Long-term outcome of targeted therapy for low back pain in elderly degenerative lumbar scoliosis.

PURPOSE: Treatment of low back pain (LBP) associated with elderly degenerative lumbar scoliosis (DLS) remains controversial. We have developed percutaneous intervertebral-vacuum polymethylmethacrylate injection (PIPI) targeting to the intervertebral vacuum as a minimally invasive surgery. The present study compared the long-term clinical outcomes of PIPI to that of nonoperative treatment. METHODS: Patients with de novo DLS, aged ≥ 65 years, who had LBP with visual analog scale (VAS) of ≥ 50 for ≥ 6 months with intervertebral vacuum on computed tomography and bone marrow edema (BME) on magnetic resonance imaging were included. The clinical outcomes were evaluated using VAS and the Oswestry Disability Index (ODI) at baseline, 1, 6, 12, 24 months, and at the final follow-up. The course of BME was also evaluated. RESULTS: One hundred and one patients underwent PIPI and 61 received nonoperative treatment. The mean follow-up duration after PIPI and nonoperative treatment was 63.7 ± 32.4 and 43.9 ± 20.9 months, respectively. VAS and ODI after PIPI were significantly improved compared to post-nonoperative treatment. BME decreased substantially in the PIPI group and it was significantly correlated with VAS and ODI improvement. Following PIPI, LBP recurred in 28 patients (35%). LBP recurrence was identified at the same level of PIPI in 10 patients, at the adjacent level of PIPI in 11 patients, and at the non-adjacent level of PIPI in seven patients. Eighteen patients underwent additional PIPIs, and both VAS and ODI were significantly improved after additional PIPIs. CONCLUSION: Bone marrow lesions of the endplate are strongly associated with the presence of LBP. PIPI can be considered as an effective, safe and repeatable treatment for LBP in elderly DLS patients.

Structural Analysis of Experimentally Induced Disc Herniation-Like Changes in the Rat.

INTRODUCTION: A disc herniation has traditionally been considered as disc tissue that has slipped out from an intervertebral disc. However, it was recently suggested that the disc herniation mass is a product of bioactive substances from the disc and that the disc hernia would more likely be scar tissue than herniated disc material. In this study, we aimed to analyze the structural components of experimentally induced disc herniations and compare with scar tissue and nucleus pulposus, in the rat. METHODS: Twenty-eight rats had their L4-5 discs punctured. After three weeks, the nodule that had been formed over the puncture site, scar tissue from the spine musculature, and normal nucleus pulposus were harvested and processed for further analysis. RESULTS: Proteomics analysis demonstrated that the formed nodule was more similar to scar tissue than to nucleus pulposus. Gene expression analysis showed that there was no resemblance between any tissues when looking at inflammatory genes but that, there was a clear resemblance between the nodule and scar tissue when analyzing extracellular matrix-related genes. Analysis of the GAG and polysaccharide size distribution revealed that only the nodule and scar tissue contained the shorter versions, potentially short chain hyaluronic acid that is known to induce inflammatory responses. The hematoxylin and eosin stained sections of the nodule, disc tissue, and scar tissue indicated that the morphology of the nodule and scar tissue was very similar. CONCLUSIONS: The nodule formed after experimental disc puncture, and that resembles a disc hernia, has a more structural resemblance to scar tissue than disc tissue. The nodule is, therefore, more likely to be induced by disc-derived bioactive substances than being formed by herniated disc material.

Bone Marrow Edema and Low Back Pain in Elderly Degenerative Lumbar Scoliosis: A Cross-Sectional Study.

STUDY DESIGN: Cross-sectional study. OBJECTIVE: To examine whether bone marrow edema is associated with low back pain in elderly patients with degenerative lumbar scoliosis. SUMMARY OF BACKGROUND DATA: The cause of low back pain in degenerative lumbar scoliosis is unclear. METHODS: A total of 120 degenerative lumbar scoliosis patients 65 years of age or older were evaluated. Radiography, computed tomography (CT), magnetic resonance imaging (MRI), and tender point examination in the lumbar spine were performed. On MRI, coronal gadolinium-contrasted T1- or T2-weighed fat-saturated images were used to score the size of bone marrow edema. The prevalence of bone marrow edema in patients with and without low back pain was compared; in patients with low back pain, we tested whether the locations of lumbar tender point were consistent with that of bone marrow edema. RESULTS: Bone marrow edema was found in 62 of 64 (96.9%) patients with low back pain compared with 21 of 56 (37.5%) patients without it (P < 0.001). Bone marrow edema located more frequently on the concave side than on the convex side of scoliosis (P < 0.001). Among patients with low back pain, bone marrow edema score was associated with low back pain severity (r = 0.724; P < 0.001), and the location of lumbar tender point were consistent with that of bone marrow edema (κ value = 0.745; P < 0.001). CONCLUSION: Bone marrow edema on MRI was closely associated with the presence of low back pain in elderly degenerative lumbar scoliosis. LEVEL OF EVIDENCE: 4.

Experimental Disc Herniation in the Rat Causes Downregulation of Serotonin Receptor 2c in a TNF-dependent Manner.

BACKGROUND: During recent decades, the knowledge of the pathophysiology of disc herniation and sciatica has drastically improved. What previously was considered a strict biomechanical process is now considered a more complex interaction between leaked nucleus pulposus and the tissue in the spinal canal. An inflammatory reaction, with tumor necrosis factor (TNF) playing an essential role, has been demonstrated. However, the exact mechanisms of the pathophysiology of disc herniation remain unknown. QUESTIONS/PURPOSES: In this study we use an animal model to investigate (1) if and/or how experimental disc herniation affects gene expression in the early phase (24 hours postsurgery) in the dorsal root ganglion; and (2) if TNF inhibition can reduce any observed changes. METHODS: A rat model of disc herniation was used. Twenty rats were evenly divided into four groups: naïve, sham, disc herniation, and disc herniation with TNF inhibition. The dorsal root ganglion of the affected nerve root was harvested 24 hours after surgery and analyzed with a TaqMan Low Density Array(®) quantitative polymerase chain reaction assay. Gene expression levels in sham were compared with disc herniation to assess question 1 and disc herniation to disc herniation with TNF inhibition to assess question 2. RESULTS: Experimental disc herniation caused a decrease in the expression of the serotonin receptor 2c gene (p = 0.022). TNF inhibition was found to reduce the observed decrease in expression of serotonin receptor 2c (p = 0.037). CONCLUSIONS: Our results suggest that a decrease in the expression of the serotonin receptor 2c gene may contribute to the pathophysiology of disc herniation. Further research on its involvement is warranted. CLINICAL RELEVANCE: This pilot study gives a brief insight into cellular changes that may contribute to the pathophysiology of disc herniation. This knowledge may contribute to the development of more and better treatment options for patients with disc herniation and sciatica.

Increase of sodium channels (nav 1.8 and nav 1.9) in rat dorsal root ganglion neurons exposed to autologous nucleus pulposus.

PURPOSE: It has been assumed that nucleus pulposus-induced activation of the dorsal root ganglion (DRG) may be related to an activation of sodium channels in the DRG neurons. In this study we assessed the expression of Nav 1.8 and Nav 1.9 following disc puncture. METHOD: Thirty female Sprague-Dawley rats were used. The L4/L5 disc was punctured by a needle (n=12) and compared to a sham group without disc puncture (n=12) and a naive group (n=6). At day 1 and 7, sections of the left L4 DRG were immunostained with anti-Nav 1.8 and Nav 1.9 antibodies. RESULT: At day 1 after surgery, both Nav 1.8-IR neurons and Nav 1.9-IR neurons were significantly increased in the disc puncture group compared to the sham and naive groups (p<0.05), but not at day 7. CONCLUSION: The findings in the present study demonstrate a neuronal mechanism that may be of importance in the pathophysiology of sciatic pain in disc herniation.

Effect of lactoferrin peptide (PXL01) on rabbit digit mobility after flexor tendon repair.

PURPOSE: Restoration of digital function after flexor tendon injuries remains a clinical challenge. Complications such as adhesion formation and tendon rupture can lead to limited hand function. The aim of this study was to compare the effects of the lactoferrin-derived peptide, PXL01, formulated in sodium hyaluronate (SH), with SH alone on joint mobility as an indirect measure of postsurgical adhesion prevention and healing strength of the tendon and to elucidate the most optimal concentration of PXL01. METHODS: Using a rabbit flexor tendon repair model, in which the deep flexor tendon was fully transected and repaired, PXL01 in SH or SH alone was administered between the repaired tendon and the tendon sheath before closure of the surgical wound. Three concentrations of PXL01 in SH (5, 20, or 40 mg/mL) were compared to determine the lowest effective concentration. The repaired tendons were evaluated 7 weeks after surgery by measuring the proximal interphalangeal joint mobility by full range of flexion assessment and the tendon repair strength. RESULTS: Treatment with PXL01 formulated in SH resulted in improved mobility of the proximal interphalangeal joint with an average of 10°, corresponding to improvement of approximately 25% to 60% of the flexion of nonoperated toes at the different measuring points compared with SH alone. The difference was statistically significant in 5 out of 6 measuring points (0.5, 1, 2, 3, and 4 N; P < .05). The dose-response study indicated that the lowest effective concentration of PXL01 was 20 mg/mL. There was no difference in healing strength of the tendon between the groups as assessed by load-to-failure breaking strength. CONCLUSIONS: PXL01 in SH significantly improved the mobility compared with the carrier SH alone, without any negative effect on healing strength, and PXL01 at 20 mg/mL was the lowest effective concentration. CLINICAL RELEVANCE: The result provides a valuable basis for a clinical trial to assess efficacy and safety of PXL01 in clinical hand surgery.

Local application of nucleus pulposus induces expression OF P2X3 in rat dorsal root ganglion cells.

The P2X(3) receptor is a ligand-gated cation channel that is activated by extra cellular adenosine triphosphate (ATP) found in the dorsal root, trigeminal and nodose ganglia. It is one of the receptors transmitting nociceptive information of injuries and inflammation of the periphery by endogenous ATP released from damaged cells. The present study was performed in order to evaluate if there was an increased expression of P2X(3)-immunoreactivity in dorsal root ganglion (DRG) neurons after experimental disc herniation. There were four groups: exposure of the left L4 dorsal root ganglion and incision of the L4-L5 disc, exposure and slight displacement of the left L4 dorsal ganglion, sham exposure of the L4 dorsal root ganglion, and normal. Seven days after surgery, the DRG's were collected, sectioned and stained immunohistochemically for the P2X(3) receptor. The expression of P2X(3) increased significantly following incision of the L4-5 disc compared to the normal group. Sham surgery induced a minor, although statistically significant increase. Mechanical displacement did not induce any increased expression of the receptors. The study demonstrates that expression of the P2X(3)receptors in the DRG may be induced by local application of nucleus pulposus. This may increase our understanding of the pathophysiologic mechanisms related to disc herniation and sciatica.

Pain behavior changes following disc puncture relate to nucleus pulposus rather than to the disc injury per se: an experimental study in rats.

It has previously been demonstrated that disc puncture in the rat induced changes in grooming and wet dog shakes, two behavioral changes that may be linked to discomfort and neuropathic pain. In this study the aim was to separate the effects of disc injury and the epidural presence of nucleus pulposus. Following anesthesia, the L4-5 disc was exposed using a dorsal approach. Ten rats received a superficial disc injury without nucleus pulposus leakage and ten rats received nucleus pulposus from a donor rat without disc injury. In ten animals the L4-5 disc was punctured using a ventral approach, with 10 corresponding controls. Spontaneous behavior was assessed after surgery. The data was matched to historical control of dorsal sham surgery and disc puncture. The study showed that the effects of nucleus pulposus were more pronounced than the effects induced by the disc injury. Ventral disc puncture did not induce any behavioral changes different from sham exposure. In conclusion, the data from the study indicate that behavioral changes induced by disc puncture are more likely to relate to the epidural presence of nucleus pulposus than the disc injury per se.

Local application of interleukin-6 to the dorsal root ganglion induces tumor necrosis factor-α in the dorsal root ganglion and results in apoptosis of the dorsal root ganglion cells.

STUDY DESIGN: The mechanisms of apoptosis behind the formation of tissue reactions at the surface of the dorsal root ganglion (DRG) exposed to the nucleus pulposus were studied with special reference to the role of interleukin-6 (IL-6), using electron microscopy and immunohistochemistry in rats. OBJECTIVE: To study the role of IL-6 on the DRG. SUMMARY OF BACKGROUND DATA: It has been reported that nucleus pulposus cells are capable to produce proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and IL-6. Recently, it was observed that local application of nucleus pulposus induced a characteristic tissue reaction at the surface of the DRG. This change was due to apoptosis of DRG neurons. However, the role of IL-6 is not known regarding the apoptosis of the DRG neurons. METHODS: Recombinant IL-6 was applied between the L4 DRG and the dura to mimic a disc herniation of the L4-L5 disc in rats. The L4 DRGs were resected 24 hours after surgery. The sections were processed for immunohistochemistry using antisera to TNF-α. Furthermore, the sections of the specimens were observed using light and electron microscopy to confirm the induced apoptosis of the DRG neurons. The sections were also processed for immunohistochemistry, using antisera to single-stranded DNA (ssDNA) and Caspase 3. RESULTS: TNF-α immunoreactivity was observed in the peripheral area of DRG at the site of the application of IL-6. Typical changes of the cell nuclei were observed in the DRG by light and electron microscopy, indicating the presence of apoptosis. The presence of ssDNA and Caspase 3 further enhanced the impression that there was apoptosis of the DRG neurons. CONCLUSION: IL-6 seemed to induce TNF-α at the surface of DRG exposed to IL-6 and to induce a characteristic reaction at the surface of the DRG. IL-6 may thus play an important role in nucleus pulposus-induced apoptosis of the DRG neurons as well as TNF-α.

Pharmacological inhibition of tumor necrosis factor may reduce pain behavior changes induced by experimental disc puncture in the rat: an experimental study in rats.

STUDY DESIGN: Pain behavior assessment in rats following disc puncture (DP) and simultaneous tumor necrosis factor (TNF) inhibition. OBJECTIVE: To assess if treatment with TNF inhibition could reduce the pain behavior changes induced by DP in the rat. SUMMARY OF BACKGROUND DATA: Anular tears with leakage of nucleus pulposus have been suggested to be one possible cause of low back pain (LBP). In an experimental model, it was recently shown that DP might induce specific pain behavior changes. The aim of the present study was to a study if inhibition of TNF might reduce such pain behavior changes. METHODS: Sixty rats underwent facetectomy and puncture of the fourth lumbar disc. The rats were simultaneously treated with doxycycline locally at 0.3 and 3.0 mg/kg and systemically at 3.0 mg/kg, or infliximab locally at 0.5 and 5.0 mg/kg, and systemically at 5.0 mg/kg, (n ∇ 10 for each subseries). The rats were videotaped at 1, 3, 7, 14, and 21 days after surgery. The videos were analyzed regarding presence of wet-dog shakes (WDS). Data from a previous study with sham surgery and DP without treatment were included for comparison. RESULTS: All groups treated with doxycycline resulted in a statistically significant reduction of WDS compared to the group without treatment (DP). In infliximab treated animals, WDS decreased with statistically significance compared to the nontreated DP group at all analyzed days except for the group with high dose local treatment where a statistically significant reduction was obtained only at days 14 and 21. CONCLUSION: The present study showed that TNF inhibition induced a marked reduction of wet dog shakes. It is not fully understood if wet-dog shakes may relate to LBP, but in view of recent clinical findings one may consider clinical studies of TNF inhibition for the treatment of LBP.

Reduction of adhesion formation and promotion of wound healing after laminectomy by pharmacological inhibition of pro-inflammatory cytokines: an experimental study in the rat.

In a previous experiment using TNF inhibition in the rat it was accidentally found that adhesion and scar formation was reduced compared to previous experience. Wound and bone healing also seemed enhanced. The present study was conducted to assess if this observation could be verified in a controlled setting using a standardized laminectomy in the rat. Five rats received doxycycline and five other rats received saline and served as control. Macroscopic blinded evaluation 1 week after the laminectomy revealed that adhesion and scar formation was less in doxycycline-treated animals than in control animals. Wound and bone healing was found to be better in doxycycline-treated animals. The mechanisms for the observed effects cannot be fully understood but the data indicate that further research may lead to opportunities to design pharmacological modalities to reduce adhesion and scar formation, maybe in combination with suitable barriers.

Model for assessment of mobility of toes and healing of tendons in rabbits.

Repair of a transected flexor tendon will, despite careful technique and early rehabilitation, usually result in a restricted range of movement. This is mainly because adhesions form between the tendon and the surrounding structures. Our aim was to establish an experimental model in rabbits for future studies on new techniques to reduce the formation of adhesions after zone II repair of flexor tendons. In rabbits' hind paws the metatarsal bones II, IV, and V were removed and the flexor tendon was freed to the metatarsophalangeal (MTP) joint. The digits were secured in a specifically-designed biomechanical testing device comprising a servo-hydraulic actuator that was designed to apply controlled force or displacement. The tests were videotaped with a digital force-monitor behind the tested digit. Paper printouts from the recordings were obtained for 0, 0.5, 1, 2, 3, 4, and 5 Newton (N) and metatarsophalangeal, proximal interphalangeal, and distal interphalangeal, angles and distances between metatarsophalangeal joints and claws were measured. The tensile strength of the tendon was evaluated by a load-to-failure test. The continuous data obtained from the experiments were used to calculate functional stiffness at the selected forces. The model allows for unique continuous recordings of mobility of toes, thereby indirectly quantifying the presence of adhesions and the assessment of tensile strength. The data are reproducible, and there is little variation between the digits tested. The model is primarily intended to compare data among treated and non-treated digits of methods to limit the formation of adhesions after tendons have been repaired.

A novel polypeptide derived from human lactoferrin in sodium hyaluronate prevents postsurgical adhesion formation in the rat.

OBJECTIVE: The objective of the study was to evaluate whether a peptide derived from human lactoferrin, PXL01 could act safely to reduce the formation of peritoneal adhesions in the rat model and to map the molecular mechanisms of its action. SUMMARY BACKGROUND DATA: Adhesion formation is a significant problem within every surgical discipline causing suffering for the patients and major cost for the society. For many decades, attempts have been made to reduce postsurgical adhesions by reducing surgical trauma. It is now believed that major improvements in adhesion prevention will only be reached by developing dedicated antiscarring products, which are administrated in connection to the surgical intervention. METHODS: Anti-inflammatory as well as fibrinolytic activities of PXL01 were studied in relevant human cell lines. Using the sidewall defect-cecum abrasion model in the rat, the adhesion prevention properties of PXL01 formulated in sodium hyaluronate were evaluated. Large bowel anastomosis healing model in the rat was applied to study if PXL01 would have any negative effects on intestine healing. RESULTS: PXL01 exhibits an inhibitory effect on the most important hallmarks of scar formation by reducing infections, prohibiting inflammation, and promoting fibrinolysis. PXL01 formulated in sodium hyaluronate markedly reduced formation of peritoneal adhesions in rat without any adverse effects on wound healing. CONCLUSIONS: A new class of synthetically derived water soluble low molecular weight peptide compound, PXL01 showed marked reduction of peritoneal adhesion formation in an animal model without any negative effects on healing. On the basis of these data, a comprehensive adhesion prevention regimen in clinical situation is expected.

Puncture of a lumbar intervertebral disc induces changes in spontaneous pain behavior: an experimental study in rats.

STUDY DESIGN: Changes in spontaneous behavior was studied in rats after a controlled puncture of a lumbar intervertebral disc. OBJECTIVE: To study if puncture of a lumbar disc would induce recordable changes in spontaneous pain behavior. SUMMARY OF BACKGROUND DATA: Anular tears are common and may be found both in patients with low back pain and in asymptomatic patients. It has been suggested that anular injury may relate to low back pain either by stimulation of local sensory receptors in the posterior part of the anulus fibrosus or by ingrowth of newly formed nerve fibers into the deeper parts of the disc. The objective of the study was to analyze if a controlled puncture of a lumbar intervertebral disc might induce recordable changes in spontaneous behavior of rats. METHODS: After anesthesia, the L4-L5 disc was punctured in 10 rats. Ten other rats received sham surgery. Spontaneous behavior was assessed at days 1, 3, 7, 14, and 21 after surgery. RESULTS: Statistically significant differences in behavior were seen at all days analyzed. Most consistent were increases in "grooming" and in "wet-dog shakes." CONCLUSION: Puncture of a lumbar intervertebral disc in the rat produces changes in spontaneous behavior mainly seen as increased "grooming" and "wet-dog shakes," 2 behaviors that have been suggested to indicate stress and pain.

The role of tumor necrosis factor-alpha in apoptosis of dorsal root ganglion cells induced by herniated nucleus pulposus in rats.

STUDY DESIGN: The mechanisms of apoptosis underlying a characteristic tissue reaction at the surface of the dorsal root ganglion (DRG) exposed to nucleus pulposus were studied in rats with special reference to the role of tumor necrosis factor-alpha (TNF). OBJECTIVE: To study the characteristic tissue reaction at the surface of the DRG exposed to nucleus pulposus with special reference to the role of TNF. SUMMARY OF BACKGROUND DATA: Nucleus pulposus cells are capable of producing TNF. Recently, local application of nucleus pulposus was shown to induce a characteristic tissue reaction at the DRG surface due to apoptosis. METHODS: Recombinant TNF was applied to the DRG to mimic L4-L5 disc herniation in rats. The DRGs were resected 24 hours after surgery. Sections of the specimens were processed for immunohistochemistry using antisera to single-stranded DNA, Caspase 3, and TNF, and observed by light and electron microscopy. RESULTS: Typical apoptotic changes of the cell nuclei were observed in the DRG after application of TNF. The presence of single-stranded DNA, Caspase 3, and TNF further confirmed the occurrence of DRG cell apoptosis. CONCLUSION: TNF seemed to play a key role in induction of apoptosis of DRG cells, which resembled that induced by application of nucleus pulposus.

Production of tumor necrosis factor-alpha from porcine nucleus pulposus cells at various time points in cell culture under conditions of nutritional deficiency.

Nucleus pulposus (NP) in the epidural space induces spinal nerve damage not only by mechanical but also chemical mechanism. NP has been shown to be capable of producing tumor necrosis factor-alpha (TNF). TNF may play key roles in the NP-induced chemical damage. One of the main pathways to reach the avascular NP is diffusion from the blood supply of the vertebral body through the cartilage endplate. On disk herniation, when NP moves to the epidural space, the distance from the endplate to the herniated NP are longer in the herniated disk than in the intact disk. That is, it seems more difficult to receive adequate nutritional supply from the endplate in the sequestrated type. However, there have been only a few reports of the appearance of TNF in NP. The present study was performed to investigate TNF production in porcine NP under conditions of nutritional deficiency. NP cells were cultured and processed for immunohistochemistry using antisera to TNF, and for ELISA to measure TNF production. The latter was compared longitudinally. The immunoreactivity increased over time. On the other hand, the results of ELISA showed a peak in TNF production 12h, and lower amounts 1 day and 2 days after application of PBS. These observations may suggest that a nutritional deficit is a possible turn-on switch for TNF up-regulation in the NP.

Changes in pain behavior and histologic changes caused by application of tumor necrosis factor-alpha to the dorsal root ganglion in rats.

STUDY DESIGN: Histologic changes in the dorsal root ganglion (DRG) and the nociceptive stimulation thresholds were studied in rats. OBJECTIVE: To examine the effects of tumor necrosis factor-alpha (TNF) with special reference to pain behavior and histology of the DRG. SUMMARY OF BACKGROUND DATA: Recently, it was reported that local application of nucleus pulposus induces a characteristic tissue reaction at the surface of the DRG. However, to our knowledge, there have been no previous reports about the relationship between the histologic changes and pain behavior caused by cytokines. METHODS: Recombinant TNF was applied to the L4 DRG. Mechanical and thermal nociceptive thresholds were tested. The L4 DRG was sectioned and observed by light microscopy. RESULTS: After the application of 5 ng/microL TNF, significant differences were observed in mechanical and thermal stimulation thresholds. At the site of application of TNF, a characteristic a semilunar-shaped enlargement was observed. The average width of the part was significantly larger in the 5 ng/microL TNF application, as compared to the 0.5-ng/microL TNF application. CONCLUSIONS: The higher concentration of TNF used induced allodynia and hyperalgesia responses. Because the region showing the histologic changes was significantly larger after application of the higher concentration of TNF, the reaction of the DRG may be related to pain.

Nucleus pulposus-induced apoptosis in dorsal root ganglion following experimental disc herniation in rats.

STUDY DESIGN: The mechanisms behind the formation of a characteristic tissue reaction at the surface of the dorsal root ganglion (DRG) exposed to nucleus pulposus was studied with special reference to apoptosis using electron microscopy and immunohistochemistry in rats. OBJECTIVES: To study the mechanism of the characteristic tissue reaction at the surface of the DRG exposed to nucleus pulposus. SUMMARY OF BACKGROUND DATA: Recently, it was observed that local application of nucleus pulposus may induce a characteristic tissue reaction at the surface of the DRG. This change occurred as early as 1 day after the application of nucleus pulposus. METHODS.: Herniation of nucleus pulposus was created in the L4-L5 disc in rats. The L4 DRG were resected 3 and 24 hours after surgery. The sections of the specimens were observed using light and electron microscopy. The sections were processed for immunohistochemistry using antibodies to single-stranded DNA (ssDNA), caspase 3, and tumor necrosis factor alpha (TNF). RESULTS: There were typical changes of the cell nuclei observed by light and electron microscopy, especially those of the small-sized cells, in the DRG 24 hours after application of nucleus pulposus, indicating the presence of apoptosis. The presence of ssDNA, caspase 3, and TNF further enhanced the impression that there was apoptosis in the DRG. Nucleus pulposus induced apoptosis in the DRG at the site of application within as little as 24 hours. CONCLUSIONS: Nucleus pulposus herniated from the disc induced apoptosis in at the surface of the DRG exposed to nucleus pulpous as early as 24 hours after exposure.

Effects of lumbar sympathectomy on pain behavioral changes caused by nucleus pulposus-induced spinal nerve damage in rats.

It has been suggested that lumbar sympathectomy can reduce pain behavior, including mechanical allodynia and thermal hyperalgesia, caused by ligation of the spinal nerve. One well-characterized model, which involves application of nucleus pulposus to the spinal nerve and displacement of the adjacent nerve, shows behavioral changes in rats. However, there have been no previous reports regarding sympathectomy performed in this model. Disk incision and adjacent spinal nerve displacement were performed with (n=6) or without (n=6) sympathectomy. Sham surgery was also performed with (n=6) or without (n=6) sympathectomy. The animals were tested for 3 days before surgery and on days 1, 3, 7, 14, and 21 after surgery. Non-noxious mechanical thresholds were tested by determining the hind paw withdrawal response to von Frey hair stimulation of the plantar surface of the footpad using a touch stimulator. Thermal nociceptive thresholds were tested using a sensitive thermal-testing device. While rats in the disk incision with displacement surgery group showed allodynia and hyperalgesia after surgery on the experimental side, sympathectomized animals did not. No allodynia was observed in the sham groups. Sympathectomy seemed to prevent the pain behavioral changes caused by the combination of disk incision and nerve displacement.

Incision of the intervertebral disc induces disintegration and increases permeability of the dorsal root ganglion capsule.

STUDY DESIGN: The origin and the barrier properties of the characteristic reaction at the surface of the dorsal root ganglion (DRG) exposed to the nucleus pulposus was studied using Alcian-Blue staining, van Gieson staining, and the application of Evans Blue Albumin (EBA) complex in rats. OBJECTIVE: To study the origin and the barrier properties of the capsule, including the characteristic reaction, at the surface of the DRG exposed to the nucleus pulposus. SUMMARY OF BACKGROUND DATA: Local application of nucleus pulposus may induce a characteristic reaction at the surface of the DRG. This reaction histologically resembles an acute inflammatory reaction. However, it is not evident if this is a swelling of the DRG capsule, if it is located between the capsule and neurons of the DRG, or if it is only an attached nucleus pulposus. METHODS: Nucleus pulposus from the discs was obtained. The nucleus pulposus was smeared on glass slides. Alcian-Blue with hematoxylin and eosin staining was performed for each smear. Herniation of the nucleus pulposus was made in the L4-L5 disc in rats. The L4 DRGs were resected 3, 24, and 72 hours after surgery, and sectioned. The sections were processed for Alcian-Blue staining, van Gieson staining, and EBA complex infiltration. The sections were observed using light or fluorescent microscopy. RESULTS: Smear of nucleus pulposus was stained bright blue indicating mucins. A characteristic reaction, "inflammatory crescent," was confirmed at the surface of the DRG exposed to the nucleus pulposus. No mucins were observed in the crescent using Alcian-Blue. The results of van Gieson staining showed that the reaction started both inside and outside the elastic fiber layer, the DRG capsule, within 3 hours. The EBA complex was capable of infiltrating into the DRG capsule 24 hours after disc incision. CONCLUSIONS: The disintegrated capsule showed an increased permeability even for a large molecule as albumin, which indicates a possible entrance route for various substances induced by locally applied nucleus pulposus.