Toward a biochemical understanding of human intervertebral disc degeneration and herniation. Contributions of nitric oxide, interleukins, prostaglandin E2, and matrix metalloproteinases

Molecular therapy of the intervertebral disc

Disc degeneration is the loss of the normal nucleus pulposus disc matrix to a more fibrotic and less cartilaginous structure. This change in disc micro-anatomy can be associated with pain and deformity, however, prevention and treatment options of disc degeneration are currently limited. Much research is going on to understand intervertebral discs at a molecular/ cellular level in hopes of creating clinically applicable options for treating disc degeneration. This review article will give insight into the current and developing status of treating intervertebral disc degeneration from a molecular standpoint.

The vertebral endplate: disc degeneration, disc regeneration

The vertebral endplates are critical for maintaining disc function yet like other components of the disc are vulnerable to degeneration. This paper provides an overview of the development and normal function of the endplates as well as an impression of what happens when they undergo progressive degeneration. Recent research suggests that the degenerative process can be retarded or reversed.

Comparison of cellular response in bovine intervertebral disc cells and articular chondrocytes: effects .of lipopolysaccharide on proteoglycan metabolism

Lipopolysaccharide (LPS) induces matrix degradation and markedly stimulates the production of several cytokines, i.e., interleukin-1beta, -6, and -10, by disc cells and chondrocytes. We performed a series of experiments to compare cellular responses of cells from the bovine intervertebral disc (nucleus pulposus and annulus fibrosus) and from bovine articular cartilage to LPS. Alginate beads containing cells isolated from bovine intervertebral discs and articular cartilage were cultured with or without LPS in the presence of 10% fetal bovine serum. The DNA content and the rate of proteoglycan synthesis and degradation were determined. In articular chondrocytes, LPS strongly suppressed cell proliferation and proteoglycan synthesis in a dose-dependent manner and stimulated proteoglycan degradation. Compared with articular chondrocytes, nucleus pulposus cells responded in a similar, although less pronounced manner. However, treatment of annulus fibrosus cells with LPS showed no significant effects on proteoglycan synthesis or degradation. A slight, but statistically significant, inhibition of cell proliferation was observed at high concentrations of LPS in annulus fibrosus cells. Thus, LPS suppressed proteoglycan synthesis and stimulated proteoglycan degradation by articular chondrocytes and nucleus pulposus cells. The effects of LPS on annulus fibrosus cells were minor compared with those on the other two cell types. The dissimilar effects of LPS on the various cell types suggest metabolic differences between these cells and may further indicate a divergence in pathways of LPS signaling and a differential sensitivity to exogenous stimuli such as LPS.

Cervical intervertebral disc degeneration induced by unbalanced dynamic and static forces: a novel in vivo rat model

STUDY DESIGN

Establishment of a novel in vivo animal model of cervical spondylosis.

OBJECTIVE

To investigate apoptotic, degenerative, and inflammatory changes occurring in the cervical intervertebral discs of rats.

SUMMARY OF BACKGROUND DATA

Cervical degeneration occurs as the result of imbalance of both static and dynamic spinal stabilizers. The disc degeneration that occurs is characterized by increased local inflammation and increased apoptosis of intervertebral disc cells.

METHODS

By excising the paraspinal musculature and posterior cervical spinal ligaments of rats, both static and dynamic cervical stabilizers were disrupted. The resultant biomechanical imbalance resulted in biochemical and histologic changes, which were characterized by light microscopy, electron microscopy, immunostaining, enzyme-linked immunosorbent assay, polymerase chain reaction, and in situ hybridization.

RESULTS

Histologic analysis showed characteristic degenerative changes of the intervertebral discs and vertebral endplates following surgery. Ultrastructural examination revealed apoptotic changes, which were verified by immunostaining. Instability also resulted in significant up-regulation of inflammatory factors, as shown by enzyme-linked immunosorbent assay, polymerase chain reaction, and in situ hybridization.

CONCLUSIONS

By creating static and dynamic posterior instability of the cervical spine, this novel model of cervical spondylosis results in rapid intervertebral disc degeneration characterized by increased apoptosis and local inflammation, such as that seen clinically.

Expression of ADAMTS-4 (aggrecanase-1) and possible involvement in regression of lumbar disc herniation

STUDY DESIGN

Examination of ADAMTS-4 expression, and cellular lineages, distribution, and numbers of ADAMTS-4 (aggrecanase-1) expressing cells in herniated lumbar intervertebral discs.

OBJECTIVE

To determine the expression of ADAMTS-4, a metalloproteinase capable of digesting aggrecan, and its role in herniated lumbar intervertebral disc degradation.

SUMMARY OF BACKGROUND DATA

Matrix metalloproteinases degrade extracellular matrix of herniated discs, but the mechanism of aggrecan degradation, the major component of intervertebral discs, is poorly understood.

METHODS

Surgically resected herniated lumbar intervertebral discs from 22 patients were subclassified into protrusion, subligamentous extrusion, transligamentous extrusion, and sequestration types. Reverse transcriptase polymerase chain reaction, Western blot, and immunohistochemistry were used to evaluate ADAMTS-4 messenger ribonucleic acid and protein expression.

RESULTS

Expression of ADAMTS-4 messenger ribonucleic acid and protein was shown in the samples of herniated lumbar intervertebral discs. Immunohistochemical staining showed that ADAMTS-4 was mainly localized in CD68-positive mononuclear cells in granulation and adjacent disc tissues. ADAMTS-4 positive cell counts were significantly higher in transligamentous extrusion and sequestration than protrusion and subligamentous extrusion types. Alcian blue staining showed a decrease of proteoglycan in transligamentous extrusion and sequestration cases.

CONCLUSIONS

Macrophages infiltrating granulation and adjacent disc tissues express ADAMTS-4, suggesting its involvement in herniated disc regression.

Cytokine Assay of the Epidural Space Lavage in Patients With Lumbar Intervertebral Disk Herniation and Radiculopathy

INTRODUCTION

Lumbar disk herniation may result in a radiculopathic pattern of symptoms. Consideration for a primary biochemical inducement of pain over a mechanical mechanism is a contemporary topic of spinal research. However, the exact pathomechanism by which a degenerative intervertebral disk leads to neural inflammation and pain has not been determined. Using modern techniques of chemical analysis, biochemical markers can be identified which participate in the degenerative cascade, and possibly with the onset of pain. The purpose of this research is to identify potential biochemical markers through a novel technique of epidural space lavage that may be helpful in understanding the pathogeneses of pain in the presence of intervertebral disk degeneration and herniation.

METHODS

Fifty consecutive patients with acute radiculopathy secondary to a symptomatic herniated lumbar intervertebral disk or spinal stenosis, and who were indicated for epidural steroid injection were identified. Additionally, 3 volunteers with no history of back pain or radiculopathy volunteered to undergo epidural lavage. After needle insertion, a lavage followed by fluid aspiration of the epidural space at the level of the disc herniation, in the case of the symptomatic patients, was performed using normal saline, before the instillation of corticosteroids. The fluid samples were frozen at -20 degrees C until analysis. A biochemical evaluation for a battery of cytokines was undertaken (IL-1beta, IL-1ra, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p40, IL-13, IL-15, IL-17, TNF-alpha, IFN-alpha, IFN-gamma, GM-CSF, MIP-1alpha, MIP-1beta, IP-10, MIG, Eotaxin, RANTES, and MCP-1, and neuropeptides) using high-resolution multiplex bead immunoassays and enzyme-linked immunosorbent assay (ELISA). Additionally, polyacrylamide gel electrophoresis was carried out to verify the presence of serum proteins.

RESULTS

Despite the presence of amino acids/serum proteins in the epidural lavage fluid, none of the aforementioned mediators were isolated in a quantifiable concentration using the ELISA techniques with >5 pg/mL resolution.

DISCUSSION

The current proteomics array technology was not able to detect critical levels of biochemical markers present in the epidural space through the mentioned lavage technique. This lack of detection could be due to the absence of the factors in this environment or the inability of the technique to obtain or detect factors which may be present.

CONCLUSION

Although a novel approach, the current study was unable to identify the presence of a series of inflammatory peptides in the epidural lavage of patients with symptomatic radicular pain due to herniated disc disease. We recommend alternative experimental designs than the one we pursued for definitively identifying potential sources of pain generators.

Omega-3 fatty acids (fish oil) as an anti-inflammatory: an alternative to nonsteroidal anti-inflammatory drugs for discogenic pain

BACKGROUND

The use of NSAID medications is a well-established effective therapy for both acute and chronic nonspecific neck and back pain. Extreme complications, including gastric ulcers, bleeding, myocardial infarction, and even deaths, are associated with their use. An alternative treatment with fewer side effects that also reduces the inflammatory response and thereby reduces pain is believed to be omega-3 EFAs found in fish oil. We report our experience in a neurosurgical practice using fish oil supplements for pain relief.

METHODS

From March to June 2004, 250 patients who had been seen by a neurosurgeon and were found to have nonsurgical neck or back pain were asked to take a total of 1200 mg per day of omega-3 EFAs (eicosapentaenoic acid and decosahexaenoic acid) found in fish oil supplements. A questionnaire was sent approximately 1 month after starting the supplement.

RESULTS

Of the 250 patients, 125 returned the questionnaire at an average of 75 days on fish oil. Seventy-eight percent were taking 1200 mg and 22% were taking 2400 mg of EFAs. Fifty-nine percent discontinued to take their prescription NSAID medications for pain. Sixty percent stated that their overall pain was improved, and 60% stated that their joint pain had improved. Eighty percent stated they were satisfied with their improvement, and 88% stated they would continue to take the fish oil. There were no significant side effects reported.

CONCLUSIONS

Our results mirror other controlled studies that compared ibuprofen and omega-3 EFAs demonstrating equivalent effect in reducing arthritic pain. omega-3 EFA fish oil supplements appear to be a safer alternative to NSAIDs for treatment of nonsurgical neck or back pain in this selective group.

Mechanobiology of the intervertebral disc and relevance to disc degeneration

Mechanical loading of the intervertebral disc may contribute to disc degeneration by initiating degeneration or by regulating cell-mediated remodeling events that occur in response to the mechanical stimuli of daily activity. This article is a review of the current knowledge of the role of mechanical stimuli in regulating intervertebral disc cellular responses to loading and the cellular changes that occur with degeneration. Intervertebral disc cells exhibit diverse biologic responses to mechanical stimuli, depending on the loading type, magnitude, duration, and anatomic zone of cell origin. The innermost cells respond to low-to-moderate magnitudes of static compression, osmotic pressure, or hydrostatic pressure with increases in anabolic cell responses. Higher magnitudes of loading may give rise to catabolic responses marked by elevated protease gene or protein expression or activity. The key regulators of these mechanobiologic responses for intervertebral disc cells will be the micromechanical stimuli experienced at the cellular level, which are predicted to differ from that measured for the extracellular matrix. Large hydrostatic pressures, but little volume change, are predicted to occur for cells of the nucleus pulposus during compression, while the highly oriented cells of the anulus fibrosus may experience deformations in tension or compression during matrix deformations. In general, the pattern of biologic response to applied loads suggests that the cells of the nucleus pulposus and inner portion of the anulus fibrosus experience comparable micromechanical stimuli in situ and may respond more similarly than cells of the outer portion of the anulus fibrosus. Changes in these features with degeneration are critically understudied, particularly degeneration-associated changes in cell-level mechanical stimuli and the associated mechanobiology. Little is known of the mechanisms that regulate cellular responses to intervertebral mechanobiology, nor is much known with regard to the precise mechanical stimuli experienced by cells during loading. Mechanical factors appear to regulate responses of the intervertebral disc cells through mechanisms involving intracellular Ca(2+) transients and cytoskeletal remodeling that may regulate downstream effects such as gene expression and posttranslational biosynthesis. Future studies should address the broader biologic responses to mechanical stimuli in intervertebral disc mechanobiology, the involved signaling mechanisms, and the apparently important interactions among mechanical factors, genetic factors, cytokines, and inflammatory mediators that may be critical in the regulation of intervertebral disc degeneration.

Gene expression changes in an early stage of intervertebral disc degeneration induced by passive cigarette smoking

STUDY DESIGN

This study attempts to determine the molecular changes in intervertebral disc degeneration of rats induced by passive cigarette smoking.

OBJECTIVES

To quantitate and compare the gene expression levels in intervertebral discs from passively cigarette smoking rats and nonsmoking rats.

SUMMARY OF BACKGROUND DATA

The molecular mechanism of intervertebral disc degeneration has been investigated mainly in vitro but little in vivo, and gene expression analysis has been performed in a few studies. The cigarette smoking is a risk factor of low back pain. We developed a smoking box to create a rat model of intervertebral disc degeneration induced by passive cigarette smoking.

METHODS

Total RNA was extracted from intervertebral discs of rats that were raised in a cigarette-smoking box for 2 to 7 weeks. After synthesis of cDNA, the quantitative analysis of gene expression was performed by the real-time PCR. The remaining spines were subjected to the histologic examination.

RESULTS

Histologic changes of the nucleus pulposus and the anulus fibrosus were detected after 2 weeks of smoking and were frequently found after 7 weeks. Collagen genes were downregulated remarkably after 7 weeks of smoking. No significant increase was observed in the expressions of matrix metalloproteinase-3, but the expression of tissue inhibitor of metalloproteinases-1 started to increase at 4 weeks of smoking. Aggrecan also started to be up-regulated at 4 weeks.

CONCLUSIONS

Changes in gene expression by passive cigarette smoking precede the histologic changes in the intervertebral discs. Reactions to suppress the destruction of tissue matrix and to regenerate the intervertebral discs are occurring at the same time as the degenerative histologic changes.

Histological changes in intervertebral discs after smoking and cessation: experimental study using a rat passive smoking model

BACKGROUND

Passive smoking has been reported to induce intervertebral disc degeneration in rats, and the objective of the present study was to histologically investigate changes in smoking-induced intervertebral disc degeneration after cessation of smoking.

METHODS

Four-week-old rats were subjected to passive smoking for 8 weeks in a smoking box [20 cigarettes a day: one cigarette an hour (inhaled over 3 minutes and followed by ventilation with room air for 5 minutes)] to induce intervertebral disc degeneration. Smoke-free periods of different lengths were then established, and intervertebral discs were histologically analyzed.

RESULTS

Immediately after 8 weeks of passive smoking, intervertebral discs exhibited cracks, tears, and misalignment of the annulus fibrosus, and increased fibrous tissue was seen in the nucleus pulposus. In addition, the level of interleukin-1beta in intervertebral discs was higher in the smoking group than in the non-smoking group. After cessation, progression of degeneration ceased, and the matrix of the nucleus pulposus and annulus fibrosus exhibited increased fibrous connective tissue and proteoglycan. However, there were no changes in annulus fibrosus misalignment. Interleukin-1beta levels also remained significantly elevated after 8 weeks of cessation.

CONCLUSIONS

While the annulus fibrosus degeneration caused by smoking was partially irreversible after cessation of smoking, the amount of mucin (proteoglycan) in the nucleus pulposus and annulus fibrosus tended to increase after cessation, thus suggesting the possibility that smoking-induced intervertebral disc degeneration can be repaired to some degree by cessation of smoking.

Nonspondylolytic Etiologies of Lumbar Pain in the Young Athlete

Approximately 50% of adolescent athletes with persistent lumbar pain can be diagnosed with spondylolysis or spondylolisthesis. The remaining 50% will have suffered injury of the vertebral body, intervertebral disc, ring apophysis, pelvis, articular processes, spinous processes, interspinous ligament, or other soft tissues of the lumbar spine. The adolescent spine is prone to these injuries as a consequence of the growth spurt and skeletal immaturity. Accurate diagnosis is mandatory in order to achieve successful treatment. History, physical examination, imaging modalities, and precision spinal injections can be employed to accurately diagnose the source of the symptoms. Appropriate treatment measures can then be prescribed to optimally treat the adolescent spine injury.

The potential of chitosan-based gels containing intervertebral disc cells for nucleus pulposus supplementation

The suitability of chitosan-based hydrogels as scaffolds for the encapsulation of intervertebral disc (IVD) cells and the accumulation of a functional extracellular matrix mimicking that of the nucleus pulposus (NP) was investigated. The specific hypothesis under study was that the cationic chitosan would form an ideal environment in which large quantities of newly synthesized anionic proteoglycan could be entrapped. Indeed, all the formulations of cell-seeded chitosan hydrogels, studied under in vitro culture conditions, showed that the majority of proteoglycan produced by encapsulated NP cells was retained within the gel rather than released into the culture medium. This was not always the case when annulus fibrosus cells were encapsulated, as unlike the nucleus cells the annulus cells often did not survive when cultured in chitosan. The results support the concept that chitosan may be a suitable scaffold for cell-based supplementation to help restore the function of the NP during the early stages of IVD degeneration.

Effects of cyclic mechanical stress on the production of inflammatory agents by nucleus pulposus and anulus fibrosus derived cells in vitro

STUDY DESIGN

Cyclic mechanical stress (CMS) was applied to cultured nucleus pulposus and anulus fibrosus cells, and the production of inflammatory agents by these cells was evaluated.

OBJECTIVE

To investigate the involvement of CMS in the production of inflammatory agents by disc cells.

SUMMARY OF BACKGROUND DATA

It has been reported that CMS affects degeneration of the disc. However, little is known about the effect of CMS on the production of inflammatory agents by both cell types in vitro.

METHODS

Cells derived from nucleus pulposus and anulus fibrosus of Sprague-Dawley rat tails were cultured with or without CMS applied by the Flexercell Strain Unit (Flexcell International Corp., Hillsborough, NC) in the presence or absence of inflammatory stimulus. Doses of prostaglandin-E2 (PGE2) were measured in the culture supernatants. Semiquantitative evaluations of the expressions of cyclooxygenase (COX)-2 and phospholipase-A2 IIA messenger ribonucleic acids (mRNAs) were also examined.

RESULTS

Sole application of CMS on nucleus pulposus and anulus fibrosus cells increased PGE2 synthesis. Coincidence of CMS and inflammatory stimulus synergistically enhanced PGE2 synthesis of both cell types. Anulus fibrosus cells showed a stronger reactivity to these stimuli than nucleus pulposus cells. The expression of COX-2 mRNA of anulus fibrosus cells tended to correlate to the amount of PGE2, whereas COX-2 mRNA was constitutively expressed in nucleus pulposus cells, suggesting that the roles of COX-2 might be different between nucleus pulposus and anulus fibrosus. Phospholipase-A2 IIA mRNA was constitutively expressed in both cell types.

CONCLUSIONS

The results of this study suggested that CMS might be involved in the pathomechanism of pain induction of lumbar disc diseases.

De novo osteogenesis from human ligamentum flavum by adenovirus-mediated bone morphogenetic protein-2 gene transfer

STUDY DESIGN

In vitro and in vivo experiment using degenerated human ligamentum flavum (LF) and Type 5 adenovirus construct with bone morphogenetic protein-2 (BMP-2) cDNA.

OBJECTIVES

To demonstrate in vitro and in vivo osteogenic effect of BMP-2 gene transfer to human LF and to propose genetically modified LF as a substitute for autogenous bone graft in spinal fusion.

SUMMARY OF BACKGROUND DATA

Spinal fusion is still considered to be an important option for treating various spinal disorders. To induce solid spinal fusion, osteoinductive and/or osteoconductive agents have been widely adopted. Autogenous LF, however, has never been seriously considered as a carrier for ex vivo osteoinductive gene therapy for spinal fusion.

METHODS

In vitro experiment: Degenerated human LF was harvested and cultured. Type 5 adenovirus lacZ (Ad/lacZ) and BMP-2 construct (Ad/BMP-2) were produced. LF cell cultures were then exposed to Ad/BMP-2. Expressions of osteocalcin and BMP-2 mRNA were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis was performed to detect osteocalcin protein. Alkaline phosphatase and von Kossa stains were used to detect osteogenic markers and bone nodule formation, respectively. In vivo experiment: Human LF tissues treated with Ad/lacZ, Ad/BMP-2, and saline were implanted into the subcutaneous tissue of nude mice. After 4 weeks, nude mice were radiographed and killed. Implanted LF tissues were harvested and histologically stained.

RESULTS

LF cell cultures with Ad/BMP-2 revealed strong expression of BMP-2 and osteocalcin mRNA in RT-PCR and osteocalcin protein in western blot analysis. LF cell culture with saline showed baseline expression of BMP-2, osteocalcin mRNA, and osteocalcin protein, respectively. Furthermore, LF cell culture with Ad/BMP-2 demonstrated the expression of alkaline phosphatase and bone nodule formation in the aforementioned histochemical stain. LF tissues with Ad/BMP-2 revealed de novo osteogenesis in nude mice, whereas LF with Ad/lacZ or saline showed only remaining LF tissue without sign of bone formation.

CONCLUSION

Human LF cells transduced with Ad/BMP-2 exhibited the expression of osteogenic phenotype and bone nodule formation. Additionally, genetically modified human LF with BMP-2 cDNA clearly demonstrated de novo osteogenesis, which supports the concept that biologically modified LF can be a substitute for autogenous bone graft in spinal fusion surgery.

Tumor necrosis factor-alpha modulates matrix production and catabolism in nucleus pulposus tissue

STUDY DESIGN

This study examines changes in the production of extracellular matrix molecules as well as the induction of tissue degradation in in vitro formed nucleus pulposus (NP) tissues following incubation with tumor necrosis factor (TNF)alpha.

OBJECTIVE

To characterize the response of NP cells to TNF-alpha, a proinflammatory cytokine present in herniated NP tissues.

SUMMARY OF BACKGROUND DATA

TNF-alpha is a proinflammatory cytokine expressed by NP cells of degenerate intervertebral discs. It is implicated in the pain associated with disc herniation, although its role in intervertebral disc degeneration remains poorly understood.

METHODS

In vitro formed NP tissues were treated with TNF-alpha (up to 50 ng/mL) over 48 hours. Tissues were assessed for histologic appearance, proteoglycan and collagen contents, as well as proteoglycan and collagen synthesis. Reverse transcriptase polymerase chain reaction was used to determine the effect of TNF-alpha on NP cell gene expression. Proteoglycan degradation was assessed by immunoblot analysis.

RESULTS

At doses of 1-5 ng/mL, TNF-alpha induced multiple cellular responses, including: decreased expression of both aggrecan and type II collagen genes; decreases in the accumulation and overall synthesis of aggrecan and collagen; increased expression of MMP-1, MMP-3, MMP-13, ADAM-TS4, and ADAM-TS5; and induction of ADAM-TS dependent proteoglycan degradation. Within 48 hours, these cellular responses resulted in NP tissue with only 25% of its original proteoglycan content.

CONCLUSIONS

Because low levels of TNF-alpha, comparable to those present physiologically, induced NP tissue degradation, this suggests that TNF-alpha may contribute to the degenerative changes that occur in disc disease.

Osteogenic protein-1 (osteogenic protein-1/bone morphogenetic protein-7) inhibits degeneration and pain-related behavior induced by chronically compressed nucleus pulposus in the rat

STUDY DESIGN

To study the therapeutic efficacy of intradiscal injection of osteogenic protein-1 (OP-1) to reduce degeneration and associated discogenic pain.

OBJECTIVE

To evaluate if intradiscal injection of OP-1 can reverse disc degeneration and reduce hyperalgesia, a pain-related behavior.

SUMMARY OF BACKGROUND DATA

We showed that induction of hyperalgesia was higher in rats exposed to compressed nucleus pulposus (NP). It has been reported that intradiscal injection of OP-1 stimulates synthesis of proteoglycans and collagen in normal intervertebral discs.

METHODS

Rats were divided into several groups. In the sham group, the rings of an Ilizarov-type apparatus were only applied to the tail without compression. In the compressed NP group, the apparatus was used to apply chronically compression to the tail. Four weeks after surgery, the NP group was subdivided into 3 groups: saline-treated and OP-1-treated, which was divided into 2 groups (i.e., the continuous compression OP-1 [COP-1] group, in which compression was continuously applied to the tail for 4 weeks after OP-1 treatment and the release compression OP-1 [ROP-1] group, in which compression was released at treatment. Either physiologic saline or OP-1 was injected into the instrumented NP. The treated NP was harvested and applied to the left lumbar nerve roots 4 weeks after injection. Hyperalgesia was measured up to 3 weeks after surgery. The degree of disc degeneration and the appearance of the extracellular matrix in the intervertebral discs were evaluated by histology.

RESULTS

Mechanical hyperalgesia was observed in the sham and saline groups, but not in the OP-1 treated group. In the saline group, NP cells became spindle-shaped. In the OP-1 group, the NP cells became swollen with vacuolated cytoplasm, and the content of the extracellular matrix was markedly increased.

CONCLUSION

OP-1 injection into degenerative intervertebral disc resulted in the enhancement of the extracellular matrix and the inhibition of pain-related behavior.

The potential value of blood biomarkers of intervertebral disk metabolism in the follow-up of patients with sciatica

STUDY DESIGN

This is a prospective study with a follow-up period of 4 years.

OBJECTIVES

The study aimed to evaluate the possible clinical utility of three biomarkers [i.e., keratan sulfate (KS), hyaluronan, and cartilage oligomeric matrix protein] measured in peripheral blood in severe acute sciatica at intake and follow-up.

SUMMARY OF BACKGROUND

Our previous study and others have pointed out the interest of different laboratory tests in the acute phase of sciatica. Several blood biomarkers have been reported useful in the long-term follow-up of patients with osteoarthritis. We have found no information about the potential interest of these tests in spinal disorders.

METHODS

Patients were admitted to the hospital for intensive conservative management of acute sciatica (n=82). A subgroup of patients (n=33) was selected based on the duration of symptoms at visit 1, and included those with the shortest (n=24) as well as those with the longest (n=9) duration of sciatica. Blood samples were drawn, centrifuged, and the plasma frozen. Antigenic KS, hyaluronan, and cartilage oligomeric matrix protein were measured by ELISA. Patients were re-evaluated at an average of 4.3 years (range: 2.1-6.8 years).

RESULTS

Thirty-three subjects with an average age of 49.2+/-10.2 years participated. At intake, levels of the three biomarkers evaluated were within the range of normal values. No significant differences were found between the results of patients with a short history of sciatica (< or =3 weeks) and those with a long duration of symptoms (>20 weeks). At follow-up, a significant increase (P<0.05) in all three biomarkers was found.

CONCLUSIONS

A single measurement of these three biomarker molecules does not seem to have any diagnostic or therapeutic relevance in patients with acute radicular compression. The significance of the increase in all three biomarkers after a mean follow-up of 4.3 years is unclear; it might reflect metabolic processes involved in degenerative spinal disorders. Even though we found no correlation with clinical outcome, we believe that more research is needed.

Positive feedback loop of interleukin-1beta upregulating production of inflammatory mediators in human intervertebral disc cells in vitro

OBJECT

Interleukin-1beta (IL-1beta) induces neurological symptoms in intervertebral disc herniation (IDH). Recently, the existence of a positive feedback loop of IL-1beta, which encourages an inflammatory reaction or degeneration in the cells of tendon, has been reported. The authors hypothesized that there is a positive feedback loop of IL-1beta in the cells of IDH.

METHODS

Eight human intervertebral disc specimens were harvested during spinal surgery for lumbar disc herniation. The cells were stimulated in serum-free medium with or without exogenous IL-1beta. The messenger RNA (mRNA) was extracted for reverse-transcription polymerase chain reaction (PCR) and real-time PCR to quantify the mRNA of endogenous IL-1beta, IL-6, cyclooxygenase-2 (COX-2), and matrix metalloproteinases (MMPs). The cells were then stimulated in serum-free medium with or without exogenous IL-1beta, and then exogenous IL-1beta was removed. After 2, 4, and 6 days, the medium was collected, and enzyme-linked immunosorbent assay was used to measure the protein concentration of endogenous IL-1beta. The mRNA expressions of endogenous IL-1beta, IL-6, COX-2, and MMPs were increased significantly depending on the concentration of exogenous IL-1beta. The protein concentration of endogenous IL-1beta was increased over time.

CONCLUSIONS

There was a positive feedback loop of IL-1beta in the cells of IDH. Furthermore, the productions of IL-6, COX-2, MMP-1, and MMP-3 were upregulated as a result of the increasing concentration of IL-1beta in a positive feedback loop of IL-1beta. The authors concluded that this positive feedback loop of IL-1beta upregulated the production of mediators and thus can cause cessation of symptoms in IDH.

Characterization of intervertebral disc degeneration by high-resolution magic angle spinning (HR-MAS) spectroscopy

The goal of this study was to determine the ability of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to distinguish different stages of intervertebral disc degeneration (IVDD). 17 discs were removed from human cadavers and analyzed them using 1D and 2D (total correlation spectroscopy (TOCSY)) (1)H HR-MAS spectroscopy, and T(1) and T(2) relaxation time measurements to determine the chemical composition and changes in chemical environment of discs with increasing levels of degeneration (Thompson grade). Among the significant findings were that spectra were very similar for samples taken from annular and nuclear regions of discs, and that visually apparent changes were observed in the spectra of the annular and nuclear samples from discs with increasing Thompson grade. Area ratios of the N-acetyl to choline (Cho) regions, and Cho to carbohydrate (Carb) regions of the spectra allowed us to discriminate between discs of increasing Thompson grade with minimal overlap of individual ratios. Changes in T(1) and T(2) relaxation times of the chemical constituents of disc spectra were not significantly correlated to the degree of degeneration. The results of this study support the feasibility of using in vivo spectroscopy for detecting chemical changes associated with disc degeneration.

Cervical intervertebral disc injury during simulated frontal impact

Cervical disc injury due to frontal impact has been observed in both clinical and biomechanical investigations; however, there is a lack of data that elucidate the mechanisms of disc injury during these collisions. The goals of the current study were to determine the peak dynamic disc annular tissue strain and disc shear strain during simulated frontal impact of the whole human cervical spine model with muscle force replication at 4 g, 6 g, 8 g and 10 g horizontal accelerations of the T1 vertebra. These data were compared with those obtained during physiological loading, and with previously reported rear impact data. Peak disc shear strain and peak annular tissue strain during frontal impact exceeded (p<0.05) corresponding physiological limits at the C2-C3 intervertebral level, beginning at 4 g and 6 g, respectively. These subsequently spread throughout the entire cervical spine at 10 g, with the exception of C4-C5. The C5-C6 intervertebral level was at high risk for injury during both frontal and rear impacts, while during frontal impact, in addition to C5-C6, subfailure injuries were likely at superior intervertebral levels, including C2-C3. The disc injuries occurred at lower impact accelerations during rear impact as compared with frontal impact. The subfailure injuries of the cervical intervertebral disc that occur during frontal impact may lead to the chronic symptoms reported by patients, such as head and neck pain.

The adeno associated viral vector as a strategy for intradiscal gene transfer in immune competent and pre-exposed rabbits

STUDY DESIGN

Experimental animal study.

OBJECTIVES

This study evaluates the in vitro and in vivo transduction efficacy and transgene expression in immune competent and pre-exposed rabbits.

SUMMARY OF BACKGROUND DATA

Degenerative disc disease (DDD) continues to pose a substantial clinical problem. Therapeutic options such as an interbody fusion are highly invasive and result in the loss of the intervertebral disc. In addition, interbody fusion puts the adjacent discs at an even higher risk for disc degeneration. A novel approach to slow DDD is to introduce high levels of growth factors into the degenerating disc by delivering the gene coding for the appropriate growth factor. The most efficient technique to do so to date uses viral vectors. However, viral vectors may be problematic because of their immunogenicity. The adeno-associated virus (AAV) viral vector is known to be less immunogenic than commonly used adenoviral vectors.

METHODS

Human nucleus pulposus cells were transduced in vitro. Twenty-four Rabbits were injected with AAV viral vectors carrying different marker genes. Transgene expression and the humoral/cellular immune response to the vector was evaluated.

RESULTS

We could show that the AAV viral vector transduces human as well as rabbit nucleus pulposus cells in vitro and in vivo. There is a significant humoral immune response against the AAV vector that decreases transgene expression over 10-fold in preimmunized animals.

CONCLUSIONS

AAV is a valuable new vector to achieve transgene expression in the intervertebral disc. In preimmunized animals, its use needs to be further evaluated because of the significant reduction in transgene expression.

Predicting the failure of disc surgery by a hypofunctional HPA axis: evidence from a prospective study on patients undergoing disc surgery

Patients with postoperative ongoing sciatic pain have been shown to exhibit reduced cortisol levels along with enhanced IL-6 levels. The aim of the present study was to clarify the relationship between a reduced cortisol secretion and enhanced cytokine levels by performing a prospective study on patients with disc herniation. Twenty-two patients were examined before and after their disc surgery. Twelve healthy, pain-free subjects matched for age, education and gender constituted the control group. The preoperative examinations included the assessment of the diurnal pattern of cortisol secretion and the feedback sensitivity of the hypothalamus-pituitary-adrenal (HPA) axis. Patients' subjective stress levels also were assessed during the preoperative examination. The diurnal pattern of cortisol secretion was again assessed during the postoperative examination. Furthermore, blood samples were collected to measure catecholamine, adrenocorticotropic hormone (ACTH)- and interleukin-6 (IL-6) levels before and after measuring the pressure pain thresholds (PPTs). An assessment of the sensitivity of circulating monocytes to the immunosuppressive effects of glucocorticoids was further included in the postoperative examinations. Failed back syndrome (FBS) patients (n=12) showed a reduced cortisol secretion in the morning hours and enhanced feedback sensitivity of the HPA axis. Furthermore, FBS patients displayed an increased in-vitro production of proinflammatory cytokines and a relative glucocorticoid resistance of pro-inflammatory cytokine producing monocytes as compared to non-FBS patients (n=10) and controls. After PPT measurement FBS patients exhibited an increased norepinephrine but decreased epinephrine response, together with lower ACTH levels and a four times higher plasma IL-6 response. These findings suggest that chronically stressed patients are at a higher risk for a poor surgical outcome as their reduced cortisol secretion promotes the postoperative ongoing synthesis of proinflammatory cytokines.

Cytokine profiles in conditioned media from cultured human intervertebral disc tissue. Implications of their effect on bone marrow stem cell metabolism

BACKGROUND

Cytokines released from intervertebral discs cultured in vitro have not been profiled, and the effect of these cytokines on human bone marrow stem cells is yet to be studied.

MATERIALS AND METHODS

Intervertebral discs from 14 patients who had undergone spinal fusion surgery were cultured separately in vitro. Conditioned media were collected after 48 and 96 h of culture in serum-free Minimum Essential Medium (MEM). Profiling of the cytokines was conducted using pooled media. Conditioned medium from each patient was also tested in human bone marrow stem cell culture, and incorporation of alkaline phosphatase and 3H-thymidine incorporation was evaluated.

RESULTS

Of the 18 cytokines screened, 12 were found to be positive, but only eotaxin, IP-10, Rantes IL-6 and IL-8 seemed to be present at high levels. There was a close correlation between IL-6 and IL-8 levels in the medium (R = 0.90, p < 0.001). When the conditioned media were added to human bone marrow stem cell cultures, cellular proliferation was stimulated (p = 0.02), but alkaline phosphatase activity remained unchanged. Cellular proliferation correlated negatively with IL-6 levels (R = -0.44, p = 0.04).

INTERPRETATION

Intervertebral discs secrete certain cytokines into the medium when cultured in vitro, and conditioned media from cultured intervertebral discs stimulate proliferation of bone marrow stem cells.

A longitudinal study on an autoimmune murine model of ankylosing spondylitis

BACKGROUND

Proteoglycan aggrecan (PG)-induced arthritis (PGIA) is the only systemic autoimmune murine model which affects the axial skeleton, but no studies have been performed characterising the progression of spine involvement.

OBJECTIVES

To follow pathological events in experimental spondylitis, and underline its clinical, radiographic, and histological similarities to human ankylosing spondylitis (AS); and to determine whether the spondyloarthropathy is a shared phenomenon with PGIA, or an "independent" disease.

METHODS

Arthritis/spondylitis susceptible BALB/c and resistant DBA/2 mice, and their F1 and F2 hybrids were immunised with cartilage PG, and radiographic and histological studies were performed before onset and weekly during the progression of spondylitis.

RESULTS

About 70% of the PG immunised BALB/c mice develop spondyloarthropathy (proteoglycan-induced spondylitis (PGISp), and the progression of the disease is very similar to human AS. It begins with inflammation in the sacroiliac joints and with enthesitis, and then progresses upwards, affecting multiple intervertebral disks. In F2 hybrids of arthritis/spondylitis susceptible BALB/c and resistant DBA/2 mice the incidence of arthritis was 43.5%, whereas the incidence of spondylitis was >60%. Some arthritic F2 hybrid mice had no spondylitis, whereas others developed spondylitis in the absence of peripheral arthritis.

CONCLUSIONS

The PGISp model provides a valuable tool for studying autoimmune reactions in spondylitis, and identifying genetic loci associated with spondyloarthropathy.

Intervertebral disc cells produce tumor necrosis factor alpha, interleukin-1beta, and monocyte chemoattractant protein-1 immediately after herniation: an experimental study using a new hernia model

STUDY DESIGN

A new hernia model that simulates human disc herniations was developed in rabbits. The herniated discs were examined by gross appearance and histology and production of tumor necrosis factor alpha, interleukin-1beta, and monocyte chemoattractant protein-1 was investigated.

OBJECTIVES

To clarify the early mechanism of spontaneous herniated disc resorption.

SUMMARY OF BACKGROUND DATA

Macrophage infiltration in herniated discs is essential for disc resorption. However, surgically removed human herniated disc tissues and existing animal hernia models are not suitable for analyzing the mechanism of macrophage infiltration. Recently, we have demonstrated that intervertebral disc cells are capable of producing monocyte chemoattractant protein-1, a potent macrophage chemoattractant, after stimulation with tumor necrosis factor alpha and interleukin-1beta.

METHODS

Intervertebral disc herniations were surgically developed in rabbits using a new technique. The herniated discs were excised at appropriate time intervals after the surgery, and the size and histologic findings were examined. Expressions of tumor necrosis factor alpha, interleukin-1beta, and monocyte chemoattractant protein-1 in herniated discs were investigated immunohistochemically.

RESULTS

A new rabbit model of disc herniation was established. The herniated discs spontaneously reduced in size by 12 weeks postsurgery. Infiltrating cells, mainly composed of macrophages, were observed from day 3. Immunohistochemically, intervertebral disc cells in the herniated discs produced tumor necrosis factor alpha and interleukin-1beta on day 1, followed by monocyte chemoattractant protein-1 on day 3.

CONCLUSIONS

The new hernia model appears to be very useful for studying herniated disc resorption. Intervertebral disc cells may produce inflammatory cytokines/chemokine immediately after the onset of disc herniation, possibly triggering subsequent macrophage infiltration that leads to disc resorption.

Quantitative analysis of gene expression in a rabbit model of intervertebral disc degeneration by real-time polymerase chain reaction

BACKGROUND CONTEXT

Serial analysis of gene expression during the course of intervertebral disc degeneration (IDD) could elucidate valuable insight into pathophysiology and provide a basis for identification of potential targets for the development of novel cellular- and gene-based therapies. However, very few previous studies described the changes in gene expression through the process of IDD using a suitable animal model.

PURPOSE

To use a recently developed rabbit annular stab model and the technique of real-time reverse transcriptase-polymerase chain reaction (RT-PCR) to quantify the change in expression of key rabbit-specific mRNA sequences encoding for selected extracellular matrix (ECM) products, catabolic, anabolic, and anti-catabolic factors in normal and stabbed discs.

STUDY DESIGN

Gene expression analyses were performed to characterize a slowly progressive and reproducible animal model of IDD using real-time RT-PCR.

METHODS

Twelve rabbits underwent an annular stab with a 16-gauge needle to the L2-L3, L3-L4, and L4-L5 discs, and three rabbits served as sham controls. Nucleus pulposus tissues were harvested from the stabbed discs at 3, 6, 12 and 24 weeks after confirmation of degenerative changes by magnetic resonance imaging (MRI) scan. Real-time RT-PCR was performed with the use of rabbit-specific primers for 1) extracellular matrix (ECM) component genes: collagen type Ia and IIa, and aggrecan; 2) catabolic genes: matrix metalloprotease-3 (MMP-3), inducible nitric oxide synthase (iNOS), and interleukin-1beta (IL-1beta); 3) anabolic growth genes: bone morphogenic protein-2, and -7 (BMP-2, -7), transforming growth factor-beta1 (TGF-beta1), and insulin-like growth factor-1 (IGF-1); and 4) anti-catabolic gene: tissue inhibitor of metalloprotease-1 (TIMP-1). These data were normalized to mRNA levels of glyceraldehyde phosphate dehydrogenase (GAPDH), a constitutively expressed gene.

RESULTS

The MRI images confirmed progressive decline in the nucleus pulposus area of high T2 signal and in the signal intensity of the stabbed discs over the 24-week study period consistent with IDD. The ECM components, aggrecan and collagen type IIa mRNA levels had decreased markedly by week 3 and never recovered, whereas type Ia collagen mRNA gradually increased throughout course of degeneration. BMP-2, BMP-7 and IGF-1 mRNA were relatively decreased from weeks 3 to 6 but then increased at weeks 12 and 24 to end at a level near the preoperative level. The TIMP-1 expression fell dramatically to approximately one tenth of the preoperative level by week 3 and remained low throughout the degenerative process. The remaining results, including those from TGF-beta1 and the catabolic genes (MMP-3, IL-1beta, iNOS) demonstrated a double peak characteristic. The gene expression increased by week 3, decreased to a low level at weeks 6 and 12 and then had a second, late peak at 24 weeks.

CONCLUSIONS

The gene expression profiles of ECM components and anabolic, catabolic, and anti-catabolic factors demonstrate many characteristics similar to the findings in human disc degeneration and suggest an inability of the intervertebral disc (IVD) to mount an early anabolic response to injury, thereby offering a possible explanation for the disc's lack of reparative capabilities. Catabolic genes are strongly up-regulated both early and late in degeneration, lending strong support to the hypothesis that an anabolic or catabolic imbalance plays a primary role in IDD. According to the resultant patterns, augmenting early production of BMP-2, BMP-7, IGF-1 or TIMP-1 by gene transfer techniques might possibly alter the progressive course of degeneration as seen in the stab model. The next step will be to transfer these therapeutic genes to regulate the biologic processes and ideally alter the progressive course of disc degeneration.

Cell mechanics and mechanobiology in the intervertebral disc

STUDY DESIGN

A review is presented on current knowledge of the micromechanical factors in the intervertebral disc, their role in modifying cell biology, and changes with degeneration.

OBJECTIVES

To identify current knowledge, knowledge gaps, and areas for future research in micromechanics of the intervertebral disc.

SUMMARY OF BACKGROUND DATA

Mechanical factors play important roles in the initiation and progression of intervertebral disc degeneration. Evidence suggests that substantial biologic remodeling occurs in the intervertebral disc in response to mechanical stimuli that may play a critical role in determining the fate of a degenerating intervertebral disc. Information is needed on the precise mechanical stimuli that these cells experience and the mechanisms that govern their responses.

METHODS

A review is presented of cell morphology, cell mechanics, and the internal strains and other mechanical factors predicted to occur at the cell level. A review of intervertebral disc cell responses to well-controlled physical stimuli is also presented with a focus on in vitro studies of explants and isolated cells.

RESULTS

Important differences in cell morphology, mechanics, micromechanical factors, and mechanobiology are noted to occur between cells of the nucleus pulposus and anulus fibrosus. Changes in these features with degeneration are critically understudied, particularly degeneration-associated changes in cell morphology, cell mechanics, and altered physiology with mechanical loading.

CONCLUSIONS

Information on the mechanisms that govern cell responses to mechanical stimuli in the intervertebral disc are just emerging. Studies must address determination of the factors that control micromechanical stimuli, but also mechanisms by which mechanics may interact with genetic factors to regulate expression and remodeling of extracellular matrix molecules, cytokines and mediators of pain and inflammation in degenerating tissue.

Growth factors and treatment of intervertebral disc degeneration

STUDY DESIGN

Literature review.

OBJECTIVE

To review the most recent findings of the effects of growth factors on the intervertebral disc and, further, to discuss trends in the biologic repair of the degenerated intervertebral disc.

SUMMARY OF BACKGROUND DATA

Since early in 1990, advancements in molecular biology and cell culture technology have enabled researchers to accumulate knowledge about the in vitro actions of growth factors on intervertebral disc cells. More recently, the use of growth factors for the biologic regeneration of the intervertebral disc is of increasing interest to the orthopedic field, and indeed, some preliminary in vivo studies have proven their efficacy.

METHODS

Based on a literature search conducted using available databases, such as the National Library of Medicine, as well as data presented at scientific conferences held in the past 2 years, primarily in the United States, the current status of biologic therapy for disc degeneration using growth factors was summarized.

RESULTS

With increasing evidence to support the feasibility of biologically regenerating intervertebral disc tissues, the clinical application of growth factors has become more plausible. The effects of growth factors on the metabolism of intervertebral disc cells or tissues have been extensively studied using in vitro approaches. More recently, the efficacy of an injection of growth factor protein to reverse disc regeneration has been shown in vivo using a small animal disc degeneration model. The confirmation of those effects and a detailed dose-response study, as well as a long-term safety study, in a large animal model is highly anticipated. Hopefully, the expansion of the clinical use of improved imaging techniques for the early detection of disc degeneration and promising results about the effects of growth factors on intervertebral disc regeneration will benefit the human population in the near future.

CONCLUSIONS

The results from these in vitro and in vivo studies reviewed here clearly suggest the potential usefulness of growth factor injections as a new approach to restore intervertebral disc degeneration at an early stage.

Imaging of disk disease and degenerative spondylosis of the lumbar spine

Low back pain is a common but poorly understood entity. Features of degeneration depend on which component of the motion segment is predominantly affected, and include disk space narrowing, vacuum phenomenon, disk desiccation, vertebral osteophyte formation, disk herniation, and facet arthrosis, but these features do not necessarily have any relationship to symptoms. Since most episodes of back pain resolve on their own, and most disk herniations spontaneously regress, imaging of low back pain, although widely performed, is probably not necessary in most cases.

Infiltration foraminale L5-S1 radioguidée dans le traitement de la lombosciatique S1

OBJECTIVE

To assess the efficacy of fluoroscopy guided L5-S1 transforaminal steroid injections for the treatment of S1 radiculopathy secondary to intervertebral disk disorder.

METHOD

41 patients were included: prospective study (20 patients) and retrospective study (21 patients). All patients suffered from S1 radiculopathy secondary to nerve root compression by intervertebral disk material, as demonstrated by lumbar spine CT. The patients underwent 2 fluoroscopy guided L5-S1 transforaminal injections of steroid (Hydrocotancyl 125 mg), at 8 days interval.

RESULTS

60% of patients showed significant improvement of their painful radiculopathy at day 8 (n:41), 60-67% at day 30 (n:41) and 67% at day 90 (n:18).

CONCLUSION

Fluoroscopy guided L5-S1 transforaminal injection showed good efficacy in the treatment of S1 radiculopathy.

Interleukin 1 Polymorphisms and Intervertebral Disc Degeneration

BACKGROUND

Enzymatic breakdown of the extracellular matrix, and possibly local inflammation, contributes to intervertebral disc degeneration. We investigated whether polymorphisms within the IL-1 gene locus are associated with lumbar disc degeneration and whether the effect of occupational physical load on disc degeneration is modified by the polymorphisms.

METHODS

Genotypes were determined from 133 middle-aged men who underwent magnetic resonance imaging of the lumbar spine. The participants represented 3 occupations: 40 were machine drivers, 42 carpenters, and 51 office workers. We evaluated decreased signal intensity of the nucleus pulposus, disc bulges, and decreased disc height as signs of degeneration in the L2/L3-L5/S1 discs.

RESULTS

The odds ratio for disc bulges was 2.4 (95% confidence interval = 1.2-4.8) and 1.9 (1.0-3.7), in carriers of the IL-1alphaT or IL-1betaT alleles, respectively. The TT genotype of the IL-1alpha gene carried more than 3-fold risk of disc bulges as compared with the CC genotype.

CONCLUSIONS

IL-1 gene cluster polymorphisms could affect the risk of disc degeneration. The effect of physical workload seems to be modified by the IL-1 gene polymorphisms.

Possible association of interleukin 1 gene locus polymorphisms with low back pain

Based on a hypothesis that interleukin 1 (IL-1) activity is associated with low back pain (LBP), we investigated relationships between previously described functional IL-1 gene polymorphisms and LBP. The subjects were a subgroup of a Finnish study cohort. The IL-1alpha(C(889)-T), IL-1beta(C(3954)-T) and IL-1 receptor antagonist (IL-1RN)(G(1812)-A, G(1887)-C and T(11100)-C) polymorphisms were genotyped in 131 middle-aged men from three occupational groups (machine drivers, carpenters and office workers). A questionnaire inquired about individual and lifestyle characteristics and the occurrence of LBP, the number of days with pain and days with limitation of daily activities because of pain, and pain intensity, during the past 12 months. Lumbar disc degeneration was determined with magnetic resonance imaging. Carriers of the IL-1RNA(1812) allele had an increased risk of LBP (OR 2.5, 95% CI 1.0-6.0) and carriers of this allele in combination with the IL-1alphaT(889) or IL-1betaT(3954) allele had a higher risk of and more days with LBP than non-carriers. Pain intensity was associated with the simultaneous carriage of the IL-1alphaT(889) and IL-1RNA(1812) alleles (OR 3.7, 95% CI 1.2-11.9). Multiple regression analyses allowing for occupation and disc degeneration showed that carriage of the IL-1RNA(1812) allele was associated with the occurrence of pain, the number of days with pain and days with limitations of daily activities. Carriage of the IL-1betaT(3954) allele was associated with the number of days with pain. The results suggest a possible contribution of the IL-1 gene locus polymorphisms to the pathogenesis of LBP. The possibility of chance findings cannot be excluded due to the small sample size.

Interleukin-6 production is upregulated by interaction between disc tissue and macrophages

STUDY DESIGN

Interleukin (IL)-6 production was investigated using a coculture system of disc tissue and macrophages.

OBJECTIVES

The purpose of this study was to investigate the interaction between intervertebral disc tissue and macrophages in terms of IL-6 production.

SUMMARY OF BACKGROUND DATA

IL-6 production is observed in human herniated disc specimens, and there is a correlation between IL-6 production and neurologic symptoms. However, the mechanism of IL-6 production in the herniated disc is not clear.

MATERIALS AND METHODS

Coccygeal intervertebral discs and exudated peritoneal macrophages were obtained from male Sprague-Dawley rats. Macrophages and intervertebral disc without endplates were cocultured in a serum-free medium. Fat tissue culture with or without macrophages, intervertebral disc alone, and macrophages alone were used for controls. The supernatant fluid of the culture was utilized for the enzyme-linked immunosorbent assay. The precipitations of macrophages and disc coculture were used for semiquantitative RT-PCR for IL-6. Immunohistochemical staining for IL-6 and the macrophages marker (ED2) were also carried out using disc tissue cultured with macrophages.

RESULTS

IL-6 production level was significantly increased in the coculture of intervertebral disc and macrophages (P < 0.01). However, there was no significant production of IL-6 in the control groups. The precipitations from coculture of macrophages and disc expressed IL-6 mRNA in semiquantitative RT-PCR. Immunohistochemical staining revealed most IL-6 producing cells were also positive for ED2, which adheres to or infiltrates the peripheral area of the nucleus pulposus.

CONCLUSIONS

Our results demonstrated that interaction between disc tissue and macrophage is necessary for upregulation of IL-6 production. Immunohistochemical staining also indicated that infiltrated macrophages played a major role in production of IL-6, suggesting that infiltration of macrophages into herniated disc material may be a trigger for IL-6 production and associated neurologic symptoms.

Temperatures within the lumbar disc and endplates during intradiscal electrothermal therapy: formulation of a predictive temperature map in relation to distance from the catheter

STUDY DESIGN

Temperatures were measured in human cadaveric lumbar discs during intradiscal electrothermal therapy.

OBJECTIVES

To determine if sufficient temperatures for collagen denaturation and nociceptive ablation can be achieved at clinically significant distances from the intradiscal electrothermal therapy heating catheter.

SUMMARY OF BACKGROUND DATA

Previous cadaveric studies have contested the ability of the intradiscal electrothermal therapy catheter to produce sufficient temperatures to denature collagen and cause neural ablation within the posterior anulus of the disc. However, these experiments used clinically unrepresentative device placements along the anterolateral anulus.

METHODS

Intradiscal electrothermal therapy was performed in 14 human cadaveric discs. Devices were inserted using a standard posterolateral approach to orient the heating catheter along the posterior anulus. Temperature recordings were collected using multiple sensors placed along the posterior anulus, anterior anulus, and endplates.

RESULTS

Temperatures greater than 60 C and 65 C were achieved in 14 and 5 specimens, respectively, at distances up to 2 mm from the catheter. Between 2 and 4 mm, more than 60 C was achieved in all specimens. More than 45 C was achieved in all specimens at distances of 9 to 14 mm from the device.

CONCLUSIONS

Temperatures sufficient for collagen denaturation and nociceptive ablation were detected at distances greater than previously documented. These data suggest that intradiscal electrothermal therapy's proposed heat-dependent mechanisms of action are achievable in most discs. Among other factors, interspecimen variability of maximum temperatures may help explain the somewhat inconsistent clinical results following intradiscal electrothermal therapy.

Intervertebral disc degeneration: the role of the mitochondrial pathway in annulus fibrosus cell apoptosis induced by overload

Degeneration of the intervertebral disk (IVD) is a major pathological process implicated in low back pain and is a prerequisite to disk herniation. Although mechanical stress is an important modulator of the degeneration, the underlying molecular mechanism remains unclear. The association of human IVD degeneration, assessed by magnetic resonance imaging, with annulus fibrosus cell apoptosis and anti-cytochrome c staining revealed that the activation of the mitochondria-dependent apoptosome was a major event in the degeneration process. Mouse models of IVD degeneration were used to investigate the role of the mechanical stress in this process. The application of mechanical overload (1.3 MPa) for 24 hours induced annulus fibrosus cell apoptosis and led to severe degeneration of the mouse disks. Immunostaining revealed cytochrome c release but not Fas-L generation. The role of the caspase-9-dependent mitochondrial pathway in annulus fibrosus cell apoptosis induced by overload was investigated further with the use of cultured rabbit IVD cells in a stretch device. Mechanical overload (15% area change) induced apoptosis with increased caspase-9 activity and decreased mitochondrial membrane potential. Furthermore, Z-LEHD-FMK, a caspase-9 inhibitor, but not Z-IETD-FMK, a caspase-8 inhibitor, attenuated the overload-induced apoptosis. Our results from human samples, mouse models, and annulus fibrosus culture experiments demonstrate that the mechanical overload-induced IVD degeneration is mediated through the mitochondrial apoptotic pathway in IVD cells.

Human intervertebral disc cell culture for disc disorders

Repair of degenerated intervertebral discs by engineered tissue is a clinical challenge in spinal surgery. Prerequisites are cultivation of intervertebral disc cells and determination of their biologic properties. The influence of disc damage in different spinal disorders on the outcome of disc cell cultures has not been discussed previously. This study showed the feasibility of cultivation of cells from damaged human intervertebral discs and the dependence of cellular culture properties on the underlying disc disorder. Human intervertebral disc cells were isolated from disc tissue obtained during surgical procedures for scoliosis, osteochondrosis, and disc herniation. After proliferation in monolayer culture, cells were embedded in a mixed matrix composed of fibrin and hyaluronic acid. Deoxyribonucleic acid content, hydroxyproline content, and proteoglycan synthesis were determined on Days 7, 14, and 21. In a three-dimensional environment only cells obtained from scoliotic and osteochondrotic discs showed significant deoxyribonucleic acid and proteoglycan synthesis. However, hydroxyproline content increased only in cells from scoliotic discs. The results of this study show that the formation of extracellular matrix components under three-dimensional culture conditions is dependent on the nature of intervertebral disc damage of the tissue processed.

Percutaneous plasma decompression alters cytokine expression in injured porcine intervertebral discs

BACKGROUND CONTEXT

Discectomy is a surgical technique commonly used to treat bulging or herniated discs causing nerve root compression. Clinical data suggest discectomy may also help patients with contained discs and no clear neural compromise. However, the mechanisms of clinical efficacy are uncertain, and consequently bases for treatment optimization are limited.

PURPOSE

To determine the effect of percutaneous plasma decompression on the histologic, morphologic, biochemical and biomechanical features of degenerating intervertebral discs.

STUDY DESIGN

An adult porcine model of disc degeneration was used to establish a degenerative baseline against which to evaluate discectomy efficacy.

OUTCOME MEASURES

Cytokines interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha were measured from tissue samples using enzyme-linked immunosorbent assay. Histology and morphology images were rated for degenerative findings (of cells and matrix) in both the nucleus and annulus. Proteoglycan content was determined, and intact specimen stiffness and flexibility were measured biomechanically. Magnetic resonance images were collected for biomechanical specimens.

METHODS

Using a retroperitoneal surgical approach, stab incisions were made in four or five lumbar discs per spine in 12 minipigs. Animals were allocated into one of three groups: 6-week recovery, 12-week recovery and percutaneous plasma decompression using an electrosurgical device at 6 weeks with recovery for 6 additional weeks. Four additional animals served as controls.

RESULTS

Discs treated with discectomy had a significant increase in IL-8 and a decrease in IL-1 as compared with the 12-week, nontreated discs. There were no significant differences in morphologic and biomechanical parameters or proteoglycan content between treated discs and time-matched, nontreated discs.

CONCLUSIONS

Our results demonstrate that percutaneous plasma discectomy alters the expression of inflammatory cytokines in degenerated discs, leading to a decrease in IL-1 and an increase in IL-8. Whereas both IL-1 and IL-8 have hyperalgesic properties, IL-1 is likely to be a more important pathophysiologic factor in painful disc disorders than IL-8. Therefore, the alteration in cytokine expression that we observed is consistent with this effect as a mechanism of pain relief after discectomy. In addition, given that IL-1 is catabolic in injured tissue and IL-8 is anabolic, our results suggest that a percutaneous plasma discectomy may be capable of initiating a repair response in the disc.

Human nucleus pulposis can respond to a pro-inflammatory stimulus

STUDY DESIGN

Disc tissue obtained from patients undergoing surgery for scoliosis, lumbar radiculopathy, and discogenic pain was cultured under basal and lipopolysaccharide-stimulated conditions and the medium analyzed for production of a range of pro-inflammatory mediators.

OBJECTIVES

This study was conducted to confirm that the human intervertebral disc is capable of responding to a pro-inflammatory stimulus and to identify the principal mediators involved in any response.

SUMMARY OF BACKGROUND DATA

Degenerate human disc tissue has been shown to spontaneously secrete a number of pro-inflammatory mediators. The importance of these molecules in the pathophysiology of symptomatic disc degeneration is increasingly recognized. Human nucleus pulposus has been shown to synthesize increased amounts of interleukin (IL)-6, prostaglandin E2 (PGE2), and nitric oxide in response to stimulation with IL-1beta. Murine nucleus pulposus synthesizes increased amounts of IL-1beta, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor in response to lipopolysaccharide stimulation. Lipopolysaccharide is a potent inducer of tumor necrosis factor-alpha (TNF-alpha), which is thought to play an important role in the pathophysiology of sciatica. To date, human nucleus pulposus has not been shown to secrete TNF-alpha in response to a pro-inflammatory stimulus.

METHODS

Human disc tissue obtained from patients undergoing surgery for scoliosis, lumbar radiculopathy, and discogenic pain was cultured under basal and lipopolysaccharide-stimulated conditions and the medium subsequently analyzed for a range of pro-inflammatory mediators.

RESULTS

None of the specimens produced any TNF-alpha, IL-1beta, granulocyte-macrophage colony-stimulating factor, or leukotriene B4. Measurable quantities of IL-6, IL-8, PGE2, MCP-1, basic fibroblast growth factor, and trans forming growth factor-beta1 were produced by a number of specimens. Lipopolysaccharide significantly increased IL-6, IL-8, and PGE2 production in both control and degenerate disc tissue. Degenerate disc specimens responded more vigorously to lipopolysaccharide stimulation than scoliotic specimens.

CONCLUSIONS

We conclude that both scoliotic and degenerate human nucleus pulposus can respond to an exogenous pro-inflammatory stimulus by secreting increased amounts of IL-6, IL-8, and PGE2 but not TNF-alpha and that degenerate disc tissue is more sensitive to a pro-inflammatory stimulus than its scoliotic counterpart.

Cyclic tensile stretch modulates proteoglycan production by intervertebral disc annulus fibrosus cells through production of nitrite oxide

Degeneration of the intervertebral disc is the main pathophysiological process implicated in low back pain and is a prerequisite to disc herniation. Clinically, mechanical forces are important modulators of the degeneration, but the underlying molecular mechanism is not known and needs investigation to identify the biological target. The aim of this work was to study, at the molecular level, the effects of cyclic tensile stretch (CTS) on the production of proteoglycan by intervertebral disc annulus fibrosus cells since proteoglycans seem to be implicated in the dynamic process of intervertebral disc degeneration. Such cells of rabbit were cultured at high density on plates with a flexible bottom. CTS was applied with use of a pressure-operated instrument to deform the plates. With CTS at 1% elongation (1 Hz frequency), the level of (35)S-labeled neosynthesized proteoglycans that accumulated in the cellular pool or were secreted in the culture medium did not change, but at 5% elongation, the level was significantly reduced after 8 h of stimulation (30 and 21%, respectively) and further reduced at 24 h (43 and 41%, respectively). Introducing the protein synthesis inhibitor cycloheximide had no effect on this result. Neither aggrecan and biglycan expression nor proteoglycan physical properties were modified. The level of nitrite oxide production significantly increased by 3.5 times after 8 h of 5% elongation. Introducing the nitric oxide synthase (NOS) inhibitors N(G)-methyl-l-arginine or N-omega nitro-l-arginine diminished the effects of CTS on the production of nitrite oxide and proteoglycans. By contrast, introducing N-iminoethyl-l-lysine (a more specific inhibitor of inductible NOS [iNOS]) had little or no effect. Taken together, these results suggest that cNOS activation seems to be more implicated in the 5% CTS modulation of proteoglycan production than iNOS activation. These results suggest that CTS can help regulate the intervertebral disc matrix by decreasing proteoglycan production through a post-translational regulation involving nitrite oxide. This result could be of interest in the development of local therapeutic strategies aimed at controlling intervertebral disc degeneration.

Prolonged spinal loading induces matrix metalloproteinase-2 activation in intervertebral discs

STUDY DESIGN

An established in vivo mouse model of compression-induced disc degeneration was used to investigate the effects of load on matrix catabolism.

OBJECTIVES

To determine whether matrix metalloproteinase-2 expression in discs is modulated by mechanical load and to characterize the regulation of matrix metalloproteinase-2 activity.

SUMMARY OF BACKGROUND DATA

We have previously shown that static compression of discs elicits changes in tissue architecture consistent with those seen with degeneration. Evidence in the literature demonstrates the existence of matrix metalloproteinases in both healthy and pathologic discs and suggests that mechanical load may influence matrix metalloproteinase expression and activity.

METHODS

Static compression was applied to mouse coccygeal discs in vivo for 1, 4, or 7 days, with adjacent discs serving as sham control. An activity assay was used to measure concentrations of active and total matrix metalloproteinase-2, and changes in matrix metalloproteinase-2 gene expression relative to beta-actin were assessed by reverse transcriptase-polymerase chain reaction.

RESULTS

Although no change was seen relative to sham after 1 day of load, the proportion of total matrix metalloproteinase-2 that was active increased after 4 days. This elevation was sustained through 7 days of compression, with no significant differences in total matrix metalloproteinase-2 concentrations among discs throughout the range of time points examined. Semiquantitative reverse transcriptase-polymerase chain reaction demonstrated no significant changes in matrix metalloproteinase-2 gene expression at 1 day or 4 days.

CONCLUSIONS

In this model, regulation of matrix metalloproteinase-2 activity occurs primarily through enhanced molecular activation of the proenzyme rather than through elevated gene expression or translation. Our results suggest that matrix metalloproteinase-2 may have a role in load-induced changes in disc architecture.

Glucosamine and chondroitin sulfate supplementation to treat symptomatic disc degeneration: biochemical rationale and case report

BACKGROUND

Glucosamine and chondroitin sulfate preparations are widely used as food supplements against osteoarthritis, but critics are skeptical about their efficacy, because of the lack of convincing clinical trials and a reasonable scientific rationale for the use of these nutraceuticals. Most trials were on osteoarthritis of the knee, while virtually no documentation exists on spinal disc degeneration. The purpose of this article is to highlight the potential of these food additives against cartilage degeneration in general, and against symptomatic spinal disc degeneration in particular, as is illustrated by a case report. The water content of the intervertebral disc is a reliable measure of its degeneration/ regeneration status, and can be objectively determined by Magnetic Resonance Imaging (MRI) signals.

CASE PRESENTATION

Oral intake of glucosamine and chondroitin sulfate for two years associated with disk recovery (brightening of MRI signal) in a case of symptomatic spinal disc degeneration. We provide a biochemical explanation for the possible efficacy of these nutraceuticals. They are bioavailable to cartilage chondrocytes, may stimulate the biosynthesis and inhibit the breakdown of their extracellular matrix proteoglycans.

CONCLUSION

The case suggests that long-term glucosamine and chondroitin sulfate intake may counteract symptomatic spinal disc degeneration, particularly at an early stage. However, definite proof requires well-conducted clinical trials with these food supplements, in which disc de-/regeneration can be objectively determined by MRI. A number of biochemical reasons (that mechanistically need to be further resolved) explain why these agents may have cartilage structure- and symptom-modifying effects, suggesting their therapeutic efficacy against osteoarthritis in general.

Comparison of dynamic posteroanterior spinal stiffness to plain film radiographic images of lumbar disk height

BACKGROUND

Assessments of spinal stiffness have become more popular in recent years as a noninvasive objective biomechanical means to evaluate the human spine. Studies investigating posteroanterior (PA) forces in spinal stiffness assessment have shown relationships to spinal level, body type, and lumbar extensor muscle activity. Such measures may be important determinants to discriminate between patients with low back pain (LBP) and asymptomatic subjects.

OBJECTIVE

To determine the relationships between dynamic PA spinal stiffness and radiographic measures of lower lumbar disk height and disk degeneration.

METHODS

L4 and L5 posterior disk height (PDH), vertebral body height (PVH), anterior disk height (ADH), and vertebral body height (AVH) were obtained from digitized plain film anteroposterior (AP) and lateral radiographs of 18 symptomatic LBP patients presenting to a chiropractic office (8 female patients and 10 male patients, aged 15-69 years, mean 44.3, SD 15.4 years). Disk degeneration (DD) and facet arthrosis (FA) were qualitatively assessed from the films by an independent examiner. Anterior disk height ratios (ADHR = ADH/AVH) and posterior disk height ratios (PDHR = PDH/PVH) were calculated from the disk height measurements and were compared to L4 and L5 posteroanterior spinal stiffness obtained using a previously validated mechanical impedance stiffness assessment procedure.

RESULTS

One third of the subjects were found to have radiographic evidence of mild or moderate DD and approximately two thirds of the subjects showed signs of mild or moderate FA. The L4 and L5 anterior disk height and posterior disk height were approximately one half and one fifth of the respective vertebral body heights, and the PA stiffness was greater at L4 than at L5. Male subjects had a greater ADHR than female subjects, but female subjects had a greater L4 and L5 PA stiffness in comparison to male subjects; however, these differences were not statistically significant. Posteroanterior L5 vertebral stiffness was found to be significantly correlated to the L5 PDHR.

CONCLUSIONS

Computations of spinal input impedance are relatively simple to perform, can provide a noninvasive measure of the dynamic mechanical behavior of the spine, appear to have potential to discriminate pathologic changes to the spine, and warrant further study on a larger sample of normal subjects and patients.

Complement membrane attack complexes in pathologic disc tissues

STUDY DESIGN

Complement membrane attack complexes were located in lumbar spine disc tissues by immunohistochemistry. Their occurrence was compared in control discs obtained from organ donors (CD), discs showing a normal macroscopic anatomy, samples of intervertebral disc herniations (DH), and intervertebral discs found to be degenerated by discography, but not herniated (DD).

OBJECTIVE

To look for a possible role of complement activation, specifically complement membrane attack complexes, an end product of the classic immune complex-mediated complement activation pathway, in disc pathophysiology.

SUMMARY OF BACKGROUND DATA

Recent immunohistochemical and biochemical studies suggest a possible role for immune complexes, as observed by immunohistochemical location and biochemical assay of immunoglobulins M and G in intervertebral disc pathophysiology. Immune complexes may trigger complement activation and ultimately cell lysis. There are, however, currently no reports on complement activation in disc tissues, although immune (antigen-antibody) complexes have been demonstrated. Such immune complexes have been reported to occur on or near to disc cells in DH tissues.

METHODS

Thin frozen sections of disc tissue from CD (n = 9 discs), DH (n = 58 discs), and DD (n = 11 discs) were cut and then immunostained with a monoclonal antibody to the complement membrane attack complex (C5b-9) using avidin-biotin complex (ABC) immunostaining. The presence or absence of complement membrane attack complex immunoreactivity was compared in the various subtypes of DH and also with preoperative duration of radicular pain.

RESULTS

Complement membrane attack complexes could be observed in none of the CDs studied. In contrast, in more than one third of both the DH (21/58, 36.2%) and the DD (4/11, 36.4%), immunoreactivity to complement membrane attack complexes could be observed in disc cells. In DD discs, immunoreactivity to complement membrane attack complexes was most often present in anulus fibrosus samples (5/13, 38.5%). With respect to subtype of DH, complement membrane attack complexes were observed in 19 of 36 sequestrated discs (52.8%), 1 of 16 extrusions (6.3%), and 1 of 6 protrusions (16.7%). Complement membrane attack complexes were more often present with shorter pain duration (P= 0.03), but showed no relation to age. Disc cells often showed a heavy staining pattern for complement membrane attack complexes, suggesting an abundance of these complexes lodged in the membrane of the cells.

CONCLUSIONS

The predominant presence of complement membrane attack complexes in sequestrated disc tissue could suggest a role in DH tissue-induced sciatica. Possibly immune (antigen-antibody) complexes, reported in previous studies, trigger the classic pathway of complement activation, with complement membrane attack complexes as the final product. Complement membrane attack complexes also appear to have some as yet undefined role in degenerated nonherniated disc tissue, with a predominant presence in the anulus fibrosus cells of such discs.

The role of cyclooxygenase-2 in lumbar disc herniation

STUDY DESIGN

The expression of cyclooxygenase-2 was studied immunohistologically in specimens from lumbar disc herniation. The cultured disc cells also were examined to evaluate the significance of cyclooxygenase-2, which might be involved in the pathogenesis of lumbar disc herniation.

OBJECTIVE

To investigate whether cyclooxygenase-2 might be involved in the pathogenesis of lumbar disc herniation.

SUMMARY OF BACKGROUND DATA

Prostaglandin E2 is one of the most important mediators contributing to pathogenetic components of lumbar disc herniation. Cyclooxygenase-2, the rate-limiting enzyme of prostaglandin E2 synthesis, has been identified and extensively investigated in other inflammatory diseases. However, the role of cyclooxygenase-2 in lumbar disc herniation has never been addressed.

METHODS

Fifteen specimens from patients with lumbar disc herniation and five control discs from traumatic burst fracture were harvested. The expression of cyclooxygenase-2 was evaluated immunohistologically. The ability of cultured disc cells to produce prostaglandin E2 with inflammatory stimulus in the presence or absence of a selective inhibitor of cyclooxygenase-2 was investigated. At the same time, the induction of cyclooxygenase-2 mRNA of these cells by reverse transcriptase-polymerase chain reaction was detected. The manner in which this prostaglandin E2 production could be suppressed by various doses of a cyclooxygenase-2 inhibitor also was investigated.

RESULTS

Immunohistologically, the expression of cyclooxygenase-2 was observed only in the lumbar disc herniation specimens. The cultured cells had a strong ability to produce prostaglandin E2 coinciding with cyclooxygenase-2 mRNA induction. A selective inhibitor of cyclooxygenase-2 inhibited this prostaglandin E2 production in a dose-dependent manner.

CONCLUSION

Cyclooxygenase-2 might be involved in the pathogenesis of lumbar disc herniation through upregulation of prostaglandin E2 production.