Sequential dynamics of monocyte chemotactic protein-1 expression in herniated nucleus pulposus resorption

Discovering Potential Mechanisms of Intervertebral Disc Disease Using Systematic Mendelian Randomization of Human Circulating Immunocytomics

BACKGROUND

Although intervertebral disc degeneration (IVDD) is a critical factor in many spine-related diseases and has an extremely high prevalence in the aging population, the potential pathogenesis remains to be clarified entirely. Immune cells have been found to perform an essential function during the onset and progression of IVDD in recent years. Therefore, we explored the association between immune cell characteristics and IVDD through Mendelian randomization (MR) analysis and further delved into the mediating role of potential metabolites.

METHODS

Based on the MR analysis, the association of 731 immune cell phenotypes and 1400 metabolites on IVDD were assessed. Single nucleotide polymorphisms were closely associated the expression levels of immune cell characteristics and the concentrations of metabolites and have been used as instrumental variables for deducing them as risk factors or protective factors for IVDD. In addition, mediation analyses have been performed to identify potential metabolite mediators between immune cell characteristics and IVDD.

RESULTS

MR analysis identified 27 immune cell phenotypes and 79 metabolites significantly associated with IVDD. In addition, mediation analysis was performed by selecting the immune cell phenotype that most significantly increased the risk of IVDD - CD86 on monocytes. A total of 4 metabolite-mediated mediation relationships were revealed (3 b-hydroxy-5-cholenoic acid, X-22509, N-acetyl-L-glutamine, and N2-acetyl, N6, N6-dimethyllysine).

CONCLUSIONS

The findings of this analysis identified underlying association between immune cell phenotypes, metabolite, and IVDD that may serve as predictive and prognostic clinical biomarkers and benefit IVDD pathogenesis research.

Incidence of Spontaneous Resorption of Lumbar Disc Herniation: A Meta-analysis

STUDY DESIGN

A meta-analysis.

OBJECTIVE

This study aimed to analyze the incidence of spontaneous resorption of lumbar disk herniation (LDH) after conservative treatment.

SUMMARY OF BACKGROUND DATA

The resorption of intervertebral disks has been more frequently reported, but there is a lack of reference to the probability of resorption.

METHODS

We strictly refer to the standard established in the PRISMA (Preferred Reporting Items for a Systematic Review and Meta-analysis) statement, comprehensively searched electronic databases using the terms related to the spontaneous resorption of LDH. Two reviewers independently evaluated the potential studies, extracted, and analyzed the enrolled data.

RESULTS

Thirty-one studies with 2233 patients who received conservative treatment were included for this analysis. We found that the pooled overall incidence of disk resorption was 70.39%, 87.77% for disk sequestration, 66.91% for disk extrusion, 37.53% for disk protrusion, and 13.33% for disk bugle, respectively. The resorption incidence in of 25%≤ reduction of disk herniation (RDH) 50%, RDH≥50%, and RDH=100% were 40.19%, 43.62, and 36.89%. The resorption incidence was 66.98% in Japan, 61.66% in the United States, 83.52% in Korea, 60.68% in China, 78.30% in the UK, 56.70% in Italy, and 83.68% in Turkey, respectively. Subgroup analysis showed that there was no significant difference in resorption incidence among prospective, retrospective studies and randomized controlled trials ( P =0.77), and there was no significant difference in evaluation method among qualitative and quantitative studies ( P =0.05).

CONCLUSIONS

The existing evidence shows that the overall resorption incidence of LDH was 70.39%, the resorption incidence of ruptured LDH is higher than that of contained LDH. There are significant differences in the resorption incidence among countries. The resorption process mainly occurred within 6 months of conservative treatment.

Characteristics and mechanisms of resorption in lumbar disc herniation

Lumbar disc herniation (LDH) can be spontaneously absorbed without surgical treatment. However, the pathogenesis and physiological indications for predicting protrusion reabsorption are still unclear, which prevents clinicians from preferentially choosing conservative treatment options for LDH patients with reabsorption effects. The purpose of this review was to summarize previous reports on LDH reabsorption and to discuss the clinical and imaging features that favor natural absorption. We highlighted the biological mechanisms involved in the phenomenon of LDH reabsorption, including macrophage infiltration, inflammatory responses, matrix remodeling, and neovascularization. In addition, we summarized and discussed potential clinical treatments for promoting reabsorption. Current evidence suggests that macrophage regulation of inflammatory mediators, matrix metalloproteinases, and specific cytokines in intervertebral disc is essential for the spontaneous reabsorption of LDH.

Sequential CCL2 Expression Profile After Disc Injury in Mice

Macrophages produce proinflammatory cytokines in injured intervertebral discs (IVDs). We recently showed that macrophage-derived inflammatory cytokines contribute to the production of pain-related factors. However, the mechanism by which macrophages are recruited to injured IVDs has not been fully clarified. Here, we examined the expression dynamics of the chemokine CCL2 in a mouse IVD injury model and the mechanisms of its regulation. The percentage of macrophages increased from day 1 after injury and persisted up until day 28. At 1 and 3 days after injury, the expression of both Ccl2 messenger RNA (mRNA) and CCL2 protein was elevated in the IVD injury group, after which expression decreased to basal levels. Consistent with the increase in CCL2 expression, Ccr2 and Tnfa expression and various types of macrophages were also immediately elevated following disc injury. Further, tumor necrosis factor-α (TNF-α) stimulated Ccl2 mRNA and CCL2 protein expression in IVD cells in vitro. The expressions of M1 (Cd86 and Nos2) and M2a (Ym1) macrophage markers were all significantly elevated from  day 1 following injury in injured compared with control mice. Meanwhile, the expression of Cd206 (M2a and M2c marker) was significantly elevated on days 3, 7, 14, and 28 following injury. These results suggest that in IVD injury, TNF-α stimulates CCL2, which, in turn, mediates the recruitment of macrophages with the recruited macrophages subsequently differentiating into M1 and M2 subtypes. CCL2 signaling may, therefore, play an important role in IVD pathology via macrophage recruitment. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:895-901, 2020.

The inflammatory response in the regression of lumbar disc herniation

Lumbar disc herniation (LDH) is highly associated with inflammation in the context of low back pain. Currently, inflammation is associated with adverse symptoms related to the stimulation of nerve fibers that may lead to pain. However, inflammation has also been indicated as the main factor responsible for LDH regression. This apparent controversy places inflammation as a good prognostic indicator of spontaneous regression of LDH. This review addresses the molecular and cellular mechanisms involved in LDH regression, including matrix remodeling and neovascularization, in the scope of the clinical decision on conservative versus surgical intervention. Based on the evidence, a special focus on the inflammatory response in the LDH context is given, particularly in the monocyte/macrophage role. The phenomenon of spontaneous regression of LDH, extensively reported in the literature, is therefore analyzed here under the perspective of the modulatory role of inflammation.

Cytokine Involvement in Biological Inflammation Related to Degenerative Disorders of the Intervertebral Disk: A Narrative Review

Objective

The purpose of this narrative literature review is to discuss the literature regarding the potential role that cytokines play in degenerative disk disease.

Methods

The inclusion criteria were studies that used inflammatory mediators in advancing disk disease processes. Research studies were limited to the last 3 decades that had free full-text available online in English. Exclusion criteria were review articles and articles pertaining to temporomandibular joints and other joints of the body other than the intervertebral disk. The following databases were searched: PubMed, EBSCOhost, and Google Scholar through March 13, 2017.

Results

A total of 82 studies were included in this review. The papers were reviewed for complex mechanisms behind the degenerative cascade, emphasizing the role of proinflammatory cytokines, which may be instrumental in processes of inflammation, neurologic pain, and disk degeneration. Interleukin-1β and tumor necrosis factor α were among the more notable cytokines involved in this cascade. Because monocyte chemoattractant protein-1 stimulates and activates macrophages in the event of infiltration, additional proinflammatory cytokines are released to act on molecules to promote blood and nerve ingrowth, resulting in pain signaling and tissue degradation. Excessive inflammation and/or tissue damage initiates a pathologic imbalance between anabolic and catabolic processes.

Conclusions

This literature review describes how inflammatory and biochemical changes may trigger disk degeneration. Proinflammatory cytokines stimulate microvascular blood and nerve ingrowth, resulting in pain signaling and tissue degradation. This may sensitize a person to chemical and/or mechanical stimuli, contributing to severe low back pain.

Increased local expressions of CX3CL1 and CCL2 are related to clinical severity in lumbar disk herniation patients with sciatic pain

Background

Chemokines have been identified to be involved in the modulation of pain through both peripheral and central mechanisms. However, the role of chemokines in lumbar disk herniation (LDH) with sciatic pain remains unknown.

Objective

The current study was performed to explore the expression of two most commonly studied chemokines CX3CL1 and CCL2 and assess their associations with clinical severity in LDH patients with sciatic pain.

Methods

The soft tissues around nerve root (STANR), annulus fibrosus (AF), and nucleus pulposus (NP) biopsies were obtained from 36 LDH patients with chronic sciatic pain and 10 scoliosis patients (painless controls). The serum and local expressions of CX3CL1 and CCL2 were determined using enzyme-linked immunosorbent assay and Western blot analysis, respectively. The visual analog scale (VAS) scores for low back pain and lower extremity pain and Japanese Orthopaedic Association (JOA) scores were recorded on the day of hospital admission to evaluate the clinical severity. LDH patients with sciatic pain were divided into severe pain (SP) group (VAS ≥7; n=18) and mild-to-moderate pain (M-MP) group (VAS <7; n=18) for lower extremity pain.

Results

Local expressions instead of CX3CL1 and CCL2 in STANR, AF, and NP were significantly higher in the SP group than in M-MP compared with scoliosis painless group. Expressions of both CX3CL1 and CCL2 in STANR and AF were positively correlated with VAS scores for lower extremity and for low back pain, respectively. In addition, CX3CL1 and CCL2 expressions in STANR were negatively associated with JOA scores. There were no significant differences of serum CX3CL1 and CCL2 levels among SP group, M-MP group, and scoliosis painless group.

Conclusion

Both CX3CL1 and CCL2 may play important roles in maintaining pain in LDH patients. Local blockade of CX3CL1 and CCL2 in LDH patients with persistent pain deserves further intensive study.

Prolyl-4-hydroxylase domain protein 2 controls NF-κB/p65 transactivation and enhances the catabolic effects of inflammatory cytokines on cells of the nucleus pulposus

Prolyl-4-hydroxylase (PHD) proteins are key in sensing tissue hypoxia. In nucleus pulposus (NP) cells, our previous work demonstrated that PHD isoforms have a differential contribution in controlling hypoxia-inducible factor (HIF)-α degradation and activity. Recently we have shown that a regulatory relationship exists between PHD3 and inflammatory cytokines in NP cells. With respect to PHD2, the most abundant PHD isoform in NP cells, very little is known concerning its function and regulation under inflammatory conditions that characterize intervertebral disc degeneration. Here, we show that PHD2 is a potent regulator of the catabolic activities of TNF-α; silencing of PHD2 significantly decreased TNF-α-induced expression of catabolic markers including SDC4, MMP-3, MMP-13, and ADAMTS5, as well as several inflammatory cytokines and chemokines, while partially restoring aggrecan and collagen II expression. Use of NF-κB reporters with ShPHD2, SiHIF-1α, as well as p65(-/-), PHD2(-/-), and PHD3(-/-) cells, shows that PHD2 serves as a co-activator of NF-κB/p65 signaling in HIF-1-independent fashion. Immunoprecipitation of endogenous and exogenously expressed tagged proteins, as well as fluorescence microscopy, indicates that following TNF-α treatment, PHD2 interacts and co-localizes with p65. Conversely, loss of function experiments using lentivirally delivered Sh-p65, Sh-IKKβ, and NF-κB inhibitor confirmed that cytokine-dependent PHD2 expression in NP cells requires NF-κB signaling. These findings clearly demonstrate that PHD2 forms a regulatory circuit with TNF-α via NF-κB and thereby plays an important role in enhancing activity of this cytokine. We propose that during disc degeneration PHD2 may offer a therapeutic target to mitigate the deleterious actions of TNF-α, a key proinflammatory cytokine.

Dominance of chemokine ligand 2 and matrix metalloproteinase-2 and -9 and suppression of pro-inflammatory cytokines in the epidural compartment after intervertebral disc extrusion in a canine model

BACKGROUND CONTEXT

In canine intervertebral disc (IVD) disease, a useful animal model, only little is known about the inflammatory response in the epidural space.

PURPOSE

To determine messenger RNA (mRNA) expressions of selected cytokines, chemokines, and matrix metalloproteinases (MMPs) qualitatively and semiquantitatively over the course of the disease and to correlate results to neurologic status and outcome.

STUDY DESIGN/SETTING

Prospective study using extruded IVD material of dogs with thoracolumbar IVD extrusion.

PATIENT SAMPLE

Seventy affected and 13 control (24 samples) dogs.

OUTCOME MEASURES

Duration of neurologic signs, pretreatment, neurologic grade, severity of pain, and outcome were recorded. After diagnostic imaging, decompressive surgery was performed.

METHODS

Messenger RNA expressions of interleukin (IL)-1β, IL-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor (TNF), interferon (IFN)γ, MMP-2, MMP-9, chemokine ligand (CCL)2, CCL3, and three housekeeping genes was determined in the collected epidural material by Panomics 2.0 QuantiGene Plex technology. Relative mRNA expression and fold changes were calculated. Relative mRNA expression was correlated statistically to clinical parameters.

RESULTS

Fold changes of TNF, IL-1β, IL-2, IL-4, IL-6, IL-10, IFNγ, and CCL3 were clearly downregulated in all stages of the disease. MMP-9 was downregulated in the acute stage and upregulated in the subacute and chronic phase. Interleukin-8 was upregulated in acute cases. MMP-2 showed mild and CCL2 strong upregulation over the whole course of the disease. In dogs with severe pain, CCL3 and IFNγ were significantly higher compared with dogs without pain (p=.017/.020). Dogs pretreated with nonsteroidal anti-inflammatory drugs revealed significantly lower mRNA expression of IL-8 (p=.017).

CONCLUSIONS

The high CCL2 levels and upregulated MMPs combined with downregulated T-cell cytokines and suppressed pro-inflammatory genes in extruded canine disc material indicate that the epidural reaction is dominated by infiltrating monocytes differentiating into macrophages with tissue remodeling functions. These results will help to understand the pathogenic processes representing the basis for novel therapeutic approaches. The canine IVD disease model will be rewarding in this process.

Translational research of herniated discs: current status of diagnosis and treatment

Lumbar herniated discs commonly occur in patients 20-40 years of age, and result in acute symptoms of shooting and intractable pain in the low back and/or lower extremities. However, the prognosis of these patients is considered to be very good. Moreover, 70% of these patients have been reported to be free from sciatica at approximately 6 months after the first onset. Magnetic resonance imaging (MRI) studies have described the spontaneous resorption process of herniated discs, which is a major cause of the reduction of symptoms in patients. New advancements in MRI have recently been developed that have facilitated the examination of nerve tract fibers and identification of symptomatic nerve tissue. Furthermore, the mechanism underlying the resorption process of a herniated disc has been determined. Inflammatory cytokines such as TNF (tumor necrosis factor)-α, angiogenic factors such as vascular endothelial growth factor, and enzymes such as matrix metalloproteinases are intricately related to each other. In our previous studies, matrix metalloproteinase-7 (MMP-7) has been shown to play a crucial role in the initiation of herniated disc resorption. Therefore, we developed recombinant human MMP-7 for intradiscal therapy through an industry-university joint research program. We have already performed in vitro and in vivo experiments to confirm its efficacy; this therapy avoids the side effects associated with surgery, such as nerve tissue damage. Moreover, the phase 1/2 studies of recombinant human (rh) MMP-7 are currently ongoing in the United States, and careful monitoring is required for these clinical trials. In conclusion, patients with lumbar herniated discs may benefit from the development of a less invasive treatment for disc herniation, which can be applied even immediately after the onset of disease symptoms.

Age-related expression of MCP-1 and MMP-3 in mouse intervertebral disc in relation to TWEAK and TNF-α stimulation

This study was undertaken to investigate the age-related differences of monocyte chemotactic protein-1 (MCP-1) and matrix metalloproteinase-3 (MMP-3) expression in mouse intervertebral disc (IVD) and to determine whether MMP-3 plays a role in disc degeneration. Expression of MCP-1 and MMP-3 mRNA in mouse IVD was assessed by quantitative PCR. The ability of MCP-1 and MMP-3 expression in IVD to respond to TNF-α or TWEAK stimulation was examined by quantitative PCR, WB, ELISA, and immunohistochemistry. IVD derived from MMP-3-deficient and wild-type mice were compared using Safranin-O staining and immunohistochemistry. mRNA levels of MCP-1 and MMP-3 in IVD significantly diminished and the ability of MCP-1 or MMP-3 expression to respond to TNF-α or TWEAK stimulation was significantly reduced as age increased. IVD derived from 64-week-old wild-type mice showed clearly diffuse proteoglycan loss by Safranin-O staining and immunohistochemistry compared with younger mice. However, no loss of proteoglycan and typeII collagen were observed in IVD derived from 64-week-old MMP-3-deficient mice. MCP-1 and MMP-3 expression in mouse IVD showed age-related decreases. The response to inflammation in IVD also displayed age-related changes. Therefore, disc degeneration may vary with the patients' age and targeting MMP-3 may be a possible future therapeutic strategy for disc degeneration.

Clinical and magnetic resonance imaging features of canine compressive cervical myelopathy with suspected hydrated nucleus pulposus extrusion

OBJECTIVE

To describe clinical and magnetic resonance imaging features in dogs with compressive cervical myelopathy due to acute suspected hydrated nucleus pulposus extrusion.

DESIGN

Retrospective case series.

ANIMALS

Ten dogs with compressive cervical myelopathy caused by acute suspected hydrated nucleus pulposus extrusion.

MATERIALS AND METHODS

Medical records and magnetic resonance images of dogs evaluated from 2005 through 2010 were reviewed. The inclusion criteria were clinical signs compatible with cervical myelopathy, magnetic resonance imaging of the spine performed within 48 hours after onset, magnetic resonance imaging findings consistent with compressive suspected hydrated nucleus pulposus extrusion, complete medical records and follow-up information.

RESULTS

Six dogs were presented with acute onset tetraplegia and four dogs with acute onset of nonambulatory tetraparesis. Compromised respiratory function was present in three dogs. Compressive suspected hydrated nucleus pulposus extrusion was found on magnetic resonance imaging at the C4-C5 (n=6), C3-C4 (n=3) and C5-C6 (n=1) intervertebral disc spaces. Seven dogs underwent surgical treatment and three dogs were treated conservatively. All dogs except one regained ambulatory status within two weeks after the onset, and had a favourable outcome.

CLINICAL SIGNIFICANCE

Compressive myelopathy caused by acute suspected hydrated nucleus pulposus extrusion has not been reported previously and, even though neurological deficits can be severe on presentation, outcome is favourable.

Mechanism of signal transduction in tumor necrosis factor-like weak inducer of apoptosis-induced matrix degradation by MMP-3 upregulation in disc tissues

STUDY DESIGN

Molecular biologic and immuno-histologic analyses using in vitro murine intervertebral disc tissue culture.

OBJECTIVE

To investigate the role of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) in matrix metalloproteinase 3 (MMP-3) pathway induction, and the effect of TWEAK to induce other cytokines or angiogenesis factors in disc tissues.

SUMMARY OF BACKGROUND DATA

We previously demonstrated that TWEAK and its receptor Fn14 were expressed in murine disc tissues. TWEAK induced MMP-3 upregulation and aggrecan downregulation in disc tissues.

METHODS

Enzyme-Linked ImmunoSorbent Assay (ELISA), western blot, and immuno-histologic analyses were used to assess the role of TWEAK-induced MMP-3, using murine disc tissue culture.

RESULTS

TWEAK induced disc cells to generate MMP-3 as did TNF-alpha and IL-1beta. MMP-3 activity was detectable in murine disc cells. MMP-3 induction was markedly inhibited with a c-Jun N-terminal kinase (JNK) inhibitor. Phosphorylation of JNK was also confirmed. Introduction of TWEAK resulted in the degradation of disc matrix in organ disc culture, whereas proteoglycan degradation was markedly abrogated in the presence of an MMP-3 specific inhibitor or a JNK inhibitor. In addition, TWEAK also induced monocyte chemotactic protein (MCP)-1 via the NF-kappaB pathway, as phosphorylation of NF-kappaB was confirmed by western blotting.

CONCLUSION

TWEAK plays an important role in MMP-3 induction in murine disc cells via JNK that results in degradation of disc matrix. TWEAK also induces MCP-1, which belongs to the chemokine family that recruits inflammatory cells via the NF-kappaB pathway.

1,25(OH)2-vitamin D3 inhibits proliferation and decreases production of monocyte chemoattractant protein-1, thrombopoietin, VEGF, and angiogenin by human annulus cells in vitro

STUDY DESIGN

Human lumbar anulus tissue and cultured human lumbar anulus cells were used in retrospective studies of the immunocytochemical localization of the vitamin D receptor (VDR) in disc tissue, and of the in vitro effects of the active metabolite of vitamin D, 1,25(OH)2D3, on anulus cell proliferation, cytokine, and proteoglycan (PG) production. 24,25-D3 was also analyzed. Studies were approved by the authors' Human Subjects Institutional Review Board. Discs were obtained from surgical specimens and from control donors.

OBJECTIVES

To determine if human anulus cells express the VDR in vivo, and to test the effect of in vitro exposure to 1,25(OH)2D3 and 24,25-D3 on anulus cell proteoglycan and cytokine production in 3-dimensional culture.

SUMMARY OF BACKGROUND DATA

Intragenic polymorphisms in the VDR gene have been associated with disc degeneration. 1,25(OH)2D3 has well-recognized effects on calcium homeostasis and bone mineralization, and is a negative growth regulator of a variety of normal and tumor cells. Its effects on human disc cells, however, are unexplored.

METHODS

Immunocytochemistry was performed on human lumbar disc anulus tissue from 19 subjects; human disc cells were cultured to test the effect of 1,25(OH)2D3 on proliferation of anulus cells from 5 subjects. A paired experimental design was used to determine proteoglycan production in control or 1,25(OH)2D3-treated cells, or in control or 24,25-D3-treated cells using the dimethylmethylene blue assay. A paired experimental design was also used to identify differences in cytokine production in conditioned media from control or 1,25(OH)2D3-treated cells, or in control or 24,25-D3-treated cells using ELISA assays.

RESULTS

Immunocytochemistry documented expression of the VDR in anulus cells. Young donor discs (aged newborn, 15 years) showed positive localization in all cells of the outer anulus, and some inner anulus cells. In adults (mean age, 38.9 years), some, but not all anulus cells, showed positive localization. Exposure to 10M 1,25(OH)2D3 in monolayer significantly reduced cell proliferation in vitro (P = 0.03). PG production in 3-dimensional was unchanged from control in both 1,25(OH)2D3- and 24,25-D3-treated cells. Cytokine production differed, however. 1,25(OH)2D3-treated cells showed significantly decreased production of vascular endothelial growth factor (VEGF) (P = 0.01), monocyte chemoattractant protein-1 (MCP-1) (P = 0.0006), angiogenin (P = 0.002), and thrombopoietin (P = 0.03) compared with controls. 24,25-D3-treated cells showed significantly elevated vascular endothelial growth factor-D (P = 0.01), beta-fibroblast growth factor (0.03), and significantly decreased interleukin-8, interferon-gamma, leptin, MCP-1, and TIMP-2 (tissue inhibitor of metalloproteinases-2) compared with controls (P <or= 0.01).

CONCLUSION

Data suggest that 1,25(OH)2D3 and 24,25-D3 may play roles as regulators of cell proliferation and production of specific cytokines in the lumbar anulus.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited

OBJECTIVE

The objectives of this white paper are to review and summarize the basic science literature relevant to spinal fixation (subluxation) and spinal adjusting procedures and to make specific recommendations for future research.

METHODS

PubMed, CINAHL, ICL, OSTMED, and MANTIS databases were searched by a multidisciplinary team for reports of basic science research (since 1995) related to spinal fixation (subluxation) and spinal adjusting (spinal manipulation). In addition, hand searches of the reference sections of studies judged to be important by the authors were also obtained. Each author used key words they determined to be most important to their field in designing their individual search strategy. Both animal and human studies were included in the literature searches, summaries, and recommendations for future research produced in this project.

DISCUSSION

The following topic areas were identified: anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system. A relevant summary of each topic area and specific recommendations for future research in each area were the primary objectives of this project.

CONCLUSIONS

The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.

In vitro evaluation of low-intensity pulsed ultrasound in herniated disc resorption

Herniated disc (HD) is often resolved spontaneously without surgical intervention. HD resorption (HDR) is associated with abundant vascularization and infiltration of macrophages (Mphi) into the intervertebral disc (ID), as well as with high levels of matrix metalloproteinases (MMPs). Low-intensity pulsed ultrasound (LIPUS) accelerates bone fracture healing in clinical studies, and angiogenic factors are involved in the mechanism of action. In the present study, we examined the effects of LIPUS on HDR in a rat in vitro HD model. HDR was enhanced by LIPUS as measured by the change in the wet weight of the cultured ID. The secretion of tumor necrosis factor-alpha (TNF-alpha) and macrophage chemoattractant protein-1 (MCP-1) from Mphi into the culture medium was stimulated by LIPUS. LIPUS also enhanced matrix metalloproteinase-3 (MMP-3) maturation. Moreover, many apoptotic cell death were observed in the HDR groups with LIPUS exposure. These results suggest that LIPUS enhanced the HDR via MMP-3 activation through TNF-alpha and MCP-1 pathways. Although animal studies and clinical trial are needed to understand the LIPUS effects on HDR, LIPUS treatment might be an effective treatment for accelerating HDR.

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.

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.

Expression of monocyte chemoattractant protein-1 in primary cultures of rabbit intervertebral disc cells

Macrophages are considered essential for herniated disc resorption, and chemokines may play a role in their recruitment. Here we demonstrate that intervertebral disc cells are capable of producing monocyte chemoattractant protein-1 (MCP-1), a CC chemokine that is chemotactic for macrophages. Nucleus pulposus cells and anulus fibrosus cells were harvested from intervertebral discs of healthy rabbits, and the cells were stimulated with either interleukin (IL)-1beta or tumor necrosis factor (TNF)alpha. Reverse transcriptase polymerase chain reaction demonstrated that IL-1beta and TNFalpha induced mRNA expression for MCP-1 in nucleus pulposus and anulus fibrosus cells. Protein concentrations of MCP-1 in the culture supernatants were quantitated by fluoroimmunoassay, which showed that nucleus pulposus and anulus fibrosus cells dose- and time-dependently produced MCP-1 after IL-1beta- and TNFalpha-stimulation, an event that was completely abrogated by IL-1 receptor antagonist and anti-TNFalpha monoclonal antibody, respectively. Nucleus pulposus cells produced significantly higher levels of MCP-1 than did anulus fibrosus cells. Immunohistochemically, the intensity of MCP-1 positive cells in nucleus pulposus cells was stronger than that in anulus fibrosus cells. Altogether, our data clearly demonstrated the production of MCP-1 in intervertebral disc cells, suggesting the possible involvement of disc cells in an early stage of macrophage infiltration.

Gadolinium diethylenetriaminepentaacetic acid enhancement in magnetic resonance imaging in relation to symptoms and signs among sciatic patients: a cross-sectional study

STUDY DESIGN

A cross-sectional descriptive study.

OBJECTIVES

Gadolinium enhancement in lumbar magnetic resonance imaging is not used routinely. The current study explored the possible intercorrelations of enhancement patterns with clinical symptoms and signs.

SUMMARY OF BACKGROUND DATA

Rim enhancement has been reported to occur in the periphery of disc herniations, and it is thought to represent neovascularization. To the authors' knowledge, the significance of the enhancement in relation to clinical symptoms has not been studied.

METHODS

Magnetic resonance imaging of the lumbar spine with intravenous gadolinium diethylenetriaminepentaacetic acid was performed in each patient. Various contrast enhancement parameters and volume of herniation were evaluated, and their correlations with clinical signs and symptoms (straight leg raising, motor defect, Achilles reflex, leg and back pain, disability) were analyzed.

RESULTS

The extent of rim enhancement correlated highly significantly with the degree of disc displacement, being most pronounced in the case of sequesters. The duration of sciatic symptoms correlated negatively with enhancement. The clinical symptoms did not correlate significantly with the different enhancement parameters or disc herniation volume. Straight leg raising correlated only slightly with the extent of rim enhancement (P = 0.04) when bulges were excluded. Achilles reflex abnormality correlated significantly with all enhancement parameters for lesions at L5-S1. In the final stepwise logistic regression model, contrast enhancement extent correlated most significantly with abnormal Achilles reflex (P = 0.0002).

CONCLUSIONS

Although rim enhancement of disc herniation is thought to represent a beneficial phagocytotic phenomenon, it may also have a harmful effect on the adjacent nerve root.

Cost effectiveness of periradicular infiltration for sciatica: subgroup analysis of a randomized controlled trial

STUDY DESIGN

A subgroup analysis of a prospective, randomized controlled trial was performed.

OBJECTIVE

To describe the cost effectiveness of periradicular infiltration with steroid in subgroups of patients with sciatica.

SUMMARY OF BACKGROUND DATA

A recent trial on periradicular infiltration indicated that a methylprednisolone-bupivacaine combination had a short-term effect, as compared with that of saline. This report describes the efficacy and cost effectiveness of steroid in subgroups of patients with sciatic.

METHODS

This study involved 160 patients with unilateral sciatica. Outcome assessments were leg pain (100-mm visual analog scale), disability on the Oswestry Low Back Disability Questionnaire, and the Nottingham Health Profile. Data on medical costs and sick leaves also were gathered. Patients were randomized for periradicular infiltration with either methylprednisolone-bupivacaine or saline. The adjusted between-group treatment differences at each follow-up assessment, the number of patients free of leg pain (responders, cutoff 75%), and efficacy by the area-under-the-curve method were calculated. For the cost-effectiveness estimate, the total costs were divided by the number of responders. The rate of operations in different subgroups was evaluated by Kaplan-Meier analysis.

RESULTS

In the case of contained herniations, the steroid injection produced significant treatment effects and short-term efficacy in leg pain and in Nottingham Health Profile emotional reactions. For symptomatic lesions at L3-L4-L5, steroid was superior to saline for leg pain, disability, and straight leg raising in the short term. By 1 year, steroid seemed to have prevented operations for contained herniations, costing $12,666 less per responder in the steroid group (P < 0.01). For extrusions, steroid seemed to increase the operation rate, and the steroid infiltration was more expensive, costing $4445 per responder (P < 0.01).

CONCLUSIONS

In addition to short-term effectiveness for contained herniations and lesions at L3-L4-L5, steroid treatment also prevented surgery for contained herniations. However, steroid was countereffective for extrusions. The results of the subgroup analyses call for a verification study.

Intervertebral disk degeneration and herniation: the role of metalloproteinases and cytokines

This article reviews the role of metabolic factors, including metalloproteinases and cytokines, in the occurrence of degenerative disk disease and disk herniation. Given that mechanical factors alone cannot cause disk degeneration, studies must explore metabolic, genetic, nutritional, and age-related factors. Zinc metalloproteinases exert particularly important effects, not only directly, but also indirectly through promotion of neovascularization. The production of these enzymes is dependent on a number of cytokines and on the cell changes they induce. This complex effect acts both on disk matrix degeneration and on the pain generated by contact between the protruding disk and the nerve roots. However, it can have a favorable effect by promoting resorption of the herniated disk. Available data on the role for mechanical factors on the disk chondrocyte metabolism and on metalloproteinase production show that mechanical and metabolic factors interact closely to produce disk disorders.

Periradicular infiltration for sciatica: a randomized controlled trial

STUDY DESIGN

A randomized, double-blind trial was conducted.

OBJECTIVES

To test the efficacy of periradicular corticosteroid injection for sciatica.

SUMMARY OF BACKGROUND DATA

The efficacy of epidural corticosteroids for sciatica is controversial. Periradicular infiltration is a targeted technique, but there are no randomized controlled trials of its efficacy.

METHODS

In this study 160 consecutive, eligible patients with sciatica who had unilateral symptoms of 1 to 6 months duration, and who never underwent surgery were randomized for double-blind injection with methylprednisolone bupivacaine combination or saline. Objective and self-reported outcome parameters and costs were recorded at baseline, at 2 and 4 weeks, at 3 and 6 months, and at 1 year.

RESULTS

Recovery was better in the steroid group at 2 weeks for leg pain (P = 0.02), straight leg raising (P = 0.03), lumbar flexion (P = 0.05), and patient satisfaction (P = 0.03). Back pain was significantly lower in the saline group at 3 and 6 months (P = 0.03 and 0.002, respectively), and leg pain at 6 months (13.5, P = 0.02). Sick leaves and medical costs were similar for both treatments, except for cost of therapy visits and drugs at 4 weeks, which were in favor of the steroid injection (P = 0.05 and 0.005, respectively). By 1 year, 18 patients in the steroid group and 15 in the saline group underwent surgery.

CONCLUSIONS

Improvement during the follow-up period was found in both the methylprednisolone and saline groups. The combination of methylprednisolone and bupivacaine seems to have a short-term effect, but at 3 and 6 months, the steroid group seems to experience a "rebound" phenomenon.