Voluntary exercise-induced neurogenesis in the postischemic dentate gyrus is associated with spatial memory recovery from stroke

High-intensity interval exercise is more efficient than medium intensity exercise at inducing neurogenesis

The neurogenic potential of the brain decreases during ageing, whereas the risk of neurodegenerative diseases and stroke rises. This creates a mismatch between the rate of neuron loss and the brain's capacity for replacement. Adult neurogenesis primarily occurs in the subgranular zone (SGZ) and the ventricular-subventricular zone (V-SVZ). Exercise enhances SGZ neurogenesis, and we previously showed that V-SVZ neurogenesis is induced by exercise via activation of the lactate receptor HCA1. Here, we investigated how high-intensity interval training (HIIT) and medium-intensity interval training (MIIT) affect neurogenesis in these niches. Wild-type (WT) and HCA1 knockout (KO) mice were randomized to sedentary, HIIT or MIIT (n = 5-8 per group) for 3 weeks. In the SGZ, HIIT increased the density of doublecortin (DCX)-positive cells in WT mice by 85% (5.77±1.76 vs. 3.12±1.54 cells/100 µm, P = 0.013) and KO mice (67% increase; 7.91±2.92 vs. 4.73±1.63 cells/100 µm, P = 0.004). MIIT did not alter the density of DCX-positive cells in either genotype. HIIT increased the density of Ki-67-positive cells only in KO mice (P = 0.038), whereas no differences in nestin-positive cells were observed. In the V-SVZ, HIIT increased the density of DCX-positive cells in WT mice by 155% (117.79±39.72 vs. 46.25±19.96 cells/100 µm, P < 0.001) and MIIT increased the density of DCX-positive cells by 80% (83.26±39.48 vs. 46.25±19.96 cells/100µm, P = 0.027). No exercise-induced changes were observed in KO mice. Similar patterns were noted for Ki-67 positive and DCX/Ki-67 double-positive cells in the V-SVZ. These findings suggest that HIIT enhances neurogenesis more robustly than MIIT in both niches, with HCA1 playing a crucial role in V-SVZ neurogenesis. KEY POINTS: The neurogenic potential of the brain decreases with age, whereas the risk of neurodegenerative diseases and stroke increases, highlighting a mismatch between neuronal loss and replacement capacity. Exercise enhances neurogenesis in both the subgranular zone and the ventricular-subventricular zone. High-intensity interval exercise is more effective than medium-intensity interval exercise at promoting neurogenesis in both the subgranular zone and the ventricular-subventricular zone of wild-type mice. The enhancement of neurogenesis in the ventricular-subventricular zone is dependent on the activation of the HCA1 receptor, as evidenced by the ability of medium- and high-intensity interval exercise to induce neurogenesis in wild-type mice and the lack of this effect in HCA1 knockout mice. By contrast, neurogenesis in the subgranular zone is independent on the activation of the HCA1 receptor, highlighting that neurogenesis in the two major neurogenic niches are regulated differently.

Protective effects of early exercise on neuroinflammation, and neurotoxicity associated by traumatic brain injury: a behavioral and neurochemical approach

OBJECTIVE

The benefits of exercise in TBI have been proven. However, the time-dependent effects of exercise initiation and the involved mechanisms are controversial. We investigated the effects of preconditioning, continuous, early, and delayed treadmill exercise on motor behavior, brain edema, inflammation, and oxidative stress in experimental traumatic brain injury (TBI).

MATERIALS AND METHODS

48 male rats were assigned into two groups: sedentary control (Sham and TBI) and exercise groups: 1MB (preconditioning, initiation beginning at 1 month before trauma), 1MBA (continuous, initiation beginning at 1 month before and continuing 1 month after trauma), 24hA (early, initiation beginning at 24 h after trauma), and 1WA (delay, initiation beginning at 1 week after trauma). The rats in exercise groups were forced to run on a treadmill five days a week for 30 min per day. Rotarod and open file were used to assess motor behavior. ELISA was also used to measure total antioxidant capacity (TAC), tumor necrosis factor-alpha (TNF-α), and malondialdehyde (MDA) in serum and CSF.

RESULTS

Exercise significantly decreased neurological impairments, motor deficits, and apoptosis compared with the sedentary group. Early (within 24 h) and ongoing (1 MBA) exercise significantly improved motor behavior after TBI. In addition, these exercise programs inhibited brain edema and the number of apoptotic cells. MDA and TNF-α levels increased in all exercise groups, but the effects were greater after early exercise than after delayed exercise, resulting in a significant decrease in TAC levels in serum and CSF. We discovered a positive correlation between MDA, TAC, and TNF-α concentration in serum and CSF.

CONCLUSION

Our finding suggests that early exercise (24hA) and 1MBA groups afford neuroprotection and reduce the second injury consequence, probably by reducing neuronal apoptosis and oxidative stress.

Exosomes as a therapeutic tool to promote neurorestoration and cognitive function in neurological conditions: Achieve two ends with a single effort

Exosomes possess a significant role in intercellular communications. In the nervous system, various neural cells release exosomes that not only own a role in intercellular communications but also eliminate the waste of cells, maintain the myelin sheath, facilitate neurogenesis, and specifically assist in normal cognitive function. In neurological conditions including Parkinson's disease (PD), Alzheimer's disease (AD), traumatic brain injury (TBI), and stroke, exosomal cargo like miRNAs take part in the sequela of conditions and serve as a diagnostic tool of neurological disorders, too. Exosomes are not only a diagnostic tool but also their inhibition or administration from various sources like mesenchymal stem cells and serum, which have shown a worthy potential to treat multiple neurological disorders. In addition to neurodegenerative manifestations, cognitive deficiencies are an integral part of neurological diseases, and applying exosomes in improving both aspects of these diseases has been promising. This review discusses the status of exosome therapy in improving neurorestorative and cognitive function following neurological disease.

Early Rehabilitation Exercise after Stroke Improves Neurological Recovery through Enhancing Angiogenesis in Patients and Cerebral Ischemia Rat Model

Among cerebrovascular diseases, ischemic stroke is a leading cause of mortality and disability. Thrombolytic therapy with tissue plasminogen activator is the first choice for clinical treatment, but its use is limited due to the high requirements of patient characteristics. Therefore, the choice of neurological rehabilitation strategies after stroke is an important prevention and treatment strategy to promote the recovery of neurological function in patients. This study shows that rehabilitation exercise 24 h after stroke can significantly improve the neurological function (6.47 ± 1.589 vs. 3.21 ± 1.069 and 0.76 ± 0.852), exercise ability (15.68 ± 5.95 vs. 162.32 ± 9.286 and 91.18 ± 7.377), daily living ability (23.37 ± 5.196 vs. 66.95 ± 4.707 and 6.55 ± 2.873), and quality of life (114.39 ± 7.772 vs. 168.61 ± 6.323 and 215.95 ± 10.977) of patients after 1 month and 3 months, and its ability to promote rehabilitation is better than that of rehabilitation exercise administered to patients 72 h after stroke (p < 0.001). Animal experiments show that treadmill exercise 24 h after middle cerebral artery occlusion and reperfusion can inhibit neuronal apoptosis, reduce the volume of cerebral infarction on the third (15.04 ± 1.07% vs. 30.67 ± 3.06%) and fifth (8.33 ± 1.53% vs. 30.67 ± 3.06%) days, and promote the recovery of neurological function on the third (7.22 ± 1.478 vs. 8.28 ± 1.018) and fifth (4.44 ± 0.784 vs. 6.00 ± 0.767) days. Mechanistic studies have shown that treadmill exercise increases the density of microvessels, regulates angiogenesis, and promotes the recovery of nerve function by upregulating the expression of vascular endothelial growth factor and laminin. This study shows that rehabilitation exercise 24 h after stroke is conducive to promoting the recovery of patients’ neurological function, and provides a scientific reference for the clinical rehabilitation of stroke patients.

Comparison between the persistence of post COVID-19 symptoms on critical patients requiring invasive mechanical ventilation and non-critical patients

Background

During follow-up, patients severely affected by coronavirus disease 2019 (COVID-19) requiring invasive mechanical ventilation (IMV), show symptoms of Post-Intensive Care Syndrome (PICS) such as cognitive impairment, psychological disability, and neuromuscular deconditioning. In COVID-19 pandemic, it is a priority to develop multidisciplinary post-acute care services to address the long-term multisystemic impact of COVID-19.

Research question

Which are the most relevant multisystemic sequelae in severe post-COVID-19 patients?

Study design and methods

Observational chart review study that included adult patients discharged from a referral hospital for respiratory diseases in Mexico after recovering from severe COVID-19 disease from December 23, 2020, to April 24, 2021. Data were collected from 280 of 612 potentially eligible patients to evaluate persistent symptoms and compare sequelae in patients who required intubation, using a standardized questionnaire of symptoms, in addition to findings reported during the face-to-face health assessment. Univariable and multivariate analyses were performed for the association among the requirement of IMV and the long-term persistence of symptoms.

Results

280 patients were included. The median age was 55 (range, 19 to 86) years, and 152 (54.3%) were men. The mean length of hospital stay was 19 (SD, 14.1) days. During hospitalization 168 (60%) participants received IMV.

A large proportion of these patients reported fatigue (38.7%), paresthesia (35.1%), dyspnea (32.7%) and headache (28%); meanwhile only 3 (1.8%) of them were asymptomatic. Patients who required intubation were more likely to have neuropsychiatric (67.3% vs 55.4%; OR, 1.79 [95% CI, 1.08 to 2.97]) and musculoskeletal involvement (38.7% vs. 25.9%; OR, 1.92 [95% CI, 1.12 to 3.27]), adjusted for age,sex and hospitalization time.

Interpretation

The proportion of patients requiring intubation was 60%, reporting persistent symptoms in 98% of them. Neuropsychiatric and musculoskeletal symptoms were the most predominant symptoms in these patients, with a significant difference. Post-COVID-19 syndrome is a frequent problem in patients who required IVM. Physicians in ICU and in care of COVID-19 patients should be aware of this syndrome in order to avoid more complications.

Steroid hormones and hippocampal neurogenesis in the adult mammalian brain

Hippocampal neurogenesis persists across the lifespan in many species, including rodents and humans, and is associated with cognitive performance and the pathogenesis of neurodegenerative disease and psychiatric disorders. Neurogenesis is modulated by steroid hormones that change across development and differ between the sexes in rodents and humans. Here, we discuss the effects of stress and glucocorticoid exposure from gestation to adulthood as well as the effects of androgens and estrogens in adulthood on neurogenesis in the hippocampus. Throughout the review we highlight sex differences in the effects of steroid hormones on neurogenesis and how they may relate to hippocampal function and disease. These data highlight the importance of examining age and sex when evaluating the effects of steroid hormones on hippocampal neurogenesis.

Effect of cycling exercise on motor excitability and gait abnormalities in stroke patients

Background

The concepts of brain excitability are still re-wiring in response to changes in environment. Ambulation is often limited in stroke patients.

Objective

To determine the effect of cycling exercise on motor excitability and consequences on spatiotemporal gait parameters in stroke patients.

Methods

Forty male ischemic stroke patients were included; their age ranged from 45 to 60 years. The patients were assigned into two equal groups: control group (GI) and study group (GII). The GI is treated by a design physical therapy program in the form of task-oriented progressive resistance exercise for lower limb muscles, and the GII is treated by the same program in addition to cycling exercise for 30 min. Treatment was conducted three times per week for 10 weeks. The excitability over motor area (Cz) was assessed by the quantitative electroencephalogram (QEEG). The spatiotemporal gait parameters were assessed by the Biodex Gait Trainer 2TM.

Results

There was a significant increase of speed, step cycle, and step length of the affected side (P < 0.05) and a non-significant difference of step length of the non-affected side in the study group compared with that of the control group (P > 0.05). There was a significant increase of excitability over motor area (Cz) in the study group compared with that of the control group (P < 0.05).

Conclusion

Cycling exercise has a positive effect on excitability over motor area of lower limbs and can improve gait parameters in stroke patients.

Timing is everything: Exercise therapy and remote ischemic conditioning for acute ischemic stroke patients

Physical exercise is a promising rehabilitative strategy for acute ischemic stroke. Preclinical trials suggest that exercise restores cerebral blood circulation and re-establishes the blood–brain barrier’s integrity with neurological function and motor skill improvement. Clinical trials demonstrated that exercise improves prognosis and decreases complications after ischemic events. Due to these encouraging findings, early exercise rehabilitation has been quickly adopted into stroke rehabilitation guidelines. Unfortunately, preclinical trials have failed to warn us of an adverse effect. Trials with very early exercise rehabilitation (within 24 h of ischemic attack) found an inferior prognosis at 3 months. It was not immediately clear as to why exercise was detrimental when performed very early while it was ameliorative just a few short days later. This review aimed to explore the potential mechanisms of harm seen in very early exercise administered to acute ischemic stroke patients. To begin, the mechanisms of exercise’s benefit were transposed onto the current understanding of acute ischemic stroke’s pathogenesis, specifically during the acute and subacute phases. Then, exercise rehabilitation’s mechanisms were compared to that of remote ischemic conditioning (RIC). This comparison may reveal how RIC may be providing clinical benefit during the acute phase of ischemic stroke when exercise proved to be harmful.

Adult Neurogenesis and Stroke: A Tale of Two Neurogenic Niches

In the aftermath of an acute stroke, numerous signaling cascades that reshape the brain both in the perilesional zone as well as in more distal regions are activated. Despite continuous improvement in the acute treatment of stroke and the sustained research efforts into the pathophysiology of stroke, we critically lag in our integrated understanding of the delayed and chronic responses to ischemic injury. As such, the beneficial or maladaptive effect of some stroke-induced cellular responses is unclear, restricting the advancement of therapeutic strategies to target long-term complications. A prominent delayed effect of stroke is the robust increase in adult neurogenesis, which raises hopes for a regenerative strategy to counter neurological deficits in stroke survivors. In the adult brain, two regions are known to generate new neurons from endogenous stem cells: the subventricular zone (SVZ) and the dentate subgranular zone (SGZ) of the hippocampus. While both niches respond with an increase in neurogenesis post-stroke, there are significant regional differences in the ensuing stages of survival, migration, and maturation, which may differently influence functional outcome. External interventions such as rehabilitative training add a further layer of complexity by independently modulating the process of adult neurogenesis. In this review we summarize the current knowledge regarding the effects of ischemic stroke on neurogenesis in the SVZ and in the SGZ, and the influence of exogenous stimuli such as motor activity or enriched environment (EE). In addition, we discuss the contribution of SVZ or SGZ post-stroke neurogenesis to sensory, motor and cognitive recovery.

The Impact of Voluntary Exercise on Stroke Recovery

Stroke treatment is limited to time-critical thrombectomy and rehabilitation by physiotherapy. Studies report beneficial effects of exercise; however, a knowledge gap exists regarding underlying mechanisms that benefit recovery of brain networks and cognition. This study aims to unravel therapeutic effects of voluntary exercise in stroke-induced mice to develop better personalized treatments. Male C57Bl6/JOlaHsd mice were subjected to transient middle cerebral artery occlusion. After surgery, the animals were divided in a voluntary exercise group with access to running wheels (RW), and a control group without running wheels (NRW). During 6 days post-stroke, activity/walking patterns were measured 24/7 in digital ventilated cages. Day 7 post-surgery, animals underwent MRI scanning (11.7T) to investigate functional connectivity (rsfMRI) and white matter (WM) integrity (DTI). Additionally, postmortem polarized light imaging (PLI) was performed to quantify WM fiber density and orientation. After MRI the animals were sacrificed and neuroinflammation and cerebral vascularisation studied. Voluntary exercise promoted myelin density recovery corresponding to higher fractional anisotropy. The deteriorating impact of stroke on WM dispersion was detected only in NRW mice. Moreover, rsfMRI revealed increased functional connectivity, cerebral blood flow and vascular quality leading to improved motor skills in the RW group. Furthermore, voluntary exercise showed immunomodulatory properties post-stroke. This study not only helped determining the therapeutic value of voluntary exercise, but also provided understanding of pathological mechanisms involved in stroke.

Remote Ischemic Postconditioning vs. Physical Exercise After Stroke: an Alternative Rehabilitation Strategy?

There remain debates on neuroprotection and rehabilitation techniques for acute ischemic stroke patients. Therapeutic physical exercise following stroke has shown promise but is challenging to apply clinically. Ischemic conditioning, which has several clinical advantages, is a potential neuroprotective method for stroke rehabilitation that is less understood. In the present study, the rehabilitative properties and mechanisms of physical exercise and remote ischemic postconditioning (RIPostC) after stroke were compared and determined. A total of 248 adult male Sprague-Dawley rats were divided into five groups: (1) sham, (2) stroke, (3) stroke with intense treadmill exercise, (4) stroke with mild treadmill exercise, and (5) stroke with RIPostC. Focal ischemia was evaluated by infarct volume and neurological deficit. Long-term functional outcomes were represented through neurobehavioral function tests: adhesive removal, beam balance, forelimb placing, grid walk, rota-rod, and Morris water maze. To further understand the mechanisms underlying neurorehabilitation and verify the presence thereof, we measured mRNA and protein levels of neuroplasticity factors, synaptic proteins, angiogenesis factors, and regulation molecules, including HIF-1α, BDNF, TrkB, and CREB. The key role of HIF-1α was elucidated by using the inhibitor, YC-1. Both exercise intensities and RIPostC significantly decreased infarct volumes and neurological deficits and outperformed the stroke group in the neurobehavioral function tests. All treatment groups showed significant increases in mRNA and protein expression levels of the target molecules for neurogenesis, synaptogenesis, and angiogenesis, with intermittent further increases in the RIPostC group. HIF-1α inhibition nullified most beneficial effects and indicative molecule expressions, including HIF-1α, BDNF, TrkB, and CREB, in both procedures. RIPostC is equally, or superiorly, effective in inducing neuroprotection and rehabilitation compared to exercise in ischemic rats. HIF-1α likely plays an important role in the efficacy of neuroplasticity conditioning, possibly through HIF-1α/BDNF/TrkB/CREB regulation.

Angiogenin in the Neurogenic Subventricular Zone After Stroke

Ischemic stroke is a leading cause of death and disability worldwide with effective acute thrombolytic treatments. However, brain repair mechanisms related to spontaneous or rehabilitation-induced recovery are still under investigation, and little is known about the molecules involved. The present study examines the potential role of angiogenin (ANG), a known regulator of cell function and metabolism linked to neurological disorders, focusing in the neurogenic subventricular zone (SVZ). Angiogenin expression was examined in the mouse SVZ and in SVZ-derived neural stem cells (NSCs), which were exposed to exogenous ANG treatment during neurosphere formation as well as in other neuron-like cells (SH-SY5Y). Additionally, male C57Bl/6 mice underwent a distal permanent occlusion of the middle cerebral artery to study endogenous and exercise-induced expression of SVZ-ANG and neuroblast migration. Our results show that SVZ areas are rich in ANG, primarily expressed in DCX+ neuroblasts but not in nestin+NSCs. In vitro, treatment with ANG increased the number of SVZ-derived NSCs forming neurospheres but could not modify SH-SY5Y neurite differentiation. Finally, physical exercise rapidly increased the amount of endogenous ANG in the ipsilateral SVZ niche after ischemia, where DCX-migrating cells increased as part of the post-stroke neurogenesis process. Our findings position for the first time ANG in the SVZ during post-stroke recovery, which could be linked to neurogenesis.

Differential Effects of Physical and Social Enriched Environment on Angiogenesis in Male Rats After Cerebral Ischemia/Reperfusion Injury

Different housing conditions, including housing space and the physiological and social environment, may affect rodent behavior. Here, we examined the effects of different housing conditions on post-stroke angiogenesis and functional recovery to clarify the ambiguity about environmental enrichment and its components. Male rats in the model groups underwent right middle cerebral artery occlusion (MCAO) followed by reperfusion. The MCAO rats were divided into four groups: the physical enrichment (PE) group, the social enrichment (SE) group, the combined physical and social enrichment (PSE) group and the ischemia/reperfusion + standard conditioning (IS) group. The rats in the sham surgery (SS) group were housed under standard conditions. In a set of behavioral tests, including the modified Neurological Severity Score (mNSS), rotarod test, and adhesive removal test, we demonstrated that the animals in the enriched condition groups exhibited significantly improved neurological functions compared to those in the standard housing group. Smaller infarction volumes were observed in the animals of the PSE group by MRI detection. The enriched conditions increased the microvessel density (MVD) in the ischemic boundary zone, as revealed by CD31 immunofluorescent staining. The immunochemical and q-PCR results further showed that environmental enrichment increased the expression levels of angiogenic factors after ischemia/reperfusion injury. Our data suggest that all three enrichment conditions promoted enhanced angiogenesis and functional recovery after ischemia/reperfusion injury compared to the standard housing, while only exposure to the combination of both physical and social enrichment yielded optimal benefits.

Post-stroke Neurogenesis: Friend or Foe?

The substantial clinical burden and disability after stroke injury urges the need to explore therapeutic solutions. Recent compelling evidence supports that neurogenesis persists in the adult mammalian brain and is amenable to regulation in both physiological and pathological situations. Its ability to generate new neurons implies a potential to contribute to recovery after brain injury. However, post-stroke neurogenic response may have different functional consequences. On the one hand, the capacity of newborn neurons to replenish the damaged tissue may be limited. In addition, aberrant forms of neurogenesis have been identified in several insult settings. All these data suggest that adult neurogenesis is at a crossroads between the physiological and the pathological regulation of the neurological function in the injured central nervous system (CNS). Given the complexity of the CNS together with its interaction with the periphery, we ultimately lack in-depth understanding of the key cell types, cell-cell interactions, and molecular pathways involved in the neurogenic response after brain damage and their positive or otherwise deleterious impact. Here we will review the evidence on the stroke-induced neurogenic response and on its potential repercussions on functional outcome. First, we will briefly describe subventricular zone (SVZ) neurogenesis after stroke beside the main evidence supporting its positive role on functional restoration after stroke. Then, we will focus on hippocampal subgranular zone (SGZ) neurogenesis due to the relevance of hippocampus in cognitive functions; we will outline compelling evidence that supports that, after stroke, SGZ neurogenesis may adopt a maladaptive plasticity response further contributing to the development of post-stroke cognitive impairment and dementia. Finally, we will discuss the therapeutic potential of specific steps in the neurogenic cascade that might ameliorate brain malfunctioning and the development of post-stroke cognitive impairment in the chronic phase.

The Contribution of Physical Exercise to Brain Resilience

Increasing attention has been given to understanding resilience to brain diseases, often described as brain or cognitive reserve. Among the protective factors for the development of resilience, physical activity/exercise has been considered to play an important role. Exercise is known to induce many positive effects on the brain. As such, exercise represents an important tool to influence neurodevelopment and shape the adult brain to react to life's challenges. Among many beneficial effects, exercise intervention has been associated with cognitive improvement and stress resilience in humans and animal models. Thus, a growing number of studies have demonstrated that exercise not only recovers or minimizes cognitive deficits by inducing better neuroplasticity and cognitive reserve but also counteracts brain pathology. This is evidenced before disease onset or after it has been established. In this review, we aimed to present encouraging data from current clinical and pre-clinical neuroscience research and discuss the possible biological mechanisms underlying the beneficial effects of physical exercise on resilience. We consider the implication of physical exercise for resilience from brain development to aging and for some neurological diseases. Overall, the literature indicates that brain/cognitive reserve built up by regular exercise in several stages of life, prepares the brain to be more resilient to cognitive impairment and consequently to brain pathology.

Voluntary exercise ameliorates the good limb training effect in a mouse model of stroke

Stroke is the leading cause of long-term disability in the United States, making research on rehabilitation imperative. Stroke rehabilitation typically focuses on recovery of the impaired limb, although this process is tedious. Compensatory use of the intact limb after stroke is more efficient, but it is known to negatively impact the impaired limb. Exercise may help with this problem; research has shown that exercise promotes neuronal growth and prevents cell death. This study used a mouse model to investigate if post-stroke exercise could prevent deterioration of the function of the impaired limb despite compensatory training of the intact limb. Results showed that mice that exercised, in combination with intact limb training, demonstrated improved functional outcome compared to mice that received no training or compensatory limb training only. These findings suggest that exercise can prevent the deterioration of impaired limb functional outcome that is typically seen with intact limb use.

Voluntary wheel running promotes improvements in biomarkers associated with neurogenic activity in adult male rats

In rodents, hippocampal neurogenesis and synaptogenesis phenomena are affected by exercise. However, the role of exercise parameters such as intensity, duration, and mode on molecular mechanisms involved in these processes has not been elucidated. In this study, we evaluated the effects of different intensities and modes of running on the expression of genes contributing to neuronal differentiation and synapse formation in the hippocampus of adult male rats. Adult male Wistar rats (n = 24) were randomly divided into control, low-intensity running (LIR), high-intensity running (HIR), and the voluntary wheel running (WR) conditions. Changes in the expression of microRNA-124 (miR-124), microRNA-132 (miR-132), and their respective targets, were analyzed using quantitative RT-PCR and Western blotting techniques. Our results showed that WR compared to treadmill running increased miR-124 and miR-132 expression, while reducing the expression of their respective targets, glucocorticoid receptor (GR), SRY-Box 9 (SOX9), and GTP-activated protein P250 (P250GAP). Differences in expression levels were statistically significant (ps < 0.05), except for the expression of GR in HIR (P = 0.09). Moreover, the expression level of gene coding for the transcription factor cAMP-response element binding protein (CREB) was significantly higher in the WR group compared to the treadmill running groups (P = 0.001). Western blotting techniques indicated that the level of the CREB protein was higher in WR compared to the other groups qualitatively. These findings demonstrated a more dramatic effect for voluntary running on biomarkers that are associated with stimulating neurogenesis and synapse formation in the hippocampus of male rats compared with forced treadmill running. In addition, greater positive effects were observed for lower-intensity treadmill running as compared with high-intensity running.

Exercise reverses learning deficits induced by hippocampal injury by promoting neurogenesis

Hippocampal atrophy and cognitive decline are common sequelae of many neurodegenerative disorders, including stroke. To determine whether cognitive decline can be ameliorated by exercise-induced neurogenesis, C57BL/6 mice in which a unilateral hippocampal injury had been induced by injecting the vasoconstrictor endothelin-1 into their right hippocampus, were run voluntarily for 21 days on a running-wheel. We found the severe deficits in spatial learning, as detected by active place-avoidance task, following injury were almost completely restored in animals that ran whereas those that did not run showed no improvement. We show the increase in neurogenesis found in both the injured and contralateral hippocampi following running was responsible for the restoration of learning since bilateral ablation of newborn doublecortin (DCX)-positive neurons abrogated the cognitive improvement, whereas unilateral ablations of DCX-positive neurons did not prevent recovery, demonstrating that elevated neurogenesis in either the damaged or intact hippocampus is sufficient to reverse hippocampal injury-induced deficits.

Inhibition of LPA5 Activity Provides Long-Term Neuroprotection in Mice with Brain Ischemic Stroke

Stroke is a leading cause of long-term disability in ischemic survivors who are suffering from motor, cognitive, and memory impairment. Previously, we have reported suppressing LPA₅ activity with its specific antagonist can attenuate acute brain injuries after ischemic stroke. However, it is unclear whether suppressing LPA₅ activity can also attenuate chronic brain injuries after ischemic stroke. Here, we explored whether effects of LPA₅ antagonist, TCLPA5, could persist a longer time after brain ischemic stroke using a mouse model challenged with tMCAO. TCLPA5 was administered to mice every day for 3 days, starting from the time immediately after reperfusion. TCLPA5 administration improved neurological function up to 21 days after tMCAO challenge. It also reduced brain tissue loss and cell apoptosis in mice at 21 days after tMCAO challenge. Such long-term neuroprotection of TCLPA5 was associated with enhanced neurogenesis and angiogenesis in post-ischemic brain, along with upregulated expression levels of vascular endothelial growth factor. Collectively, results of the current study indicates that suppressing LPA₅ activity can provide long-term neuroprotection to mice with brain ischemic stroke.

Infusion of Plasma from Exercised Mice Ameliorates Cognitive Dysfunction by Increasing Hippocampal Neuroplasticity and Mitochondrial Functions in 3xTg-AD Mice

Alzheimer’s disease is the most common neurodegenerative brain disease causing dementia. It is characterized by slow onset and gradual worsening of memory and other cognitive functions. Recently, parabiosis and infusion of plasma from young mice have been proposed to have positive effects in aging and Alzheimer’s disease. Therefore, this study examined whether infusion of plasma from exercised mice improved cognitive functions related to the hippocampus in a 3xTg-Alzheimer’s disease (AD) model. We collected plasma from young mice that had exercised for 3 months and injected 100 µL of plasma into the tail vein of 12-month-old 3xTg-AD mice 10 times at 3-day intervals. We then analyzed spatial learning and memory, long-term memory, hippocampal GSK3β/tau proteins, synaptic proteins, mitochondrial function, apoptosis, and neurogenesis. In the hippocampus of 3xTg-AD mice, infusion of plasma from exercised mice improved neuroplasticity and mitochondrial function and suppressed apoptosis, ultimately improving cognitive function. However, there was no improvement in tau hyperphosphorylation. This study showed that plasma from exercised mice could have a protective effect on cognitive dysfunction and neural circuits associated with AD via a tau-independent mechanism involving elevated brain-derived neurotrophic factor due to exercise.

Prenatal stress promotes icv-STZ-induced sporadic Alzheimer's pathology through central insulin signaling change

AIM

Insulin resistance and neuroinflammation play roles in Alzheimer's (AD) etiology. Insulin receptors (IR) are developmentally expressed in neurons as well as astrocytes. Moreover, prolonged stress can induce brain insulin resistance and astrogliosis. Also, prenatal stress could advance AD-related abnormalities in a transgenic model of AD. Besides, postnatal maternal care (PMC) has antagonistic effects on prenatal stress (PS)-induced neuronal and immunological malfunctions. Using an icv-STZ subclinical model of sAD, we assessed PS and/or abnormal PMC impacts on advancing sAD-like pathology in adult male rats. We also sought astrocyte- and/or neuron-oriented change in central insulin programming.

MAIN METHODS

Pregnant rats were exposed to PS. Thereafter, a group of pups was fostered onto unstressed mothers and the others remained intact. Real-time RT-PCR- for hippocampal IR, Tau, and ChAT transcripts- and immunohistochemistry analysis- for GFAP⁺ astrocytes- were performed at the first- and forth-postnatal-week, respectively. The other animals received icv-STZ0.5 mg/kg in adulthood and subjected to cognitive tests, molecular, and histological experiments at appropriate time-point post-injection.

KEY FINDINGS

PS could advance sAD-related symptoms in icv-STZ-treated animals. PS changed expression levels of hippocampal IR in one-week-old and 5.5-month-old offspring. PS could worsen cognitive, molecular and histological impairments of icv-STZ. Adequate PMC prevented some destructive effects of PS.

SIGNIFICANCE

PS can potentially change central insulin programming and induce long-lasting astrogliosis in rat hippocampus. PS-related cognitive and histological pathologies can rescue by PMC probably via IR-dependent pathways. Astrocyte involvement in AD-like neuropathology observed in stressed-animals needs more detailed investigations.

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.

Functions of subventricular zone neural precursor cells in stroke recovery

The proliferation and ectopic migration of neural precursor cells (NPCs) in response to ischemic brain injury was first reported two decades ago. Since then, studies of brain injury-induced subventricular zone cytogenesis, primarily in rodent models, have provided insight into the cellular and molecular determinants of this phenomenon and its modulation by various factors. However, despite considerable correlational evidence-and some direct evidence-to support contributions of NPCs to behavioral recovery after stroke, the causal mechanisms have not been identified. Here we discuss the subventricular zone cytogenic response and its possible roles in brain injury and disease, focusing on rodent models of stroke. Emerging evidence suggests that NPCs can modulate harmful responses and enhance reparative responses to neurologic diseases. We speculatively identify four broad functions of NPCs in the context of stroke: cell replacement, cytoprotection, remodeling of residual tissue, and immunomodulation. Thus, NPCs may have pleiotropic functions in supporting behavioral recovery after stroke.

Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain

Brain Derived Neurotrophic Factor (BDNF) is a key molecule involved in plastic changes related to learning and memory. The expression of BDNF is highly regulated, and can lead to great variability in BDNF levels in healthy subjects. Changes in BDNF expression are associated with both normal and pathological aging and also psychiatric disease, in particular in structures important for memory processes such as the hippocampus and parahippocampal areas. Some interventions like exercise or antidepressant administration enhance the expression of BDNF in normal and pathological conditions. In this review, we will describe studies from rodents and humans to bring together research on how BDNF expression is regulated, how this expression changes in the pathological brain and also exciting work on how interventions known to enhance this neurotrophin could have clinical relevance. We propose that, although BDNF may not be a valid biomarker for neurodegenerative/neuropsychiatric diseases because of its disregulation common to many pathological conditions, it could be thought of as a marker that specifically relates to the occurrence and/or progression of the mnemonic symptoms that are common to many pathological conditions.

The Effects of High-Intensity Aerobic Exercise on Cognitive Performance After Stroke: A Pilot Randomised Controlled Trial

Background:

Aerobic exercise is an effective treatment to improve aerobic capacity following stroke and might also improve cognitive impairments in sub-acute stroke survivors. The aim of the study was to assess the effect of high-intensity aerobic exercise on cognitive impairments in sub-acute stroke survivors.

Methods:

A pilot, randomised controlled trial on the effects of aerobic exercise on cognitive impairments of stroke patients in the sub-acute (1-3 months) phase was conducted. Thirty patients with moderate cognitive impairments (maximum score of 5 on at least two items on the cognitive subscales of the Functional Independence Measure [FIM]) were included in the study and randomly assigned to either the intervention group – performing high-intensity aerobic exercise (above 70% of maximum heart rate), or the control group – performing low-intensity aerobic exercise (below 60%). Patients in both groups exercised for 50 min twice a week for 4 weeks. Primary neuropsychological outcome: Trail Making Test B.

Results:

Thirty stroke patients completed the interventions. The results showed that the high-intensity group, compared with the low-intensity group, achieved significant improvements on Trail Making Test B, which assesses processing speed and divided attention (P = .04 after training and P = .01 at follow-up). However, the significant improvements on Trail Making Test B might relate to a ceiling effect in the control group.

Conclusions:

This study does not provide evidence to support that aerobic exercise can improve cognition in stroke survivors, even though significant improvement was revealed on the primary outcome in sub-acute stroke survivors following high-intensity aerobic exercise compared with low-intensity general exercise.

Abolition of aberrant neurogenesis ameliorates cognitive impairment after stroke in mice

Poststroke cognitive impairment is considered one of the main complications during the chronic phase of ischemic stroke. In the adult brain, the hippocampus regulates both encoding and retrieval of new information through adult neurogenesis. Nevertheless, the lack of predictive models and studies based on the forgetting processes hinders the understanding of memory alterations after stroke. Our aim was to explore whether poststroke neurogenesis participates in the development of long-term memory impairment. Here, we show a hippocampal neurogenesis burst that persisted 1 month after stroke and that correlated with an impaired contextual and spatial memory performance. Furthermore, we demonstrate that the enhancement of hippocampal neurogenesis after stroke by physical activity or memantine treatment weakened existing memories. More importantly, stroke-induced newborn neurons promoted an aberrant hippocampal circuitry remodeling with differential features at ipsi- and contralesional levels. Strikingly, inhibition of stroke-induced hippocampal neurogenesis by temozolomide treatment or using a genetic approach (Nestin-CreERT2/NSE-DTA mice) impeded the forgetting of old memories. These results suggest that hippocampal neurogenesis modulation could be considered as a potential approach for treatment of poststroke cognitive impairment.

Is the "lactormone" a key-factor for exercise-related neuroplasticity? A hypothesis based on an alternative lactate neurobiological pathway

For many years lactate was seen as a metabolite from glucose metabolism. However, since the last century researchers have shown that this molecule has an important role on liver, muscle, and brain metabolism. Lactate traffics along whole body mediating many biological processes depending on specific situations. For example, glucose is the main substrate used during exercise but lactate released by striated skeletal muscle is used by own muscle as secondary fuel. On the other hand, neuronal firing in the brain is almost totally lactate-dependent. In addition, lactate has an important role on BDNF-mediated neuroplasticity. As this molecule has a pleiotropic role in the body, it was called as "lactormone" in 2009. Here we show basic concepts on peripheral and central metabolism and discuss neurobiological pathways of lactate, including an alternative hypothesis on lactate released during exercise.

Effects of Voluntary Wheel-Running Types on Hippocampal Neurogenesis and Spatial Cognition in Middle-Aged Mice

While increasing evidence demonstrated that voluntary wheel running promotes cognitive function, little is known on how different types of voluntary wheel running affect cognitive function in elderly populations. We investigated the effects of various voluntary wheel-running types on adult hippocampal neurogenesis and spatial cognition in middle-aged mice. Male C57BL6 and Thy1-green fluorescent protein (GFP) transgenic mice (13 months) were equally assigned to one of the following groups: (1) T1: no voluntary wheel running; (2) T2: intermittent voluntary wheel running; and (3) T3: continuous voluntary wheel running. The Thy1-GFP transgenic mice were used to specifically label granule cells, since Thy-1 is a promoter for neuronal expression. Behavioral evaluations suggested that intermittent voluntary wheel running improved Morris water maze performance in middle-aged mice. The number of BrdU-positive cells was significantly higher in both intermittent and continuous voluntary wheel running compared with no voluntary wheel running. However, only intermittent voluntary wheel running facilitated the newborn cells to differentiate into granule cells, while newborn cells tended to differentiate into astrocytes and repopulation of microglia was also enhanced in the continuous voluntary wheel-running group. These results indicated that intermittent voluntary exercise may be more beneficial for enhancing spatial memory. Effective improvement of hippocampal neurogenesis was also caused by intermittent voluntary wheel running in middle-aged mice.

Chronic Fluoxetine Induces Activity Changes in Recovery From Poststroke Anxiety, Depression, and Cognitive Impairment

Poststroke depression (PSD) is a common outcome of stroke that limits recovery and is only partially responsive to chronic antidepressant treatment. In order to elucidate changes in the cortical-limbic circuitry associated with PSD and its treatment, we examined a novel mouse model of persistent PSD. Focal endothelin-1-induced ischemia of the left medial prefrontal cortex (mPFC) in male C57BL6 mice resulted in a chronic anxiety and depression phenotype. Here, we show severe cognitive impairment in spatial learning and memory in the stroke mice. The behavioral and cognitive phenotypes were reversed by chronic (4-week) treatment with fluoxetine, alone or with voluntary exercise (free-running wheel), but not by exercise alone. To assess chronic cellular activation, FosB+ cells were co-labeled for markers of glutamate/pyramidal (VGluT1-3/CaMKIIα), γ-aminobutyric acid (GAD67), and serotonin (TPH). At 6 weeks poststroke versus sham (or 4 days poststroke), left mPFC stroke induced widespread FosB activation, more on the right (contralesional) than on the left side. Stroke activated glutamate cells of the mPFC, nucleus accumbens, amygdala, hippocampus, and raphe serotonin neurons. Chronic fluoxetine balanced bilateral neuronal activity, reducing total FosB and FosB/CamKII+ cells (mPFC, nucleus accumbens), and unlike exercise, increasing FosB/GAD67+ cells (septum, amygdala) or both (hippocampus, raphe). In summary, chronic antidepressant but not exercise mediates recovery in this unilateral ischemic PSD model that is associated with region-specific reversal of stroke-induced pyramidal cell hyperactivity and increase in γ-aminobutyric acidergic activity. Targeted brain stimulation to restore brain activity could provide a rational approach for treating clinical PSD.

Early Rehabilitation After Stroke: a Narrative Review

PURPOSE OF REVIEW

Despite current rehabilitative strategies, stroke remains a leading cause of disability in the USA. There is a window of enhanced neuroplasticity early after stroke, during which the brain's dynamic response to injury is heightened and rehabilitation might be particularly effective. This review summarizes the evidence of the existence of this plastic window, and the evidence regarding safety and efficacy of early rehabilitative strategies for several stroke domain-specific deficits.

RECENT FINDINGS

Overall, trials of rehabilitation in the first 2 weeks after stroke are scarce. In the realm of very early mobilization, one large and one small trial found potential harm from mobilizing patients within the first 24 h after stroke, and only one small trial found benefit in doing so. For the upper extremity, constraint-induced movement therapy appears to have benefit when started within 2 weeks of stroke. Evidence for non-invasive brain stimulation in the acute period remains scant and inconclusive. For aphasia, the evidence is mixed, but intensive early therapy might be of benefit for patients with severe aphasia. Mirror therapy begun early after stroke shows promise for the alleviation of neglect. Novel approaches to treating dysphagia early after stroke appear promising, but the high rate of spontaneous improvement makes their benefit difficult to gauge. The optimal time to begin rehabilitation after a stroke remains unsettled, though the evidence is mounting that for at least some deficits, initiation of rehabilitative strategies within the first 2 weeks of stroke is beneficial. Commencing intensive therapy in the first 24 h may be harmful.

Protective Effects of Enriched Environment Against Transient Cerebral Ischemia-Induced Impairment of Passive Avoidance Memory and Long-Term Potentiation in Rats

Introduction

Enriched Environment (EE), a complex novel environment, has been demonstrated to improve synaptic plasticity in both injured and intact animals. The present study investigated the capacity of an early environmental intervention to normalize the impairment of passive avoidance memory and Long-Term Potentiation (LTP) induced by transient bilateral common carotid artery occlusion (2-vessel occlusion, 2VO) in rats.

Methods

After weaning, young Wistar rats (22 days old) were housed in EE or Standard Environment (SE) for 40 days. Transient (30-min) incomplete forebrain ischemia was induced 4 days before the passive avoidance memory test and LTP induction.

Results

The transient forebrain ischemia led to impairment of passive avoidance memory and LTP induction in the Perforant Path-Dentate Gyrus (PP-DG) synapses. Interestingly, housing and growing in EE prior to 2VO was found to significantly reverse 2VO-induced cognitive and LTP impairments.

Conclusion

Our results suggest that early housing and growing in EE exhibits therapeutic potential to normalize cognitive and LTP abnormalities induced by 2VO ischemic model in rats.

Mitochondrial impairments contribute to spatial learning and memory dysfunction induced by chronic tramadol administration in rat: Protective effect of physical exercise

Despite the worldwide use of tramadol, few studies have been conducted about its effects on memory and mitochondrial function, and controversial results have been reported. Recently, there has been an increasing interest in physical exercise as a protective approach to neuronal and cognitive impairments. Therefore, the aim of this study was to investigate the effects of physical exercise on spatial learning and memory and brain mitochondrial function in tramadol-treated rats. After completion of 2-week (short-term) and 4-week (long-term) treadmill exercise regimens, male Wistar rats received tramadol (20, 40, 80mg/kg/day) intraperitoneally for 30days. Then spatial learning and memory was assessed by Morris water maze test (MWM). Moreover, brain mitochondrial function was evaluated by determination of mitochondrial reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), mitochondrial swelling and cytochrome c release from mitochondria. Chronic administration of tramadol impaired spatial learning and memory as well as brain mitochondrial function as indicated by increased ROS level, MMP collapse, increased mitochondrial swelling and cytochrome c release from mitochondria. Conversely, treadmill exercise significantly attenuated the impairments of spatial learning and memory and brain mitochondrial dysfunction induced by tramadol. The results revealed that chronic tramadol treatment caused memory impairments through induction of brain mitochondrial dysfunction. Furthermore, pre-exposure to physical exercise markedly mitigated these impairments through its positive effects on brain mitochondrial function.

Exercise pattern and distance differentially affect hippocampal and cerebellar expression of FLK-1 and FLT-1 receptors in astrocytes and blood vessels

Aerobic exercise benefits the body and brain. In the brain, benefits include neuroprotection and improved cognition. These exercise-induced changes are attributed in part to angiogenesis: the growth of new capillaries from preexisting vessels. One critical factor involved in the regulation of angiogenesis is VEGF and its receptors Flk-1 and Flt-1. Although exercise is generally found to be beneficial, there are wide variations in exercise regimens across experiments. This study standardized some of these variations. Rats were assigned to a voluntary or a forced wheel running exercise condition. Within each condition, animals ran for either a long (1000m) or short distance (500m) for up to 24h. Additionally, one voluntary group had unrestricted access to the wheels for the full 24h. Exercising animals were then compared to inactive controls, based on unbiased stereological quantification of Flk-1 and Flt-1 immunohistochemical labeling in the hippocampus and cerebellum. Findings indicated that voluntary exercise, but not forced exercise, could significantly increase Flk-1 and Flt-1 expression in the hippocampus. Interestingly, Flk-1 expression was elevated in astrocytes and Flt-1 in vessels. In the cerebellum long distance forced exercise resulted in the least Flk-1 expression compared to other conditions, and Flt-1 expression in exercising animals either did not change or was suppressed relative to inactive controls.

The Effects of Early Exercise on Motor, Sense, and Memory Recovery in Rats With Stroke

OBJECTIVE

Exercise is an effective, inexpensive, home-based, and accessible intervention strategy for stroke treatment, and early exercise after stroke has attracted a great deal of attention in recent years. However, the effects of early exercise on comprehensive functional recovery remain poorly understood. The present study investigated the effect of early exercise on motor, sense, balance, and spatial memory recovery.

DESIGN

Adult Sprague-Dawley rats were subjected to unilateral middle cerebral artery occlusion (MCAO) and were randomly divided into early exercise group (EE), non-exercise group (NE), and sham group. EE group received 2 weeks of exercise training initiated at 24 hours after operation. The recovery of motor, sense, and balance function was evaluated every 3 days after MCAO. Spatial memory recovery was detected from 21 to 25 days after MCAO.

RESULTS

The results showed that early exercise significantly promoted the motor and spatial memory recovery with statistical differences. The rats in EE group have a better recovery in sense and balance function, but there is no statistically significant difference about these results.

CONCLUSION

Our results showed that early moderate exercise can significantly promote motor and spatial memory recovery, but not the sense and balance functions.

Exercise as a Positive Modulator of Brain Function

Various forms of exercise have been shown to prevent, restore, or ameliorate a variety of brain disorders including dementias, Parkinson's disease, chronic stress, thyroid disorders, and sleep deprivation, some of which are discussed here. In this review, the effects on brain function of various forms of exercise and exercise mimetics in humans and animal experiments are compared and discussed. Possible mechanisms of the beneficial effects of exercise including the role of neurotrophic factors and others are also discussed.

Effects of Different Exercise Strategies and Intensities on Memory Performance and Neurogenesis

It is well established that physical exercise affects both hippocampal neurogenesis and memory functions. Until now, distinctive effects of controlled and voluntary training (VT) on behavior and neurogenesis as well as interactions between exercise intensity, neurogenesis and memory performance are still elusive. The present study tested the impact of moderate controlled and VT on memory formation and hippocampal neurogenesis and evaluated interactions between exercise performance, learning efficiency and proliferation of progenitor cells in the hippocampus. Our data show that both controlled and VT augmented spatial learning and promoted hippocampal neurogenesis. Regression analysis revealed a significant linear increase of the amount of new hippocampal neurons with increased exercise intensity. Regression analysis of exercise performance on retention memory performance revealed a quadratic, inverted u-shaped relationship between exercise performance and retention of spatial memory. No association was found between the amount of newborn neurons and memory performance. Our results demonstrate that controlled training (CT), if performed with an appropriate combination of speed and duration, improves memory performance and neurogenesis. Voluntary exercise elevates neurogenesis dose dependently to high levels. Best cognitive improvement was achieved with moderate exercise performance.

Influence of Aerobic Training and Combinations of Interventions on Cognition and Neuroplasticity after Stroke

Stroke often aggravated age-related cognitive impairments that strongly affect several aspects of quality of life. However, few studies are, to date, focused on rehabilitation strategies that could improve cognition. Among possible interventions, aerobic training is well known to enhance cardiovascular and motor functions but may also induce beneficial effects on cognitive functions. To assess the effectiveness of aerobic training on cognition, it seems necessary to know whether training promotes the neuroplasticity in brain areas involved in cognitive functions. In the present review, we first explore in both human and animal how aerobic training could improve cognition after stroke by highlighting the neuroplasticity mechanisms. Then, we address the potential effect of combinations between aerobic training with other interventions, including resistance exercises and pharmacological treatments. In addition, we postulate that classic recommendations for aerobic training need to be reconsidered to target both cognition and motor recovery because the current guidelines are only focused on cardiovascular and motor recovery. Finally, methodological limitations of training programs and cognitive function assessment are also developed in this review to clarify their effectiveness in stroke patients.

Long-Term Exercise Improves Memory Deficits via Restoration of Myelin and Microvessel Damage, and Enhancement of Neurogenesis in the Aged Gerbil Hippocampus After Ischemic Stroke

BACKGROUND

The positive correlation between therapeutic exercise and memory recovery in cases of ischemia has been extensively studied; however, long-term exercise begun after ischemic neuronal death as a chronic neurorestorative strategy has not yet been thoroughly examined.

OBJECTIVE

The purpose of this study is to investigate possible mechanisms by which exercise ameliorates ischemia-induced memory impairment in the aged gerbil hippocampus after transient cerebral ischemia.

METHODS

Treadmill exercise was begun 5 days after ischemia-reperfusion (I-R) and lasted for 1 or 4 weeks. The animals were sacrificed 31 days after the induction of ischemia. Changes in short-term memory, as well as the hippocampal expression of markers of cell proliferation, neuroblast differentiation, neurogenesis, myelin and microvessel repair, and growth factors were examined by immunohistochemistry and/or western blots.

RESULTS

Four weeks of exercise facilitated memory recovery despite neuronal damage in the stratum pyramidale (SP) of the hippocampal CA1 region and in the polymorphic layer (PoL) of the dentate gyrus (DG) after I-R. Long-term exercise enhanced cell proliferation and neuroblast differentiation in a time-dependent manner, and newly generated mature cells were found in the granule cell layer of the DG, but not in the SP of the CA1 region or in the PoL of the DG. In addition, long-term exercise ameliorated ischemia-induced damage of myelin and microvessels, which was correlated with increased BDNF expression in the CA1 region and the DG.

CONCLUSIONS

These results suggest that long-term treadmill exercise after I-R can restore memory function through replacement of multiple damaged structures in the ischemic aged hippocampus.

Promoting recovery from ischemic stroke

Over recent decades, experimental and clinical stroke studies have identified a number of neurorestorative treatments that stimulate neural plasticity and promote functional recovery. In contrast to the acute stroke treatments thrombolysis and endovascular thrombectomy, neurorestorative treatments are still effective when initiated days after stroke onset, which makes them applicable to virtually all stroke patients. In this article, selected physical, pharmacological and cell-based neurorestorative therapies are discussed, with special emphasis on interventions that have already been transferred from the laboratory to the clinical setting. We explain molecular and structural processes that promote neural plasticity, discuss potential limitations of neurorestorative treatments, and offer a speculative viewpoint on how neurorestorative treatments will evolve.

Defining Optimal Aerobic Exercise Parameters to Affect Complex Motor and Cognitive Outcomes after Stroke: A Systematic Review and Synthesis

Although poststroke aerobic exercise (AE) increases markers of neuroplasticity and protects perilesional tissue, the degree to which it enhances complex motor or cognitive outcomes is unknown. Previous research suggests that timing and dosage of exercise may be important. We synthesized data from clinical and animal studies in order to determine optimal AE training parameters and recovery outcomes for future research. Using predefined criteria, we included clinical trials of stroke of any type or duration and animal studies employing any established models of stroke. Of the 5,259 titles returned, 52 articles met our criteria, measuring the effects of AE on balance, lower extremity coordination, upper limb motor skills, learning, processing speed, memory, and executive function. We found that early-initiated low-to-moderate intensity AE improved locomotor coordination in rodents. In clinical trials, AE improved balance and lower limb coordination irrespective of intervention modality or parameter. In contrast, fine upper limb recovery was relatively resistant to AE. In terms of cognitive outcomes, poststroke AE in animals improved memory and learning, except when training was too intense. However, in clinical trials, combined training protocols more consistently improved cognition. We noted a paucity of studies examining the benefits of AE on recovery beyond cessation of the intervention.

Therapeutic physical exercise in neural injury: friend or foe?

[Purpose] The intensity of therapeutic physical exercise is complex and sometimes controversial in patients with neural injuries. This review assessed whether therapeutic physical exercise is beneficial according to the intensity of the physical exercise. [Methods] The authors identified clinically or scientifically relevant articles from PubMed that met the inclusion criteria. [Results] Exercise training can improve body strength and lead to the physiological adaptation of skeletal muscles and the nervous system after neural injuries. Furthermore, neurophysiological and neuropathological studies show differences in the beneficial effects of forced therapeutic exercise in patients with severe or mild neural injuries. Forced exercise alters the distribution of muscle fiber types in patients with neural injuries. Based on several animal studies, forced exercise may promote functional recovery following cerebral ischemia via signaling molecules in ischemic brain regions. [Conclusions] This review describes several types of therapeutic forced exercise and the controversy regarding the therapeutic effects in experimental animals versus humans with neural injuries. This review also provides a therapeutic strategy for physical therapists that grades the intensity of forced exercise according to the level of neural injury.

Mechanisms and Functional Significance of Stroke-Induced Neurogenesis

Stroke affects one in every six people worldwide, and is the leading cause of adult disability. After stroke, some limited spontaneous recovery occurs, the mechanisms of which remain largely unknown. Multiple, parallel approaches are being investigated to develop neuroprotective, reparative and regenerative strategies for the treatment of stroke. For years, clinical studies have tried to use exogenous cell therapy as a means of brain repair, with varying success. Since the rediscovery of adult neurogenesis and the identification of adult neural stem cells in the late nineties, one promising field of investigation is focused upon triggering and stimulating this self-repair system to replace the neurons lost following brain injury. For instance, it is has been demonstrated that the adult brain has the capacity to produce large numbers of new neurons in response to stroke. The purpose of this review is to provide an updated overview of stroke-induced adult neurogenesis, from a cellular and molecular perspective, to its impact on brain repair and functional recovery.

Neurogenic effect of VEGF is related to increase of astrocytes transdifferentiation into new mature neurons in rat brains after stroke

To study the cellular mechanism of vascular endothelial growth factor (VEGF)-enhanced neurogenesis in ischemic brain injury, we used middle cerebral artery occlusion (MCAO) model to induce transient focal ischemic brain injury. The results showed that ischemic injury significantly increased glial fibrillary acidic protein immunopositive (GFAP(+)) and nestin(+) cells in ipsilateral striatum 3 days following MCAO. Most GFAP(+) cells colocalized with nestin (GFAP(+)-nestin(+)), Pax6 (GFAP(+)-Pax6(+)), or Olig2 (GFAP(+)-Olig2(+)). VEGF further increased GFAP(+)-nestin(+) and GFAP(+)-Pax6(+) cells, and decreased GFAP(+)-Olig2(+) cells. We used striatal injection of GFAP targeted enhanced green fluorescence protein (pGfa2-EGFP) vectors combined with multiple immunofluorescent staining to trace the neural fates of EGFP-expressing (GFP(+)) reactive astrocytes. The results showed that MCAO-induced striatal reactive astrocytes differentiated into neural stem cells (GFP(+)-nestin(+) cells) at 3 days after MCAO, immature (GFP(+)-Tuj-1(+) cells) at 1 week and mature neurons (GFP(+)-MAP-2(+) or GFP(+)-NeuN(+) cells) at 2 weeks. VEGF increased GFP(+)-NeuN(+) and BrdU(+)-MAP-2(+) newborn neurons after MCAO. Fluorocitrate, an astrocytic inhibitor, significantly decreased GFAP and nestin expression in ischemic brains, and also reduced VEGF-enhanced neurogenic effects. This study is the first time to report that VEGF-mediated increase of newly generated neurons is dependent on the presence of reactive astrocytes. The results also illustrate cellular mechanism of VEGF-enhanced neural repair and functional plasticity in the brains after ischemic injury. We concluded that neurogenic effect of VEGF is related to increase of striatal astrocytes transdifferentiation into new mature neurons, which should be very important for the reconstruction of neurovascular units/networks in non-neurogenic regions of the mammalian brain.