Extracellular matrix synthesis and ultrastructural changes of degenerative disc cells transfected by Ad/CMV-hTGF-beta 1

OBJECTIVE

To determine whether the synthesis of proteoglycan, collagen and associated ultrastructure are related to the adenovirus-mediated gene transferred to adult degenerative cells.

METHODS

Adenovirus/cytomegalovirus human transforming growth factor-beta 1 (Ad/CMV-hTGF-beta 1) was used to transfect degenerative cells. Antonopulos method, Miamine method and transmission electron microscopy were conducted to study the synthesis of proteoglycan, collagen, and ultrastructure, respectively. Cell cultures were established from the nucleus pulpous and annulus fibrosus tissues, which were taken from surgery.

RESULTS

Nucleus pulpous and annulus fibrosus cells were efficiently transduced by the adenoviral vector carrying hTGF-beta 1 gene. The synthesis of proteoglycan and collagen increased compared with the control group (P < 0.05). The metabolism of cells was slightly improved. No significant toxic effects were found.

CONCLUSIONS

Expression of hTGF-beta 1 gene is efficient to accelerates proteoglycan synthesis and thus accelerates the improvement of collagen. The function and structure of degenerative cells are improved. Ad/CMV-hTGF-beta 1 may be suitable for treating disc degeneration.

Diagnostic value of image-guided needle aspiration cytology in the assessment of vertebral and intervertebral lesions

The aim of this study was to evaluate the diagnostic value of the noninvasive method of image-guided needle aspiration cytology (NAC) in the assessment of radiologically detected vertebral and intervertebral space-occupying lesions. NAC was performed under computed tomographic (CT) guidance on 70 patients suspected of having a vertebral or intervertebral lesion. Cytologic examination was performed on site after staining smears with the Papanicoloau method. In addition, air-dried smears, fixed smears, filter preparations from needle washings, and cell blocks were studied. The NAC diagnosis was supported by examining cell blocks, which showed the reliability of histologic architecture; further support was obtained with a tissue biopsy in some cases. Additionally, immunoperoxidase and/or histochemical studies were done. Ten cases were diagnosed as inflammatory/degenerative lesions, and in 2 cases a diagnosis of neurofibroma was made. Twelve cases consisted of normal cellular elements, 7 cases were unsatisfactory/inadequate for diagnosis, and 4 cases were suspicious for malignancy. In 32 cases, a variety of metastatic tumors were diagnosed, while in 3 cases, a diagnosis of chordoma was made. Based on our study, we feel that NAC, as a first line of investigation, is not only useful in the diagnosis of space-occupying lesions of vertebral and intervertebral regions, but can also help in deciding on appropriate management. Also, histologic architecture from cell blocks can be correlated with cytology, and such material can be used for histochemical and immunomarker studies.

2002 SSE Award Competition in Basic Science: expression of major matrix metalloproteinases is associated with intervertebral disc degradation and resorption

During the process of degeneration, the intervertebral disc (IVD) shows a progressive and significant reduction in height due to tissue resorption. Intradiscal clefts and tears are major hallmarks of disc degeneration. Matrix-degrading enzymes such as matrix metalloproteinases (MMPs) are assumed to play a pivotal role in disc tissue degradation and resorption. The objective of this study was therefore to investigate the potential role of MMPs in extracellular matrix degradation leading to disc degeneration. This study was conducted on 30 formalin-fixed and EDTA-decalcified complete cross-sections of lumbar IVDs from cadavers of individuals aged between 0 and 86 years. Tissue sections were used for the immunolocalization of MMPs-1, -2, -3 and -9. The number of labeled cells was assessed by morphometric analyses, and was statistically correlated with the formation of clefts and tears, cellular proliferation, granular matrix changes and mucous degeneration. Furthermore, 30 disc specimens obtained during spinal surgery were used for in situ hybridization of MMP-2 and -3-mRNA. In addition, the enzymatic gelatinolytic activity was determined by in situ zymography in autopsy material. Immunohistochemistry showed the intradiscal expression of all four MMPs, which was confirmed by in situ hybridization, providing clear evidence for the synthesis of the enzymes within nucleus pulposus and annulus fibrosus cells. Gelatinolytic enzymatic activity was verified by in situ zymography. IVDs from infants and young adolescents remained almost completely unlabeled for all MMPs tested, while more MMPs-1 and -3 were seen in disc cells of younger adults than in those of a more advanced age; MMP-2 remained unchanged over the adult age periods, and MMP-9 was expressed in only relatively few cells. This pattern significantly correlated with the occurrence of clefts and tears. This correlation was strongest for MMP-1 ( P<0.0001), MMP-2 ( P<0.0017) and MMP-3 ( P<0.0005) in the nucleus, and MMP-1 ( P<0.0001) and MMP-2 ( P<0.038) in the annulus. In parallel, the proliferation of disc cells and matrix degeneration (granular changes and mucous degeneration) were related to MMP expression. Likewise, enzymatic activity was seen in association with cleft formation. Our data suggest that major MMPs play an important role in the degradation of the IVD. This is evidenced by the high correlation of MMP expression with the formation of clefts and tears. These findings implicate a leading function for MMPs in IVD degeneration resulting in the loss of normal disc function, eventually leading to low-back pain.

Expression of chondrocyte markers by cells of normal and degenerate intervertebral discs

AIMS

To investigate the phenotype of cells in normal and degenerate intervertebral discs by studying the expression of molecules characteristic of chondrocytes in situ.

METHODS

Human intervertebral discs taken at surgery were graded histologically, and classified on this basis as normal or degenerate. Eighteen of each type were selected, and in situ hybridisation was performed for the chondrocytic markers Sox9 and collagen II using (35)S labelled cDNA probes. Aggrecan was located by immunohistochemistry, using the monoclonal antibody HAG7E1, and visualised with an avidin-biotin peroxidase system.

RESULTS

In the normal discs, strong signals for Sox9 and collagen II mRNA, and strong staining for the aggrecan protein were seen for the cells of the nucleus pulposus (NP), but reactions were weak or absent over the cells of the annulus fibrosus (AF). In degenerate discs, the Sox9 and collagen II mRNA signals remained visible over the cells of the NP and were again absent in the AF. Aggrecan staining was not visible in the NP cells, and was again absent in the AF.

CONCLUSIONS

Cells of the normal NP showed expression of all three markers, clearly indicating a chondrocytic phenotype. In degeneration, there was evidence of a loss of aggrecan synthesis, which may contribute to the pathogenesis of disc degeneration. AF cells showed no evidence of a chondrocytic phenotype in either normal or degenerate discs.

Current understanding of cellular and molecular events in intervertebral disc degeneration: implications for therapy

Until recently, material removed from the intervertebral disc (IVD) at surgery consisted either of 'loose bodies' from the centre of the IVD or discal tissue displaced (prolapsed) into the intervertebral root or spinal canals. This material is best regarded as a by-product of disc degeneration and therefore not representative of the disease process itself. Recent advances in surgical techniques, particularly anterior fusion, in which large segments of the anterior part of the IVD are excised with the anatomical relationships between different components intact, have generated material that can be investigated with modern molecular and cell biological techniques. This is an important area of study because degeneration of the lumbar IVDs is associated, perhaps causally, with low back pain, one of the most common and debilitating conditions in the West. 'Degeneration' carries implications of inevitable progression of wear-and-tear associated conditions. Modern research on human IVD tissue has shown that this is far from the case and that disruption of the micro-anatomy described as degeneration is an active process, regulated by locally produced molecules. The exciting consequence of this observation is the possibility of being able to inhibit or even reverse the processes of degeneration using targeted therapy.

A study on the influence of calcified intervertebral disk and aorta in determining bone mineral density

This study utilized dual-energy X-ray absorptiometry (DXA) to determine the association that age-related calcinosis of the aorta and intervertebral disks have in determining bone mineral density (BMD). Eight cadavers were chosen at random and were scanned with DXA before and after the removal of the aorta and intervertebral disks. Our results showed that the removal of sclerotic aortas decreased the vertebral BMD an average of 4.64% and the removal of two lumbar intervertebral disks further decreased BMD an average of 11.93%. These results were deemed significant at the 0.01 level using a Friedman two-way analysis of variance by ranks. It can be concluded that the presence of aortic arteriosclerotic lesions and intervertebral disk chondrocalcinosis add a significant contribution to BMD.

Potential value of vertebral proton MR spectroscopy in determining bone weakness

BACKGROUND AND PURPOSE

Increased fat content in vertebrae may indicate bone weakness. Vertebral proton MR spectroscopy ((1)H MRS) quantitatively measures vertebral fat relative to water. Thus, (1)H MRS measurements of percent fat fraction (%FF) and spectral line width (LW) of vertebral bone marrow may differ between subjects with and those without MR imaging evidence of weakened bone.

METHODS

We measured %FF and LW in 22 subjects with (15 men and 7 women, aged 26 to 80 years) and 72 control subjects without (33 male and 39 female subjects, aged 15 to 87 years) MR findings of weakened bone, including prominent Schmorl's nodes, endplate depression, vertebral wedging, and vertebral compression fractures. In those with bone weakness, (1)H MRS data were sampled from an intact vertebra, usually L2. Data were analyzed for differences by age and sex. We compared the mean %FF and LW in subjects with and in those without bone weakness by use of Student's t test.

RESULTS

The %FF increased linearly with age in the control subjects, ranging from 20.5% in the second and third decades of life to 49.4% in eighth or ninth decades of life. Across all age groups, male control subjects had a higher aggregate %FF than did female control subjects. Male control subjects tended to have a greater LW than did female control subjects, but differences between the sexes within or across age groups were not significant. Contrary to expectations, LW was greatest in the oldest control subjects and lowest among younger control subjects, but there were insufficient data points to make definitive conclusions. Overall, %FF was a relative 45% higher in subjects with weakened bone compared with control subjects (48.8 vs 33.6 [P <.001]). The subjects with evidence of vertebral bone weakness also had a higher overall mean LW (37 vs 29 Hz [P <.002]), but this finding is of uncertain importance.

CONCLUSION

The %FF was significantly higher within the L2 vertebral body in 22 subjects with weakened bone compared with the control group, suggesting that it could serve as a measure of bone quality. The LW measurements did not yield meaningful conclusions.

Impaired Th1 cytokine production in spondyloarthropathy is restored by anti-TNFalpha

OBJECTIVES

To evaluate the effect of anti-TNFalpha on the Th1 and Th2 cytokines in patients with spondyloarthropathy (SpA).

METHODS

Peripheral blood mononuclear cells (PBMC) were obtained from 20 patients with active SpA treated with infliximab (5 mg/kg). For comparison, PBMC were also obtained from 15 healthy controls and 19 patients with active rheumatoid arthritis (RA). After stimulation with PMA/ionomycin, the intracellular cytokines interleukin (IL)2, IL4, IL10, and interferon (IFN)gamma were determined in CD3+ T cells and in CD3+/CD56+ natural killer (NK) T cells by flow cytometry.

RESULTS

At baseline the percentage of T cells positive for IFNgamma (p=0.020) and IL2 (p=0.046) was decreased in patients with SpA compared with healthy controls, while IL10 (p=0.001) was increased. This cytokine profile, confirmed by the mean fluorescence intensities (MFI), was more pronounced in CD3+/CD8- cells and contrasted with higher IL2 production in RA. NK T cells, characterised by high IL4 and IL10 numbers, were also increased in patients with SpA (p=0.017). Treatment with infliximab induced a significant and persistent increase in IFNgamma and IL2 in patients with SpA. Moreover, there was a transient decrease in IL10 and NK T cells in patients with high baseline values, resulting in values comparable with those of healthy controls. This switch in cytokine profile was seen in both the CD3+/CD8- and CD3+/CD8+ subsets.

CONCLUSIONS

Before treatment patients with SpA had an impaired Th1 cytokine profile compared with healthy controls and patients with RA. TNFalpha blockade induced restoration of the Th1 cytokines, resulting in a normal cytokine balance. These data confirm the effect of anti-TNFalpha on the immune changes in SpA, and provide insights into the mechanisms involved in TNFalpha blockade.

Elevated protein content and prolyl 4-hydroxylase activity in severely degenerated human annulus fibrosus

Alterations involved with the intervertebral disc degeneration are partly well described, however, it is not so well known how collagen network is affected by the disease. We analyzed the rate of collagen biosynthesis (estimated by the enzymic activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase) and the level of hydroxylysylpyridinoline and lysylpyridinoline crosslinks both in normal (n=7) and degenerated (n=7) human annulus fibrosus. The activity of prolyl 4-hydroxylase was significantly increased in degenerated tissue. However, no significant changes in the collagen content or in the amount of hydroxylysylpyridinoline and lysylpyridinoline collagen crosslinks were observed. On the other hand, the content of soluble proteins was significantly increased. Our results suggest that collagen biosynthesis is increased in degenerated human annulus fibrosus, obviously to compensate the impairment of collagen fibers. The faster turnover of collagen in degenerated annulus fibrosus, suggested by the increased prolyl 4-hydroxylase activity and unchanged collagen content, seems not to cause any significant changes in its mature pyridinium crosslink concentrations.

Anterior cervical instrumentation enhances fusion rates in multilevel reconstruction in smokers

This retrospective consecutive case study evaluated the effect of anterior plating on multilevel anterior cervical decompressions and fusions in smokers and non-smokers. Multilevel anterior cervical decompression and fusion surgery in smokers provides an important challenge. Higher nonfusion rates in smokers have been reported. Cigarette smoking has been shown to interfere with bone metabolism and revascularization and to suppress bone formation. One hundred six patients underwent anterior cervical decompression and fusion using autografts or allografts and anterior plating. The minimum follow-up was 12 months. The mean age was 50.12 years (+/- 11.72; range, 27 to 80 years). Autografts were used in 90 patients and allograft in 16. The mean level fused was 2.74 (+/- 0.61). Forty-six (45.5%) patients were smokers. Successful fusion was achieved in all but three patients (97.17%). C5 root weakness was seen in four patients (3.8%); two patients experienced acute airway obstruction, of which one required tracheotomy. Temporary recurrent laryngeal nerve palsy developed in three (2.8%) patients. A fusion rate of 97% was achieved in multilevel anterior cervical decompression and fusions using anterior plating. No difference in fusion rates between smokers and nonsmokers was seen. Anterior cervical plating markedly improved the fusion rate in smokers.

Unusual facet cyst containing struvite and hydroxyapatite

This case report describes a patient with severe back pain and radiculopathy. She was found to have a facet cyst within the lumbar spine that appeared to contain calcium on MRI and CT. Upon aspiration the cyst was found to contain calcium ammonium phosphate (struvite) and calcium phosphate (hydroxyapatite). Ammonia production in the presence of urease-producing bacteria is responsible for the production of struvite in the human body. We postulate that there was a prior infection of the facet with urease-producing bacteria, thus accounting for the production of the struvite within the facet cyst.

Immunohistochemistry of chondromodulin-I in the human intervertebral discs with special reference to the degenerative changes

The expression of the matrix protein chondromodulin-I has been studied in human intervertebral discs of 101 people using immunohistochemical analyses. The purpose of this report is to present data on the metabolic changes that were found to occur in the chondrocytes of intervertebral discs during development and aging. Chondromodulin-I was highly expressed during the gestational period and gradually decreased after maturation. It was detected in both the extracellular matrix and chondrocytes in the zone of hypertrophic cartilage, the zone of proliferative cartilage and the zone of resting cartilage in fetal discs. It was also present in the annulus fibrosus, nucleus pulposus and end-plate cartilage in mature discs. In degenerative discs, chondromodulin-1 immunoreactivity tended to be elevated in the remaining chondrocytes. Our findings suggest that the expression of the protein is developmentally regulated and upregulated through a defense mechanism against the degenerative processes of the aged intervertebral disc.

Compression-induced changes in intervertebral disc properties in a rat tail model

STUDY DESIGN

An Ilizarov-type apparatus was applied to the tails of rats to assess the influence of immobilization, chronically applied compression, and sham intervention on intervertebral discs of mature rats.

OBJECTIVES

To test the hypothesis that chronically applied compressive forces and immobilization cause changes in the biomechanical behavior and biochemical composition of rat tail intervertebral discs.

SUMMARY OF BACKGROUND DATA

Mechanical factors are associated with degenerative disc disease and low back pain, yet there have been few controlled studies in which the effects of compressive forces on the structure and function of the disc have been isolated.

METHODS

The tails of 16 Sprague-Dawley rats were instrumented with an Ilizarov-type apparatus. Animals were separated into sham, immobilization, and compression groups based on the mechanical conditions imposed. In vivo biomechanical measurements of disc thickness, angular laxity, and axial and angular compliance were made at 14-day intervals during the course of the 56-day experiment, after which discs were harvested for measurement of water, proteoglycan, and collagen contents.

RESULTS

Application of pins and rings alone (sham group) resulted in relatively small changes of in vivo biomechanical behavior. Immobilization resulted in decreased disc thickness, axial compliance, and angular laxity. Chronically applied compression had effects similar to those of immobilization alone but induced those changes earlier and in larger magnitudes. Application of external compressive forces also caused an increase in proteoglycan content of the intervertebral discs.

CONCLUSIONS

The well-controlled loading environment applied to the discs in this model provides a means of isolating the influence of joint-loading conditions on the response of the intervertebral disc. Results indicate that chronically applied compressive forces, in the absence of any disease process, caused changes in mechanical properties and composition of tail discs. These changes have similarities and differences in comparison with human spinal disc degeneration.

Molecular biology and spinal disorders. A survey for the clinician

Over the past 10 years, advances in molecular biology techniques have extended the potential for understanding spinal disorders from the microscopic (histologic) level down to the molecular level of gene expression within individual cells. These advances are initiating new avenues of research and, ultimately, novel clinical treatments. The intent of this update is to provide the spine clinician with a basic understanding of molecular biology, the type of information that may be learned from its application, and the potential for gene therapy in spine disorders.

Reevaluation of discograms not classified into usual classifications

Discograms of images that were eccentrically dyed because of insufficient infiltration of contrast medium are difficult to classify into the usual past discogram patterns. In this study, these types of images were detected in 40 discs of 36 patients with lumbar disc disease. We classified these images into the following three types, and analyzed the dye mechanisms in each case by computed tomography discographic findings: (1) type A (image of the annulus fibrosus only). Nine discs in nine cases. A part of the marginal annulus fibrosus was dyed. (2) type B (image of the right or left half of the nucleus pulposus). Eighteen discs in 15 cases. Unilateral dyeing was considered nucleus pulposus existing in the central region of the disc. (3) type C (partial image of the superior or inferior half of the nucleus pulposus). Thirteen discs in 12 cases. Only the superior or inferior half showing a cotton-ball pattern was dyed.

The effect of compressive force applied to the intervertebral disc in vivo. A study of proteoglycans and collagen

STUDY DESIGN

Coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs of dogs for up to 27 weeks.

OBJECTIVE

To test the hypothesis that a high compressive force applied over a period of time affects the production of proteoglycans and collagen by the intervertebral disc cells.

SUMMARY OF BACKGROUND DATA

It is a commonly held belief that high forces applied to the intervertebral disc, and to joints in general, play a role in causing degeneration.

METHODS

Pairs of stainless steel coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs (L1-L2 and L3-L4) of 16 dogs. Dogs were killed between 13 and 27 weeks after the springs were attached. The discs (L1-L2 and L3-L4) were excised and assessed using immunohistochemical analyses and enzyme-linked immunosorbent assay; T13-L1 and L4-L5 were used as controls.

RESULTS

The main result relates to a group effect in the six dogs, assessed using enzyme-linked immunosorbent assay, that were generally at the highest values of force for the greatest number of weeks. For the nucleus, but not the anulus, Spearman rank correlations revealed a strong correlation between increases in force and force-weeks (force multiplied by number of weeks) and increases in collagen type I accompanied by decreases in proteoglycans, chondroitin sulfate, and collagen type II for both experimental discs (L1-L2 and L3-L4), as compared with corresponding values in the controls (T13-L1 and L4-L5). In other words, as either the force or the force-weeks increased, the effect on the nucleus became greater.

CONCLUSION

A high compressive force applied to the disc over a period of time initiates changes in proteoglycans and collagen.

Quantitative magnetic resonance imaging in the assessment of degenerative disc disease

Understanding degenerative intervertebral disc diseases hinges on the ability to objectively and noninvasively assess the disc matrix composition and integrity. The potential of quantitative magnetic resonance imaging to meet these demands was evaluated. Analyzing the T1 and T2 signal patterns in the nucleus pulposus with increasing Thompson morphological grade revealed a significant reduction related to grade. This significant decrease in T1 and T2 in the nucleus pulposus with grade 4 degeneration and the corresponding low correlation coefficients with respect to the content of individual matrix molecules suggest that matrix integrity plays an important and distinct role in determining T1 and T2 signal. Similarly, the significant increase in magnetization transfer in the nucleus pulposus observed in grade 4 degeneration did not correlate with the changes in molecular content in these highly degenerated discs. Again, this lack of correlation clearly indicates that the tissue integrity and matrix composition independently contribute to the magnetization transfer signal. This study presents the first clear evidence that quantitative magnetic resonance analysis reflects not only the disc matrix composition, but also the structural integrity of the matrix of the disc.

Compression-induced degeneration of the intervertebral disc: an in vivo mouse model and finite-element study

STUDY DESIGN

An in vivo study of the biologic and biomechanical consequences of static compressive loading on the mouse tail intervertebral disc.

OBJECTIVES

To determine whether static compression in vivo alters the biologic activity of the disc and leads to diminished biomechanical performance.

SUMMARY OF BACKGROUND DATA

Static compressive stress that exceeds the disc's swelling pressure is known to change hydration and the intradiscal stress distribution. Alterations in hydration and stress have been associated with changes in disc cell activity in vitro and in other collagenous tissues in vivo.

METHODS

Mouse tail discs were loaded in vivo with an external compression device. After 1 week at one of three different stress levels, the discs were analyzed for their biomechanical performance, morphology, cell activity, and cell viability. A second group of mice were allowed to recuperate for 1 month after the 1-week loading protocol to assess the disc's ability to recover. As an aid to interpreting the histologic and biologic data, finite-element analysis was used to predict region-specific changes in tissue stress caused by the static loading regimen.

RESULTS

With increasing compressive stress, the inner and middle anulus became progressively more disorganized, and the percentage of cells undergoing apoptosis increased. The expression of Type II collagen was suppressed at all levels of stress, whereas the expression of aggrecan decreased at the highest stress levels in apparent proportion to the decreased nuclear cellularity. Compression for 1 week did not affect the disc bending stiffness or strength but did increase the neutral zone by 33%. As suggested by the finite-element model, during sustained compression, tension is maintained in the outer anulus and lost in the inner and middle regions where the hydrostatic stress was predicted to increased nearly 10-fold. Discs loaded at the lowest stress recovered anular architecture but not cellularity after 1 month of recuperation. Discs loaded at the highest stress did not recover anular architecture, displaying islands of cartilage cells in the middle anulus at sites previously populated by fibroblasts.

CONCLUSIONS

The results of the current project demonstrate that static compressive loading initiates a number of harmful responses in a dose-dependent way: disorganization of the anulus fibrosus; an increase in apoptosis and associated loss of cellularity; and down regulation of collagen II and aggrecan gene expression. The finite element model used in this study predicts loss of collagen fiber tension and increased matrix hydrostatic stress in those anular regions observed to undergo programmed cell death after 1 week of loading and ultimately become populated by chondrocytes after one month of recuperation. This correspondence conforms with the suggestions of others that the cellular phenotype in collagenous tissues is sensitive to the dominant type of tissue stress. Although the specific mechanisms by which alterations in tissue stress lead to apoptosis and variation in cell phenotype remain to be identified, our results suggest that maintenance of appropriate stress within the disc may be an important basis for strategies to mitigate disc degeneration and initiate disc repair.

Decreased nitric oxide levels and bone turnover in amenorrheic athletes with spinal osteopenia

Amenorrheic athletes have been likened to postmenopausal women, with low estrogen levels and osteopenia. It has been suggested that estrogen exerts its antiresorptive actions on bone via a nitric oxide (NO)-dependent mechanism. This study investigated whether the mechanism of bone loss in amenorrheic athletes is similar to that of postmenopausal women with reduced NO levels and high bone turnover. Eleven amenorrheic athletes, 15 eumenorrheic athletes, and 10 sedentary controls were studied. Spine and hip bone mineral density was measured using dual-energy x-ray absorptiometry. Bone turnover was assessed by biochemical markers of formation (osteocalcin and bone-specific alkaline phosphatase) and resorption (deoxypyridinoline). NO metabolites were measured from 24-h urine samples using a chemiluminescence assay. Spine, but not hip, bone mineral density was reduced in the amenorrheic group, compared with the eumenorrheic (P = 0.0001) and control (P = 0.04) groups. Osteocalcin, bone-specific alkaline phosphatase, and deoxypyridinoline were similar in all groups. NO metabolites were lower in the amenorrheic group, compared with controls (P = 0.035), despite a higher dietary intake of nitrates. Unlike postmenopausal women, amenorrheic athletes do not have raised bone turnover but do have reduced NO metabolites and spinal osteopenia. The results show, however, that reduced NO production is a common denominator in both conditions and further support the importance of NO in estrogen-mediated protection of skeletal mass and strength.

Torsional injury resulting in disc degeneration: I. An in vivo rabbit model

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

Torsional injury resulting in disc degeneration in the rabbit: II. Associative changes in dorsal root ganglion and spinal cord neurotransmitter production

The mechanism mediating the chronic pain associated with lumbar disc degeneration may involve neurotransmitters elaborated by dorsal root ganglion (DRG). This hypothesis has been tested in an applicable rabbit model of disc degeneration. Twenty control male rabbits underwent a soft-tissue release; 20 experimental rabbits sustained a facetectomy and capsulotomy and received an acute torsional lumbar injury. The levels of calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P were measured in the DRG, spinal cord, and disc at 10, 30, 60, and 90 days postoperatively. Torsional injury was associated with a statistically significant increase in most DRG and spinal cord neurotransmitter values after 60-90 days. These points in time marked the periods of maximum biomechanical instability and disc narrowing. Such data support concepts about the association between chronic lumbar spinal instability, disc degeneration, and pain.

Leukaemia inhibitory factor (LIF) production in a mouse model of spinal trauma

A model of spinal trauma was developed where spinal neurones of adult mice were exposed to the excitotoxic glutamate analogue beta-N-oxylamino-L-alanine (L-BOAA). After 24 h, the injured neurones received a single dose of [125I]-LIF at the same site of the spinal cord, and 2 h later, tissues were removed to assess the distribution of leukaemia inhibitory factor (LIF). There was a significant increase in LIF binding to the injured region of the spinal cord over saline controls, and this corresponded with a significant increase in LIF mRNA expression in the same region of the cord. There was a change in the expression of ciliary neurotrophic factor, but the expression of cardiotrophin-1 (CT-1) and the common receptor subunit LIF receptor beta (LIFRbeta) did not change after neurotoxin treatment. The results add to the evidence that LIF plays a significant role in the response of adult neuronal tissue to injury.

Degeneration affects the anisotropic and nonlinear behaviors of human anulus fibrosus in compression

Axial and radial specimens of non-degenerate and degenerate human anulus fibrosus (AF) were tested in confined compression to test the hypothesis that degeneration significantly affects the compressive properties of AF. Due to the highly oriented structure of AF, a secondary objective was to investigate anisotropic behaviors of AF in compression. Uniaxial swelling and stress relaxation experiments were performed on site-matched samples of anulus from the anterior outer region of L2-3 intervertebral discs. The experimental stress-relaxation behavior was modeled using the finite deformation biphasic theory and a finite-difference approximation scheme. Significant effects of degeneration but not orientation were detected for the reference stress offset, sigma(offset), and parameters describing the compressive stiffness (i.e. reference aggregate modulus, H(A0), and nonlinear stiffening coefficient, beta). Average values were 0.13+/-0.06 and 0.05+/-0.05 MPa for sigma(offset), 0.56+/-0.21 and 1.10+/-0.53 MPa for H(A0) and 2.13+/-1.48 and 0.44+/-0.61 for beta for all normal and degenerate specimens, respectively. No significant effect of degeneration or orientation were detected for either of the parameters describing the strain-dependent permeability (i.e. reference permeability, k0 and strain-dependent permeability coefficient, M) with average values for all specimens of 0.20+/-0.10 x 10(-15) m4/N-s and 1.18+/-1.30 for k0 and M, respectively. The loss of sigma(offset) was compensated with an elastic stiffening and change in the shape of the equilibrium stress-strain curve with H(A0) for degenerate tissues almost twice that of normal tissues and beta less than one sixth. The increase in reference elastic modulus with degeneration is likely related to an increase in tissue density resulting from the loss of water content. The significant effects of degeneration reported in this study suggested a shift in load carriage from fluid pressurization and swelling pressure to deformation of the solid matrix of the AF. The results also suggest that the highly organized and layered network of the anulus fibrosus, which gives rise to significant anisotropic effects in tension, does not play a major role in contributing to the magnitude of compressive stiffness or the mechanisms of fluid flow of the anulus in the confined compression configuration.

Keratan sulfate as a potential biomarker of loading of the intervertebral disc

STUDY DESIGN

A review of the literature.

OBJECTIVE

To investigate the potential of serum levels of keratan sulfate as a biomarker of the effects of loading of the spine.

SUMMARY OF BACKGROUND DATA

Exposure to mechanical loading of the spine causes changes in metabolism of intervertebral discs, eventually leading to accelerated disc degeneration. This process is characterized by the degradation of proteoglycans, which is reflected by an increase in the blood level of proteoglycan components. The serum level of keratan sulfate, an epitope present on these proteoglycan components, has been suggested as a marker of changes in metabolism of cartilaginous tissues.

METHODS

A review of the literature on serum keratan sulfate levels in relation to degenerative changes in cartilaginous tissue.

RESULTS

In a number of studies keratan sulfate in serum was reported to be related to degeneration of articular cartilage in patients with osteoarthritis. In addition, massive and rapid degradation of intervertebral discs was determined to result in a large rise in serum keratan sulfate levels. Whether degenerative changes of intervertebral discs induced by mechanical stress also cause a detectable increase in serum keratan sulfate should be subjected to further investigation.

CONCLUSION

Quantification of keratan sulfate in serum offers a promising measure for the early effects of mechanical loading of the spine, but research is needed for validation.

Immunolocalization of major interstitial collagen types in human lumbar intervertebral discs of various ages

We used complete transverse sections through 65 samples of human lumbar intervertebral discs for immunolocalization of the major interstitial collagen types I, II, III, V, VI and IX. The samples were selected from 47 patients ranging in age from 0 (fetuses) to 86 years. The results were compared with the histological findings in disc tissue degeneration and/or reparative alterations as indicated by tear and cleft formation, chondrocyte proliferation, mucous degeneration, granular matrix changes and fibrocartilage fibrillation. We observed a typical pattern for each antibody and each anatomical structure, with, however, remarkable inter- and intraindividual variability, which could be monitored only by use of the complete transverse sections. Accordingly, collagen I was seen in the normal annulus fibrosus and in the degeneratively altered nucleus pulposus, but not within the end-plate, regardless of degenerative changes. Collagens II and IX were found in the normal nucleus pulposus, the inner annulus fibrosus and the end-plate. The collagen II (and IX) staining seemed to be enhanced in areas of minor degenerative lesions, but reduced in advanced lesions and in the degenerated end-plate. Collagens III and VI were significantly increased in areas of minor to advanced degeneration in all anatomical settings, while collagen V showed only minor changes in its staining pattern. In general, histological signs of tissue degeneration coincided with significant quantitative, but also with certain qualitative, changes in the composition of the collagenous disc matrix. These observations indicate the association of degenerative and/or reparative alterations of the intervertebral disc and changes in the collagenous matrix, but document the variability in the extent of the abnormalities observed.