COL9A2 allelotypes in intervertebral disc disease

Targeting Autophagy for Developing New Therapeutic Strategy in Intervertebral Disc Degeneration

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

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.

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

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

Association of COL9A3 trp3 polymorphism with intervertebral disk degeneration: a meta-analysis

BACKGROUND

Intervertebral disk degeneration (IDD) is a common musculoskeletal disease associated with genetic factors. COL9A3 gene encodes the α3 (IX) chain of type IX collagen that is part of the interior structure of the disc. Mutations in COL9A3 gene sequence, leading to an Arg103Trp substitution in its 3 chain (the Trp3 allele at rs61734651 site), respectively, have been found to be connected with IDD occurrence in several studies. However, those studies have showed conflict results. Thus, a meta-analysis has been performed to assess the associations between the COL9A3 trp3 polymorphism and IDD.

METHODS

Data were gathered from the following four electronic databases: PubMed, Web of Science (WOS), Embase and Cochrane library up to January 01, 2018. The pooled odds ratio (polled ORs) and 95% confidence interval (CI) were calculated to evaluate the strength of relationship between the COL9A3 trp3 polymorphism and IDD.

RESULTS

Eleven eligible studies with 1631 cases of IDD and 1366 controls were included in this meta-analysis. The results indicated that the COL9A3 trp3 polymorphism was not associated with IDD (trp3 positive versus trp3 negative: OR = 1.31, 95%CI = 0.78-2.21, P = 0.309). Furthermore, the Egger's test and the Begg funnel plot did not show any evidence of publication bias.

CONCLUSIONS

Our results suggest that the COL9A3 trp3 polymorphism might not be associated with IDD. Nor did we find any relationship in subgroup analyses stratified by gender and ethnicity. Future researches with larger samples are required to verify this outcome.

Genetic background of degenerative disc disease in the lumbar spine

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

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

STUDY DESIGN

Prospective genetic association study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

4.

Genetic Factors in Intervertebral Disc Degeneration

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Meta-analysis of the association between COL9A2 genetic polymorphisms and lumbar disc disease susceptibility

STUDY DESIGN

Meta-analysis to collect all the relevant studies to date to further investigate whether or not the COL9A2 gene rs12077871, rs12722877, and rs7533552 polymorphism are associated with susceptibility to lumbar disc disease (LDD).

OBJECTIVE

The aim of this study was to assess the association between the COL9A2 gene rs12077871, rs12722877, and rs7533552 and LDD.

SUMMARY OF BACKGROUND DATA

LDD is a common musculoskeletal disease with strong genetic determinants. COL9A2 encodes the α2 (IX) chain of type IX collagen, which is the major collagen component of the hyaline cartilage. Growing numbers of studies have revealed the association between COL9A2 polymorphisms and susceptibility to LDD. However, those studies have yielded contradictory results.

METHODS

Data were collected from the following electronic databases: PubMed, Web of Knowledge, and China National Knowledge Infrastructure, with the last report up to November 30, 2013. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength of association under the allelic genetic model. We summarized the data on the association between COL9A2 rs12077871, rs12722877, and rs7533552 polymorphism and LDD in the overall studies.

RESULTS

Nine case-control studies, including 1522 LDD cases and 1646 controls, were identified. The results indicated that the rs12077871, rs12722877, and rs7533552 variants in COL9A2 were not associated with LDD (rs12077871: C vs. T, OR = 0.541, 95% CI = 0.256-1.147, P = 0.109; rs12722877: C vs. G, OR = 1.199, 95% CI = 0.992-1.448, P = 0.06; rs7533552: A vs. G, OR = 0.993, 95% CI = 0.815-1.069, P = 0.320). Furthermore, the Egger test and the Begg funnel plot did not show any evidence of publication bias.

CONCLUSION

Our results suggest that the COL9A2 rs12077871, rs12722877, and rs7533552 polymorphisms may not be associated with LDD. More studies based on larger sample sizes and homogeneous samples of patients with LDD are needed to confirm these findings.

LEVEL OF EVIDENCE

2.

The role of polymorphisms of genes encoding collagen IX and XI in lumbar disc disease

The intervertebral disc disease (IDD) is one of the most common musculoskeletal disorders. A number of environment and anthropometric risk factors may contribute to it. The recent reports have suggested the importance of genetic factors, especially these which encode collagen types IX and XI. The allelic variants in the collagen IX genes - COL9A2 (Trp2) and COL9A3 (Trp3) have been identified as genetic risk factors for IDD, because they interfere the cross-linking between collagen types II, IX and XI and result in decreased stability of intervertebral discs. Type XI collagen is a minor component of cartilage collagen fibrils, but it is present in the annulus fibrosus and nucleus pulposus of intervertebral discs. Some studies have shown the association between gene COL11A1 polymorphism c.4603C>T and IDD. The frequency of 4603T allele was significantly higher in the patients with IDD than in the healthy controls.

Genetic polymorphisms associated with intervertebral disc degeneration

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

Literature review.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Absence of the mutated Trp2 allele but a common polymorphism of the COL9A2 collagen gene is associated with early recurrence after lumbar discectomy in a German population

Genetic factors seem to play a role in symptomatic lumbar disc disease (LDD). It has been shown previously that a tryptophan mutation of the COL9A2 gene is a major risk factor for LDD in a Finish population. The impact of collagen gene variations on the relapse rate after lumbar discectomy, however, has not been studied so far. Here, we conducted a cross-sectional genotyping study of patients who underwent lumbar discectomy to determine the influence of a COL9A2 mutation on the recurrence rates. Biopsy samples from 288 patients suffering from LDD with and without relapse were analyzed by PCR restriction fragment analysis and direct sequencing. The mutated Trp2 allele was not detected in the patients' samples of the present study. However, nine patients with recurrent LDD, but only two without recurrence were homozygous for the Arg allele. Homozygosity for the Arg allele of Col9A2 seems to be more frequent in the patient group with early recurrence although the differences in the allele frequencies were statistically not significant. In contrast, the Trp2 mutation seems not to be a major susceptibility factor for LDD in a German population.

Association study of COL9A2 with lumbar disc disease in the Japanese population

Lumbar disc disease (LDD) is a common musculo-skeletal disease with strong genetic determinants. In a Finnish population, a single nucleotide polymorphism (SNP) causing an amino-acid substitution (Trp2 allele) in COL9A2, which encodes the alpha2 (IX) chain of type IX collagen, has been reported to associate with LDD. However, replication studies in different populations have produced controversial results. To further investigate the association of COL9A2 with LDD in Japanese, we examined SNPs in COL9A2, including Trp2, in 470 LDD patients (mean age 35) along with 658 controls (mean age 48). We identified a total of 43 sequence variations in COL9A2. Nine SNPs, including Trp2, were selected and genotyped. After Bonferroni's correction, none of these SNPs showed association. Unlike observations in the Finnish population, Trp2 was common in Japanese, and no association with LDD was apparent. However, we did see association of a COL9A2 specific haplotype with LDD (P=0.025; permutation test); this association is more significant in patients with severe lumbar disc degeneration (P=0.011). Thus, the association of Trp2 with LDD was not replicated, but COL9A2 susceptibility allele(s) other than Trp2 may be present in Japanese LDD.

Biology of intervertebral disc aging and degeneration: involvement of the extracellular matrix

STUDY DESIGN

A review of current knowledge and opinions concerning the biologic changes that take place during development, maturation and degeneration of the intervertebral disc.

OBJECTIVE

To provide an overview of the changes that occur in structure and composition of the extracellular matrix of the intervertebral disc and to explain the origin of such changes and their functional consequences.

SUMMARY OF BACKGROUND DATA

The structure of the intervertebral disc, and, in particular, the composition of its extracellular matrix, changes throughout life, ultimately resulting in tissue degeneration in the adult.

METHODS

A review of the published scientific literature.

RESULTS

In the young disc, the outer anulus fibrosus and inner nucleus pulposus have clear physical and molecular properties, although these differences become less distinct in the adult. The age changes are due to variations in both the abundance and structure of the macromolecules, particularly aggrecan, and the structural variations may be due to changes in both synthesis and degradation. It is not clear how many of the changes are by design to adapt to the altered environment of the growing spine. However, it is commonly thought that the degradative changes are detrimental to disc function, a property that is exacerbated by the inability of the mature avascular disc to remove and replace accumulated degradation products. The rate at which these detrimental changes occur may vary between individuals because of genetic, biomechanical, and nutritional differences. Such changes are thought to form the basis of tissue loss associated with disc degeneration.

CONCLUSION

Changes in intervertebral disc structure throughout life ultimately result in tissue degeneration and the need for medical intervention. Current research is aimed at trying to restore the integrity of the degenerate disc matrix by biologic means, although at present it is not clear what the structure of the most appropriate repair tissue should be or how it can be achieved.

The role of collagen IX tryptophan polymorphisms in symptomatic intervertebral disc disease in Southern European patients

STUDY DESIGN

We conducted a cross-sectional, genotyping study of intervertebral disc disease patients and controls.

OBJECTIVES

To determine the contribution of COL9A2 and COL9A3 Tryptophan polymorphisms to intervertebral disc disease development in a genetically heterogeneous, Southern European population compared to previous Finnish studies.

SUMMARY OF BACKGROUND DATA

The COL9A2 and COL9A3 genes encode the alpha2 and alpha3 chains of Collagen IX. Recent Finnish studies suggest that a tryptophan polymorphism in the COL9A2 gene (Trp2) results in hereditary intervertebral disc disease, whereas a similar tryptophan mutation in COL9A3 (Trp3) conveys a 3-fold risk of intervertebral disc disease.

METHODS

We studied 105 symptomatic patients with radiographically and/or surgically proven lumbar (98%, n = 103) or cervical (2%, n = 2) intervertebral disc disease and 102 age-matched controls without spinal complaints from hospitals in Athens, Greece. Intervertebral disc disease was defined as significant disc herniation resulting in persistent back or leg pain. We genotyped all patients for COL9A2 and COL9A3 allele variations using a polymerase chain reaction-based technique.

RESULTS

None of our patients had the Trp2 allele. Consistent with previous Finnish findings, more Greek intervertebral disc disease cases (8.6%) than controls (4.9%) had at least 1 Trp3 allele, but this difference did not reach statistical significance (P = 0.293). The allele frequency of the Trp3 mutation was significantly higher among previously studied Finnish patients with intervertebral disc disease (12.3%) than among the Southern European patients with intervertebral disc disease in our study (4.3%), P = 0.001.

CONCLUSIONS

The differences in Trp allele frequency we found between Greek and Finnish patients with intervertebral disc disease most likely represent true differences in polymorphism prevalence between the respective populations. The 2 previously described Trp alleles in COL9A2 and COL9A3 are likely to be less significant susceptibility factors for intervertebral disc disease development in Southern European populations.

Matrix deposition of tryptophan-containing allelic variants of type IX collagen in developing human cartilage

Genetic polymorphisms that encode a tryptophan (Trp) residue in the triple-helical domain of the alpha2 (Trp2) or alpha3 chain (Trp3) of human type IX collagen have been linked to risk of degenerative intervertebral disc disease. To determine whether these two allelic variants express protein that may affect the extracellular matrix of cartilage in vivo, we examined the properties of resident type IX collagen in an anonymous collection of embryonic and fetal human cartilage samples screened for Trp genotypes. No difference was found in the yield and electrophoretic properties of pepsin-solubilized type IX collagen between Trp2, Trp3 and non-Trp cartilage samples. On Western blot analysis, a polyclonal antiserum raised against a synthetic peptide matching the immediate Trp-containing sequence of the Trp3 allele reacted specifically with the alpha3(IX) chain prepared from Trp3 cartilage samples. Two-dimensional peptide mapping of type IX collagen in CNBr-digests of whole tissue gave indistinguishable fingerprints for Trp2, Trp3 and control tissues, including the yield of cross-linked peptides. Analysis of one cartilage sample that was homozygous for the Trp2 allele also gave a normal yield of collagen IX, including its alpha2 chain and a normal profile of cross-linked peptides. Together, the findings indicate that both Trp2 and Trp3 allelic products are incorporated into the cross-linked fibrillar network of developing human cartilage apparently normally. Any pathological consequences are likely, therefore, to be long-term and indirect rather than from overt misassembly of matrix.

Clinical phenotype and molecular diagnosis of multiple epiphyseal dysplasia with relative hip sparing during childhood (EDM2)

We report on a family of 19 individuals over four generations in which 12 members are affected with a variant of multiple epiphyseal dysplasia. Beginning in childhood, the disease leads to pain and stiffness of knees, ankles, elbows and finger joints. Some adult patients repeatedly suffer from free articular bodies resulting in locking of the joint. Finally, affected individuals are prone to the development of early degenerative joint disease. Mutation screening of candidate regions revealed a novel point mutation at position -1 in the COL9A2 exon 3/intron 3 splicing region. This G --> C substitution most probably induces an alteration of the splicing process. Family screening was carried out by both automated sequencing and by digestion of amplicons with BsaWI. We confirmed the nucleotide substitution in eight clinically affected family members as well as in three presymptomatic young children. Electron microscopy showed that the diameter of collagen fibrils from arthroscopically removed free articular bodies of two patients was not obviously different from that of normal articular cartilage. Together with previous reports our results indicate that mutations leading to skipping of exon 3 within the COL3 domain of the alpha2-chain of collagen type IX may be relatively common in patients with a special subtype of multiple epiphyseal dysplasia (MED) in which the hips are not markedly affected at early age (EDM2). In these patients and their families, mutation screening of the candidate regions may help to confirm the diagnosis, lead to appropriate advice for lifestyle and well based genetic counseling.

Recent advances in disc cell biology

STUDY DESIGN

There have been many advances over the past decade in understanding and experimentally modulating biologic aspects of intervertebral disc cell function. An overview of the current state of this biologic research is presented.

OBJECTIVES

To provide clinicians with a review of important recent advances in biologic studies of the disc and their implications for potential disc therapies.

SUMMARY OF BACKGROUND DATA

Historically, anatomic, biochemical, radiologic, and biomechanical studies of the intervertebral disc formed the foundation on which our understanding of disc function was built. Magnetic resonance imaging techniques that allowed viewing of soft tissue components of the disc further advanced imaging capabilities.

METHODS

Recent publications are reviewed.

RESULTS

Experimental approaches over the past decade have enabled researchers to look more critically at disc cell function. This is important because disc cell function produces the extracellular matrix components of the disc, which, in turn, shape the disc's subsequent physiologic and biomechanical functions. New approaches to the study of disc cell function, methods to manipulate disc cells, studies of intact discs and disc nutrition, vertebral endplate structure and function, tissue engineering, gene therapy, and the potential of stem cells in disc therapy are reviewed and discussed.

CONCLUSIONS

Many believe that disc degeneration has a cellular basis. New research is helping us better understand healthy, aging, and degenerating discs. Modern methods to manipulate and modulate disc cell function open exciting and challenging new therapeutic possibilities for future biologic treatments of disc degeneration.