 20q11.2 (GDF5) and 20q13.12 (MMP9). More recently, in 2012, the first genome-wide association study revealed variants on loci and genes of 3p26.2, 6p21.32 (HLA region) and 6q26 (PARK2) that associate with disc-related disorders. In many other complex diseases, large meta-analyses of hundreds of thousands of study subjects and loci have revealed remarkable pathways. As methodology is evolving rapidly, we have already stepped into the era of routinely sequencing all bases in all human exons and we are approaching the era of sequencing the entire genome of study subjects with common diseases. The past decade has taught us that the common variants seen throughout populations seem to have low effects in many common diseases, explain relatively little of the overall heritability of the diseases and demand thousands of study subjects to identify associations. It seems that familial rare variants play an important role in many common diseases leading us back to valuing studies with large families and isolated populations. Moreover, careful characterization of environmental conditions are needed to explore and determine gene-environment interactions as genes that increase disease risk in one context may not do so under another context.

Disc height and sagittal alignment in operated and non-operated levels in the lumbar spine at long-term follow-up: a case-control study

Purpose:

To compare lumbar disc degeneration at 9-year follow-up in patients with chronic low back pain who had instrumented lumbar fusion or no fusion.

Material and methodology:

The main outcomes were disc height and sagittal alignment measured by Distortion Compensated Roentgen Analysis (DCRA). Secondary outcome included the Oswestry Disability Index and VAS back pain.

Results:

Forty-eight patients with baseline and 9-year radiographs from L2- S1 were included. Twenty-three had lumbar fusion and 25 had no fusion. Disc height was reduced at all levels independent of fusion. No difference in disc height and sagittal alignment was observed between patients fused and not fused. There were weak correlations, ranging from 0.04 to 0.36, between clinical and radiological parameters.

Conclusion:

Lumbar disc degeneration increased at all measured levels independent of fusion and correlated poorly with clinical outcome.

A retrospective analysis of vertebral body fractures following epidural steroid injections

BACKGROUND

Lumbar epidural steroid injections (LESIs) are frequently prescribed for the treatment of radiculopathy or neurogenic claudication arising from compression of spinal nerves. However, there is evidence suggesting that corticosteroids adversely affect bone strength by diminishing new bone formation and increasing bone resorption. Our study sought to assess whether LESIs increase the risk of subsequent vertebral body fracture.

METHODS

A retrospective cohort study was conducted to compare patients receiving LESIs with a control group. A total of 50,345 patients with ICD-9 (International Classification of Diseases, Ninth Revision) diagnosis codes involving the spine were identified by searching a corporate database, and 3415 of these were found to have received at least one LESI. We randomly selected a study population of 3000 patients from the injected population, and we selected a matched cohort of 3000 patients from the non-injected group with use of propensity matching. The incidence of vertebral body fractures in each group was assessed with use of survival analysis.

RESULTS

There was no significant difference between the injected and non-injected groups with respect to age, predicted propensity score, sex, race, hyperthyroidism, or steroid use. In the survival analysis, an increasing number of injections was associated with an increasing likelihood of fractures. Each successive injection increased the risk of fracture by a factor of 1.21 (95% confidence interval, 1.08 to 1.30) after adjustment for covariates (p = 0.003).

CONCLUSIONS

The findings suggest that LESIs, like other forms of exogenous steroid administration, may lead to increased bone fragility. The added exposure to glucocorticoids resulting from LESI use may carry a greater risk than previously thought, suggesting that use of LESIs should be approached cautiously in patients at risk for osteoporotic fractures.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Combined anti-inflammatory and anti-AGE drug treatments have a protective effect on intervertebral discs in mice with diabetes

Objective

Diabetes and low back pain are debilitating diseases and modern epidemics. Diabetes and obesity are also highly correlated with intervertebral disc (IVD) degeneration and back pain. Advanced-glycation-end-products (AGEs) increase reactive-oxygen-species (ROS) and inflammation, and are one cause for early development of diabetes mellitus. We hypothesize that diabetes results in accumulation of AGEs in spines and associated spinal pathology via increased catabolism. We present a mouse model showing that: 1) diabetes induces pathological changes to structure and composition of IVDs and vertebrae; 2) diabetes is associated with accumulation of AGEs, TNFα, and increased catabolism spinal structures; and 3) oral-treatments with a combination of anti-inflammatory and anti-AGE drugs mitigate these diabetes-induced degenerative changes to the spine.

Methods

Three age-matched groups of ROP-Os mice were compared: non-diabetic, diabetic (streptozotocin (STZ)-induced), or diabetic mice treated with pentosan-polysulfate (anti-inflammatory) and pyridoxamine (AGE-inhibitor). Mice were euthanized and vertebra-IVD segments were analyzed by μCT, histology and Immunohistochemistry.

Results

Diabetic mice exhibited several pathological changes including loss in IVD height, decreased vertebral bone mass, decreased glycosaminoglycan content and morphologically altered IVDs with focal deposition of tissues highly expressing TNFα, MMP-13 and ADAMTS-5. Accumulation of larger amounts of methylglyoxal suggested that AGE accumulation was associated with these diabetic degenerative changes. However, treatment prevented or reduced these pathological effects on vertebrae and IVD.

Conclusion

This is the first study to demonstrate specific degenerative changes to nucleus pulposus (NP) morphology and their association with AGE accumulation in a diabetic mouse model. Furthermore, this is the first study to demonstrate that oral-treatments can inhibit AGE-induced ROS and inflammation in spinal structures and provide a potential treatment to slow progression of degenerative spine changes in diabetes. Since diabetes, IVD degeneration, and accumulation of AGEs are frequent consequences of aging, early treatments to reduce AGE-induced ROS and Inflammation may have broad public-health implications.

Association of abdominal obesity with lumbar disc degeneration--a magnetic resonance imaging study

Purpose

To evaluate whether midsagittal (abdominal) obesity in magnetic resonance imaging (MRI), waist circumference (WC) and body fat percentage are associated with lumbar disc degeneration in early adulthood.

Methods

We obtained the lumbar MRI (1.5-T scanner) of 325 females and 233 males at a mean age of 21 years. Lumbar disc degeneration was evaluated using Pfirrmann classification. We analysed the associations of MRI measures of obesity (abdominal diameter (AD), sagittal diameter (SAD), ventral subcutaneous thickness (VST), and dorsal subcutaneous thickness (DST)), WC and body fat percentage with disc degeneration sum scores using ordinal logistic regression.

Results

A total of 155 (48%) females and 147 (63%) males had disc degeneration. AD and SAD were associated with a disc degeneration sum score of ≥3 compared to disc degeneration sum score of 0–2 (OR 1.67; 95% confidence interval (CI) 1.20–2.33 and OR 1.40; 95% CI 1.12–1.75, respectively) among males, but we found no association among females. WC was also associated with disc degeneration among males (OR 1.03 per one cm; 95% CI 1.00–1.05), but not among females.

Conclusion

Measures of abdominal obesity in MRI and waist circumference were associated with disc degeneration among 21-year-old males.

Ageing, genes, environment and epigenetics: what twin studies tell us now, and in the future

Compared with younger people, older people are much more variable in their organ function, and these large individual differences contribute to the complexity of geriatric medicine. What determines this variability? Is it due to the accumulation of different life experiences, or because of the variation in the genes we are born with, or an interaction of both? This paper reviews key findings from ageing twin cohorts probing these questions. Twin studies are the perfect natural experiment to dissect out genes and life experiences. We discuss the paradox that ageing is strongly determined by heritable factors (an influence that often gets stronger with time), yet longevity and lifespan seem not to be so heritable. We then focus on the intriguing question of why DNA sequence-identical twins might age differently. Animal studies are increasingly showing that epigenetic modifications occurring in early development and adulthood, might be key to ageing phenomena but this is difficult to investigate longitudinally in human populations, due to ethical problems of intervention and long lifespan. We propose that identical twin studies using new and existing cohorts may be useful human models in which to investigate the interaction between the environment and genetics, mediated by epigenetic modifications.

Gender difference in genetic association between IL1A variant and early lumbar disc degeneration: a three-year follow-up

OBJECTIVE

The purpose of the present study was to analyze the associations between specific genetic markers and early disc degeneration (DD) or early disc degeneration progression (DDP) defined by magnetic resonance imaging (MRI).

METHODS

We selected eleven of the most promising single nucleotide polymorphisms (SNP) and compared the distributions of these genetic markers between groups defined by MRI in a Danish adolescent population (N=166) over a three-year follow-up period.

RESULTS

We observed a ten-fold higher annual incidence of endplate changes than previously reported in adults. The gender difference in IL1A rs1800587 association with DD remained significant and another association with DDP emerged in follow-up assessment. Among girls, the rs1800587 T-allele was associated both with DD (OR 2.82 [95% CI 1.29-6.16]) and with DDP (OR 2.45 [95% CI 1.03-5.82]). Among boys, the IL6 rs1800795 genotype G/C was protective in both DD (OR 0.26 [95% CI 0.09-0.72]) and DDP (OR 0.32 [95% CI 0.12-0.88]) with the IL6 rs1800797 genotype G/A was associated with a decreased likelihood of DD (OR 0.27 [95% CI 0.10-0.77]). Gender-genotype interactions were significant for polymorphisms in both IL1A and IL6. Correction for multiple testing weakened the associations for IL6 polymorphisms.

CONCLUSION

We conclude that gender specific effects in lumbar disc degeneration and its progression are possible. However, further evaluations in larger populations are needed. Our results provide some support to the hypothesis that early disc degeneration is an especially important phase in the cascade of degenerative disc disease.

Incidence and risk factors for radiographic lumbar spondylosis and lower back pain in Japanese men and women: the ROAD study

OBJECTIVE

To determine the incidence of radiographic lumbar spondylosis (LS)and lower back pain, and their risk factors in Japan using a large-scale population from the nationwide cohort Research on Osteoarthritis/osteoporosis Against Disability (ROAD) Study.

METHODS

Participants in the ROAD study who had been recruited between 2005 and 2007 were followed up with lumbar spine radiography for 3 years. A total of 2,282 paired radiographs (75% of the original sample) were scored using Kellgren and Lawrence (KL) grades, and the incidence and progression rate of radiographic LS was analyzed. The incidence of lower back pain was also examined. In addition, associations between risk factors and incident and progressive radiographic LS as well as incident lower back pain were tested.

RESULTS

Given a 3.3-year follow-up, the incidence of KL≥2 radiographic LS was 50.0% and 34.4% (15.3% and 10.5% per year), while that of KL≥3 LS was 15.3% and 23.7% (4.6% and 7.2% per year) in men and women, respectively. The progression rate of LS was 20.5% and 27.4% (6.2% and 8.3% per year) in men and in women, respectively. In addition, the incidence of lower back pain was 28.3% and 31.2% (8.6% and 9.5% per year) in men and women. Lower back pain was not significantly associated with incident radiographic LS, while a more severe KL grade at baseline was associated with incident lower back pain.

CONCLUSION

The present longitudinal study revealed a high incidence of radiographic LS in Japan.