Abnormal connective tissue degrading enzyme patterns in prolapsed intervertebral discs

Measurement of local strains in intervertebral disc anulus fibrosus tissue under dynamic shear: contributions of matrix fiber orientation and elastin content

Shear strain has been implicated as an initiator of intervertebral disc anulus failure, however a clear, multi-scale picture of how shear strain affects the tissue microstructure has been lacking. The purposes of this study were to measure microscale deformations in anulus tissue under dynamic shear in two orientations, and to determine the role of elastin in regulating these deformations. Bovine AF tissue was simultaneously shear loaded and imaged using confocal microscopy following either a buffer or elastase treatment. Digital image analysis was used to track through time local shear strains in specimens sheared transversely, and stretch and rotation of collagen fiber bundles in specimens sheared circumferentially. The results of this study suggest that sliding does not occur between AF plies under shear, and that interlamellar connections are governed by collagen and fibrilin rather than elastin. The transverse shear modulus was found to be approximately 1.6 times as high in plies the direction of the collagen fibers as in plies across them. Under physiological levels of in-plane shear, fiber bundles stretched and re-oriented linearly. Elastin was found to primarily stiffen plies transversely. We conclude that alterations in the elastic fiber network, as found with IVD herniation and degeneration, can therefore be expected to significantly influence the AF response to shear making it more susceptible to micro failure under bending or torsion loading.

Low back pain: pathophysiology and management

Basic research is advancing the understanding of the pathogenesis and management of low back pain at the molecular and genetic levels. Frequently, low back pain is caused by disorders of the intervertebral disk. Cytokines such as matrix metalloproteinases, phospholipase A2, nitric oxide, and tumor necrosis factor-alpha are thought to contribute to the development of low back pain. Drugs are being developed to modulate these chemical mediators. Recent research using growth factors to promote chondrocyte regeneration appears to be promising. Advances in gene therapy to both prevent disk degeneration and regenerate the disk eventually may have clinical application.

The role of inflammation in disk herniation-associated radiculopathy

OBJECTIVE

The causes and physiopathology of low-back pain and acute lumbar radiculopathy remain unclear. A compression of the nerve root by protruded disk has been suggested but explains only partially the physiopathology of radicular pain. This article provides an overview of the role of inflammation in disk herniation-associated radiculopathy.

METHODS

A review of the relevant literature in American and European medical journals was performed.

RESULTS

Several studies have identified inflammatory mediators (phospholipase A2, prostaglandin E2, leukotrienes, nitric oxide, immunoglobulins, pro-inflammatory cytokines such as interleukin [IL]-1alpha, IL-1beta, IL-6, and tumor necrosis factor alpha [TNFalpha]) and autoimmune reaction (macrophages expressing IL-1beta, intercellular adhesion molecules) in disk herniation. An appealing hypothesis is that the leakage of these agents may produce an excitation of the nociceptors, a direct neural injury, a nerve inflammation, or an enhancement of sensitization to other pain-producing substances (such as bradykinin), leading to the nerve root pain. However, the role of these inflammatory mediators in the pathophysiology of lumbar radiculopathy has not been proven. Several findings suggest that this inflammatory response, which occurs in the early stage of disk herniation, is transient. Indeed, most studies of chronic disk herniation samples failed to demonstrate inflammation.

CONCLUSION

Although inflammation may partially explain lumbar radiculopathy, involvement of inflammatory mediators in the physiopathology of disk herniation-associated radiculopathy has not been proven.

Matrix metalloproteinases: the clue to intervertebral disc degeneration?

STUDY DESIGN

A review of the current literature on the role of matrix metalloproteinases in intervertebral disc degeneration.

OBJECTIVE

To detail the characteristics of matrix metalloproteinases (classification, structure, substrate specificity and regulation) and to report previous studies of intervertebral discs.

SUMMARY OF BACKGROUND DATA

Degeneration of the intervertebral disc, a probable prerequisite to disc herniation, is a complex phenomenon, and its physiopathologic course remains unclear. Matrix metalloproteinases probably play an important role but have received sparse attention in the literature.

METHODS

A systematic review of studies reporting a role of matrix metalloproteinases in intervertebral disc degeneration.

RESULTS

In several studies, investigators have reported the presence of proteolytic enzymes from disc culture systems and disc tissue extracts in degenerated human intervertebral discs, especially collagenase-1 (MMP-1) and stromelysin-1 (MMP-3). The matrix metalloproteinases are regulated by specific inhibitors (tissue inhibitors of metalloproteinases, or TIMPS), cytokines (interleukin-1), and growth factors.

CONCLUSIONS

This field of application is of particular interest because conventional treatments are disappointing in chronic low back pain. Clinical trials with specific inhibitors of metalloproteinases are beginning in osteoarthritis.

Phospholipase A2 sensitivity of the dorsal root and dorsal root ganglion

STUDY DESIGN

This study was designed to characterize the effects of phospholipase A2 on the neural response of dorsal root and dorsal root ganglion in the anesthetized New Zealand White rabbit.

OBJECTIVES

To examine the effects of phospholipase A2 on the neural response of somatosensory neurons at the dorsal root ganglion level.

SUMMARY OF BACKGROUND DATA

Phospholipase A2 may be an irritating component of disc tissue that is present in high concentration in painful herniated discs, in synovial fluids, and in sera of rheumatoid arthritis patients. Phospholipase A2 is inflammatory; however, its effects on dorsal roots and dorsal root ganglion response have never been demonstrated.

METHODS

Surgically isolated dorsal roots and dorsal root ganglia from New Zealand White rabbits were investigated by electrophysiologic techniques. Phospholipase A2 doses ranging from 100 to 400 U were applied on the mechanically sensitive segments of the dorsal root ganglia, and responses to varying doses were evaluated in relation to elapsed time.

RESULTS

The application of phospholipase A2 on the dorsal root ganglion resulted in possible neurotoxicity at doses more than 375 U, with no significant effect at lower doses except for recruitment of "silent units" at doses ranging from 200 to 340 U.

CONCLUSIONS

Phospholipase A2 doses comparable to serum concentrations in human rheumatoid arthritis appeared to be neurotoxic when applied to dorsal root ganglia. At lower doses, silent units become activated that were not active before the phospholipase A2 application. These results suggest that dorsal roots and dorsal root ganglion may be impaired by phospholipase A2, leading to sciatica and low back pain.

Murine nucleus pulposus-derived cells secrete interleukins-1-beta, -6, and -10 and granulocyte-macrophage colony-stimulating factor in cell culture

STUDY DESIGN

Cultures established from murine disc-derived cells were stimulated by lipopolysaccharide. The cells' capacity to secrete proinflammatory cytokines and interleukin-10 with and without lipopolysaccharide stimulation was determined using enzyme-linked immunosorbent assays.

OBJECTIVES

To determine the capacity of disc-derived cells to secrete proinflammatory cytokines, and the effect of lipopolysaccharide stimulation on such secretion.

SUMMARY OF BACKGROUND DATA

The pathophysiology of compressive radiculopathy is unclear. Inflammation is a possible explanation. Proinflammatory cytokine secretion was demonstrated in herniated nucleus pulposus. It is unknown whether these cytokines are secreted from disc-derived cells or from infiltrating inflammatory cells in the herniated nucleus pulposus.

METHODS

Discs were microsurgically harvested from inbred mice and cut to allow the nucleus pulposus to establish cell culture. A study group was exposed to lipopolysaccharide stimulation. Media were harvested from the study and control groups 24 hours later. Secretion of interleukins-1-, -6, and -10, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha were determined using enzyme-linked immunosorbent assays.

RESULTS

Basal secretion of interleukins-6 and -10, but no basal secretion of interleukin-1-, granulocyte-macrophage colony-stimulating factor, or tumor necrosis factor-alpha was detected. Secretion of interleukin-1- rose from zero to 27.69 pg/10(5) cells, and granulocyte-macrophage colony-stimulating factor secretion rose from zero to 9.77 pg/10(5) cells after lipopolysaccharide stimulation. A 75-fold increase in interleukin-6 secretion and a 150-fold increase in interleukin-10 secretion were detected after stimulation with lipopolysaccharide. No tumor necrosis factor-alpha secretion was detectable. All result had high statistical significance (all P < 0.001).

CONCLUSIONS

Cultured murine disc-derived cells have the capacity to secrete proinflammatory cytokines and interleukin-10 in the absence of inflammatory cells. This finding supports the hypothesis that disc-derived cells are capable of initiating or amplifying an inflammatory process.

Transpedicle instrumentation in the degenerative spine

Controversy continues regarding the use of pedicle instrumentation in fusion surgery on the degenerative lumbar spine. Recently, however, published reports are increasingly demonstrative of the positive effect of pedicle fixation on fusion and outcome success in the management of these disorders. Recent developments in surgical technique and implant design have improved operative risk and implant related complications. However, patient selection and demonstration of the underlying pathophysiology of degenerative lumbar motion segment pain remain 2 of the main challenges to clinical practice. The importance of well designed clinical studies are of paramount consequence in the solution of the existing controversies surrounding surgical treatment of the degenerative lumbar spine. Equally significant is the need to establish general and accepted measures of outcome to assess and compare treatment options. Combining study design and accepted outcome assessment will permit the resolution of the remaining controversies. The future of pedicle instrumentation of the degenerative lumbar spine is of necessity tied to the resolution of these remaining points of controversy-only thereafter can the current rate of advances continue.

Platelet-derived growth factor and vascular endothelial growth factor expression in disc herniation tissue: and immunohistochemical study

Angiogenesis is essential in tissue growth and regeneration. There are several factors that are able to stimulate vascular endothelial cell growth, including platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). Disc herniation tissue (DHT) contains vascular ingrowth, which promotes granulation tissue formation. In this study we observed 50 disc herniations for PDGF and VEGF immunoreactivity. PDGF immunopositivity was detected in 38 samples (78%). In 28 samples (56%) there were PDGF immunopositive capillaries, PDGF immunopositive disc cells were detected in 19 samples (38%) and PDGF immunopositive fibroblasts in 6 DHT samples (12%). VEGF immunopositive capillaries were identified in 44 DHT samples (88%). For neither growth factor was immunopositivity dependent on preoperative radicular pain duration. In extrusions (n = 25) VEGF immunopositive capillaries were detected in 23 samples (92%) and PDGF immunopositivity in 21 samples (84%). PDGF immunopositivity was more commonly associated with capillaries than with nuclei of disc cells. In sequesters (n = 20) VEGF immunopositive capillaries were identified in all samples and PDGF immunopositivity in 16 (80%). As in extrusions, PDGF immunoreaction was more prevalent in capillaries than in disc cells. Patient age did not relate to VEGF expression. In all age groups it was higher than 80%. Thus capillaries in disc herniation tissue are evidently newly formed and our results demonstrate that PDGF and VEGF participate in the neovascularization process. The presence of PDGF in fibroblasts and in disc cells suggests that this growth factor regulates the function of these cells, possibly the proliferation of the cells and the production of extracellular matrix components.

Prostaglandin production after experimental discectomy

STUDY DESIGN

This study ascertained the effects of discectomy on prostaglandin synthesis.

OBJECTIVES

The purpose of these novel experiments was to measure the levels of two prostaglandins in lumbar epidural fluid obtained from an area subjected to discectomy. For comparison, lumbar epidural fluid from a site not disturbed by discectomy and fluid from a subcutaneous site were analyzed for the prostaglandins.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that nuclear material obtained from degenerative discs manifests an extraordinarily high level of phospholipase A2 activity. Others have hypothesized that the known inflammatory effects of phospholipase A2 are due to the release of arachidonic acid, which is converted to various eicosanoids, including several algesic prostaglandins (PGI2 and PGE2). No previous study has continuously measured prostaglandin levels in epidural fluid or assessed the effect of discectomy on prostaglandin production.

METHODS

An ultrafiltrate of lumbar epidural fluid of dogs was obtained from indwelling catheters located adjacent to spinal areas that were and were not subjected to discectomy as well as from subcutaneous tissue. The fluid was collected daily for 14 days and analyzed for PGE2 and 6-keto PGF1(alpha) (the stable metabolite of PGI2) by radioimmunoassay.

RESULTS

The concentration of 6-keto PGF1(alpha) and PGE2 in fluid collected during the first 24 hours was significantly higher in the area of discectomy than in the epidural region that was not subjected to discectomy and significantly higher than in fluid obtained from the subcutaneous site. The high level of these prostaglandins at the discectomy site fell rapidly, so that by the end of 48 hours the differences in values between spinal fluid from the discectomy and nondiscectomy regions were not statistically significant. The concentration of the prostaglandins in epidural fluid decreased with time and became minimal within the second week.

CONCLUSION

The removal of normal discs is accompanied for 24 hours by a marked rise in the synthesis of two prostaglandins known to produce pain. Because the concentration of prostaglandins in epidural fluid decreased rapidly thereafter, the initial surge obtained appears to be associated more with chemical factors such as phospholipase A2 than with wound healing.

The results of operations on the lumbar spine in patients who have diabetes mellitus

The results for sixty-two patients who had had a diagnosis of diabetes mellitus and lumbar disc disease or spinal stenosis and had been managed with a posterior decompressive procedure were compared, in a retrospective study, with those for sixty-two age and sex-matched non-diabetic (control) patients who had had similar operative procedures. Forty-four of the sixty-two diabetic patients and fifty-five of the non-diabetic patients were available for long-term follow-up (mean, five and seven years, respectively). Among the diabetic patients, there were high rates of postoperative infection and prolonged hospitalization compared with the rates for the control group. The long-term result was excellent or good for seventeen (39 per cent) of the forty-four patients who had diabetes mellitus and for fifty-two (95 per cent) of the fifty-five non-diabetic patients. The poor results in the diabetic patients may have been related to coexisting diabetic neuropathy, to the associated microvascular disease that affects the spinal nerve roots in diabetic patients, or to the failure of the nerve roots of these patients to recover after decompressive procedures.

The serine proteinase inhibitory proteins of the human intervertebral disc: their isolation, characterization and variation with ageing and degeneration

Serine proteinase inhibitory proteins (SPIs) were extracted from human disc tissues using 2 M GuHCl and subjected to CsCl density gradient ultracentrifugation. The SPIs recovered in the low buoyant density fractions (rho < or = 1.35 g/ml) were purified by a combination of gel-permeation, ion-exchange, trypsin affinity, and reverse-phase high performance chromatographies. Characterisation of the major disc SPI by polyacrylamide gel electrophoresis, isoelectric focussing, enzyme inhibition and pH stability studies indicated that this small molecular weight (12-14 kDa), highly basic (pI > 9.5), acid-stable but alkaline-labile protein possessed potent inhibitory activity against bovine pancreatic trypsin and chymotrypsin, and human leukocyte elastase and cathepsin G. Two-major and two-minor low molecular weight cationic SPI species were identified by reverse-phase HPLC. The predominant species was identical to a human articular cartilage SPI sharing amino terminal sequence homology with the mucus proteinase inhibitors (MPIs). It also cross-reacted with an antiserum to the MPIs and behaved identically to secretory leucocyte proteinase inhibitor (SLPI) when examined by reverse phase HPLC, and SDS PAGE. A higher molecular weight (54 kDa), anionic (pI approximately 4.6) SPI was also purified and identified as alpha 1-proteinase inhibitor (alpha 1-PI). Quantification of alpha 1-PI and the small molecular weight cationic disc inhibitors indicated that the latter were depleted in morphologically degenerate disc tissues while levels of alpha 1-PI were somewhat higher although a large proportion of the alpha 1-PI was inactive. A depletion of total SPI levels was evident overall in degenerate discs suggesting a functional role for these inhibitory proteins in the maintenance of IVD matrix homeostasis.

Isolation and characterisation of a neutral proteinase from the canine intervertebral disc

A neutral proteinase of 94 kDa capable of degrading gelatin, canine disc proteoglycan, and L-lysine and L-arginine peptide substrates has been isolated from the greyhound intervertebral disc. Strong inhibition of this proteinase with class-specific inhibitors, such as APMSF, TLCK and benzamidine indicated a 'serine'-type specificity. Metallo, aspartyl- and cysteine proteinase inhibitors were devoid of significant action. Degradation of the resident canine disc proteoglycan monomer by the disc proteinase was shown to occur at the hyaluronic acid binding region, thereby diminishing its ability to aggregate with hyaluronic acid. The hydrodynamic size of the proteoglycan degradation products was only slightly less than that of the intact disc proteoglycan subunits.

Intrarater and interrater reliability of strength measurements of the biceps and deltoid using a hand held dynamometer

This study reports the intrarater and interrater reliability of measurements for elbow flexion (biceps) and shoulder abduction (deltoid) in 27 normal subjects. Testing was done by two physical therapy examiners. For each muscle group tested, the first series of three tests were administered according to the general guidelines described in the dynamometer administration manual and then repeated with increased stabilization procedures (i.e., examiner elbow stabilized against the anterior superior spine). Intrarater and interrater reliability were highest when tested with the examiner elbow stabilized. Intrarater reliability coefficients were in an acceptable range both with and without additional stabilization (0.833 to 0.957) but interrater reliability coefficients were more variable, ranging from a low of 0.518 to a high of 0.840. Mean muscle strength measurements were significantly different between the two examiners. More studies are needed to improve interrater reliability when estimating muscle strength with the hand held dynamometer.J Orthop Sports Phys Ther 1988;9(12):395-398.