Alaska Pollock-derived Gelatin Sealant has Higher Sealing Strength than, and Comparable Biocompatibility with, Fibrin Sealant in Porcine and Rat Dural Injury Models.

STUDY DESIGN: Burst strength study in porcine dural models and functional and histological study in rat dural models. OBJECTIVE: This study aimed to investigate the sealing strength and biocompatibility of Alaska pollock-derived gelatin (ApGltn) and fibrin sealants in disrupted dural injuries. SUMMARY OF BACKGROUND DATA: Disruption of the dura mater occurs during spine surgery, leading to cerebrospinal fluid leakage. Fibrin sealant is usually applied to ruptured sites; however, it lacks sealing strength. A novel biocompatible sealant composed of ApGltn was recently demonstrated to have good burst strength and biocompatibility in the porcine aorta. METHODS: Ten porcine dura maters with central holes were covered with ApGltn and fibrin sealants (five samples per group). The maximum burst strength of each sealant was measured, and histological examination was performed after burst testing. Twenty-seven dura maters of male Wistar rats were used for functional and histopathological evaluations. The rats were treated with three surgical interventions: defect + ApGltn sealant; defect + fibrin sealant; defect alone (nine rats per group). Macroscopic confirmation of the sealant, hindlimb motor function analysis, and histopathological examination were performed at two, four, and eight weeks after the procedure. RESULTS: The maximum burst strength of the ApGltn sealant was ~4.4 times higher than that of the fibrin sealant (68.1±12.1 vs . 15.6±8.7 mmHg; P <0.001). Histological examination confirmed that the ApGltn sealant showed tight adhesion to the dural surface, whereas a gap was observed between the fibrin sealant and the dura mater. In the rat model, the ApGltn sealant resulted in spinal function and dural histological findings similar to those of the fibrin sealant. CONCLUSION: The ApGltn sealant had a higher sealing strength than, and comparable effect on dura regeneration with, the fibrin sealant.

Extramedullary Hematopoiesis in the Dura Mater During Treatment of a CNS Embryonal Tumor.

Extramedullary hematopoiesis (EMH) is hematopoiesis occurring outside of the bone marrow. It has been reported to develop in abdominal organs or lymph nodes after chemotherapy. Here, the authors describe a patient with a localized central nervous system embryonal tumor who, during intensive chemotherapy, developed dural nodules. Biopsy revealed these nodules to be EMH. Without a pathologic diagnosis, this may have been considered disease progression, altering the patient's treatment plan. This report intends to serve as a reminder that EMH should be included in the differential diagnosis of suspicious lesions and highlights the importance of their biopsy because of potential management implications.

Trigeminal activation patterns evoked by chemical stimulation of the dura mater in rats.

BACKGROUND: Although migraine is one of the most common primary headaches, its therapy is still limited in many cases. The use of animal models is crucial in the development of novel therapeutic strategies, but unfortunately, none of them show all aspects of the disease, therefore, there is a constant need for further improvement in this field. The application of inflammatory agents on the dura mater is a widely accepted method to mimic neurogenic inflammation in rodents, which plays a key role in the pathomechanism of migraine. Complete Freund's Adjuvant (CFA), and a mixture of inflammatory mediators, called inflammatory soup (IS) are often used for this purpose. METHODS: To examine the activation pattern that is caused by chemical stimulation of dura mater, we applied CFA or IS over the right parietal lobe. After 2 h and 4 h (CFA groups), or 2.5 h and 4 h (IS groups), animals were perfused, and c-Fos immunoreactive cells were counted in the caudal trigeminal nucleus. To explore every pitfall, we examined whether our surgical procedure (anesthetic drug, stereotaxic apparatus, local lidocaine) can alter the results under the same experimental settings. c-Fos labeled cells were counted in the second-order neuron area based on the somatotopic organization of the trigeminal nerve branches. RESULTS: We could not find any difference between the CFA and physiological saline group neither 2 h, nor 4 h after dural stimulation. IS caused significant difference after both time points between IS treated and control group, and between treated (right) and control (left) side. Stereotaxic frame usage had a substantial effect on the obtained results. CONCLUSIONS: Counting c-Fos immunoreactive cells based on somatotopic organization of the trigeminal nerve helped to examine the effect of chemical stimulation of dura in a more specific way. As a result, the use of IS over the parietal lobe caused activation in the area of the ophthalmic nerve. To see this effect, the use of lidocaine anesthesia is indispensable. In conclusion, application of IS on the dura mater induces short-term, more robust c-Fos activation than CFA, therefore it might offer a better approach to model acute migraine headache in rodents.

ATP sensitive potassium (KATP) channel inhibition: A promising new drug target for migraine.

BACKGROUND: Recently, the adenosine triphosphate (ATP) sensitive potassium channel opener levcromakalim was shown to induce migraine attacks with a far higher incidence than any previous provoking agent such as calcitonin gene-related peptide. Here, we show efficacy of ATP sensitive potassium channel inhibitors in two validated rodent models of migraine. METHODS: In female spontaneous trigeminal allodynic rats, the sensitivity of the frontal region of the head was tested by an electronic von Frey filament device. In mice, cutaneous hypersensitivity was induced by repeated glyceryl trinitrate or levcromakalim injections over nine days, as measured with von Frey filaments in the hindpaw. Release of calcitonin gene-related peptide from dura mater and trigeminal ganglion was studied ex vivo. RESULTS: The ATP sensitive potassium channel inhibitor glibenclamide attenuated the spontaneous cephalic hypersensitivity in spontaneous trigeminal allodynic rats and glyceryl trinitrate-induced hypersensitivity of the hindpaw in mice. It also inhibited CGRP release from dura mater and the trigeminal ganglion isolated from spontaneous trigeminal allodynic rats. The hypersensitivity was also diminished by the structurally different ATP sensitive potassium channel inhibitor gliquidone. Mice injected with the ATP sensitive potassium channel opener levcromakalim developed a progressive hypersensitivity that was completely blocked by glibenclamide, confirming target engagement. CONCLUSION: The results suggest that ATP sensitive potassium channel inhibitors could be novel and highly effective drugs in the treatment of migraine.

How Safe is the Use of Intrathecal Fluorescein? An Experimental Study.

AIM: To investigate the effects of fluorescein-sodium on neural tissues. MATERIAL AND METHODS: Twenty-one Wistar rats were randomly divided into three experimental groups: control (group 1) and fluorescein-sodium groups with different doses (groups 2 and 3). In the control group, craniectomy following with durotomy was performed with the help of a loupe microscope, and a dry sponge was overlayed to the brain tissue. In the study groups, the open dura was covered with a sponge soaked with 0.02 mg (group 2) and with 0.2 mg (group 3) fluorescein sodium following craniectomy. Three weeks postoperatively, rats were sacrificed for the histopathologic evaluations. RESULTS: Fluorescein-induced apoptosis occurs in a dose-dependent manner in rats' neurons. It was determined that neuron and neuroglial cell TUNEL staining was statistically different among the three groups (p < 0.001). Our results indicated that fluorescein induces apoptosis, resulting in increased nuclear factor kappa beta (NF-kß) expression in a dose-dependent manner. CONCLUSION: Fluorescein sodium is used frequently during surgery for CSF fistulas. However, information in the literature about its safety is insufficient. Our study holds promise for the development of new studies on the reliability of this agent.

Marked effectiveness of low-dose oral methotrexate for steroid-resistant idiopathic hypertrophic pachymeningitis: Case report.

Idiopathic hypertrophic pachymeningitis (HP) is a rare clinical entity characterized by thickening of the dura mater without obvious underlying disease. High-dose steroid therapy is considered to be the first line for idiopathic HP, but half of patients show resistance for steroid therapy and suffer progressive clinical course. We describe low-dose methotrexate (MTX) administration for recurrent and steroid-resistant idiopathic HP resulting in noticeable improvement without severe adverse effects. A 51-year-old Japanese woman with dermatomyositis first presented with right retro-orbital pain caused by dural thickening in the sella and upper clivus involving the right trigeminal nerve, which was diagnosed as idiopathic HP by transsphenoidal biopsy. High-dose methylprednisolone therapy led to remission, and she remained healthy with low-dose dexamethasone. Three years after the initial therapy she presented with right facial nerve and lower cranial nerve palsies caused by diffuse and significant dural thickening in the posterior cranial fossa. Second highdose methylprednisolone therapy was introduced, but the effect was transient and she suffered aspiration pneumonia. Low-dose oral MTX therapy was begun, and her symptoms were almost resolved and dural thickening was remarkably improved without severe adverse effects. Lowdose MTX may be a more appropriate choice for idiopathic HP than steroid administration. Randomized controlled clinical trials are now needed.

Evaluation and management of small dural tears in primary lumbar spinal decompression and discectomy surgery.

Incidental dural tear is one of the most common intraoperative complications in lumbar spine surgery. Yet, its technical management for the prevention of CSF leak is controversial. The technique of managing dural tears depends on the location of the dural tears as well on the length and anatomical characteristics of the dural tear. We propose an anatomical classification for small (less than one cm) dural tears and report on the outcome of managing these dural tears types using different technique for different type. 62 patients underwent spinal dural repair after microdiscectomy or lumbar spinal decompression. Group 1 consisted of 20 patients, with Type I or mild dural tear who had tissue-glue coated collagen sponge or fibrin glue application. Group 2 comprised 21 patients with Type II or moderate dural tear who had both tissue-glue coated collagen sponge and fibrin glue application. Group 3 comprised 21 patients with Type III or severe dural tear who had polypropylene suture and tissue-glue coated collagen sponge and/or fibrin glue application. Evident postoperative CSF leak was used to determine the patient's postoperative result. Postoperative CSF leak was not evident during a minimum 1 year follow up in group 1. Internal CSF leak was evident in group 2 (n = 3) and group 3 (n = 3) during same follow up. Three patients underwent re-do spinal surgery for CSF leak repair. We recommend different management technique depending on the type of tear. For type I, we recommend the use of tissue-glue coated collagen sponge or fibrin glue application, without dural suturing.

Salmon calcitonin ameliorates migraine pain through modulation of CGRP release and dural mast cell degranulation in rats.

The exact mechanism of migraine pathophysiology still remains unclear due to the complex nature of migraine pain. Salmon calcitonin (SC) exhibits antinociceptive effects in the treatment of various pain conditions. In this study, we explored the mechanisms underlying the analgesic effect of salmon calcitonin on migrane pain using glyceryltrinitrate (GTN)-induced model of migraine and ex vivo meningeal preparations in rats. Rats were intraperitoneally administered saline, GTN (10 mg/kg), vehicle, saline + GTN, SC (50 µg/kg) + GTN, and SC alone. Also, ex vivo meningeal preparations were applied topically 100 µmol/L GTN, 50 µmol/L SC, and SC + GTN. Calcitonin gene-related peptide (CGRP) contents of plasma, trigeminal neurons and superfusates were measured using enzyme-immunoassays. Dural mast cells were stained with toluidine blue. c-fos neuronal activity in trigeminal nucleus caudalis (TNC) sections were determined by immunohistochemical staining. The results showed that GTN triggered the increase in CGRP levels in plasma, trigeminal ganglion neurons and ex vivo meningeal preparations. Likewise, GTN-induced c-fos expression in TNC. In in vivo experiments, GTN caused dural mast cell degranulation, but similar effects were not seen in ex vivo experiments. Salmon calcitonin administration ameliorated GTN-induced migraine pain by reversing the increases induced by GTN. Our findings suggested that salmon calcitonin could alleviate the migraine-like pain by modulating CGRP release at different levels including the generation and conduction sites of migraine pain and mast cell behaviour in the dura mater. Therefore salmon calcitonin may be a new therapeutic choice in migraine pain relief.

Controlled-release mitomycin C-polylactic acid film prevents epidural scar hyperplasia after laminectomy by inducing fibroblast autophagy and regulating the expression of miRNAs.

OBJECTIVE: To design a new controlled-release MMC-PLA film and explore whether and how this film could prevent epidural scar hyperplasia and adhesion in a post-laminectomy rat model. MATERIALS AND METHODS: All procedures were performed under the approval and supervision of the Institutional Animal Care and Use Committee (IACUC) of Nanjing Medical University. A total of 120 Sprague-Dawley (SD) rats were randomly placed into four groups after laminectomy (each group=30 rats). In Group I, the laminectomy area was flushed with saline as a control; in Group II, 25 mg of PLA film was applied to the dura mater in the laminectomy area; in Group III, a cotton pad soaked with 0.01% MMC solution was kept on the laminectomy area; and in Group IV, 25 mg of PLA film containing 0.01% MMC was implanted on the laminectomy area. Magnetic resonance imaging (MRI), hematoxylin-eosin (HE) staining and Masson staining were used to evaluate scar adhesion and collagen deposition one month after the operation. Autophagy-related proteins, including autophagy-related gene 5 (ATG5), beclin 1, light chain-3B-2/1 (LC3B-2/1) and protein 53 (p53), were detected by Western blotting. A microRNA microarray analysis was performed to screen for scar tissue miRNAs, especially those associated with autophagy, and changes in expression were confirmed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: A total of 112 rats recovered uneventfully from the surgery. MRI showed that the scar adhesion and scar area of the MMC-PLA group were significantly reduced compared with those of the PLA, MMC, and saline groups. Accordingly, scar adhesion and the deposition of collagen in the rats treated with MMC-PLA were also significantly reduced, as indicated by HE and Masson staining. In the scar tissue, the levels of autophagy-related proteins (ATG5, beclin 1, LC3B-2/1 and p53) were significantly elevated in the MMC-PLA group. Additionally, in the MMC-PLA group, the expression levels of miR-34a, miR-146a and miR-200 were significantly increased, while the levels of miR-16, miR-221 and miR-378a were significantly decreased. CONCLUSIONS: The controlled-release MMC-PLA film could alleviate epidural scar hyperplasia after laminectomy; this outcome might be associated with increased autophagy and altered expression of miRNAs in the scar tissue.

Topical dura mater application of CFA induces enhanced expression of c-fos and glutamate in rat trigeminal nucleus caudalis: attenuated by KYNA derivate (SZR72).

BACKGROUND: Migraine is a debilitating neurological disorder where trigeminovascular activation plays a key role. We have previously reported that local application of Complete Freund's Adjuvant (CFA) onto the dura mater caused activation in rat trigeminal ganglion (TG) which was abolished by a systemic administration of kynurenic acid (KYNA) derivate (SZR72). Here, we hypothesize that this activation may extend to the trigeminal complex in the brainstem and is attenuated by treatment with SZR72. METHODS: Activation in the trigeminal nucleus caudalis (TNC) and the trigeminal tract (Sp5) was achieved by application of CFA onto the dural parietal surface. SZR72 was given intraperitoneally (i.p.), one dose prior CFA deposition and repeatedly daily for 7 days. Immunohistochemical studies were performed for mapping glutamate, c-fos, PACAP, substance P, IL-6, IL-1ß and TNFα in the TNC/Sp5 and other regions of the brainstem and at the C1-C2 regions of the spinal cord. RESULTS: We found that CFA increased c-fos and glutamate immunoreactivity in TNC and C1-C2 neurons. This effect was mitigated by SZR72. PACAP positive fibers were detected in the fasciculus cuneatus and gracilis. Substance P, TNFα, IL-6 and IL-1ß immunopositivity were detected in fibers of Sp5 and neither of these molecules showed any change in immunoreactivity following CFA administration. CONCLUSION: This is the first study demonstrating that dural application of CFA increases the expression of c-fos and glutamate in TNC neurons. Treatment with the KYNA analogue prevented this expression.

Supradural inflammatory soup in awake and freely moving rats induces facial allodynia that is blocked by putative immune modulators.

Facial allodynia is a migraine symptom that is generally considered to represent a pivotal point in migraine progression. Treatment before development of facial allodynia tends to be more successful than treatment afterwards. As such, understanding the underlying mechanisms of facial allodynia may lead to a better understanding of the mechanisms underlying migraine. Migraine facial allodynia is modeled by applying inflammatory soup (histamine, bradykinin, serotonin, prostaglandin E2) over the dura. Whether glial and/or immune activation contributes to such pain is unknown. Here we tested if trigeminal nucleus caudalis (Sp5C) glial and/or immune cells are activated following supradural inflammatory soup, and if putative glial/immune inhibitors suppress the consequent facial allodynia. Inflammatory soup was administered via bilateral indwelling supradural catheters in freely moving rats, inducing robust and reliable facial allodynia. Gene expression for microglial/macrophage activation markers, interleukin-1ß, and tumor necrosis factor-α increased following inflammatory soup along with robust expression of facial allodynia. This provided the basis for pursuing studies of the behavioral effects of 3 diverse immunomodulatory drugs on facial allodynia. Pretreatment with either of two compounds broadly used as putative glial/immune inhibitors (minocycline, ibudilast) prevented the development of facial allodynia, as did treatment after supradural inflammatory soup but prior to the expression of facial allodynia. Lastly, the toll-like receptor 4 (TLR4) antagonist (+)-naltrexone likewise blocked development of facial allodynia after supradural inflammatory soup. Taken together, these exploratory data support that activated glia and/or immune cells may drive the development of facial allodynia in response to supradural inflammatory soup in unanesthetized male rats.

Activation of dura-sensitive trigeminal neurons and increased c-Fos protein induced by morphine withdrawal in the rostral ventromedial medulla.

Aims Overuse of medications used to treat migraine headache can increase the frequency of headaches. Sudden abstinence from migraine medication can also lead to a period of withdrawal-induced headaches. The aim of this study was to examine the effect of morphine withdrawal localized to the rostral ventromedial medulla (RVM) on the activity of dura-sensitive spinal trigeminal nucleus caudalis (Vc) neurons. Methods Rats were implanted with either morphine or placebo pellets for six to seven days before the microinjection of naloxone methiodide or phosphate-buffered saline into the RVM in urethane-anesthetized animals. Dura-sensitive neurons were recorded in the Vc and the production of c-Fos-like immunoreactivity was quantified. Results In chronic morphine-treated animals, naloxone methiodide microinjections produced a significant increase both in ongoing and facial heat-evoked activity and an increase in Fos-positive neurons in the Vc and in the nucleus reticularis dorsalis, a brainstem region involved in diffuse noxious inhibitory controls. Conclusions These results indicate that activation of pronociceptive neurons in the RVM under conditions of morphine withdrawal can increase the activity of neurons that transmit headache pain. Modulation of the subnucleus reticularis dorsalis by the RVM may explain the attenuation of conditioned pain modulation in patients with chronic headache.

Dural stimulation in rats causes brain-derived neurotrophic factor-dependent priming to subthreshold stimuli including a migraine trigger.

Migraine is one of the most common and most disabling disorders. Between attacks, migraine patients are otherwise normal but are sensitized to nonnoxious events known as triggers. The purpose of these studies was to investigate whether a headache-like event causes sensitization, or priming, to subsequent subthreshold events. Interleukin-6 (IL-6) was applied to the rat cranial dura mater which produced cutaneous facial and hind paw allodynia that lasted 24 hours. At 72 hours, IL-6-treated rats developed allodynia in response to dural stimulation with either a pH 6.8 or pH 7.0 solution and to a systemic nitric oxide (NO) donor, a well-known migraine trigger. Vehicle-treated rats did not respond to either pH stimulus or to the NO donor, demonstrating that IL-6 exposure primes rats to subthreshold stimuli. Inhibitors of brain-derived neurotrophic factor (BDNF) signaling given either systemically or intracisternally 24 hours after IL-6 eliminated responses to dural pH stimulation at 72 hours. Additionally, intracisternal administration of BDNF without previous dural stimulation produced allodynia and once resolved, animals were primed to dural pH 6.8/pH 7.0 and a systemic NO donor. Finally, hind paw IL-6 produced paw allodynia but not priming to paw injection of pH 7.0 at 72 hours demonstrating differences in priming depending on location. These data indicate that afferent input from the meninges produces BDNF-dependent priming of the dural nociceptive system. This primed state mimics the interictal period of migraine where attacks can be triggered by normally nonnoxious events and suggests that BDNF-dependent plasticity may contribute to migraine.

The effect of vancomycin powder on human dural fibroblast culture and its implications for dural repair during spine surgery.

OBJECTIVE Surgical site infections (SSIs) are a major source of morbidity after spinal surgery. Several recent studies have described the finding that applying vancomycin powder to the surgical bed may reduce the incidence of SSI. However, applying vancomycin in high concentrations has been shown in vitro to inhibit osteoblast proliferation and to induce cell death. Vancomycin may have a deleterious effect on dural healing after repair of an intentional or unintentional durotomy. This study was therefore undertaken to assess the effect of different concentrations of vancomycin on a human dura mater cell culture. METHODS Human dura intended for disposal after decompressive craniectomy was harvested. Explant primary cultures and subcultures were subsequently performed. Cells were characterized through common staining and immunohistochemistry. A growth curve was performed to assess the effect of different concentrations of vancomycin (40, 400, and 4000 µg/ml) on cell count. The effect of vancomycin on cellular shape, intercellular arrangement, and viability was also evaluated. RESULTS All dural tissue samples successfully developed into fusiform cells, demonstrating pseudopod projections and spindle formation. The cells demonstrated vimentin positivity and also had typical features of fibroblasts. When applied to the cultures, the highest dose of vancomycin induced generalized cell death within 24 hours. The mean (± SD) cell counts for control, 40, 400, and 4000 µg/ml were 38.72 ± 15.93, 36.28 ± 22.87, 19.48 ± 6.53, and 4.07 ± 9.66, respectively (p < 0.0001, ANOVA). Compared with controls, vancomycin-exposed cells histologically demonstrated a smaller cytoplasm and decreased pseudopodia formation resulting in the inhibition of normal spindle intercellular arrangement. CONCLUSIONS When vancomycin powder is applied locally, dural cells are exposed to a concentration several times greater than when delivered systemically. In this in vitro model, vancomycin induced dural cell death, inhibited growth, and altered cellular morphology in a concentration-dependent fashion. Defining a safe vancomycin concentration that is both bactericidal and also does not inhibit normal dural healing is necessary.

Effects of hemostatic polysaccharide agent on epidural fibrosis formation after lumbar laminectomy in rats.

BACKGROUND CONTEXT: Epidural fibrosis is a common adverse outcome of spinal surgery that can compress the dural sac and nerve root. Local hemostatic agents have many indications in numerous types of spinal surgery. As these agents may behave as foreign bodies, inducing inflammation and delaying regeneration, they could enhance the risk of epidural fibrosis. PURPOSE: We evaluated the effects of hemostatic polysaccharide on epidural fibrosis development in laminectomized rats. STUDY DESIGN: This is a randomized controlled trial. OUTCOME MEASURES: One month after surgery, tissues were histopathologically examined. Spinal tissue surrounding the laminectomy site was cut with a microtome and stained with hematoxylin and eosin and Masson trichrome. Slides were evaluated by a pathologist in a blinded fashion. The extent of epidural fibrosis, fibroblast cell density, cartilage, and bone regeneration was evaluated. METHODS: Rats were randomly assigned to receive sham surgery, laminectomy, or laminectomy with hemostatic polysaccharide (seven rats per group). Sham surgery that consisted of a skin incision was performed without laminectomy. Laminectomy was performed at the L1 and L2 vertebrae. In the experimental group, the polysaccharide hemostatic material, HaemoCer was placed in the laminectomy area. RESULTS: The proportion of rats with epidural fibrosis in laminectomized mice (both with and without hemostatic material) was higher than in sham-operated rats (p<.01). There was no difference in fibrosis between the two groups of laminectomized rats (p>.05). CONCLUSIONS: Our study indicates that hemostatic polysaccharide does not enhance epidural fibrosis following laminectomy in rodents, suggesting that absorbable polysaccharides may be appropriate for use in hemostasis during spinal surgery.

Dura-evoked neck muscle activity involves purinergic and N-methyl-D-aspartate receptor mechanisms.

We have previously demonstrated that noxious stimulation of craniofacial tissues including the frontal dura reflexly evokes significant increases in neck muscle electromyographic (EMG) activity. The primary aim of this study was to determine whether purinergic receptor mechanisms may be involved in these EMG effects, and whether N-methyl-D-aspartate (NMDA) receptor processes modulate the purinergic mechanisms. Application of the P2X1, P2X3 and P2X2/3 receptor agonist α,ß-methylene ATP (but not vehicle) to the dural surface evoked a significant (P<0.05) increase in ipsilateral neck EMG activity that could be suppressed by dural or intrathecal application of the selective P2X1, P2X3 and P2X2/3 receptor antagonist 2',3'-O-(2,4,6-trinitrophenyl) ATP (TNP-ATP) but not by vehicle; the intrathecal application of 2-amino-5-phosphonopentanoic acid, an NMDA receptor antagonist, also significantly reduced the neck EMG activity evoked by dural application of α,ß-methylene ATP. These data suggest that purinergic receptor mechanisms contribute to the increased neck activity that can be reflexly evoked by noxious stimulation of the frontal dura, and that NMDA as well as purinergic receptor mechanisms in the medulla may modulate these purinergic-related effects.

In situ forming hydrogel composed of hyaluronate and polygalacturonic acid for prevention of peridural fibrosis.

Hyaluronic acid-based hydrogels can reduce postoperative adhesion. However, the long-term application of hyaluronic acid is limited by tissue mediated enzymatic degradation. To overcome this limitation, we developed a polygalacturonic acid and hyaluronate composite hydrogel by Schiff's base crosslinking reaction. The polygalacturonic acid and hyaluronate composite hydrogels had short gelation time (less than 15 s) and degraded by less than 50 % in the presence of hyaluronidase for 7 days. Cell adhesion and migration assays showed polygalacturonic acid and hyaluronate composite hydrogels prevented fibroblasts from adhesion and infiltration into the hydrogels. Compared to hyaluronate hydrogels and commercial Medishield™ gels, polygalacturonic acid and hyaluronate composite hydrogel was not totally degraded in vivo after 4 weeks. In the rat laminectomy model, polygalacturonic acid and hyaluronate composite hydrogel also had better adhesion grade and smaller mean area of fibrous tissue formation over the saline control and hyaluronate hydrogel groups. Polygalacturonic acid and hyaluronate composite hydrogel is a system that can be easy to use due to its in situ cross-linkable property and potentially promising for adhesion prevention in spine surgeries.

Alpha-lipoic acid inhibits peridural fibrosis following laminectomy through the inactivation of TGF-ß1, PDGF, PAI-1 and IL-6 expressions.

AIM: The objective of this study was to investigate the antifibrotic effect of parenteral administration of alpha-lipoic acid (ALA), which has been reported to reduce fibrosis in the liver, oral mucosa, and peritoneum, in laminectomized rabbits as a potential candidate for the prevention of peridural fibrosis. MATERIAL AND METHODS: Twelve adult New Zealand white male rabbits were divided into control (n=6) and ALA treatment groups (n=6). Laminectomy of the lumbar spine was performed in all animals, and ALA was administered intramuscularly in six rabbits composing the treatment group. Total RNA obtained from the paraffin-embedded tissues was analyzed for transforming growth factor-ß1 (TGF-ß1), plateletderived growth factor (PDGF), plasminogen activator inhibitor-1 (PAI-1) and interleukin-6 (IL-6). RESULTS: mRNA investigations showed that TGF-ß1, PDGF, PAI-1 and IL-6 gene expressions, which constitute strong evidence for the development of fibrosis, were significantly lower in the treatment group compared with the results obtained from the control group. According to the histological peridural grading, the ALA-treated group showed significantly less peridural fibrosis than the control group. CONCLUSION: Intramuscular administration of ALA is a promising treatment for the prevention of peridural fibrosis in the postoperative period.

Anti-adhesive effect of hyaluronate in a rabbit laminectomy model.

BACKGROUND: Postlaminectomy dural adhesion is a common cause of recurrent symptoms. Hyaluronic acid-based gel has been reported to reduce the incidence of postoperative adhesion in the peritoneal cavity; however, its effect on preventing postoperative scar formation at laminectomy sites is not yet known. The purpose of this study was to evaluate the anti-adhesive effect of hyaluronic acid-based gelatin after laminectomy, using a rabbit model. METHODS: Twelve adult New Zealand rabbits underwent two-level lumbar laminectomy, and were randomly assigned to one of two groups of six rabbits each. The treatment group received hyaluronic acid-based gelatin treatment and the control group was untreated. Rabbits were sacrificed 8 weeks after treatment. Peel-off testing and histological analysis were performed to assess the tenacity and the extent of adhesion formation. RESULTS: No significant difference was observed in the neurologic performance between the two groups. The tenacity in the treatment group was significantly reduced compared to that of the control group (3.17 ± 0.75 vs. 4.33 ± 0.52, respectively; p = 0.016). Histological analysis showed significantly less scar tissue formation in the treatment group, with a larger subarachnoid space and greater distance between the dura and scar tissues. The amount of fibroblast cells also was significantly smaller in the treatment group than in the control group (3078 ± 313.68 vs. 3742 ± 455.65, respectively; p = 0.042). CONCLUSIONS: No serious adverse events were reported, and no difference was found in the incidence of complications between the treatment and control groups. The findings suggested that hyaluronic acid-based gelatin may be effective for preventing postlaminectomy dural adhesion in rabbits.

Assessing the role of selected growth factors and cytostatic agents in an in vitro model of human dura mater healing.

OBJECTIVES: Cerebrospinal fluid (CSF) leaks are a common concern in skull base surgery. Appropriate dural healing is crucial to prevent CSF leaks but the entire process has been barely understood so far. Here, we review the impact of growth factors and chemotherapeutic agents on an explant culture of human dural fibroblasts and a 3D subculture grown in a collagen mesh scaffold. METHODS: Human dural specimens were harvested during surgical procedures where they would not be further used therapeutically or diagnostically. Explant cultures were grown in Petri dishes, and subcultures were grown in collagen mesh scaffolds. Insulin, fibroblast growth factor type 2 (FGF-2), and human serum were analyzed for their effect as growth factors, whereas mitomycin C, vincristine, and colchicine were analyzed for their role as inhibitors. Cell count was used as a parameter to assess the effects of these factors. In addition, the effects of human serum were assessed using collagen mesh scaffolds. RESULTS: Insulin, FGF-2, and human serum increased culture cell count; human serum also achieved an increased number of viable fibroblasts embedded in a collagen mesh. Mitomycin C, which is a mitosis inhibitor, showed no significant effect on cell count, whereas colchicine and vincristine, which inhibit both mitosis and migration, resulted in cell growth suppression. DISCUSSION: In our model, dural defect closure is achieved through cell migration rather than through cell growth. Adding growth factors to the dural suture line or into a collagen mesh might prove useful to stimulate dural closure.