[Pathology of the intervertebral discs].
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The oncoproteins c-Fos and c-Jun create a transcriptional site early response activating protein (AP-1) mediating the regulation of gene expression in response to extracellular signalling by, for example, cytokines. These proteins are important in the signalling pathway from the cell membrane to the nucleus. Previously, oncoproteins have been located in articular synovium and in chondrocytes, participating in transcription. There is, however, no such study of intervertebral disc tissue. In disc degeneration and after herniation, cell proliferation markers have been demonstrated. In the present study we visualize the AP-1 transcriptional site factors c-Fos and c-Jun in 38 human herniated intervertebral disc tissue samples by immunohistochemical staining with monoclonal antibodies. No immunoreactivity could be observed in control disc tissue, indicating that after herniation, disc cells are entering from the resting stage to the cell cycle. Furthermore, c-Jun immunoreactivity was also observed in disc cell clusters, thus demonstrating them to be active transcriptional sites in disc tissue. c-Fos immunoreactivity was seen in 15/38 and c-Jun in 28/38 herniated discs (39% and 74% respectively). Immunopositive groups of disc cells were noted in 7/28 (25%) of the oncoprotein-immunopositive samples. We did not see any difference in immunoreactivity between female and male patients. Furthermore, we did not notice any statistical difference regarding the immunoreaction for proto-oncogenes c-Fos and c-Jun in extrusions, sequesters and protrusions. Nor did immunostaining show any significant relationship with preoperative pain duration. We concluded that, in herniated disc tissue, the oncoproteins c-Fos and c-Jun are activated in disc cells and cell clusters. In the future, learning more about this transcriptional signal pathway may result in new specific treatments for intervertebral disc pathology.
The suitability of two different implant types for the replacement of the intervertebral disc was studied in vitro. Self-reinforced poly-L-lactide (SR-PLLA) screws Ø 4.5 mm were studied 24 weeks in vitro and cylindrical implants with elastic nucleus made of poly(L/D)lactide 96/4, poly(L/DL)lactide 70/30, Bioactive Glass n:o 13-93 and Polyactive 1000PEOT70PBT30 were studied 15 weeks in vitro. The cylindrical implant mimics the size and shape of the intervertebral disc. During the in vitro, there were no changes in compression properties with either implant types. The screws had sufficient modulus for intervertebral ossification in the canine model and the cylindrical implant showed also sufficient mechanical properties. These results suggest that both implant types could be used in clinical testing.
The objectives of this study were (1) to quantify changes in the mechanical behavior of the intervertebral disc in response to cyclic compressive loading and (2) to determine whether mechanical behavior would be restored following a period of unloading. The elastic and viscoelastic compressive mechanical behaviors of adult sheep motion segments were assessed. Ten thousand cycles of compressive loading resulted in increased elastic stiffness and decreased stress-relaxation. After 18 h of unloading in a PBS bath stiffness and relaxation were fully restored. Cyclic loading did not cause structural damage as determined by radiographs and magnetic resonance images. After cyclic loading, average stiffness increased from 603 to 800 N/mm (p = 0.015) and returned to initial levels after the recovery period. Cyclic loading caused a decrease in total relaxation (from 92 to 38 N, p < 0.001) that also returned to initial levels after recovery. The reversible, repeatable effects of cyclic loading and recovery demonstrated in this in vitro study may be attributed to fluid flow. Intervertebral disc fluid transport during the diurnal recovery cycle may be key to understanding intervertebral disc degeneration, as fluid exudation and recovery may be integral to maintaining adequate disc nutrition.
Inflammation and irritation of the nerve roots has been indicated as an important factor in the pain associated with symptomatic disc herniations. Tumour necrosis factor alpha (TNFalpha) is now believed to be involved in this pathway. TNFalpha causes connective tissue cells in culture to synthesise a glycoprotein, TNFalpha-stimulated gene-6 (TSG-6). TSG-6 is found in inflammatory diseases of related connective tissues, such as articular cartilage in rheumatoid arthritis, but is not present in unaffected individuals. In order to determine if TSG-6 occurred in intervertebral disc (and cartilage endplate), we have investigated the presence of TSG-6 and its binding protein, inter-alpha-inhibitor (IalphaI), in 58 herniated and 15 non-herniated discs. Immunostaining for the cytokines, IL-1alpha, IL-1beta and TNFalpha, has also been carried out. We have demonstrated that both TSG-6 and IalphaI occur commonly in human intervertebral disc matrix with at least some TSG-6 in 98% of discs studied and IalphaI in all of them. Staining for TSG-6 was greatest in herniated discs, particularly close to blood vessels. IalphaI immunostaining was frequently widespread throughout the disc but there was little in the cartilage endplate. It has been proposed that these molecules have widespread effects, including extracellular matrix stabilisation, down-regulation of the protease network and reduction of inflammation. Hence, the occurrence of TSG-6 and IalphaI in disc tissue could have implications in the aetiopathogenesis and future therapeutics of intervertebral disc disease.
Laser induced fluorescence of intervertebral discs was investigated in this study for the first time in order to develop a fluorescence guided percutaneous excimer laser discectomy. For this purpose 35 human cadaveric intervetebral discs from level L1 to L5 were irradiated with a 308 nm XeCl excimer laser with a 60 nsec pulse width at 10, 20 and 30 mj/mm2. Laser light was transmitted over a 1000 microns core optical fiber. Fluorescence emitted from the irradiated tissue was transmitted back over the same fiber over a semireflective mirror to another optical fiber, coupled into a spectrograph and O-SMA optical simultaneous multichannel spectral analyzer system. The spectral lineshape of both the annulus fibrosus and the nucleus pulposus was characterized by a broadband emission between 320 nm and 616 nm with 3 peak emissions at 358, 423 and 457 nm. Relative intensities were calculated by forming two ratios of the peak intensities of the three peaks (R1 = I 423/I 358; R2 = I 423/I 457). Statistical analysis of both ratios revealed a highly significant discrimination between annulus fibrosus and nucleus pulposus (P less than 0.001). Under penetrating conditions multiple recorded spectra showed the spectral profile of subsequently ablated nucleus and annulus. The results of this study demonstrate that discrimination between annulus fibrosus and nucleus pulposus by excimer laser-induced fluorescence is feasible under laboratory conditions. Fluorescence spectroscopy could possibly be developed into a valuable guiding system for percutaneous laser discectomy.
Very little is known about the turnover of extracellular matrix in the human intervertebral disc. We measured concentrations of specific molecules reflecting matrix synthesis and degradation in predetermined regions of 121 human lumbar intervertebral discs and correlated them with ageing and Thompson grade of degeneration. Synthesis in intervertebral discs, measured by immunoassay of the content of a putative aggrecan biosynthesis marker (846) and the content of types I and II procollagen markers, is highest in the neonatal and 2-5-yr age groups. The contents of these epitopes/molecules progressively diminished with increasing age. However, in the oldest age group (60-80 yr) and in highly degenerated discs, the type I procollagen epitope level increased significantly. The percentage of denatured type II collagen, assessed by the presence of an epitope that is exposed with cleavage of type II collagen, increased twofold from the neonatal discs to the young 2-5-yr age group. Thereafter, the percentage progressively decreased with increasing age; however, it increased significantly in the oldest group and in highly degenerate discs. We identified three matrix turnover phases. Phase I (growth) is characterized by active synthesis of matrix molecules and active denaturation of type II collagen. Phase II (maturation and ageing) is distinguished by a progressive drop in synthetic activity and a progressive reduction in denaturation of type 11 collagen. Phase III (degeneration and fibrotic) is illustrated by evidence for a lack of increased synthesis of aggrecan and type II procollagen, but also by an increase in collagen type II denaturation and type I procollagen synthesis, both dependent on age and grade of tissue degeneration.
The vascular channels at the end-plate of the intervertebral disc are very important in maintaining a healthy disc. With age, a reduction of the nutrition of the avascular nucleus pulposus is inevitable. On the other hand the calcium channel antagonist nimodipine has been shown to have a positive effect on blood flow in the region of the vertebral end-plate. To evaluate the effects of nimodipine on the end-plate vascularity in the degenerative discs, we have produced an experimental disc degeneration and evaluated the radiological and histopathological features of the end-plate of the degenerated discs. Adult rats were divided into 3 groups: control (n=5), operated degeneration (n=5), and nimodipine treatment (n=5). Using a posterior approach, a cut was made parallel to the end-plates in the posterior annulus fibrosus in 5 consecutive intervertebral discs between the 5th and 10th vertebral segments of the tails of adult Swiss Albino rats. At 8 weeks, 5 of these animals were treated with nimodipine. In each experimental group, 1 animal was examined using computed tomography (CT) to study the density of the cartilage end-plate of the disc. Then, the animals were sacrificed for subsequent histopathological evaluation. We found that the vascular channel counts and percentage areas from animals treated with nimodipine were higher than from both the non-operative control and operated degeneration groups, although these were not statistically different. Accordingly, the profile of the density histogram in the nimodipine-treated group showed a wide plateau, indicating an increase in the vascularity in this region. From our results, we suggest that nimodipine enhances vascularisation of the cartilage end-plate in the disc. It is possible that the increased proportion of vascular contacts at the end-plate has a beneficial effect in the nutrition of the disc. However, further experimental studies will be needed to determine the validity of this statement in animals or human beings.
OBJECTIVES: To examine whether collagen type I alpha1 (COLIA1) Sp1 polymorphism is associated with osteoporosis and/or intervertebral disc degeneration in older people. METHODS: COLIA1 genotype was determined in 966 men and women (>/=65 years) of the Longitudinal Aging Study Amsterdam. The guanine (G) to thymidine (T) polymorphism in the first intron of the COLIA1 gene was detected by PCR and MscI digestion. In the total sample, quantitative ultrasound (QUS) measurements, serum osteocalcin (OC), and urine deoxypyridinoline (DPD/Cr(urine)) were assessed. A follow up of fractures was done every three months. In a subsample, total body bone mineral content (n = 485) and bone mineral density (BMD) of the hip and lumbar spine (n = 512) were measured by dual energy x ray absorptiometry (DXA). Prevalent vertebral deformities and intervertebral disc degeneration were identified on radiographs (n = 517). RESULTS: People with the TT genotype had a higher risk of disc degeneration than those with the GG and GT genotypes (OR = 3.6; 95% CI 1.3 to 10). For men, higher levels of OC were found in those with the T allele than in those without it (GG v (GT+TT) 1.96 (0.06) nmol/l v 2.19 (0.09) nmol/l). COLIA1 polymorphism was not significantly associated with other measures of osteoporosis in either men or women. CONCLUSION: COLIA1 Sp1 polymorphism may be a genetic risk factor related to intervertebral disc degeneration in older people. Previously reported associations between the COLIAI Sp1 genotype and lower BMD or QUS values, higher levels of DPD/Cr, and an increased fracture risk in either men or women could not be confirmed.
Although the role of growth factors in the regulation of phenotype, maintenance, and repair of cartilaginous tissues has been extensively evaluated, the response of intervertebral disc to growth factors has not been investigated. A tissue culture system for annular, transitional, and nuclear regions of mature canine intervertebral disc was devised to assess the proliferative response, as determined by 3H-thymidine incorporation, and the biosynthetic response, assayed by 35S-sulfate incorporation into proteoglycan, of these tissues to growth factors. The culture system achieved steady-state conditions in serum-free mediums at 4 days and was perturbed by plasma-derived equine serum, fetal calf serum, insulin-like growth factor-1, epidermal growth factor, fibroblast growth factor, and transforming growth factor-beta. Incorporation rates by the tissue regions of up to five times the control rate were recorded; the nucleus and transition zone responded more than anulus. Transforming growth factor-beta and epidermal growth factor elicited greater responses than fibroblast growth factor; insulin-like growth factor-1 produced a marginally significant response in the nucleus and no response in the anulus and transition. The intervertebral disc appeared to respond to the growth factors differently than cartilage, and this may represent inherent differences in cell biology. The biologic significance and basis of these responses require further evaluation. However, the responses observed, particularly in the nucleus and transition zone suggest the possibility that disc repair can be modulated by growth factors. A therapeutic approach to degenerative disc disease involving enhanced tissue repair by exogenous growth factors would be of great clinical significance.
Low back pain is one of the largest health problems in the Western world today, and intervertebral disc degeneration has been identified as a main cause. Currently, treatments are symptomatic, but cell-based tissue engineering methods are realistic alternatives for tissue regeneration. However, the major problem for these strategies is the generation of a suitable population of cells. Adult bone marrow-derived mesenchymal stem cells (MSCs) are undifferentiated, multipotent cells that have the ability to differentiate into a number of cell types, including the chondrocyte-like cells found within the nucleus pulposus (NP) of the intervertebral disc; however, no method exists to differentiate these cells in an accessible monolayer environment. We have conducted coculture experiments to determine whether cells from the human NP can initiate the differentiation of human MSCs with or without cell-cell contact. Fluorescent labeling of the stem cell population and high-speed cell sorting after coculture with cell-cell contact allowed examination of individual cell populations. Real-time quantitative polymerase chain reaction showed significant increases in NP marker genes in stem cells when cells were cocultured with contact for 7 days, and this change was regulated by cell ratio. No significant change in NP marker gene expression in either NP cells or stem cells was observed when cells were cultured without contact, regardless of cell ratio. Thus, we have shown that human NP and MSC coculture with contact is a viable method for generating a large population of differentiated cells that could be used in cell-based tissue engineering therapies for regeneration of the degenerate intervertebral disc.
Herniated intervertebral disc tissue has been shown to produce a number of proinflammatory mediators and cytokines, but there have been no similar studies using discs from patients with discogenic low back pain. We have compared the levels of production of interleukin-6 (IL-6), interleukin-8 (IL-8) and prostaglandin E2 (PGE2) in disc tissue from patients undergoing discectomy for sciatica (63) with that from patients undergoing fusion for discogenic low back pain (20) using an enzyme-linked immunoabsorbent assay. There was a statistically significant difference between levels of production of IL-6 and IL-8 in the sciatica and low back pain groups (p < 0.006 and p < 0.003, respectively). The high levels of proinflammatory mediator found in disc tissue from patients undergoing fusion suggest that production of proinflammatory mediators within the nucleus pulposus may be a major factor in the genesis of a painful lumbar disc.
STUDY DESIGN: Human intervertebral disc cells were harvested from patients with adolescent idiopathic scoliosis (AIS) and from donors with degenerative disc disease. Anulus fibrosis (AF) was separated from nucleus pulposus (NP), and cells were cultured separately in two different cell culture models. OBJECTIVES: To investigate changes in gene expression of human disc cells during in vitro expansion and to determine whether cells from adolescent idiopathic scoliosis donors show different gene expression profiles compared with cells from patients operated for degenerative disc disease. SUMMARY OF BACKGROUND DATA: During in vitro expansion, cells undergo a dedifferentiation process, which is characterized by a switch in gene expression. Markers for the differentiation and dedifferentiation status of human disc cells are not yet known. Moreover, it is not known whether changes in the gene expression pattern occur during the degeneration process. METHODS: Cells from AF and NP tissues were expanded in monolayer and alginate cultures under controlled and defined conditions. Cells were then harvested, and analysis of phenotype was performed using quantitative real-time polymerase chain reaction (PCR). The mRNA expression of Type I, II, and X collagen, aggrecan, and interleukin-1beta in scoliosis and degenerative human intervertebral disc cells was analyzed. RESULTS: The gene expression of Type II and X collagen and of aggrecan significantly decreased for both cell types during monolayer expansion. Reexpression of all genes was observed when cells were cultured in alginate. Additionally, NP cells from degenerative tissues displayed significant lower levels of Type II collagen compared with NP cells from scoliosis donors. CONCLUSIONS: These results provide a better understanding of how the phenotype of human healthy and degenerative disc cells is influenced by in vitro expansion. This may be useful for future tissue engineering purposes.
OBJECTIVES: To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. METHODS: Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. RESULTS: Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219.7, range 14.3 to 84.9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. CLINICAL SIGNIFICANCE: The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study.
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.
The present study was undertaken to investigate the effect of insulin-like growth factor-1 on proteoglycan synthesis and the autocrine/paracrine mechanism involving insulin-like growth factor-1 in the bovine coccygeal intervertebral disc. Insulin-like growth factor-1 stimulated proteoglycan synthesis in cultured cells of the nucleus pulposus of bovine intervertebral discs in a dose-dependent manner, and the effect was inhibited by an anti-insulin-like growth factor-1 monoclonal antibody. In situ hybridization histochemistry revealed the expression of insulin-like growth factor-1 mRNA in the cultured cells, and its production in these cells was demonstrated by radioimmunoassay. Insulin-like growth factor-1 receptor in the cultured cells was also demonstrated immunohistochemically. Scatchard analysis using an [125I]insulin-like growth factor-1 binding assay showed that the cells cultured in monolayer had a single type of insulin-like growth factor-1 receptor, whose affinity and number were estimated to be 7.38 x 10(8)/M and 9.27 x 10(4)/cell, respectively. These results suggest that insulin-like growth factor-1 stimulates proteoglycan synthesis in cells of the nucleus pulposus and that these cells in culture have an insulin-like growth factor-1 autocrine/paracrine mechanism. The expressions of insulin-like growth factor-1 mRNA and insulin-like growth factor-1 receptor in disc tissue were greater in cells of the nucleus pulposus of fetal bovine intervertebral discs than in those of the adult discs. These findings suggest that the action of autocrine/paracrine insulin-like growth factor-1 is more active in cells of the young nucleus pulposus than in cells of mature subjects.
Reinsertion of autogenous nucleus pulposus, an innovative method to delay further disc degeneration, has been proved with an experimental animal model. This study examined whether coculture of nucleus pulposus cells with annulus fibrosus cells (a) activates annulus fibrosus cells and (b) retards disc degeneration when reinserted into the disc in a rabbit model of disc degeneration. Coculture of the two cell types stimulated proliferation of each, as indicated by increased DNA synthesis measured by increases in DNA polymerase alpha expression and uptake of 5-bromo-2'deoxy-uridine assessed by an enzyme-linked immunosorbent assay. In a model of disc degeneration in rabbits, reinsertion of activated nucleus pulposus cells delayed the formation of clusters of chondrocyte-like cells, the destruction of disc architecture, and the elaboration of type-II collagen as measured immunohistochemically compared with no treatment. The direct reinsertion of activated nucleus pulposus cells into the disc offers a promising line of investigation for delaying intervertebral disc degeneration, although these results obtained with notochordal cells may not necessarily apply when mature central nucleus pulposus cells are used.
The nucleus pulposus of the lumbar intervertebral disc of mice given daily intramuscular injection of hydrocortisone at a dose of 1, 5, 10 mg/kg body weight for 1-4 weeks from 2 weeks of age was studied by electron microscopy. The hydrocortisone administration induced degeneration of the notochordal cells in the nucleus pulposus. The degenerative changes occurred earlier in the periphery of the nucleus pulposus than in the central region and developed earlier in mice treated with higher doses of hydrocortisone than in mice treated with lower doses. From the results, it is likely that steroid treatment accelerates the aging process of the nucleus pulposus and causes dysfunction of the intervertebral disc.