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

Neuroinflammation at the Neuroforamina and Spinal Cord in Patients with Painful Cervical Radiculopathy and Pain-Free Participants: An [11C]DPA713 PET/CT Proof-of-Concept Study

Background/Objectives: The complex pathophysiology of painful cervical radiculopathy is only partially understood. Neuroimmune activation in the dorsal root ganglion and spinal cord is assumed to underlie the genesis of radicular pain. Molecular positron emission tomography (PET) using the radiotracer [11C]DPA713, which targets the 18-kDa translocator protein (TSPO), offers the ability to quantify neuroinflammation in humans in vivo. The primary objectives of this study were to (1) assess whether uptake of [11C]DPA713, a metric of neuroinflammation, is higher in the neuroforamina and spinal cord of patients with painful cervical radiculopathy compared with that in pain-free participants and (2) assess whether [11C]DPA713 uptake is associated with clinical parameters, such as pain intensity. Methods: Dynamic 60 min [11C]DPA713 PET/CT scans were acquired, and regions of interest were defined for neuroforamina and spinal cord. Resulting time-activity curves were fitted to a single-tissue compartment model using an image-derived input function, corrected for plasma-to-whole blood ratios and parent fractions, to obtain the volume of distribution (VT) as the primary outcome measure. Secondary neuroinflammation metrics included 1T2k VT without metabolite correction (1T2k_WB) and Logan VT. Results: The results indicated elevated levels of 1T2k VT at the neuroforamina (p < 0.04) but not at the spinal cord (p = 0.16). Neuroforamina and spinal cord 1T2k VT lack associations with clinical parameters. Secondary neuroinflammatory metrics show associations with clinical parameters such as the likelihood of neuropathic pain. Conclusions: These findings enhance our understanding of painful cervical radiculopathy's pathophysiology, emphasizing the neuroforamina levels of neuroinflammation as a potential therapeutic target.

What does degeneration at the cervicothoracic junction tell us? A kinematic MRI study of 93 individuals

PURPOSE

Current decision-making in multilevel cervical fusion weighs the potential to protect adjacent levels and reduce reoperation risk by crossing the cervicothoracic junction (C7/T1) against increased operative time and risk of complication. Careful planning is required, and the planned distal and adjacent levels should be assessed for degenerative disc disease (DDD). This study assessed whether DDD at the cervicothoracic junction was associated with DDD, disc height, translational motion, or angular variation in the adjacent superior (C6/C7) or inferior (T1/T2) levels.

METHODS

This study retrospectively analyzed 93 cases with kinematic MRI. Cases were randomly selected from a database with inclusion criteria being no prior spine surgery and images having sufficient quality for analysis. DDD was assessed using Pfirrmann classification. Vertebral body bone marrow lesions were assessed using Modic changes. Disc height was measured at the mid-disc in neutral and extension. Translational motion and angular variation were calculated by assessing translational or angular motion segment integrity respectively in flexion and extension. Statistical associations were assessed with scatterplots and Kendall's tau.

RESULTS

DDD at C7/T1 was positively associated with DDD at C6/C7 (tau = 0.53, p < 0.01) and T1/T2 (tau = 0.58, p < 0.01), with greater disc height in neutral position at T1/T2 (tau = 0.22, p < 0.01), and with greater disc height in extended position at C7/T1 (tau = 0.17, p = 0.04) and at T1/T2 (tau = 0.21, p < 0.01). DDD at C7/T1 was negatively associated with angular variation at C6/C7 (tau = - 0.23, p < 0.01). No association was appreciated between DDD at C7/T1 and translational motion.

CONCLUSION

The association of DDD at the cervicothoracic junction with DDD at the adjacent levels emphasizes the necessity for careful selection of the distal level in multilevel fusion in the distal cervical spine.

AN ANALYTICAL REVIEW OF CONTRIBUTORY FACTORS IN INTERVERTEBRAL DISC DEGENERATION

ABSTRACT Objective: To summarize current trends in the pathogenesis and management of disc degeneration and suggest areas where more research would be of benefit. Methods: The available literature relevant to Lumbar disc degeneration (LDD) was reviewed. PubMed, MEDLINE, OVID, EMBASE, Cochrane, and Google Scholar databases were used to review the literature. Institutional Review Board approval was not applicable for this study. Results: This article summarizes trends in the pathogenesis and factors associated with disc degeneration. Conclusions: The genetic contribution to lumbar disc degeneration is a newer concept, still being researched in different populations around the world. Investigators have demonstrated a familial predisposition in the etiology of lumbar disc degeneration. The effect sizes of most genetic variants are small and, thus, individual gene-environment studies must have very large sample sizes to provide compelling evidence of any interaction. Level of evidence; Narrative review of available literature.

Towards Tissue-Specific Stem Cell Therapy for the Intervertebral Disc: PPARδ Agonist Increases the Yield of Human Nucleus Pulposus Progenitor Cells in Expansion

(1) Background: Low back pain (LBP) is often associated with intervertebral disc degeneration (IVDD). Autochthonous progenitor cells isolated from the center, i.e., the nucleus pulposus, of the IVD (so-called nucleus pulposus progenitor cells (NPPCs)) could be a future cell source for therapy. The NPPCs were also identified to be positive for the angiopoietin-1 receptor (Tie2). Similar to hematopoietic stem cells, Tie2 might be involved in peroxisome proliferator-activated receptor delta (PPARδ) agonist-induced self-renewal regulation. The purpose of this study was to investigate whether a PPARδ agonist (GW501516) increases the Tie2+ NPPCs’ yield within the heterogeneous nucleus pulposus cell (NPC) population. (2) Methods: Primary NPCs were treated with 10 µM of GW501516 for eight days. Mitochondrial mass was determined by microscopy, using mitotracker red dye, and the relative gene expression was quantified by qPCR, using extracellular matrix and mitophagy-related genes. (3) The NPC’s group treated with the PPARδ agonist showed a significant increase of the Tie2+ NPCs yield from ~7% in passage 1 to ~50% in passage two, compared to the NPCs vehicle-treated group. Furthermore, no significant differences were found among treatment and control, using qPCR and mitotracker deep red. (4) Conclusion: PPARδ agonist could help to increase the Tie2+ NPCs yield during NPC expansion.

Integrated transcriptome and proteome analyses identify novel regulatory network of nucleus pulposus cells in intervertebral disc degeneration

BACKGROUND

Degeneration of intervertebral disc is a major cause of lower back pain and neck pain. Studies have tried to unveil the regulatory network using either transcriptomic or proteomic analysis. However, neither have fully elucidated the exact mechanism of degeneration process. Since post-transcriptional regulation may affect gene expression by modulating the translational process of mRNA to protein product, a combined transcriptomic and proteomic study may provide more insight into the key regulatory network of Intervertebral disc degeneration.

METHODS

In order to obtain the proteomic and transcriptomic data, we performed label-free proteome analysis on freshly isolated nucleus pulposus cells and obtained transcriptome profiling data from the Gene Expression Omnibus repository. To identify the key regulatory network of intervertebral disc degeneration in nucleus pulposus cells, we performed bioinformatic analyses and established a protein-RNA interacting network. To validate the candidate genes, we performed in vitro experimentation and immunochemistry labeling to identify their potential function during nucleus pulposus degeneration.

RESULTS

The label-free proteome analysis identified altogether 656 proteins, and 503 of which were differentially expressed between nucleus pulposus cells from degenerated or normal disc cells. Using the existing nucleus pulposus transcriptomic profiling data, we integrated the proteomic and transcriptomic data of nucleus pulposus cells, and established a protein-RNA interacting network to show the combined regulatory network of intervertebral disc degeneration. In the network, we found 9 genes showed significant changes, and 6 of which (CHI3L1, KRT19, COL6A2, DPT, TNFAIP6 and COL11A2) showed concordant changes in both protein and mRNA level. Further functional analysis showed these candidates can significantly affect the degeneration of the nucleus pulposus cell when altering their expression.

CONCLUSIONS

This study is the first to use combined analysis of proteomic and transcriptomic profiling data to identify novel regulatory network of nucleus pulposus cells in intervertebral disc degeneration. Our established protein-RNA interacting network demonstrated novel regulatory mechanisms and key genes that may play vital roles in the pathogenesis of intervertebral disc degeneration.

Current perspectives on the role of biomechanical loading and genetics in development of disc degeneration and low back pain; a narrative review

Degenerative changes in the disc have long been of interest; they are thought to be strongly associated with low back pain and caused by inappropriate loading or through injury. However, independent of the magnitude of occupational spinal loading, twin studies find that the heritability of lumbar disc degeneration is 34-74%. This finding has led to intensive searches for susceptibility genes; some genes associated with disc degeneration have been identified, though all with small effects on the degenerative process. The complex nature of degenerative changes suggests that many different genes are involved, and that interactions with environmental factors are influential in progression of degeneration. Low back pain itself also appears heritable (30-46%). The most important clinical question though, is not how discs degenerate but is disc degeneration related to low back pain. Imaging studies find many people with degenerate discs or even with discs showing pathological features such as herniations, are asymptomatic. However results are obscured by the lack of consistent definitions of the phenotypes of disc degeneration and of low back pain. Epidemiological studies could help disentangle these complex relationships, but they will only be successful once consistent classifications and phenotypes of both disc degeneration and low back pain are developed.

Genome-wide analysis of DNA methylation profile identifies differentially methylated loci associated with human intervertebral disc degeneration

BACKGROUND

Environmental and endogenous factors under genetic predisposition are considered to initiate the human intervertebral disc (IVD) degeneration. DNA methylation is an essential mechanism to ensure cell-specific gene expression for normal development and tissue stability. Aberrant epigenetic alterations play a pivotal role in several diseases, including osteoarthritis. However, epigenetic alternations, including DNA methylation, in IVD degeneration have not been evaluated. The purpose of this study was to comprehensively compare the genome-wide DNA methylation profiles of human IVD tissues, specifically nucleus pulpous (NP) tissues, with early and advanced stages of disc degeneration.

METHODS

Human NP tissues were used in this study. The samples were divided into two groups: early stage degeneration (n = 8, Pfirrmann's MRI grade: I-III) and advanced stage degeneration (n = 8, grade: IV). Genomic DNA was processed for genome-wide DNA methylation profiling using the Infinium MethylationEPIC BeadChip array. Extraction of raw methylation data, clustering and scatter plot of each group values of each sample were performed using a methylation module in GenomeStudio software. The identification of differentially methylated loci (DMLs) and the Gene Ontology (GO) analysis were performed using R software with the ChAMP package.

RESULTS

Unsupervised hierarchical clustering revealed that early and advanced stage degenerated IVD samples segregated into two main clusters by their DNA methylome. A total of 220 DMLs were identified between early and advanced disc degeneration stages. Among these, four loci were hypomethylated and 216 loci were hypermethylated in the advanced disc degeneration stage. The GO enrichment analysis of genes containing DMLs identified two significant GO terms for biological processes, hemophilic cell adhesion and cell-cell adhesion.

CONCLUSIONS

We conducted a genome-wide DNA methylation profile comparative study and observed significant differences in DNA methylation profiles between early and advanced stages of human IVD degeneration. These results implicate DNA methylation in the process of human IVD degeneration.

Redefining lumbar spinal stenosis as a developmental syndrome: does age matter?

OBJECTIVE

Age is commonly thought to be a risk factor in defining lumbar spinal stenosis (LSS) degenerative or developmental subtypes. This article is a follow-up to a previous article ("Redefining Lumbar Spinal Stenosis as a Developmental Syndrome: An MRI-Based Multivariate Analysis of Findings in 709 Patients Throughout the 16- to 82-Year Age Spectrum") that describes the radiological differences between developmental and degenerative types of LSS. MRI-based analysis of "degeneration" variables and spinal canal morphometric characteristics of LSS segments have been thought to correlate with age at presentation.

METHODS

The authors performed a re-analysis of data from their previously reported prospective MRI-based study, stratifying data from the 709 cases into 3 age categories of equal size (instead of the original < 60 vs ≥ 60 years). Relative spinal canal dimensions, as well as radiological degenerative variables from L1 to S1, were analyzed across age groups in a multivariate mode. The total degenerative scale score (TDSS) for each lumbar segment from L1 to S1 was calculated for each patient. The relationships between age and qualitative stenosis grades, TDSS, disc degeneration, and facet degeneration were analyzed using Pearson's product-moment correlation and multiple regression.

RESULTS

Multivariate analysis of TDSS and spinal canal dimensions revealed highly significant differences across the 3 age groups at L2-3 and L3-4 and a weaker, but still significant, association with changes at L5-S1. Age helped to explain only 9.6% and 12.2% of the variance in TDSS at L1-2 and L2-3, respectively, with a moderate positive correlation, and 7.8%, 1.2%, and 1.9% of the variance in TDSS at L3-4, L4-5, and L5-S1, respectively, with weak positive correlation. Age explained 24%, 26%, and 18.4% of the variance in lumbar intervertebral disc (LID) degeneration at L1-2, L2-3, and L3-4, respectively, while it explained only 6.2% and 7.2% of the variance of LID degeneration at L4-5 and L5-S1, respectively. Age explained only 2.5%, 4.0%, 1.2%, 0.8%, and 0.8% of the variance in facet degeneration at L1-2, L2-3, L3-4, L4-5, and L5-S1, respectively.

CONCLUSIONS

Age at presentation correlated weakly with degeneration variables and spinal canal morphometries in LSS segments. Age correlated with upper lumbar segment (L1-4) degeneration more than with lower segment (L4-S1) degeneration. The actual chronological age of the patients did not significantly correlate with the extent of degenerative pathology of the lumbar stenosis segments. These study results lend support for a developmental contribution to LSS.

Genetic Influence in Disc Degeneration - Systematic Review of Literature

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

Discogenic Back Pain: Literature Review of Definition, Diagnosis, and Treatment

Discogenic back pain is multifactorial; hence, physicians often struggle to identify the underlying source of the pain. As a result, discogenic back pain is often hard to treat—even more so when clinical treatment strategies are of questionable efficacy. Based on a broad literature review, our aim was to define discogenic back pain into a series of more specific and interacting pathologies, and to highlight the need to develop novel approaches and treatment strategies for this challenging and unmet clinical need. Discogenic pain involves degenerative changes of the intervertebral disc, including structural defects that result in biomechanical instability and inflammation. These degenerative changes in intervertebral discs closely intersect with the peripheral and central nervous systems to cause nerve sensitization and ingrowth; eventually central sensitization results in a chronic pain condition. Existing imaging modalities are nonspecific to pain symptoms, whereas discography methods that are more specific have known comorbidities based on intervertebral disc puncture and injection. As a result, alternative noninvasive and specific diagnostic methods are needed to better diagnose and identify specific conditions and sources of pain that can be more directly treated. Currently, there are many treatments/interventions for discogenic back pain. Nevertheless, many surgical approaches for discogenic pain have limited efficacy, thus accentuating the need for the development of novel treatments. Regenerative therapies, such as biologics, cell‐based therapy, intervertebral disc repair, and gene‐based therapy, offer the most promise and have many advantages over current therapies. © 2019 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research

Redefining lumbar spinal stenosis as a developmental syndrome: an MRI-based multivariate analysis of findings in 709 patients throughout the 16- to 82-year age spectrum

OBJECTIVEUsing an imaging-based prospective comparative study of 709 eligible patients that was designed to assess lumbar spinal stenosis (LSS) in the ages between 16 and 82 years, the authors aimed to determine whether they could formulate radiological structural differences between the developmental and degenerative types of LSS.METHODSMRI structural changes were prospectively reviewed from 2 age cohorts of patients: those who presented clinically before the age of 60 years and those who presented at 60 years or older. Categorical degeneration variables at L1-S1 segments were compared. A multivariate comparative analysis of global radiographic degenerative variables and spinal dimensions was conducted in both cohorts. The age at presentation was correlated as a covariable.RESULTSA multivariate analysis demonstrated no significant between-groups differences in spinal canal dimensions and stenosis grades in any segments after age was adjusted for. There were no significant variances between the 2 cohorts in global degenerative variables, except at the L4-5 and L5-S1 segments, but with only small effect sizes. Age-related degeneration was found in the upper lumbar segments (L1-4) more than the lower lumbar segments (L4-S1). These findings challenge the notion that stenosis at L4-5 and L5-S1 is mainly associated with degenerative LSS.CONCLUSIONSIntegration of all the morphometric and qualitative characteristics of the 2 LSS cohorts provides evidence for a developmental background for LSS. Based on these findings the authors propose the concept of LSS as a developmental syndrome with superimposed degenerative changes. Further studies can be conducted to clarify the clinical definition of LSS and appropriate management approaches.

Clinical Relationship of Degenerative Changes between the Cervical and Lumbar Spine

Study Design

Retrospective, observational, case series.

Purpose

To elucidate the prevalence of degenerative changes in the cervical and lumbar spine and estimate the degenerative changes in the cervical spine based on the degeneration of lumbar disc through a retrospective review of magnetic resonance (MR) images.

Overview of Literature

Over 50% of middle-aged adults show evidence of spinal degeneration. However, the relationship between degenerative changes in the cervical and lumbar spine has yet to be elucidated.

Methods

A retrospective review of positional MR images of 152 patients with symptoms related to cervical and lumbar spondylosis with or without a neurogenic component was conducted. The degree of intervertebral disc degeneration (IDD) was assessed on a grade of 1–5 for each segment of the cervical and lumbar spine using MR T2-weighted sagittal images. The grades across all segments were summed to produce the degenerative disc score (DDS) for the cervical and lumbar spine. The patients were divided into two groups based on the IDD grade for each lumbar segment: normal (grades 1 and 2) and degenerative (grades 3–5).

Results

DDSs for the cervical and lumbar spine were positively correlated. Significant differences in cervical DDSs between the groups were observed in all lumbar segments. Although there were no significant differences in cervical DDSs among the degenerative lumbar segment, cervical DDSs at the L1–2 and L2–3 segments tended to be higher than those at the L3–4, L4–5, and L5–S degenerative segments.

Conclusions

Our study shows that participants with degenerative changes in the upper lumbar segments are more likely to have a certain amount of cervical spondylosis. This information could be used to lower the incidence of a missed diagnosis of cervical spine disorders in patients presenting with lumbar spine symptomology.

Sequencing and bioinformatics analysis of the differentially expressed genes in herniated discs with or without calcification

The purpose of this study was to detect the differentially expressed genes between ossified herniated discs and herniated discs without ossification. In addition, we sought to identify a few candidate genes and pathways by using bioinformatics analysis. We analyzed 6 samples each of ossified herniated discs (experimental group) and herniated discs without ossification (control group). Purified mRNA and cDNA extracted from the samples were subjected to sequencing. The NOISeq method was used to statistically identify the differentially expressed genes (DEGs) between the 2 groups. An in-depth analysis using bioinformatics tools based on the DEGs was performed using Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein-protein interaction network analysis. The top 6 DEGs were verified using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A total of 132 DEGs was detected. A total of 129 genes in the ossified group were upregulated and 3 genes were found to be downregulated as compared to the control group. The top 3 cellular components in GO ontologies analysis were extracellular matrix components. GO functions were mainly related to the glycoprotein in the cell membrane and extracellular matrix. The GO process was related to completing response to stimulus, immune reflex and defense. The top 5 KEGG enrichment pathways were associated with infection and inflammation. Three of the top 20 DEGs [sclerostin (SOST), WNT inhibitory factor 1 (WIF1) and secreted frizzled related protein 4 (SFRP4)] were related to the inhibition of the Wnt pathway. The ossified discs exhibited a higher expression of the top 6 DEGs [SOST, joining chain of multimeric IgA and IgM (IGJ; also known as JCHAIN), defensin alpha 4 (DEFA4), SFRP4, proteinase 3 (PRTN3) and cathepsin G (CTSG)], with the associated P-values of 0.045, 0.000, 0.008, 0.010, 0.015 and 0.002, respectively, as calculated by the independent sample t-test. The gene expression profiling of the 2 groups revealed differential gene expression. Thus, our data suggest that Wnt pathway abnormality and local inflammation may be related to disc ossification.

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.

Cervical radiculopathy

Cervical radiculopathy is a common clinical scenario. Patients with radiculopathy typically present with neck pain, arm pain, or both. We review the epidemiology of cervical radiculopathy and discuss the diagnosis of this condition. This includes an overview of the pertinent findings on the patient history and physical examination. We also discuss relevant clinical syndromes that must be considered in the differential diagnosis including peripheral nerve entrapment syndromes and shoulder pathology. The natural history of cervical radiculopathy is reviewed and options for management are discussed. These options include conservative management, non-operative modalities such as physical therapy, steroid injections, and operative intervention. While the exact indications for surgical intervention have not yet been elucidated, we provide an overview of the available literature regarding indications and discuss the timing of intervention. The surgical outcomes of anterior cervical decompression and fusion (ACDF), cervical disc arthroplasty (CDA), and posterior cervical foraminotomy (PCF) are discussed.

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 Associations of Primary Angle-Closure Disease: A Systematic Review and Meta-analysis

TOPIC

Systematic review and meta-analysis of the genetic associations of primary angle-closure disease (PACD).

CLINICAL RELEVANCE

To confirm the genetic biomarkers for PACD, including primary angle-closure glaucoma (PACG) and related phenotypes.

METHODS

We searched in the MEDLINE and EMBASE databases for genetic studies of PACG or other PACD published from the start dates of the databases to May 11, 2015. We estimated the summary odds ratios (ORs) and 95% confidence intervals (CIs) for each polymorphism in PACG, primary angle-closure suspect (PACS), and primary angle-closure (PAC) using fixed- or random-effect models. We also performed sensitivity analysis to test the robustness of the results.

RESULTS

Our literature search yielded 6463 reports. Among them, we identified 24 studies that fulfilled the eligibility criteria for meta-analysis, involving 28 polymorphisms in 11 genes/loci. We affirmed the association of PACG and combined PACS/PAC/PACG with 10 polymorphisms in 8 genes/loci, including COL11A1 (rs3753841-G, OR, 1.22; P = 0.00046), HGF (rs17427817-C, OR, 2.02; P = 6.9E-07; rs5745718-A, OR, 2.11; P = 9.9E-07), HSP70 (rs1043618, GG+GC, OR, 0.52; P = 0.0010), MFRP (rs2510143-C, OR, 0.66; P = 0.012; rs3814762-G, OR, 1.40; P = 0.0090), MMP9 (rs3918249-C, OR, 1.35; P = 0.034), NOS3 (rs7830-A, OR, 0.80; P = 0.036), PLEKHA7 (rs11024102-G, OR, 1.24; P = 8.3E-05), and PCMTD1-ST18 (rs1015213-A, OR, 1.59; P = 0.00013). Sensitivity analysis indicated that the results were robust.

CONCLUSIONS

In this study, we confirmed multiple polymorphisms in 8 genes/loci as genetic biomarkers for PACD, among which 3 were identified in a genome-wide association study (COL11A1, PLEKHA7, and PCMTD1-ST18), and 5 were identified in candidate gene studies (HGF, HSP70, MFRP, MMP9, and NOS3).

Decreased Zn(2+) Influx Underlies the Protective Role of Hypoxia in Rat Nucleus Pulposus Cells

Zn(2+) is an essential component of metalloproteinases, and is required for their activity in cartilage; however, the effect of Zn(2+) on nucleus pulposus (NP) cells has not been widely investigated. The aim of this paper was to investigate the effect of intracellular Zn(2+) concentration ([Zn(2+)]i) in hypoxia-induced regulation of metalloproteinases (MMPs) and extracellular matrix (ECM) production in NP cells. NP cells from Sprague-Dawley (SD) rats were cultured as monolayers or in alginate beads. [Zn(2+)]i was assayed by FluoZin-3 AM staining. Alcian Blue staining, immunochemistry, 1,9-dimethylmethylene blue (DMMB) assay, and real-time PCR were used to assay collagen II, proteoglycan, and COL2A1, MMP-13, and ADAMTS-5 mRNA expression. ZIP8, a main Zn(2+) transporter in chondrocytes, was assayed by immunochemistry and in Western blotting. Interleukin (IL)-1β- and ZnCl2-induced increases of [Zn(2+)]i were significantly inhibited by hypoxia. Hypoxia did not reverse a decline of ECM expression caused by IL-1β and ZnCl2 in monolayer cultures, but did significantly attenuate the decreases of proteoglycan, glycosaminoglycan (GAG), and COL2A1 mRNA expression following IL-1β and ZnCl2 treatment in alginate bead cultures. However, ZnCl2 inhibited the protective effect of hypoxia. Both an intracellular Zn(2+) chelator and hypoxia prevented the increase in MMP-13 mRNA expression. IL-1β and ZnCl2 treatment increased ZIP8 expression in NP cells, and hypoxia inhibited ZIP8 expression. In conclusion, decrease of Zn(2+) influx mediates the protective role of hypoxia on ECM and MMP-13 expression. Consequently, changes in intracellular Zn(2+) concentration maybe involved in intervertebral disc degeneration.

Lumbar spinal stenosis is a highly genetic condition partly mediated by disc degeneration

Objective. Lumbar spinal stenosis is one of the most commonly diagnosed spinal disorders in older adults. Although the pathophysiology of the clinical syndrome is not well understood, a narrow central canal or intervertebral foramen is an essential or defining feature. The aim of the present study was to estimate the magnitude of genetic versus environmental influences on central lumbar spinal stenosis and to investigate disc degeneration and stature or bone development as possible genetic pathways.Methods. A classic twin study with multivariate analyses considering lumbar level and other covariates was conducted. The study sample comprised 598 male twins (147 monozygotic and 152 dizygotic pairs), 35-70 years of age, from the population-based Finnish Twin Cohort. The primary phenotypes were central lumbar stenosis as assessed qualitatively on magnetic resonance imaging (MRI) and quantitatively measured dural sac cross-sectional area. Additional phenotypes (to examine possible genetic pathways) included disc bulging and standing height, as an indicator of overall skeletal size or development.Results. The heritability estimate (h²) for qualitatively assessed central lumbar spinal stenosis on MRI was 66.9% (95% confidence interval [95% CI] 56.8,74.5). The broad-sense heritability estimate for dural sac cross-sectional area was 81.2% (95% CI 74.5, 86.1),with a similar magnitude of genetic influences across lumbar levels (h²=72.4–75.6). The additive genetic correlation of quantitatively assessed stenosis and disc bulging was extremely high. There was no indication of shared genetic influences between stenosis and stature.Conclusion. Central lumbar spinal stenosis and associated dural sac dimensions are highly genetic, and disc degeneration (bulging) appears to be one pathway through which genes influence spinal stenosis.