Exercise therapy augments the ischemia-induced proangiogenic state and results in sustained improvement after stroke

Endothelial cell-derived extracellular vesicles induce pro-angiogenic responses in mesenchymal stem cells

Angiogenesis is a central component of vital biological processes such as wound healing, tissue nourishment, and development. Therefore, angiogenic activities are precisely maintained with secreted factors such as angiopoietin-1 (Ang1), fibroblast growth factor (FGF), and vascular endothelial growth factor (VEGF). As an element of intracellular communication, extracellular vesicles (EVs)-particularly EVs of vascular origin-could have key functions in maintaining angiogenesis. However, the functions of EVs in the control of angiogenesis have not been fully studied. In this study, human umbilical vein endothelial cell line (HUVEC)-derived small EVs (<200 nm; HU-sEVs) were investigated as a potential pro-angiogenic agent. Treating mesenchymal stem cells (MSCs) and mature HUVEC cells with HU-sEVs induced their tube formation under in vitro conditions and significantly increased the expression of angiogenesis-related genes, such as Ang1, VEGF, Flk-1 (VEGF receptor 2), Flt-1 (VEGF receptor 1), and vWF (von Willebrand Factor), in a dose-dependent manner. These results indicate that HU-sEVs take part in angiogenesis activities in physiological systems, and suggest endothelial EVs as a potential therapeutic candidate for the treatment of angiogenesis-related diseases.

Resistance exercise promotes the resolution and recanalization of deep venous thrombosis in a mouse model via SIRT1 upregulation

BACKGROUND

Early exercise for acute deep venous thrombosis (DVT) improves the patient's symptoms and does not increase the risk of pulmonary embolism. However, information about its effect on thrombus resolution is limited. The aim of this study was to investigate the role of resistance exercise (RE) in thrombus resolution and recanalization and determine its underlying mechanisms.  METHODS: Ninety-six C57BL/6 J mice were randomly divided into four groups: Control group (C, n = 24); DVT group (D, n = 24); RE + DVT group (ED, n = 24); and inhibitor + RE + DVT group (IED, n = 24). A DVT model was induced by stenosis of the inferior vena cava (IVC). After undergoing IVC ultrasound within 24 h post-operation to confirm DVT formation, mice without thrombosis were excluded. Other mice were sacrificed and specimens were obtained 14 or 28 days after operation. Thrombus-containing IVC was weighed, and the thrombus area and recanalization rate were calculated using HE staining. Masson's trichrome staining was used to analyze the collagen content. RT-PCR and ELISA were performed to examine IL-6, TNF-α, IL-10, and VEGF expression levels. SIRT1 expression was assessed using immunohistochemistry staining and RT-PCR. VEGF-A protein expression and CD-31-positive microvascular density (MVD) in the thrombus were observed using immunohistochemistry.  RESULTS: RE did not increase the incidence of pulmonary embolism. It reduced the weight and size of the thrombus and the collagen content. Conversely, it increased the recanalization rate. It also decreased the levels of the pro-inflammatory factors IL-6 and TNF-α and increased the expression levels of the anti-inflammatory factor IL-10. RE enhanced VEGF and SIRT1 expression levels and increased the MVD in the thrombosis area. After EX527 (SIRT1 inhibitor) was applied, the positive effects of exercise were suppressed.

CONCLUSIONS

RE can inhibit inflammatory responses, reduce collagen deposition, and increase angiogenesis in DVT mice, thereby promoting thrombus resolution and recanalization. Its underlying mechanism may be associated with the upregulation of SIRT1 expression.

A review of remote ischemic conditioning as a potential strategy for neural repair poststroke

Ischemic stroke is one of the major disabling health-care problem and multiple different approaches are needed to enhance rehabilitation, in which neural repair is the structural basement. Remote ischemic conditioning (RIC) is a strategy to trigger endogenous protect. RIC has been reported to play neuroprotective role in acute stage of stroke, but the effect of RIC on repair process remaining unclear. Several studies have discovered some overlapped mechanisms RIC and neural repair performs. This review provides a hypothesis that RIC is a potential therapeutic strategy on stroke rehabilitation by evaluating the existing evidence and puts forward some remaining questions to clarify and future researches to be performed in the field.

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.

Lactate as Potential Mediators for Exercise-Induced Positive Effects on Neuroplasticity and Cerebrovascular Plasticity

The accumulated evidence from animal and human studies supports that exercise is beneficial to physical health. Exercise can upregulate various neurotrophic factors, activate neuroplasticity, and play a positive role in improving and enhancing cerebrovascular function. Due to its economy, convenience, and ability to prevent or ameliorate various aging-related diseases, exercise, a healthy lifestyle, is increasingly popularized by people. However, the mechanism by which exercise performs this function and how it is transmitted from muscles to the brain remains incompletely understood. Here, we review the beneficial effects of exercise with different intensities on the brain with a focus on the positive effects of lactate on neuroplasticity and cerebrovascular plasticity. Based on these recent studies, we propose that lactate, a waste previously misunderstood as a by-product of glycolysis in the past, may be a key signal molecule that regulates the beneficial adaptation of the brain caused by exercise. Importantly, we speculate that a central protective mechanism may underlie the cognitive benefits induced by exercise.

The Effect of Ophiocephalus striatus sp. Extract on Nitric Oxide in Ischemic Stroke Model

BACKGROUND: One of alternative medicine in stroke therapy is Ophiocephalus striatus sp. extract. The nutrients contained in the O. striatus sp. extract, namely amino acids, fatty acids, cuprum, and zinc, are useful for the process of angiogenesis in poststroke patients through increased endothelial nitric oxide synthase. AIM: We hypothesized that there was an effect of giving O. striatus sp. extract to cerebral angiogenesis process of Sprague Dawley rats ischemic stroke models through the level of NO. METHODS: This was evidenced by conducting experimental studies on rats ischemic stroke models which were divided into five groups, (a) K (−) group (no ligation, no treatment), (b) K (+) group (ligation, no treatment), (c) P1 group (ligation, 200 mg extract), (d) P2 group (ligation, 400 mg extract), and (e) P3 group (ligation, 800 mg extract). Then blood sample was taken on day 3 to assess levels of NO. RESULTS: There was increased level of NO in P1 (p = 0.001), P2 (p < 0.001), and P3 (p < 0.001) groups compared to K (+) group. The level of NO increases along with the increasing dose of O. striatus sp. extract. Histological examination revealed that there was formation of new blood vessel in the P1, P2, and P3 groups compared to K (+) group. CONCLUSION: Our study showed that O. striatus sp. extract improves cerebral angiogenesis in rat models of ischemic stroke.

The Effect of Two Types of Exercise Preconditioning on the Expression of TrkB, TNF-α, and MMP2 Genes in Rats with Stroke

Despite the beneficial effects of exercise and physical activity, there is little knowledge about the effects of different types of physical activity on neural function. The present study assessed the effects of two types of selected aerobic exercises prior to stroke induction and characterized the expression of TrkB, TNF-α, and MMP2 genes in vivo. Forty male adult Wistar rats were exposed to aerobic exercises following randomization into four groups, including swimming + MCAO (Middle Cerebral Artery Occlusion) (n = 10), treadmill training + MCAO (n = 10), MCAO (n = 10), and control (n = 10). The swimming + MCAO group included swimming for 30 minutes each day, while the treadmill training + MCAO group program involved running for 30 minutes each day at an intensity of 15 m/min, for three weeks, five days a week. Neurological deficit was assessed using modified criteria at 24 h after the onset of cerebral ischemia. In the control group, the animals worked freely for three weeks without undergoing ischemia. The MCAO group also operated freely for three weeks after they underwent a stroke. Both training groups underwent ischemia after three weeks of training. TrkB, TNF-α, and MMP2 gene expressions were increased in the MCAO+ swimming training and in the MCAO + running training group compared to the control and MCAO groups, respectively. Preconditioning aerobic exercises significantly increased brain trophic support and reduced brain damage conditions in exercise groups, which support the importance of aerobic exercise in the prevention and treatment of stroke.

Biomarkers of Angiogenesis and Neuroplasticity as Promising Clinical Tools for Stroke Recovery Evaluation

Several key issues impact the clinical practice of stroke rehabilitation including a patient’s medical history, stroke experience, the potential for recovery, and the selection of the most effective type of therapy. Until clinicians have answers to these concerns, the treatment and rehabilitation are rather intuitive, with standard procedures carried out based on subjective estimations using clinical scales. Therefore, there is a need to find biomarkers that could predict brain recovery potential in stroke patients. This review aims to present the current state-of-the-art stroke recovery biomarkers that could be used in clinical practice. The revision of biochemical biomarkers has been developed based on stroke recovery processes: angiogenesis and neuroplasticity. This paper provides an overview of the biomarkers that are considered to be ready-to-use in clinical practice and others, considered as future tools. Furthermore, this review shows the utility of biomarkers in the development of the concept of personalized medicine. Enhancing brain neuroplasticity and rehabilitation facilitation are crucial concerns not only after stroke, but in all central nervous system diseases.

An Exercise Mimetic Approach to Reduce Poststroke Deconditioning and Enhance Stroke Recovery

Evidence supports early rehabilitation after stroke to limit disability. However, stroke survivors are typically sedentary and experience significant cardiovascular and muscular deconditioning. Despite growing consensus that preclinical and clinical stroke recovery research should be aligned, there have been few attempts to incorporate cardiovascular and skeletal muscle deconditioning into animal models of stroke. Here, we demonstrate in rats that a hindlimb sensorimotor cortex stroke results in both cardiovascular and skeletal muscle deconditioning and impairments in gait akin to those observed in humans. To reduce poststroke behavioral, cardiovascular, and skeletal muscle perturbations, we then used a combinatorial intervention consisting of aerobic and resistance exercise in conjunction with administration of resveratrol (RESV), a drug with exercise mimetic properties. A combination of aerobic and resistance exercise mitigated decreases in cardiovascular fitness and attenuated skeletal muscle abnormalities. RESV, beginning 24 hours poststroke, reduced acute hindlimb impairments, improved recovery in hindlimb function, increased vascular density in the perilesional cortex, and attenuated skeletal muscle fiber changes. Early RESV treatment and aerobic and resistance exercise independently provided poststroke benefits, at a time when individuals are rapidly becoming deconditioned as a result of inactivity. Although no additive effects were observed in these experiments, this approach represents a promising strategy to reduce poststroke behavioral impairments and minimize deconditioning. As such, this treatment regime has potential for enabling patients to engage in more intensive rehabilitation at an earlier time following stroke when mechanisms of neuroplasticity are most prevalent.

Aerobic exercise attenuates neurodegeneration and promotes functional recovery - Why it matters for neurorehabilitation & neural repair

Aerobic exercise facilitates optimal neurological function and exerts beneficial effects in neurologic injuries. Both animal and clinical studies have shown that aerobic exercise reduces brain lesion volume and improves multiple aspects of cognition and motor function after stroke. Studies using animal models have proposed a wide range of potential molecular mechanisms that underlie the neurological benefits of aerobic exercise. Furthermore, additional exercise parameters, including time of initiation, exercise dosage (exercise duration and intensity), and treatment modality are also critical for clinical application, as identifying the optimal combination of parameters will afford patients with maximal functional gains. To clarify these issues, the current review summarizes the known neurological benefits of aerobic exercise under both physiological and pathological conditions and then considers the molecular mechanisms underlying these benefits in the contexts of stroke-like focal cerebral ischemia and cardiac arrest-induced global cerebral ischemia. In addition, we explore the key roles of exercise parameters on the extent of aerobic exercise-induced neurological benefits to elucidate the optimal combination for aerobic exercise intervention. Finally, the current challenges for aerobic exercise implementation after stroke are discussed.

Low-Intensity Exercise Suppresses CCAAT/Enhancer-Binding Protein δ/Myostatin Pathway Through Androgen Receptor in Muscle Cells

BACKGROUND

Androgen production following exercise has been suggested to contribute anabolic actions of muscle. However, the underlying mechanisms of the androgen receptor (AR) in androgen's action are still unclear.

OBJECTIVE

In the present study, we examined androgen/AR-mediated action in exercise, especially for the suppression of myostatin, a potent negative regulator of muscle mass.

METHODS

To examine the effects of exercise, we employed low-intensity exercise in mice and electric pulse stimulation (EPS) in C2C12 myotubes. Androgen production by C2C12 myotubes was measured by enzyme-linked immunosorbent assay. To block the action of AR, we pretreated C2C12 myotubes with flutamide. Quantitative real-time polymerase chain reaction was used to determine the expression levels of proteolytic genes including CCAAT/enhancer-binding protein delta (C/EBPδ), myostatin and muscle E3 ubiquitin ligases, as well as myogenic genes such as myogenin and PGC1α. The activation of 5'-adenosine-activated protein kinase and STAT3 was determined by Western blot analysis.

RESULTS

Both mRNA and protein levels of AR significantly increased in skeletal muscle of low-intensity exercised mice and C2C12 myotubes exposed to EPS. Production of testosterone and dihydrotestosterone from EPS-treated C2C12 myotubes was markedly increased. Of interest, we found that myostatin was clearly inhibited by EPS, and its inhibition was significantly abrogated when AR was blocked by flutamide. To test how AR suppresses myostatin, we examined the effects of EPS on C/EBPδ because the promoter region of myostatin has several C/EBP recognition sites. C/EBPδ expression was decreased by EPS, and this decrease was negated by flutamide. IL-6 and phospho-STAT3 (pSTAT3) expression, the downstream pathway of myostatin, were decreased by EPS and this was also reversed by flutamide. Similar downregulation of C/EBPδ, myostatin, and IL-6 was seen in skeletal muscle of low-intensity exercised mice.

CONCLUSIONS

Muscle AR expression and androgen production were increased by exercise and EPS treatment. As a mechanistical insight, it is suggested that AR inhibited myostatin expression transcriptionally by C/EBPδ suppression, which negatively influences IL-6/pSTAT3 expression and consequently contributes to the prevention of muscle proteolysis during exercise.

Bone Marrow Stromal Cells With Exercise and Thyroid Hormone Effect on Post-Stroke Injuries in Middle-aged Mice

Introduction:

Based on our previous findings, the treatment of stem cells alone or in combination with thyroid hormone (T₃) and mild exercise could effectively reduce the risk of stroke damage in young mice. However, it is unclear whether this treatment is effective in aged or middle-aged mice. Therefore, this study designed to assess whether combination of Bone Marrow Stromal Cells (BMSCs) with T₃ and mild treadmill exercise can decrease stroke complications in middle-aged mice.

Methods:

Under laser Doppler flowmetry monitoring, transient focal cerebral ischemia was produced by right Middle Cerebral Artery Occlusion (MCAO) for 45 min followed by 7 days of reperfusion in middle-aged mice. BMSCs (1×10⁵) were injected into the right cerebral ventricle 24 h after MCAO, followed by daily injection of triiodothyronine (T₃) (20 μg/100 g/d SC) and 6 days of running on a treadmill. Infarct size, neurological function, apoptotic cells and expression levels of Glial Fibrillary Acidic Protein (GFAP) were evaluated 1 week after stroke.

Results:

Post-ischemic treatment with BMSCs or with T₃ and or mild treadmill exercise alone or in combination did not significantly change neurological function, infarct size, and apoptotic cells 7 days after ischemia in middle-aged mice (P>0.05). However, the expression of GFAP significantly reduced after treatment with BMSCs and or T₃ (P<0.01).

Conclusion:

Our findings indicate that post-stroke treatment BMSCs with exercise and thyroid hormone cannot reverse neuronal damage 7 days after ischemia in middle-aged mice. These findings further support that age is an important variable in stroke treatment

Vasculature Remodeling in a Rat Model of Cerebral Ischemia. The Fate of the BrdU-Labeled Cells Prior to Stroke

Despite the clinical significance of post-stroke angiogenesis, a detailed phenotypic analysis of pre-stroke vascular remodeling and post-stroke angiogenesis had not yet been done in a model of focal ischemia. In this study, using BrdU-labeling of proliferating cells and immunofluorescence of pre- and post-stroke rats, we found that, (i) BrdU administered before stroke was incorporated preferentially into the nuclei of endothelial cells lining the lumen of existing blood vessels and newly born neurons in the dentate gyrus but not in the subventricular zone or proliferating microglia, (ii) BrdU injection prior to stroke led to the patchy distribution of the newly incorporated endothelial cells into existing blood vessels of the adult rat brain, (iii) BrdU injection prior to stroke specifically labeled neuronal precursors cells in a region of soft tissue beyond the inhibitory scar, which seems to be permissive to regenerative events, (iv) BrdU injection after stroke led to labeling of endothelial cells crossing or detaching from the disintegrating blood vessels and their incorporation into new blood vessels in the stroke region, scar tissue and the region beyond, (v) BrdU injection after stroke led to specific incorporation of BrdU-positive nuclei into the "pinwheel" architecture of the ventricular epithelium, (vi) blood vessels in remote areas relative to the infarct core and in the contralateral non-lesioned cortex, showed co-labeled BrdU/RECA⁺ endothelial cells shortly after the BrdU injection, which strongly suggests a bone marrow origin of the endothelial cells. In the damaged cortex, a BrdU/prolyl 4-hydroxylase beta double labeling in the close proximity to collagen IV-labeled basement membrane, suggests that, in addition to bone marrow derived endothelial cells, the disintegrating vascular wall itself could also be a source of proliferating endothelial cells, (vii) By day 28 after stroke, new blood vessels were observed in the perilesional area and the scar tissue region, which is generally considered to be resistant to regenerative events. Finally, (viii) vigorous angiogenesis was also detected in a region of soft tissue, also called "islet of regeneration," located next to the inhibitory scar. Conclusion: BrdU administered prior to, and after stroke, allows to investigate brain vasculature remodeling in the adult brain.

Is Environmental Enrichment Ready for Clinical Application in Human Post-stroke Rehabilitation?

Environmental enrichment (EE) has been widely used as a means to enhance brain plasticity mechanisms (e.g., increased dendritic branching, synaptogenesis, etc.) and improve behavioral function in both normal and brain-damaged animals. In spite of the demonstrated efficacy of EE for enhancing brain plasticity, it has largely remained a laboratory phenomenon with little translation to the clinical setting. Impediments to the implementation of enrichment as an intervention for human stroke rehabilitation and a lack of clinical translation can be attributed to a number of factors not limited to: (i) concerns that EE is actually the "normal state" for animals, whereas standard housing is a form of impoverishment; (ii) difficulty in standardizing EE conditions across clinical sites; (iii) the exact mechanisms underlying the beneficial actions of enrichment are largely correlative in nature; (iv) a lack of knowledge concerning what aspects of enrichment (e.g., exercise, socialization, cognitive stimulation) represent the critical or active ingredients for enhancing brain plasticity; and (v) the required "dose" of enrichment is unknown, since most laboratory studies employ continuous periods of enrichment, a condition that most clinicians view as impractical. In this review article, we summarize preclinical stroke recovery studies that have successfully utilized EE to promote functional recovery and highlight the potential underlying mechanisms. Subsequently, we discuss how EE is being applied in a clinical setting and address differences in preclinical and clinical EE work to date. It is argued that the best way forward is through the careful alignment of preclinical and clinical rehabilitation research. A combination of both approaches will allow research to fully address gaps in knowledge and facilitate the implementation of EE to the clinical setting.

Effects of the combined treatment of bone marrow stromal cells with mild exercise and thyroid hormone on brain damage and apoptosis in a mouse focal cerebral ischemia model

This study examined whether post-stroke bone marrow stromal cells (BMSCs) therapy combined with exercise (EX) and/or thyroid hormone (TH) could reduce brain damage in an experimental ischemic stroke in mice. Focal cerebral ischemia was induced under Laser Doppler Flowmetry (LDF) guide by 45 min of middle cerebral artery occlusion (MCAO), followed by 7 days of reperfusion in albino mice. BMSCs were injected into the right cerebral ventricle 24 h after MCAO, followed by daily injection of T3 (20 μg/100 g weight S.C) and 6 days of running on a treadmill. Infarct size, neurobehavioral test, TUNEL and BrdU positive cells were evaluated at 7 days after MCAO. Treatment with BMSCs and mild EX alone significantly reduced the infarct volume by 23% and 44%, respectively (both, p < 0.001). The BMSCs + TH, BMSCs + EX, and BMSCs + EX + TH combination therapies significantly reduced the infarct volume by 26%, 51%, and 70%, respectively (all, p < 0.001). A significant improvement in the neurobehavioral functioning was observed in the EX, BMSCs + EX, and BMSCs + EX+ TH groups (p < 0.001). The number of TUNEL-positive cells (a marker of apoptosis) was significantly reduced in the EX, BMSCs, BMSCs + EX, BMSCs + TH, and BMSCs + EX + TH groups (all, p < 0.001). Moreover, the combination therapy considerably increased BrdU-labeled cells in the subventricular zone (SVZ) (p < 0.01). Our findings indicated that the combined treatment of BMSCs with mild EX and TH more efficiently reduces the cerebral infarct size after stroke. More likely, these effects mediate via enchaining generation of new neuronal cells and the attenuation of apoptosis in ischemia stroke in young mice.

Exercise and Environmental Enrichment as Enablers of Task-Specific Neuroplasticity and Stroke Recovery

Improved stroke care has resulted in greater survival, but >50% of patients have chronic disabilities and 33% are institutionalized. While stroke rehabilitation is helpful, recovery is limited and the most significant gains occur in the first 2-3 months. Stroke triggers an early wave of gene and protein changes, many of which are potentially beneficial for recovery. It is likely that these molecular changes are what subserve spontaneous recovery. Two interventions, aerobic exercise and environmental enrichment, have pleiotropic actions that influence many of the same molecular changes associated with stroke injury and subsequent spontaneous recovery. Enrichment paradigms have been used for decades in adult and neonatal animal models of brain injury and are now being adapted for use in the clinic. Aerobic exercise enhances motor recovery and helps reduce depression after stroke. While exercise attenuates many of the signs associated with normal aging (e.g., hippocampal atrophy), its ability to reverse cognitive impairments subsequent to stroke is less evident. It may be that stroke, like other diseases such as cancer, needs to use multimodal treatments that augment complimentary neurorestorative processes.

The role of vascular endothelial growth factor in the regulation of development and functioning of the brain: new target molecules for pharmacotherapy

Vascular endothelial growth factors (VEGFs) have been shown to participate in atherosclerosis, arteriogenesis, cerebral edema, neuroprotection, neurogenesis, angiogenesis, postischemic brain and vessel repair. Most of these actions involve VEGF-A and the VEGFR-2 receptor. VEGF signaling pathways represent an important potential for treatment of neurological diseases affecting the brain

Physical exercise-induced protection on ischemic cardiovascular and cerebrovascular diseases

Physical exercise is any bodily activity to enhance or maintain physical fitness and overall health and wellness. A series of associated studies have demonstrated that physical exercise could alleviate the infarct volume, increase the collateral circulation, promote endothelial progenitor cells, improve cerebral blood flow after cardiovascular and cerebrovascular diseases. In this review, we summed up the protective effects of physical exercise on cerebral blood flow (CBF), vascular endothelium, vascular vasodilation, endothelial progenitor cells and collateral circulation. An awareness of the exercise intervention benefits for cardiovascular and cerebrovascular diseases may encourage more patients with cerebral infarction and myocardial infarction and people with high risk factors to accept exercise interventions for the prevention and treatment of cardiovascular and cerebrovascular diseases.

The Effects of Exercise on Cognitive Recovery after Acquired Brain Injury in Animal Models: A Systematic Review

The objective of the present paper is to review the current status of exercise as a tool to promote cognitive rehabilitation after acquired brain injury (ABI) in animal model-based research. Searches were conducted on the PubMed, Scopus, and psycINFO databases in February 2014. Search strings used were: exercise (and) animal model (or) rodent (or) rat (and) traumatic brain injury (or) cerebral ischemia (or) brain irradiation. Studies were selected if they were (1) in English, (2) used adult animals subjected to acquired brain injury, (3) used exercise as an intervention tool after inflicted injury, (4) used exercise paradigms demanding movement of all extremities, (5) had exercise intervention effects that could be distinguished from other potential intervention effects, and (6) contained at least one measure of cognitive and/or emotional function. Out of 2308 hits, 22 publications fulfilled the criteria. The studies were examined relative to cognitive effects associated with three themes: exercise type (forced or voluntary), timing of exercise (early or late), and dose-related factors (intensity, duration, etc.). The studies indicate that exercise in many cases can promote cognitive recovery after brain injury. However, the optimal parameters to ensure cognitive rehabilitation efficacy still elude us, due to considerable methodological variations between studies.

Functional level during the first 2 years after moderate and severe traumatic brain injury

BACKGROUND

Long-term outcomes after TBI are examined to a large extent, but longitudinal studies with more than 1-year follow-up time after injury have been fewer in number. The course of recovery may vary due to a number of factors and it is still somewhat unclear which factors are contributing.

AIM

The aim of this study was to describe the functional level at four time points up to 24 months after traumatic brain injury (TBI) and to evaluate the predictive impact of pre-injury and injury-related factors.

DESIGN

A cohort study.

SETTING

Outpatient.

POPULATION

Sixty-five patients with moderate (n = 21) or severe (n = 44) TBI.

METHODS

The patients with TBI were examined with Functional Independence Measure (FIM) and Glasgow Outcome Scale Extended (GOSE) at 3 months, 12 months and 24 months after injury. Possible predictors were analysed in a regression model using FIM total score at 24 months as the outcome measure.

RESULTS

FIM scores improved significantly from rehabilitation unit discharge to 24 months after injury, with peak levels at 3 and 24 months after injury (p < 0.001), for the whole TBI group and the group with severe TBI. The moderate TBI group did not show significant FIM score improvement during this time period. GOSE scores for the whole group and the moderate group improved significantly over time, but the severe group did not. FIM at admission to the rehabilitation unit and GCS score at admission to the rehabilitation unit were closest to being significant predictors of FIM total scores 24 months after injury (B = 0.265 and 2.883, R(2 )= 0.39, p = 0.073, p = 0.081).

CONCLUSION

FIM levels improved during the period from rehabilitation unit discharge to 3 months follow-up; thereafter, there was a 'plateauing' of recovery. In contrast, GOSE 'plateauing' of recovery was at 12 months.

CLINICAL REHABILITATION IMPACT

The study results may indicate that two of the most used outcome measures in TBI research are more relevant for assessment of the functional recovery in a sub-acute phase than in later stages of TBI recovery.

Exercise preconditioning improves traumatic brain injury outcomes

PURPOSE

To determine whether 6 weeks of exercise performed prior to traumatic brain injury (TBI) could improve post-TBI behavioral outcomes in mice, and if exercise increases neuroprotective molecules (vascular endothelial growth factor-A [VEGF-A], erythropoietin [EPO], and heme oxygenase-1 [HO-1]) in brain regions responsible for movement (sensorimotor cortex) and memory (hippocampus).

METHODS

120 mice were randomly assigned to one of four groups: (1) no exercise+no TBI (NOEX-NOTBI [n=30]), (2) no exercise+TBI (NOEX-TBI [n=30]), (3) exercise+no TBI (EX-NOTBI [n=30]), and (4) exercise+TBI (EX-TBI [n=30]). The gridwalk task and radial arm water maze were used to evaluate sensorimotor and cognitive function, respectively. Quantitative real time polymerase chain reaction and immunostaining were performed to investigate VEGF-A, EPO, and HO-1 mRNA and protein expression in the right cerebral cortex and ipsilateral hippocampus.

RESULTS

EX-TBI mice displayed reduced post-TBI sensorimotor and cognitive deficits when compared to NOEX-TBI mice. EX-NOTBI and EX-TBI mice showed elevated VEGF-A and EPO mRNA in the cortex and hippocampus, and increased VEGF-A and EPO staining of sensorimotor cortex neurons 1 day post-TBI and/or post-exercise. EX-TBI mice also exhibited increased VEGF-A staining of hippocampal neurons 1 day post-TBI/post-exercise. NOEX-TBI mice demonstrated increased HO-1 mRNA in the cortex (3 days post-TBI) and hippocampus (3 and 7 days post-TBI), but HO-1 was not increased in mice that exercised.

CONCLUSIONS

Improved TBI outcomes following exercise preconditioning are associated with increased expression of specific neuroprotective genes and proteins (VEGF-A and EPO, but not HO-1) in the brain.

Neuroprotection of Early Locomotor Exercise Poststroke: Evidence From Animal Studies

Early locomotor exercise after stroke has attracted a great deal of attention in clinical and animal research in recent years. A series of animal studies showed that early locomotor exercise poststroke could protect against ischemic brain injury and improve functional outcomes through the promotion of angiogenesis, inhibition of acute inflammatory response and neuron apoptosis, and protection of the blood-brain barrier. However, to date, the clinical application of early locomotor exercise poststroke was limited because some clinicians have little confidence in its effectiveness. Here we review the current progress of early locomotor exercise poststroke in animal models. We hope that a comprehensive awareness of the early locomotor exercise poststroke may help to implement early locomotor exercise more appropriately in treatment for ischemic stroke.

Aerobic exercise effects on neuroprotection and brain repair following stroke: a systematic review and perspective

Aerobic exercise (AE) enhances neuroplasticity and improves functional outcome in animal models of stroke, however the optimal parameters (days post-stroke, intensity, mode, and duration) to influence brain repair processes are not known. We searched PubMed, CINAHL, PsychInfo, the Cochrane Library, and the Central Register of Controlled Clinical Trials, using predefined criteria, including all years up to July 2013 (English language only). Clinical studies were included if participants had experienced an ischemic or hemorrhagic stroke. We included animal studies that utilized any method of global or focal ischemic stroke or intracerebral hemorrhage. Any intervention utilizing AE-based activity with the intention of improving cardiorespiratory fitness was included. Of the 4250 titles returned, 47 studies (all in animal models) met criteria and measured the effects of exercise on brain repair parameters (lesion volume, oxidative damage, inflammation and cell death, neurogenesis, angiogenesis and markers of stress). Our synthesized findings show that early-initiated (24-48h post-stroke) moderate forced exercise (10m/min, 5-7 days per week for about 30min) reduced lesion volume and protected perilesional tissue against oxidative damage and inflammation at least for the short term (4 weeks). The applicability and translation of experimental exercise paradigms to clinical trials are discussed.

Role of vascular endothelial growth factor and other growth factors in post-stroke recovery

Stroke is a major health problem world-wide and its burden has been rising in last few decades. Until now tissue plasminogen activator is only approved treatment for stroke. Angiogenesis plays a vital role for striatal neurogenesis after stroke. Administration of various growth factors in an early post ischemic phase, stimulate both angiogenesis and neurogenesis and lead to improved functional recovery after stroke. However vascular endothelial growth factors (VEGF) is the most potent angiogenic factor for neurovascularization and neurogenesis in ischemic injury can be modulated in different ways and thus can be used as therapy in stroke. In response to the ischemic injury VEGF is released by endothelial cells through natural mechanism and leads to angiogenesis and vascularization. This release can also be up regulated by exogenous administration of Mesenchymal stem cells, by various physical therapy regimes and electroacupuncture, which further potentiate the efficacy of VEGF as therapy in post stroke recovery. Recent published literature was searched using PubMed and Google for the article reporting on methods of up regulation of VEGF and therapeutic potential of growth factors in stroke.

Impact of BDNF -196 G>A and BDNF -270 C>T polymorphisms on stroke rehabilitation outcome: sex and age differences

BACKGROUND

Genetic factors, including gene polymorphisms, are promising in determining stroke rehabilitation outcome. Brain-derived neurotrophic factor (BDNF) is one of the most attractive because of its role in neuroplasticity and brain repair.

OBJECTIVE

The aim of present study was to assess the role of BDNF -196 G≯A (val66met) and -270 C≯T on clinical parameters and functional outcome in patients with ischemic and hemorrhagic stroke. Additional analyses according to sex and age (≤55 and ≯55 years) were performed.

METHODS

Three hundred thirty-eight patients (287 with ischemic and 51 with hemorrhagic stroke) were evaluated in terms of neurological deficit (National Institute of Heath Stroke Scale [NIHSS]), activities of daily living (Barthel Index [BI]), and everyday functionality (Rankin score [RS]) before and after rehabilitation. BDNF polymorphism genotyping was performed by polymerase chain reaction restriction fragment length polymorphism analysis.

RESULTS

In multivariative analysis, unfavorable outcome of stroke rehabilitation (RS ≥2) was associated with independent factors: ischemic stroke (odds ratio [OR], 2.59; 95% CI, 1.03-6.47), female gender (OR, 2.80; 95% CI, 1.39-5.64), depression (OR, 4.24; 95% CI, 1.45-12.35), falls (OR, 2.61; 95% CI, 1.16-5.87), and BDNF -196 GG polymorphism (OR, 2.18; 95% CI, 1.09-4.35). The differences of functional parameters measured with BI and RS on admission and at discharge are apparent only for comparisons between patients ≤55 and ≯55 years old carrying BDNF -196 GA+AA genotypes but not in those carrying -196 GG genotype; the differences were evident in women but not in men.

CONCLUSIONS

BDNF -196 G≯A polymorphism might affect functional outcome of stroke rehabilitation, but this hypothesis needs further verification.

Physical exercise training and neurovascular unit in ischemic stroke

Physical exercise could exert a neuroprotective effect in both clinical studies and animal experiments. A series of related studies have indicated that physical exercise could reduce infarct volume, alleviate neurological deficits, decrease blood-brain barrier dysfunction, promote angiogenesis in cerebral vascular system and increase the survival rate after ischemic stroke. In this review, we summarized the protective effects of physical exercise on neurovascular unit (NVU), including neurons, astrocytes, pericytes and the extracellular matrix. Furthermore, it was demonstrated that exercise training could decrease the blood-brain barrier dysfunction and promote angiogenesis in cerebral vascular system. An awareness of the exercise intervention benefits pre- and post stroke may lead more stroke patients and people with high-risk factors to accept exercise therapy for the prevention and treatment of stroke.