Oxygen, a Key Factor Regulating Cell Behavior during Neurogenesis and Cerebral Diseases

Shaping early neural development by timed elevated tissue oxygen tension: Insights from multiomic analysis on human cerebral organoids

Oxygen plays a critical role in early neural development in brains, particularly before establishment of complete vasculature; however, it has seldom been investigated due to technical limitations. This study uses an in vitro human cerebral organoid model with multiomic analysis, integrating advanced microscopies and single-cell RNA sequencing, to monitor tissue oxygen tension during neural development. Results reveal a key period between weeks 4 and 6 with elevated intra-organoid oxygen tension, altered energy homeostasis, and rapid neurogenesis within the organoids. The timed oxygen tension elevation can be suppressed by hypoxia treatment or silencing of neuroglobin gene. This study provides insights into the role of oxygen in early neurogenesis from functional, genotypic, phenotypic, and proteomic aspects. These findings highlight the significance of the timed tissue oxygen tension elevation in neurogenesis and provide insights into the role of neuroglobin in neural development, with potential implications for understanding neurodegenerative diseases and therapeutic strategies.

Unraveling pathogenesis and potential biomarkers for autism spectrum disorder associated with HIF1A pathway based on machine learning and experiment validation

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with a high social burden and limited treatments. Hypoxic condition of the brain is considered an important pathological mechanism of ASD. HIF1A is a key participant in brain hypoxia, but its contribution to the pathophysiological landscape of ASD remains unclear.

METHODS

ASD-related datasets were obtained from GEO database, and HIF1A-related genes from GeneCards. Co-expression module analysis identified module genes, which were intersected with HIF1A-related genes to identify common genes. Machine learning identified hub genes from intersection genes and PPI networks were constructed to explore relationships among hub and HIF1A. Single-cell RNA sequencing analyzed hub gene distribution across cell clusters. ASD mouse model was created by inducing maternal immune activation (MIA) with poly(I:C) injections, verified through behavioral tests. Validation of HIF1A pathway and hub genes was confirmed through Western Blot, qPCR, and immunofluorescence in ASD mice and microglia BV-2 cells.

RESULTS

Using CEMiTool and GeneCards, 45 genes associated with ASD and HIF1A pathway were identified. Machine learning identified CDKN1A, ETS2, LYN, and SLC16A3 as potential ASD diagnostic markers. Single-cell sequencing pinpointed activated microglia as key immune cells. Behavioral tests showed MIA offspring mice exhibited typical ASD-like behaviors. Immunofluorescence confirmed the activation of microglia and HIF1A pathway in frontal cortex of ASD mice. Additionally, IL-6 contributed to ASD by activating JUN/HIF1A pathway, affecting CDKN1A, LYN, and SLC16A3 expression in microglia.

CONCLUSIONS

HIF1A-related genes CDKN1A, ETS2, LYN, and SLC16A3 are strong diagnostic markers for ASD and the activation of IL-6/JUN/HIF1A pathway in microglia contributes to the pathogenesis of ASD.

Mechanisms of ozone-induced neurotoxicity in the development and progression of dementia: a brief review

Dementia encompasses a spectrum of neurodegenerative disorders significantly impacting global health, with environmental factors increasingly recognized as crucial in their etiology. Among these, ozone, has been identified as a potential exacerbator of neurodegenerative processes, particularly in Alzheimer's disease (AD). Ozone exposure induces the production of reactive oxygen species (ROS), which penetrate the BBB, leading to oxidative damage in neuronal cells. This oxidative stress is closely linked with mitochondrial dysfunction and lipid peroxidation, processes that are foundational to the pathology observed in dementia, such as neuronal death and protein aggregation. Furthermore, ozone triggers chronic neuroinflammation, exacerbating these neurodegenerative processes and perpetuating a cycle of CNS damage. Recent studies highlight the role of peripheral biomarkers like High Mobility Group Box 1 (HMGB1) and Triggering Receptor Expressed on Myeloid cells 2 (TREM2) in mediating ozone's effects. Disruption of these and other identified proteins by ozone exposure impairs microglial function and response to amyloid plaques, suggesting a novel pathway through which ozone may influence AD pathology via immune dysregulation. This review discusses the concept of a bidirectional lung-brain axis, illustrating that systemic responses to air pollutants like ozone may reflect and contribute to neurodegenerative processes in the CNS. By delineating these mechanisms, we emphasize the critical need for integrating environmental health management into strategies for the prevention and treatment of dementia.

3D-Bioprinted Co-Cultures of Glioblastoma Multiforme and Mesenchymal Stromal Cells Indicate a Role for Perivascular Niche Cells in Shaping Glioma Chemokine Microenvironment

3D bioprinting has become a valuable tool for studying the biology of solid tumors, including glioblastoma multiforme (GBM). Our analysis of publicly available bulk RNA and single-cell sequencing data has allowed us to define the chemotactic profile of GBM tumors and identify the cell types that secrete particular chemokines in the GBM tumor microenvironment (TME). Our findings indicate that primary GBM tissues express multiple chemokines, whereas spherical monocultures of GBM cells significantly lose this diversity. Subsequently, the comparative analysis of GBM spherical monocultures vs. 3D-bioprinted multicultures of cells showed a restoration of chemokine profile diversity in 3D-bioprinted cultures. Furthermore, single-cell RNA-Seq analysis showed that cells of the perivascular niche (pericytes and endocytes) express multiple chemokines in the GBM TME. Next, we 3D-bioprinted cells from two glioblastoma cell lines, U-251 and DK-MG, alone and as co-cultures with mesenchymal stromal cells (representing cells of the perivascular niche) and assessed the chemokine secretome. The results clearly demonstrated that the interaction of tumors and mesenchymal cells leads to in a significant increase in the repertoire and levels of secreted chemokines under culture in 21% O2 and 1% O2. Our study indicates that cells of the perivascular niche may perform a substantial role in shaping the chemokine microenvironment in GBM tumors.

Mdivi-1 alleviates ferroptosis induced by hypoxia combined with propofol in HT22 cells by inhibiting excessive mitophagy

BACKGROUND

Pediatric postoperative cognitive dysfunction (POCD) is a prevalent complication following anesthesia and surgery. Hypoxia and propofol are the primary risk factors contributing to pediatric POCD. Our previous in vivo animal research has demonstrated that cognitive dysfunction in immature Sprague-Dawley (SD) rats, induced by hypoxia combined with propofol (HCWP), is closely associated with hippocampal neuron ferroptosis.

METHODS AND RESULTS

In vivo transcriptome sequencing and KEGG functional analysis revealed significant enrichment of the mitophagy pathway. To further elucidate the relationship between mitophagy and ferroptosis, HT22 cells were selected to construct an in vitro HCWP model. Our findings indicate that HCWP activates excessive mitophagy in HT22 cells, leading to decreased mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) burst, mitochondrial fragmentation, and the induction of ferroptosis. To explore this causal relationship further, we employed Mdivi-1, a mitophagy inhibitor. Notably, low-dose Mdivi-1 (10 µM) effectively suppressed excessive mitophagy in HT22 cells, improved mitochondrial function and morphology, and mitigated markers associated with ferroptosis. The mechanism by which Mdivi-1 alleviates HCWP-induced ferroptosis in HT22 cells is likely due to its inhibition of excessive mitophagy, thereby promoting mitochondrial homeostasis.

CONCLUSIONS

Our study suggests that mitophagy may be an upstream event in HCWP-induced ferroptosis in HT22 cells. Consequently, targeted regulation of mitophagy by Mdivi-1 may represent a promising approach to prevent cognitive dysfunction following HCWP exposure.

Oxygen and HIF1α-dependent SDF1 expression in primary astrocytes

In the naturally hypoxic in utero fetal environment of preterm infants, oxygen and oxygen-sensitive signaling pathways play an important role in brain development, with hypoxia-inducible factor-1α (HIF1α) being an important regulator. Early exposure to nonphysiological high oxygen concentrations by birth in room can induce HIF1α degradation and may affect neuronal and glial development. This involves the dysregulation of astroglial maturation and function, which in turn might contribute to oxygen-induced brain injury. In this study, we investigated the effects of early high oxygen exposure on astroglial maturation and, specifically, on astroglial stromal cell-derived factor 1 (SDF1) expression in vivo and in vitro. In our neonatal mouse model of hyperoxia preterm birth brain injury in vivo, high oxygen exposure affected astroglial development and cortical SDF1 expression. These results were further supported by reduced Sdf1 expression, impaired proliferation, decreased total cell number, and altered expression of astroglial markers in astrocytes in primary cultures grown under high oxygen conditions. Moreover, to mimic the naturally hypoxic in utero fetal environment, astroglial Sdf1 expression was increased after low oxygen exposure in vitro, which appears to be regulated by HIF1α activity. Additionally, the knockdown of Hif1α revealed HIF1α-dependent Sdf1 expression in vitro. Our results indicate HIF1α and oxygen-dependent chemokine expression in primary astrocytes and highlight the importance of oxygen conditions for brain development.

Mitochondrial metabolism regulation and epigenetics in hypoxia

The complex and dynamic interaction between cellular energy control and gene expression modulation is shown by the intersection between mitochondrial metabolism and epigenetics in hypoxic environments. Poor oxygen delivery to tissues, or hypoxia, is a basic physiological stressor that sets off a series of reactions in cells to adapt and endure oxygen-starved environments. Often called the "powerhouse of the cell," mitochondria are essential to cellular metabolism, especially regarding producing energy through oxidative phosphorylation. The cellular response to hypoxia entails a change in mitochondrial metabolism to improve survival, including epigenetic modifications that control gene expression without altering the underlying genome. By altering the expression of genes involved in angiogenesis, cell survival, and metabolism, these epigenetic modifications help cells adapt to hypoxia. The sophisticated interplay between mitochondrial metabolism and epigenetics in hypoxia is highlighted by several important points, which have been summarized in the current article. Deciphering the relationship between mitochondrial metabolism and epigenetics during hypoxia is essential to understanding the molecular processes that regulate cellular adaptation to reduced oxygen concentrations.

The Role of Hyperbaric Oxygen Therapy in Neuroregeneration and Neuroprotection: A Review

Neurogenesis is a high energy-demanding process, which is why blood vessels are an active part of the neurogenic niche since they allow the much-needed oxygenation of progenitor cells. In this regard, although neglected for a long time, the "oxygen niche" should be considered an important intervenient in adult neurogenesis. One possible hypothesis for the failure of numerous neuroprotective trials is that they relied on compounds that target a highly specific neuroprotective pathway. This approach may be too limited, given the complexity of the processes that lead to cell death. Therefore, research should adopt a more multifactorial approach. Among the limited range of agents with multimodal neuromodulatory capabilities, hyperbaric oxygen therapy has demonstrated effectiveness in reducing secondary brain damage in various brain injury models. This therapy functions not only as a neuroprotective mechanism but also as a powerful neuroregenerative mechanism.

From Vessels to Neurons-The Role of Hypoxia Pathway Proteins in Embryonic Neurogenesis

Embryonic neurogenesis can be defined as a period of prenatal development during which divisions of neural stem and progenitor cells give rise to neurons. In the central nervous system of most mammals, including humans, the majority of neocortical neurogenesis occurs before birth. It is a highly spatiotemporally organized process whose perturbations lead to cortical malformations and dysfunctions underlying neurological and psychiatric pathologies, and in which oxygen availability plays a critical role. In case of deprived oxygen conditions, known as hypoxia, the hypoxia-inducible factor (HIF) signaling pathway is activated, resulting in the selective expression of a group of genes that regulate homeostatic adaptations, including cell differentiation and survival, metabolism and angiogenesis. While a physiological degree of hypoxia is essential for proper brain development, imbalanced oxygen levels can adversely affect this process, as observed in common obstetrical pathologies such as prematurity. This review comprehensively explores and discusses the current body of knowledge regarding the role of hypoxia and the HIF pathway in embryonic neurogenesis of the mammalian cortex. Additionally, it highlights existing gaps in our understanding, presents unanswered questions, and provides avenues for future research.

Value of brain tissue oxygen saturation in neonatal respiratory distress syndrome: a clinical study

Neonatal respiratory distress syndrome (NRDS) is one of the major causes of pre-term mortality and morbidity among very-low-birth-weight infants (VLBWI) in low- and middle-income countries (LMIC). Some of the neonates pass away despite admission and care in intensive care units (ICUs). The present clinical trial seeks the application value of elevating oxygen saturation in the brain cells of pre-term neonates born with NRDS. Near-infrared spectroscopy (NIRS) was used to monitor the neonates' microscopic cerebral oxygenation levels do determine hemoglobin concentration in brain tissues, whereas the pulse oximetry was used to measure oxygenation levels among the patients. In statistical analyses, the Analysis of Variance (ANOVA), and descriptive statistics was deployed in the Jupyter Notebook environment using Python language. High saturation of oxygen in the brain tissues result in important biological and physiological processes, including enhanced oxygen supply to cells, reduced severity of NRDS, and balancing oxygen demand and supply. The correlations of oxygen saturation with systemic saturation of oxygen, the saturation of oxygen in brain tissues, the association between brain-specific and systemic saturation, and the impact of these outcomes on clinical practices were deliberated. Also, the pH gas values, the saturation of oxygen in neonates' brain tissues, metabolic acidosis, the effect of acid-base balance and cerebral oxygen supply, and the oxygenation of brain tissues and the pH values emerged as important variables of oxygenation of brain tissues in pre-term neonates. Oxygen saturation in brain cells influence vital physiological and biological processes. Balancing acid-base saturation or levels is needed despite the challenging achievement. Oxygenation of brain tissues improve the brain's overall functioning.

Reactive Gliosis in Neonatal Disorders: Friend or Foe for Neuroregeneration?

A developing nervous system is particularly vulnerable to the influence of pathophysiological clues and injuries in the perinatal period. Astrocytes are among the first cells that react to insults against the nervous tissue, the presence of pathogens, misbalance of local tissue homeostasis, and a lack of oxygen and trophic support. Under this background, it remains uncertain if induced astrocyte activation, recognized as astrogliosis, is a friend or foe for progressing neonatal neurodevelopment. Likewise, the state of astrocyte reactivity is considered one of the key factors discriminating between either the initiation of endogenous reparative mechanisms compensating for aberrations in the structures and functions of nervous tissue or the triggering of neurodegeneration. The responses of activated cells are modulated by neighboring neural cells, which exhibit broad immunomodulatory and pro-regenerative properties by secreting a plethora of active compounds (including interleukins and chemokines, neurotrophins, reactive oxygen species, nitric oxide synthase and complement components), which are engaged in cell crosstalk in a paracrine manner. As the developing nervous system is extremely sensitive to the influence of signaling molecules, even subtle changes in the composition or concentration of the cellular secretome can have significant effects on the developing neonatal brain. Thus, modulating the activity of other types of cells and their interactions with overreactive astrocytes might be a promising strategy for controlling neonatal astrogliosis.

Fetal head-down posture may explain the rapid brain evolution in humans and other primates: An interpretative review

Evolutionary cerebrovascular consequences of upside-down postural verticality of the anthropoid fetus have been largely overlooked in the literature. This working hypothesis-based report provides a literature interpretation from an aspect that the rapid evolution of the human brain has been promoted by fetal head-down position due to maternal upright and semi-upright posture. Habitual vertical torso posture is a feature not only of humans, but also of monkeys and non-human apes that spend considerable time in a sitting position. Consequently, the head-down position of the fetus may have caused physiological craniovascular hypertension that stimulated expansion of the intracranial vessels and acted as an epigenetic physiological stress, which enhanced neurogenesis and eventually, along with other selective pressures, led to the progressive growth of the anthropoid brain and its organization. This article collaterally opens a new insight into the conundrum of high cephalopelvic proportions (i.e., the tight fit between the pelvic birth canal and fetal head) in phylogenetically distant lineages of monkeys, lesser apes, and humans. Low cephalopelvic proportions in non-human great apes could be accounted for by their energetically efficient horizontal nest-sleeping and consequently by their larger body mass compared to monkeys and lesser apes that sleep upright. One can further hypothesize that brain size varies in anthropoids according to the degree of exposure of the fetus to postural verticality. The supporting evidence for this postulation includes a finding that in fossil hominins cerebral blood flow rate increased faster than brain volume. This testable hypothesis opens a perspective for research on fetal postural cerebral hemodynamics.

Neuronal and tumourigenic boundaries of glioblastoma plasticity

Glioblastoma (GBM) remains the most lethal primary brain cancer largely due to recurrence of treatment-resistant disease. Current therapies are ultimately ineffective as GBM tumour cells adapt their identity to escape treatment. Recent advances in single-cell epigenetics and transcriptomics highlight heterogeneous cell populations in GBM tumours originating from unique cancerous genetic aberrations. However, they also suggest that tumour cells conserve molecular properties of parent neuronal cells, with their permissive epigenetic profiles enabling them to morph along a finite number of reprogramming routes to evade treatment. Here, we review the known tumourigenic, neurodevelopmental and brain-injury boundaries of GBM plasticity, and propose that effective treatment of GBM requires the addition of therapeutics that restrain GBM plasticity.

Neonatal Oxidative Stress Impairs Cortical Synapse Formation and GABA Homeostasis in Parvalbumin-Expressing Interneurons

Neonatal brain injury is often caused by preterm birth. Brain development is vulnerable to increased environmental stress, including oxidative stress challenges. Due to a premature change of the fetal living environment from low oxygen in utero into postnatal high-oxygen room air conditions ex utero, the immature preterm brain is exposed to a relative hyperoxia, which can induce oxidative stress and impair neuronal cell development. To simulate the drastic increase of oxygen exposure in the immature brain, 5-day-old C57BL/6 mice were exposed to hyperoxia (80% oxygen) for 48 hours or kept in room air (normoxia, 21% oxygen) and mice were analyzed for maturational alterations of cortical GABAergic interneurons. As a result, oxidative stress was indicated by elevated tyrosine nitration of proteins. We found perturbation of perineuronal net formation in line with decreased density of parvalbumin-expressing (PVALB) cortical interneurons in hyperoxic mice. Moreover, maturational deficits of cortical PVALB+ interneurons were obtained by decreased glutamate decarboxylase 67 (GAD67) protein expression in Western blot analysis and lower gamma-aminobutyric acid (GABA) fluorescence intensity in immunostaining. Hyperoxia-induced oxidative stress affected cortical synaptogenesis by decreasing synapsin 1, synapsin 2, and synaptophysin expression. Developmental delay of synaptic marker expression was demonstrated together with decreased PI3K-signaling as a pathway being involved in synaptogenesis. These results elucidate that neonatal oxidative stress caused by increased oxygen exposure can lead to GABAergic interneuron damage which may serve as an explanation for the high incidence of psychiatric and behavioral alterations found in preterm infants.

Biosensors to Monitor Cell Activity in 3D Hydrogel-Based Tissue Models

Three-dimensional (3D) culture models have gained relevant interest in tissue engineering and drug discovery owing to their suitability to reproduce in vitro some key aspects of human tissues and to provide predictive information for in vivo tests. In this context, the use of hydrogels as artificial extracellular matrices is of paramount relevance, since they allow closer recapitulation of (patho)physiological features of human tissues. However, most of the analyses aimed at characterizing these models are based on time-consuming and endpoint assays, which can provide only static and limited data on cellular behavior. On the other hand, biosensing systems could be adopted to measure on-line cellular activity, as currently performed in bi-dimensional, i.e., monolayer, cell culture systems; however, their translation and integration within 3D hydrogel-based systems is not straight forward, due to the geometry and materials properties of these advanced cell culturing approaches. Therefore, researchers have adopted different strategies, through the development of biochemical, electrochemical and optical sensors, but challenges still remain in employing these devices. In this review, after examining recent advances in adapting existing biosensors from traditional cell monolayers to polymeric 3D cells cultures, we will focus on novel designs and outcomes of a range of biosensors specifically developed to provide real-time analysis of hydrogel-based cultures.

Reproducibility of developmental neuroplasticity in in vitro brain tissue models

The current prevalence of neurodevelopmental, neurodegenerative diseases, stroke and brain injury stimulates studies aimed to identify new molecular targets, to select the drug candidates, to complete the whole set of preclinical and clinical trials, and to implement new drugs into routine neurological practice. Establishment of protocols based on microfluidics, blood-brain barrier- or neurovascular unit-on-chip, and microphysiological systems allowed improving the barrier characteristics and analyzing the regulation of local microcirculation, angiogenesis, and neurogenesis. Reconstruction of key mechanisms of brain development and even some aspects of experience-driven brain plasticity would be helpful in the establishment of brain in vitro models with the highest degree of reliability. Activity, metabolic status and expression pattern of cells within the models can be effectively assessed with the protocols of system biology, cell imaging, and functional cell analysis. The next generation of in vitro models should demonstrate high scalability, 3D or 4D complexity, possibility to be combined with other tissues or cell types within the microphysiological systems, compatibility with bio-inks or extracellular matrix-like materials, achievement of adequate vascularization, patient-specific characteristics, and opportunity to provide high-content screening. In this review, we will focus on currently available and prospective brain tissue in vitro models suitable for experimental and preclinical studies with the special focus on models enabling 4D reconstruction of brain tissue for the assessment of brain development, brain plasticity, and drug kinetics.

Characterization of Oxygen Levels in an Uninfected and Infected Human Blood-Cerebrospinal-Fluid-Barrier Model

The host–pathogen interaction during meningitis can be investigated with blood-cerebrospinal-fluid-barrier (BCSFB) cell culture models. They are commonly handled under atmospheric oxygen conditions (19–21% O₂), although the physiological oxygen conditions are significantly lower in cerebrospinal fluid (CSF) (7–8% O₂). We aimed to characterize oxygen levels in a Streptococcus (S.) suis-infected BCSFB model with transmigrating neutrophils. A BCSFB model with human choroid plexus epithelial cells growing on transwell-filters was used. The upper “blood”-compartment was infected and blood-derived neutrophils were added. S. suis and neutrophils transmigrated through the BCSFB into the “CSF”-compartment. Here, oxygen and pH values were determined with the non-invasive SensorDish^® reader. Slight orbital shaking improved the luminescence-based measurement technique for detecting free oxygen. In the non-infected BCSFB model, an oxygen value of 7% O₂ was determined. However, with S. suis and transmigrating neutrophils, the oxygen value significantly decreased to 2% O₂. The pH level decreased slightly in all groups. In conclusion, we characterized oxygen levels in the BCSFB model and demonstrated the oxygen consumption by cells and bacteria. Oxygen values in the non-infected BCSFB model are comparable to in vivo values determined in pigs in the CSF. Infection and transmigrating neutrophils decrease the oxygen value to lower values.

Non-invasive, non-pharmacological/bio-technological interventions towards neurorestoration upshot after ischemic stroke, in adults-systematic, synthetic, literature review

Considering its marked life-threatening and (not seldom: severe and/or permanent) disabling, potential, plus the overall medico-psycho-socio-economic tough burden it represents for the affected persons, their families and the community, the cerebrovascular accident (CVA)-including with the, by far more frequent, ischemic type-is subject to considerable scientific research efforts that aim (if possible) at eliminating the stroke induced lesions, and consist, as well, in ambitious-but still poorly transferable into medical practice-goals such as brain neuroregeneration and/or repair, within related corollary/upshot of neurorestoration. We have conducted, in this respect, a systematic and synthetic literature review, following the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)" concept. Accordingly, we have interrogated five internationally renowned medical data bases: Elsevier, NCBI/PubMed, NCBI/PMC, PEDro, and ISI Web of Knowledge/Science (the last one to check whether the initially identified articles are published in ISI indexed journals), based on a large (details in the body text) number of most appropriate, to our knowledge, key word combinations/"syntaxes"-used contextually-and subsequently fulfilling the related, on five steps, filtering/selection methodology. We have thereby selected 114 fully eligible (of which contributive: 83-see further) papers; at the same time, additionally, we have enhanced our documentation-basically, but not exclusively, for the introductive part of this work (see further)-with bibliographic resources, overall connected to our subject, identified in the literature within a non-standardized search. It appears that the opportunity window for morph-functional recovery after stroke is larger than previously thought, actually being considered that brain neurorestoration/repair could occur, and therefore be expected, in later stages than in earlier ones, although, in this context, the number of cases possibly benefitting (for instance after physical and/or cognitive rehabilitation-including with magnetic or direct current transcranial stimulation) is quite small and with more or less conflicting, related outcomes, in the literature. Moreover, applying especially high intense, solicitating, rehabilitation interventions, in early stages post (including ischemic) stroke could even worsen the functional evolution. Accordingly, for clarifications and validation of more unitary points of view, continuing and boosting research efforts in this complex, interdisciplinary domain, is necessary. Until finding (if ever) effective modalities to cure the lesions of the central nervous system (CNS)-including post ischemic stroke-it is reasonable and recommendable-based on rigorous methodologies-the avail of combined ways: physiatric, pharmacologic, possibly also bio-technologic. On a different note, but however connected to our subject: periodic related systematic, synthetic literature reviews reappraisals are warranted and welcome.

Intermittent hypoxia treatment alleviates memory impairment in the 6-month-old APPswe/PS1dE9 mice and reduces amyloid beta accumulation and inflammation in the brain

Background

Alzheimer’s disease (AD) is a progressive, degenerative, and terminal disease without cure. There is an urgent need for a new strategy to treat AD. The aim of this study was to investigate the effects of intermittent hypoxic treatment (IHT) on cognitive functions in a mouse model of AD and unravel the mechanism of action of IHT.

Methods

Six-month-old APPswe/PS1dE9 (APP/PS1) male mice were exposed to hypoxic environment (14.3% O₂) 4 h/day for 14 days or 28 days. Cognitive functions were measured by Morris water maze test after either 14 days or 42 days of interval. Thereafter the distribution of amyloid plaque and microglial activation were determined by mouse brain immunohistochemistry, while the amyloid beta (Aβ) and inflammatory cytokines were measured by ELISA and Western Blot. Microarray was used for studying gene expressions in the hippocampus.

Results

IHT for 14 days or 28 days significantly improved the spatial memory ability of the 6-month-old APP/PS1 mice. The memory improvement by 14 days IHT lasted to 14 days, but not to 42 days. The level of Aβ plaques and neurofilament accumulations was reduced markedly after the IHT exposure. IHT reduced the pro-inflammatory cytokines IL-1β, IL-6 levels, and β-secretase cleavage of APP processing which implies reduced Aβ production. Microarray analysis revealed a large number of genes in the hippocampus were significantly altered which are known to be metabolism-regulated genes.

Conclusions

This study provides evidence of the beneficial effect of IHT on the progression of AD by alleviating memory impairment, reducing Aβ accumulation and inflammation in the brain. IHT can be developed as a novel measure to relieve the progression of AD by targeting multiple pathways in the AD pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00935-z.

Reduction of cortical parvalbumin-expressing GABAergic interneurons in a rodent hyperoxia model of preterm birth brain injury with deficits in social behavior and cognition

The inhibitory GABAergic system in the brain is involved in the etiology of various psychiatric problems, including autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD) and others. These disorders are influenced not only by genetic but also by environmental factors, such as preterm birth, although the underlying mechanisms are not known. In a translational hyperoxia model, exposing mice pups at P5 to 80% oxygen for 48 h to mimic a steep rise of oxygen exposure caused by preterm birth from in utero into room air, we documented a persistent reduction of cortical mature parvalbumin-expressing interneurons until adulthood. Developmental delay of cortical myelin was observed, together with decreased expression of oligodendroglial glial cell-derived neurotrophic factor (GDNF), a factor involved in interneuronal development. Electrophysiological and morphological properties of remaining interneurons were unaffected. Behavioral deficits were observed for social interaction, learning and attention. These results demonstrate that neonatal oxidative stress can lead to decreased interneuron density and to psychiatric symptoms. The obtained cortical myelin deficit and decreased oligodendroglial GDNF expression indicate that an impaired oligodendroglial-interneuronal interplay contributes to interneuronal damage.

Structure and inhibition of Cryptococcus neoformans sterylglucosidase to develop antifungal agents

Pathogenic fungi exhibit a heavy burden on medical care and new therapies are needed. Here, we develop the fungal specific enzyme sterylglucosidase 1 (Sgl1) as a therapeutic target. Sgl1 converts the immunomodulatory glycolipid ergosterol 3β-D-glucoside to ergosterol and glucose. Previously, we found that genetic deletion of Sgl1 in the pathogenic fungus Cryptococcus neoformans (Cn) results in ergosterol 3β-D-glucoside accumulation, renders Cn non-pathogenic, and immunizes mice against secondary infections by wild-type Cn, even in condition of CD4+ T cell deficiency. Here, we disclose two distinct chemical classes that inhibit Sgl1 function in vitro and in Cn cells. Pharmacological inhibition of Sgl1 phenocopies a growth defect of the Cn Δsgl1 mutant and prevents dissemination of wild-type Cn to the brain in a mouse model of infection. Crystal structures of Sgl1 alone and with inhibitors explain Sgl1’s substrate specificity and enable the rational design of antifungal agents targeting Sgl1.

Sterylglucosidase 1 (Sgl1) is a virulence factor in Cryptococcus neoformans that modulates fungal pathogenesis and host response. Here, the authors characterize Sgl1 structurally, identify Sgl1 inhibitors, and demonstrate Sgl1 inhibition has efficacy in mouse models of infection.

Overview of therapeutic potentiality of Angelica sinensis for ischemic stroke

BACKGROUND

Ischemic stroke is a common cerebrovascular disease. Due to sudden interruption of blood flow by arterial thrombus, amounts of neurons in ischemic central and penumbral regions occur necrosis and apoptosis resulting in serious injury of neurological function. Chinese medicines have a great advantage in ischemic stroke treatment and recovery, especially Angelica sinensis.

PURPOSE

There are a large number of studies reported that Angelica injection and A. sinensis active compounds. We systematically reviewed the effects and mechanisms of A. sinensis in recent years according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statements, and excavated its therapeutic potentiality for exploring more effective and safe compounds for ischemic stroke precision treatment.

RESULTS

A. sinensis extracts and active compounds, such as Z-ligustilide, 3-n-Butylphthalide, and ferulic acid have significant effects of anti-inflammation, anti-oxidative stress, angiogenesis, neurogenesis, anti-platelet aggregation, anti-atherosclerosis, protection of vessels, which contributes to improvement of neurological function on ischemic stroke.

CONCLUSION

A. sinensis is a key agent for ischemic stroke treatment, and worth deeply excavating its therapeutic potentiality with the aid of pharmacological network, computer-aided drug design, artificial intelligence, big data and multi-scale modelling techniques.

Chronic Intermittent Hypobaric Hypoxia Restores Hippocampus Function and Rescues Cognitive Impairments in Chronic Epileptic Rats via Wnt/β-catenin Signaling

Epilepsy is a complex neurological disorder with frequent psychiatric, cognitive, and social comorbidities in addition to recurrent seizures. Cognitive impairment, one of the most common comorbidities, has severe adverse effects on quality of life. Chronic intermittent hypobaric hypoxia (CIHH) has demonstrated neuroprotective efficacy in several neurological disease models. In the present study, we examined the effects of CIHH on cognition and hippocampal function in chronic epileptic rats. CIHH treatment rescued deficits in spatial and object memory, hippocampal neurogenesis, and synaptic plasticity in pilocarpine-treated epileptic rats. The Wnt/β-catenin pathway has been implicated in neural stem cell proliferation and synapse development, and Wnt/β-catenin pathway inhibition effectively blocked the neurogenic effects of CIHH. Our findings indicate that CIHH rescues cognitive deficits in epileptic rats via Wnt/β-catenin pathway activation. This study establishes CIHH and Wnt/β-catenin pathway regulators as potential treatments for epilepsy- induced cognitive impairments.

HIFα Regulates Developmental Myelination Independent of Autocrine Wnt Signaling

The developing CNS is exposed to physiological hypoxia, under which hypoxia-inducible factor α (HIFα) is stabilized and plays a crucial role in regulating neural development. The cellular and molecular mechanisms of HIFα in developmental myelination remain incompletely understood. A previous concept proposes that HIFα regulates CNS developmental myelination by activating the autocrine Wnt/β-catenin signaling in oligodendrocyte progenitor cells (OPCs). Here, by analyzing a battery of genetic mice of both sexes, we presented in vivo evidence supporting an alternative understanding of oligodendroglial HIFα-regulated developmental myelination. At the cellular level, we found that HIFα was required for developmental myelination by transiently controlling upstream OPC differentiation but not downstream oligodendrocyte maturation and that HIFα dysregulation in OPCs but not oligodendrocytes disturbed normal developmental myelination. We demonstrated that HIFα played a minor, if any, role in regulating canonical Wnt signaling in the oligodendroglial lineage or in the CNS. At the molecular level, blocking autocrine Wnt signaling did not affect HIFα-regulated OPC differentiation and myelination. We further identified HIFα-Sox9 regulatory axis as an underlying molecular mechanism in HIFα-regulated OPC differentiation. Our findings support a concept shift in our mechanistic understanding of HIFα-regulated CNS myelination from the previous Wnt-dependent view to a Wnt-independent one and unveil a previously unappreciated HIFα-Sox9 pathway in regulating OPC differentiation.SIGNIFICANCE STATEMENT Promoting disturbed developmental myelination is a promising option in treating diffuse white matter injury, previously called periventricular leukomalacia, a major form of brain injury affecting premature infants. In the developing CNS, hypoxia-inducible factor α (HIFα) is a key regulator that adapts neural cells to physiological and pathologic hypoxic cues. The role and mechanism of HIFα in oligodendroglial myelination, which is severely disturbed in preterm infants affected with diffuse white matter injury, is incompletely understood. Our findings presented here represent a concept shift in our mechanistic understanding of HIFα-regulated developmental myelination and suggest the potential of intervening with an oligodendroglial HIFα-mediated signaling pathway to mitigate disturbed myelination in premature white matter injury.

Hypoxia-inducible factor-2α is crucial for proper brain development

Sufficient tissue oxygenation is required for regular brain function; thus oxygen supply must be tightly regulated to avoid hypoxia and irreversible cell damage. If hypoxia occurs the transcription factor complex hypoxia-inducible factor (HIF) will accumulate and coordinate adaptation of cells to hypoxia. However, even under atmospheric O₂ conditions stabilized HIF-2α protein was found in brains of adult mice. Mice with a neuro-specific knockout of Hif-2α showed a reduction of pyramidal neurons in the retrosplenial cortex (RSC), a brain region responsible for a range of cognitive functions, including memory and navigation. Accordingly, behavioral studies showed disturbed cognitive abilities in these mice. In search of the underlying mechanisms for the specific loss of pyramidal cells in the RSC, we found deficits in migration in neural stem cells from Hif-2α knockout mice due to altered expression patterns of genes highly associated with neuronal migration and positioning.

Functional hypoxia drives neuroplasticity and neurogenesis via brain erythropoietin

Erythropoietin (EPO), named after its role in hematopoiesis, is also expressed in mammalian brain. In clinical settings, recombinant EPO treatment has revealed a remarkable improvement of cognition, but underlying mechanisms have remained obscure. Here, we show with a novel line of reporter mice that cognitive challenge induces local/endogenous hypoxia in hippocampal pyramidal neurons, hence enhancing expression of EPO and EPO receptor (EPOR). High-dose EPO administration, amplifying auto/paracrine EPO/EPOR signaling, prompts the emergence of new CA1 neurons and enhanced dendritic spine densities. Single-cell sequencing reveals rapid increase in newly differentiating neurons. Importantly, improved performance on complex running wheels after EPO is imitated by exposure to mild exogenous/inspiratory hypoxia. All these effects depend on neuronal expression of the Epor gene. This suggests a model of neuroplasticity in form of a fundamental regulatory circle, in which neuronal networks—challenged by cognitive tasks—drift into transient hypoxia, thereby triggering neuronal EPO/EPOR expression.

EPO treatment improves cognition, but underlying mechanisms were unknown. Here the authors describe a regulatory loop in which brain networks challenged by cognitive tasks drift into functional hypoxia that drives—via neuronal EPO synthesis—neurodifferentiation and dendritic spine formation.

Chronic mild hypoxia promotes hippocampal neurogenesis involving Notch1 signaling in epileptic rats

Cognitive impairment is one of the most common and disabling co-morbidities of epilepsy. It is therefore imperative to find novel treatment approaches to rescue cognitive function among epilepsy patients. Adult neurogenesis is strongly implicated in cognitive function, and mild hypoxia is known to promote the proliferation and differentiation of both embryonic and adult neural stem cells (NSCs). In the present study, we investigated the effect of mild hypoxia on cognitive function and hippocampal neurogenesis of rats with pilocarpine-induced chronic epilepsy. Chronic epilepsy induced marked spatial learning and memory deficits in the Morris water maze that were rescued by consecutively 28 days mild hypoxia exposure (6 h/d at 3000 m altitude equivalent) during the chronic phase. Moreover, mild hypoxia reversed the suppression of hippocampal neurogenesis and the downregulation of NT-3 and BDNF expression in hippocampus and cortex of epileptic rats. Mild hypoxia in vitro also promoted hippocampus-derived NSC proliferation and neuronal differentiation. In addition, mild hypoxia enhanced Notch1 and Hes1 expression, suggesting that Notch1 signaling may be involved in neuroprotection of hypoxia. Our data may help to pave the way for identifying new therapeutic targets for rescuing cognition conflicts in epileptic patients by using hypoxia to promote hippocampus neurogenesis.

Every Breath You Take: Non-invasive Real-Time Oxygen Biosensing in Two- and Three-Dimensional Microfluidic Cell Models

Knowledge on the availability of dissolved oxygen inside microfluidic cell culture systems is vital for recreating physiological-relevant microenvironments and for providing reliable and reproducible measurement conditions. It is important to highlight that in vivo cells experience a diverse range of oxygen tensions depending on the resident tissue type, which can also be recreated in vitro using specialized cell culture instruments that regulate external oxygen concentrations. While cell-culture conditions can be readily adjusted using state-of-the-art incubators, the control of physiological-relevant microenvironments within the microfluidic chip, however, requires the integration of oxygen sensors. Although several sensing approaches have been reported to monitor oxygen levels in the presence of cell monolayers, oxygen demands of microfluidic three-dimensional (3D)-cell cultures and spatio-temporal variations of oxygen concentrations inside two-dimensional (2D) and 3D cell culture systems are still largely unknown. To gain a better understanding on available oxygen levels inside organ-on-a-chip systems, we have therefore developed two different microfluidic devices containing embedded sensor arrays to monitor local oxygen levels to investigate (i) oxygen consumption rates of 2D and 3D hydrogel-based cell cultures, (ii) the establishment of oxygen gradients within cell culture chambers, and (iii) influence of microfluidic material (e.g., gas tight vs. gas permeable), surface coatings, cell densities, and medium flow rate on the respiratory activities of four different cell types. We demonstrate how dynamic control of cyclic normoxic-hypoxic cell microenvironments can be readily accomplished using programmable flow profiles employing both gas-impermeable and gas-permeable microfluidic biochips.

Hypoxia-ischemia is not an antecedent of most preterm brain damage: the illusion of validity

Brain injury in preterm newborn infants is often attributed to hypoxia-ischemia even when neither hypoxia nor ischemia is documented, and many causative speculations are based on the same assumption. We review human and animal study contributions with their strengths and limitations, and conclude that - despite all the work done in human fetal neuropathology and developmental models in animals - the evidence remains unconvincing that hypoxemia, in the fetus or newborn infant, contributes appreciably to any encephalopathy of prematurity. Giving an inappropriate causal name to a disorder potentially limits the options for change, should our understanding of the etiologies advance. The only observationally-based title we think appropriate is 'encephalopathy of prematurity'. Future pathophysiological research should probably include appropriately designed epidemiology studies, highly active developmental processes, infection and other inflammatory stimuli, the immature immune system, long chain fatty acids and their transporters, and growth (neurotrophic) factors.

WHAT THIS PAPER ADDS

Fetal hypoxemia is rarely documented in brain injury studies. Animal studies fail to consider human-animal fetal anatomical differences. Putative treatments from animal models have not found clinical use. Observational studies constitute the only approach to etiological understanding. No convincing evidence yet that hypoxemia injures preterm brain. Encephalopathy of prematurity is preferable to hypoxia-ischemia as a term for this disorder. Encephalopathy of prematurity is preferable to hypoxia-ischemia as a term for this disorder.

Oxygen Levels Regulate the Development of Human Cortical Radial Glia Cells

The oxygen (O2) concentration is a vital parameter for controlling the survival, proliferation, and differentiation of neural stem cells. A prenatal reduction of O2 levels (hypoxia) often leads to cognitive and behavioral defects, attributable to altered neural development. In this study, we analyzed the effects of O2 levels on human cortical progenitors, the radial glia cells (RGCs), during active neurogenesis, corresponding to the second trimester of gestation. Small changes in O2 levels profoundly affected RGC survival, proliferation, and differentiation. Physiological hypoxia (3% O2) promoted neurogenesis, whereas anoxia (<1% O2) and severe hypoxia (1% O2) arrested the differentiation of human RGCs, mainly by altering the generation of glutamatergic neurons. The in vitro activation of Wnt-β-catenin signaling rescued the proliferation and neuronal differentiation of RGCs subjected to anoxia. Pathologic hypoxia (≤1% O2) also exerted negative effects on gliogenesis, by decreasing the number of O4+ preoligodendrocytes and increasing the number of reactive astrocytes derived from cortical RGCs. O2-dependent alterations in glutamatergic neurogenesis and oligodendrogenesis can lead to significant changes in cortical circuitry formation. A better understanding of the cellular effects caused by changes in O2 levels during human cortical development is essential to elucidating the etiology of numerous neurodevelopmental disorders.

Blocked, delayed, or obstructed: What causes poor white matter development in intrauterine growth restricted infants?

Poor white matter development in intrauterine growth restricted (IUGR) babies remains a major, untreated problem in neonatology. New therapies, guided by an understanding of the mechanisms that underlie normal and abnormal oligodendrocyte development and myelin formation, are required. Much of our knowledge of the mechanisms that underlie impaired myelination come from studies in adult demyelinating disease, preterm brain injury, or experimental models of hypoxia-ischemia. However, relatively less is known for IUGR which is surprising because IUGR is a leading cause of perinatal mortality and morbidity, second only to premature birth. IUGR is also a significant risk factor for the later development of cerebral palsy, and is a greater risk compared to some of the more traditionally researched antecedents - asphyxia and inflammation. Recent evidence suggests that the white matter injury and reduced myelination in the brains of some preterm babies is due to impaired maturation of oligodendrocytes thereby resulting in the reduced capacity to synthesize myelin. Therefore, it is not surprising that the hypomyelination observable in the central nervous system of IUGR infants has similarly lead to investigations identifying a delay or blockade in the progress of maturation of oligodendrocytes in these infants. This review will discuss current ideas thought to account for the poor myelination often present in the neonate's brain following IUGR, and discuss novel interventions that are promising as treatments that promote oligodendrocyte maturation, and thereby repair the myelination deficits that otherwise persist into infancy and childhood and lead to neurodevelopmental abnormalities.

A longitudinal study of cerebral blood flow under hypoxia at high altitude using 3D pseudo-continuous arterial spin labeling

Changes in cerebral blood flow (CBF) may occur with acute exposure to high altitude; however, the CBF of the brain parenchyma has not been studied to date. In this study, identical magnetic resonance scans using arterial spin labeling (ASL) were performed to study the haemodynamic changes at both sea level and high altitude. We found that with acute exposure to high altitude, the CBF in acute mountain sickness (AMS) subjects was higher (P < 0.05), while the CBF of non-AMS subjects was lower (P > 0.05) compared with those at sea level. Moreover, magnetic resonance angiography in both AMS and non-AMS subjects showed a significant increase in the cross-sectional areas of the internal carotid, basilar, and middle cerebral arteries on the first day at high altitude. These findings support that AMS may be related to increased CBF rather than vasodilation; these results contradict most previous studies that reported no relationship between CBF changes and the occurrence of AMS. This discrepancy may be attributed to the use of ASL for CBF measurement at both sea level and high altitude in this study, which has substantial advantages over transcranial Doppler for the assessment of CBF.

Strategies to Enhance Implantation and Survival of Stem Cells After Their Injection in Ischemic Neural Tissue

High post-transplantation cell mortality is the main limitation of various approaches that are aimed at improving regeneration of injured neural tissue by an injection of neural stem cells (NSCs) and mesenchymal stromal cells (MStroCs) in and/or around the lesion. Therefore, it is of paramount importance to identify efficient ways to increase cell transplant viability. We have previously proposed the "evolutionary stem cell paradigm," which explains the association between stem cell anaerobic/microaerophilic metabolic set-up and stem cell self-renewal and inhibition of differentiation. Applying these principles, we have identified the main critical point in the collection and preparation of these cells for experimental therapy: exposure of the cells to atmospheric O₂, that is, to oxygen concentrations that are several times higher than the physiologically relevant ones. In this way, the primitive anaerobic cells become either inactivated or adapted, through commitment and differentiation, to highly aerobic conditions (20%-21% O₂ in atmospheric air). This inadvertently compromises the cells' survival once they are transplanted into normal tissue, especially in the hypoxic/anoxic/ischemic environment, which is typical of central nervous system (CNS) lesions. In addition to the findings suggesting that stem cells can shift to glycolysis and can proliferate in anoxia, recent studies also propose that stem cells may be able to proliferate in completely anaerobic or ischemic conditions by relying on anaerobic mitochondrial respiration. In this systematic review, we propose strategies to enhance the survival of NSCs and MStroCs that are implanted in hypoxic/ischemic neural tissue by harnessing their anaerobic nature and maintaining as well as enhancing their anaerobic properties via appropriate ex vivo conditioning.

Elevated serum MDA and depleted non-enzymatic antioxidants, macro-minerals and trace elements are associated with bipolar disorder

Genetic and neurobiological factors are considered to be the major causes of mood and mental disorders. However, over the past few years, increased levels of serum malondialdehyde and altered levels of various non-enzymatic antioxidants and essential minerals involved in abnormal functional activity have been identified as major contributing factors to the pathogenesis of several neurological disorders. The aim of this study was to determine the levels of the serum lipid peroxidation product malondialdehyde (MDA), antioxidants (vitamin A, E and C), macro-minerals (calcium, potassium and sodium) and trace elements (zinc, iron and selenium) in patients with bipolar disorder and to explore their role in disease progression. This is a prospective case-control study that evaluated 55 patients with bipolar disorder and 55 healthy volunteers matched by age and sex. Serum MDA levels were determined by UV spectrophotometry as a marker of lipid peroxidation. RP-HPLC was employed to investigate the serum vitamin A and E concentrations, whereas UV spectrophotometry was used to quantify levels of vitamin C. Serum macro-minerals and trace elements were analyzed by atomic absorption spectroscopy (AAS). Statistical analysis was performed with independent sample t-tests and Pearson's correlation test. We found significantly higher concentrations of MDA (p<0.05) and significantly lower concentrations of antioxidants (vitamin A, E and C) (p<0.05) in the patient group compared with control group. Regarding trace elements and macro-minerals, lower concentrations of zinc, calcium, iron, selenium, sodium and potassium were found in the patient group compared with control subjects (p<0.05). Our study suggests that high serum MDA concentrations and low serum concentrations of antioxidants, macro-minerals and trace elements are strongly associated with bipolar disorder.

Bone Marrow Stromal Cells Combined With Sodium Ferulate and n-Butylidenephthalide Promote the Effect of Therapeutic Angiogenesis via Advancing Astrocyte-Derived Trophic Factors After Ischemic Stroke

Being a potential candidate for stroke treatment, bone marrow-derived mesenchymal stem/stromal cells (BM-MSCs) have been demonstrated to be able to enhance angiogenesis and proliferation of reactive astrocytes, which subsequently leads to the amelioration of neurological injury. Increasing evidence further indicates that combining BM-MSCs with certain agents, such as simvastatin, may improve therapeutic effects. Sodium ferulate (SF) and n-butylidenephthalide (BP), two main components of Radix Angelica Sinensis, are proven to be important regulators of stem cells in cell migration, differentiation, and pluripotency maintenance. This study aimed to investigate whether combining BM-MSCs with SF and BP had better therapeutic effect in the treatment of stroke, and the underlying molecular basis for the therapeutic effects was also investigated. The results showed that combination treatment notably reduced neurological injury after stroke and increased the expression of astrocyte-derived vascular endothelial growth factor (VEGF), brain-derived neurotrophic factor (BDNF), and von Willebrand factor-positive vascular density in the ischemic boundary zone as evaluated by immunofluorescence staining. After treatment with BM-MSCs plus SF and BP, astrocytes showed increased expression of VEGF and BDNF by upregulating protein kinase B/mammalian target of rapamycin (AKT/mTOR) expression in an oxygen- and glucose-deprived (OGD) environment. Human umbilical vein endothelial cells (HUVECs) incubated with the conditioned medium (CM) derived from OGD astrocytes treated with BM-MSCs plus SF and BP showed significantly increased migration and tube formation compared with those incubated with the CM derived from OGD astrocytes treated with BM-MSCs alone. These results demonstrate that combination treatment enhances the expression of astrocyte-derived VEGF and BDNF, which contribute to angiogenesis after cerebral ischemia, and the underlying mechanism is associated with activation of the astrocytic AKT/mTOR signaling pathway. Our study provides a potential therapeutic approach for ischemic stroke.

Sodium ferulate and n-butylidenephthalate combined with bone marrow stromal cells (BMSCs) improve the therapeutic effects of angiogenesis and neurogenesis after rat focal cerebral ischemia

BACKGROUND

Studies have indicated that bone marrow stromal cell (BMSC) administration is a promising approach for stroke treatment. For our study, we chose sodium ferulate (SF) and n-butylidenephthalide (BP) combined with BMSC, and observed if the combination treatment possessed more significant effects on angiogenesis and neurogenesis post-stroke.

METHODS

We established rat permanent middle cerebral artery occlusion (MCAo) model and evaluated ischemic volumes of MCAo, BMSC, SF + BP, Simvastatin + BMSC and SF + BP + BMSC groups with TTC staining on the 7th day after ischemia. Immunofluorescence staining of vascular endothelial growth factor (VEGF) and brain derived neurotrophic factor (BDNF), as well as immunohistochemistry staining of von Willebrand factor (vWF) and neuronal class III β-tubulin (Tuj1) were performed in ischemic boundary zone (IBZ), furthermore, to understand the mechanism, western blot was used to investigate AKT/mammalian target of rapamycin (mTOR) signal pathway in ischemic cortex. We also tested BMSC derived-VEGF and BDNF expressions by western blot assay in vitro.

RESULTS

SF + BP + BMSC group obviously decreased infarction zone, and elevated the expression of VEGF and the density and perimeter of vWF-vessels as same as Simvastatin + BMSC administration; moreover, its effects on BDNF and Tuj1 expressions were superior to Simvastatin + BMSC treatment in IBZ. Meanwhile, it showed that SF and BP combined with BMSC treatment notably up-regulated AKT/mTOR signal pathway compared with SF + BP group and BMSC alone post-stroke. Western blot results showed that SF and BP treatment could promote BMSCs to synthesize VEGF and BDNF in vitro.

CONCLUSIONS

We firstly demonstrate that SF and BP combined with BMSC can significantly improve angiogenesis and neurogenesis in IBZ following stroke. The therapeutic effects are associated with the enhancement of VEGF and BDNF expressions via activation of AKT/mTOR signal pathway. Furthermore, triggering BMSC paracrine function of SF and BP might contribute to amplifying the synergic effects of the combination treatment.

Redox-regulated fate of neural stem progenitor cells

BACKGROUND

Accumulated data indicate that self-renewal, multipotency, and differentiation of neural stem cells are under an intrinsic control mediated by alterations in the redox homeostasis. These dynamic redox changes not only reflect and support the ongoing metabolic and energetic processes, but also serve to coordinate redox-signaling cascades. Controlling particular redox couples seems to have a relevant impact on cell fate decision during development, adult neurogenesis and regeneration.

SCOPE OF REVIEW

Our own research provided initial evidence for the importance of NAD+-dependent enzymes in neural stem cell fate decision. In this review, we summarize recent knowledge on the active role of reactive oxygen species, redox couples and redox-signaling mechanisms on plasticity and function of neural stem and progenitor cells focusing on NAD(P)+/NAD(P)H-mediated processes.

MAJOR CONCLUSIONS

The compartmentalized subcellular sources and availability of oxidizing/reducing molecules in particular microenvironment define the specificity of redox regulation in modulating the delicate balance between stemness and differentiation of neural progenitors. The generalization of "reactive oxygen species" as well as the ambiguity of their origin might explain the diametrically-opposed findings in the field of redox-dependent cell fate reflected by the literature.

GENERAL SIGNIFICANCE

Increasing knowledge of temporary and spatially defined redox regulation is of high relevance for the development of novel approaches in the field of cell-based regeneration of nervous tissue in various pathological states. This article is part of a special issue entitled Redox regulation of differentiation and de-differentiation.

Fibroblast growth factor and endothelin-1 receptors mediate the response of human striatal precursor cells to hypoxia

Fetal striatal transplantation has emerged as a new therapeutic strategy in Huntington's disease (HD). Hypoxia is one of the microenvironmental stress conditions to which fetal tissue is exposed as soon as it is isolated and transplanted into the diseased host brain. Mechanisms that support neuroblast survival and replenishment of damaged cells within the HD brain in the hypoxic condition have yet to be fully elucidated. This study is aimed at investigating the molecular pathways associated with the hypoxic condition in human fetal striatal neuroblasts (human striatal precursor (HSP) cells), using the hypoxia-mimetic agent cobalt chloride (CoCl2). We analyzed the effect of CoCl2 on HSP cell proliferation and on the expression of hypoxia-related proteins, such as hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF). Moreover, we evaluated fibroblast growth factor 2 (FGF2; 50ng/ml) and endothelin-1 (ET-1; 100nM) proliferative/survival effects in HSP cells in normoxic and hypoxic conditions. Dose-response experiments using increasing concentrations of CoCl2 (50-750μM) showed that the HSP cell growth was unaffected after 24h, while it increased at 48h, with the maximal effect observed at 400μM. In contrast, cell survival was impaired at 72h. Hypoxic conditions determined HIF-1α protein accumulation and increased gene and protein expression of VEGF, while FGF2 and ET-1 significantly stimulated HSP cell proliferation both in normoxic and hypoxic conditions, thus counteracting the apoptotic CoCl2 effect at 72h. The incubation with selective receptor (FGFR1, endothelin receptor A (ETA) and endothelin receptor B (ETB)) inhibitors abolished the FGF2 and ET-1 neuroprotective effect. In particular, ET-1 stimulated HSP cell survival through ETA in normoxic conditions and through ETB during hypoxia. Accordingly, ETA expression was down-regulated, while ETB expression was up-regulated by CoCl2 treatment. Overall, our results support the idea that HSP cells possess the machinery for their adaptation to hypoxic conditions and that neurotrophic factors, such as FGF2 and ET-1, may sustain neurogenesis and long-term survival through complex receptor-mediated mechanisms.

Absorbable magnesium-based stent: physiological factors to consider for in vitro degradation assessments

Absorbable metals have been widely tested in various in vitro settings using cells to evaluate their possible suitability as an implant material. However, there exists a gap between in vivo and in vitro test results for absorbable materials. A lot of traditional in vitro assessments for permanent materials are no longer applicable to absorbable metallic implants. A key step is to identify and test the relevant microenvironment and parameters in test systems, which should be adapted according to the specific application. New test methods are necessary to reduce the difference between in vivo and in vitro test results and provide more accurate information to better understand absorbable metallic implants. In this investigative review, we strive to summarize the latest test methods for characterizing absorbable magnesium-based stent for bioabsorption/biodegradation behavior in the mimicking vascular environments. Also, this article comprehensively discusses the direction of test standardization for absorbable stents to paint a more accurate picture of the in vivo condition around implants to determine the most important parameters and their dynamic interactions.

Hypoxic conditioned medium from rat cerebral cortical cells enhances the proliferation and differentiation of neural stem cells mainly through PI3-K/Akt pathways

Purpose

To investigate the effects of hypoxic conditioned media from rat cerebral cortical cells on the proliferation and differentiation of neural stem cells (NSCs) in vitro, and to study the roles of PI3-K/Akt and JNK signal transduction pathways in these processes.

Methods

Cerebral cortical cells from neonatal Sprague–Dawley rat were cultured under hypoxic and normoxic conditions; the supernatant was collected and named ‘hypoxic conditioned medium’ (HCM) and ‘normoxic conditioned medium’ (NCM), respectively. We detected the protein levels (by ELISA) of VEGF and BDNF in the conditioned media and mRNA levels (by RT-PCR) in cerebral cortical cells. The proliferation (number and size of neurospheres) and differentiation (proportion of neurons and astrocytes over total cells) of NSCs was assessed. LY294002 and SP600125, inhibitors of PI3-K/Akt and JNK, respectively, were applied, and the phosphorylation levels of PI3-K, Akt and JNK were measured by western blot.

Results

The protein levels and mRNA expressions of VEGF and BDNF in 4% HCM and 1% HCM were both higher than that of those in NCM. The efficiency and speed of NSCs proliferation was enhanced in 4% HCM compared with 1% HCM. The highest percentage of neurons and lowest percentage of astrocytes was found in 4% HCM. However, the enhancement of NSCs proliferation and differentiation into neurons accelerated by 4% HCM was inhibited by LY294002 and SP600125, with LY294002 having a stronger inhibitory effect. The increased phosphorylation levels of PI3-K, Akt and JNK in 4% HCM were blocked by LY294002 and SP600125.

Conclusions

4%HCM could promote NSCs proliferation and differentiation into high percentage of neurons, these processes may be mainly through PI3-K/Akt pathways.

Wnt pathway activation increases hypoxia tolerance during development

Adaptation to hypoxia, defined as a condition of inadequate oxygen supply, has enabled humans to successfully colonize high altitude regions. The mechanisms attempted by organisms to cope with short-term hypoxia include increased ATP production via anaerobic respiration and stabilization of Hypoxia Inducible Factor 1α (HIF-1α). However, less is known about the means through which populations adapt to chronic hypoxia during the process of development within a life time or over generations. Here we show that signaling via the highly conserved Wnt pathway impacts the ability of Drosophila melanogaster to complete its life cycle under hypoxia. We identify this pathway through analyses of genome sequencing and gene expression of a Drosophila melanogaster population adapted over >180 generations to tolerate a concentration of 3.5-4% O2 in air. We then show that genetic activation of the Wnt canonical pathway leads to increased rates of adult eclosion in low O2. Our results indicate that a previously unsuspected major developmental pathway, Wnt, plays a significant role in hypoxia tolerance.

Repetitive long-term hyperbaric oxygen treatment (HBOT) administered after experimental traumatic brain injury in rats induces significant remyelination and a recovery of sensorimotor function

Cells in the central nervous system rely almost exclusively on aerobic metabolism. Oxygen deprivation, such as injury-associated ischemia, results in detrimental apoptotic and necrotic cell loss. There is evidence that repetitive hyperbaric oxygen therapy (HBOT) improves outcomes in traumatic brain-injured patients. However, there are no experimental studies investigating the mechanism of repetitive long-term HBOT treatment-associated protective effects. We have therefore analysed the effect of long-term repetitive HBOT treatment on brain trauma-associated cerebral modulations using the lateral fluid percussion model for rats. Trauma-associated neurological impairment regressed significantly in the group of HBO-treated animals within three weeks post trauma. Evaluation of somatosensory-evoked potentials indicated a possible remyelination of neurons in the injured hemisphere following HBOT. This presumption was confirmed by a pronounced increase in myelin basic protein isoforms, PLP expression as well as an increase in myelin following three weeks of repetitive HBO treatment. Our results indicate that protective long-term HBOT effects following brain injury is mediated by a pronounced remyelination in the ipsilateral injured cortex as substantiated by the associated recovery of sensorimotor function.

Chronic hypoxia induces the activation of the Wnt/β-catenin signaling pathway and stimulates hippocampal neurogenesis in wild-type and APPswe-PS1ΔE9 transgenic mice in vivo

Hypoxia modulates proliferation and differentiation of cultured embryonic and adult stem cells, an effect that includes β-catenin, a key component of the canonical Wnt signaling pathway. Here we studied the effect of mild hypoxia on the activity of the Wnt/β-catenin signaling pathway in the hippocampus of adult mice in vivo. The hypoxia-inducible transcription factor-1α (HIF-1α) was analyzed as a molecular control of the physiological hypoxic response. Exposure to chronic hypoxia (10% oxygen for 6–72 h) stimulated the activation of the Wnt/β-catenin signaling pathway. Because the Wnt/β-catenin pathway is a positive modulator of adult neurogenesis, we evaluated whether chronic hypoxia was able to stimulate neurogenesis in the subgranular zone (SGZ) of the hippocampal dentate gyrus. Results indicate that hypoxia increased cell proliferation and neurogenesis in adult wild-type mice as determined by Ki67 staining, Bromodeoxyuridine (BrdU) incorporation and double labeling with doublecortin (DCX). Chronic hypoxia also induced neurogenesis in a double transgenic APPswe-PS1ΔE9 mouse model of Alzheimer’s disease (AD), which shows decreased levels of neurogenesis in the SGZ. Our results show for the first time that exposure to hypoxia in vivo can induce the activation of the Wnt/β-catenin signaling cascade in the hippocampus, suggesting that mild hypoxia may have a therapeutic value in neurodegenerative disorders associated with altered Wnt signaling in the brain and also in pathological conditions in which hippocampal neurogenesis is impaired.

Focal necrosis and disturbed myelination in the white matter of newborn infants: a tale of too much or too little oxygen

White matter disease in preterm infants comes along with focal destructions or with diffuse myelination disturbance. Recent experimental work with transgenic mice paves the way for a unifying molecular model for both types of brain injury, placing oxygen sensing by oligodendrocyte precursor cells (OPCs) at the center stage. Mice genetically altered to mimic high local oxygen tension in oligodendroglia lineage cells (via deletion of hypoxia-inducible factor, HIF) develop white matter disease resembling cystic periventricular leukomalacia within the first 7 days of life. Mice in which local hypoxia is mimicked in oligodendroglial cells (via genetic inhibition of HIF decay) display arrested OPC maturation and subsequent hypomyelination, reminiscent of the diffuse white matter disease observed in preterm infants and infants with congenital heart disease. These recent experimental findings on oxygen sensing and myelination are awaiting integration into a clinical framework. Gene regulation in response to hyperoxia or hypoxia, rather than oxidative stress, may be an important mechanism underlying neonatal white matter disease.

Magnesium degradation as determined by artificial neural networks

Magnesium degradation under physiological conditions is a highly complex process in which temperature, the use of cell culture growth medium and the presence of CO2, O2 and proteins can influence the corrosion rate and the composition of the resulting corrosion layer. Due to the complexity of this process it is almost impossible to predict the parameters that are most important and whether some parameters have a synergistic effect on the corrosion rate. Artificial neural networks are a mathematical tool that can be used to approximate and analyse non-linear problems with multiple inputs. In this work we present the first analysis of corrosion data obtained using this method, which reveals that CO2 and the composition of the buffer system play a crucial role in the corrosion of magnesium, whereas O2, proteins and temperature play a less prominent role.

Ischemic preconditioning increased the intestinal stem cell activities in the intestinal crypts in mice

BACKGROUND

Ischemic preconditioning (IPC) can protect against ischemia-reperfusion injury in the small intestine. Because intestinal stem cells (ISCs) control the recovery and growth of intestinal villi, this study investigated whether IPC had any effects on the activity of ISCs.

MATERIALS AND METHODS

The small intestines of mice were treated with IPC, laparotomy only (sham), or no surgery. The crypt fractions were isolated and the characteristics of ISCs among various groups were compared. The regenerative ability and the number of organoids grown from various crypt fractions were compared. The expression of hypoxia-inducible factor-1α (HIF-1α) and the related proteins of the Wnt-/β-catenin pathway in the crypt fractions were studied.

RESULTS

The IPC group had higher messenger RNA levels of various stem cell markers than the sham group at days 1 and 2 after surgery. The IPC group exhibited greater regenerative activity and more crypt organoids than the sham group (P < 0.05). The expression of HIF-1α, β-catenin, and phosphoglycogen synthase kinase 3β was increased in the IPC-treated crypt fractions in vivo and cultured crypt organoid cells with deferoxamine-mimicked hypoxia in vitro.

CONCLUSIONS

IPC significantly upregulated the activity of ISCs, possibly through the HIF-1α response and Wnt-/β-catenin signaling pathway.