Lloydine J. Jacobs

Expression and regulation of metalloproteinases and their inhibitors in intervertebral disc aging and degeneration

BACKGROUND CONTEXT Destruction of extracellular matrix (ECM) leads to intervertebral disc degeneration (IDD), which underlies many spine-related disorders. Matrix metalloproteinases (MMPs), and disintegrins and metalloproteinases with thrombospondin motifs (ADAMTSs) are believed to be the major proteolytic enzymes responsible for ECM degradation in the intervertebral disc (IVD). PURPOSE To summarize the current literature on gene expression and regulation of MMPs, ADAMTSs, and tissue inhibitors of metalloproteinases (TIMPs) in IVD aging and IDD. METHODS A comprehensive literature review of gene expression of MMP, ADAMTS, and TIMP in human IDD and reported studies on regulatory factors controlling their expressions and activities in both human and animal model systems. RESULTS Upregulation of specific MMPs (MMP-1, -2, -3, -7, -8, -10, and -13) and ADAMTS (ADAMTS-1, -4, and -15) were reported in human degenerated IVDs. However, it is still unclear from conflicting published studies whether the expression of ADAMTS-5, the predominant aggrecanase, is increased with IDD. Tissue inhibitors of metalloproteinase-3 is downregulated, whereas TIMP-1 is upregulated in human degenerated IVDs relative to nondegenerated IVDs. Numerous studies indicate that the expression levels of MMP and ADAMTS are modulated by a combination of many factors, including mechanical, inflammatory, and oxidative stress, some of which are mediated in part through the p38 mitogen-activated protein kinase pathway. Genetic predisposition also plays an important role in determining gene expression of MMP-1, -2, -3, and -9. CONCLUSIONS Upregulation of MMP and ADAMTS expression and enzymatic activity is implicated in disc ECM destruction, leading to the development of IDD. Future IDD therapeutics depends on identifying specific MMPs and ADAMTSs whose dysregulation result in pathological proteolysis of disc ECM.

An overview of underlying causes and animal models for the study of age-related degenerative disorders of the spine and synovial joints

As human lifespan increases so does the incidence of age‐associated degenerative joint diseases, resulting in significant negative socioeconomic consequences. Osteoarthritis (OA) and intervertebral disc degeneration (IDD) are the most common underlying causes of joint‐related chronic disability and debilitating pain in the elderly. Current treatment methods are generally not effective and involve either symptomatic relief with non‐steroidal anti‐inflammatory drugs and physical therapy or surgery when conservative treatments fail. The limitation in treatment options is due to our incomplete knowledge of the molecular mechanism of degeneration of articular cartilage and disc tissue. Basic understanding of the age‐related changes in joint tissue is thus needed to combat the adverse effects of aging on joint health. Aging is caused at least in part by time‐dependent accumulation of damaged organelles and macromolecules, leading to cell death and senescence and the eventual loss of multipotent stem cells and tissue regenerative capacity. Studies over the past decades have uncovered a number of important molecular and cellular changes in joint tissues with age. However, the precise causes of damage, cellular targets of damage, and cellular responses to damage remain poorly understood. The objectives of this review are to provide an overview of the current knowledge about the sources of endogenous and exogenous damaging agents and how they contribute to age‐dependent degenerative joint disease, and highlight animal models of accelerated aging that could potentially be useful for identifying causes of and therapies for degenerative joint diseases.

Part 2: Quantitative proton T2 and sodium magnetic resonance imaging to assess intervertebral disc degeneration in a rabbit model.

Study Design. Comparison of sodium concentration ([23Na]) and proton T2 relaxation time between normal and degenerated discs in a rabbit model. Objective. The purpose of this article was to evaluate quantitative [23Na] and T2 characteristics of discs associated with degenerative changes. Summary of Background Data. Intervertebral disc degeneration is a common chronic condition that may lead to back pain, limited activity, and disability. Noninvasive imaging method to detect early intervertebral disc degeneration is vital to follow disease progression and guide clinical treatment and management. Methods. Dual-tuned magnetic resonance imaging of rabbit discs was performed using 3T. Thirteen rabbits were included in the study; 6 control rabbits (24 normal discs) and 7 rabbits with annular puncture–induced disc degeneration (9 degenerated discs, 19 intact internal-control discs). Dual-tuned magnetic resonance imaging of discs was performed at baseline and 12-week poststab. [23Na] and T2 were measured and compared among 3 groups of discs. Results. The mean [23Na] were 274.8 ± 40.2 mM for the normal discs, 247.2 ± 27.7 mM for the internal-control discs, and 190.6 ± 19.1 mM for the degenerated discs. The corresponding T2 for 3 groups were 97.1 ± 12.1 ms, 93.7 ± 11.9 ms, and 79.0 ± 9.1 ms, respectively. The [23Na] is highly correlated with the T2 in the degenerated discs (r = 0.90, P < 0.01). The mean percent decreases from the normal to degenerated discs were in 30.6% in [23Na] and 18.6% in T2, whereas those from the internal-control to degenerated discs were 22.9% in [23Na] and 15.6% in T2. Conclusion. Although both [23Na] and T2 changes in discs were associated with the disc-punctured rabbits, greater change in [23Na] is observed at 12-week poststab compared with T2 change. Because T2 and [23Na] reflect different disc properties, performing both imaging under same condition will be helpful in the evaluation of disc degeneration.

Part 1: Dual-tuned proton/sodium magnetic resonance imaging of the lumbar spine in a rabbit model

Study Design. Development of a dual-tuned proton/sodium radiofrequency (RF) coil for magnetic resonance imaging (MRI) of the rabbit spine and quantification of sodium concentration in intervertebral discs. Objective. To develop the dual-tuned proton/sodium MRI of rabbit lumbar spine to investigate proteoglycan matrix content and intervertebral disc degeneration (IDD). Summary of Background Data. IDD is a common chronic condition that may lead to back pain, limited activity, and disability. Early-stage IDD involves the loss of proteoglycan matrix and water content in the disc. Sodium MRI is a promising noninvasive technique for quantitative measurement of proteoglycan changes associated with IDD. The combined structural (proton) and biochemical (sodium) MRI facilitates the investigation of morphological and molecular changes associated with degeneration of discs. Methods. Multichannel dual-tuned proton/sodium transceiver RF coil of the rabbit spine was developed and optimized at 3T human scanner—8 channels allocated for the sodium coil and 4 channels for the proton coil. High-resolution anatomy proton images of the discs were acquired using turbo spin echo and dual echo steady state sequence. Sodium concentration of the discs was quantified from sodium magnetic resonance (MR) images that were calibrated for signal attenuation because of RF field inhomogeneity, sodium MR relaxation times, and disc thickness. Twelve rabbits (∼1-yr old, female, 5.2 ± 0.4 kg) were used for measuring disc sodium concentration. Results. High-resolution in vivo proton and sodium MR images of rabbit discs (⩽2-mm thickness) were successfully obtained using an in-house dual-tuned proton/sodium RF coil at 3T. The total acquisition time for each set of images was approximately 40 minutes. Sodium concentration of normal rabbit lumbar discs was measured at 269.7 ± 6.3 mM, and this measurement was highly reproducible, with 5.3% of coefficient of variation. Conclusion. Sodium concentrations of rabbit lumbar discs were reliably measured using our newly developed dual-tuned multichannel proton/sodium RF coil at 3T.

Reliable Magnetic Resonance Imaging Based Grading System for Cervical Intervertebral Disc Degeneration

Study Design Observational. Purpose To develop a simple and comprehensive grading system for cervical discs that precisely, consistently and meaningfully presents radiologic and morphologic data. Overview of Literature The Thompson grading system is commonly used to classify the severity of degenerative lumbar discs on magnetic resonance imaging (MRI). Inherent differences in the morphological and physiological characteristics of cervical discs have hindered development of precise classification systems. Other grading systems have been developed for degenerating cervical discs, but their versatility and feasibility in the clinical setting is suboptimal. Methods MRIs of 46 human cervical discs were de-identified and displayed in PowerPoint format. Each slide depicted a single disc with a normal (grade 0) disc displayed in the top right corner for reference. The presentation was given to 25 physicians comprising attending spine surgeons, spine fellows, orthopaedic residents, and two attending musculoskeletal radiologists. The grading system included Grade 0 (normal height compared to C2–3, mid cleft still visible), grade 1 (dark disc, normal height), grade 2 (collapsed disc, few osteophytes), and grade 3 (collapsed disc, many osteophytes). The ease of use of the system was gauged in the participants and the interobserver reliability was calculated. Results The intraclass correlation coefficient for interobserver reliability was 0.87, and 0.94 for intraobserver reliability, indicating excellent reliability. Ninety-five percent and 85 percent of the clinicians judged the grading system to be clinically feasible and useful in daily practice, respectively. Conclusions The grading system is easy to use, has excellent reliability, and can be used for precise and consistent clinician communication.

The effects of glucosamine sulfate on intervertebral disc annulus fibrosus cells in vitro.

BACKGROUND CONTEXT Glucosamine has gained widespread use among patients, despite inconclusive efficacy data. Inconsistency in the clinical literature may be related to lack of understanding of the effects of glucosamine on the intervertebral disc, and therefore, improper patient selection. PURPOSE The goal of our study was to investigate the effects of glucosamine on intervertebral disc cells in vitro under the physiological conditions of inflammation and mechanical loading. STUDY DESIGN Controlled in vitro laboratory setting. METHODS Intervertebral disc cells isolated from the rabbit annulus fibrosus were exposed to glucosamine sulfate in the presence and absence of interleukin-1β and tensile strain. Outcome measures included gene expression, measurement of total glycosaminoglycans, new proteoglycan synthesis, prostaglandin E2 production, and matrix metalloproteinase activity. The study was funded by NIH/NCCAM, and the authors have no conflicts of interest. RESULTS Under conditions of inflammatory stimulation alone, glucosamine demonstrated a dose-dependent effect in decreasing inflammatory and catabolic mediators and increasing anabolic genes. However, under conditions of mechanical stimulation, although inflammatory gene expression was decreased, PGE2 was not. In addition, matrix metalloproteinase-3 gene expression was increased and aggrecan expression decreased, both of which would have a detrimental effect on matrix homeostasis. Consistent with this, measurement of total glycosaminoglycans and new proteoglycan synthesis demonstrated detrimental effects of glucosamine under all conditions tested. CONCLUSIONS These results may in part help to explain the conflicting reports of efficacy, as there is biological plausibility for a therapeutic effect under conditions of predominate inflammation but not under conditions where mechanical loading is present or in which matrix synthesis is needed.

Glucosamine supplementation demonstrates a negative effect on intervertebral disc matrix in an animal model of disc degeneration.

Study Design. Laboratory based controlled in vivo study. Objective. To determine the in vivo effects of oral glucosamine sulfate on intervertebral disc degeneration. Summary of Background Data. Although glucosamine has demonstrated beneficial effect in articular cartilage, clinical benefit is uncertain. A Centers for Disease Control report from 2009 reported that many patients are using glucosamine supplementation for low back pain, without significant evidence to support its use. Because disc degeneration is a major contributor of low back pain, we explored the effects of glucosamine on disc matrix homeostasis in an animal model of disc degeneration. Methods. Eighteen skeletally mature New Zealand White rabbits were divided into 4 groups: control, annular puncture, glucosamine, and annular puncture + glucosamine. Glucosamine treated rabbits received daily oral supplementation with 107 mg/d (weight based equivalent to human 1500 mg/d). Annular puncture surgery involved puncturing the annulus fibrosus of 3 lumbar discs with a 16-gauge needle to induce degeneration. Serial magnetic resonance images were obtained at 0, 4, 8, 12, and 20 weeks. Discs were harvested at 20 weeks for determination of glycosaminoglycan content, relative gene expression measured by real time polymerase chain reaction, and histological analyses. Results. The magnetic resonance imaging index and nucleus pulposus area of injured discs of glucosamine treated animals with annular puncture was found to be lower than that of degenerated discs from rabbits not supplemented with glucosamine. Consistent with this, decreased glycosaminoglycan was demonstrated in glucosamine fed animals, as determined by both histological and glycosaminoglycan content. Gene expression was consistent with a detrimental effect on matrix. Conclusion. These data demonstrate that the net effect on matrix in an animal model in vivo, as measured by gene expression, magnetic resonance imaging, histology, and total proteoglycan is antianabolic. This raises concern about this commonly used supplement, and future research is needed to establish the clinical relevance of these findings.

Biomechanical comparison of ponte osteotomy and discectomy.

Study Design. Biomechanical cadaver study. Objective. To evaluate the relative effectiveness of Ponte osteotomies for spinal release in deformity correction. Summary of Background Data. Controversy exists as to the role of Ponte osteotomy in deformity correction surgery. Very little has been written about the biomechanical effects of Ponte osteotomy. Past biomechanical studies have been limited to application of forces through endplates, single functional units, or lack of comparison with anterior release. Methods. Twelve fresh-frozen human full thoracic spinal units were tested for motion in axial rotation, flexion/extension, and lateral bending in a custom-designed robotic environment. Testing was repeated after sequential facetectomy and Ponte osteotomy (6 specimens) and compared with partial and full discectomy (6 specimens). Results. Motion in axial rotation is increased 21% by Ponte osteotomy compared with 35% for full discectomy. Anterior displacement of the spinal column, creating lordosis, was increased 15% by Ponte osteotomy and 40% by full discectomy. Posterior displacement of the spinal column, creating kyphosis, was increased 23% by Ponte osteotomy and 89% by full discectomy. Finally, in coronal force application the Ponte osteotomy had virtually no effect (2%) compared with 40% increased motion by full discectomy. Conclusion. Posterior Ponte osteotomy releases produced more motion than facetectomy alone in axial rotation and sagittal correction maneuvers, but had no effect on coronal correction. Anterior discectomy release destabilized spinal column significantly more than posterior releases in all force applications. Despite ample clinical experience demonstrating the effectiveness of posterior-only surgery, the biomechanical effect of Ponte osteotomies is modest. Level of Evidence: N/A

Identifying Inflammatory Targets for Biologic Therapies for Spine Pain

The costs associated with treating spine‐related conditions are enormous and are trending upward. Current methods employed to treat inflammatory‐mediated pain are targeted at alleviating symptoms, rather than correcting the underlying cause of disease. It is clear that a biochemical basis for inflammatory‐mediated intervertebral disk, facet joint, and nerve pain exists. Biologic therapies that address the underlying cause of pain could potentially decrease the costs associated with treating spine pathology. MMPs, IL‐1, TNF‐ α, IL‐6, NGF, bradykinin, prostaglandins, and nitric oxide are implicated in much of the catabolic effects seen in the pathogenesis of inflammatory‐mediated pain and are good targets for inhibition. The anticatabolic and anabolic effects of TIMPs, BMPs, TGF‐ β, and IGF‐1 are targets already shown to favorably impact disk matrix homeostasis. With rapid advances in biomedical technology, these interventions may be available for clinical use in the near future.

Safety of thromboembolic chemoprophylaxis in spinal trauma patients requiring surgical stabilization.

Study Design. Retrospective review. Objective. To determine the incidence of thromboembolic events, bleeding complications such as epidural hematomas, and wound complications in patients with spinal trauma requiring surgical stabilization. Summary of Background Data. Literature addressing the safety and efficacy of chemoprophylactic agents in postoperative patients with spinal trauma is sparse. As a result, significant variability exists regarding administration of thromboembolic chemoprophylaxis in this population. The risk of bleeding complications is particularly concerning. Methods. Patients with spinal trauma who underwent surgical stabilization in 2009 and 2010 at a single level 1 trauma center were retrospectively reviewed. Exclusion criteria included patients who underwent solely decompressive procedures, noninstrumented fusions, kyphoplasty, or had incomplete medical records. Patients who received chemoprophylaxis were compared with patients who did not. Demographical information and injury data were collected. Primary outcome measures were prevalence of thromboembolic events, epidural hematomas, and persistent wound drainage requiring irrigation and debridement. Results. Two hundred twenty-seven of 373 patients were included (56 in the untreated group, 171 in the treated group). Eight patients in the untreated group (14.3%) and 12 patients in the treated group (7%) developed postoperative thromboembolism (P = 0.096). There was 1 pulmonary embolism in the untreated group (1.8%), and 4 pulmonary embolisms in the treated group (2.3%). Surgical irrigation and debridement for wound drainage was required for 1.8% of patients in the untreated group and for 5.3% of patients in the treated group. No epidural hematomas were noted in either group. The treated group had more spinal levels fused (P = 0.46), higher injury severity scores (0.001), and longer hospitalizations (0.018). Patients who developed postoperative thromboembolism had significantly higher body mass indexes (P = 0.01), injury severity scores (0.001), number of spinal levels fused (P = 0.004), incidence of neurological deficits (0.001), and longer hospitalizations (0.16) compared with those who did not. Conclusion. The use of chemoprophylaxis appears to be safe in at-risk patients in the immediate postoperative period after spinal trauma surgery. No epidural hematomas occurred, and the risk of wound drainage is small. Body mass index, injury severity score, presence of neurological deficits, and number of spinal levels fused should be considered when determining which patients should receive chemoprophylaxis after surgical stabilization. Level of Evidence: 3