Toru Takada

Fas Ligand Exists on Intervertebral Disc Cells : A Potential Molecular Mechanism for Immune Privilege of the Disc

Study Design. Rat and human intervertebral disc specimens were examined immunohistochemically. Reverse transcription polymerase chain reaction (RT-PCR) analysis was also performed on rat disc tissue to demonstrate the existence of Fas ligand. Objective. To clarify the existence of Fas ligand on intact intervertebral disc cells. Summary of Background Data. The nucleus pulposus has been reported to be an immune-privileged site. The immune-privileged characteristic in other tissues such as the retina and testis has been attributed to the local expression of Fas ligand, which acts by inducing apoptosis of invading Fas-positive T-cells. The existence of Fas ligand in normal disc cells has not yet been addressed. Methods. Skeletally mature SD male rats were killed, and the coccygeal discs were harvested. Human disc specimens were obtained from idiopathic scoliosis patients during surgical procedures. Immunohistochemical staining for Fas ligand was performed for cross-sections of the discs by standard procedures. Reverse transcription polymerase chain reaction analysis was also carried out to demonstrate Fas ligand mRNA expression on rat intervertebral discs. Testes of the rats were used for positive controls, and muscles were used for negative controls. The sections were observed by light microscopy. Results. The nucleus pulposus cells exhibited intense positive immune staining for Fas ligand. The outer anulus fibrosus cells and notochordal cells exhibited little immunopositivity. The positive controls exhibited positive immune staining, and the negative control showed no immunopositivity. The result of RT-PCR confirmed the existence of Fas ligand in disc cells. The human nucleus pulposus cells showed a similar predilection to rat disc cells. Conclusions. We demonstrated the existence of Fas ligand on disc cells, which should play a key role in the potential molecular mechanism to maintain immune privilege of the disc. Immune privilege and Fas ligand expression of the intervertebral disc may provide a new insight for basic science research as well as clinical treatments for disc degenerative diseases, including disc herniation with radicular pain.

Sustained transgene expression in intervertebral disc cells in vivo mediated by microbubble-enhanced ultrasound gene therapy.

Study Design. In vivo studies using a rat model were performed to determine the feasibility of microbubble-enhanced ultrasound gene transfer technique to the intervertebral disc. Objectives. 1) To establish this microbubble-enhanced ultrasound gene therapy technique for intervertebral disc cells in vivo without using viral vectors and 2) to estimate the duration of transgene expression in vivo. Summary of Background Data. Intervertebral disc degeneration and associated spinal disorders remain a formidable problem. Although gene therapy approaches have been reported as having promising therapeutic potential to regenerate the disc, concerns over safety issues using recombinant viral vectors limits its application. Successful gene transfer using ultrasound has been reported in muscle and cardiovascular systems in vivo. Materials and Methods. Two different reporter plasmid DNA encoding green fluorescent protein (GFP) and firefly luciferase were used. Plasmid DNA was mixed with ultrasonography contrast agent (microbubbles) and injected into coccygeal intervertebral discs of Sprague-Dawley rats. The therapeutic ultrasound was irradiated on the surface of injected discs. Rats were killed 1, 3, 6, 12, and 24 weeks after gene transduction. Harvested nucleus pulposus tissues were used for evaluation of transgene expression. The intact discs were used as a control. Results. Seven days after gene transfection, considerable numbers of GFP-positive cells were observed in nucleus pulposus from the GFP-transfected group. Luciferase assay revealed that the ultrasound group demonstrated approximately an 11-fold increase in luciferase activity over the plasmid DNA-only group. Furthermore, transgene expression mediated by this method was observed, at least up to 24 weeks. Conclusions. Our study indicated that ultrasound transfection method with microbubbles significantly enhanced transfection efficiency of plasmid DNA into the nucleus pulposus cells in vivo. Furthermore, the sustained transgene expression in vivo was possible up to 24 weeks. The long-term gene expression mediated by simple and safe procedure has important clinical applications, including the treatment of chronic types of disease such as degenerative disc diseases.

Rat tail static compression model mimics extracellular matrix metabolic imbalances of matrix metalloproteinases, aggrecanases, and tissue inhibitors of metalloproteinases in intervertebral disc degeneration

IntroductionThe longitudinal degradation mechanism of extracellular matrix (ECM) in the interbertebral disc remains unclear. Our objective was to elucidate catabolic and anabolic gene expression profiles and their balances in intervertebral disc degeneration using a static compression model.MethodsForty-eight 12-week-old male Sprague-Dawley rat tails were instrumented with an Ilizarov-type device with springs and loaded statically at 1.3 MPa for up to 56 days. Experimental loaded and distal-unloaded control discs were harvested and analyzed by real-time reverse transcription-polymerase chain reaction (PCR) messenger RNA quantification for catabolic genes [matrix metalloproteinase (MMP)-1a, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and ADAMTS-5], anti-catabolic genes [tissue inhibitor of metalloproteinases (TIMP)-1, TIMP-2, and TIMP-3], ECM genes [aggrecan-1, collagen type 1-α1, and collagen type 2-α1], and pro-inflammatory cytokine genes [tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, and IL-6]. Immunohistochemistry for MMP-3, ADAMTS-4, ADAMTS-5, TIMP-1, TIMP-2, and TIMP-3 was performed to assess their protein expression level and distribution. The presence of MMP- and aggrecanase-cleaved aggrecan neoepitopes was similarly investigated to evaluate aggrecanolytic activity.ResultsQuantitative PCR demonstrated up-regulation of all MMPs and ADAMTS-4 but not ADAMTS-5. TIMP-1 and TIMP-2 were almost unchanged while TIMP-3 was down-regulated. Down-regulation of aggrecan-1 and collagen type 2-α1 and up-regulation of collagen type 1-α1 were observed. Despite TNF-α elevation, ILs developed little to no up-regulation. Immunohistochemistry showed, in the nucleus pulposus, the percentage of immunopositive cells of MMP-cleaved aggrecan neoepitope increased from 7 through 56 days with increased MMP-3 and decreased TIMP-1 and TIMP-2 immunopositivity. The percentage of immunopositive cells of aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with decreased TIMP-3 immunopositivity. In the annulus fibrosus, MMP-cleaved aggrecan neoepitope presented much the same expression pattern. Aggrecanase-cleaved aggrecan neoepitope increased at 7 and 28 days only with increased ADAMTS-4 and ADAMTS-5 immunopositivity.ConclusionsThis rat tail sustained static compression model mimics ECM metabolic imbalances of MMPs, aggrecanases, and TIMPs in human degenerative discs. A dominant imbalance of MMP-3/TIMP-1 and TIMP-2 relative to ADAMTS-4 and ADAMTS-5/TIMP-3 signifies an advanced stage of intervertebral disc degeneration.

Fas ligand expression on human nucleus pulposus cells decreases with disc degeneration processes

BackgroundThe intervertebral disc has been reported to be an immunologically privileged environment, possibly mediated by Fas ligand (FasL) expression. On the other hand, recent studies have shown the infiltration of host immune cells into the degenerated disc, which may indicate the failure of the immune-privilege feature of the disc with degeneration. However, the relationship between FasL expression and disc degeneration is still unclear. Therefore, the purpose of this study was to clarify the relationship between FasL expression and disc degeneration.MethodsTen human degenerated disc specimens were obtained from spondylolisthesis patients and ten nondegenerated discs from idiopathic scoliosis patients during surgical procedures. Immunohistochemical staining was performed to determine the presence of FasL in cross-sections of those discs. Parts of the disc tissues were used to examine FasL expression quantitatively with Western blot analysis. To examine whether the change in FasL expression was influenced by aging, an animal study comparing the discs from young and old rats were performed using magnetic resonance imaging (MRI) and real-time polymerase chain reaction (PCR) assessment.ResultsNucleus pulposus cells showed strong positive staining for FasL in all specimens examined. Quantitative examination demonstrated a significant decrease in FasL expression in the degenerated group compared with the nondegenerated group (average 67.6%, P<0.05). MRI showed no significant differences in the grade of disc degeneration between young and old rats, and also no significant difference in FasL mRNA in real-time PCR assay.ConclusionsThe current results indicate that FasL and its potential mechanism of immunological privilege could influence the protection of the intervertebral disc against degeneration.

Kinematic magnetic resonance imaging of a thoracic spinal extradural arachnoid cyst: an alternative suggestion for exacerbation of symptoms during straining.

Study Design. A case study of an extradural arachnoid cyst using kinematic magnetic resonance imaging. Objectives. To access the dynamic and pathologic changes of an extradural subarachnoid cyst during straining by kinematic magnetic resonance imaging and to clarify the pathomechanism of a fluctuation in symptoms. Summary of Background Data. Extradural arachnoid cysts of the spine are an uncommon cause of myelopathy secondary to spinal cord compression; however, the precise mechanism of cord compression and subsequent symptoms remain unclear. Methods. A 31-year-old female presented with severe left lower thoracic back pain and leg stiffness, which were exacerbated by coughing and straining. She was diagnosed with an extradural subarachnoid cyst by magnetic resonance imaging. Kinematic magnetic resonance imaging was carried out to assess the dynamic change of the extradural cyst and to demonstrate the mechanism causing her chest pain and leg stiffness during straining. Results. Kinematic magnetic resonance imaging demonstrated that the cyst wall was compressed, and the size of extradural cyst was decreased for several seconds during straining. Furthermore, the ring of cerebrospinal fluid was gradually compressed circumferentially. After surgery, the patient experienced complete relief of symptoms. Postoperative kinematic magnetic resonance imaging revealed good decompressive results had been obtained, and the ring of cerebrospinal fluid was preserved even when the patient strained for a few minutes. Conclusions. Kinematic magnetic resonance imaging study demonstrated that pressure changes which occur in the extradural space as well as in the arachnoid cyst might cause spinal cord compression and result in intermittent exacerbation of symptoms.

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.

Unusual metastasis to the cauda equina from renal cell carcinoma.

Study Design. This is a case report of a patient with renal cell carcinoma and intradural metastasis to the cauda equina. Objective. To present a rare case of an intradural metastasis from renal cell carcinoma and to discuss the clinical features of metastatic tumors in the cauda equina and the possible mechanism of the tumor spread to the cauda equina. Summary of Background Data. Intradural spinal metastasis has been rarely reported in the English literature. Only two reports that describe the spread of metastatic renal cell carcinoma to the cauda equina have been published. Methods. A 61-year-old man who underwent a nephrectomy for the treatment of renal cell carcinoma presented with worsening low back pain that radiated to both legs. Magnetic resonance imaging showed an ill-defined tumor mass in the cauda equina at L3. After a recapping T-saw laminoplasty of L3 was performed, the tumor was excised and the nerves involved in the tumor were transected. Results. Pathologic examination showed papillary renal cell carcinoma with identical histology to the primary tumor. The patient’s low back pain and radiating leg pain were relieved after operating. Conclusion. The majority of cauda equina tumors are primary tumors, and metastases are very rare. Intradural spinal metastasis pain is a characteristic cramping pain provoked by light percussion on the lumbar spine, becoming severe when sleeping in the flexion or sitting position. Magnetic resonance imaging is a useful tool for detecting intraspinal metastasis when the patient is complaining of a unique pain. A recapping T-saw laminoplasty to preserve posterior elements with tumor removal is feasible for relieving pain and demonstrating the pathology.

Fas ligand plays an important role for the production of pro‐inflammatory cytokines in intervertebral disc nucleus pulposus cells

It is suggested that pro‐inflammatory cytokines, which are produced by interaction of the intervertebral nucleus pulposus cells and macrophages, may be linked to the cause of pain of the intervertebral disc herniation. This study carries out the in vitro experiments to examine the mechanism, with the use of the co‐culture of an immortalized cell line of nucleus pulposus of the human intervertebral disc and the macrophage cell line. As a result, it is found that the production of pro‐inflammatory cytokines is significantly larger at the co‐culture group than at the independent culture group. Also, at the co‐culture group of macrophages and intervertebral nucleus pulposus cells with over‐expression of fas ligand (FasL), the production of pro‐inflammatory cytokines is found to be far larger. Furthermore, it is found that these pro‐inflammatory cytokines are produced mainly by the intervertebral nucleus pulposus cells with over‐expression of FasL, and that the expression of a disintegrin and metalloproteinase (ADAM) 10, which controls the expression of FasL and activates reverse signaling inside cells, also increases. From these findings, it is suggested that FasL and ADAM10 play an important role in the production of pro‐inflammatory cytokines coming from interaction of the intervertebral nucleus pulposus cells and macrophages.

Intervertebral disc and macrophage interaction induces mechanical hyperalgesia and cytokine production in a herniated disc model in rats

OBJECTIVE The expression of proinflammatory factors such as tumor necrosis factor α (TNFα), interleukin-6 (IL-6), IL-8, and prostaglandin E(2) (PGE(2) ) is significantly correlated with the symptoms of herniated disc disease. Among the different types of immune cells, macrophages are frequently noted in the herniated disc tissue. We undertook this study to clarify the interaction of the intervertebral disc (IVD) and macrophages with regard to the production of TNFα, IL-6, IL-8, and PGE(2) . METHODS We developed 2 animal models to assess the interactions of IVDs with macrophages in terms of TNFα, IL-6, IL-8, and PGE(2) production and pain-related behavior. We also cocultured IVDs and macrophages to assess the role of TNFα in IL-6, IL-8, and PGE(2) production. RESULTS IVD autografts induced TNFα, IL-6, IL-8, and cyclooxygenase 2 (COX-2) messenger RNA (mRNA) up-regulation; macrophage infiltration was seen shortly after the autograft was implanted. A significant decrease was noted in the mechanical threshold of the ipsilateral paw following the up-regulation of TNFα, IL-6, IL-8, and COX-2 mRNA. Only IVD and macrophage cocultures resulted in IL-8 and PGE(2) up-regulation. TNFα up-regulation was maximized before that of IL-6 and IL-8. TNFα neutralization attenuated production of IL-6 and PGE(2) , but not that of IL-8. Neutralization of TNFα and IL-8 significantly increased the paw withdrawal mechanical threshold in the IVD autograft and spinal nerve ligation model. CONCLUSION IVD-macrophage interaction plays a major role in sciatica and in the production of TNFα, IL-6, IL-8, and PGE(2) . TNFα is required for IL-6 and PGE(2) production, but not for IL-8 production, during IVD-macrophage interaction. Neutralization of TNFα and IL-8 can be a valuable therapy for herniated disc disease.

Matrix metalloproteinase (MMP)-3 gene up-regulation in a rat tail compression loading-induced disc degeneration model.

The rodent static compression loading‐induced disc degeneration model still has important gaps among the radiographic, magnetic resonance imaging (MRI), and histological schemes and the acute and chronic expression of catabolic genes such as matrix metalloproteinase (MMP)‐3. Our objectives were to assess the validity of a rat tail two‐disc static compression model and to elucidate a representative catabolic marker, MMP‐3 gene alterations, throughout the degenerative process. Static compression at 1.3 MPa for up to 56 days produced progressive disc height loss in radiographs, lower nucleus intensity on T2‐weighted MRIs, and histomorphological degeneration. Real‐time RT‐PCR mRNA quantification showed significant MMP‐3 up‐regulation in nucleus pulposus cells from 7 days and a significantly progressive increase as the loading duration lengthened, with high correlations to radiological degenerative scores. Immunohistochemistry demonstrated progressively increased positive staining for MMP‐3. These results validate this animal model for disc degeneration research. Progressive mRNA and protein‐distributional up‐regulations indicate the significant role of MMP‐3 and its feasibility as a disc degenerative marker. This model should prove useful for investigating the pathomechanism and for evaluating molecular therapies for degenerative disc disease.