Apoptosis of spinal interneurons induced by sciatic nerve axotomy in the neonatal rat is counteracted by nerve growth factor and ciliary neurotrophic factor

Combination of Adult Mesenchymal Stem Cell Therapy and Immunomodulation with Dimethyl Fumarate Following Spinal Cord Ventral Root Repair

Spinal cord injury results in significant motor and sensory loss. In the experimental ventral root avulsion (VRA) model, the ventral (motor) roots are disconnected from the spinal cord surface, disrupting contact between spinal motoneurons and muscle fibers. Axotomized motoneurons typically degenerate within two to three weeks after avulsion, the situation being exacerbated by an increased glial response and chronic inflammation. Nevertheless, root reimplantation has been observed to stimulate regenerative potential in some motoneurons, serving as a model for CNS/PNS regeneration. We hypothesized that a combination of neuroprotective and immunomodulatory therapies is capable of enhancing regenerative responses following nerve root injury and repair. A heterologous fibrin biopolymer (HFB) was used for surgical repair; dimethyl fumarate (DMF) was used for neuroprotection and immunomodulation; and adipose tissue-derived mesenchymal stem cells (AT-MSCs) were used as a source of trophic factors and cytokines that may further enhance neuronal survival. Thus, adult female Lewis rats underwent unilateral VRA of the L4-L6 roots, followed by reimplantation with HFB, AT-MSCs transplantation, and daily DMF treatment for four weeks, with a 12-week postoperative survival period. An evaluation of the results focused on light microscopy, qRT-PCR, and the Catwalk motor function recovery system. Data were analyzed using one-way or two-way ANOVA (p < 0.05). The results indicate that the combined therapy resulted in a reduced glial response and a 70% improvement in behavioral motor recovery. Overall, the data support the potential of combined regenerative approaches after spinal cord root injury.

Nerve Tracing in Juvenile Rats: A Feasible Model for the Study of Brachial Plexus Birth Palsy and Cocontractions?

Brachial plexus birth injuries cause diminished motor function in the upper extremity. The most common sequel is internal rotation contracture. A number of these patients also suffer from cocontractions, preventing the use of an otherwise good passive range of motion in the shoulder. One theory behind the co-contracture problem is that injured nerve fibers grow into distal support tissue not corresponding to the proximal support tissue, resulting in reinnervation of the wrong muscle groups. To further elucidate this hypothesis, we used rat neonates to investigate a possible model for the study of cocontractions in brachial plexus birth injuries. Five-day-old rats were subjected to a crush injury to the C5-C6 roots. After a healing period of 4 weeks, the infraspinatus muscle was injected with Fluoro-Gold. A week later, the animals were perfused and spinal cords harvested and sectioned. Differences in the uptake of Fluoro-Gold and NeuN positive cells of between sides of the spinal cord were recorded. We found a larger amount of Fluoro-Gold positive cells on the uninjured side, while the injured side had positive cells dispersed over a longer area in the craniocaudal direction. Our findings indicate that the method can be used to trace Fluoro-Gold from muscle through a neuroma. Our results also indicate that a neuroma in continuity somewhat prevents the correct connection from being established between the motor neuron pool in the spinal cord and target muscle and that some neurons succumb to a crushing injury. We also present future research ideas.

Berberine enhances L1 expression and axonal remyelination in rats after brachial plexus root avulsion

BACKGROUND AND PURPOSE

Enhanced remyelination of the regenerated axons results in functional re-innervation and improved functional motor recovery after brachial plexus root avulsion (BPRA). The neural cell adhesion molecule L1 (L1CAM, L1) regulates myelination and promotes regeneration after acute injury in the nervous system. Berberine (BBR) can exert neuroprotective roles against the lesion. Herein, we investigated whether berberine (BBR) can affect the expression of L1 and enhance the axonal remyelination in rats following BPRA.

METHODS

The surgical procedures were performed to build the rat brachial plexus avulsion and re-implantation model, and then, the rats were treated with BBR. After the rehabilitation for 12 weeks, the musculocutaneous nerves were collected for quantitative real-time PCR, Western blot analysis, and histochemical and immunofluorescence staining.

RESULTS

We observed that, BBR treatment ameliorated the abnormal musculocutaneous nerve fibers morphology, up-regulated the L1 expression, increased the myelination-related genes, decreased the differentiated-associated genes, and up-regulated the phosphorylation of ERK.

CONCLUSION

These results suggest that BBR may enhance L1 expression and promote axonal remyelination after spinal root avulsion.

Neuroprotective effects of hyperbaric oxygen (HBO) therapy on neuronal death induced by sciatic nerve transection in rat

Background

Recent studies shows that hyperbaric oxygen (HBO) therapy exerts some protective effects against neural injuries. The purpose of this study was to determine the neuroprotective effects of HBO following sciatic nerve transection (SNT).

Methods

Rats were randomly divided into five groups (n = 14 per group): Sham-operated (SH) group, SH + HBO group, SNT group, and SNT + pre- and SNT + post-HBO groups (100% oxygen at 2.0 atm absolute, 60 min/day for five consecutive days beginning on 1 day before and immediately after nerve transaction, respectively). Spinal cord segments of the sciatic nerve and related dorsal root ganglions (DRGs) were removed 4 weeks after nerve transection for biochemical assessment of malodialdehyde (MDA) levels in spinal cord, biochemical assessment of superoxide dismutase (SOD) and catalse (CAT) activities in spinal cord, immunohistochemistry of caspase-3, cyclooxigenase-2 (COX-2), S100beta (S100ß), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) in spinal cord and DRG.

Results

The results revealed that MDA levels were significantly decreased in the SNT + pre-HBO group, while SOD and CAT activities were significantly increased in SNT + pre- and SNT + post-HBO treated rats. Attenuated caspase-3 and COX-2 expression, and TUNEL reaction could be significantly detected in the HBO-treated rats after nerve transection. Also, HBO significantly increased S100ß expression.

Conclusions

Based on these results, we can conclude that pre- and post-HBO therapy had neuroprotective effects against sciatic nerve transection-induced degeneration.

Differentiation of Pre- and Postganglionic Nerve Injury Using MRI of the Spinal Cord

Brachial plexus injury (BPI) is a devastating type of nerve injury, potentially causing loss of motor and sensory function. Principally, BPI is either categorized as preganglionic or postganglionic, with the early establishment of injury level being crucial for choosing the correct treatment strategy. Despite diagnostic advances, the need for a reliable, non-invasive method for establishing the injury level remains. We studied the usefulness of in vivo magnetic resonance imaging (MRI) of the spinal cord for determination of injury level. The findings were related to neuronal and glial changes. Rats underwent unilateral L4 & L5 ventral roots avulsion or sciatic nerve axotomy. The injuries served as models for pre- and postganglionic BPI, respectively. MRI of the L4/L5 spinal cord segments 4 weeks after avulsion showed ventral horn (VH) shrinkage on the injured side compared to the uninjured side. Axotomy induced no change in the VH size on MRI. Following avulsion, histological sections of L4/L5 revealed shrinkage in the VH grey matter area occupied by NeuN-positive neurons, loss of microtubular-associated protein-2 positive dendritic branches (MAP2), pan-neurofilament positive axons (PanNF), synaptophysin-positive synapses (SYN) and increase in immunoreactivity for the microglial OX42 and astroglial GFAP markers. Axotomy induced no changes in NeuN-reactivity, modest decrease of MAP2 immunoreactivity, no changes in SYN and PanNF labelling, and a modest increase in OX42 and SYN labeling. Histological and radiological findings were congruent when assessing changes after axotomy, while MRI somewhat underestimated the shrinkage. This study indicates a potential diagnostic value of structural spinal cord MRI following BPI.

Long-Standing Motor and Sensory Recovery following Acute Fibrin Sealant Based Neonatal Sciatic Nerve Repair

Brachial plexus lesion results in loss of motor and sensory function, being more harmful in the neonate. Therefore, this study evaluated neuroprotection and regeneration after neonatal peripheral nerve coaptation with fibrin sealant. Thus, P2 neonatal Lewis rats were divided into three groups: AX: sciatic nerve axotomy (SNA) without treatment; AX+FS: SNA followed by end-to-end coaptation with fibrin sealant derived from snake venom; AX+CFS: SNA followed by end-to-end coaptation with commercial fibrin sealant. Results were analyzed 4, 8, and 12 weeks after lesion. Astrogliosis, microglial reaction, and synapse preservation were evaluated by immunohistochemistry. Neuronal survival, axonal regeneration, and ultrastructural changes at ventral spinal cord were also investigated. Sensory-motor recovery was behaviorally studied. Coaptation preserved synaptic covering on lesioned motoneurons and led to neuronal survival. Reactive gliosis and microglial reaction decreased in the same groups (AX+FS, AX+CFS) at 4 weeks. Regarding axonal regeneration, coaptation allowed recovery of greater number of myelinated fibers, with improved morphometric parameters. Preservation of inhibitory synaptic terminals was accompanied by significant improvement in the motor as well as in the nociceptive recovery. Overall, the present data suggest that acute repair of neonatal peripheral nerves with fibrin sealant results in neuroprotection and regeneration of motor and sensory axons.

Erythropoietin Attenuates the Apoptosis of Adult Neurons After Brachial Plexus Root Avulsion by Downregulating JNK Phosphorylation and c-Jun Expression and Inhibiting c-PARP Cleavage

In the present study, the effects of erythropoietin (EPO) on preventing adult neurons from apoptosis (introduced by brachial plexus avulsion) were examined, and the mechanism was analyzed. Fifty injury rat models were established in this study by using micro-hemostat forceps to pull out brachial plexus root from the intervertebral foramen in supine position. These models were divided into EPO group (avulsion + 1000 U/kg subcutaneously on alternate days) and control group (avulsion + normal saline). C5-T1 spinal cord was harvested at days 1, 2, 4, 7, and 14. Compared with the control group, the apoptosis of spinal motoneurons was significantly decreased on days 4 and 7 in the EPO group, which was also approved by TUNEL examination results. The detection of p-JNK and expression of c-Jun and cleavage of cleaved PARP (c-PARP) were also examined by immunohistochemistry and were increased immediately at day 1, and peaked at day 2, day 2, and day 4 in control group, respectively. However, the amounts were decreased and delayed by EPO treatment significantly at the same time points. In conclusion, the apoptosis of adult spinal motorneurons was associated with JNK phosphorylation, c-Jun expression, and caspase activity, and EPO-mediated neuronal protective effect is proved by downregulating the JNK phosphorylation and c-Jun expression and inhibiting of c-PARP cleavage.

Tremor in Charcot-Marie-Tooth disease: No evidence of cerebellar dysfunction

OBJECTIVES

Tremor in Charcot-Marie-Tooth disease (CMT) can be disabling. Cerebellar abnormalities are thought to underpin neuropathic tremor. Here, we aim to clarify the potential role of the cerebellum in CMT tremor.

METHODS

We assessed prevalence of tremor by questionnaire in 84 patients with CMT. Of those, 23 patients with CMT with and without arm tremor and healthy controls underwent a clinical assessment, classical eyeblink conditioning, electro-oculography, visuomotor adaptation test, tremor recording with surface EMG and accelerometry, and retrospective correlation with nerve conduction studies to investigate the possible mechanisms of tremor generation.

RESULTS

The prevalence study revealed tremor in 21% of patients and in 42% of those it caused impairment of function. Tremor recordings revealed a mild-to-moderate amplitude tremor with a weight load-invariant 7.7 Hz frequency component. Performance on classical eyeblink conditioning, visuomotor adaptation and electro-oculography were no different between tremulous and non-tremulous patients and healthy controls.

CONCLUSIONS

These results argue against a prominent role for an abnormal cerebellum in tremor generation in the patients studied with CMT. Rather, our results suggest an enhancement of the central neurogenic component of physiological tremor as a possible mechanism for tremor in the patients studied.

SIGNIFICANCE

This study is the first to propose differing pathogenic mechanisms for subtypes of neuropathic tremor.

Synaptic rearrangement following axonal injury: Old and new players

Following axotomy, the contact between motoneurons and muscle fibers is disrupted, triggering a retrograde reaction at the neuron cell body within the spinal cord. Together with chromatolysis, a hallmark of such response to injury is the elimination of presynaptic terminals apposing to the soma and proximal dendrites of the injured neuron. Excitatory inputs are preferentially eliminated, leaving the cells under an inhibitory influence during the repair process. This is particularly important to avoid glutamate excitotoxicity. Such shift from transmission to a regeneration state is also reflected by deep metabolic changes, seen by the regulation of several genes related to cell survival and axonal growth. It is unclear, however, how exactly synaptic stripping occurs, but there is substantial evidence that glial cells play an active role in this process. In one hand, immune molecules, such as the major histocompatibility complex (MHC) class I, members of the complement family and Toll-like receptors are actively involved in the elimination/reapposition of presynaptic boutons. On the other hand, plastic changes that involve sprouting might be negatively regulated by extracellular matrix proteins such as Nogo-A, MAG and scar-related chondroitin sulfate proteoglycans. Also, neurotrophins, stem cells, physical exercise and several drugs seem to improve synaptic stability, leading to functional recovery after lesion. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Neuroprotective effect of tempol (4 hydroxy-tempo) on neuronal death induced by sciatic nerve transection in neonatal rats

Peripheral nerve injury in newborn rats triggers extensive neuronal death within the spinal cord. Because most neurodegeneration is related to oxidative stress and apoptosis, the use of antioxidants may be of therapeutic interest. Tempol is promising because of its ability to chelate reactive oxygen species and to minimize or even prevent tissue damage. Here, we evaluated neuroprotective effects of tempol following neonatal sciatic nerve transection. Two-day-old pups underwent sciatic nerve axotomy followed by tempol (12, 24 and 48 mg/kg) treatment (i.p.) at 10 min, 6 h, and every 24 h up to 1 week after injury. The rats were then killed for lumbar intumescence analysis. Nissl staining, TUNEL, synaptophysin immunolabeling and qRT-PCR (Caspase 3, Bax and Bcl2) were carried out. The results indicated that tempol treatment, at 24 mg/kg, increased up to 21% spinal cord motoneuron survival (p<0.001), also preserving pre-synaptic terminals in the neuropile. Likewise, the TUNEL-positive cell number decreased in tempol-treated animals. qRT-PCR results indicated differential increase in Caspase 3 (3-fold), Bax (13-fold) and Bcl2 (28-fold) gene expression, after 12 h following axotomy and tempol treatment. In conclusion, tempol administration has proven to be neuroprotective after neonatal nerve injury, leading to improved motoneuron survival, synapse preservation and minimizing apoptosis.

Effects of ischemic phrenic nerve root ganglion injury on respiratory disturbances in subarachnoid hemorrhage: an experimental study

INTRODUCTION

Phrenic nerves have important roles on the management of respiration rhythm. Diaphragm paralysis is possible in phrenic nerve roots ischemia in subarachnoid hemorrhage (SAH). We examined whether there is a relationship between phrenic nerve root ischemia and respiratory disturbances in SAH.

MATERIAL AND METHODS

This study was conducted on 5 healthy control and 14 rabbits with experimentally induced SAH by injecting autologous blood into their cisterna magna. Animals were followed up via monitors for detecting the heart and respiration rhythms for 20 days and then decapitaed by humanely. Normal and degenerated neuron densities of phrenic nerve root at the level of C4 dorsal root ganglia (C4DRG) were estimated by Stereological methods. Between the mean numerical density of degenerated neurons of C4DRG and respiratory rate/minute of groups were compared statistically.

RESULTS

Phrenic nerve roots, artery and diaphragm muscles degeneration was detected in respiratory arrest developed animals. The mean neuronal density of C4DRG was 13272 ±1201/mm3 with a mean respiration rate of 23 ±4/min in the control group. The mean degenerated neuron density was 2.240 ±450/mm(3) and respiration rhythm was 31 ±6/min in survivors. But, the mean degenerated neuron density was 5850 ±650/mm(3) and mean respiration rhythm was 34 ±7/min in respiratory arrest developed animals (n = 7). A linear relationship was noticed between the degenerated neuron density of C4DRG and respiraton rate (r = -0.758; p < 0.001).

CONCLUSIONS

Phrenic nerve root ischemia may be an important factor in respiration rhythms deteriorations in SAH which has not been mentioned in the literature.

Valproic acid protection against the brachial plexus root avulsion-induced death of motoneurons in rats

In this study, the role of valproic acid (VPA) in protecting motoneuron after brachial plexus root avulsion was investigated in adult rats. Sixty rats were used in this study, and underwent the brachial plexus root avulsion injury, which was created by using a micro-hemostat forceps to pull out brachial plexus root from the intervertebral foramen. The animals were divided into two groups, VPA group administered with VPA dissolved in drinking water (300 mg/kg) daily, and control group had drinking water every day. The spinal cords (C5-T1) were harvested at day 1, 2, 3, 7, 14, and 28 for immunohistochemistry analysis, TUNEL staining, Nissl staining, and electron microscopy, respectively. The results showed that with VPA administration, the survival of motoneurons was promoted and the cell apoptosis was inhibited. The number of c-Jun and Bcl-2 positive motoneurons was increased immediately after avulsion both in control and VPA group, however, the percent of c-Jun positive motoneurons was decreased and the percent of Bcl-2 positive motoneurons was increased by VPA treatment significantly. Our results indicated that motoneurons were protected by VPA against cell death induced by brachial plexus root avulsion through c-Jun inhibition and Bcl-2 induction.

Evaluating motor neuron death in neonatal rats subjected to sciatic nerve lesion

Neonatal sciatic nerve lesion is a useful experimental model for the study of neuronal cell death. Sciatic nerve transection or crush is the most frequently used approach to evaluate motoneuron loss in the lumbar enlargement of the spinal cord. Here we describe and illustrate the surgical procedures performed in our laboratory to assess motoneuron cell death and the related cellular mechanisms.

Examining the combinatorial model of motor neuron survival by expression profiling of trophic factors and their receptors in the embryonic Gallus gallus

During embryogenesis, limb-innervating lateral motor column (LMC) spinal motor neurons (MN) are generated in excess and subsequently nearly half of them die. Many motor neuron survival factors (MnSFs) have been shown to suppress this default programmed cell death (PCD) program through their receptors (MnSFRs), raising the possibility that they are involved in matching specific MNs with their target muscles. Published observations suggest a combinatorial model of MnSF/Rs function, which assumes that during the PCD phase, MNs are expressing combinations of MnSFRs, whereas the limb muscles innervated by these MNs express cognate combinations of MnSFs. We tested this model by expression profiling of MnSFs and their receptors in the avian lumbosacral spinal cord and limb muscles during the peak PCD period. Our findings highlight the complexity of MnSF/Rs function in the control of LMC motor neuron survival.

The neuroprotective effects of Reg-2 following spinal cord transection injury

This study was designed to elucidate the potential neuroprotective effects of Reg-2 (regeneration gene protein 2) in a rodent model of spinal cord transection injury at the ninth thoracic level. Reg-2 at 100 and 500 μg, recombinant rat ciliary neurotrophic factor, or vehicle were delivered intrathecally using Alzet miniosmotic pumps. We found that Reg-2 treatment significantly reduced neuronal death in the spinal cord. There was also an attenuation of inflammation at the injury site and an increase in white matter sparing and retained myelination. Retrograde tracing revealed that Reg-2 protected axons of long descending pathways at 6 weeks post-SCI, and the number of FluoroGold-labeled neurons in spinal and supraspinal regions was also significantly increased. Immunofluorescent staining confirmed that the spared white matter contained neurofilament-positive axons. Moreover, behavioral improvements were revealed by Basso Beattie Bresnahan locomotor rating scores and grid-walk analysis. These results suggest that Reg-2 might promote functional recovery by increasing axonal growth, inhibiting neuronal apoptosis, and attenuating spinal cord secondary injury after SCI.

Role of degenerated neuron density of dorsal root ganglion on anterior spinal artery vasospasm in subarachnoid hemorrhage: experimental study

BACKGROUND

The spinal arteries are innervated by several systems that contribute to the control of spinal cord blood flow. The sensory fibers of upper cervical nerves have vasodilatatory effect on the anterior spinal arteries (ASA). Subarachnoid hemorrhage (SAH) causes severe vasospasm by various neurochemical mechanisms. We examined whether there is a relationship between the neuron density of the C3 dorsal root ganglion and the severity of ASA vasospasm in SAH.

METHODS

This study was conducted on 20 rabbits. Four of them were used as baseline group. Experimental SAH has been applied to all of 16 animals by injecting homologous blood into cisterna magna. After 20 days of injection, ASA and C3 dorsal root ganglia (C3DRG) were examined histopathologically. ASA volume values and normal and degenerated neuron densities of C3DRG were estimated stereologically and the results were analyzed statistically.

RESULTS

The mean ASA volume was 1.050±0.450 mm³, [corrected] and the mean neuronal density of C3DRG was 10,500 ± 850 in all animals. The mean volume value of ASA was 0.970±0.150 [corrected] mm³, and the normal neuron density of C3DRG fell to 8,600 ± 400/mm³ in slight vasospasm group. In severe vasospasm-developed animals, mean volume value of ASA was 0.540±0.90 [corrected]mm³ and the normal neuron density of C3DRG fell to 5,500 ± 360/mm³. An inverse relationship between the degenerated neuronal density of the C3DRG and ASA volume values may indicate the severity of ASA vasospasm.

CONCLUSION

The neuron density of C3DRG may be an important factor on the regulation of ASA volume values and the continuation of spinal cord blood flow. Low neuron density of C3DRG may be considered as an important factor in the pathogenesis of severe ASA vasospasm in SAH.

Motoneuron survival after chronic and sequential peripheral nerve injuries in the rat

OBJECT

Surgical repair of peripheral nerves following chronic nerve injury is associated with poor axonal regeneration and outcome. An underlying possibility is that chronic injuries may increase motoneuron cell death. The hypothesis that substantial motoneuron death follows chronic and sequential nerve injuries was tested in adult rats in this study.

METHODS

Thirty adult male Lewis rats underwent bilateral multistage surgeries. At initial surgery, Fast Blue (FB) tracer was injected at a nerve-crush injury site in the right control femoral motor nerve. The left femoral motor nerve was transected at the same level and either capped to prevent regeneration (Group 1), or repaired to allow axonal regeneration and reinnervation of the target quadriceps muscle (Group 2) (15 rats in each group). After 8 weeks in 6 rats/group, the left femoral nerve was cut and exposed to FB just proximal to prior nerve capping or repair and the rats were evaluated for FB-labeled motoneuron counts bilaterally in the spinal cord (this was considered survival after initial injury). In the remaining 9 animals/group, the left nerve was recut (sequential injury), exposed to FB, and repaired to a fresh distal saphenous nerve stump to permit axonal regeneration. Following another 6 weeks, Fluoro-Gold, a second retrograde tracer, was applied to the cut distal saphenous nerve. This allowed us to evaluate the number of motoneurons that survived (maintained FB labeling) and the number of motoneurons that survived but that also regenerated axons (double labeled with FB and Fluoro-Gold).

RESULTS

A mean number of 350 and 392 FB-labeled motoneurons were found after 8 weeks of nerve injury on the right and the left sides, respectively. This indicated no significant cell death due to initial nerve injury alone. A similar number (mean 390) of motoneurons were counted at final end point at 14 weeks, indicating no significant cell death after sequential and chronic nerve injury. However, only 50% (mean 180) of the surviving motoneurons were double labeled, indicating that only half of the population regenerated their axons.

CONCLUSIONS

The hypothesis that significant motoneuron cell death occurs after chronic and or sequential nerve injury was rejected. Despite cell survival, only 50% of motoneurons are capable of exhibiting a regenerative response, consistent with our previous findings of reduced regeneration after chronic axotomy.

Quantitative analysis of multivesicular bodies (MVBs) in the hypoglossal nerve: evidence that neurotrophic factors do not use MVBs for retrograde axonal transport

Multivesicular bodies (MVBs) are defined by multiple internal vesicles enclosed within an outer, limiting membrane. MVBs have previously been quantified in neuronal cell bodies and in dendrites, but their frequencies and significance in axons are controversial. Despite lack of conclusive evidence, it is widely believed that MVBs are the primary organelle that carries neurotrophic factors in axons. Reliable information about axonal MVBs under physiological and pathological conditions is needed for a realistic assessment of their functional roles in neurons. We provide a quantitative ultrastructural analysis of MVBs in the normal postnatal rat hypoglossal nerve and under a variety of experimental conditions. MVBs were about 50 times less frequent in axons than in neuronal cell bodies or dendrites. Five distinct types of MVBs were distinguished in axons, based on MVB size, electron density, and size of internal vesicles. Although target manipulations did not significantly change MVBs in axons, dystrophic conditions such as delayed fixation substantially increased the number of axonal MVBs. Radiolabeled brain- and glial-cell derived neurotrophic factors (BDNF and GDNF) injected into the tongue did not accumulate during retrograde axonal transport in MVBs, as determined by quantitative ultrastructural autoradiography, and confirmed by analysis of quantum dot-labeled BDNF. We conclude that for axonal transport, neurotrophic factors utilize small vesicles or endosomes that can be inconspicuous at transmission electron microscopic resolution, rather than MVBs. Previous reports of axonal MVBs may be based, in part, on artificial generation of such organelles in axons due to dystrophic conditions.

A differential developmental pattern of spinal interneuron apoptosis during synaptogenesis: insights from genetic analyses of the protocadherin-gamma gene cluster

Although the role of developmental apoptosis in shaping the complement and connectivity of sensory and motoneurons is well documented, the extent to which cell death affects the 13 cardinal classes of spinal interneurons is unclear. Using a series of genetic manipulations in vivo, we demonstrate for the first time a differential pattern of developmental apoptosis in molecularly identified spinal interneuron populations, and implicate the adhesion molecule family encoded by the 22-member protocadherin-gamma (Pcdh-gamma) gene cluster in its control. In constitutive Pcdh-gamma null mouse embryos, many interneuron populations undergo increased apoptosis, but to differing extents: for example, over 80% of En1-positive V1 neurons are lost, whereas only 30% of Chx10-positive V2a neurons are lost and there is no reduction in the number of V1-derived Renshaw cells. We show that this represents an exacerbation of a normal, underlying developmental pattern: the extent of each population's decrease in Pcdh-gamma mutants is precisely commensurate both with the extent of its loss during normal embryogenesis and with the extent of its increase in Bax(-/-) mice, in which apoptosis is genetically blocked. Interneuron apoptosis begins during the first wave of synaptogenesisis in the spinal cord, occurring first among ventral populations (primarily between E14 and E17), and only later among dorsal populations (primarily after P0). Utilizing a new, conditional Pcdh-gamma mutant allele, we show that the gamma-Pcdhs can promote survival non-cell-autonomously: mutant neurons can survive if they are surrounded by normal neurons, and normal neurons can undergo apoptosis if they are surrounded by mutant neurons.

Effects of systemic administration of ciliary neurotrophic factor on Bax and Bcl-2 proteins in the lumbar spinal cord of neonatal rats after sciatic nerve transection

Ciliary neurotrophic factor (CNTF) is a cytokine that plays a neuroprotective role in relation to axotomized motoneurons. We determined the effect of daily subcutaneous doses of CNTF (1.2 microg/g for 5 days; N = 13) or PBS (N = 13) on the levels of mRNA for Bcl-2 and Bax, as well as the expression and inter-association of Bcl-2 and Bax proteins, and the survival of motoneurons in the spinal cord lumbar enlargement of 2-day-old Wistar rats after sciatic nerve transection. Five days after transection, the effects were evaluated on histological and molecular levels using Nissl staining, immunoprecipitation, Western blot analysis, and reverse transcriptase-polymerase chain reaction. The motoneuron survival ratio, defined as the ratio between the number of motoneurons counted on the lesioned side vs those on the unlesioned side, was calculated. This ratio was 0.77 +/- 0.02 for CNTF-treated rats vs 0.53 +/- 0.02 for the PBS-treated controls (P < 0.001). Treatment with CNTF modified the level of mRNA, with the expression of Bax RNA decreasing 18% (with a consequent decrease in the level of Bax protein), while the expression of Bcl-2 RNA was increased 87%, although the level of Bcl-2 protein was unchanged. The amount of Bcl-2/Bax heterodimer increased 91% over that found in the PBS-treated controls. These data show, for the first time, that the neuroprotective effect of CNTF on neonatal rat axotomized motoneurons is associated with a reduction in free Bax, due to the inhibition of Bax expression, as well as increased Bcl-2/Bax heterodimerization. Thus, the neuroprotective action of the CNTF on axotomized motoneurons can be related to the inhibition of this apoptotic pathway.

The reduction of proprioceptors in the mesencephalic trigeminal tract nucleus after neonatal masseteric nerve transection; effect of brain-derived neurotrophic factor

The effect of neonatal masseteric nerve transection on primary proprioceptors was examined in the mesencephalic trigeminal tract nucleus (Mes5) of the rat. At 72 h to 21 days after the injury, the number of Mes5 neurons decreased on the side ipsilateral to the transection. The means+/-SD of percentage proportion of ipsilateral/contralateral neurons at 72 h and 21 days were 69.9+/-7.5% and 58.2+/-14.6%, respectively. The application of brain-derived neurotrophic factor to the proximal stump of the masseteric nerve delayed the loss of Mes5 neurons at 72 h after the injury; the mean numbers+/-SD of ipsilateral and contralateral Mes5 neurons in injured animals with BDNF application was 553.6+/-61.9 and 558.4+/-55.3, respectively. Saline application had no effect on the injury-induced loss of Mes5 neurons; i.e., the mean numbers+/-SD of ipsilateral and contralateral Mes5 neurons were 367.3+/-72.5 and 543+/-33.5, respectively. These findings indicate that trigeminal primary proprioceptors are sensitive to the neonatal injury. The survival of proprioceptors during early postnatal period is probably dependent upon brain-derived neurotrophic factor in the trigeminal nervous system.

Spinal motoneuron synaptic plasticity during the course of an animal model of multiple sclerosis

During the course of experimental autoimmune encephalomyelitis, a massive loss of motor and sensitive function occurs, which has been classically attributed to the demyelination process. In rats, the clinical signs disappear within 5 days following complete tetraplegia, indicating that demyelination might not be the only cause for the rapid evolution of the disease. The present work investigated the occurrence of experimental autoimmune encephalomyelitis-induced changes of the synaptic covering of spinal motoneurons during exacerbation and after remission. The terminals were typed with transmission electron microscopy as C-, F- and S-type. Immunohistochemical analysis of synaptophysin, glial fibrillary acidic protein and the microglia/macrophage marker F4/80 were also used in order to draw a correlation between the synaptic changes and the glial reaction. The ultrastructural analysis showed that, during exacerbation, there was a strong retraction of both F- and S-type terminals. In this sense, both the covering as well as the length of the remaining terminals suffered great reductions. However, the retracted terminals rapidly returned to apposition, although the mean length remained shorter. A certain level of sprouting may have occurred as, after remission, the number of F-terminals was greater than in the control group. The immunohistochemical analysis showed that the peak of synaptic loss was coincident with an increased macro- and microglial reaction. Our results suggest that the major changes occurring in the spinal cord network during the time course of the disease may contribute significantly to the origin of the clinical signs as well as help to explain their rapid recovery.

Early dysregulation of cripto-1 and immunomodulatory genes in the cerebral cortex in a macaque model of neuroAIDS

Human immunodeficiency virus type 1 (HIV-1) and related primate lentiviruses are known to enter the central nervous system (CNS) during the primary phase of infection. Neuroinvasion by simian immunodeficiency virus and simian human immunodeficiency virus (SHIV) is characterized by transient meningitis and astrocytosis. In this report, we used targeted cytokine cDNA arrays to analyze cortical brain tissue from four pig-tailed macaques inoculated for 2 weeks with pathogenic SHIV(50OLNV) and a normal age-matched pig-tailed macaque. Our results revealed that eight genes were significantly upregulated in all four macaques. These included: leukocyte interferon inducible peptide, corticotrophin releasing factor receptor 1, interleukin 6, CDW40 antigen, cysteine-rich fibroblast growth factor, neurotrophin 3, ciliary neurotrophin factor receptor and cripto-1. The upregulation of three of these genes was confirmed by reverse transcriptase PCR (RT-PCR). Since cripto-1 had not been previously identified within specific cell types within the primate central nervous system, we performed immunohistochemical studies, which revealed the presence of cripto-1 in neurons. RT-PCR studies demonstrated that cripto-1 mRNA was widely expressed in the CNS. These results indicate that immunomodulatory genes are upregulated during the primary phase of infection of the central nervous system. Cripto-1, which acts as a survival factor in tumor cells and may be neuroprotective, is expressed in neurons within the CNS and is upregulated during viral invasion.

Ganglionary mechanisms of spasticity and ileus in cerebral hemorrhage: an experimental study

OBJECTIVE

The effects of retrograde neuronal death is well determined in dorsal root ganglia (DRG) after peripheral nerve injury, but the effects of intracerebral hemorrhage on the DRG has not been well known. In this study, it was investigated if hemorrhagic lesions of sensory-motor cortex cause neurodegeneration on DRG.

MATERIALS AND METHODS

This study was conducted on 23 male hybrid rabbits. Three of 23 animals were examined as control. Left parietal burr-hole surgery was applied to remaining 20 animals and autolog blood of 0.25ml injected into left sensory-motor region under general anesthesia. All rabbits were followed-up for two months and sacrificed. L(5) DRG's were observed histopathologically. The results were analyzed with Mann-Whitney U-test.

RESULTS

Right spastic hemiplegia developed only in 16 operated animals and 10 of them were developed ileus. The number of degenerated neurons in DRG was higher in the plegic side than in the non-plegic side (p<0.001). But, the difference between the non-plegic side of the study group and control group did not meaningful (p>0.05).

CONCLUSION

Intracerebral hemorrhages affecting the sensory-motor cortex may result in neurodegeneration in DRG. Sensitive reflex arches of striated muscles and bowels may be disturbed due to DRG degeneration and results in spasticity and/or ileus.

Bax and Bcl-2 expression and TUNEL labeling in lumbar enlargement of neonatal rats after sciatic axotomy and melatonin treatment

Peripheral axotomy in neonatal rats induces neuronal death. We studied the anti-apoptotic protein Bcl-2 and cell death promoter Bax in spinal cord of neonatal rats after sciatic transection and treatment with melatonin, a neuroprotective substance. Pups were unilaterally axotomized at P2 and received melatonin (1 mg/kg; sc) or vehicle 1 h prior to lesion, immediately after, at 1 h, 2 h and then once daily. Rats were sacrificed at 3 h, 6 h, 24 h, 72 h and 5 days postaxotomy. Intact animals were used as controls. Lumbar enlargement was processed for Nissl staining, immunohistochemistry and RT-PCR for Bax or Bcl-2 and TUNEL reaction. Motoneurons (MN) of lesioned (L) and normal (N) sides were counted, and MN survival ratio (MSR=L/N) was calculated. Bax and Bcl-2 showed cytoplasmic immunoreactivity (IR). Bax IR was noticeable in small cells but less evident in MN. In unlesioned pups, some Bax-positive small cells (B+) and TUNEL-positive nuclei (T+) were mainly seen in the dorsal horn. In lesioned animals given vehicle, Bax mRNA levels and numbers of B+ and T+ were increased in comparison with intact controls at 24 h postaxotomy. The basal IR for Bax in MN was not changed by axotomy. Bcl-2 IR was noted in all cells and, like Bcl-2 mRNA, was unaltered after lesion. Melatonin reduced MN loss at 24 h, 72 h and 5 days and T+ at 24 h after lesion but did not interfere with Bax or Bcl-2 expression. These results suggest that (1) sciatic transection at P2 increases Bax mRNA and the amount of B+ and T+ in the lumbar enlargement, (2) Bax IR in immature MN is not altered by axotomy and (3) melatonin protects MN and dorsal horn cells through a mechanism independent of Bax and Bcl-2.

ADAPTIVE ROLES OF PROGRAMMED CELL DEATH DURING NERVOUS SYSTEM DEVELOPMENT

The programmed cell death (PCD) of developing cells is considered an essential adaptive process that evolved to serve diverse roles. We review the putative adaptive functions of PCD in the animal kingdom with a major focus on PCD in the developing nervous system. Considerable evidence is consistent with the role of PCD in events ranging from neurulation and synaptogenesis to the elimination of adult-generated CNS cells. The remarkable recent progress in our understanding of the genetic regulation of PCD has made it possible to perturb (inhibit) PCD and determine the possible repercussions for nervous system development and function. Although still in their infancy, these studies have so far revealed few striking behavioral or functional phenotypes.

Abducens internuclear neurons depend on their target motoneurons for survival during early postnatal development

The highly specific projection of abducens internuclear neurons onto medial rectus motoneurons in the oculomotor nucleus is a good model to evaluate the dependence on target cells for survival during development and in the adult. Thus, the procedure we chose to selectively deprive abducens internuclear neurons of their natural target was the enucleation of postnatal day 1 rats to induce the death of medial rectus motoneurons. Two months later, we evaluated both the extent of reduction in target size, by immunocytochemistry against choline acetyltransferase (ChAT) and Nissl counting, and the percentage of abducens internuclear neurons surviving target loss, by calretinin immunostaining and horseradish peroxidase (HRP) retrograde tracing. Firstly, axotomized oculomotor motoneurons died in a high percentage ( approximately 80%) as visualized 2 months after lesion. In addition, we showed a transient (1 month) and reversible down-regulation of ChAT expression in extraocular motoneurons induced by injury. Secondly, 2 months after enucleation, 61.6% and 60.5% of the population of abducens internuclear neurons appeared stained by retrograde tracing and calretinin immunoreaction, respectively, indicating a significant extent of cell death after target loss (38.4% or 39.5%). By contrast, in the adult rat, neither extraocular motoneurons died in response to axotomy nor abducens internuclear neurons died due to the loss of their target motoneurons induced by the retrograde transport of toxic ricin injected in the medial rectus muscle. These results indicate that, during development, abducens internuclear neurons depend on their target motoneurons for survival, and that they lose this dependence with maturation.

Characterisation of transverse slice culture preparations of postnatal rat spinal cord: preservation of defined neuronal populations

Spinal cord injury induces degenerative and regenerative processes and complex interactions of neurons with non-neuronal cells. In order to develop an in vitro tool for the investigation of such processes, we prepared and characterised spinal cord slice cultures (SCSC) from Wistar rats (p0-12). SCSC were sustained in vitro up to 12 days and characterised by immunohistochemistry. Calbindin+ neurons, distributed across the entire gray matter, were visible also after longer culture periods. NeuN+ neurons were best preserved in the dorsal horn whereas large NeuN+ and choline acetyltransferase+ motoneurons in the ventral horn vanished after 3 days in vitro. Nestin immunoreactivity was found in animals of all age groups, either in cells interspersed in the ependymal lining around the central canal or in cells resembling protoplasmic astrocytes. Glial fibrillary acidic protein+ astrocytes, initially restricted to the white matter, invaded the gray matter of SCSC early during the culture period. Microglial cells, stained by Griffonia simplicifolia isolectin B4, were rapidly activated in the dorsal tract and in the gray matter but declined in number with time. SCSC derived from p0 or p3 animals showed a better preservation of the cytoarchitecture than cultures derived from older animals. In summary, SCSC undergo degenerative changes, but they contain defined neuronal populations, the cytoarchitecture is partially preserved and the glial reaction is limited.

Glial-mediated neuroprotection: evidence for the protective role of the NO-cGMP pathway via neuron-glial communication in the peripheral nervous system

The NO-cGMP pathway has emerged as a neuroprotective signaling system involved in communication between neurons and glia. We have previously shown that axotomy or nerve growth factor (NGF)-deprivation of dorsal root ganglion (DRG) neurons leads to increased production of NO and at the same time an increase in cGMP production in their satellite glia cells. Blockade of NO or its receptor, the cGMP synthesizing enzyme soluble guanylate cyclase (sGC), results in apoptosis of neurons and glia. We now show that co-culture of neonatal DRG neurons with either Schwann cells pre-treated with an NO donor or a membrane-permeant cGMP analogue; or neurons maintained in the medium from Schwann cell cultures treated in the same way, prevents neuronal apoptosis. Both NO donor and cGMP treatment of Schwann cells results in synthesis of NGF and NT3. Furthermore, if the Schwann cells are previously infected with adenoviral vectors expressing a dominant negative sGC mutant transgene, treatment of these Schwann cells with an NO donor now fails to prevent neuronal apoptosis. Schwann cells treated in this way also fail to express neither cGMP nor neurotrophins. These findings suggest NO-sGC-cGMP-mediated NGF and NT3 synthesis by Schwann cells protect neurons.

Neuronal NOS deficiency promotes apoptotic cell death of spinal cord neurons after peripheral nerve transection

To study the role of endogenous NO in survival and recovery of spinal cord neurons after nerve lesions, wild type mice were compared to knock-out mice lacking neuronal, endothelial or inducible NO synthase (NOS) after sciatic nerve transection. The NO-generating capacities were assessed by NOS immunohistochemistry and NADPH-diaphorase staining. The feature of affected neurons was evaluated following Nissl- and TUNEL-staining, by immunocytochemical demonstration of cytochrome c-translocation, and by ultrastructural examination. Time point of cell loss was found to be independent of the mice type and occurred only at later post-axotomy states. The extent of neuronal degeneration, however, depended on the NO supply. Whereas a lack of endothelial or inducible NOS was well tolerated, deficiency of neuronal NOS enhanced the competence-to-die and led to a substantial apoptotic cell death of spinal cord neurons. Thus, NO supply turned out to be essential for cell survival and recovery with reference to the neuronal NOS isoform.

Nicotine upregulates nerve growth factor expression and prevents apoptosis of cultured spinal cord neurons

Modulation of neurotrophic factor expression may constitute an important part of neuroprotective effects of nicotine. Therefore, the effects of nicotine on expression of nerve growth factor (NGF) and its receptor, tyrosine receptor kinase A (trkA), were studied in cultured spinal cord neurons treated with arachidonic acid. Because injury to spinal cord is associated with elevated levels of arachidonic acid, this cell culture system has been developed in our laboratory as an in vitro model of neuronal injury in spinal cord trauma. Treatment with nicotine markedly upregulated NGF mRNA and protein expression in spinal cord neurons. In addition, a 12h treatment with nicotine increased mRNA levels of trkA. Both nicotine and exogenous NGF inhibited arachidonic acid induced apoptosis of spinal cord neurons. However, the blockage of the trkA receptor prevented nicotine-mediated anti-apoptotic effects. The present results indicate that increased expression of NGF may be an important element of the neuroprotective effects of nicotine in injured spinal cord neurons.

Viral vector-mediated gene transfer of neurotrophins to promote regeneration of the injured spinal cord

Injuries to the adult mammalian spinal cord often lead to severe damage to both ascending (sensory) pathways and descending (motor) nerve pathways without the perspective of complete functional recovery. Future spinal cord repair strategies should comprise a multi-factorial approach addressing several issues, including optimalization of survival and function of spared central nervous system neurons in partial lesions and the modulation of trophic and inhibitory influences to promote and guide axonal regrowth. Neurotrophins have emerged as promising molecules to augment neuroprotection and neuronal regeneration. Although intracerebroventricular, intrathecal and local protein delivery of neurotrophins to the injured spinal cord has resulted in enhanced survival and regeneration of injured neurons, there are a number of drawbacks to these methods. Viral vector-mediated transfer of neurotrophin genes to the injured spinal cord is emerging as a novel and effective strategy to express neurotrophins in the injured nervous system. Ex vivo transfer of neurotrophic factor genes is explored as a way to bridge lesions cavities for axonal regeneration. Several viral vector systems, based on herpes simplex virus, adenovirus, adeno-associated virus, lentivirus, and moloney leukaemia virus, have been employed. The genetic modification of fibroblasts, Schwann cells, olfactory ensheathing glia cells, and stem cells, prior to implantation to the injured spinal cord has resulted in improved cellular nerve guides. So far, neurotrophic factor gene transfer to the injured spinal cord has led to results comparable to those obtained with direct protein delivery, but has a number of advantages. The steady advances that have been made in combining new viral vector systems with a range of promising cellular platforms for ex vivo gene transfer (e.g., primary embryonic neurons, Schwann cells, olfactory ensheating glia cells and neural stem cells) holds promising perspectives for the development of new neurotrophic factor-based therapies to repair the injured nervous system.

Anti-apoptotic effects of CNTF gene transfer on photoreceptor degeneration in experimental antibody-induced retinopathy

Autoantibodies against recoverin are found in the sera of patients with cancer-associated retinopathy syndrome, a paraneoplastic disease associated with retinal degeneration. We have previously shown that anti-recoverin autoantibodies induced photoreceptor apoptotic cell death after injection into the vitreous of Lewis rats. Ciliary neurotrophic factor (CNTF) has been shown to promote the survival of a number of neuronal cell types, including photoreceptors. In this study, we examined whether an adeno-associated virus (AAV)-mediated delivery of gene encoding the human CNTF protected photoreceptor cells from anti-recoverin antibody-induced death. One month after subretinal injection of the AAV-CNTF gene into one eye and a control vector into the other eye, an anti-recoverin antibody was injected to induce retinal cell death in Lewis rats. Subretinal administration of the virus led to an efficient transduction of photoreceptors, as indicated by immunostaining of retinas with anti-CNTF. Histological examination of the corresponding retinas showed that photoreceptor cells were significantly protected from apoptotic death in the CNTF-treated eyes. CNTF treatment of the retinas resulted in a time-dependent activation of STAT 3. The present study shows that an AAV-mediated delivery of CNTF may protect photoreceptors from antibody-induced cell death through the activation of STAT3 and the suppression of caspase 3 activity, a key caspase leading to apoptosis. Thus, CNTF may be a useful treatment for human antibody-mediated retinal degeneration.

Gamma protocadherins are required for survival of spinal interneurons

The murine genome contains approximately 70 protocadherin (Pcdh) genes. Many are expressed in the nervous system, suggesting that Pcdhs may specify neuronal connectivity. Here, we analyze the 22 contiguous genes of the Pcdh-gamma cluster. Individual neurons express subsets of Pcdh-gamma genes. Pcdh-gamma proteins are present in most neurons and associated with, but not confined to, synapses. Early steps in neuronal migration, axon outgrowth, and synapse formation proceed in mutant mice lacking all 22 Pcdh-gamma genes. At late embryonic stages, however, dramatic neurodegeneration leads to neonatal death. In mutant spinal cord, many interneurons are lost, but sensory and motor neurons are relatively spared. In cultures from mutant spinal cord, neurons differentiate and form synapses but then die. Thus, Pcdh-gamma genes are dispensable for at least some aspects of connectivity but required for survival of specific neuronal types.