Delayed treatment with monoclonal antibody IN-1 1 week after stroke results in recovery of function and corticorubral plasticity in adult rats.

Neuronal death due to ischemic stroke results in permanent deficits in sensory, language, and motor functions. The growth-restrictive environment of the adult central nervous system (CNS) is an obstacle to functional recovery after stroke and other CNS injuries. In this regard, Nogo-A is a potent neurite growth-inhibitory protein known to restrict neuronal plasticity in adults. Previously, we have found that treatment with monoclonal antibody (mAb) IN-1 to neutralize Nogo-A immediately after stroke enhanced motor cortico-efferent plasticity and recovery of skilled forelimb function in rats. However, immediate treatment for stroke is often not clinically feasible. Thus, the present study was undertaken to determine whether cortico-efferent plasticity and functional recovery would occur if treatment with mAb IN-1 was delayed 1 week after stroke. Adult rats were trained on a forelimb-reaching task, and the middle cerebral artery was occluded to induce focal cerebral ischemia to the forelimb sensorimotor cortex. After 1 week, animals received mAb IN-1 treatment, control antibody, or no treatment, and were tested for 9 more weeks. To assess cortico-efferent plasticity, the sensorimotor cortex opposite the stroke lesion was injected with an anterograde neuroanatomical tracer. Behavioral analysis demonstrated a recovery of skilled forelimb function, and anatomical studies revealed neuroplasticity at the level of the red nucleus in animals treated with mAb IN-1, thus demonstrating the efficacy of this treatment even if administered 1 week after stroke.     

Functional recovery and neuroanatomical plasticity following middle cerebral artery occlusion and IN-1 antibody treatment in the adult rat

Stroke is a prevalent and devastating disorder, and no treatment is currently available to restore lost neuronal function after stroke occurs. One unique therapy that may improve functional recovery after stroke is blockade of the neurite inhibitory protein Nogo-A with the monoclonal antibody IN-1, through enhancement of neuroanatomical plasticity from uninjured areas of the central nervous system. In the present study, we combined IN-1 treatment with an ischemic lesion (permanent middle cerebral artery occlusion) to determine the effect of Nogo-A neutralization on cortical plasticity and functional recovery. We report here that, following ischemic stroke and treatment with IN-1, adult rats demonstrated functional recovery on a forelimb-reaching task and new cortico-efferent projections from the opposite, unlesioned hemisphere. These results support the efficacy of Nogo-A blockade as a treatment for ischemic stroke and implicate plasticity from the unlesioned hemisphere as a mechanism for recovery.     

Increased corticofugal plasticity after unilateral cortical lesions combined with neutralization of the IN-1 antigen in adult rats.

If damage to the central nervous system (CNS) occurs early in life, extensive rearrangements of the remaining fiber systems as well as regeneration of lesioned fibers take place. In the rat or hamster, newly grown projections have been described only if the lesion occurred within the first two weeks postnatally. This decreasing growth ability correlates with CNS maturation and the progression of myelination. Myelin contains the potent neurite growth inhibitors NI-35/250 that are crucially involved in the failure of long-distance regeneration and the lack of compensatory structural plasticity after adult CNS lesions. In this study, we show that extensive remodeling occurs well after the termination of the growth permissive period in the adult rat if we neutralize the inhibitory properties of myelin with the monoclonal antibody IN-1. After ablation of one motor cortex and treatment with the antibody IN-1, we observed that the remaining corticospinal tract (CST) from the spared hemisphere sprouted into the denervated, contralateral red nucleus and pons. In the pons, these fibers terminated in a typical somatotopic pattern. For comparison with neonatal plasticity, we performed the same lesion in two-day-old rats (no antibody). This lesion led as well to sprouting of the remaining CST into denervated brainstem nuclei, resulting in a bilateral corticofugal projection. Our results show that neutralization of myelin-associated neurite-growth inhibitors after CNS lesions leads to a structural remodeling of the spared corticofugal fibers in adult rats, a process normally restricted to a short postnatal period.     

Partial recovery of skilled forelimb reaching after transplantation of fetal cortical tissue in adult rats with motor cortex lesion - anatomical and functional aspects

We have studied the effect of transplantation of embryonic frontal cortex on the motor deficit resulting from motor cortex lesion in the adult rat. Twenty-four 2-month-old rats were first trained in a food reaching task with right and left forelimbs. Then, at 4 months of age, the subjects were divided into two equal groups. In the lesion group, the animals sustained a lesion of the left motor cortex, whereas in the graft group the animals received a fetal cell suspension of embryonic (E16) frontal cortical tissue three days after the lesion. Postoperative reaching ability was assessed every week during eight weeks and then every two months until the age of one year. The results indicate that the deficit resulting from the lesion is bilateral but mainly affects the limb contralateral to the lesion. During the first 3 weeks of postoperative testing, both groups displayed comparable evolution of performance with contralateral forelimb, characterized by an initial large drop followed by progressive recovery. But, whereas in the lesion group performance did not increase after the fourth postoperative week, in the graft group the reaching scores further improved, without recovering, however, preoperative levels. This improvement was still observed eight months after transplantation. However, no improvement appeared using the limb ipsilateral to the transplant. An anatomical study of the volumes of transplant and/or lesion revealed that the importance of the recovery or deficit varied as a function of the sizes of the transplant and/or lesion within the rostral part of the motor cortex, approximately corresponding to the rostral forelimb area of Neafsey et al. [37]. It is therefore suggested that in adult rats, some components of the motor deficit resulting from a lesion of the motor cortex can be partially reduced by transplantation of homotopic embryonic cortex.     

Regenerating corticospinal fibers in the Marmoset (Callitrix jacchus) after spinal cord lesion and treatment with the anti-Nogo-A antibody IN-1

Neutralizing the myelin-associated growth inhibitor Nogo-A in adult spinal cord-injured rats can promote regeneration of injured and compensatory sprouting of uninjured axons. Nogo-A is present in humans, making its neutralization a possible novel treatment option for paraplegic patients. In this study we examined the effects of an extensively used anti-Nogo-A antibody (mAb IN-1) on the regenerative capabilities of lesioned corticospinal tract (CST) axons in a primate, the Marmoset monkey. Unilateral thoracic lesions of the CST were performed in six adult Marmosets, followed by the application of mAb IN-1 into the cerebrospinal fluid circulation by a graft of hybridoma cells. A unilateral injection of biotin dextran amine into the motor cortex was performed to analyse sprouting and regeneration of the lesioned axons. In the control antibody-treated animal CST fibers stopped rostral to the lesion site and often showed retraction bulbs. In contrast, in four out of five mAb IN-1-treated animals fine labeled neurites had grown into, through and around the lesion site. Thus, this study provides first anatomical evidence that in primates, the neutralization of the myelin-associated inhibitor Nogo-A results in increased regenerative sprouting and growth of lesioned spinal cord axons.     

Topical glucocorticoids modulate the lesion interface after cerebral cortical stab wounds in adult rats

A lesion interface, consisting of a glia limitans lined by a laminin-rich basal lamina and leptomeningeal cells, forms within 2–3 weeks after penetrating wounds to the adult mammalian central nervous system (CNS). This interface prevents the growth of axons across the lesion. We have examined the effects of topically applied steroids on the formation of such an interface after stab wounds to the adult rat cerebral cortex. Immediately after lesioning, the surface of cortex in the region of the wound was treated with a topical application of either 0.1% halcinonide or 0.05% betamethasone dipropionate or their respective placebos. Cryostat sections through the lesioned area were obtained 3 weeks later and assessed by immunofluorescence. Steroid treatment attenuated all components of the lesion. The continuous anti-laminin labeling along the lesion in untreated rats became patchy after steroid treatment. The number of leptomeningeal cells that infiltrated into the wound was reduced in the laminin-negative regions in steroid-treated rats. In addition, astrocytic processes in the laminin-negative regions after steroid treatment were loosely arranged, compared with the tightly packed parallel processes forming the glia limitans in laminin-positive regions in controls. The mechanism of steroid-mediated attenuation of the lesion interface was examined in vitro. Betamethasone but not halcinonide reduced laminin secretion slightly in leptomeningeal cell cultures, but both steroids reduced cell proliferation. These results suggest that steroids modulate the formation of the lesion interface after CNS injury, at least in part by decreasing leptomeningeal cell proliferation. Such modulation of the lesion interface by steroids or other agents may permit the growth of axons across the lesion site and thus could enhance the overall degree of axon regeneration if other factors such as neurotrophic support and neutralization of axon growth inhibitory molecules are optimized. © 1996 Wiley-Liss, Inc.     

Electrophysiological analysis of motor cortical plasticity after cortical lesions in newborn rats

Intracortical microstimulation of the motor cortex in normal adult rats evoked low threshold contralateral forelimb movements and high threshold ipsilateral movements. Ablation of the opposite sensorimotor cortex in adult animals did not alter these thresholds. However, stimulation of the unablated hemisphere in adult rats that sustained unilateral sensorimotor cortical lesions as neonates elicited low threshold ipsilateral forelimb movements that were similar to contralateral movements. These low threshold ipsilateral movements may be mediated via aberrant corticofugal pathways which are known to develop following neonatal cortical lesions.     

CNS transplants promote anatomical plasticity and recovery of function after spinal cord injury

We are using neural tissue transplantation after spinal cord injury to identify the rules which determine the response of young neurons to injury, to identify the mechanisms underlying anatomical plasticity and recovery of function following spinal cord injury, and to determine the conditions which change during development, leading to the more restricted growth capacity of mature neurons following injury. Spinal cord lesions at birth interrupt different pathways at different relative stages in their development. Neural tissue transplants modify the response of the immature central nervous system neurons to injury. In the current studies, we have used neuroanatomical and behavioral methods to compare the response of the late-developing corticospinal pathway with that of brainstem-spinal pathways which are intermediate in their development and that of the relatively mature dorsal root pathway. We find that both late-developing and regenerating neuronal populations contribute to the transplant-induced anatomical plasticity, and suggest that this anatomical plasticity underlies the transplant-mediated sparing and recovery of function.     

Anti-Nogo-A antibody treatment promotes recovery of manual dexterity after unilateral cervical lesion in adult primates – re-examination and extension of behavioral data

In rodents and nonhuman primates subjected to spinal cord lesion, neutralizing the neurite growth inhibitor Nogo-A has been shown to promote regenerative axonal sprouting and functional recovery. The goal of the present report was to re-examine the data on the recovery of the primate manual dexterity using refined behavioral analyses and further statistical assessments, representing secondary outcome measures from the same manual dexterity test. Thirteen adult monkeys were studied; seven received an anti-Nogo-A antibody whereas a control antibody was infused into the other monkeys. Monkeys were trained to perform the modified Brinkman board task requiring opposition of index finger and thumb to grasp food pellets placed in vertically and horizontally oriented slots. Two parameters were quantified before and following spinal cord injury: (i) the standard 'score' as defined by the number of pellets retrieved within 30 s from the two types of slots; (ii) the newly introduced 'contact time' as defined by the duration of digit contact with the food pellet before successful retrieval. After lesion the hand was severely impaired in all monkeys; this was followed by progressive functional recovery. Remarkably, anti-Nogo-A antibody-treated monkeys recovered faster and significantly better than control antibody-treated monkeys, considering both the score for vertical and horizontal slots (Mann–Whitney test: P  = 0.05 and 0.035, respectively) and the contact time ( P  = 0.008 and 0.005, respectively). Detailed analysis of the lesions excluded the possibility that this conclusion may have been caused by differences in lesion properties between the two groups of monkeys.     

Motor recovery and anatomical evidence of axonal regrowth in spinal cord-repaired adult rats

Behavioral assessments of hindlimb motor recovery and anatomical assessments of extended axons of long spinal tracts were conducted in adult rats following complete spinal cord transection. Rats were randomly divided into 3 groups: 1) sham control group (laminectomy only; n = 12); 2) transection-only group, spinal cord transection at T8 (n = 20); and 3) experimental treatment group, spinal cord transection at T8, with peripheral nerve grafts (PNG) and application of acidic fibroblast growth factor (aFGF) (n = 14). The locomotor behavior and stepping of all rats were analyzed over a 6-month survival time using the Basso, Beattie, Bresnahan (BBB) open field locomotor test and the contact placing test. Immunohistochemistry for serotonin (5-HT), anterograde tracing with biotinylated dextran amine (BDA), and retrograde tracing with fluoro-gold were used to evaluate the presence of axons below the damage site following treatment. When compared with the transection-only group, the nerve graft with the aFGF group showed 1) significant improvement in hindlimb locomotion and stepping, 2) the presence of 5-HT-labeled axons below the lesion site at lumbar cord level (these were interpreted as regenerated axons from the raphe nuclei), 3) the presence of anterograde BDA labeling of corticospinal tract axons at the graft site and below, and 4) fluoro-gold retrograde labeling of neuron populations in motor cortex and in red nucleus, reticulospinal nuclei, raphe nuclei, and vestibular nuclei. We conclude that peripheral nerve grafts and aFGF treatments facilitate the regrowth of the spinal axons and improve hindlimb function in a T-8 spinal cord-transected rat model.     

Neurophysiological and anatomical plasticity in the adult sensorimotor cortex

Evidence supporting the plastic capacity of the adult cortex is abundant. Changes have been associated with exposure to enriched environments, learning, peripheral lesions and central lesions. The initial loss of function caused by a lesion is generally followed by a certain amount of recovery that is believed to be due, at least in part, to adaptive plasticity. In particular, the reorganization of cortical representational maps has been associated with improvement of performance. Therefore, areas undergoing such reorganization following lesions are generally assumed to participate in the recovery. We review evidence demonstrating the remodeling of representational maps of the forelimb in adult cortex and the structural plasticity that has been coupled with it. A particular emphasis is paid to non-human primate studies and stroke.     

Reduced plasticity of cortical whisker representation in adult tenascin-C-deficient mice after vibrissectomy

The effect of the extracellular matrix recognition molecule tenascin-C on cerebral plasticity induced by vibrissectomy was investigated with 2-deoxyglucose (2DG) brain mapping in tenascin-C-deficient mice. Unilateral vibrissectomy sparing row C of vibrissae was performed in young adult mice. Two months later, cortical representations of spared row C vibrissae and control row C on the other side of the snout were visualized by [(14)C]2DG autoradiography. In both wild-type and tenascin-C-deficient mice, cortical representation of the spared row was expanded in all layers of the barrel cortex. However, the effect was significantly more extensive in wild-type animals than in the mutant. Elimination of tenascin-C by genetic manipulation thus reduces the effect of vibrissectomy observed in the somatosensory cortex. No increase in number of fibres in the vibrissal nerve of spared vibrissae was seen, and occurrence of additional nerve to the spared follicle was very rare. Thus, in tenascin-C-deficient mice functional plasticity seems to be impaired within the CNS.     

On nature and limits of cortical developmental plasticity after an early lesion,in a child

MS is a little girl who suffered severe, bilateral destruction of her primary visual areas at six weeks, after premature birth at 30 weeks. Between the ages of 4.5 and 5.5 years she partially recovered different aspects of visual function, and, in particular, the ability to segregate figures from background, based on texture cues. The recovery might have been due to the compensatory role of the remaining visual areas that could have acquired response properties similar to those of the primary visual areas. This is not supported by the available FMRI (functional magnetic resonance imaging) responses to visual stimuli. Instead, abnormalities in the pattern of stimulus-induced changes of interhemi-spheric EEG-coherence in this patient suggest that her visual callosal connections, and possibly other cortico-cortical connections have re-organized abnormally. Since cortico-cortical connections, including the callosal ones appear to be involved in perceptual binding and figure-background segregation, their reorganization could be an important element in the functional recovery after early lesion, and/or in the residual perceptual impairment.     

Spontaneous locomotor recovery in spinal cord injured rats is accompanied by anatomical plasticity of reticulospinal fibers

Although injured axons in mammalian spinal cords do not regenerate, some recovery of locomotor function following incomplete injury can be observed in patients and animal models. Following a lateral hemisection injury of the thoracic spinal cord, rats spontaneously recover weight-bearing stepping in the hind limb ipsilateral to the injury. The mechanisms behind this recovery are not completely understood. Plasticity in the reticulospinal tract (RtST), the tract responsible for the initiation of walking, has not been studied. In this study, rats received lateral thoracic hemisection of the spinal cord, and RtST projections were compared in two groups of rats, one early in recovery (7 days) and the other at a time point when weight-bearing stepping was fully regained (42 days). We found that this recovery occurs in parallel with increased numbers of collaterals of spared RtST fibers entering the intermediate lamina below the injury at L2. Sprouting of injured RtST fibers above the lesion was not found. In conclusion, our study suggests that sprouting of spared RtST fibers might be involved in the recovery of locomotion following incomplete spinal cord injury.     

Effects of differential environments on plasticity of dendrites of cortical pyramidal neurons in adult rats

Thickening of the frontal cortex and especially the occipital cortex was observed in adult rats after exposure to the “enriched” condition. An increase in branching and in length of terminal segments was found in the dendritic tree of pyramidal cells in layers II and III of the visual cortex of the adult rat after exposure to “standard” and enriched conditions. These exposures began at day 112 and continued 30 days. The increase observed in the basal dendritic tree of pyramidal cells in the superficial layers was significantly greater in the enriched conditions than in the standard condition. It appeared, furthermore, that branching occurred predominantly on basal terminal segments of all orders at a considerable distance from the tip. This mode of growth is similar to that observed in the cortex of normal immature rats. The differential conditions did not influence the bifurcation angles. The dendritic and cortical changes and changes reported in the literature indicate that the effects of differential experience are not limited to a short, “critical” period.     

Alterations in medial prefrontal cortical activity and plasticity in rats with disruption of cortical development.

BACKGROUND: Psychiatric disorders such as schizophrenia are believed to emerge from an interaction of several factors. Thus, a genetic predisposition can lead to developmental compromises that may leave the system more susceptible to deficits induced by subsequent environmental variables such as stress. METHODS: The impact of neurodevelopmental interruption induced by exposure of rats prenatally to a compound methylazoxymethanol acetate (MAM) that disrupts neuronal proliferation was investigated using in vivo electrophysiologic recordings from the prefrontal cortex of adult rats. RESULTS: Prenatal exposure to MAM resulted in alterations in the medial prefrontal cortex indicative of a compromise in information processing. Specifically, we observed a disruption in activity patterns consistent with deficits in neuronal synchronization and abnormal augmentation of synaptic plasticity that was more severely disrupted by stress exposure than in normal animals. Furthermore, these deficits could be reversed by manipulating the mesocortical dopamine system. CONCLUSIONS: These results suggest that disruption of early cortical development causes impairments in medial prefrontal cortical function at adulthood that are more vulnerable to disruptive influences, despite the presence of only subtle structural alterations in the brain.     

Cortical electrical stimulation combined with rehabilitative training: enhanced functional recovery and dendritic plasticity following focal cortical ischemia in rats

This study assessed the behavioral and dendritic structural effects of combining subdural motor cortical electrical stimulation with motor skills training following unilateral sensorimotor cortex lesions in adult male rats. Rats were pre-operatively trained on a skilled forelimb reaching task, the Montoya staircase test, and then received endothelin-1 induced ischemic lesions of the sensorimotor cortex. Ten to 14 days later, electrodes were implanted over the peri-lesion cortical surface. Rats subsequently began 10 days of rehabilitative training on the reaching task in 1 of 3 conditions: 1. 50 Hz stimulation during training, 2. 250 Hz stimulation during training or 3. no stimulation. No significant difference in performance was found between the 250 Hz and no stimulation groups. The 50 Hz stimulation group had significantly greater rates of improvement with the impaired forelimb in comparison to 250 Hz and no stimulation groups combined. Fifty Hz stimulated animals also had a significant increase in the surface density of dendritic processes immunoreactive for the cytoskeletal protein, microtubule-associated protein 2, in the peri-lesion cortex compared to the other groups. These results support the efficacy of combining rehabilitative training with cortical electrical stimulation to improve functional outcome and cortical neuronal structural plasticity following sensorimotor cortical damage.     

Cortical electrical stimulation combined with rehabilitative training: Enhanced functional recovery and dendritic plasticity following focal cortical ischemia in rats

Abstract

This study assessed the behavioral and dendritic structural effects of combining subdural motor cortical electrical stimulation with motor skills training following unilateral sensorimotor cortex lesions in adult male rats. Rats were pre-operatively trained on a skilled forelimb reaching task, the Montoya staircase test, and then received endothelin-1 induced ischemic lesions of the sensorimotor cortex. Ten to 14 days later, electrodes were implanted over the peri-lesion cortical surface. Rats subsequently began 10 days of rehabilitative training on the reaching task in 1 of 3 conditions: 1. 50 Hz stimulation during training, 2. 250 Hz stimulation during training or 3. no stimulation. No significant difference in performance was found between the 250 Hz and no stimulation groups. The 50 Hz stimulation group had significantly greater rates of improvement with the impaired forelimb in comparison to 250 Hz and no stimulation groups combined. Fifty Hz stimulated animals also had a significant increase in the surface density of dendritic processes immunoreactive for the cytoskeletal protein, microtubule-associated protein 2, in the peri-lesion cortex compared to the other groups. These results support the efficacy of combining rehabilitative training with cortical electrical stimulation to improve functional outcome and cortical neuronal structural plasticity following sensorimotor cortical damage.     

Motor cortical excitability and plasticity in patients with neurofibromatosis type 1

ObjectiveNeurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that is associated with cognitive disabilities. Based on studies involving animals, the hypothesized cause of these disabilities results from increased activity of inhibitory interneurons that decreases synaptic plasticity. We obtained transcranial magnetic stimulation (TMS)-based measures of cortical inhibition, excitability and plasticity in individuals with NF1.MethodsWe included 32 NF1 adults and 32 neurotypical controls. Cortical inhibition was measured with short-interval intracortical inhibition (SICI) and cortical silent period (CSP). Excitability and plasticity were studied with intermittent theta burst stimulation (iTBS).ResultsThe SICI and CSP response did not differ between NF1 adults and controls. The response upon iTBS induction was significantly increased in controls (70%) and in NF1 adults (83%). This potentiation lasted longer in controls than in individuals with NF1. Overall, the TMS response was significantly lower in NF1 patients (F(1, 41) = 7.552, p = 0.009).ConclusionsIndividuals with NF1 may have reduced excitability and plasticity, as indicated by their lower TMS response and attenuation of the initial potentiated response upon iTBS induction. However, our findings did not provide evidence for increased inhibition in NF1 patients.SignificanceThese findings have potential utility as neurophysiological outcome measures for intervention studies to treat cognitive deficits associated with NF1.     

LINGO-1多克隆抗体对大鼠脊髓损伤模型干预的可行性分析

目的 探讨脊髓损伤(SCI)处局部给予LINGO-1多克隆抗体治疗的可行性. 方法 24只成年雌性SD大鼠采用随机数字表法分为假手术组、半横断对照IgG组及半横断LINGO-1多克隆抗体组,每组8只.假手术组仅行椎板切除术,另外两组均行T9脊髓半横断术,半横断LINGO-1多克隆抗体组大鼠半横断损伤后立刻通过微量渗透泵局部给予损伤处LINGO-1多克隆抗体,而半横断对照IgG组仅给予兔源性对照IgG.术后3 d和28 d取各组T8～10节段脊髓制作冰冻切片,应用免疫荧光染色方法 观察分析LINGO-1多克隆抗体是否进入脊髓组织并与LINGO-1分子特异性结合. 结果半横断LINGO-1多克隆抗体组大鼠SCI术后3 d和28 d均可检测出兔源性抗体;术后3 d,半横断对照IgG组切片LINGO-1染色强度(1.704±0.174)明显强于半横断LINGO-1多克隆抗体组(0.568±0.052),LINGO-1多克隆抗体预处理后的半横断对照1g3组切片LINGO-1染色强度(0.329±0.055)明显弱于半横断对照lgG组(1.704±0.174)切片,比较差异均有统计学意义(P<0.05). 结论 局部给予的LINGO-1多克隆抗体在较宽的时间窗里均可进入SCI区并特异性识别LINGO-1分子,证明被动免疫治疗SCI是可行的.