Erythropoietin increases neurogenesis and oligodendrogliosis of subventricular zone precursor cells after neonatal stroke

The long-term effect of erythropoiesis stimulating agents given to preterm infants: a proton magnetic resonance spectroscopy study on neurometabolites in early childhood

BACKGROUND

Erythropoiesis stimulating agents (ESAs) are neuroprotective in cell and animal models of preterm birth. Prematurity has been shown to alter neurometabolite levels in children in studies using proton magnetic resonance spectroscopy (1H-MRS).

OBJECTIVE

We hypothesized that ESA treatment in premature infants would tend to normalize neurometabolites by 4-6 years of age.

MATERIALS AND METHODS

Children in a longitudinal study of neurodevelopment underwent MRI and 1H-MRS at approximately 4 years and 6 years of age. Prematurely born children (500-1,250 g birth weight) received ESAs (erythropoietin or darbepoetin) or placebo during their neonatal hospitalization, and these groups were compared to healthy term controls. 1H-MRS spectra were obtained from the anterior cingulate (gray matter) and frontal lobe white matter, assessing combined N-acetylaspartate and N-acetylaspartylglutamate (tNAA), myo-inositol, choline compounds (Cho), combined creatine and phosphocreatine, and combined glutamate and glutamine.

RESULTS

No significant (P≤0.5) group differences were observed for any metabolite level. Significant age-related increases in white-matter tNAA and Cho were observed, as well as a trend for increased gray-matter tNAA.

CONCLUSION

Neither prematurity nor neonatal ESA treatment was associated with differences in brain metabolite levels in the children of this study at a significance level of 0.05. These findings suggest that earlier differences that might have existed had normalized by 4-6 years of age or were too small to be statistically significant in the current sample.

Erythropoietin attenuates motor neuron programmed cell death in a burn animal model

Burn-induced neuromuscular dysfunction may contribute to long-term morbidity; therefore, it is imperative to develop novel treatments. The present study investigated whether erythropoietin (EPO) administration attenuates burn-induced motor neuron apoptosis and neuroinflammatory response. To validate our hypothesis, a third-degree hind paw burn rat model was developed by bringing the paw into contact with a metal surface at 75°C for 10 s. A total of 24 male Sprague–Dawley rats were randomly assigned to four groups: Group A, sham-control; Group B, burn-induced; Group C, burn + single EPO dose (5000 IU/kg i.p. at D0); and Group D, burn + daily EPO dosage (3000 IU/kg/day i.p. at D0–D6). Two treatment regimens were used to evaluate single versus multiple doses treatment effects. Before sacrifice, blood samples were collected for hematological parameter examination. The histological analyses of microglia activation, iNOS, and COX-2 in the spinal cord ventral horn were performed at week 1 post-burn. In addition, we examined autophagy changes by biomarkers of LC3B and ATG5. The expression of BCL-2, BAX, cleaved caspase-3, phospho-AKT, and mTOR was assessed simultaneously through Western blotting. EPO administration after burn injury attenuated neuroinflammation through various mechanisms, including the reduction of microglia activity as well as iNOS and COX-2 expression in the spinal cord ventral horn. In addition, the expression of phospho-AKT, mTOR and apoptotic indicators, such as BAX, BCL-2, and cleaved caspase-3, was modulated. Furthermore, the activity of burn-induced autophagy in the spinal cord ventral horn characterized by the expression of autophagic biomarkers, LC3B and ATG5, was reduced after EPO administration. The present results indicate that EPO inhibits the AKT-mTOR pathway to attenuate burn-induced motor neuron programmed cell death and microglia activation. EPO can modulate neuroinflammation and programmed cell death and may be a therapeutic candidate for neuroprotection.

Promoting neuroregeneration after perinatal arterial ischemic stroke: neurotrophic factors and mesenchymal stem cells

Newborns suffering from perinatal arterial ischemic stroke (PAIS) are at risk of neurodevelopmental problems. Current treatment options for PAIS are limited and mainly focus on supportive care, as presentation of PAIS is beyond the time window of current treatment strategies. Therefore, recent focus has shifted to interventions that stimulate regeneration of damaged brain tissue. From animal models, it is known that the brain increases its neurogenic capability after ischemic injury, by promoting neural cell proliferation and differentiation. However, neurogenesis is not maintained at the long term, which consequently impedes full repair leading to adverse consequences later in life. Boosting neuroregeneration of the newborn brain using treatment with neurotrophic factors and/or mesenchymal stem cells (MSCs) may be promising novel therapeutic strategies to improve neurological prospects and quality of life of infants with PAIS. This review focuses on effectiveness of neurotrophic growth factors, including erythropoietin, brain-derived neurotrophic factor, vascular endothelial growth factor, glial-derived neurotrophic factor, and MSC therapy, in both experimental neonatal stroke studies and first clinical trials for neonatal ischemic brain injury.

Pediatric brain repair from endogenous neural stem cells of the subventricular zone

There is great interest in the regenerative potential of the neural stem cells and progenitors that populate the germinal zones of the immature brain. Studies using animal models of pediatric brain injuries have provided a clearer understanding of the responses of these progenitors to injury. In this review, we have compared and contrasted the responses of the endogenous neural stem cells and progenitors of the subventricular zone in animal models of neonatal cerebral hypoxia-ischemia, neonatal stroke, congenital cardiac disease, and pediatric traumatic brain injury. We have reviewed the dynamic shifts that occur within this germinal zone with injury as well as changes in known signaling molecules that affect these progenitors. Importantly, we have summarized data on the extent to which cell replacement occurs in response to each of these injuries, opportunities available, and obstacles that will need to be overcome to improve neurological outcomes in survivors.

Neonatal erythropoietin mitigates impaired gait, social interaction and diffusion tensor imaging abnormalities in a rat model of prenatal brain injury

Children who are born preterm are at risk for encephalopathy of prematurity, a leading cause of cerebral palsy, cognitive delay and behavioral disorders. Current interventions are limited and none have been shown to reverse cognitive and behavioral impairments, a primary determinant of poor quality of life for these children. Moreover, the mechanisms of perinatal brain injury that result in functional deficits and imaging abnormalities in the mature brain are poorly defined, limiting the potential to target interventions to those who may benefit most. To determine whether impairments are reversible after a prenatal insult, we investigated a spectrum of functional deficits and diffusion tensor imaging (DTI) abnormalities in young adult animals. We hypothesized that prenatal transient systemic hypoxia-ischemia (TSHI) would induce multiple functional deficits concomitant with reduced microstructural white and gray matter integrity, and tested whether these abnormalities could be ameliorated using postnatal erythropoietin (EPO), an emerging neurorestorative intervention. On embryonic day 18 uterine arteries were transiently occluded for 60min via laparotomy. Shams underwent anesthesia and laparotomy for 60min. Pups were born and TSHI pups were randomized to receive EPO or vehicle via intraperitoneal injection on postnatal days 1 to 5. Gait, social interaction, olfaction and open field testing was performed from postnatal day 25-35 before brains underwent ex vivo DTI to measure fractional anisotropy, axial diffusivity and radial diffusivity. Prenatal TSHI injury causes hyperactivity, impaired gait and poor social interaction in young adult rats that mimic the spectrum of deficits observed in children born preterm. Collectively, these data show for the first time in a model of encephalopathy of prematurity that postnatal EPO treatment mitigates impairments in social interaction, in addition to gait deficits. EPO also normalizes TSHI-induced microstructural abnormalities in fractional anisotropy and radial diffusivity in multiple regions, consistent with improved structural integrity and recovery of myelination. Taken together, these results show behavioral and memory deficits from perinatal brain injury are reversible. Furthermore, resolution of DTI abnormalities may predict responsiveness to emerging interventions, and serve as a biomarker of CNS injury and recovery.

Erythropoietin Signaling Regulates Key Epigenetic and Transcription Networks in Fetal Neural Progenitor Cells

Erythropoietin (EPO) and its receptor are highly expressed in the developing nervous system, and exogenous EPO therapy is potentially neuroprotective, however the epigenetic and transcriptional changes downstream of EPO signaling in neural cells are not well understood. To delineate epigenetic changes associated with EPO signaling, we compared histone H3 lysine 4 dimethylation (H3K4me2) in EPO treated and control fetal neural progenitor cells, identifying 1,150 differentially bound regions. These regions were highly enriched near protein coding genes and had significant overlap with H4Acetylation, a mark of active regulatory elements. Motif analyses and co-occupancy studies revealed a complex regulatory network underlying the differentially bound regions, including previously identified mediators of EPO signaling (STAT5, STAT3), and novel factors such as REST, an epigenetic modifier central to neural differentiation and plasticity, and NRF1, a key regulator of antioxidant response and mitochondrial biogenesis. Global transcriptome analyses on neural tubes isolated from E9.0 EpoR-null and littermate control embryos validated our in vitro findings, further suggesting a role for REST and NRF1 downstream of EPO signaling. These data support a role for EPO in regulating the survival, proliferation, and differentiation of neural progenitor cells, and suggest a basis for its function in neural development and neuroprotection.

Erythropoietin signaling increases neurogenesis and oligodendrogenesis of endogenous neural stem cells following spinal cord injury both in vivo and in vitro

Erythropoietin (Epo) promotes functional recovery following spinal cord injury (SCI); however, the exact underlying mechanisms are yet to be determined. Although endogenous neural stem cells (NSCs) in the adult spinal cord are a therapeutic target in SCI models, the effect of Epo on this NSC population remains unknown. The present study investigated the effects of Epo on endogenous NSCs in the adult spinal cord both in vitro and in vivo. For the in vivo analyses, normal rats (Normal) and SCI contusion model rats (SCI) received either recombinant human Epo or saline treatment for 7 days (5,000 U/kg), and spinal cords were subsequently analyzed at 2, 8, and 14 days. For in vitro analyses, NSCs harvested from adult rat spinal cords were exposed to Epo (10 U/ml). A significant increase in β-tubulin⁺ new neurons (P<0.01) was observed at all three time points and O4⁺ new oligodendrocytes (P<0.05) at days 8 and 14 in the SCI+Epo group compared with the SCI+Saline group. This was concomitant with a prolonged activation of Epo signaling; however, no effect on NSCs proliferation was observed. Similar results were also obtained in vitro. Motor functional recovery was also noted at days 8 and 14 only in the Epo-treated SCI rats. Although the expression of Epo and EpoR significantly increased in Normal+Epo rats compared with Normal+Saline rats (P<0.05), the cell numbers and phenotype were comparable between the two groups. To the best of the author's knowledge, this is the first study to demonstrate that Epo signaling promotes both neurogenesis and oligodendrogenesis following SCI and that these may represent the underlying mechanisms for the functional recovery and therapeutic effects of Epo following SCI.

White matter injury in the preterm infant: pathology and mechanisms

The human preterm brain is particularly susceptible to cerebral white matter injury (WMI) that disrupts the normal progression of developmental myelination. Advances in the care of preterm infants have resulted in a sustained reduction in the severity of WMI that has shifted from more severe focal necrotic lesions to milder diffuse WMI. Nevertheless, WMI remains a global health problem and the most common cause of chronic neurological morbidity from cerebral palsy and diverse neurobehavioral disabilities. Diffuse WMI involves maturation-dependent vulnerability of the oligodendrocyte (OL) lineage with selective degeneration of late oligodendrocyte progenitors (preOLs) triggered by oxidative stress and other insults. The magnitude and distribution of diffuse WMI are related to both the timing of appearance and regional distribution of susceptible preOLs. Diffuse WMI disrupts the normal progression of OL lineage maturation and myelination through aberrant mechanisms of regeneration and repair. PreOL degeneration is accompanied by early robust proliferation of OL progenitors that regenerate and augment the preOL pool available to generate myelinating OLs. However, newly generated preOLs fail to differentiate and initiate myelination along their normal developmental trajectory despite the presence of numerous intact-appearing axons. Disrupted preOL maturation is accompanied by diffuse gliosis and disturbances in the composition of the extracellular matrix and is mediated in part by inhibitory factors derived from reactive astrocytes. Signaling pathways implicated in disrupted myelination include those mediated by Notch, WNT-beta catenin, and hyaluronan. Hence, there exists a potentially broad but still poorly defined developmental window for interventions to promote white matter repair and myelination and potentially reverses the widespread disturbances in cerebral gray matter growth that accompanies WMI.

Manipulation of neural progenitor fate through the oxygen sensing pathway

Neural progenitor cells hold significant promise in a variety of clinical settings. While both the brain and spinal cord harbor endogenous neural progenitor or stem cells, they typically are not capable of repopulating neural populations in case of injury or degenerative disease. In vitro systems for the culture of neural progenitors has come a long ways due to advances in the method development. Recently, many groups have shown that manipulation of the oxygen-sensing pathway leading to activation of hypoxia inducible factors (HIFs) that can influence the proliferation, differentiation or maturation of neural progenitors. Moreover, different oxygen concentrations appear to affect lineage specification of neural progenitors upon their differentiation in vitro. Here we summarize some of these studies in an attempt to direct effort towards implementation of best methods to advance the use of neural progenitors from basic development towards clinical application.

The Differential Effects of Erythropoietin Exposure to Oxidative Stress on Microglia and Astrocytes in vitro

The neonatal brain is especially susceptible to oxidative stress owing to its reduced antioxidant capacity. Following hypoxic-ischemic (HI) injury, for example, there is a prolonged elevation in levels of hydrogen peroxide (H2O2) in the immature brain compared to the adult brain, resulting in lasting injury that can lead to life-long disability or morbidity. Erythropoietin (Epo) is one of few multifaceted treatment options that have been promising enough to trial in the clinic for both term and preterm brain injury. Despite this, there is a lack of clear understanding of how Epo modulates glial cell activity following oxidative injury, specifically, whether it affects microglia (Mg) and astrocytes (Ast) differently. Using an in vitro approach using primary murine Mg and Ast subjected to H2O2 injury, we studied the oxidative and inflammatory responses of Mg and Ast to recombinant murine (rm)Epo treatment. We found that Epo protects Ast from H2O2 injury (p < 0.05) and increases secreted nitric oxide levels in these cells (p < 0.05) while suppressing intracellular reactive oxygen species (p < 0.05) and superoxide ion (p < 0.05) levels only in Mg. Using a multiplex analysis, we noted that although H2O2 induced the levels of several chemokines, rmEpo did not have any significant specific effects on their levels, either with or without the presence of conditioned medium from injured neurons (NCM). Ultimately, it appears that rmEpo has pleiotropic effects based on the cell type; it has a protective effect on Ast but an antioxidative effect only on Mg without any significant modulation of chemokine and cytokine levels in either cell type. These findings highlight the importance of considering all cell types when assessing the benefits and pitfalls of Epo use.

Prophylactic Early Erythropoietin for Neuroprotection in Preterm Infants: A Meta-analysis

CONTEXT

Recombinant human erythropoietin (rhEPO) is a promising pharmacological agent for neuroprotection in neonates.

OBJECTIVE

To investigate whether prophylactic rhEPO administration in very preterm infants improves neurodevelopmental outcomes in a meta-analysis of randomized controlled trials (RCTs).

DATA SOURCES

Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched in December 2016 and complemented by other sources.

STUDY SELECTION

RCTs investigating the use of rhEPO in preterm infants versus a control group were selected if they were published in a peer-reviewed journal and reported neurodevelopmental outcomes at 18 to 24 months' corrected age.

DATA EXTRACTION

Data extraction and analysis followed the standard methods of the Cochrane Neonatal Review Group. The primary outcome was the number of infants with a Mental Developmental Index (MDI) <70 on the Bayley Scales of Infant Development. Secondary outcomes included a Psychomotor Development Index <70, cerebral palsy, visual impairment, and hearing impairment.

RESULTS

Four RCTs, comprising 1133 infants, were included in the meta-analysis. Prophylactic rhEPO administration reduced the incidence of children with an MDI <70, with an odds ratio (95% confidence interval) of 0.51 (0.31-0.81), P < .005. The number needed to treat was 14. There was no statistically significant effect on any secondary outcome.

CONCLUSIONS

Prophylactic rhEPO improved the cognitive development of very preterm infants, as assessed by the MDI at a corrected age of 18 to 24 months, without affecting other neurodevelopmental outcomes. Current and future RCTs should investigate optimal dosing and timing of prophylactic rhEPO and plan for long-term neurodevelopmental follow-up.

Erythropoietin Treatment Exacerbates Moderate Injury after Hypoxia-Ischemia in Neonatal Superoxide Dismutase Transgenic Mice

The neonatal brain is highly susceptible to oxidative stress as developing endogenous antioxidant mechanisms are overwhelmed. In the neonate, superoxide dismutase (SOD) overexpression worsens hypoxic-ischemic injury due to H2O2 accumulation in the brain. Erythropoietin (EPO) is upregulated in 2 phases after HI, early (4 h) and late (7 days), and exogenous EPO has been effective in reducing the injury, possibly through reducing oxidative stress. We hypothesized that exogenous EPO would limit injury from excess H2O2 seen in SOD1-overexpressing mice, and thus enhance recovery after HI. We first wanted to confirm our previous findings in postnatal day 7 (P7) SOD-tg (CD1) mice using a P9 model of the Vannucci procedure of HI with SOD-tg mice from a different background strain (C57Bl/6), and then determine the efficacy of EPO treatment in this strain and their wild-type (WT) littermates. Thus, mice overexpressing copper/zinc SOD1 were subjected to HI, modified for the P9 mouse, and recombinant EPO (5 U/g) or vehicle (saline) was administered intraperitoneally 3 times: at 0 h, 24 h, and 5 days. Injury was assessed 7 days after HI. In addition, protein expression for EPO and EPO receptor was assessed in the cortex and hippocampus 24 h after HI. With the moderate insult, the SOD-tg mice had greater injury than the WT overall, confirming our previous results, as did the hippocampus and striatum when analyzed separately, but not the cortex or thalamus. EPO treatment worsened injury in SOD-tg overall and in the WT and SOD-tg hippocampus and striatum. With the more severe insult, all groups had greater injury than with the moderate insult, but differences between SOD-tg and WT were no longer observed and EPO treatment had no effect. Increased protein expression of EPO was observed in the cortex of SOD-tg mice given recombinant human EPO compared to SOD-tg given vehicle. This study confirms our previous results showing greater injury with SOD overexpression in the neonatal brain after HI at P7 in a different strain. These results also suggest that EPO treatment cannot ameliorate the damage seen in situations where there is excess H2O2 accumulation, and it may exacerbate injury in settings of extreme oxidative stress.

Transient Middle Cerebral Artery Occlusion Model of Neonatal Stroke in P10 Rats

A number of animal models have been used to study hypoxic-ischemic injury, traumatic injury, global hypoxia, or permanent ischemia in both the immature and mature brain. Stroke occurs commonly in the perinatal period in humans, and transient ischemia-reperfusion is the most common form of stroke in neonates. The reperfusion phase is a critical component of injury progression, which occurs over a period of days to weeks, and of the endogenous response to injury. This postnatal day 10 (p10) rat model of transient middle cerebral artery occlusion (tMCAO) creates a unilateral, non-hemorrhagic focal ischemia-reperfusion injury that can be utilized to study the mechanisms of focal injury and repair in the full-term-equivalent brain. The injury pattern that is produced by tMCAO is consistent and highly reproducible and can be confirmed with MRI or histological analyses. The severity of injury can be manipulated through changes in occlusion time and other methods that will be discussed.

Endothelial Progenitor Cells' Classification and Application in Neurological Diseases

The therapeutic effects of endothelial progenitor cells (EPCs) on ischemic stroke have been extensively studied in recent years. However, the differences in early EPCs and endothelial outgrowth cells (EOCs) are still unclear. Clarifications of their respective properties and specific functioning characteristics contribute to better applications of EPCs in ischemic diseases. In this review, we discuss cellular origin, isolation, culture, surface markers of early EPCs and EOCs and relevant applications in neurological diseases. We conclude that EOCs possess all characteristics of true endothelial progenitors and have potent advantages in EPC-based therapies for ischemic diseases. A number of preclinical and clinical applications of EPCs in neurological diseases are under study. More studies are needed to determine the specific characteristics of EPCs and the relevant mechanisms of EPCs for neurological diseases.

Partial white and grey matter protection with prolonged infusion of recombinant human erythropoietin after asphyxia in preterm fetal sheep

Perinatal asphyxia in preterm infants remains a significant contributor to abnormal long-term neurodevelopmental outcomes. Recombinant human erythropoietin has potent non-haematopoietic neuroprotective properties, but there is limited evidence for protection in the preterm brain. Preterm (0.7 gestation) fetal sheep received sham asphyxia (sham occlusion) or asphyxia induced by umbilical cord occlusion for 25 min, followed by an intravenous infusion of vehicle (occlusion-vehicle) or recombinant human erythropoietin (occlusion-Epo, 5000 international units by slow push, then 832.5 IU/h), starting 30 min after asphyxia and continued until 72 h. Recombinant human erythropoietin reduced neuronal loss and numbers of caspase-3-positive cells in the striatal caudate nucleus, CA3 and dentate gyrus of the hippocampus, and thalamic medial nucleus ( P < 0.05 vs. occlusion-vehicle). In the white matter tracts, recombinant human erythropoietin increased total, but not immature/mature oligodendrocytes ( P < 0.05 vs. occlusion-vehicle), with increased cell proliferation and reduced induction of activated caspase-3, microglia and astrocytes ( P < 0.05). Finally, occlusion-Epo reduced seizure burden, with more rapid recovery of electroencephalogram power, spectral edge frequency, and carotid blood flow. In summary, prolonged infusion of recombinant human erythropoietin after severe asphyxia in preterm fetal sheep was partially neuroprotective and improved electrophysiological and cerebrovascular recovery, in association with reduced apoptosis and inflammation.

Role of Antioxidants in Neonatal Hypoxic-Ischemic Brain Injury: New Therapeutic Approaches

Hypoxic-ischemic brain damage is an alarming health and economic problem in spite of the advances in neonatal care. It can cause mortality or detrimental neurological disorders such as cerebral palsy, motor impairment and cognitive deficits in neonates. When hypoxia-ischemia occurs, a multi-faceted cascade of events starts out, which can eventually cause cell death. Lower levels of oxygen due to reduced blood supply increase the production of reactive oxygen species, which leads to oxidative stress, a higher concentration of free cytosolic calcium and impaired mitochondrial function, triggering the activation of apoptotic pathways, DNA fragmentation and cell death. The high incidence of this type of lesion in newborns can be partly attributed to the fact that the developing brain is particularly vulnerable to oxidative stress. Since antioxidants can safely interact with free radicals and terminate that chain reaction before vital molecules are damaged, exogenous antioxidant therapy may have the potential to diminish cellular damage caused by hypoxia-ischemia. In this review, we focus on the neuroprotective effects of antioxidant treatments against perinatal hypoxic-ischemic brain injury, in the light of the most recent advances.

Current Opinion on the Role of Neurogenesis in the Therapeutic Strategies for Alzheimer Disease, Parkinson Disease, and Ischemic Stroke; Considering Neuronal Voiding Function

Neurological diseases such as Alzheimer, Parkinson, and ischemic stroke have increased in occurrence and become important health issues throughout the world. There is currently no effective therapeutic strategy for addressing neurological deficits after the development of these major neurological disorders. In recent years, it has become accepted that adult neural stem cells located in the subventricular and subgranular zones have the ability to proliferate and differentiate in order to replace lost or damaged neural cells. There have been many limitations in the clinical application of both endogenous and exogenous neurogenesis for neurological disorders. However, many studies have investigated novel mechanisms in neurogenesis and have shown that these limitations can potentially be overcome with appropriate stimulation and various approaches. We will review concepts related to possible therapeutic strategies focused on the perspective of neurogenesis for the treatment of patients diagnosed with Alzheimer disease, Parkinson disease, and ischemic stroke based on current reports.

Recent Advances in Stem Cell-Based Therapeutics for Stroke

Regenerative medicine for central nervous system disorders, including stroke, has challenged the non-regenerative capacity of the brain. Among the many treatment strategies tailored towards repairing the injured brain, stem cell-based therapeutics have been demonstrated as safe and effective in animal models of stroke, and are being tested in limited clinical trials. We address here key lab-to-clinic translational research that relate to efficacy, safety, and mechanism of action underlying stem cell therapy. Recognizing the multi-pronged cell death processes associated with stroke that will likely require combination therapies, we next discuss potent drugs and novel technologies directed at improving the functional outcomes of stem cell-based therapeutics. We also examine discrepant transplant regimens between preclinical studies and clinical trials, as well as missing appropriate control arm (i.e., stroke subjects undergoing rehabilitation) on which to directly compare the therapeutic benefits of cell therapy. Finally, the bioethics of cell therapy is presented in order to assess its prevailing social status. With preliminary results now being reported from on-going clinical trials of stem cell therapy for stroke, a careful assessment of the true functional benefits of this novel treatment will further direct the future of regenerative medicine for neurological disorders.

Hollow manganese oxide nanoparticle-enhanced MRI of hypoxic-ischaemic brain injury in the neonatal rat

OBJECTIVE

To determine the utility of hollow manganese oxide nanoparticle (HMON)-enhanced MRI in depicting and monitoring apoptotic area following hypoxic-ischaemic injury in a neonatal rat brain and to evaluate the longitudinal evolution of hypoxic-ischaemic brain injury (HII) up to 21 days.

METHODS

The institutional animal care and use committee approval was obtained. The Rice-Vannucci model of HII was used in 7-day-old rat pups (n = 17). MRI was performed 1, 3, 7, 14 and 21 days after HII with intraperitoneal injection of HMON. Relative contrast values in the injured hemisphere and mean apparent diffusion coefficient values were calculated at each time point. Apoptosis and reactive astrogliosis were detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling (TUNEL) and glial fibrillary acidic protein staining, and the distribution and intensity of immunohistochemical staining were directly compared with those of HMON enhancement on MRI.

RESULTS

The dorsolateral thalamus, hippocampus and remaining cortex of the injured hemisphere showed HMON enhancement from 3 to 21 days after HII. The mean relative contrast values in the dorsolateral thalamus showed an increase from a negative value at 1 day to 16.5 ± 4.8% at 21 days. The apoptotic cells and reactive astrocytes were observed on immunohistochemical staining from 1 to 21 days after HII. The accumulation of apoptotic cells regionally matched with the areas of HMON enhancement, while that of reactive astrocytes did not.

CONCLUSION

The areas of HMON enhancement showed best spatial agreement with those of apoptosis on TUNEL staining. Both HMON enhancement and TUNEL-positive cells were observed up to 21 days after HII. Advances in knowledge: The strength of our study is the visualization of apoptotic area in vivo using HMON-enhanced MRI, and we also showed that HII has a prolonged evolution lasting for several weeks.

Perinatal neuroprotection update

Antepartum, intrapartum, and neonatal events can result in a spectrum of long-term neurological sequelae, including cerebral palsy, cognitive delay, schizophrenia, and autism spectrum disorders [1]. Advances in obstetrical and neonatal care have led to survival at earlier gestational ages and consequently increasing numbers of periviable infants who are at significant risk for long-term neurological deficits. Therefore, efforts to decrease and prevent cerebral insults attempt not only to decrease preterm delivery but also to improve neurological outcomes in infants delivered preterm. We recently published a comprehensive review addressing the impacts of magnesium sulfate, therapeutic hypothermia, delayed cord clamping, infections, and prevention of preterm delivery on the modification of neurological risk [2]. In this review, we will briefly provide updates to the aforementioned topics as well as an expansion on avoidance of toxin and infections, specifically the Zika virus.

Erythropoietin Restores Long-Term Neurocognitive Function Involving Mechanisms of Neuronal Plasticity in a Model of Hyperoxia-Induced Preterm Brain Injury

Cerebral white and grey matter injury is the leading cause of an adverse neurodevelopmental outcome in prematurely born infants. High oxygen concentrations have been shown to contribute to the pathogenesis of neonatal brain damage. Here, we focused on motor-cognitive outcome up to the adolescent and adult age in an experimental model of preterm brain injury. In search of the putative mechanisms of action we evaluated oligodendrocyte degeneration, myelination, and modulation of synaptic plasticity-related molecules. A single dose of erythropoietin (20,000 IU/kg) at the onset of hyperoxia (24 hours, 80% oxygen) in 6-day-old Wistar rats improved long-lasting neurocognitive development up to the adolescent and adult stage. Analysis of white matter structures revealed a reduction of acute oligodendrocyte degeneration. However, erythropoietin did not influence hypomyelination occurring a few days after injury or long-term microstructural white matter abnormalities detected in adult animals. Erythropoietin administration reverted hyperoxia-induced reduction of neuronal plasticity-related mRNA expression up to four months after injury. Thus, our findings highlight the importance of erythropoietin as a neuroregenerative treatment option in neonatal brain injury, leading to improved memory function in adolescent and adult rats which may be linked to increased neuronal network connectivity.

High-Dose Erythropoietin and Hypothermia for Hypoxic-Ischemic Encephalopathy: A Phase II Trial

OBJECTIVE

To determine if multiple doses of erythropoietin (Epo) administered with hypothermia improve neuroradiographic and short-term outcomes of newborns with hypoxic-ischemic encephalopathy.

METHODS

In a phase II double-blinded, placebo-controlled trial, we randomized newborns to receive Epo (1000 U/kg intravenously; n = 24) or placebo (n = 26) at 1, 2, 3, 5, and 7 days of age. All infants had moderate/severe encephalopathy; perinatal depression (10 minute Apgar <5, pH <7.00 or base deficit ≥15, or resuscitation at 10 minutes); and received hypothermia. Primary outcome was neurodevelopment at 12 months assessed by the Alberta Infant Motor Scale and Warner Initial Developmental Evaluation. Two independent observers rated MRI brain injury severity by using an established scoring system.

RESULTS

The mean age at first study drug was 16.5 hours (SD, 5.9). Neonatal deaths did not significantly differ between Epo and placebo groups (8% vs 19%, P = .42). Brain MRI at mean 5.1 days (SD, 2.3) showed a lower global brain injury score in Epo-treated infants (median, 2 vs 11, P = .01). Moderate/severe brain injury (4% vs 44%, P = .002), subcortical (30% vs 68%, P = .02), and cerebellar injury (0% vs 20%, P = .05) were less frequent in the Epo than placebo group. At mean age 12.7 months (SD, 0.9), motor performance in Epo-treated (n = 21) versus placebo-treated (n = 20) infants were as follows: Alberta Infant Motor Scale (53.2 vs 42.8, P = .03); Warner Initial Developmental Evaluation (28.6 vs 23.8, P = .05).

CONCLUSIONS

High doses of Epo given with hypothermia for hypoxic-ischemic encephalopathy may result in less MRI brain injury and improved 1-year motor function.

Delayed erythropoietin therapy improves histological and behavioral outcomes after transient neonatal stroke

BACKGROUND AND PURPOSE

Stroke is a major cause of neonatal morbidity, often with delayed diagnosis and with no accepted therapeutic options. The purpose of this study is to investigate the efficacy of delayed initiation of multiple dose erythropoietin (EPO) therapy in improving histological and behavioral outcomes after early transient ischemic stroke.

METHODS

32 postnatal day 10 (P10) Sprague-Dawley rats underwent sham surgery or transient middle cerebral artery occlusion (tMCAO) for 3h, resulting in injury involving the striatum and parieto-temporal cortex. EPO (1000U/kg per dose×3 doses) or vehicle was administered intraperitoneally starting one week after tMCAO (at P17, P20, and P23). At four weeks after tMCAO, sensorimotor function was assessed in these four groups (6 vehicle-sham, 6 EPO-sham, 10 vehicle-tMCAO and 10 EPO-tMCAO) with forepaw preference in cylinder rearing trials. Brains were then harvested for hemispheric volume and Western blot analysis.

RESULTS

EPO-tMCAO animals had significant improvement in forepaw symmetry in cylinder rearing trials compared to vehicle-tMCAO animals, and did not differ from sham animals. There was also significant preservation of hemispheric brain volume in EPO-tMCAO compared to vehicle-tMCAO animals. No differences in ongoing cell death at P17 or P24 were noted by spectrin cleavage in either EPO-tMCAO or vehicle-tMCAO groups.

CONCLUSIONS

These results suggest that delayed EPO therapy improves both behavioral and histological outcomes at one month following transient neonatal stroke, and may provide a late treatment alternative for early brain injury.

Activation of migration of endogenous stem cells by erythropoietin as potential rescue for neurodegenerative diseases

Neurodegenerative disorders such as Alzheimer's disease (AD) are characterized by progressive cognitive dysfunction and memory loss. There is deposition of amyloid plaques in the brain and subsequent neuronal loss. Neuroinflammation plays a key role in the pathogenesis of AD. There is still no effective curative therapy for these patients. One promising strategy involves the stimulation of endogenous stem cells. This study investigated the therapeutic effect of erythropoietin (EPO) in neurogenesis, and proved its manipulation of the endogenous mesenchymal stem cells in model of lipopolysaccharide (LPS)-induced neuroinflammation.

METHODS

Forty five adult male mice were divided equally into 3 groups: Group I (control), group II (LPS untreated group): mice were injected with single dose of lipopolysaccharide (LPS) 0.8 mg/kg intraperitoneally (ip) to induce neuroinflammation, group III (EPO treated group): in addition to (LPS) mice were further injected with EPO in dose of 40 μg/kg of body weight three times weekly for 5 consecutive weeks. Groups were tested for their locomotor activity and memory using open field test and Y-maze. Cerebral specimens were subjected to histological and morphometric studies. Glial fibrillary acidic protein (GFAP) and mesenchymal stem cell marker CD44 were assessed using immunostaining. Gene expression of brain derived neurotrophic factor (BDNF) was examined in brain tissue.

RESULTS

LPS decreased locomotor activity and percentage of correct choices in Y-maze test. Cerebral sections of LPS treated mice showed increased percentage area of dark nuclei and amyloid plaques. Multiple GFAP positive astrocytes were detected in affected cerebral sections. In addition, decrease BDNF gene expression was noted. On the other hand, EPO treated group, showed improvement in locomotor and cognitive function. Examination of the cerebral sections showed multiple neurons exhibiting less dark nuclei and less amyloid plaques in comparison to the untreated group. GFAP positive astrocytes were also reduced. Cerebral sections of the EPO treated group showed multiple branched and spindle CD44 positive cells inside and around blood vessels more than in LPS group. This immunostaining was negative in the control group. EPO administration increased BDNF gene expression.

CONCLUSION

This study proved that EPO provides excellent neuroprotective and neurotrophic effects in vivo model of LPS induced neuroinflammation. It enhances brain tissue regeneration via stimulation of endogenous mesenchymal stem cells proliferation and their migration to the site of inflammation. EPO also up regulates cerebral BDNF expression and production, which might contributes to EPO mediated neurogenesis. It also attenuates reactive gliosis thus reduces neuroinflammation. These encouraging results obtained with the use of EPO proved that it may be a promising candidate for future clinical application and treatment of neurodegenerative diseases.

Impaired oligodendrocyte maturation in preterm infants: Potential therapeutic targets

Preterm birth is an evolving challenge in neonatal health care. Despite declining mortality rates among extremely premature neonates, morbidity rates remain very high. Currently, perinatal diffuse white matter injury (WMI) is the most commonly observed type of brain injury in preterm infants and has become an important research area. Diffuse WMI is associated with impaired cognitive, sensory and psychological functioning and is increasingly being recognized as a risk factor for autism-spectrum disorders, ADHD, and other psychological disturbances. No treatment options are currently available for diffuse WMI and the underlying pathophysiological mechanisms are far from being completely understood. Preterm birth is associated with maternal inflammation, perinatal infections and disrupted oxygen supply which can affect the cerebral microenvironment by causing activation of microglia, astrogliosis, excitotoxicity, and oxidative stress. This intricate interplay of events negatively influences oligodendrocyte development, causing arrested oligodendrocyte maturation or oligodendrocyte cell death, which ultimately results in myelination failure in the developing white matter. This review discusses the current state in perinatal WMI research, ranging from a clinical perspective to basic molecular pathophysiology. The complex regulation of oligodendrocyte development in healthy and pathological conditions is described, with a specific focus on signaling cascades that may play a role in WMI. Furthermore, emerging concepts in the field of WMI and issues regarding currently available animal models are put forward. Novel insights into the molecular mechanisms underlying impeded oligodendrocyte maturation in diffuse WMI may aid the development of novel treatment options which are desperately needed to improve the quality-of-life of preterm neonates.

Neuroprotective potential of erythropoietin in neonates; design of a randomized trial

Background

In 2013, nearly four million babies were born in the U.S., among whom 447,875 were born preterm. Approximately 30,000 of these infants were born before 28 weeks of gestation. These infants, termed Extremely Low Gestational Age Neonates (ELGANs), experience high morbidity and mortality despite modern therapies: approximately 20 % of ELGANs admitted to an NICU die before discharge, 20 % of survivors have severe, and 20 % moderate neurodevelopmental impairment (NDI). New approaches are needed to improve neonatal outcomes. Recombinant erythropoietin (Epo) is a promising neuroprotective agent that is widely available, affordable, and has been used safely in neonates to stimulate erythropoiesis. There are extensive preclinical data to support its use as a neuroprotective intervention: Epo promotes normal brain maturation by increasing neurogenesis, angiogenesis, and by protecting oligodendrocytes. Epo also decreases acute brain injury following hypoxia ischemia by decreasing inflammation, oxidative and excitotoxic injury, resulting in decreased apoptosis. Despite the availability of both preclinical and safety data there has not been a definitive clinical evaluation of the benefit of Epo, and a large phase III trial is necessary to provide evidence to support potential changes in practice guidelines.

Findings

We first review the preclinical data motivating further clinical trials, and then describe in detail the design of the PENUT study (Preterm Epo Neuroprotection). PENUT is a phase III study evaluating the effect of neonatal Epo treatment on the combined outcome of death or severe NDI among ELGANS. 940 subjects will be randomized to determine: 1) whether Epo decreases the combined outcome of death or NDI at 22–26 months corrected age; 2) the safety of high dose Epo administration to ELGANs; 3) whether Epo treatment decreases serial measures of circulating inflammatory mediators, and improves biomarkers of brain injury; and 4) whether Epo treatment improves brain structure at 36 weeks postmenstrual age as measured by MRI.

Conclusions

Epo neuroprotection is an exciting new approach to preterm neuroprotection, and if efficacious, will provide a much-needed therapy for this group of vulnerable infants.

New horizons for newborn brain protection: enhancing endogenous neuroprotection

Intrapartum-related events are the third leading cause of childhood mortality worldwide and result in one million neurodisabled survivors each year. Infants exposed to a perinatal insult typically present with neonatal encephalopathy (NE). The contribution of pure hypoxia-ischaemia (HI) to NE has been debated; over the last decade, the sensitising effect of inflammation in the aetiology of NE and neurodisability is recognised. Therapeutic hypothermia is standard care for NE in high-income countries; however, its benefit in encephalopathic babies with sepsis or in those born following chorioamnionitis is unclear. It is now recognised that the phases of brain injury extend into a tertiary phase, which lasts for weeks to years after the initial insult and opens up new possibilities for therapy.There has been a recent focus on understanding endogenous neuroprotection and how to boost it or to supplement its effectors therapeutically once damage to the brain has occurred as in NE. In this review, we focus on strategies that can augment the body's own endogenous neuroprotection. We discuss in particular remote ischaemic postconditioning whereby endogenous brain tolerance can be activated through hypoxia/reperfusion stimuli started immediately after the index hypoxic-ischaemic insult. Therapeutic hypothermia, melatonin, erythropoietin and cannabinoids are examples of ways we can supplement the endogenous response to HI to obtain its full neuroprotective potential. Achieving the correct balance of interventions at the correct time in relation to the nature and stage of injury will be a significant challenge in the next decade.

Mechanisms of cell-cell interaction in oligodendrogenesis and remyelination after stroke

White matter damage is a clinically important aspect of several central nervous system diseases, including stroke. Cerebral white matter primarily consists of axonal bundles ensheathed with myelin secreted by mature oligodendrocytes, which play an important role in neurotransmission between different areas of gray matter. During the acute phase of stroke, damage to oligodendrocytes leads to white matter dysfunction through the loss of myelin. On the contrary, during the chronic phase, white matter components promote an environment, which is favorable for neural repair, vascular remodeling, and remyelination. For effective remyelination to take place, oligodendrocyte precursor cells (OPCs) play critical roles by proliferating and differentiating into mature oligodendrocytes, which help to decrease the burden of axonal injury. Notably, other types of cells contribute to these OPC responses under the ischemic conditions. This mini-review summarizes the non-cell autonomous mechanisms in oligodendrogenesis and remyelination after white matter damage, focusing on how OPCs receive support from their neighboring cells. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Neuroprotective agents for neonatal hypoxic-ischemic brain injury

Hypoxic-ischemic (H-I) brain injury in newborns is a major cause of morbidity and mortality that claims thousands of lives each year. In this review, we summarize the promising neuroprotective agents tested on animal models and pilot clinical studies of neonatal H-I brain injury according to the different phases of the disease. These agents target various phases of injury including the early phase of excitotoxicity, oxidative stress and apoptosis as well as late-phase inflammatory reaction and neural repair. We analyze the cell survival and cell death pathways modified by these agents in neonatal H-I brain injury. We aim to 'build a bridge' between animal trials of neuroprotective agents and potential candidate treatments for future clinical applications against H-I encephalopathy.

Growth factors for the treatment of ischemic brain injury (growth factor treatment)

In recent years, growth factor therapy has emerged as a potential treatment for ischemic brain injury. The efficacy of therapies that either directly introduce or stimulate local production of growth factors and their receptors in damaged brain tissue has been tested in a multitude of models for different Central Nervous System (CNS) diseases. These growth factors include erythropoietin (EPO), vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and insulin-like growth factor (IGF-1), among others. Despite the promise shown in animal models, the particular growth factors that should be used to maximize both brain protection and repair, and the therapeutic critical period, are not well defined. We will review current pre-clinical and clinical evidence for growth factor therapies in treating different causes of brain injury, as well as issues to be addressed prior to application in humans.

Endothelial progenitor cells in ischemic stroke: an exploration from hypothesis to therapy

As the population ages and lifestyles change in concordance, the number of patients suffering from ischemic stroke and its associated disabilities is increasing. Studies on determining the relationship between endothelial progenitor cells (EPCs) and ischemic stroke have become a new hot spot and have reported that EPCs may protect the brain against ischemic injury, promote neurovascular repair, and improve long-term neurobehavioral outcomes. More importantly, they introduce a new perspective for prognosis assessment and therapy of ischemic stroke. However, EPCs’ origin, function, influence factors, injury repair mechanisms, and cell-based therapy strategies remain controversial. Particularly, research conducted to date has less clinical studies than pre-clinical experiments on animals. In this review, we summarized and analyzed the current understanding of basic characteristics, influence factors, functions, therapeutic strategies, and disadvantages of EPCs as well as the regulation of inflammatory factors involved in the function and survival of EPCs after ischemic stroke. Identifying potential therapeutic effects of EPCs in ischemic stroke will be a challenging but an incredibly important breakthrough in neurology, which may bring promise for patients with ischemic stroke.

The role of inflammation in perinatal brain injury

Inflammation is increasingly recognized as being a critical contributor to both normal development and injury outcome in the immature brain. The focus of this Review is to highlight important differences in innate and adaptive immunity in immature versus adult brain, which support the notion that the consequences of inflammation will be entirely different depending on context and stage of CNS development. Perinatal brain injury can result from neonatal encephalopathy and perinatal arterial ischaemic stroke, usually at term, but also in preterm infants. Inflammation occurs before, during and after brain injury at term, and modulates vulnerability to and development of brain injury. Preterm birth, on the other hand, is often a result of exposure to inflammation at a very early developmental phase, which affects the brain not only during fetal life, but also over a protracted period of postnatal life in a neonatal intensive care setting, influencing critical phases of myelination and cortical plasticity. Neuroinflammation during the perinatal period can increase the risk of neurological and neuropsychiatric disease throughout childhood and adulthood, and is, therefore, of concern to the broader group of physicians who care for these individuals.

Erythropoietin: a novel therapy for hypoxic-ischaemic encephalopathy?

Perinatal hypoxic-ischaemic encephalopathy (HIE) occurs in 1 to 3 per 1000 term births. HIE is not preventable in most cases, and therapies are limited. Hypothermia improves outcomes and is the current standard of care. Yet, clinical trials suggest that 44-53% of infants who receive hypothermia will die or suffer moderate to severe neurological disability. In this article, we review the preclinical and clinical evidence for erythropoietin (EPO) as a potential novel neuroprotective agent for the treatment of HIE. EPO is a novel neuroprotective agent, with remarkable neuroprotective and neuroregenerative effects in animals. Rodent and primate models of neonatal brain injury support the safety and efficacy of multiple EPO doses for improving histological and functional outcomes after hypoxia-ischaemia. Small clinical trials of EPO in neonates with HIE have also provided evidence supporting safety and preliminary efficacy in humans. There is currently insufficient evidence to support the use of high-dose EPO in newborns with HIE. However, several on-going trials will provide much needed data regarding the safety and efficacy of this potential new therapy when given in conjunction with hypothermia for HIE. Novel neuroprotective therapies are needed to further reduce the rate and severity of neurodevelopmental disabilities resulting from HIE. High-dose EPO is a promising therapy that can be administered in conjunction with hypothermia. However, additional data are needed to determine the safety and efficacy of this adjuvant therapy for HIE.

Nitric Oxide Pathway and Proliferation of Neural Progenitors in the Neonatal Rat

Several lines of evidence demonstrate that inhaled nitric oxide (iNO) not only acts locally on the pulmonary vasculature but also has remote effects on the mature and developing brain under basal or pathological conditions by modulating cerebral blood flow and microvascularization, white matter maturation, inflammation, and subsequent brain repair. Previously, consistent studies demonstrated that increased levels of guanosine 3',5' cyclic monophosphate (cGMP), the main effector of biological effect induced by nitric oxide (NO), significantly augment proliferation and neuronal differentiation of adult neural progenitor cells (NPCs). In the present study, we ask the question whether iNO could promote the proliferation of NPCs in the uninjured developing brain. We first reported that iNO exposure at a concentration of 20 ppm during the first 7 days of life was associated with a significant but transient elevation of brain cGMP concentration 2 h after the onset of iNO exposure and a subsequent increase in myelin content of the developing white matter at postnatal day (P) 10. Using BrDu labelling and colabelling with specific cell-type markers we found that iNO exposure of rat pups results in an increased NPC proliferation in several layers of the subventricular zone (SVZ) at both early (30 h) and late (P7) time points. These proliferating NPCs were found to be sustainably viable and subsequently differentiated into oligodendroglial cells in the developing white matter and cortex. We also found that NG2 immunoreactivity around vessel walls, labeling pericyte cells, was increased in NO-exposed rat pups in the periventricular SVZ. In conclusion, iNO appears to act on oligodendrocyte progenitor cells, leading to increased density of mature oligodendrocytes and myelin content in the immature rat brain.

Tract-based spatial statistics to assess the neuroprotective effect of early erythropoietin on white matter development in preterm infants

Despite improved survival, many preterm infants undergo subsequent neurodevelopmental impairment. To date, no neuroprotective therapies have been implemented into clinical practice. Erythropoietin, a haematopoietic cytokine used for treatment of anaemia of prematurity, has been shown to have neuroprotective and neuroregenerative effects on the brain in many experimental studies. The aim of the study was to assess the effect of recombinant human erythropoietin on the microstructural development of the cerebral white matter using tract-based spatial statistics performed at term equivalent age. A randomized, double-blind placebo-controlled, prospective multicentre study applying recombinant human erythropoietin in the first 42 h after preterm birth entitled 'Does erythropoietin improve outcome in preterm infant' was conducted in Switzerland (NCT00413946). Preterm infants were given recombinant human erythropoietin (3000 IU) or an equivalent volume of placebo (NaCl 0.9%) intravenously before 3 h of age after birth, at 12-18 h and at 36-42 h after birth. High resolution diffusion tensor imaging was obtained at 3 T in 58 preterm infants with mean (standard deviation) gestational age at birth 29.75 (1.44) weeks, and at scanning at 41.1 (2.09) weeks. Imaging was performed at a single centre. Voxel-wise statistical analysis of the fractional anisotropy data was carried out using tract-based spatial statistics to test for differences in fractional anisotropy between infants treated with recombinant human erythropoietin and placebo using a general linear model, covarying for the gestational age at birth and the corrected gestational age at the time of the scan. Preterm infants treated with recombinant human erythropoietin demonstrated increased fractional anisotropy in the genu and splenium of the corpus callosum, the anterior and posterior limbs of the internal capsule, and the corticospinal tract bilaterally. Mean fractional anisotropy was significantly higher in preterm infants treated with recombinant human erythropoietin than in those treated with placebo (P < 0.001). We conclude that early recombinant human erythropoietin administration improves white matter development in preterm infants assessed by diffusion tensor imaging and tract-based spatial statistics.

Perinatal arterial ischemic stroke: presentation, risk factors, evaluation, and outcome

BACKGROUND

Perinatal arterial ischemic stroke is as common as large vessel arterial ischemic stroke in adults and leads to significant morbidity. Perinatal arterial ischemic stroke is the most common identifiable cause of cerebral palsy and can lead to cognitive and behavioral difficulties that are amortized over a lifetime.

METHODS

The literature on perinatal arterial ischemic stroke was reviewed and analyzed.

RESULTS

Risk factors for perinatal arterial ischemic stroke include those that are maternal, neonatal, and placental. The most common clinical signs at presentation are seizures and hemiparesis. Evaluation should begin with thorough history acquisition and physical examination followed by magnetic resonance imaging of the brain, with consideration of magnetic resonance angiography of the head and neck, echocardiogram, and thrombophilia evaluation. Treatment beginning early to include physical, speech, and occupational therapies including constraint-induced movement therapy and close cognitive and developmental follow-up may be beneficial. Future treatments may include transcranial magnetic stimulation, hypothermia, and erythropoietin.

CONCLUSIONS

Perinatal arterial ischemic stroke comprises a group of arterial ischemic injuries that can occur in the prenatal, perinatal, and postnatal periods in term and preterm infants with different types of perinatal arterial ischemic stroke having different clinical presentations, risk factors, and long-term outcomes.

Barrier mechanisms in neonatal stroke

Clinical data continue to reveal that the incidence of perinatal stroke is high, similar to that in the elderly. Perinatal stroke leads to significant morbidity and severe long-term neurological and cognitive deficits, including cerebral palsy. Experimental models of cerebral ischemia in neonatal rodents have shown that the pathophysiology of perinatal brain damage is multifactorial. Cerebral vasculature undergoes substantial structural and functional changes during early postnatal brain development. Thus, the state of the vasculature could affect susceptibility of the neonatal brain to cerebral ischemia. In this review, we discuss some of the most recent findings regarding the neurovascular responses of the immature brain to focal arterial stroke in relation to neuroinflammation. We also discuss a possible role of the neonatal blood-CSF barrier in modulating inflammation and the long-term effects of early neurovascular integrity after neonatal stroke on angiogenesis and neurogenesis.

Erythropoietin and hypothermia for hypoxic-ischemic encephalopathy

BACKGROUND

Erythropoietin is neuroprotective in animal models of neonatal hypoxic-ischemic encephalopathy. We previously reported a phase I safety and pharmacokinetic study of erythropoietin in neonates. This article presents the neurodevelopmental follow-up of infants who were enrolled in the phase I clinical trial.

METHODS

We enrolled 24 newborns with hypoxic-ischemic encephalopathy in a dose-escalation study. Patients received up to six doses of erythropoietin in addition to hypothermia. All infants underwent neonatal brain magnetic resonance imaging (MRI) reviewed by a single neuroradiologist. Moderate-to-severe neurodevelopmental disability was defined as cerebral palsy with Gross Motor Function Classification System levels III-V or cognitive impairment based on Bayley Scales of Infant Development II mental developmental index or Bayley III cognitive composite score.

RESULTS

Outcomes were available for 22 of 24 infants, at mean age 22 months (range, 8-34 months). There were no deaths. Eight (36%) had moderate-to-severe brain injury on neonatal MRI. Moderate-to-severe disability occurred in one child (4.5%), in the setting of moderate-to-severe basal ganglia and/or thalamic injury. Seven infants with moderate-to-severe watershed injury exhibited the following outcomes: normal (three), mild language delay (two), mild hemiplegic cerebral palsy (one), and epilepsy (one). All 11 patients with a normal brain MRI had a normal outcome.

CONCLUSIONS

This study is the first to describe neurodevelopmental outcomes in infants who received high doses of erythropoietin and hypothermia during the neonatal period. The findings suggest that future studies are warranted to assess the efficacy of this new potential neuroprotective therapy.

Evidence That Erythropoietin Modulates Neuroinflammation through Differential Action on Neurons, Astrocytes, and Microglia

Neuroinflammation is a normal and healthy response to neuronal damage. However, excessive or chronic neuroinflammation exacerbates neurodegeneration after trauma and in progressive diseases such as Alzheimer’s, Parkinson’s, age-related macular degeneration, and glaucoma. Therefore, molecules that modulate neuroinflammation are candidates as neuroprotective agents. Erythropoietin (EPO) is a known neuroprotective agent that indirectly attenuates neuroinflammation, in part, by inhibiting neuronal apoptosis. In this review, we provide evidence that EPO also modulates neuroinflammation upstream of apoptosis by acting directly on glia. Further, the signaling induced by EPO may differ depending on cell type and context possibly as a result of activation of different receptors. While significant progress has been made in our understanding of EPO signaling, this review also identifies areas for future study in terms of the role of EPO in modulating neuroinflammation.

Erythropoietin: emerging role of erythropoietin in neonatal neuroprotection

BACKGROUND

In the last two decades, there has been considerable evolution in understanding the role of erythropoietin in neuroprotection. Erythropoietin has both paracrine and autocrine functions in the brain. Erythropoietin binding results in neurogenesis, oligodendrogenesis, and angiogenesis. Erythropoietin and its receptor are upregulated by exposure to hypoxia and proinflammatory cytokines after brain injury. While erythropoietin aids in recovery of locally injured neuronal cells, it provides negative feedback to glial cells in the penumbra, thereby limiting extension of injury. This forms the rationale for use of recombinant erythropoietin and erythropoietin mimetics in neonatal and adult injury models of stroke, traumatic brain injury, spinal cord injury, intracerebral hemorrhage, and neonatal hypoxic ischemia.

METHOD

Review of published literature (Pubmed, Medline, and Google scholar).

RESULTS

Preclinical neuroprotective data are reviewed, and the rationale for proceeding to clinical trials is discussed. Results from phase I/II trials are presented, as are updates on ongoing and upcoming clinical trials of erythropoietin neuroprotection in neonatal populations.

CONCLUSIONS

The scientific rationale and preclinical data for erythropoietin neuroprotection are promising. Phase II and III clinical trials are currently in process to determine the safety and efficacy of neuroprotective dosing of erythropoietin for extreme prematurity and hypoxic-ischemic encephalopathy in neonates.

Increased oligodendrogenesis by humanin promotes axonal remyelination and neurological recovery in hypoxic/ischemic brains

Oligodendrocytes are the predominant cell type in white matter and are highly vulnerable to ischemic injury. The role of oligodendrocyte dysfunction in ischemic brain injury is unknown. In this study, we used a 24-amino acid peptide S14G-Humanin (HNG) to examine oligodendrogenesis and neurological functional recovery in a hypoxic/ischemic (H/I) neonatal model. Intraperitoneal HNG pre-treatment decreased infarct volume following H/I injury. Delayed HNG treatment 24 h after H/I injury did not reduce infarct volume but did decrease neurological deficits and brain atrophy. Delayed HNG treatment did not attenuate axonal demyelination at 48 h after H/I injury. However, at 14 d after H/I injury, delayed HNG treatment increased axonal remyelination, the thickness of corpus callosum at the midline, the number of Olig2(+) /BrdU(+) cells, and levels of brain-derived neurotrophic factor (BDNF). Our results suggest that targeting oligodendrogenesis via delayed HNG treatment may represent a promising approach for the treatment of stroke.

Endogenous neurogenesis following ischaemic brain injury: insights for therapeutic strategies

Ischaemic stroke is among the most common yet most intractable types of central nervous system (CNS) injury in the adult human population. In the acute stages of disease, neurons in the ischaemic lesion rapidly die and other neuronal populations in the ischaemic penumbra are vulnerable to secondary injury. Multiple parallel approaches are being investigated to develop neuroprotective, reparative and regenerative strategies for the treatment of stroke. Accumulating evidence indicates that cerebral ischaemia initiates an endogenous regenerative response within the adult brain that potentiates adult neurogenesis from populations of neural stem and progenitor cells. A major research focus has been to understand the cellular and molecular mechanisms that underlie the potentiation of adult neurogenesis and to appreciate how interventions designed to modulate these processes could enhance neural regeneration in the post-ischaemic brain. In this review, we highlight recent advances over the last 5 years that help unravel the cellular and molecular mechanisms that potentiate endogenous neurogenesis following cerebral ischaemia and are dissecting the functional importance of this regenerative mechanism following brain injury. This article is part of a Directed Issue entitled: Regenerative Medicine: the challenge of translation.

HIF prolyl hydroxylase inhibition prior to transient focal cerebral ischaemia is neuroprotective in mice

This study investigated the effects of 2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetic acid (IOX3), a selective small molecule inhibitor of hypoxia-inducible factor (HIF) prolyl hydroxylases, on mouse brains subject to transient focal cerebral ischaemia. Male, 8- to 12-week-old C57/B6 mice were subjected to 45 min of middle cerebral artery occlusion (MCAO) either immediately or 24 h after receiving IOX3. Mice receiving IOX3 at 20 mg/kg 24 h prior to the MCAO had better neuroscores and smaller blood-brain barrier (BBB) disruption and infarct volumes than mice receiving the vehicle, whereas those having IOX3 at 60 mg/kg showed no significant changes. IOX3 treatment immediately before MCAO was not neuroprotective. IOX3 up-regulated HIF-1α, and increased EPO expression in mouse brains. In an in vitro BBB model (RBE4 cell line), IOX3 up-regulated HIF-1α and delocalized ZO-1. Pre-treating IOX3 on RBE4 cells 24 h before oxygen-glucose deprivation had a protective effect on endothelial barrier preservation with ZO-1 being better localized, while immediate IOX3 treatment did not. Our study suggests that HIF stabilization with IOX3 before cerebral ischaemia is neuroprotective partially because of BBB protection, while immediate application could be detrimental. These results provide information for studies aimed at the therapeutic activation of HIF pathway for neurovascular protection from cerebral ischaemia. We show that IOX3, a selective small molecule (280.66 Da) HIF prolyl hydroxylase inhibitor, could up-regulate HIF-1α and increase erythropoietin expression in mice. We further demonstrate that HIF stabilization with IOX3 before cerebral ischaemia is neuroprotective partially because of blood-brain barrier (BBB) protection, while immediate application is detrimental both in vivo and in vitro. These findings provide new insights into the role of HIF stabilization in ischaemic stroke.

Mechanisms of perinatal arterial ischemic stroke

The incidence of perinatal stroke is high, similar to that in the elderly, and produces a significant morbidity and severe long-term neurologic and cognitive deficits, including cerebral palsy, epilepsy, neuropsychological impairments, and behavioral disorders. Emerging clinical data and data from experimental models of cerebral ischemia in neonatal rodents have shown that the pathophysiology of perinatal brain damage is multifactorial. These studies have revealed that, far from just being a smaller version of the adult brain, the neonatal brain is unique with a very particular and age-dependent responsiveness to hypoxia-ischemia and focal arterial stroke. In this review, we discuss fundamental clinical aspects of perinatal stroke as well as some of the most recent and relevant findings regarding the susceptibility of specific brain cell populations to injury, the dynamics and the mechanisms of neuronal cell death in injured neonates, the responses of neonatal blood-brain barrier to stroke in relation to systemic and local inflammation, and the long-term effects of stroke on angiogenesis and neurogenesis. Finally, we address translational strategies currently being considered for neonatal stroke as well as treatments that might effectively enhance repair later after injury.

Brain remodelling following endothelin-1 induced stroke in conscious rats

The extent of stroke damage in patients affects the range of subsequent pathophysiological responses that influence recovery. Here we investigate the effect of lesion size on development of new blood vessels as well as inflammation and scar formation and cellular responses within the subventricular zone (SVZ) following transient focal ischemia in rats (n = 34). Endothelin-1-induced stroke resulted in neurological deficits detected between 1 and 7 days (P<0.001), but significant recovery was observed beyond this time. MCID image analysis revealed varying degrees of damage in the ipsilateral cortex and striatum with infarct volumes ranging from 0.76–77 mm³ after 14 days, where larger infarct volumes correlated with greater functional deficits up to 7 days (r = 0.53, P<0.05). Point counting of blood vessels within consistent sample regions revealed that increased vessel numbers correlated significantly with larger infarct volumes 14 days post-stroke in the core cortical infarct (r = 0.81, P<0.0001), core striatal infarct (r = 0.91, P<0.005) and surrounding border zones (r = 0.66, P<0.005; and r = 0.73, P<0.05). Cell proliferation within the SVZ also increased with infarct size (P<0.01) with a greater number of Nestin/GFAP positive cells observed extending towards the border zone in rats with larger infarcts. Lesion size correlated with both increased microglia and astrocyte activation, with severely diffuse astrocyte transition, the formation of the glial scar being more pronounced in rats with larger infarcts. Thus stroke severity affects cell proliferation within the SVZ in response to injury, which may ultimately make a further contribution to glial scar formation, an important factor to consider when developing treatment strategies that promote neurogenesis.

Neuroprotective effects of erythropoiesis-stimulating agents in term and preterm neonates

PURPOSE OF REVIEW

The use of erythropoiesis-stimulating agents (ESAs) such as erythropoietin and darbepoetin in preterm and term infants has been studied for over 20 years. Recent investigations have explored the potential neuroprotective effects of ESAs. We review the recent clinical trials and experimental animal models that provide evidence in support of using ESA to improve the neurodevelopmental outcomes in term and preterm infants.

RECENT FINDINGS

Continued work using animal models have confirmed the neuroprotective properties of ESAs, including promotion of oligodendrocyte development in the face of neuronal injury. Clinical studies in term and preterm infants have reported the neuroprotective effects following ESA administration, and improved neurodevelopmental outcomes have been reported in the studies of preterm infants.

SUMMARY

ESAs show great promise in preventing and treating brain injury in term and preterm infants.

The rodent endovascular puncture model of subarachnoid hemorrhage: mechanisms of brain damage and therapeutic strategies

Subarachnoid hemorrhage (SAH) represents a considerable health problem. To date, limited therapeutic options are available. In order to develop effective therapeutic strategies for SAH, the mechanisms involved in SAH brain damage should be fully explored. Here we review the mechanisms of SAH brain damage induced by the experimental endovascular puncture model. We have included a description of similarities and distinctions between experimental SAH in animals and human SAH pathology. Moreover, several novel treatment options to diminish SAH brain damage are discussed.SAH is accompanied by cerebral inflammation as demonstrated by an influx of inflammatory cells into the cerebral parenchyma, upregulation of inflammatory transcriptional pathways and increased expression of cytokines and chemokines. Additionally, various cell death pathways including cerebral apoptosis, necrosis, necroptosis and autophagy are involved in neuronal damage caused by SAH.Treatment strategies aiming at inhibition of inflammatory or cell death pathways demonstrate the importance of these mechanisms for survival after experimental SAH. Moreover, neuroregenerative therapies using stem cells are discussed as a possible strategy to repair the brain after SAH since this therapy may extend the window of treatment considerably. We propose the endovascular puncture model as a suitable animal model which resembles the human pathology of SAH and which could be applied to investigate novel therapeutic therapies to combat this debilitating insult.