Sciatic Nerve Transection Model Research Articles

Involvement of placental growth factor in Wallerian degeneration

Wallerian degeneration (WD) is an inflammatory process of nerve degeneration, which occurs more rapidly in the peripheral nervous system compared with the central nervous system, resulting, respectively in successful and aborted axon regeneration. In the peripheral nervous system, Schwann cells (SCs) and macrophages, under the control of a network of cytokines and chemokines, represent the main cell types involved in this process. Within this network, the role of placental growth factor (PlGF) remains totally unknown. However, properties like monocyte activation/attraction, ability to increase expression of pro-inflammatory molecules, as well as neuroprotective effects, make it a candidate likely implicated in this process. Also, nothing is described about the expression and localization of this molecule in the peripheral nervous system. To address these original questions, we decided to study PlGF expression under physiological and degenerative conditions and to explore its role in WD, using a model of sciatic nerve transection in wild-type and Pgf(-/-) mice. Our data show dynamic changes of PlGF expression, from periaxonal in normal nerve to SCs 24h postinjury, in parallel with a p65/NF-κB recruitment on Pgf promoter. After injury, SC proliferation is reduced by 30% in absence of PlGF. Macrophage invasion is significantly delayed in Pgf(-/-) mice compared with wild-type mice, which results in worse functional recovery. MCP-1 and proMMP-9 exhibit a 3-fold reduction of their relative expressions in Pgf(-/-) injured nerves, as demonstrated by cytokine array. In conclusion, this work originally describes PlGF as a novel member of the cytokine network of WD.

Effect of bone marrow-derived mononuclear cells on nerve regeneration in the transection model of the rat sciatic nerve

Bone marrow-derived stem cells enhance the rate of regeneration and clinical improvement in nerve injury, spinal cord injury and brain infarction. Recent experiments in rat spinal cord demyelination showed that remyelination was specific to intravenous delivery of the bone marrow-derived mononuclear cell (BM-MNC) fraction, although the specific role of this fraction in peripheral nerve regeneration has not been examined. Therefore we evaluated the role of BM-MNCs in peripheral nerve regeneration in the rat sciatic nerve transection model. After anesthesia, the right sciatic nerve of 20 adult-male Wistar rats was transected under an operating microscope. In the test group, the cut ends of the nerve were approximated with two epineural microsutures, the gap was filled with rat BM-MNCs and the approximated nerve ends were covered with fibrin glue. In the control group, the transected nerve ends were repaired with two epineural microsutures and fibrin sealant only. Histological assessment of the nerve was performed 30 days and 60 days after the operation and regenerative changes were compared between the two groups. The recovery after nerve anastamosis was far better in the test group at both 30 days and 60 days. There was a statistically significant difference in axonal regeneration, remyelination and myelin thickness at sites 5 mm and 10 mm from the site of repair of the nerve. Schwann cell proliferation and degenerative changes were more prevalent in the controls. This study demonstrates that local delivery of BM-MNCs (which can be isolated easily from bone marrow aspirates) into injured peripheral nerve increases the rate and degree of nerve regeneration. The present study highlights the role of BM-MNCs in peripheral nerve regeneration.

Trophic activity derived from bone marrow mononuclear cells increases peripheral nerve regeneration by acting on both neuronal and glial cell populations

A rat model of complete sciatic nerve transection was used to evaluate the effect of bone marrow mononuclear cells (BMMC) transplanted to the injury site immediately after lesion. Rats treated with BMMC had both sensory and motor axons reaching the distal stump earlier compared to untreated animals. In addition, BMMC transplantation reduced cell death in dorsal root ganglia (DRG) compared to control animals. Transplanted BMMC remained in the lesion site for several days but there is no evidence of BMMC differentiation into Schwann cells. However, an increase in the number of Schwann cells, satellite cells and astrocytes was observed in the treated group. Moreover, neutralizing antibodies for nerve growth factor (NGF) (but not for brain-derived neurotrophic factor and ciliary-derived neurotrophic factor) added to the BMMC-conditioned medium reduced neurite growth of sensory and sympathetic neurons in vitro, suggesting that BMMC release NGF, improve regeneration of the sciatic nerve in the adult rat and stimulate Schwann and satellite cell proliferation or a combination of both.

The expression patterns of β1,4 galactosyltransferase I and V mRNAs, and Galβ1-4GlcNAc group in rat gastrocnemius muscles post sciatic nerve injury

Glycosylation is one of the most important post-translational modifications. It is clear that the single step of beta1,4-galactosylation is performed by a family of beta1,4-galactosyltransferases (beta1,4-GalTs), and that each member of this family may play a distinct role in different tissues and cells. beta1,4-GalT I and V are involved in the biosynthesis of N-linked oligosaccharides and play roles in sciatic nerve regeneration after sciatic nerve injury. In the present study, the expression of beta1,4-galactosyltransferase (beta1,4-GalT) I, V mRNAs and Galbeta1-4GlcNAc group were examined in rat gastrocnemius muscles after sciatic nerve crush and transection. Real time PCR revealed that beta1,4-GalT I and V mRNAs expressed at a high level in normal gastrocnemius muscles and decreased gradually from 6 h, reached the lowest level at 2 weeks, then restored gradually to relatively normal level at 4 weeks after sciatic nerve crush. In contrast, in sciatic nerve transection model, beta1,4-GalT I and V mRNAs decreased gradually from 6 h, and remained on a low level at 4 weeks in gastrocnemius muscles after sciatic nerve transection. In situ hybridization indicated that beta1,4-GalT I and V mRNAs localized in numerous myocytes and muscle satellite cells under normal conditions and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 4 weeks after sciatic nerve transection. Furthermore, lectin blotting showed that the expression level of the Galbeta1-4GlcNAc group decreased from 6 h, reached the lowest level at 2 weeks, and restored to relatively normal level at 4 weeks after sciatic nerve crush. RCA-I lectin histochemistry demonstrated that Galbeta1-4GlcNAc group localized in numerous membranes of myocytes and muscle satellite cells in normal and at 4 weeks after sciatic nerve crush, and in a few muscle satellite cells at 2 and 4 weeks after sciatic nerve transection. These results indicated that the expressions of beta1,4-GalT I, V mRNAs and Galbeta1-4GlcNAc group were involved in the process of denervation and reinnervation, which suggests that beta1,4-GalT I, V mRNAs and Galbeta1-4GlcNAc group may play an important role in the muscle regeneration.

Transplantation of Embryonic Stem Cells Improves Nerve Repair and Functional Recovery After Severe Sciatic Nerve Axotomy in Rats

Extensive research has focused on transplantation of pluripotent stem cells for the treatment of central nervous system disorders, the therapeutic potential of stem cell therapy for injured peripheral nerves is largely unknown. We used a rat sciatic nerve transection model to test the ability of implanted embryonic stem (ES) cell-derived neural progenitor cells (ES-NPCs) in promoting repair of a severely injured peripheral nerve. Mouse ES cells were neurally induced in vitro; enhanced expression and/or secretion of growth factors were detected in differentiating ES cells. One hour after removal of a 1-cm segment of the left sciatic nerve, ES-NPCs were implanted into the gap between the nerve stumps with the surrounding epineurium as a natural conduit. The transplantation resulted in substantial axonal regrowth and nerve repair, which were not seen in culture medium controls. One to 3 months after axotomy, co-immunostaining with the mouse neural cell membrane specific antibody M2/M6 and the Schwann cell marker S100 suggested that transplanted ES-NPCs had survived and differentiated into myelinating cells. Regenerated axons were myelinated and showed a uniform connection between proximal and distal stumps. Nerve stumps had near normal diameter with longitudinally oriented, densely packed Schwann cell-like phenotype. Fluoro-Gold retrogradely labeled neurons were found in the spinal cord (T12-13) and DRG (L4-L6), suggesting reconnection of axons across the transection. Electrophysiological recordings showed functional activity recovered across the injury gap. These data suggest that transplanted neurally induced ES cells differentiate into myelin-forming cells and provide a potential therapy for severely injured peripheral nerves.

Axonal supercharging technique using reverse end-to-side neurorrhaphy in peripheral nerve repair: an experimental study in the rat model

In an attempt to improve peripheral nerve repair, the influence of the addition of reverse end-to-side neurorrhaphy for an injured peripheral nerve was investigated in the rat sciatic nerve transection model. Twelve Sprague-Dawley rats were divided into two groups (six rats in each group). In Group I, the right sciatic nerve was cut at a point distal to the gluteal notch and repaired using end-to-end neurorrhaphy with four 10-0 nylon epineurial sutures. In Group II, after performing the same procedure as in Group I, the left sciatic nerve was cut distally and passed through a subcutaneous tunnel to the right side. The proximal stump of the left sciatic nerve was coapted to the epineurial window of the right sciatic nerve distal to the injured point in an end-to-side fashion using 10-0 nylon epineurial sutures. The effects were evaluated using analgesimeter recordings for the hind paw, electrophysiological tests, measurement of the muscle contraction force, a double-labeling technique, weight measurement and histological examination of the gastrocnemius muscle, histological examination of the bilateral sciatic nerves, and immunofluorescent staining. Results from the many tests used to evaluate the reverse end-to-side neurorrhaphy technique indicated that functional recovery of the denervated target organs was promoted by axonal augmentation. The reverse end-to-side neurorrhaphy technique could be useful in peripheral nerve repair.

Axonal supercharging technique using reverse end-to-side neurorrhaphy in peripheral nerve repair: an experimental study in the rat model

Object In an attempt to improve peripheral nerve repair, the influence of the addition of reverse end-to-side neu-rorrhaphy for an injured peripheral nerve was investigated in the rat sciatic nerve transection model. Methods Twelve Sprague–Dawley rats were divided into two groups (six rats in each group). In Group I, the right sciatic nerve was cut at a point distal to the gluteal notch and repaired using end-to-end neurorrhaphy with four 10-0 nylon epineurial sutures. In Group II, after performing the same procedure as in Group I, the left sciatic nerve was cut distally and passed through a subcutaneous tunnel to the right side. The proximal stump of the left sciatic nerve was coapted to the epineurial window of the right sciatic nerve distal to the injured point in an end-to-side fashion using 10-0 nylon epineurial sutures. The effects were evaluated using analgesimeter recordings for the hind paw, electrophysiological tests, measurement of the muscle contraction force, a double-labeling technique, weight measurement and histological examination of the gastrocnemius muscle, histological examination of the bilateral sciatic nerves, and immunofluorescent staining. Results Results from the many tests used to evaluate the reverse end-to-side neurorrhaphy technique indicated thatfunctional recovery of the denervated target organs was promoted by axonal augmentation. Conclusions The reverse end-to-side neurorrhaphy technique could be useful in peripheral nerve repair.

Retraction

Extensive research has focused on transplantation of pluripotent stem cells for the treatment of central nervous system disorders, the therapeutic potential of stem cell therapy for injured peripheral nerves is largely unknown. We used a rat sciatic nerve transection model to test the ability of implanted embryonic stem (ES) cell-derived neural progenitor cells (ES-NPCs) in promoting repair of a severely injured peripheral nerve. Mouse ES cells were neurally induced in vitro; enhanced expression and/or secretion of growth factors were detected in differentiating ES cells. One hour after removal of a 1-cm segment of the left sciatic nerve, ES-NPCs were implanted into the gap between the nerve stumps with the surrounding epineurium as a natural conduit. The transplantation resulted in substantial axonal regrowth and nerve repair, which were not seen in culture medium controls. One to 3 months after axotomy, co-immunostaining with the mouse neural cell membrane specific antibody M2/M6 and the Schwann cell marker S100 suggested that transplanted ES-NPCs had survived and differentiated into myelinating cells. Regenerated axons were myelinated and showed a uniform connection between proximal and distal stumps. Nerve stumps had near normal diameter with longitudinally oriented, densely packed Schwann cell-like phenotype. Fluoro-Gold retrogradely labeled neurons were found in the spinal cord (T12-13) and DRG (L4-L6), suggesting reconnection of axons across the transection. Electrophysiological recordings showed functional activity recovered across the injury gap. These data suggest that transplanted neurally induced ES cells differentiate into myelin-forming cells and provide a potential therapy for severely injured peripheral nerves.

Evaluation of ketamine, nimodipine, gabapentin and imipramine in partial sciatic nerve transection model of neuropathic pain in rat: An experimental study

The aim of this research is to study the effects of nimodipine, gabapentin, ketamine and imipramine in the partial sciatic nerve transection (PST) model of neuropathic pain in rats. PST was produced in young Wistar rats of either sex by partial destruction of the sciatic nerve. A decrease in the latency to paw withdrawal reaction on the hot plate was considered as development of neuropathy. The drugs were given daily from the third day of the procedure, and evaluation was done on days 7, 14, 21 and 28. There was a significant decrease (p < 0.05) in the paw withdrawal response in the nimodipine group from day 14 onward when compared with the control group. In the ketamine and imipramine group, this response was seen from day 21 onward. The effect persisted till the end of the study. There was no improvement in the gabapentin group. The results of our study show that nimodipine (dihydropyridine calcium channel blocker), ketamine (NMDA antagonist) and imipramine (tricyclic antidepressant) modulated hyperalgesia and allodynia in the PST model of neuropathy. Gabapentin (an alpha-2 delta calcium subunit blocker) did not show any effect in this model of neuropathy. The widespread use of gabapentin in various types of neuropathic pain thus needs to be reevaluated.

Sympathetic Sprouting Near Sensory Neurons After Nerve Injury Occurs Preferentially on Spontaneously Active Cells and Is Reduced by Early Nerve Block

Some chronic pain conditions are maintained or enhanced by sympathetic activity. In animal models of pathological pain, abnormal sprouting of sympathetic fibers around large- and medium-sized sensory neurons is observed in dorsal root ganglia (DRGs). Large- and medium-sized cells are also more likely to be spontaneously active, suggesting that sprouting may be related to neuron activity. We previously showed that sprouting could be reduced by systemic or locally applied lidocaine. In the complete sciatic nerve transection model in rats, spontaneous activity initially originates in the injury site; later, the DRGs become the major source of spontaneous activity. In this study, spontaneous activity reaching the DRG soma was reduced by early nerve blockade (local perfusion of the transected nerve with TTX for the 1st 7 days after injury). This significantly reduced sympathetic sprouting. Conversely, increasing spontaneous activity by local nerve perfusion with K(+) channel blockers increased sprouting. The hyperexcitability and spontaneous activity of DRG neurons observed in this model were also significantly reduced by early nerve blockade. These effects of early nerve blockade on sprouting, excitability, and spontaneous activity were all observed 4-5 wk after the end of early nerve blockade, indicating that the early period of spontaneous activity in the injured nerve is critical for establishing the more long-lasting pathologies observed in the DRG. Individual spontaneously active neurons, labeled with fluorescent dye, were five to six times more likely than quiescent cells to be co-localized with sympathetic fibers, suggesting a highly localized correlation of activity and sprouting.

A substance P receptor (NK 1) antagonist can reverse vascular and nociceptive abnormalities in a rat model of complex regional pain syndrome type II

Sciatic nerve section in rats evokes chronic hindlimb edema, pain behavior, and hyperalgesia, a syndrome resembling complex regional pain syndrome (CRPS II) in man. Furthermore, there is an increase in spontaneous protein extravasation in the hindpaw skin of rats after sciatic transection, similar to the increased protein extravasation observed in the edematous limbs of CRPS patients. Now we demonstrate that sciatic nerve section also generates chronic hindlimb warmth, distal articular tenderness, allodynia, and periarticular osteoporosis, sequelae of nerve injury resembling those observed in CRPS. We postulated that facilitated substance P signaling may contribute to these vascular and nociceptive abnormalities and attempted to reverse these changes with the long acting substance P receptor (NK 1) antagonist LY303870. Hindpaw spontaneous extravasation was inhibited by LY303870. Systemic administration of LY303870 also reversed hindpaw edema and cutaneous warmth. Intrathecal, but not systemic administration of LY303870 reversed soft tissue and articular mechanical hyperalgesia in the hindpaw. Collectively, these data further support the hypothesis that the sciatic nerve transection model closely resembles CRPS and that substance P contributes to the spontaneous extravasation, edema, warmth, and mechanical hyperalgesia observed in this model.

Influence of testosterone on autotomy in castrated male rats

Sex-related differences exist in nociception and gonadal steroids influence the analgesic response in animals and humans. As we have shown previously, estrogen could modify autotomy in female rats using the sciatic nerve transection model. To further characterize the relationship between gonadal steroid and nociception, the role of testosterone on autotomy in sciatic nerve sectioned rats was investigated. Twenty male rats were subjected to orchiectomy (ORX). Then ten rats received subcutaneous sesame oil and the other ten were treated with testosterone propionate in sesame oil (TP; 500 μg/day/rat). All the rats underwent sciatic nerve resection in left hind limb. Degree of self-mutilation was measured daily for 8 weeks. TP reinstatement resulted in significantly lower autotomy scores in orchiectomized rats. The results demonstrated that testosterone could modify the autotomy behavior, an indicator of neuropathic pain, in rats after nerve injury.

Glucocorticoid Inhibition of Neuropathic Hyperalgesia and Spinal Fos Expression

Glucocorticoids are used to treat patients suffering from neuropathic pain and complex regional pain syndromes (CRPS). Previously we found that once-daily injections of the glucocorticoid methylprednisolone had no antihyperalgesic effect in the rat sciatic nerve transection model for CRPS, but on the basis of CRPS clinical data, we hypothesized that a continuous infusion of methylprednisolone might prove effective. We further postulated that the antihyperalgesic effects of glucocorticoids were mediated by the inhibition of spinal neuron hyperactivity and by the depletion of substance P or its NK1 receptor. This study tested the effects of continuously infused methylprednisolone in sciatic nerve-transected rats. Continuous infusion of methylprednisolone (3 mg · kg−1 · d−1 for 21 days), started after the development of neuropathic hyperalgesia, reversed both heat and mechanical hyperalgesia over 2 wk, and this effect persisted for at least 1 wk after discontinuing methylprednisolone. In addition, continuous methylprednisolone infusion partially reversed nerve injury-evoked Fos expression in the dorsal horns, suggesting that glucocorticoids can inhibit the spinal neuron hyperactivity induced by chronic sciatic nerve transection. Finally, no changes were observed in spinal substance P or NK1 immunoreactivity after chronic methylprednisolone infusion, suggesting that the depletion of this neuropeptide or its receptor does not contribute to the antihyperalgesic actions of glucocorticoids. Implications Chronic continuous infusion of the glucocorticoid, methylprednisolone, relieved pain in a rodent model of nerve injury, and this effect persisted after discontinuing the drug. Methylprednisolone may be a curative treatment for some types of neuropathic pain when administered in divided daily doses over several weeks.

Glucocorticoid inhibition of neuropathic hyperalgesia and spinal Fos expression.

Glucocorticoids are used to treat patients suffering from neuropathic pain and complex regional pain syndromes (CRPS). Previously we found that once-daily injections of the glucocorticoid methylprednisolone had no antihyperalgesic effect in the rat sciatic nerve transection model for CRPS, but on the basis of CRPS clinical data, we hypothesized that a continuous infusion of methylprednisolone might prove effective. We further postulated that the antihyperalgesic effects of glucocorticoids were mediated by the inhibition of spinal neuron hyperactivity and by the depletion of substance P or its NK(1) receptor. This study tested the effects of continuously infused methylprednisolone in sciatic nerve-transected rats. Continuous infusion of methylprednisolone (3 mg. kg(-1). d(-1) for 21 days), started after the development of neuropathic hyperalgesia, reversed both heat and mechanical hyperalgesia over 2 wk, and this effect persisted for at least 1 wk after discontinuing methylprednisolone. In addition, continuous methylprednisolone infusion partially reversed nerve injury-evoked Fos expression in the dorsal horns, suggesting that glucocorticoids can inhibit the spinal neuron hyperactivity induced by chronic sciatic nerve transection. Finally, no changes were observed in spinal substance P or NK(1) immunoreactivity after chronic methylprednisolone infusion, suggesting that the depletion of this neuropeptide or its receptor does not contribute to the antihyperalgesic actions of glucocorticoids.