Induction of cervical disc degeneration and discogenic pain by low concentration Propionibacterium acnes infection: an in vivo animal study.

BACKGROUND: Although cervical intervertebral disc (IVD) degeneration is closely associated with neck pain, its cause remains unclear. In this study, an animal model of cervical disc degeneration and discogenic neck pain induced by a low concentration of Propionibacterium acnes (P. acnes-L) is investigated to explore the possible mechanisms of cervical discogenic pain. METHODS: Cervical IVD degeneration and discitis was induced in 8-week-old male rats in C3-C6 IVDs through the anterior intervertebral puncture with intradiscal injections of low and high concentrations of P. acnes (P. acnes-L, n = 20 and P. acnes-H, n = 15) or Staphylococcus aureus (S. aureus, n = 15), compared to control (injection with PBS, n = 20). The structural changes in the cervical IVD using micro-CT, histological evaluation, and gene expression assays after MRI scans at 2 and 6 weeks post-modeling. The P. acnes-L induced IVD degeneration model was assessed for cervical spine MRI, histological degeneration, pain-like behaviors (guarding behavior and forepaw von Frey), nerve fiber growth in the IVD endplate region, and DRG TNF-α and CGRP. RESULTS: IVD injection with P. acnes-L induced IVD degeneration with decreased IVD height and MRI T2 values. IVD injection with P. acnes-H and S. aureus both lead to discitis-like changes on T2-weighted MRI, trabecular bone remodeling on micro-CT, and osseous fusion after damage in the cartilage endplate adjacent to the injected IVD. Eventually, rats in the P. acnes-L group exhibited significant nociceptive hypersensitivity, nerve fiber ingrowth was observed in the IVD endplate region, inflammatory activity in the DRG was significantly increased compared to the control group, and the expression of the pain neurotransmitter CGRP was significantly upregulated. CONCLUSION: P. acnes-L was validated to induce cervical IVD degeneration and discogenic pain phenotype, while P. acnes-H induced was identified to resemble septic discitis comparable to those caused by S. aureus infection.

Elevated regulatory T cells after antibiotic treatment of infectious spondylodiscitis as biomarker of recovery?

Dysregulated systemic immune responses during infectious spondylodiscitis (IS) may impair microbial clearance and bone resorption. Therefore, the aim of the study was to examine whether circulating regulatory T cells (Tregs) are elevated during IS and whether their frequency is associated with alterations in T cells and the presence of markers of bone resorption in the blood. A total of 19 patients hospitalized with IS were enrolled in this prospective study. Blood specimens were obtained during hospitalization and 6 weeks and 3 months after discharge. Flow cytometric analysis of CD4 and CD8 T cell subsets, the percentage of Tregs and serum levels of collagen type I fragments (S-CrossLap) were performed. Out of 19 enrolled patients with IS, microbial etiology was confirmed in 15 (78.9%) patients. All patients were treated with antibiotics for a median of 42 days, and no therapy failure was observed. Next, a significant serum C-reactive protein (S-CRP) decrease during the follow-up was observed, whereas the frequencies of Tregs remained higher than those of controls at all-time points (p < 0.001). In addition, Tregs demonstrated a weak negative correlation with S-CRP and S-CrossLap levels were within the norm at all-time points. Circulating Tregs were elevated in patients with IS and this elevation persisted even after the completion of antibiotic therapy. Moreover, this elevation was not associated with treatment failure, altered T cells, or increased markers of bone resorption.

Intervertebral disc cell chondroptosis elicits neutrophil response in Staphylococcus aureus spondylodiscitis.

To understand the pathophysiology of spondylodiscitis due to Staphylococcus aureus, an emerging infectious disease of the intervertebral disc (IVD) and vertebral body with a high complication rate, we combined clinical insights and experimental approaches. Clinical data and histological material of nine patients suffering from S. aureus spondylodiscitis were retrospectively collected at a single center. To mirror the clinical findings experimentally, we developed a novel porcine ex vivo model mimicking acute S. aureus spondylodiscitis and assessed the interaction between S. aureus and IVD cells within their native environment. In addition, the inflammatory features underlying this interaction were assessed in primary human IVD cells. Finally, mirroring the clinical findings, we assessed primary human neutrophils for their ability to respond to secreted inflammatory modulators of IVD cells upon the S. aureus challenge. Acute S. aureus spondylodiscitis in patients was characterized by tissue necrosis and neutrophil infiltration. Additionally, the presence of empty IVD cells' lacunae was observed. This was mirrored in the ex vivo porcine model, where S. aureus induced extensive IVD cell death, leading to empty lacunae. Concomitant engagement of the apoptotic and pyroptotic cell death pathways was observed in primary human IVD cells, resulting in cytokine release. Among the released cytokines, functionally intact neutrophil-priming as well as broad pro- and anti-inflammatory cytokines which are known for their involvement in IVD degeneration were found. In patients as well as ex vivo in a novel porcine model, S. aureus IVD infection caused IVD cell death, resulting in empty lacunae, which was accompanied by the release of inflammatory markers and recruitment of neutrophils. These findings offer valuable insights into the important role of inflammatory IVD cell death during spondylodiscitis and potential future therapeutic approaches.

68Ga-PSMA Uptake in Escherichia coli Spondylodiscitis.

In a patient with recently diagnosed intermediate-risk prostate cancer, Ga-prostate-specific-membrane-antigen (PSMA) PET/CT for primary staging discovered increased Ga-PSMA uptake in spondylodiscitis in the thoracic spine. The bacteria Escherichia coli was found both in blood cultures and bone biopsies from the thoracic lesion. This case presents spondylodiscitis as a potential benign pitfall to be aware of when interpreting PSMA PET/CT in prostate cancer patients.

18F-fluorodeoxyglucose uptake pattern in patients with suspected spondylodiscitis.

BACKGROUND: Infections of the spine are rare and often discovered late, but they can have a severe outcome with hospital case fatality rates of up to 17%. Efficient and early diagnosis is important, because early diagnosis and therapy improve outcome. The aim of the current study was to evaluate the clinical value of F-fluorodeoxyglucose (18F-FDG) uptake pattern in PET as a diagnostic modality for the detection of spondylodiscitis. MATERIALS AND METHODS: 18F-FDG-PET examinations of the spine were performed in 42 patients with suspected spondylodiscitis. Of these 42 patients, 13 had already undergone spinal surgery in the past, making initial definition of the test group difficult and complex. Qualitative analysis was based on 18F-FDG uptake patterns, and quantitative maximal standard uptake value measurements were ascertained. PET findings were verified by comparing them with combined information from intraoperative findings, blood results, microbiological investigations, histopathology, and clinical examination. RESULTS: Evidence of spondylodiscitis was correctly determined in 95% of patients and absence of spondylodiscitis in 86% of patients using 18F-FDG-PET. The detection of spondylodiscitis by 18F-FDG-PET had a sensitivity of 86% and a specificity of 95%. Three patients had false-negative and one patient a false-positive finding on 18F-FDG-PET. CONCLUSION: The application of 18F-FDG uptake patterns in 18F-FDG-PET helps to predict or exclude spondylodiscitis. Differentiation between inflammatory and degenerative changes in the vertebral body endplates is possible. Owing to the high specificity of this method, a negative PET result in the setting of a diagnostically unclear case diminishes the need for surgical intervention. 18F-FDG-PET is therefore an important tool in inflammation imaging and can be used in the diagnostic cascade of difficult cases with suspected spondylodiscitis. In contrast, a positive PET result does not always clearly establish the cause of increased 18F-FDG uptake.

Inflammatory and catabolic signalling in intervertebral discs: the roles of NF-κB and MAP kinases.

Painful intervertebral disc disease is characterised not only by an imbalance between anabolic (i.e., matrix synthesis) and catabolic (i.e., matrix degradation) processes, but also by inflammatory mechanisms. The increased expression and synthesis of matrix metalloproteinases and inflammatory factors is mediated by specific signal transduction, in particular the nuclear factor-kappaB (NF-kB) and mitogen-activated protein kinase (MAPK)-mediated pathways. NF-kB and MAPK have been identified as the master regulators of inflammation and catabolism in several musculoskeletal disorders (e.g., osteoarthritis), and recently growing evidence supports the importance of these signalling pathways in painful disc disease. With continuing research exploiting in vitro and in vivo model systems to elucidate the roles of these pathways in disc degeneration, it may be possible in the near future to specifically target these major inflammatory / catabolic signalling pathways to treat painful degenerative disc disease. In this perspective, we aim to summarise the current state of knowledge concerning the inflammatory and catabolic molecular pathways of intervertebral disc disease (IDD), with a detailed description of NF-kB and MAP kinase-mediated signal transduction in disc cells. Furthermore, we will discuss the emerging novel molecular treatment modalities for IDD using pharmacological inhibitors targeting these pathways.

[Expression and significance of growth-associated protein 43 in a rat model of intervertebral disc inflammation].

OBJECTIVE: To investigate the expression and significance of growth-associated protein 43 (GAP-43) in the dorsal root ganglion (DRG) and intervertebral disc in the rat model of intervertebral disc inflammation. METHODS: A total of 103 adult male Sprague Dawley rats (weighing, 200-250 g) were randomly divided into the experimental group (n = 48), the control group (n = 48), and the blank control group (n = 7). Fluoro-gold (F-G) as tracer was injected into the L6, 6 intervertebral disc of 3 groups; after 7 days of F-G injection, complete Freund's adjuvant (50 microL) and the same volume of saline were injected in the experimental group (to prepare the model of intervertebral disc inflammation) and the control group, respectively, and the blank control group had no further treatment. After 1, 3, 7, and 14 days, T13-L6 DRG and L5, 6 intervertebral disc of experimental group and control group were harvested to detect the GAP-43 by using fluorescent immunohistochemistry, in situ hybridization, and RT-PCR. The DRG and intervertebral disc of blank control group were also harvested after 8 days of F-G injection. RESULTS: Fluorescent immunohistochemistry results showed that the number of F-G-labeled GAP-43 immunoreaction (GAP-43-IR) cells of the DRGs in the experimental group was significantly higher than that in the control group (P < 0.05) at 3 days, and no significant difference was found at the other time points (P > 0.05). There was no significant difference in the cross-sectional area of F-G-labeled GAP-43-IR cells between the experimental group and the control group at each time point (P > 0.05). The co-expression of GAP-43 with calcitonin gene-related peptide (CGRP) and isolectin B4 (IB4)-binding glycoprotein exhibited that the expression of CGRP was 91.4% +/- 7.4% in the control group and was 87.6% +/- 7.8% in the experimental group, showing no significant difference between 2 groups (P > 0.05). There was no IB4-binding glycoprotein expression in GAP-43-IR cells of the DRGs in 2 groups. The expressions of GAP-43, CGRP, and IB4-positive nerve fibers in the intervertebral disc exhibited that the GAP-43-IR nerve fibers in the experimental group were significantly more than that in the control group (P < 0.05), but no significant difference was found in the expression of CGRP between 2 groups (P > 0.05); and there was no IB4-binding glycoprotein expression in GAP-43-IR nerve fibers of the intervertebral disc in 2 group. In situ hybridization and RT-PCR detection showed that the positive expression cells ratio of GAP-43 mRNA and the level of GAP-43 mRNA were significantly higher in the experimental group than in the control group at 1 day (P < 0.05), and no significant difference was found at the other time points (P > 0.05). CONCLUSION: Intradiscal inflammatory environment may induce the expression of GAP-43, and potentially promote the nerve fiber ingrowth of rat.

Comparison of E-selectin and the other inflammatory markers in lumbar disc herniation: a new promising therapeutical window for radicular pain.

STUDY DESIGN: Histopathologic and immunohistochemical analysis of the herniated disc specimens obtained from 50 patients who had unilateral persistent radicular pain or unilateral radicular motor paresis. OBJECTIVE: The aim of this study was to investigate the prevalence of inflammatory cells in lumbar disc herniations (LDH) and compare the prevalence of leukocyte adhesion protein "E-selectin" with other inflammatory cells such as T cells, B cells, and macrophages. SUMMARY OF BACKGROUND: Studies on inflammatory cells and biochemical mediators of inflammation have suggested that these factors may play an important role in pathophysiology of radicular pain, and the medical therapy was formed against to block these cells and inflammatory cytokines. METHODS: The herniated disc specimens obtained from 50 patients who had unilateral persistent radicular pain or unilateral radicular motor paresis were microscopically examined after staining with monoclonal antibodies of CD20, CD45, CD68, and E-selectin. Relative risk assessment of the straight-leg raising (SLR) test positivity or negativity with CD20, CD45, CD68, and E-selectin staining was investigated. RESULTS: Our data emphasize that, the cases with positive SLR test had higher rates of immunostaining with E-selectin and CD45. There were no statistically significant relationship between SLR positivity and CD20 and CD68. CONCLUSIONS: We suggest that E-selectin is as valuable as the other well-known inflammatory markers in the pathogenesis of LDH. In our opinion, beside the well-known nonsteroidal anti-inflammatory drugs, antagonists targeting E-selectin can be potentially effective therapeutics for controlling inflammation in LDH.

Complete Freund's adjuvant-induced intervertebral discitis as an animal model for discogenic low back pain.

BACKGROUND: Although numerous animal models for low back pain associated with intervertebral disk (IVD) degeneration have been proposed, insufficient data have been provided to make any conclusions regarding pain. Our aim in this study was to determine the reliability of complete Freund's adjuvant (CFA) injection into the rat spine as an animal model representing human discogenic pain. METHODS: We studied IVD degenerative changes with pain development after a 10-microL CFA injection into the L5-6 IVD of adult rats using behavioral, histologic, and biochemical studies. Serial histologic changes were analyzed to detect degenerative changes. Expression of calcitonin gene-related peptide (CGRP), prostaglandin E (PGE), and inducible nitric oxide synthase (iNOS) were determined using immunohistochemistry or real-time polymerase chain reaction as support data for pain development. In addition, CGRP immunoreactivity (ir) at the IVD was considered indirect evidence of neural ingrowth into the IVD. RESULTS: There was a significant increase of the hindpaw withdrawal response in the CFA group until 7 wk postoperatively (P < 0.05). Histologic analyses revealed progressive degenerative changes of the disks without any damage in adjacent structures, including nerve roots. In the CGRP-ir staining study, the bilateral dorsal horns and IVD had positive ir after intradiscal CFA injection. CGRP mRNA expression was increased in the dorsal root ganglion (DRG) at 2 and 4 wk, whereas PGE and iNOS mRNAs were markedly increased at 2 wk. The increment of CGRP expression was higher in allodynic rats compared with nonallodynic rats. CONCLUSION: Intradiscal CFA injection led to chronic disk degeneration with allodynia, which was suggested by pain behavior and expression of pain-related mediators. The increment of CGRP, PGE, and iNOS also suggest pain-related signal processing between the IVD and the neural pathway in this animal model. This animal model may be useful for future research related to the pathophysiology and development of novel treatment for spine-related pain.

Up-regulation in receptor for advanced glycation end-products in inflammatory circumstances in bovine coccygeal intervertebral disc specimens in vitro.

STUDY DESIGN: This study investigated whether or not the receptor for advanced glycation end-products (RAGE) was up-regulated in inflammatory circumstances and consequently associated with aggrecan content in nucleus pulposus in vitro. OBJECTIVE: To investigate the activation of AGEs-RAGE complex by the irritation of IL-1beta in bovine intervertebral disc (IVD). SUMMARY OF BACKGROUND DATA: Although we have demonstrated that the accumulation of AGEs contributed to disc degeneration in human, it may be that acceleration in the AGEs-RAGE complex might be more important, mediated by expression levels of RAGE that increase in inflammatory mediators including IL-1beta in some tissues. Therefore, we investigated, in this study, the correlation if any between IL-1beta and AGEs-RAGE complex in bovine IVD. METHODS: Samples of bovine coccygeal IVDs were harvested (n = 6). The presence of AGEs and RAGE were identified by immunohistochemistry. Real-time polymerase chain reaction (PCR) was used to quantify the messenger RNA levels of aggrecan after 6 days' stimulation of AGEs. Real-time PCR and immunofluorescein cytochemistry were performed to analyze the expression of RAGE after 2 days' stimulation of IL-1beta. The aggrecan expressions were evaluated by real-time PCR after 2 days' stimulation of combination of AGEs and/or IL-1beta. RESULTS: Immunohistochemical analysis revealed that AGEs and RAGE were localized within the bovine IVDs. AGEs significantly decreased the aggrecan expression in bovine IVD as in human IVD. The RAGE expression was significantly increased by 2 days' stimulation of IL-1beta. The aggrecan expression was decreased by stimulated AGEs and IL-1beta together, although not decreased by stimulated AGEs or IL-1beta separately. CONCLUSION: This is the first report to show the correlation between IL-1beta and AGEs-RAGE complex in IVD. Our results suggested that the increased RAGE expression in inflammatory circumstances and interaction with AGEs are risk factors in decreasing of aggrecan content in nucleus pulposus.

Alteration of disc vacuum contents during prolonged supine positioning: evaluation with MR image.

STUDY DESIGN: Consecutive study. OBJECTIVE: To investigate the changes of disc signal in intradiscal vacuum phenomenon during prolonged supine MR imaging. SUMMARY OF BACKGROUND DATA: Increased T2 signal on MR imaging in intravertebral vacuum cleft during prolonged supine positioning has been described, but no sequential observation of the intervertebral discal signal change in intervertebral disc vacuum. METHODS: Six women and 4 men (age range, 49-89 years; mean, 77 years) with low back pain and more than one level of intradiscal vacuum phenomenon underwent MR examinations at 0 minute, 1 hour, and 2 hours while remaining continuously supine. We recorded the original T2 signal intensity in the vacuum disc and subsequent alterations in the disc signals; they were scored 0 for signal void, 1 for equivocal or mild fluid intensity, or 2 for fluid signal intensity. RESULTS: Vacuum phenomena affected 31 of 60 intervertebral discs (T11-T12 to L5-S1). In 9 patients, the signal intensity of the vacuum content progressively replaced by hyperintense fluid occurred in 25 discs (81%) after prolonged supine positioning, mostly from L3 to S1 levels. The location of fluid signal was central in 20 discs (65%), anterior in 4 (13%), and posterior in 1 (3%). Signal intensity was unchanged in 6 discs (19%). Fluid signal intensity was linear shape in 9 discs (29%), homogeneous in 5 (16%), and mixed in 11 (35%). Overall scores were 8, 26, and 38 at 0, 71, and 161 minutes, respectively. CONCLUSION: After prolonged supine positioning, fluid-like signal could be identified among the intradiscal vacuum by using T2 MR images. This in vivo observation suggested the possible pathway of fluid diffusion from surrounding tissues into degenerative discs.

ISSLS prize winner: repeated disc injury causes persistent inflammation.

STUDY DESIGN: An in vivo rat model of disc degeneration with emphasis on characterizing acute and chronic cytokine production. OBJECTIVE: To compare the morphologic and proinflammatory response between a single and triple-stab injury in attempts to establish mechanisms of chronic disc inflammation. SUMMARY OF BACKGROUND DATA: The features that distinguish physiologic (asymptomatic) from pathologic (symptomatic) degeneration are unclear. Epidemiologic evidence suggests that cumulative damage and elevated disc cytokine levels may be linked to increased low back pain rates. Although acute injury stimulates a healing response that includes transient cytokine production, repetitive damage may be necessary to trigger the persistent inflammation suspected to underlie chronic pain. METHODS: Tail discs were exposed surgically and stabbed with a number 11 blade. During the subsequent acute healing phase, triple-stab discs were percutaneously injured with a 23-gauge needle at day 3 and then again at day 6 after the initial blade incision. Cytokine (IL-1 beta, IL-6, IL-8, and TNF-alpha) production was quantified using enzyme linked immunosorbent assay, and, in addition to MAPK signaling pathways (phosphorylated forms of ERK, JNK, and p38), was localized by immunohistochemistry. Disc architecture was evaluated using histology. RESULTS: Both single-stab and triple-stab discs degenerated with time, yet degeneration was more severe with repeated injury where nuclear proteoglycan was replaced by disorganized collagen. Four days after single-stab, there was a transient peak in IL-1 beta and IL-8 production that was localized to the wound track and associated granulation tissue. By contrast, triple-stab induced an activated annular fibroblast phenotype (p38 positive) that caused a prolonged, diffuse inflammatory response with elevated levels of TNF-alpha, IL-1 beta, and IL-8 up to 28 days after injury. Disc inflammation was accompanied by reactive changes in the adjacent vertebral marrow spaces that was initially lytic at day 4, becoming sclerotic by day 56. CONCLUSION: Our results demonstrate that repeated injury during active healing leads to persistent inflammation and enhanced disc degeneration. These data support the premise that damage accumulation and its associated inflammation may distinguish pathologic from physiologic disc degeneration. In the future, this triple-stab model may be useful to evaluate the efficacy of anti-inflammatory low back pain treatments.

Age-related accumulation of pentosidine in aggrecan and collagen from normal and degenerate human intervertebral discs.

During aging and degeneration, many changes occur in the structure and composition of human cartilaginous tissues, which include the accumulation of the AGE (advanced glycation end-product), pentosidine, in long-lived proteins. In the present study, we investigated the accumulation of pentosidine in constituents of the human IVD (intervertebral disc), i.e. collagen, aggrecan-derived PG (proteoglycan) (A1) and its fractions (A1D1-A1D6) in health and pathology. We found that, after maturity, pentosidine accumulates with age. Over the age range studied, a linear 6-fold increase was observed in pentosidine accumulation for A1 and collagen with respective rates of 0.12 and 0.66 nmol x (g of protein)(-1) x year(-1). Using previously reported protein turnover rate constants (k(T)) obtained from measurements of the D-isomer of aspartic residue in collagen and aggrecan of human IVD, we could calculate the pentosidine formation rate constants (k(F)) for these constituents [Sivan, Tsitron, Wachtel, Roughley, Sakkee, van der Ham, DeGroot, Roberts and Maroudas (2006) J. Biol. Chem. 281, 13009-13014; Tsitron (2006) MSc Thesis, Technion-Israel Institute of Technology, Haifa, Israel]. In spite of the comparable formation rate constants obtained for A1D1 and collagen [1.81+/-0.25 compared with 3.71+/-0.26 micromol of pentosidine x (mol of lysine)(-1) x year(-1) respectively], the higher pentosidine accumulation in collagen is consistent with its slower turnover (0.005 year(-1) compared with 0.134 year(-1) for A1D1). Pentosidine accumulation increased with decreasing buoyant density and decreasing turnover of the proteins from the most glycosaminoglycan-rich PG components (A1D1) to the least (A1D6), with respective k(F) values of 1.81+/-0.25 and 3.18+/-0.37 micromol of pentosidine.(mol of lysine)(-1) x year(-1). We concluded that protein turnover is an important determinant of pentosidine accumulation in aggrecan and collagen of human IVD, as was found for articular cartilage. Correlation of pentosidine accumulation with protein half-life in both normal and degenerate discs further supports this finding.

Aseptic discitis in patients with ankylosing spondylitis: a retrospective study of 14 cases.

OBJECTIVES: To determine whether patients with ankylosing spondylitis (AS) and discitis exhibit specific characteristics as compared to patients who have AS without discitis. METHODS: We retrospectively collected clinical, laboratory, and imaging data from the charts of 79 patients with AS admitted to a rheumatology department. RESULTS: Of the 79 patients, 14 (18%) had discitis that was not due to infection or trauma. Mean age at the diagnosis of AS was 40 years and mean duration of AS at admission was 10 years, with no difference between the two groups. In three patients, discitis was the inaugural manifestation of AS. Two patients had discitis at two levels. The lumbar and thoracolumbar segments were the most common sites of discitis. Symptoms of discitis were present in 10 of the 14 patients. Stage III sacroiliitis was significantly more common in the patients with discitis. None of the patients experienced neurological compromise. CONCLUSION: The frequency of aseptic discitis in patients with AS is probably overestimated as a result of inclusion and exclusion biases. Discitis usually occurs at an advanced stage of AS under the form of an erosive condition related to both mechanical factors and osteoporosis. Inaugural or early discitis can occur, however, as a result of the inflammatory process.

Salmonella spondylodiscitis in patients without sickle cell disease.

The optimal treatment of salmonella spondylodiscitis is controversial. The cases of eight patients who had salmonella spondylitis without sickle cell disease were reviewed. Back pain (100%), fever (75%), and elevated C-reactive protein levels (100%) were common, but gastrointestinal symptoms were not (0%). Six patients had positive blood cultures, and the other two had positive tissue cultures. Group C1 salmonella was the most common serotype. Two patients with coexisting aortic mycotic aneurysms had immediate aneurysm resection. Three others responded favorably to appropriate antibiotics, and three required subsequent surgical reconstruction because of neurologic impairment or osseous instability. Clinical outcomes were significantly better than those of 46 previously reported patients. Salmonella spondylodiscitis usually responds favorably to appropriate antibiotics; consequently, a tissue diagnosis is important. Operative interventions are necessary only for patients with coexisting aneurysms or ongoing osseous instability. A ruptured aortic aneurysm with pseudoaneurysm may mimic a paravertebral abscess, and surgery at the site of an unsuspected aneurysm may precipitate life-threatening hemorrhage. Satisfactory results may be depend on early surgical intervention for a mycotic aneurysm and also are related to host immunity.

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.

Disc inflammation potentially promotes axonal regeneration of dorsal root ganglion neurons innervating lumbar intervertebral disc in rats.

STUDY DESIGN: The expression of growth-associated protein 43 (GAP-43), a marker of axonal growth, in the dorsal root ganglion (DRG) neurons innervating the lumbar intervertebral disc was assessed using the retrograde tracing method and immunohistochemistry. OBJECTIVES: To study whether disc inflammation affects GAP-43 expression in DRG neurons innervating the disc in rats. SUMMARY AND BACKGROUND DATA: Persistent inflammation and nerve ingrowth into the inner layer of degenerated discs can be a cause of discogenic pain. Although the presence of GAP-43-expressing nerve fibers in painful discs has been reported, the expression of GAP-43 in DRG neurons innervating the disc has not been studied. METHODS: Seven days after the application of Fluoro-Gold to the L5-L6 disc, 50 microL of saline (n = 10, control group) or complete Freund's adjuvant (n = 10, inflammatory group) was applied to the disc in rats. Ten days after the Fluoro-Gold application, T13-L5 DRGs were double-stained with GAP-43 and either calcitonin gene-related peptide or isolectin B4 (IB4). RESULTS: The percentage of Fluoro-Gold-labeled neurons that were positive for GAP-43 was significantly higher in the inflammatory group (44%) than in the control group (24%, P < 0.001). In both groups, the majority of GAP-43-positive neurons were small and positive for calcitonin gene-related peptide but not IB4. CONCLUSIONS: The present results suggest that disc inflammation potentially promotes axonal growth of DRG neurons innervating the disc. In light of the strong correlation between the expression of calcitonin gene-related peptide and nerve growth factor receptor, it is most likely that nerve growth factor-sensitive DRG neurons extend their axons following disc inflammation.

Cellular, but not matrix, immunolocalization of SPARC in the human intervertebral disc: decreasing localization with aging and disc degeneration.

STUDY DESIGN: Human intervertebral disc anulus tissue was obtained in a prospective study of immunolocalization of SPARC (secreted protein, acidic and rich in cysteine) (osteonectin). Experimental studies were approved by the authors' Human Subjects Institutional Review Board. Discs were obtained from surgical specimens and from control donors. OBJECTIVES: To determine whether SPARC could be detected in the disc with immunohistochemistry and to determine the incidence of SPARC-positive cells. SUMMARY OF THE BACKGROUND DATA: SPARC is a glycoprotein that has an important role in modulating interactions between cells and matrix. It influences remodeling, collagen fibrillogenesis, metalloproteinase expression, and cytokine expression. Little is known about SPARC in the disc, and one previous study reported the absence of its immunolocalization in fetal and adult disc tissue. METHODS: Eight normal human discs from subjects aged newborn to 10 years, and 11 disc specimens from control donors or surgical patients aged 15to 76 years were examined for immunolocalization of SPARC. Anulus cells were also tested for the presence of SPARC in vitro in monolayer or three-dimensional agarose culture. RESULTS: In discs of subjects aged newborn to 0.19 years, SPARC was present in all cells in the outer anulus, in 76.4% of inner anulus cells, and 76.0% of nucleus cells. Localization was significantly lower in anulus cells of study participants aged 4.7 to 76 years (66.7%, P = 0.04). Anulus cells cultured in agarose or monolayer showed positive localization in all cells. CONCLUSIONS: Findings show decreased presence of SPARC in disc cells of older subjects with disc degeneration and point to the importance of future studies designed to elucidate the unrecognized role of SPARC in disc remodeling, aging, and degeneration.

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.