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.     

Bone marrow stromal cells enhance inter- and intracortical axonal connections after ischemic stroke in adult rats

We investigated axonal plasticity in the bilateral motor cortices in rats after unilateral stroke and bone marrow stromal cell (BMSC) treatment. Rats were subjected to permanent right middle cerebral artery occlusion followed by intravenous administration of phosphate-buffered saline or BMSCs 1 day later. Adhesive-removal test and modified neurologic severity score were performed weekly to monitor limb functional deficit and recovery. Anterograde tracing with biotinylated dextran amine injected into the right motor cortex was used to assess axonal sprouting in the contralateral motor cortex and ipsilateral rostral forelimb area. Animals were killed 28 days after stroke. Progressive functional recovery was significantly enhanced by BMSCs. Compared with normal animals, axonal density in both contralateral motor cortex and ipsilateral rostral forelimb area significantly increased after stroke. Bone marrow stromal cells markedly enhanced such interhemispheric and intracortical connections. However, labeled transcallosal axons in the corpus callosum were not altered with either stroke or treatment. Both interhemispheric and intracortical axonal sprouting were significantly and highly correlated with behavioral outcome after stroke. This study suggests that, after stroke, cortical neurons surviving in the peri-infarct motor cortex undergo axonal sprouting to restore connections between different cerebral areas. Bone marrow stromal cells enhance axonal plasticity, which may underlie neurologic functional improvement.     

Gliosis and brain remodeling after treatment of stroke in rats with marrow stromal cells

The long-term (4-month) responses to treatment of stroke in the older adult rat, using rat bone marrow stromal cells (MSCs), have not been investigated. Retired breeder rats were subjected to middle cerebral artery occlusion (MCAo) alone, or injected intravenously with 3 x 10(6) MSCs, at 7 days after MCAo. Functional recovery was measured using an adhesive-removal patch test and a modified neurological severity score. Bromodeoxyuridine, a cell proliferation marker, was injected daily for 14 before sacrifice. Animals were sacrificed 4 months after stroke. Double immunostaining was used to identify cell proliferation and cell types for axons, astrocytes, microglia, and oligodendrocytes. MSC treatment induced significant improvement in neurological outcome after MCAo compared with control rats. MSC treatment reduced the thickness of the scar wall (P < 0.05) and reduced the numbers of microglia/macrophages within the scar wall (P < 0.01). Double staining showed increased expression of an axonal marker (GAP-43), among reactive astrocytes in the scar boundary zone and in the subventricular zone in the treated rats. Bromodeoxyuridine in cells preferentially colocalized with markers of astrocytes (GFAP) and oligodendrocytes (RIP) in the ipsilateral hemisphere, and gliogenesis was enhanced in the subventricular zone of the rats treated with MSCs. This is the first report to show that MSCs injected at 7 days after stroke improve long-term neurological outcome in older animals. Brain tissue repair is an ongoing process with reactive gliosis, which persists for at least 4 months after stroke. Reactive astrocytes responding to MSC treatment of ischemia may also promote axonal regeneration during long-term recovery.     

Intracisternal antisense oligonucleotide to growth associated protein-43 blocks the recovery-promoting effects of basic fibroblast growth factor after focal stroke.

Focal infarction (stroke) of the lateral cerebral cortex of rats (including the sensorimotor cortex) produces deficits in sensorimotor function of the contralateral limbs that recover partially over time. In previous studies, we found that the intracisternal injection of basic fibroblast growth factor (bFGF), a potent neurotrophic growth factor, starting at 1 day after stroke, significantly enhanced recovery of sensorimotor function of the contralateral forelimb and hindlimb. Moreover, immunoreactivity (IR) for growth-associated protein-43 (GAP-43), a molecular marker of new axonal growth, was increased in the intact contralateral sensorimotor cortex following bFGF treatment. In the current study, we found that the intracisternal administration of antisense, but not missense, oligonucleotide to GAP-43 blocked the recovery-enhancing effects of bFGF and blocked the increase in GAP-43 IR in the contralateral cortex. These results suggest that upregulation of GAP-43 expression and consequent enhanced axonal sprouting in intact uninjured parts of the brain are likely mechanisms for the recovery-promoting effects of bFGF.     

Extrinsic inhibitors in axon sprouting and functional recovery after spinal cord injur y

The limited axonal growth after central nervous system （CNS） injury such as spinal cord injury presents a major challenge in promoting repair and recovery. The literature in axonal repair has focused mostly on frank regeneration of injured axons. Here, we argue that sprouting of uninjured axons, an innate repair mech- anism of the CNS, might be more amenable to modulation in order to promote functional repair. Extrinsic inhibitors of axonal growth modulate axon sprouting after injury and may serve as the first group of therapeutic targets to promote functional repair.     

Growth-associated gene and protein expression in the region of axonal sprouting in the aged brain after stroke

Aged individuals exhibit reduced functional recovery after stroke. We examined the expression profile in aged animals of a recently identified group of growth-associated genes that underlies post-stroke axonal sprouting in the young adult. Basal levels of most growth-promoting genes are higher in aged cortex compared with young adult, and are further induced after stroke. Compared with the young adult, these genes are induced at later time points after stroke. For growth-inhibitory molecules, myelin-associated glycoprotein and ephrin A5 are uniquely induced in the aged brain; chondroitin sulfate proteoglycans and oligodendrocyte myelin glycoprotein are induced at earlier time points; and Nogo-A, semaphorin IIIa and NG2 decline in aged vs. young adult after stroke. The aged brain does not simply have a reduction in growth-associated molecules after stroke, but a completely unique molecular profile of post-stroke axonal sprouting.     

Allogeneic bone marrow stromal cells promote glial–axonal remodeling without immunologic sensitization after stroke in rats

We evaluated the effects of allogeneic bone marrow stromal cell treatment of stroke on functional outcome, glial–axonal architecture, and immune reaction. Female Wistar rats were subjected to 2 h of middle cerebral artery occlusion. Rats were injected intravenously with PBS, male allogeneic ACI – or syngeneic Wistar –bone marrow stromal cells at 24 h after ischemia and sacrificed at 28 days. Significant functional recovery was found in both cell-treated groups compared to stroke rats that did not receive BMSCs, but no difference was detected between allogeneic and syngeneic cell-treated rats. No evidence of T cell priming or humoral antibody production to marrow stromal cells was found in recipient rats after treatment with allogeneic cells. Similar numbers of Y-chromosome⁺ cells were detected in the female rat brains in both groups. Significantly increased thickness of individual axons and myelin, and areas of the corpus callosum and the numbers of white matter bundles in the striatum were detected in the ischemic boundary zone of cell-treated rats compared to stroked rats. The areas of the contralateral corpus callosum significantly increased after cell treatment compared to normal rats. Processes of astrocytes remodeled from hypertrophic star-like to tadpole-like shape and oriented parallel to the ischemic regions after cell treatment. Axonal projections emanating from individual parenchymal neurons exhibited an overall orientation parallel to elongated radial processes of reactive astrocytes of the cell-treated rats. Allogeneic and syngeneic bone marrow stromal cell treatment after stroke in rats improved neurological recovery and enhanced reactive oligodendrocyte and astrocyte related axonal remodeling with no indication of immunologic sensitization in adult rat brain.     

腺病毒介导Nogo受体特异性RNA干扰对大鼠脑缺血再灌注后轴突再生和神经行为的影响

目的 观察腺病毒介导Nogo受体特异性RNA干扰对大鼠脑缺血再灌注后轴突再生及神经行为的影响.方法 采用线栓法制作大鼠缺血再灌注模型,20只大鼠随机分为假手术组、脑缺血再灌注组和RNAi干预组、阴性对照组.术后24 h、9周行CT测量腩梗死体积,术后行神经功能评分,示踪技术观察皮质红核束和皮质脊髓束.结果 RNAi治疗后脑梗死体积较缺血再灌注组和阴性对照组没有明显变化(P＞0.05),而RNAi治疗3周后,神经功能有明显地恢复(P＜0.01),RNAi治疗9周后健侧皮质红核束发出侧枝支配病灶侧的数量明显增多(P＜0.01).结论 腺病毒介导NgR特异性RNAi可以增加来源于健侧皮质的轴突侧枝出芽,从而促进神经功能的恢复.     

Recovery and brain reorganization after stroke in adult and aged rats

Stroke is a prevalent and devastating disorder, and no treatment is currently available to restore lost neuronal function after stroke. One unique therapy that improves recovery after stroke is neutralization of the neurite inhibitory protein Nogo-A. Here, we show, in a clinically relevant model, improved functional recovery and brain reorganization in the aged and adult rat when delayed anti-Nogo-A therapy is given after ischemic injury. These results support the efficacy of Nogo-A neutralization as treatment for ischemic stroke, even in the aged animal and after a 1-week delay, and implicate neuronal plasticity from unlesioned areas of the central nervous system as a mechanism for recovery.     

Neurogenesis promoted by the CD200/CD200R signaling pathway following treadmill exercise enhances post-stroke functional recovery in rats

Stroke is a leading cause of long-term disability worldwide; survivors often show sensorimotor and cognitive deficits. Therapeutic exercise is the most common treatment strategy for rehabilitating patients with stroke via augmentation of neurogenesis, angiogenesis, neurotrophic factors expression, and synaptogenesis. Neurogenesis plays important roles in sensorimotor and cognitive functional recovery, and can be promoted by exercise; however, the mechanism underlying this phenomenon remains unclear. In this study, we explored the effects of treadmill exercise on sensorimotor and cognitive functional recovery, as well as the potential molecular mechanisms underlying the promotion of neurogenesis in a rat model of transient middle cerebral artery occlusion (tMCAO). We found that treadmill exercise facilitated sensorimotor and cognitive functional recovery after tMCAO, and that neural stem/progenitor cell proliferation, differentiation, and migration were enhanced in the ipsilateral subventricular and subgranular zones after tMCAO. Meanwhile, the newborn neurons induced by treadmill exercise after tMCAO had the similar function with pre-existing neurons. Treadmill exercise significantly increased CD200 and CD200 receptor (CD200R) levels in the ipsilateral hippocampus and cortex. Further study revealed that treadmill exercise-induced neurogenesis and functional recovery were clearly inhibited, while Il-β and Tnf-α expression were upregulated, following lentivirus (LV)-induced suppression of post-stroke CD200R expression. Consistent with the effect of treadmill exercise, CD200Fc (a CD200R agonist) markedly promoted neurogenesis and functional recovery after stroke. In addition, CD200Fc could further enhance the functional recovery induced by treadmill exercise after stroke. Our results demonstrate the beneficial role of treadmill exercise in promoting neurogenesis and functional recovery via activating the CD200/CD200R signaling pathway and improving the inflammatory environment after stroke. Thus, the CD200/CD200R signaling pathway is a potential therapeutic target for functional recovery after stroke.