Themes and strategies for studying the biology of stroke recovery in the poststroke epoch

Targeting Neuronal GPR65 With Delayed BTB09089 Treatment Improves Neurorehabilitation Following Ischemic Stroke

BACKGROUND

GPR65 (G protein-coupled receptor 65) can sense extracellular acidic environment to regulate pathophysiological processes. Pretreatment with the GPR65 agonist BTB09089 has been proven to produce neuroprotection in acute ischemic stroke. However, whether delayed BTB09089 treatment and neuronal GPR65 activation promote neurorestoration remains unknown.

METHODS

Ischemic stroke was induced in wild-type (WT) or GPR65 knockout (GPR65-/-) mice by photothrombotic ischemia. Male mice were injected intraperitoneally with BTB09089 every other day at days 3, 7, or 14 poststroke. AAV-Syn-GPR65 (adenoassociated virus-synapsin-GPR65) was utilized to overexpress GPR65 in the peri-infarct cortical neurons of GPR65-/- and WT mice. Motor function was monitored by grid-walk and cylinder tests. The neurorestorative effects of BTB09089 were observed by immunohistochemistry, Golgi-Cox staining, and Western blotting.

RESULTS

BTB09089 significantly promoted motor outcomes in WT but not in GPR65-/- mice, even when BTB09089 was delayed for 3 to 7 days. BTB09089 inhibited the activation of microglia and glial scar progression in WT but not in GPR65-/- mice. Meanwhile, BTB09089 reduced the decrease in neuronal density in WT mice, but this benefit was abolished in GPR65-/- mice and reemerged by overexpressing GPR65 in peri-infarct cortical neurons. Furthermore, BTB09089 increased the GAP43 (growth-associated protein-43) and synaptophysin puncta density, dendritic spine density, dendritic branch length, and dendritic complexity by overexpressing GPR65 in the peri-infarct cortical neurons of GPR65-/- mice, which was accompanied by increased levels of p-CREB (phosphorylated cAMP-responsive element-binding protein). In addition, the therapeutic window of BTB09089 was extended to day 14 by overexpressing GPR65 in the peri-infarct cortical neurons of WT mice.

CONCLUSIONS

Our findings indicated that delayed BTB09089 treatment improved neurological functional recovery and brain tissue repair poststroke through activating neuronal GRP65. GPR65 overexpression may be a potential strategy to expand the therapeutic time window of GPR65 agonists for neurorehabilitation after ischemic stroke.

Neuroimaging of motor recovery after ischemic stroke - functional reorganization of motor network

The long-term motor outcome of acute stroke patients may be correlated to the reorganization of brain motor network. Abundant neuroimaging studies contribute to understand the pathological changes and recovery of motor networks after stroke. In this review, we summarized how current neuroimaging studies have increased understanding of reorganization and plasticity in post stroke motor recovery. Firstly, we discussed the changes in the motor network over time during the motor-activation and resting states, as well as the overall functional integration trend of the motor network. These studies indicate that the motor network undergoes dynamic bilateral hemispheric functional reorganization, as well as a trend towards network randomization. In the second part, we summarized the current study progress in the application of neuroimaging technology to early predict the post-stroke motor outcome. In the third part, we discuss the neuroimaging techniques commonly used in the post-stroke recovery. These methods provide direct or indirect visualization patterns to understand the neural mechanisms of post-stroke motor recovery, opening up new avenues for studying spontaneous and treatment-induced recovery and plasticity after stroke.

Micro-ultrasound based characterization of cerebrovasculature following focal ischemic stroke and upon short-term rehabilitation

Notwithstanding recanalization treatments in the acute stage of stroke, many survivors suffer long-term impairments. Physical rehabilitation is the only widely available strategy for chronic-stage recovery, but its optimization is hindered by limited understanding of its effects on brain structure and function. Using micro-ultrasound, behavioral testing, and electrophysiology, we investigated the impact of skilled reaching rehabilitation on cerebral hemodynamics, motor function, and neuronal activity in a rat model of focal ischemic stroke. A 50 MHz micro-ultrasound transducer and intracortical electrophysiology were utilized to characterize neurovascular changes three weeks following focal ischemia elicited by endothelin-1 injection into the sensorimotor cortex. Sprague-Dawley rats were rehabilitated through tray reaching, and their fine skilled reaching was assessed via the Montoya staircase. Focal ischemia led to a sustained deficit in forelimb reaching; and increased tortuosity of the penetrating vessels in the perilesional cortex; with no lateralization of spontaneous neuronal activity. Rehabilitation improved skilled reaching; decreased cortical vascularity; was associated with elevated peri- vs. contralesional hypercapnia-induced flow homogenization and increased perilesional spontaneous cortical neuronal activity. Our study demonstrated neurovascular plasticity accompanying rehabilitation-elicited functional recovery in the subacute stage following stroke, and multiple micro-ultrasound-based markers of cerebrovascular structure and function modified in recovery from ischemia and upon rehabilitation.

Angiogenesis after ischemic stroke

Owing to its high disability and mortality rates, stroke has been the second leading cause of death worldwide. Since the pathological mechanisms of stroke are not fully understood, there are few clinical treatment strategies available with an exception of tissue plasminogen activator (tPA), the only FDA-approved drug for the treatment of ischemic stroke. Angiogenesis is an important protective mechanism that promotes neural regeneration and functional recovery during the pathophysiological process of stroke. Thus, inducing angiogenesis in the peri-infarct area could effectively improve hemodynamics, and promote vascular remodeling and recovery of neurovascular function after ischemic stroke. In this review, we summarize the cellular and molecular mechanisms affecting angiogenesis after cerebral ischemia registered in PubMed, and provide pro-angiogenic strategies for exploring the treatment of ischemic stroke, including endothelial progenitor cells, mesenchymal stem cells, growth factors, cytokines, non-coding RNAs, etc.

Multicomponent Educational-Rehabilitation Approach in Rehabilitation of Patients After Stroke

Rehabilitation must be based on the individual needs and specific goals of the person and must be adapted to his abilities. According to the recommendation of the World Stroke Organization, the team involved in conducting rehabilitation should be multidisciplinary. One of the treatments that are applied within the multidisciplinary approach to a neurological patient is educational-rehabilitation treatment, which is multicomponent in nature. Before starting educational-rehabilitation treatment, an educational-rehabilitation clinical assessment is necessary, which aims to detect difficulties caused by impairment; identify potentials and constraints in these areas; determine the specifics, course, and forecasts of difficulties; formulate clear treatment recommendations; form a watch list that will be available to all team members in the process of diagnosis, treatment, education, and to evaluate the effectiveness of treatment; and continuously monitor the ability and adaptive behavior of the person. Educational-rehabilitation clinical treatment includes treatment of cognitive abilities, treatment of motor skills, relaxation, treatment of adaptive skills, as well as informing the person about the disease and counseling. This review focuses on some aspects of rehabilitation such as treatment of cognitive and motor disorders, treatment of adaptive skills, relaxation issues, and informing and counseling patients from the perspective of an educational rehabilitator with practical experiences in this area of rehabilitation.

Gene Expression Profile Changes in the Stimulated Rat Brain Cortex After Repetitive Transcranial Magnetic Stimulation

Repetitive transcranial magnetic stimulation (rTMS) is gaining popularity as a research tool in neuroscience; however, little is known about its molecular mechanisms of action. The present study aimed to investigate the rTMS-induced transcriptomic changes; we performed microarray messenger RNA, micro RNA, and integrated analyses to explore these molecular events. Eight adult male Sprague-Dawley rats were subjected to a single session of unilateral rTMS at 1 Hz (n = 4) or sham (n = 4). The left hemisphere was stimulated for 20 minutes. To evaluate the cumulative effect of rTMS, eight additional rats were assigned to the 1-Hz (n = 4) or sham (n = 4) rTMS groups. The left hemisphere was stimulated for 5 consecutive days using the same protocol. Microarray analysis revealed differentially expressed genes in the rat cortex after rTMS treatment. The overrepresented gene ontology categories included the positive regulation of axon extension, axonogenesis, intracellular transport, and synaptic plasticity after repeated sessions of rTMS. A single session of rTMS primarily induced changes in the early genes, and several miRNAs were significantly related to the mRNAs. Future studies are required to validate the functional significance of selected genes and refine the therapeutic use of rTMS.

Inhibition of CSPG receptor PTPσ promotes migration of newly born neuroblasts, axonal sprouting, and recovery from stroke

In addition to neuroprotective strategies, neuroregenerative processes could provide targets for stroke recovery. However, the upregulation of inhibitory chondroitin sulfate proteoglycans (CSPGs) impedes innate regenerative efforts. Here, we examine the regulatory role of PTPσ (a major proteoglycan receptor) in dampening post-stroke recovery. Use of a receptor modulatory peptide (ISP) or Ptprs gene deletion leads to increased neurite outgrowth and enhanced NSCs migration upon inhibitory CSPG substrates. Post-stroke ISP treatment results in increased axonal sprouting as well as neuroblast migration deeply into the lesion scar with a transcriptional signature reflective of repair. Lastly, peptide treatment post-stroke (initiated acutely or more chronically at 7 days) results in improved behavioral recovery in both motor and cognitive functions. Therefore, we propose that CSPGs induced by stroke play a predominant role in the regulation of neural repair and that blocking CSPG signaling pathways will lead to enhanced neurorepair and functional recovery in stroke.

Somatosensory Deficits After Stroke: Insights From MRI Studies

Somatosensory deficits after stroke are a major health problem, which can impair patients' health status and quality of life. With the developments in human brain mapping techniques, particularly magnetic resonance imaging (MRI), many studies have applied those techniques to unravel neural substrates linked to apoplexy sequelae. Multi-parametric MRI is a vital method for the measurement of stroke and has been applied to diagnose stroke severity, predict outcome and visualize changes in activation patterns during stroke recovery. However, relatively little is known about the somatosensory deficits after stroke and their recovery. This review aims to highlight the utility and importance of MRI techniques in the field of somatosensory deficits and synthesizes corresponding articles to elucidate the mechanisms underlying the occurrence and recovery of somatosensory symptoms. Here, we start by reviewing the anatomic and functional features of the somatosensory system. And then, we provide a discussion of MRI techniques and analysis methods. Meanwhile, we present the application of those techniques and methods in clinical studies, focusing on recent research advances and the potential for clinical translation. Finally, we identify some limitations and open questions of current imaging studies that need to be addressed in future research.

Temporal profile of angiogenesis and expression of extracellular matrix-related genes in rat brains following experimental intracerebral hemorrhage

BACKGROUND

Angiogenesis is essential for the repair process after intracerebral hemorrhage (ICH).

METHODS

Given the importance of the extracellular matrix (ECM) in angiogenesis, we analysed the temporal profile of angiogenesis in rat brains on days 4, 7, and 21 after ICH. To this end, we compared the expression of ECM-related genes between ICH-induced and sham-operated groups using a complementary DNA (cDNA) array. We further measured protein expression using western blot and immunohistochemistry assays. Fluorescein isothiocyanate (FITC)-dextran was injected into the tail vein to examine the angioarchitecture in the perihematomal region.

RESULTS

Among the 88 ECM-related genes, we identified 42, 50, and 38 genes that were significantly upregulated on days 4, 7, and 21 after ICH, respectively (P < 0.05). Particularly, collagens, integrins, and matrix metalloproteinases (MMPs) were significantly increased on day 4 post-ICH and continued to increase at the other time points. Western blot and immunohistochemistry analyses showed a comparable trend in the upregulation of MMPs. Compared to the sham group, FITC-dextran labelling demonstrated decreased perfusion and increased vascular permeability in the perihematomal region in the ICH group. Doxycycline, an MMP inhibitor, significantly reduced angiogenesis (P < 0.05).

CONCLUSIONS

The results of this study indicate that MMPs are involved in modulating angiogenesis following ICH.

Dynamic Relationship Between Interhemispheric Functional Connectivity and Corticospinal Tract Changing Pattern After Subcortical Stroke

Background and Purpose

Increased interhemispheric resting-state functional connectivity (rsFC) between the bilateral primary motor cortex (M1) compensates for corticospinal tract (CST) impairment, which facilitates motor recovery in chronic subcortical stroke. However, there is a lack of data on the evolution patterns and correlations between M1–M1 rsFC and diffusion indices of CSTs with different origins after subcortical stroke and their relations with long-term motor outcomes.

Methods

A total of 44 patients with subcortical stroke underwent longitudinal structural and functional magnetic resonance imaging (MRI) examinations and clinical assessments at four time points. Diffusion tensor imaging was used to extract fractional anisotropy (FA) values of the affected CSTs with different origins. Resting-state functional MRI was used to calculate the M1–M1 rsFC. Longitudinal patterns of functional and anatomic changes in connections were explored using a linear mixed-effects model. Dynamic relationships between M1–M1 rsFC and FA values of the affected specific CSTs and the impact of these variations on the long-term motor outcomes were analyzed in patients with subcortical stroke.

Results

Stroke patients showed a significantly decreased FA in the affected specific CSTs and a gradually increasing M1–M1 rsFC from the acute to the chronic stage. The FA of the affected M1 fiber was negatively correlated with the M1–M1 rsFC from the subacute to the chronic stage, FA of the affected supplementary motor area fiber was negatively correlated with the M1–M1 rsFC in the subacute stage, and FA of the affected M1 fiber in the acute stage was correlated with the long-term motor recovery after subcortical stroke.

Conclusion

Our findings show that the FA of the affected M1 fiber in the acute stage had the most significant correlation with long-term motor recovery and may be used as an imaging biomarker for predicting motor outcomes after stroke. The compensatory role of the M1–M1 rsFC enhancement may start from the subacute stage in stroke patients with CST impairment.

Agonistic analog of growth hormone-releasing hormone promotes neurofunctional recovery and neural regeneration in ischemic stroke

Ischemic stroke can induce neurogenesis. However, most stroke-generated newborn neurons cannot survive. It has been shown that MR-409, a potent synthetic agonistic analog of growth hormone-releasing hormone (GHRH), can protect against some life-threatening pathological conditions by promoting cell proliferation and survival. The present study shows that long-term treatment with MR-409 (5 or 10 μg/mouse/d) by subcutaneous (s.c.) injection significantly reduces the mortality, ischemic insult, and hippocampal atrophy, and improves neurological functional recovery in mice operated on for transient middle cerebral artery occlusion (tMCAO). Besides, MR-409 can stimulate endogenous neurogenesis and improve the tMCAO-induced loss of neuroplasticity. MR-409 also enhances the proliferation and inhibits apoptosis of neural stem cells treated with oxygen and glucose deprivation-reperfusion. The neuroprotective effects of MR-409 are closely related to the activation of AKT/CREB and BDNF/TrkB pathways. In conclusion, the present study demonstrates that GHRH agonist MR-409 has remarkable neuroprotective effects through enhancing endogenous neurogenesis in cerebral ischemic mice.

Cuprizone-induced demyelination under physiological and post-stroke condition leads to decreased neurogenesis response in adult mouse brain

Due to the limitation in treatment window of the rtPA (recombinant tissue plasminogen activator), the development of delayed treatment for stroke is needed. We previously reported that there is a difference in neurogenesis and neuroblast migration patterns in different mouse stroke models (proximal and distal middle cerebral artery occlusion models, pMCAo or dMCAo). Specifically, compared to robust neurogenesis and substantial migration of newly born neuroblasts in pMCAo model, dMCAo only illicit limited neurogenesis and migration of neuroblasts towards ischemic area. One potential reason for this difference is the relative location of ischemic area to white matter and the neurogenic niche (subventricular zone, SVZ). Specifically, white matter could serve as a physical barrier or inhibitory factor to neurogenesis and migration in the dMCAo model. Given that a major difference in human and rodent brains is the content of white matter in the brain, in this study, we further characterize these two models and test the important hypothesis that white matter is an important contributing inhibitory factor for the limited neurogenesis in the dMCAo model. We utilized a genetically inducible NSC-specific reporter mouse line (nestin-CreERT2-R26R-YFP) to label and track NSC proliferation, survival and differentiation in ischemic brain. To test whether myelin is inhibitory to neurogenesis in dMCAo model, we demyelinated mouse brains using cuprizone treatment after stroke and examined whether there is enhanced neurogenesis or migration of neuroblasts cells in stroke mice treated with cuprizone. Our data suggests that demyelination of the brain does not result in enhanced neurogenesis or migration of neuroblasts, supporting that myelin is not a major inhibitory factor for stroke-induced neurogenesis. In addition, our results suggest that in non-stroke mice, demyelination causes decreased neurogenesis in adult brain, indicating a potential positive role of myelin in maintenance of adult neural stem cell niche.

Dissociating nNOS (Neuronal NO Synthase)-CAPON (Carboxy-Terminal Postsynaptic Density-95/Discs Large/Zona Occludens-1 Ligand of nNOS) Interaction Promotes Functional Recovery After Stroke via Enhanced Structural Neuroplasticity

Background and Purpose- Stroke is a major public health concern worldwide. Although clinical treatments have improved in the acute period after stroke, long-term therapeutics remain limited to physical rehabilitation in the delayed phase. This study is aimed to determine whether nNOS (neuronal NO synthase)-CAPON (carboxy-terminal postsynaptic density-95/discs large/zona occludens-1 ligand of nNOS) interaction may serve as a new therapeutic target in the delayed phase for stroke recovery. Methods- Photothrombotic stroke and transient middle cerebral artery occlusion were induced in mice. Adeno-associated virus (AAV)-cytomegalovirus (CMV)-CAPON-125C-GFP (green fluorescent protein)-3Flag and the other 2 drugs (Tat-CAPON-12C and ZLc-002) were microinjected into the peri-infarct cortex immediately and 4 to 10 days after photothrombotic stroke, respectively. ZLc-002 was also systemically injected 4 to 10 days after transient middle cerebral artery occlusion. Grid-walking task and cylinder task were conducted to assess motor function. Western blotting, immunohistochemistry, Golgi staining, and electrophysiology recordings were performed to uncover the mechanisms. Results- Stroke increased nNOS-CAPON association in the peri-infarct cortex in the delayed period. Inhibiting the ischemia-induced nNOS-CAPON association substantially decreased the number of foot faults in the grid-walking task and forelimb asymmetry in the cylinder task, suggesting the promotion of functional recovery from stroke. Moreover, dissociating nNOS-CAPON significantly facilitated dendritic remodeling and synaptic transmission, indicated by increased dendritic spine density, dendritic branching, and length and miniature excitatory postsynaptic current frequency but did not affect stroke-elicited neuronal loss, infarct size, or cerebral edema, suggesting that nNOS-CAPON interaction may function via regulating structural neuroplasticity, rather than neuroprotection. Furthermore, ZLc-002 reversed the transient middle cerebral artery occlusion-induced impairment of motor function. Conclusions- Our results reveal that nNOS-CAPON coupling can serve as a novel pharmacological target for functional restoration after stroke.

Effects of thalamic infarction on the structural and functional connectivity of the ipsilesional primary somatosensory cortex

OBJECTIVES

To identify regions causally influenced by thalamic stroke by measuring white matter integrity, cortical volume, and functional connectivity (FC) among patients with thalamic infarction (TI) and to determine the association between structural/functional alteration and somatosensory dysfunction.

METHODS

Thirty-one cases with TI-induced somatosensory dysfunction and 32 healthy controls underwent magnetic resonance imaging scanning. We reconstructed the ipsilesional central thalamic radiation (CTR) and assessed its integrity using fractional anisotropy (FA), assessed S1 ipsilesional changes with cortical volume, and identified brain regions functionally connected to TI locations and regions without TI to examine the potential effects on somatosensory symptoms.

RESULTS

Compared with controls, TI patients showed decreased FA (F = 17.626, p < 0.001) in the ipsilesional CTR. TI patients exhibited significantly decreased cortical volume in the ipsilesional top S1. Both affected CTR (r = 0.460, p = 0.012) and S1 volume (r = 0.375, p = 0.049) were positively correlated with somatosensory impairment in TI patients. In controls, the TI region was highly functionally connected to atrophic top S1 and less connected to the adjacent middle S1 region in FC mapping. However, T1 patients demonstrated significantly increased FC between the ipsilesional thalamus and middle S1 area, which was adjacent to the atrophic S1 region.

CONCLUSIONS

TI induces remote changes in the S1, and this network of abnormality underlies the cause of the sensory deficits. However, our other finding that there is stronger connectivity in pathways adjacent to the damaged ones is likely responsible for at least some of the recovery of function.

KEY POINTS

• TI led to secondary impairment in the CTR and cortical atrophy in the ipsilesional top of S1. • TI patients exhibited significantly higher functional connectivity with the ipsilateral middle S1 which was mainly located within the non-atrophic area of S1. • Our results provide neuroimaging markers for non-invasive treatment and predict somatosensory recovery.

Revascularization and endothelial progenitor cells in stroke

Stroke is one of the leading causes of death and disability worldwide. Tremendous improvements have been achieved in the acute care of stroke patients with the implementation of stroke units, thrombolytic drugs, and endovascular trombectomies. However, stroke survivors with neurological deficits require long periods of neurorehabilitation, which is the only approved therapy for poststroke recovery. With this scenario, more treatments are urgently needed, and only the understanding of the mechanisms of brain recovery might contribute to identify new therapeutic agents. Fortunately, brain injury after stroke is counteracted by the birth and migration of several populations of progenitor cells towards the injured areas, where angiogenesis and vascular remodeling play a key role providing trophic support and guidance during neurorepair. Endothelial progenitor cells (EPCs) constitute a pool of circulating bone-marrow derived cells that mobilize after an ischemic injury with the potential to incorporate into the damaged endothelium, to form new vessels, or to secrete trophic factors stimulating vessel remodeling. The circulating levels of EPCs are altered after stroke, and several subpopulations have proved to boost brain neurorepair in preclinical models of cerebral ischemia. The goal of this review is to discuss the current state of the neuroreparative actions of EPCs, focusing on their paracrine signaling mechanisms thorough their secretome and released extracellular vesicles.

Inhibiting Histone Deacetylase 2 (HDAC2) Promotes Functional Recovery From Stroke

BACKGROUND

Stroke is a leading cause of long-term disability worldwide. However, current therapies that promote functional recovery from stroke are limited to physical rehabilitation. No pharmacological therapy is available. Thus, understanding the role of histone deacetylase 2 (HDAC2) in the pathophysiological process of stroke-induced functional loss may provide a novel strategy for stroke recovery.

METHODS AND RESULTS

Focal stroke was induced by photothrombosis. LV-HDAC2-shRNA-GFP, LV-GFP, Ad-HDAC2-Flag, or Ad-inactive-HDAC2-Flag was microinjected into the peri-infarct area immediately after stroke. HDAC inhibitors were microinjected into the peri-infarct area 4 to 10 days after stroke. Grid-walking task and cylinder task were conducted to assess motor function. Golgi-Cox staining, chromatin immunoprecipitation, and electrophysiology were used to reveal the mechanisms underlying stroke recovery. Knockdown or knockout of HDAC2 promoted stroke recovery, whereas overexpression of HDAC2 worsened stroke-induced functional impairment. More importantly, trichostatin A, a pan-HDAC inhibitor, promoted functional recovery from stroke in WT mice when used in the delayed phase, but it was ineffective in Hdac2 conditional knockout (Hdac2 CKO) mice. Treatment with suberoylanilide hydroxamic acid, a selective HDAC1 and HDAC2 inhibitor, in the delayed phase of stroke produced sustained functional recovery in mice via epigenetically enhancing neuroplasticity of surviving neurons in the peri-infarct zone.

CONCLUSIONS

Our novel findings provide evidence that HDAC2 is a crucial target for functional recovery from stroke. As there are clinically available HDAC inhibitors, our findings could be directly translated into clinical research of stroke.

Chimeric Peptide Tat-HA-NR2B9c Improves Regenerative Repair after Transient Global Ischemia

Transient global ischemia (TGI) is a major public health problem, and it heightens the need of effective treatments. The present study was undertaken to investigate whether recombinant polypeptide Tat-HA-NR2B9c improves spatial learning and memory deficits in rats after TGI. Rats were subjected to 20-min ischemia induced by four-vessel occlusion (4-VO) method and daily injected with Tat-HA-NR2B9c (1.12 mg/kg) for 1 week. Tat-HA-NR2B9c increased CREB activity, upregulated B-cell lymphoma-2 (Bcl-2) expression after treated for 24 h. There was a significant increase in dendrite spine density in hippocampal CA1 region and BrdU-positive cells and BrdU/NeuN-positive cells in the dentate gyrus after Tat-HA-NR2B9c treatment, compared with ischemia group at postischemic day 28. Inhibition of the CREB activation by recombinant lentivirus, LV-CREB133-GFP, abolished the upregulation effects of Tat-HA-NR2B9c on Bcl-2 expression. Moreover, Tat-HA-NR2B9c improved the impaired spatial learning and memory ability in Morris water maze. These results suggest that Tat-HA-NR2B9c substantially ameliorated the TGI-induced loss of dendrite spine in hippocampal CA1, increased neurogenesis in dentate gyrus, and significantly improved cognitive abilities by the CREB pathway in rats after transient global cerebral ischemia. It may be served as a treatment for TGI.

Challenging the great vascular wall: Can we envision a simple yet comprehensive therapy for stroke?

Stroke is a leading cause of death in adult life, closely behind ischemic heart disease, and causes a significant and abiding socioeconomic burden. However, current therapies are not able to ensure full neurologic and/or sequelae-free recovery to all stroke survivors. We believe treatment efficacy and patient rehabilitation could be enhanced significantly by targeting blood-brain barrier (BBB) deregulation and inflammation-induced barrier loss that occurs after stroke. In this pathological context, bone marrow-derived endothelial progenitor cells (EPC) enter the bloodstream towards the lesion site, but their insufficient numbers and impaired angiogenic ability compromise neurovascular regeneration. In this context, cell-based therapies have become increasingly appealing since treating patients with large numbers of mesenchymal or hematopoietic stem/progenitor cells alone may boost repair. However, this approach could be met with several challenges in terms of logistics and cost; hence, the development of a drug delivery system suitable for intravenous administration and functionalized for selective uptake by circulating EPC could enhance their restorative potential without perceived complications. The ability to encapsulate proangiogenic and anti-inflammatory agents, such as retinoic acid, and to safely and easily deliver them systemically may open new therapeutic perspectives for the treatment of cerebrovascular disorders. Copyright © 2017 John Wiley & Sons, Ltd.

Regenerative repair of Pifithrin-α in cerebral ischemia via VEGF dependent manner

Promoting regenerative repair, including neurogenesis and angiogenesis, may provide a new therapeutic strategy for treatment of stroke. P53, a well-documented transcription factor, has been reported to be involved in cerebral ischemia and also serves as an important regulator of vascular endothelial growth factor (VEGF). However, the role of p53 in endogenous regenerative repair after brain ischemia is poorly understood. In this study, we investigated the effects of PFT-α, a specific p53 inhibitor on neurogenesis and angiogenesis improvement and associated signal pathways in rats impaired by cerebral artery occlusion (MCAo). PFT-α induced neuroprotection, reduced infarct volume and neurological functional impairment after ischemic stroke. More importantly, neurogenesis and angiogenesis were greatly enhanced by PFT-α, and accompanied by increased expression of VEGF. Moreover, we got consistent results in neural stem cells (NSCs) isolated from fetal rats. In contrast, application of the anti-VEGF neutralizing antibody (RB-222) partially reversed PFT-α-induced neuroprotection and rescued p53 expression. Noteworthily, inhibition of p53 after ischemic stroke in these rats improved their outcomes via promotion of regenerative repair. In conclusion, PFT-α could serve as a promising therapeutic strategy for ischemic stroke by promoting regenerative repair.

Innate Immunity and Inflammation Post-Stroke: An α7-Nicotinic Agonist Perspective

Stroke is one of the leading causes of death and long-term disability, with limited treatment options available. Inflammation contributes to damage tissue in the central nervous system across a broad range of neuropathologies, including Alzheimer's disease, pain, Schizophrenia, and stroke. While the immune system plays an important role in contributing to brain damage produced by ischemia, the damaged brain, in turn, can exert a powerful immune-suppressive effect that promotes infections and threatens the survival of stroke patients. Recently the cholinergic anti-inflammatory pathway, in particular its modulation using α7-nicotinic acetylcholine receptor (α7-nAChR) ligands, has shown potential as a strategy to dampen the inflammatory response and facilitate functional recovery in stroke patients. Here we discuss the current literature on stroke-induced inflammation and the effects of α7-nAChR modulators on innate immune cells.

Withania somnifera Improves Ischemic Stroke Outcomes by Attenuating PARP1-AIF-Mediated Caspase-Independent Apoptosis

Withania somnifera (WS), popularly known as "Ashwagandha" has been used for centuries as a nerve tonic. Its protective effect has been elucidated in many neurodegenerative pathologies, although there is a paucity of data regarding its effects in ischemic stroke. We examined the neuroprotective properties of an aqueous extract of WS in both pre- and poststroke treatment regimens in a mouse model of permanent distal middle cerebral artery occlusion (pMCAO). WS (200 mg/kg) improved functional recovery and significantly reduced the infarct volume in mice, when compared to those treated with vehicle, in both paradigms. We investigated the protective mechanism/s induced by WS using brain cortices by testing its ability to modulate the expression of key proteins in the ischemic-apoptotic cascade. The Western blots and immunofluorescence analyses of mice cortices revealed that WS upregulated the expression of hemeoxygenase 1 (HO1) and attenuated the expression of the proapoptotic protein poly (ADP-ribose) polymerase-1 (PARP1) via the PARP1-AIF pathway, thus preventing the nuclear translocation of apoptosis-inducing factor (AIF), and subsequent apoptosis. Semaphorin-3A (Sema3A) expression was reduced in WS-treated group, whereas Wnt, pGSK3β, and pCRMP2 expression levels were virtually unaltered. These results indicate the interplay of antioxidant-antiapoptic pathways and the possible involvement of angiogenesis in the protective mechanism of WS while emphasizing the noninvolvement of one of the prime pathways of neurogenesis. Our results suggest that WS could be a potential prophylactic as well as a therapeutic agent aiding stroke repair, and that part of its mechanism could be attributed to its antiapoptotic and antioxidant properties.

Models of care for late-life depression of the medically ill: examples from chronic obstructive pulmonary disease and stroke

Depression worsens most treatment outcomes in medically ill older adults. Chronic medical illnesses weaken and demoralize patients and compromise their ability to adhere to treatments requiring consistency and effort. Acute medical illnesses create a psychosocial storm that finds patients and their ecosystem unprepared. We describe two intervention models that can be used to target and personalize treatment in depressed, chronically, or acutely medically ill older adults. The Personalized Adherence Intervention for Depression and COPD (PID-C) is a model intervention for depressed patients with chronic medical illnesses. It targets patient-specific barriers to treatment engagement and aims to shift the balance in favor of treatment participation. PID-C led to higher remission rates of depression, reduction in depressive symptoms, and reduction in dyspnea-related disability. The addition of problem-solving training enables patients to use resources available to them and hopefully improve their outcomes. Ecosystem-focused therapy (EFT) is a model intervention for depression developing in the context of an acute medical event. It was developed for patients with poststroke depression (PSD) and targets five areas, part of the "psychosocial storm" originating from the patient's sudden disability and the resulting change in the patient's needs and family's life. A preliminary study suggests that EFT is feasible and efficacious in reducing depressive symptoms and signs and disability in PSD.

Delayed Administration of Tat-HA-NR2B9c Promotes Recovery After Stroke in Rats

BACKGROUND AND PURPOSE

Previous studies reported that Tat-NR2B9c, a peptide disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction, reduced ischemic damage in the acute phase after stroke. However, its effect in the subacute phase is unknown. The aim of this study is to determine whether disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction in the subacute phase promotes recovery after stroke.

METHODS

Studies were performed on Sprague-Dawley rats or nNOS(-/-) mice, and experimental ischemic stroke was induced by middle cerebral artery occlusion. Animals were treated with drugs starting at day 4 after ischemia. Sensorimotor functions and spatial learning and memory ability were assessed after drug treatment. Then, rats were euthanized for morphological observation and biochemical tests.

RESULTS

Disrupting the N-methyl-d-aspartate receptor-postsynaptic density protein-95 interaction with Tat-HA-NR2B9c significantly ameliorated the ischemia-induced impairments of spatial memory and sensorimotor functions in rats during subacute stage but did not improve stroke outcome in nNOS(-/-) mice. Consistent with the functional recovery, Tat-HA-NR2B9c substantially increased neurogenesis in the dentate gyrus and dendritic spine density of mature neurons in the motor cortex of rats, meanwhile, reversed the ischemia-induced formation of S-nitrosylation-cyclin-dependent kinase 5 and increased cyclin-dependent kinase 5 activity in ipsilateral hippocampus. However, directly blocking N-methyl-d-aspartate receptors with MK-801 or Ro 25-6981 did not show the beneficial effects above.

CONCLUSIONS

Dissociating N-methyl-d-aspartate receptor-postsynaptic density protein-95 coupling by Tat-HA-NR2B9c in the subacute phase after stroke promotes functional recovery, probably because of that it increases neurogenesis and dendritic spine density of mature neurons via regulating cyclin-dependent kinase 5 in the ischemic brain.

Enhanced interhemispheric functional connectivity compensates for anatomical connection damages in subcortical stroke

BACKGROUND AND PURPOSE

Motor recovery after stroke has been shown to be correlated with both the fractional anisotropy (FA) of the affected corticospinal tract (CST) and the interhemispheric resting-state functional connectivity (rsFC) of the primary motor cortex (M1). However, the role of the restoration or enhancement of the M1-M1 rsFC in motor recovery remains largely unknown. We aimed to clarify this issue by investigating the correlations between the M1-M1 rsFC and the integrity of the M1-M1 anatomic connection and the affected CST in chronic subcortical stroke patients with good motor outcomes.

METHODS

Twenty patients and 16 healthy controls underwent multimodal magnetic resonance imaging examinations. Diffusion tensor imaging was used to reconstruct the M1-M1 anatomic connection and bilateral CSTs. White matter integrity of these tracts was assessed using FA. Resting-state functional magnetic resonance imaging was used to calculate M1-M1 rsFC. Group differences in these measures were compared. Correlations between M1-M1 rsFC and FA of the M1-M1 anatomic connection and the affected CST were analyzed in patients with stroke.

RESULTS

Compared with healthy controls, patients with stroke exhibited significantly reduced FA in the affected CST and the M1-M1 anatomic connection and a significantly increased M1-M1 rsFC. The FA values of the affected CST were positively correlated with the M1-M1 anatomic connection, and these FA values were negatively correlated with the M1-M1 rsFC in these patients.

CONCLUSIONS

Our findings suggest that the M1-M1 anatomic connection impairment is secondary to CST damage, and the M1-M1 rsFC enhancement may reflect compensatory or reactive neural plasticity in stroke patients with CST impairment.

Optogenetic mapping after stroke reveals network-wide scaling of functional connections and heterogeneous recovery of the peri-infarct

We used arbitrary point channelrhodopsin-2 (ChR2) stimulation and wide-scale voltage sensitive dye (VSD) imaging in mice to map altered cortical connectivity at 1 and 8 weeks after a targeted cortical stroke. Network analysis based on optogenetic stimulation revealed a symmetrical sham network with distinct sensorimotor and association groupings. This symmetry was disrupted after stroke: at 1 week after stroke, we observed a widespread depression of optogenetically evoked activity that extended to the non-injured hemisphere; by 8 weeks, significant recovery was observed. When we considered the network as a whole, scaling the ChR2-evoked VSD responses from the stroke groups to match the sham group mean resulted in a relative distribution of responses that was indistinguishable from the sham group, suggesting network-wide down-scaling and connectional diaschisis after stroke. Closer inspection revealed that connections that had little connectivity with the peri-infarct, such as contralateral visual areas, tended to escape damage, whereas some connections near the peri-infarct were more severely affected. When connections within the peri-infarct were isolated, we did not observe equal down-scaling of responses after stroke. Peri-infarct sites that had weak connection strength in the sham condition tended to have the greatest relative post-stroke recovery. Our findings suggest that, during recovery, most cortical areas undergo homeostatic upscaling, resulting in a relative distribution of responses that is similar to the pre-stroke (sham) network, albeit still depressed. However, recovery within the peri-infarct zone is heterogeneous and these cortical points do not follow the recovery scaling factor expected for the entire network.

Stem cell transplantation enhances endogenous brain repair after experimental stroke

Stem cell transplantation for stroke treatment has been a promising therapy in small and large animal models, and many clinical trials are ongoing to establish this strategy in a clinical setting. However, the mechanism underlying functional recovery after stem cell transplantation has not been fully established and there is still a need to determine the ideal subset of stem cells for such therapy. We herein reviewed the recent evidences showing the underlying mechanism of functional recovery after cell transplantation, focusing on endogenous brain repair. First, angiogenesis/neovascularization is promoted by trophic factors including vascular endothelial growth factor secreted from stem cells, and stem cells migrated to the lesion along with the vessels. Second, axonal sprouting, dendritic branching, and synaptogenesis were enhanced altogether in the both ipsilateral and contralateral hemisphere remapping the pyramidal tract across the board. Finally, endogenous neurogenesis was also enhanced although little is known how much these neurogenesis contribute to the functional recovery. Taken together, it is clear that stem cell transplantation provides functional recovery via endogenous repair enhancement from multiple ways. This is important to maximize the effect of stem cell therapy after stroke, although it is still undetermined which repair mechanism is mostly contributed.

Interaction of nNOS with PSD-95 negatively controls regenerative repair after stroke

Stroke is a major public health concern. The lack of effective therapies heightens the need for new therapeutic targets. Mammalian brain has the ability to rewire itself to restore lost functionalities. Promoting regenerative repair, including neurogenesis and dendritic remodeling, may offer a new therapeutic strategy for the treatment of stroke. Here, we report that interaction of neuronal nitric oxide synthase (nNOS) with the protein postsynaptic density-95 (PSD-95) negatively controls regenerative repair after stroke in rats. Dissociating nNOS-PSD-95 coupling in neurons promotes neuronal differentiation of neural stem cells (NSCs), facilitates the migration of newborn cells into the injured area, and enhances neurite growth of newborn neurons and dendritic spine formation of mature neurons in the ischemic brain of rats. More importantly, blocking nNOS-PSD-95 binding during the recovery stage improves stroke outcome via the promotion of regenerative repair in rats. Histone deacetylase 2 in NSCs may mediate the role of nNOS-PSD-95 association. Thus, nNOS-PSD-95 can serve as a target for regenerative repair after stroke.

Lost in translation: rethinking approaches to stroke recovery

Stroke is the second leading cause of death and the preeminent cause of neurological disability. Attempts to limit brain injury after ischemic stroke with clot-dissolving drugs have met with great success but their use remains limited due to a narrow therapeutic time window and concern over serious side effects. Unfortunately, the neuroprotective strategy failed in clinical trials. A more promising approach is to promote recovery of function in people affected by stroke. Following stroke, there is a heightened critical period of plasticity that appears to be receptive to exogenous interventions (e.g., delivery of growth factors) designed to enhance neuroplasticity processes important for recovery. An emerging concept is that combinational therapies appear much more effective than single interventions in improving stroke recovery. One of the most promising interventions, with clinical feasibility, is enriched rehabilitation, a combination of environmental enrichment and task-specific therapy.

Delivery of iPS-NPCs to the Stroke Cavity within a Hyaluronic Acid Matrix Promotes the Differentiation of Transplanted Cells

Stroke is the leading cause of adult disability with ~80% being ischemic. Stem cell transplantation has been shown to improve functional recovery. However, the overall survival and differentiation of these cells is still low. The infarct cavity is an ideal location for transplantation as it is directly adjacent to the highly plastic peri-infarct region. Direct transplantation of cells near the infarct cavity has resulted in low cell viability. Here we deliver neural progenitor cells derived from induce pluripotent stem cells (iPS-NPC) to the infarct cavity of stroked mice encapsulated in a hyaluronic acid hydrogel matrix to protect the cells. To improve the overall viability of transplanted cells, each step of the transplantation process was optimized. Hydrogel mechanics and cell injection parameters were investigated to determine their effects on the inflammatory response of the brain and cell viability, respectively. Using parameters that balanced the desire to keep surgery invasiveness minimal and cell viability high, iPS-NPCs were transplanted to the stroke cavity of mice encapsulated in buffer or the hydrogel. While the hydrogel did not promote stem cell survival one week post-transplantation, it did promote differentiation of the neural progenitor cells to neuroblasts.

Phase II trial of the Sigma-1 receptor agonist cutamesine (SA4503) for recovery enhancement after acute ischemic stroke

BACKGROUND AND PURPOSE

The σ-1 receptor (Sig-1R) agonist cutamesine (SA4503) enhanced functional recovery after experimental stroke with a treatment initiation window of 48 hours and chronic treatment for 28 days. We conducted a phase 2 clinical trial exploring the safety, tolerability, dose range, and functional effects of cutamesine in patients with ischemic stroke.

METHODS

Subjects were randomized between 48 and 72 hours after stroke to receive cutamesine 1 mg/d, 3 mg/d, or placebo for 28 days. Effects on safety and function were assessed at baseline, at end of treatment (day 28), and at end of follow-up (day 56).

RESULTS

In 60 patients, treatment with both cutamesine dosages was safe and well tolerated without significant differences in numbers of treatment emergent or serious adverse events. No significant effect was observed on the primary efficacy measure (change in National Institutes of Health Stroke Scale from baseline to day 56) or modified Rankin Scale and Barthel Index scores. Post hoc analysis of moderately and severely affected patients (baseline National Institutes of Health Stroke Scale, ≥7 and ≥10) showed greater National Institutes of Health Stroke Scale improvements in the 3 mg/d cutamesine group when compared with placebo (P=0.034 and P=0.038, respectively). A trend toward a higher proportion being able to complete a 10m timed walk was observed for cutamesine-treated subjects.

CONCLUSIONS

Cutamesine was safe and well tolerated at both dosage levels. Although no significant effects on functional end points were seen in the population as a whole, greater improvement in National Institutes of Health Stroke Scale scores among patients with greater pretreatment deficits seen in post hoc analysis warrants further investigation. Additional studies should focus on the patient population with moderate-to-severe stroke.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov/show/NCT00639249. Unique identifier: NCT00639249. The EudraCT number is 2007-004840-60 (https://www.clinicaltrialsregister.eu/ctr-search/trial/2007-004840-60/GB).

Baclofen facilitates sleep, neuroplasticity, and recovery after stroke in rats

OBJECTIVE

Sleep disruption in the acute phase after stroke has detrimental effects on recovery in both humans and animals. Conversely, the effect of sleep promotion remains unclear. Baclofen (Bac) is a known non-rapid eye movement (NREM) sleep-promoting drug in both humans and animals. The aim of this study was to investigate the effect of Bac on stroke recovery in a rat model of focal cerebral ischemia (isch).

METHODS

Rats, assigned to three experimental groups (Bac/isch, saline/isch, or Bac/sham), were injected twice daily for 10 consecutive days with Bac or saline, starting 24 h after induction of stroke. The sleep-wake cycle was assessed by EEG recordings and functional motor recovery by single pellet reaching test (SPR). In order to identify potential neuroplasticity mechanisms, axonal sprouting and neurogenesis were evaluated. Brain damage was assessed by Nissl staining.

RESULTS

Repeated Bac treatment after ischemia affected sleep, motor function, and neuroplasticity, but not the size of brain damage. NREM sleep amount was increased significantly during the dark phase in Bac/isch compared to the saline/isch group. SPR performance dropped to 0 immediately after stroke and was recovered slowly thereafter in both ischemic groups. However, Bac-treated ischemic rats performed significantly better than saline-treated animals. Axonal sprouting in the ipsilesional motor cortex and striatum, and neurogenesis in the peri-infarct region were significantly increased in Bac/isch group.

CONCLUSION

Delayed repeated Bac treatment after stroke increased NREM sleep and promoted both neuroplasticity and functional outcome. These data support the hypothesis of the role of sleep as a modulator of poststroke recovery.

Optical imaging of disrupted functional connectivity following ischemic stroke in mice

Recent human neuroimaging studies indicate that spontaneous fluctuations in neural activity, as measured by functional connectivity magnetic resonance imaging (fcMRI), are significantly affected following stroke. Disrupted functional connectivity is associated with behavioral deficits and has been linked to long-term recovery potential. FcMRI studies of stroke in rats have generally produced similar findings, although subacute cortical reorganization following focal ischemia appears to be more rapid than in humans. Similar studies in mice have not been published, most likely because fMRI in the small mouse brain is technically challenging. Extending functional connectivity methods to mouse models of stroke could provide a valuable tool for understanding the link between molecular mechanisms of stroke repair and human fcMRI findings at the system level. We applied functional connectivity optical intrinsic signal imaging (fcOIS) to mice before and 72 h after transient middle cerebral artery occlusion (tMCAO) to examine how graded ischemic injury affects the relationship between functional connectivity and infarct volume, stimulus-induced response, and behavior. Regional changes in functional connectivity within the MCA territory were largely proportional to infarct volume. However, subcortical damage affected functional connectivity in the somatosensory cortex as much as larger infarcts of cortex and subcortex. The extent of injury correlated with cortical activations following electrical stimulation of the affected forelimb and with functional connectivity in the somatosensory cortex. Regional homotopic functional connectivity in motor cortex correlated with behavioral deficits measured using an adhesive patch removal test. Spontaneous hemodynamic activity within the infarct exhibited altered temporal and spectral features in comparison to intact tissue; failing to account for these regional differences significantly affected apparent post-stroke functional connectivity measures. Thus, several results were strongly dependent on how the resting-state data were processed. Specifically, global signal regression alone resulted in apparently distorted functional connectivity measures in the intact hemisphere. These distortions were corrected by regressing out multiple sources of variance, as performed in human fcMRI. We conclude that fcOIS provides a sensitive imaging modality in the murine stroke model; however, it is necessary to properly account for altered hemodynamics in injured brain to obtain accurate measures of functional connectivity.

Contribution of the resting-state functional connectivity of the contralesional primary sensorimotor cortex to motor recovery after subcortical stroke

It remains uncertain if the contralesional primary sensorimotor cortex (CL_PSMC) contributes to motor recovery after stroke. Here we investigated longitudinal changes in the resting-state functional connectivity (rsFC) of the CL_PSMC and their association with motor recovery. Thirteen patients who had experienced subcortical stroke underwent a series of resting-state fMRI and clinical assessments over a period of 1 year at 5 time points, i.e., within the first week, at 2 weeks, 1 month, 3 months, and 1 year after stroke onset. Thirteen age- and gender-matched healthy subjects were recruited as controls. The CL_PSMC was defined as a region centered at the voxel that had greatest activation during hand motion task. The dynamic changes in the rsFCs of the CL_PSMC within the whole brain were evaluated and correlated with the Motricity Index (MI) scores. Compared with healthy controls, the rsFCs of the CL_PSMC with the bilateral PSMC were initially decreased, then gradually increased, and finally restored to the normal level 1 year later. Moreover, the dynamic change in the inter-hemispheric rsFC between the bilateral PSMC in these patients was positively correlated with the MI scores. However, the intra-hemispheric rsFC of the CL_PSMC was not correlated with the MI scores. This study shows dynamic changes in the rsFCs of the CL_PSMC after stroke and suggests that the increased inter-hemispheric rsFC between the bilateral PSMC may facilitate motor recovery in stroke patients. However, generalization of our findings is limited by the small sample size of our study and needs to be confirmed.

Voluntary forced use of the impaired limb following stroke facilitates functional recovery in the rat

Constraint induced movement therapy (CIMT), which forces use of the impaired arm following stroke, improves functional recovery. The mechanisms underlying recovery are not well understood, necessitating further investigation into how rehabilitation may affect neuroplasticity using animal models. Animal motivation and stress make modelling CIMT in animals challenging. We have shown that following focal ischemia, voluntary forced use therapy using pet activity balls could engage the impaired forelimb and result in a modest acceleration in recovery. In this study, we investigated the effects of a more intensive appetitively motivated regimen that included task specific reaching exercises. Adult male Sprague Dawley rats were subjected to focal unilateral stroke using intracerebral injections of endothelin-1 or sham surgery. Three days later, stroke animals were assigned to daily rehabilitation or control therapy. Rehabilitation consisted of 30 min of generalized movement sessions in activity balls, followed by 30 min of voluntary task-specific movement using reaching boxes. Rats were tested weekly to measure forelimb deficit and recovery. After 30 days, animals were euthanized and tissue was examined for infarct volume, brain derived neurotrophic factor expression, and the presence of new neurons using doublecortin immunohistochemistry. Rehabilitation resulted in a significant acceleration of forelimb recovery in several tests, and a significant increase in the number of doublecortin-expressing cells. Furthermore, while the proportion of cells expressing BDNF in the peri-infarct region did not change, there was a shift in the cellular origin of expressed BDNF, resulting in significantly more non-neuronal, non-astrocytic BDNF, presumed to be of microglial origin.

Factors secreted by endothelial progenitor cells enhance neurorepair responses after cerebral ischemia in mice

Cell therapy with endothelial progenitor cells (EPCs) has emerged as a promising strategy to regenerate the brain after stroke. Here, we aimed to investigate if treatment with EPCs or their secreted factors could potentiate angiogenesis and neurogenesis after permanent focal cerebral ischemia in a mouse model of ischemic stroke. BALB/C male mice were subjected to distal occlusion of the middle cerebral artery, and EPCs, cell-free conditioned media (CM) obtained from EPCs, or vehicle media were administered one day after ischemia. Magnetic resonance imaging (MRI) was performed at baseline to confirm that the lesions were similar between groups. Immunohistochemical and histological evaluation of the brain was performed to evaluate angio-neurogenesis and neurological outcome at two weeks. CM contained growth factors, such as VEGF, FGF-b and PDGF-bb. A significant increase in capillary density was noted in the peri-infarct areas of EPC- and CM-treated animals. Bielschowsky's staining revealed a significant increase in axonal rewiring in EPC-treated animals compared with shams, but not in CM-treated mice, in close proximity with DCX-positive migrating neuroblasts. At the functional level, post-ischemia forelimb strength was significantly improved in animals receiving EPCs or CM, but not in those receiving vehicle media. In conclusion, we demonstrate for the first time that the administration of EPC-secreted factors could become a safe and effective cell-free option to be considered in future therapeutic strategies for stroke.

Cerebral ischaemia and matrix metalloproteinase-9 modulate the angiogenic function of early and late outgrowth endothelial progenitor cells

The enhancement of endogenous angiogenesis after stroke will be critical in neurorepair therapies where endothelial progenitor cells (EPCs) might be key players. Our aim was to determine the influence of cerebral ischaemia and the role of matrix metalloproteinase-9 (MMP-9) on the angiogenic function of EPCs. Permanent focal cerebral ischaemia was induced by middle cerebral artery (MCA) occlusion in MMP-9/knockout (MMP-9/KO) and wild-type (WT) mice. EPCs were obtained for cell counting after ischaemia (6 and 24 hrs) and in control animals. Matrigel(™) assays and time-lapse imaging were conducted to monitor angiogenic function of WT and MMP9-deficient EPCs or after treatment with MMP-9 inhibitors. Focal cerebral ischaemia increased the number of early EPCs, while MMP-9 deficiency decreased their number in non-ischaemic mice and delayed their release after ischaemia. Late outgrowth endothelial cells (OECs) from ischaemic mice shaped more vessel structures than controls, while MMP-9 deficiency reduced the angiogenic abilities of OECs to form vascular networks, in vitro. Treatment with the MMP inhibitor GM6001 and the specific MMP-9 inhibitor I also decreased the number of vessel structures shaped by both human and mouse WT OECs, while exogenous MMP-9 could not revert the impaired angiogenic function in MMP-9/KO OECs. Finally, time-lapse imaging showed that the extension of vascular networks was influenced by cerebral ischaemia and MMP-9 deficiency early during the vascular network formation followed by a dynamic vessel remodelling. We conclude that focal cerebral ischaemia triggers the angiogenic responses of EPCs, while MMP-9 plays a key role in the formation of vascular networks by EPCs.

In vitro angiogenic performance and in vivo brain targeting of magnetized endothelial progenitor cells for neurorepair therapies

Endothelial progenitor cells (EPCs) represent a promising approach for cell-based therapies to induce tissue repair; however, their effective delivery into the brain has remained a challenge. We loaded EPCs with superparamagnetic iron oxide nanoparticles (SPIONs), assessed their angiogenic potential and evaluated their guidance to the brain using an external magnet. SPIONs were stored in the cytoplasm within endosomes/lysosomes as observed by transmission electron microscopy (TEM) and could be visualized as hypointense signals by magnetic resonance imaging (MRI) T2-weighted images. In vitro SPION-loaded EPCs were fully functional, forming vessel-like structures in Matrigel®, and displayed enhanced migration and secretion of growth factors (VEGF and FGF), which was associated with a moderate increase in reactive oxygen species production. Furthermore, in vivo MRI of treated mice showed accumulated hypointense signals consistent with SPION-loaded EPCs engraftment. Thus, we demonstrate that loading EPCs with SPIONs represents a safe and effective strategy for precise cell guidance into specific brain areas.

FROM THE CLINICAL EDITOR

This study investigates the potential role of endothelial progenitor cells in neuro-repair strategies of the central nervous system using SPION-loaded EPCs and magnetic guidance to the target organ. The authors demonstrate ex vivo cellular viability and maintained function following SPION load as well as successful guidance of the EPCs to the target site via MR imaging in a murine model.

Is sleep essential for neural plasticity in humans, and how does it affect motor and cognitive recovery?

There is a general consensus that sleep is strictly linked to memory, learning, and, in general, to the mechanisms of neural plasticity, and that this link may directly affect recovery processes. In fact, a coherent pattern of empirical findings points to beneficial effect of sleep on learning and plastic processes, and changes in synaptic plasticity during wakefulness induce coherent modifications in EEG slow wave cortical topography during subsequent sleep. However, the specific nature of the relation between sleep and synaptic plasticity is not clear yet. We reported findings in line with two models conflicting with respect to the underlying mechanisms, that is, the “synaptic homeostasis hypothesis” and the “consolidation” hypothesis, and some recent results that may reconcile them. Independently from the specific mechanisms involved, sleep loss is associated with detrimental effects on plastic processes at a molecular and electrophysiological level. Finally, we reviewed growing evidence supporting the notion that plasticity-dependent recovery could be improved managing sleep quality, while monitoring EEG during sleep may help to explain how specific rehabilitative paradigms work. We conclude that a better understanding of the sleep-plasticity link could be crucial from a rehabilitative point of view.