SCO-spondin knockout mice exhibit small brain ventricles and mild spine deformation

Reissner's fiber (RF) is an extracellular polymer comprising the large monomeric protein SCO-spondin (SSPO) secreted by the subcommissural organ (SCO) that extends through cerebrospinal fluid (CSF)-filled ventricles into the central canal of the spinal cord. In zebrafish, RF and CSF-contacting neurons (CSF-cNs) form an axial sensory system that detects spinal curvature, instructs morphogenesis of the body axis, and enables proper alignment of the spine. In mammalian models, RF has been implicated in CSF circulation. However, challenges in manipulating Sspo, an exceptionally large gene of 15,719 nucleotides, with traditional approaches has limited progress. Here, we generated a Sspo knockout mouse model using CRISPR/Cas9-mediated genome-editing. Sspo knockout mice lacked RF-positive material in the SCO and fibrillar condensates in the brain ventricles. Remarkably, Sspo knockout brain ventricle sizes were reduced compared to littermate controls. Minor defects in thoracic spine curvature were detected in Sspo knockouts, which did not alter basic motor behaviors tested. Altogether, our work in mouse demonstrates that SSPO and RF regulate ventricle size during development but only moderately impact spine geometry.

20-αHydroxycholesterol, an oxysterol in human breast milk, reverses mouse neonatal white matter injury through Gli-dependent oligodendrogenesis

White matter injuries (WMIs) are the leading cause of neurologic impairment in infants born premature. There are no treatment options available. The most common forms of WMIs in infants occur prior to the onset of normal myelination, making its pathophysiology distinctive, thus requiring a tailored approach to treatment. Neonates present a unique opportunity to repair WMIs due to a transient abundance of neural stem/progenitor cells (NSPCs) present in the germinal matrix with oligodendrogenic potential. We identified an endogenous oxysterol, 20-αHydroxycholesterol (20HC), in human maternal breast milk that induces oligodendrogenesis through a sonic hedgehog (shh), Gli-dependent mechanism. Following WMI in neonatal mice, injection of 20HC induced subventricular zone-derived oligodendrogenesis and improved myelination in the periventricular white matter, resulting in improved motor outcomes. Targeting the oligodendrogenic potential of postnatal NSPCs in neonates with WMIs may be further developed into a novel approach to mitigate this devastating complication of preterm birth.

Age-appropriate potassium clearance from perinatal cerebrospinal fluid depends on choroid plexus NKCC1

Regulation of the volume and electrolyte composition of the cerebrospinal fluid (CSF) is vital for brain development and function. The Na-K-Cl co-transporter NKCC1 in the choroid plexus (ChP) plays key roles in regulating CSF volume by co-transporting ions and mediating same-direction water movements. Our previous study showed ChP NKCC1 is highly phosphorylated in neonatal mice as the CSF K+ level drastically decreases and that overexpression of NKCC1 in the ChP accelerates CSF K+ clearance and reduces ventricle size [1]. These data suggest that NKCC1 mediates CSF K+ clearance following birth in mice. In this current study, we used CRISPR technology to create a conditional NKCC1 knockout mouse line and evaluated CSF K+ by Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). We demonstrated ChP-specific reduction of total and phosphorylated NKCC1 in neonatal mice following embryonic intraventricular delivery of Cre recombinase using AAV2/5. ChP-NKCC1 knockdown was accompanied by a delayed perinatal clearance of CSF K+. No gross morphological disruptions were observed in the cerebral cortex. We extended our previous results by showing embryonic and perinatal rats shared key characteristics with mice, including decreased ChP NKCC1 expression level, increased ChP NKCC1 phosphorylation state, and increased CSF K+ levels compared to adult. Collectively, these follow up data support ChP NKCC1's role in age-appropriate CSF K+ clearance during neonatal development.

Claudin-5a knockdown attenuates blood-neural barrier in zebrafish

Mammalian claudin-5 (cldn5), a zebrafish cldn5a homolog, is essential to blood-brain barrier (BBB) integrity. Previously, the existence of an endothelial tight junction-based BBB with cldn5a expression in the cerebral microvessels was reported in zebrafish. However, the role of cldn5a in the cerebral microvessels of developing zebrafish has not been elucidated. Here, we further investigated the functional integrity of cldn5a in developing zebrafish by injecting cldn5a morpholinos. At 7 days post-fertilization, cldn5a immunoreactivity was detected on the brain surface, ventricular ependyma, and cerebral mircovessels but disappeared following cldna5a knockdown. Cldn5a morphants showed size-selective leakage of tracers through the BBB and downregulated expression of glucose transporter 1 (glut1) in the cerebral microvessels. In addition, leakiness in the blood-cerebrospinal fluid barrier was observed, implying the overall abnormal development of blood-neural barriers. The results of our study suggest that cldn5a is required for building and maintaining the blood-neural barrier during zebrafish development.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Camel regulates development of the brain ventricular system

Development of the brain ventricular system of vertebrates and the molecular mechanisms involved are not fully understood. The developmental genes expressed in the elements of the brain ventricular system such as the ependyma and circumventricular organs act as molecular determinants of cell adhesion critical for the formation of brain ventricular system. They control brain development and function, including the flow of cerebrospinal fluid. Here, we describe the novel distantly related member of the zebrafish L1-CAM family of genes-camel. Whereas its maternal transcripts distributed uniformly, the zygotic transcripts demonstrate clearly defined expression patterns, in particular in the axial structures: floor plate, hypochord, and roof plate. camel expresses in several other cell lineages with access to the brain ventricular system, including the midbrain roof plate, subcommissural organ, organum vasculosum lamina terminalis, median eminence, paraventricular organ, flexural organ, and inter-rhombomeric boundaries. This expression pattern suggests a role of Camel in neural development. Several isoforms of Camel generated by differential splicing of exons encoding the sixth fibronectin type III domain enhance cell adhesion differentially. The antisense oligomer morpholino-mediated loss-of-function of Camel affects cell adhesion and causes hydrocephalus and scoliosis manifested via the tail curled down phenotype. The subcommissural organ's derivative-the Reissner fiber-participates in the flow of cerebrospinal fluid. The Reissner fiber fails to form upon morpholino-mediated Camel loss-of-function. The Camel mRNA-mediated gain-of-function causes the Reissner fiber misdirection. This study revealed a link between Chl1a/Camel and Reissner fiber formation, and this supports the idea that CHL1 is one of the scoliosis factors.

Exome sequencing implicates genetic disruption of prenatal neuro-gliogenesis in sporadic congenital hydrocephalus

Congenital hydrocephalus (CH), characterized by enlarged brain ventricles, is considered a disease of excessive cerebrospinal fluid (CSF) accumulation and thereby treated with neurosurgical CSF diversion with high morbidity and failure rates. The poor neurodevelopmental outcomes and persistence of ventriculomegaly in some post-surgical patients highlight our limited knowledge of disease mechanisms. Through whole-exome sequencing of 381 patients (232 trios) with sporadic, neurosurgically treated CH, we found that damaging de novo mutations account for >17% of cases, with five different genes exhibiting a significant de novo mutation burden. In all, rare, damaging mutations with large effect contributed to ~22% of sporadic CH cases. Multiple CH genes are key regulators of neural stem cell biology and converge in human transcriptional networks and cell types pertinent for fetal neuro-gliogenesis. These data implicate genetic disruption of early brain development, not impaired CSF dynamics, as the primary pathomechanism of a significant number of patients with sporadic CH.

The Lactate Receptor HCA1 Is Present in the Choroid Plexus, the Tela Choroidea, and the Neuroepithelial Lining of the Dorsal Part of the Third Ventricle

The volume, composition, and movement of the cerebrospinal fluid (CSF) are important for brain physiology, pathology, and diagnostics. Nevertheless, few studies have focused on the main structure that produces CSF, the choroid plexus (CP). Due to the presence of monocarboxylate transporters (MCTs) in the CP, changes in blood and brain lactate levels are reflected in the CSF. A lactate receptor, the hydroxycarboxylic acid receptor 1 (HCA1), is present in the brain, but whether it is located in the CP or in other periventricular structures has not been studied. Here, we investigated the distribution of HCA1 in the cerebral ventricular system using monomeric red fluorescent protein (mRFP)-HCA1 reporter mice. The reporter signal was only detected in the dorsal part of the third ventricle, where strong mRFP-HCA1 labeling was present in cells of the CP, the tela choroidea, and the neuroepithelial ventricular lining. Co-labeling experiments identified these cells as fibroblasts (in the CP, the tela choroidea, and the ventricle lining) and ependymal cells (in the tela choroidea and the ventricle lining). Our data suggest that the HCA1-containing fibroblasts and ependymal cells have the ability to respond to alterations in CSF lactate in body-brain signaling, but also as a sign of neuropathology (e.g., stroke and Alzheimer's disease biomarker).

Intrathecal drug delivery in the era of nanomedicine

Administration of substances directly into the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord is one approach that can circumvent the blood-brain barrier to enable drug delivery to the central nervous system (CNS). However, molecules that have been administered by intrathecal injection, which includes intraventricular, intracisternal, or lumbar locations, encounter new barriers within the subarachnoid space. These barriers include relatively high rates of turnover as CSF clears and potentially inadequate delivery to tissue or cellular targets. Nanomedicine could offer a solution. In contrast to the fate of freely administered drugs, nanomedicine systems can navigate the subarachnoid space to sustain delivery of therapeutic molecules, genes, and imaging agents within the CNS. Some evidence suggests that certain nanomedicine agents can reach the parenchyma following intrathecal administration. Here, we will address the preclinical and clinical use of intrathecal nanomedicine, including nanoparticles, microparticles, dendrimers, micelles, liposomes, polyplexes, and other colloidalal materials that function to alter the distribution of molecules in tissue. Our review forms a foundational understanding of drug delivery to the CSF that can be built upon to better engineer nanomedicine for intrathecal treatment of disease.

Brain Ventricular System and Cerebrospinal Fluid Development and Function: Light at the End of the Tube: A Primer with Latest Insights

The brain ventricular system is a series of connected cavities, filled with cerebrospinal fluid (CSF), that forms within the vertebrate central nervous system (CNS). The hollow neural tube is a hallmark of the chordate CNS, and a closed neural tube is essential for normal development. Development and function of the ventricular system is examined, emphasizing three interdigitating components that form a functional system: ventricle walls, CSF fluid properties, and activity of CSF constituent factors. The cellular lining of the ventricle both can produce and is responsive to CSF. Fluid properties and conserved CSF components contribute to normal CNS development. Anomalies of the CSF/ventricular system serve as diagnostics and may cause CNS disorders, further highlighting their importance. This review focuses on the evolution and development of the brain ventricular system, associated function, and connected pathologies. It is geared as an introduction for scholars with little background in the field.

Schizophrenia-related microdeletion causes defective ciliary motility and brain ventricle enlargement via microRNA-dependent mechanisms in mice

Progressive ventricular enlargement, a key feature of several neurologic and psychiatric diseases, is mediated by unknown mechanisms. Here, using murine models of 22q11-deletion syndrome (22q11DS), which is associated with schizophrenia in humans, we found progressive enlargement of lateral and third ventricles and deceleration of ciliary beating on ependymal cells lining the ventricular walls. The cilia-beating deficit observed in brain slices and in vivo is caused by elevated levels of dopamine receptors (Drd1), which are expressed in motile cilia. Haploinsufficiency of the microRNA-processing gene Dgcr8 results in Drd1 elevation, which is brought about by a reduction in Drd1-targeting microRNAs miR-382-3p and miR-674-3p. Replenishing either microRNA in 22q11DS mice normalizes ciliary beating and ventricular size. Knocking down the microRNAs or deleting their seed sites on Drd1 mimicked the cilia-beating and ventricular deficits. These results suggest that the Dgcr8-miR-382-3p/miR-674-3p-Drd1 mechanism contributes to deceleration of ciliary motility and age-dependent ventricular enlargement in 22q11DS.

Differential coupling between subcortical calcium and BOLD signals during evoked and resting state through simultaneous calcium fiber photometry and fMRI

Task based and resting state fMRI has been widely utilized to study brain functions. As the foundation of fMRI, the underlying neural basis of the BOLD signal has been extensively studied, but the detailed mechanism remains elusive, particularly during the resting state. To examine the neurovascular coupling, it is important to simultaneously record neural and vascular signals. Here we developed a novel setup of camera based, scalable simultaneous calcium fiber photometry and fMRI in rats. Using this setup, we recorded calcium signals of superior colliculus (SC) and lateral geniculate nucleus (LGN) and fMRI simultaneously during visual stimulation and the resting state. Our results revealed robust, region-specific coupling between calcium and BOLD signals in the task state and weaker, whole brain correlation in the resting state. Interestingly, the spatial specificity of such correlation in the resting state was improved upon regression of white matter, ventricle signals and global signals in fMRI data. Overall, our results suggest differential coupling of calcium and BOLD signals for subcortical regions between evoked and resting states, and the coupling relationship in the resting state was related with resting state BOLD preprocessing strategies.

Aquaporin 4 Silencing Aggravates Hydrocephalus Induced by Injection of Autologous Blood in Rats

BACKGROUND Aquaporin 4 (AQP4), the most abundant aquaporin in the brain, is a type of bidirectional water channel controlling the brain-water balance and plays a critical role in physiologic and pathologic water balance in the brain. AQP4 was reported to be elevated in hydrocephalus; therefore, we hypothesized that AQP4 contributes to hydrocephalus. In this study, the role of AQP4 in hydrocephalus was explored. MATERIAL AND METHODS The hydrocephalus rat model was established by injection of autologous blood. On Day 1 and Day 3 after injection of autologous blood, magnetic resonance imaging (MRI) and hematoxylin-eosin (HE) staining were performed to detect the changes in ventricles, and quantitative real-time PCR (qRT-PCR) and immunohistochemistry were carried out to detect the changes in AQP4 level. Thereafter, an AQP4-specific siRNA was used to downregulate AQP4. Then, on Day 3 after injection of autologous blood, the levels of AQP4 and connexin-43 were detected by qRT-PCR, immunohistochemistry, immunofluorescence, or Western blot analysis. MRI and HE staining were performed to detect the changes in ventricles, and Evans blue extravasation assay was used to assess blood-brain barrier integrity. RESULTS The hydrocephalus rat model was established successfully, and hydrocephalus rats showed a higher AQP4 level. Silencing AQP4 aggravated the hydrocephalus, with enlarged lateral ventricles and destruction of ependymal integrity and blood-brain barrier. CONCLUSIONS Our study demonstrates that silencing AQP4 aggravates hydrocephalus, indicating that AQP4 protects against hydrocephalus.

Molecular anatomy and functions of the choroidal blood-cerebrospinal fluid barrier in health and disease

The barrier between the blood and the ventricular cerebrospinal fluid (CSF) is located at the choroid plexuses. At the interface between two circulating fluids, these richly vascularized veil-like structures display a peculiar morphology explained by their developmental origin, and fulfill several functions essential for CNS homeostasis. They form a neuroprotective barrier preventing the accumulation of noxious compounds into the CSF and brain, and secrete CSF, which participates in the maintenance of a stable CNS internal environment. The CSF circulation plays an important role in volume transmission within the developing and adult brain, and CSF compartments are key to the immune surveillance of the CNS. In these contexts, the choroid plexuses are an important source of biologically active molecules involved in brain development, stem cell proliferation and differentiation, and brain repair. By sensing both physiological changes in brain homeostasis and peripheral or central insults such as inflammation, they also act as sentinels for the CNS. Finally, their role in the control of immune cell traffic between the blood and the CSF confers on the choroid plexuses a function in neuroimmune regulation and implicates them in neuroinflammation. The choroid plexuses, therefore, deserve more attention while investigating the pathophysiology of CNS diseases and related comorbidities.

Dosing, collection, and quality control issues in cerebrospinal fluid research using animal models

Cerebrospinal fluid (CSF) is a complex fluid filling the ventricular system and surrounding the brain and spinal cord. Although the bulk of CSF is created by the choroid plexus, a significant fraction derives from the interstitial fluid in the brain and spinal cord parenchyma. For this reason, CSF can often be used as a source of pharmacodynamic and prognostic biomarkers to reflect biochemical changes occurring within the brain. For instance, CSF biomarkers can be used to diagnose and track progression of disease as well as understand pharmacokinetic and pharmacodynamic relationships in clinical trials. To facilitate the use of these biomarkers in humans, studies in preclinical species are often valuable. This review summarizes methods for preclinical CSF collection for biomarkers from mice, rats, and nonhuman primates. In addition, dosing directly into CSF is increasingly being used to improve drug levels in the brain. Therefore, this review also summarizes the state of the art in CSF dosing in these preclinical species.

Dose-Different Effects of Orexin-A on the Renal Sympathetic Nerve and Blood Pressure in Urethane-Anesthetized Rats

Previous studies have demonstrated that central injection of orexin-A affects renal sympathetic nerve activity (RSNA) and blood pressure (BP) in both anesthetized and unanesthetized rats. In the present study, we examined, using urethane-anesthetized rats, the dose-dependent effects of intravenous (iv) or intralateral cerebral ventricular (LCV) injection of various doses of orexin-A on RSNA and BP. We found that injection of a low dose of orexin-A (10 ng iv or 0.01 ng LCV) suppressed RSNA and BP significantly. Conversely, a high dose (1000 ng iv or 10 ng LCV) of orexin-A elevated both RSNA and BP significantly. Pretreatment with either iv or LCV injection of thioperamide, a histaminergic H3-receptor antagonist, eliminated the effects of a low dose of orexin-A on both RSNA and BP. Both iv and LCV injection of diphenhydramine, a histaminergic H1-receptor antagonist, abolished the effects of a high dose of orexin-A on RSNA and BP. Furthermore, bilateral lesions of the hypothalamic suprachiasmatic nucleus (SCN) abolished the effects of both low and high doses of orexin-A on RSNA and BP. These findings suggest that orexin-A affects RSNA and BP in a dose-dependent manner and that the SCN and histaminergic nerve may be involved in the dose-different effects of orexin-A in rats.

Mapping Alterations to the Endogenous Elemental Distribution within the Lateral Ventricles and Choroid Plexus in Brain Disorders Using X-Ray Fluorescence Imaging

The choroid plexus and cerebral ventricles are critical structures for the production of cerebral spinal fluid (CSF) and play an important role in regulating ion and metal transport in the brain, however many aspects of its roles in normal physiology and disease states, such as psychiatric illness, remain unknown. The choroid plexus is difficult to examine in vivo, and in situ ex vivo, and as such has typically been examined indirectly with radiolabeled tracers or ex vivo stains, making measurements of the endogenous K+, Cl-, and Ca+ distributions unreliable. In the present study, we directly examined the distribution of endogenous ions and biologically relevant transition metals in the choroid plexus and regions surrounding the ventricles (ventricle wall, cortex, corpus callosum, striatum) using X-ray fluorescence imaging (XFI). We find that the choroid plexus was rich in Cl- and Fe while K+ levels increase further from the ventricle as Cl- levels decrease, consistent with the known role of ion transporters in the choroid plexus CSF production. A polyI:C offspring displayed enlarged ventricles, elevated Cl- surrounding the ventricles, and intraventricular calcifications. These observations fit with clinical findings in patients with schizophrenia and suggest maternal treatment with polyI:C may lead to dysfunctional ion regulation in offspring. This study demonstrates the power of XFI for examining the endogenous elemental distributions of the ventricular system in healthy brain tissue as well as disease models.

A Primate lncRNA Mediates Notch Signaling during Neuronal Development by Sequestering miRNA

Long non-coding RNAs (lncRNAs) are a diverse and poorly conserved category of transcripts that have expanded greatly in primates, particularly in the brain. We identified an lncRNA, which has acquired 16 microRNA response elements for miR-143-3p in the Catarrhini branch of primates. This lncRNA, termed LncND (neurodevelopment), is expressed in neural progenitor cells and then declines in neurons. Binding and release of miR-143-3p by LncND control the expression of Notch receptors. LncND expression is enriched in radial glia cells (RGCs) in the ventricular and subventricular zones of developing human brain. Downregulation in neuroblastoma cells reduced cell proliferation and induced neuronal differentiation, an effect phenocopied by miR-143-3p overexpression. Gain of function of LncND in developing mouse cortex led to an expansion of PAX6+ RGCs. These findings support a role for LncND in miRNA-mediated regulation of Notch signaling within the neural progenitor pool in primates that may have contributed to the expansion of cerebral cortex.

Brain-specific Crmp2 deletion leads to neuronal development deficits and behavioural impairments in mice

Several genome- and proteome-wide studies have associated transcription and translation changes of CRMP2 (collapsing response mediator protein 2) with psychiatric disorders, yet little is known about its function in the developing or adult mammalian brain in vivo. Here we show that brain-specific Crmp2 knockout (cKO) mice display molecular, cellular, structural and behavioural deficits, many of which are reminiscent of neural features and symptoms associated with schizophrenia. cKO mice exhibit enlarged ventricles and impaired social behaviour, locomotor activity, and learning and memory. Loss of Crmp2 in the hippocampus leads to reduced long-term potentiation, abnormal NMDA receptor composition, aberrant dendrite development and defective synapse formation in CA1 neurons. Furthermore, knockdown of crmp2 specifically in newborn neurons results in stage-dependent defects in their development during adult hippocampal neurogenesis. Our findings reveal a critical role for CRMP2 in neuronal plasticity, neural function and behavioural modulation in mice.

Sex Differences in the Embryonic Development of the Central Oxytocin System in Mice

Recent studies suggest that oxytocin (OXT) may be important for organising the neural circuitry that underlies adult social behaviour. Although most of the work exploring these effects has focused on early postnatal development, there is evidence that OXT may also be important during foetal development. However, without an understanding of how the OXT system develops, the ability to functionally link OXT in foetal life to adult behaviour is limited. To understand where and when OXT could be acting during embryonic development to affect the organisation of neural substrates, we examined the development of the mouse OXT system from embryonic day (E) 12.5 through postnatal day (PND) 2 using OXT receptor (OXTR) binding and a quantitative polymerase chain reaction. In both males and females, OXTR binding was observed by E16.5 in the ventricular and subventricular zones, as well as the developing amygdala. In males, OXT mRNA was not detectable until PND2, whereas it was detectable by E16.5 in females. OXTR mRNA was detected by E12.5 in both sexes, although females appear to have more OXTR mRNA during foetal development than males. The present study is significant because it is the first to reveal an unexpected sex difference in the development of the OXT system and supports the possibility that OXT during foetal development may contribute to sex differences in adult behaviour.

Increased ventricular cerebrospinal fluid lactate in depressed adolescents

BACKGROUND

Mitochondrial dysfunction has been increasingly examined as a potential pathogenic event in psychiatric disorders, although its role early in the course of major depressive disorder (MDD) is unclear. Therefore, the purpose of this study was to investigate mitochondrial dysfunction in medication-free adolescents with MDD through in vivo measurements of neurometabolites using high-spatial resolution multislice/multivoxel proton magnetic resonance spectroscopy.

METHODS

Twenty-three adolescents with MDD and 29 healthy controls, ages 12-20, were scanned at 3T and concentrations of ventricular cerebrospinal fluid lactate, as well as N-acetyl-aspartate (NAA), total creatine (tCr), and total choline (tCho) in the bilateral caudate, putamen, and thalamus were reported.

RESULTS

Adolescents with MDD exhibited increased ventricular lactate compared to healthy controls [F(1,41)=6.98, P=0.01]. However, there were no group differences in the other neurometabolites. Dimensional analyses in the depressed group showed no relation between any of the neurometabolites and symptomatology, including anhedonia and fatigue.

CONCLUSIONS

Increased ventricular lactate in depressed adolescents suggests mitochondrial dysfunction may be present early in the course of MDD; however it is still not known whether the presence of mitochondrial dysfunction is a trait vulnerability of individuals predisposed to psychopathology or a state feature of the disorder. Therefore, there is a need for larger multimodal studies to clarify these chemical findings in the context of network function.

Intraventricular Silicone Oil: A Case Report

Intracranial silicone oil is a rare complication of intraocular endotamponade with silicone oil. We describe a case of intraventricular silicone oil fortuitously observed 38 months after an intraocular tamponade for a complicated retinal detachment in an 82 year-old woman admitted in the Department of Neurology for a stroke. We confirm the migration of silicone oil along the optic nerve. We discuss this rare entity with a review of the few other cases reported in the medical literature. Intraventricular migration of silicone oil after intraocular endotamponade is usually asymptomatic but have to be known of the neurologists and the radiologists because of its differential diagnosis that are intraventricular hemorrhage and tumor.

Effect of Milnacipran Treatment on Ventricular Lactate in Fibromyalgia: A Randomized, Double-Blind, Placebo-Controlled Trial

Milnacipran, a serotonin/norepinephrine reuptake inhibitor, has been approved by the US Food and Drug Administration for the treatment of fibromyalgia (FM). This report presents the results of a randomized, double-blind, placebo-controlled trial of milnacipran conducted to test the hypotheses that a) similar to patients with chronic fatigue syndrome, patients with FM have increased ventricular lactate levels at baseline; b) 8 weeks of treatment with milnacipran will lower ventricular lactate levels compared with baseline levels and with ventricular lactate levels after placebo; and c) treatment with milnacipran will improve attention and executive function in the Attention Network Test compared with placebo. In addition, we examined the results for potential associations between ventricular lactate and pain. Baseline ventricular lactate measured by proton magnetic resonance spectroscopic imaging was found to be higher in patients with FM than in healthy controls (F1,37 = 22.11, P < .0001, partial η(2) = .37). Milnacipran reduced pain in patients with FM relative to placebo but had no effect on cognitive processing. At the end of the study, ventricular lactate levels in the milnacipran-treated group had decreased significantly compared with baseline and after placebo (F1,18 = 8.18, P = .01, partial η(2) = .31). A significantly larger proportion of patients treated with milnacipran showed decreases in both ventricular lactate and pain than those treated with placebo (P = .03). These results suggest that proton magnetic resonance spectroscopic imaging measurements of lactate may serve as a potential biomarker for a therapeutic response in FM and that milnacipran may act, at least in part, by targeting the brain response to glial activation and neuroinflammation.

PERSPECTIVE

Patients treated with milnacipran showed decreases in both pain and ventricular lactate levels compared with those treated with placebo, but, even after treatment, levels of ventricular lactate remained higher than in controls. The hypothesized mechanism for these decreases is via drug-induced reductions of a central inflammatory state.

Prenatal Exposure to Autism-Specific Maternal Autoantibodies Alters Proliferation of Cortical Neural Precursor Cells, Enlarges Brain, and Increases Neuronal Size in Adult Animals

Autism spectrum disorders (ASDs) affect up to 1 in 68 children. Autism-specific autoantibodies directed against fetal brain proteins have been found exclusively in a subpopulation of mothers whose children were diagnosed with ASD or maternal autoantibody-related autism. We tested the impact of autoantibodies on brain development in mice by transferring human antigen-specific IgG directly into the cerebral ventricles of embryonic mice during cortical neurogenesis. We show that autoantibodies recognize radial glial cells during development. We also show that prenatal exposure to autism-specific maternal autoantibodies increased stem cell proliferation in the subventricular zone (SVZ) of the embryonic neocortex, increased adult brain size and weight, and increased the size of adult cortical neurons. We propose that prenatal exposure to autism-specific maternal autoantibodies directly affects radial glial cell development and presents a viable pathologic mechanism for the maternal autoantibody-related prenatal ASD risk factor.

GSK3β regulates oligodendrogenesis in the dorsal microdomain of the subventricular zone via Wnt-β-catenin signaling

Oligodendrocytes, the myelinating cells of the CNS, are derived postnatally from oligodendrocyte precursors (OPs) of the subventricular zone (SVZ). However, the mechanisms that regulate their generation from SVZ neural stem cells (NSC) are poorly understood. Here, we have examined the role of glycogen synthase kinase 3β (GSK3β), an effector of multiple converging signaling pathways in postnatal mice. The expression of GSK3β by rt-qPCR was most prominent in the SVZ and in the developing white matter, around the first 1–2 weeks of postnatal life, coinciding with the peak periods of OP differentiation. Intraventricular infusion of the GSK3β inhibitor ARA-014418 in mice aged postnatal day (P) 8–11 significantly increased generation of OPs in the dorsal microdomain of the SVZ, as shown by expression of cell specific markers using rt-qPCR and immunolabelling. Analysis of stage specific markers revealed that the augmentation of OPs occurred via increased specification from earlier SVZ cell types. These effects of GSK3β inhibition on the dorsal SVZ were largely attributable to stimulation of the canonical Wnt/β-catenin signaling pathway over other pathways. The results indicate GSK3β is a key endogenous factor for specifically regulating oligodendrogenesis from the dorsal SVZ microdomain under the control of Wnt-signaling.

The subventricular zone is able to respond to a demyelinating lesion after localized radiation

Radiation is a common tool in the treatment of brain tumors that induces neurological deficits as a side effect. Some of these deficits appear to be related to the impact of radiation on the neurogenic niches, producing a drastic decrease in the proliferative capacity of these regions. In the adult mammalian brain, the subventricular zone (SVZ) of the lateral ventricles is the main neurogenic niche. Neural stem/precursor cells (NSCs) within the SVZ play an important role in brain repair following injuries. However, the irradiated NSCs' ability to respond to damage has not been previously elucidated. In this study, we evaluated the effects of localized radiation on the SVZ ability to respond to a lysolecithin-induced demyelination of the striatum. We demonstrated that the proliferation rate of the irradiated SVZ was increased after brain damage and that residual NSCs were reactivated. The irradiated SVZ had an expansion of doublecortin positive cells that appeared to migrate from the lateral ventricles toward the demyelinated striatum, where newly generated oligodendrocytes were found. In addition, in the absence of demyelinating damage, remaining cells in the irradiated SVZ appeared to repopulate the neurogenic niche a year post-radiation. These findings support the hypothesis that NSCs are radioresistant and can respond to a brain injury, recovering the neurogenic niche. A more complete understanding of the effects that localized radiation has on the SVZ may lead to improvement of the current protocols used in the radiotherapy of cancer.

Measurement of cerebrospinal fluid formation and absorption by ventriculo-cisternal perfusion: what is really measured?

The generally accepted hypothesis on cerebrospinal fluid (CSF) hydrodynamics suggests that CSF is actively formed mainly by the choroid plexuses, circulates unidirectionally along the brain ventricles and subarachnoid space, and is passively absorbed mainly into the dural venous sinuses. CSF formation rate (Vf) has been extensively studied using the ventriculo-cisternal perfusion technique and the results have been used as the key evidence confirming the mentioned hypothesis. This technique and the equation for Vf calculation are based on the assumption that the dilution of the indicator substance is a consequence of the newly formed CSF, ie, that a higher CSF formation rate will result in a higher degree of dilution. However, it has been experimentally shown that the indicator substance dilution inside the CSF system does not occur because of a "newly formed" CSF, but as consequence of a number of other factors (departure of substances into the surrounding tissue, flowing around the collecting cannula into the cortical and spinal subarachnoid space, departure into the contralateral ventricle, etc). This technique allows "calculation" of the CSF formation even in dead animals, in an in vitro model, and in any other part of the CSF system outside the ventricles that is being perfused. Therefore, this method is indirect and any dilution of the indicator substance in the perfusate caused by other reasons would result in questionable and often contradictory conclusions regarding CSF formation rates.

Fluorescent protein-expressing neural progenitor cells as a tool for transplantation studies

The purpose of this study was to generate quadruple fluorescent protein (QFP) transgenic mice as a source for QFP-expressing neural stem and progenitor cells (NSCs/NPCs) that could be utilized as a tool for transplantation research. When undifferentiated, these NSCs only express cyan fluorescent protein (CFP); however, upon neuronal differentiation, the cells express yellow fluorescent protein (YFP). During astrocytic differentiation, the cells express green fluorescent protein (GFP), and during oligodendrocytic differentiation, the cells express red fluorescent protein (DsRed). Using immunocytochemistry, immunoblotting, flow cytometry and electrophysiology, quadruple transgenic NPCs (Q-NPCs) and GFP-sorted NPCs were comprehensively characterized in vitro. Overall, the various transgenes did not significantly affect proliferation and differentiation of transgenic NPCs in comparison to wild-type NPCs. In contrast to a strong CFP and GFP expression in vitro, NPCs did not express YFP and dsRed either during proliferation or after differentiation in vitro. GFP-positive sorted NPCs, expressing GFP under the control of the human GFAP promoter, demonstrated a significant improvement in astroglial differentiation in comparison to GFP-negative sorted NPCs. In contrast to non-sorted and GFP-positive sorted NPCs, GFP-negative sorted NPCs demonstrated a high proportion of neuronal differentiation and proved to be functional in vitro. At 6 weeks after the intracerebroventricular transplantation of Q-NPCs into neonatal wild-type mice, CFP/DCX (doublecortin) double-positive transplanted cells were observed. The Q-NPCs did not express any other fluorescent proteins and did not mature into neuronal or glial cells. Although this model failed to visualize NPC differentiation in vivo, we determined that activation of the NPC glial fibrillary acid protein (GFAP) promoter, as indicated by GFP expression, can be used to separate neuronal and glial progenitors as a valuable tool for transplantation studies.

Activation of sirtuin 1 attenuates cerebral ventricular streptozotocin-induced tau hyperphosphorylation and cognitive injuries in rat hippocampi

Patients with diabetes in the aging population are at high risk of Alzheimer's disease (AD), and reduction of sirtuin 1 (SIRT1) activity occurs simultaneously with the accumulation of hyperphosphorylated tau in the AD-affected brain. It is not clear, however, whether SIRT1 is a suitable molecular target for the treatment of AD. Here, we employed a rat model of brain insulin resistance with intracerebroventricular injection of streptozotocin (ICV-STZ; 3 mg/kg, twice with an interval of 48 h). The ICV-STZ-treated rats were administrated with resveratrol (RSV; SIRT1-specific activator) or a vehicle via intraperitoneal injection for 8 weeks (30 mg/kg, once per day). In ICV-STZ-treated rats, the levels of phosphorylated tau and phosphorylated extracellular signal-regulated kinases 1 and 2 (ERK1/2) at the hippocampi were increased significantly, whereas SIRT1 activity was decreased without change of its expression level. The capacity of spatial memory was also significantly lower in ICV-STZ-treated rats compared with age-matched control. RSV, a specific activator of SIRT1, which reversed the ICV-STZ-induced decrease in SIRT1 activity, increases in ERK1/2 phosphorylation, tau phosphorylation, and impairment of cognitive capability in rats. In conclusion, SIRT1 protects hippocampus neurons from tau hyperphosphorylation and prevents cognitive impairment induced by ICV-STZ brain insulin resistance with decreased hippocampus ERK1/2 activity.

Neuro-immune interactions in the postnatal ventricular-subventricular zone

As described in this book, the interaction between the immune system and the brain can affect multiple cerebral functions, such as: neural remodeling, synaptic plasticity or neurotransmitter releasing. Neurogenic niches are not the exception, in fact, pro-inflammatory cytokines and chemokines exert a strong regulation in neural stem cells (NSCs) of the ventricular-subventricular zone (V-SVZ) by interacting with cell membrane receptors and activating multiple downstream pathways. These neuro-immune interactions modulate quiescence, cell adhesion, migration, self-renewal, differentiation, cytoskeletal rearrangement, and cell survival. In this chapter, we describe the cellular composition and cytoarchitecture of the main neurogenic niche in the adult mammalian brain: the V-SVZ. We also discuss the current evidence indicating that many immunological molecules can control the function of this neurogenic niche in the adult brain under both physiological and pathological conditions.

Higher Orexin A levels in lumbar compared to ventricular CSF: a study in idiopathic normal pressure hydrocephalus

Orexin A (ORX-A) is implicated in the regulation of various physiological processes, including sleep/wake cycles and reward/motivation. The hypothalamic ORX-A neurons project throughout the brain and spinal cord. In the present study we established and compared ORX-A levels in lumbar and ventricular cerebrospinal fluid (CSF) samples, drawn from idiopathic normal pressure hydrocephalus (INPH) patients, during respectively, lumbar puncture and shunt placement. Ventricular and lumbar CSF levels of total protein and of the dopamine, serotonin and norepinephrine metabolites HVA, 5-HIAA and MHPG respectively, were also estimated. ORX-A was quantified using a commercially available radioimmunoassay kit. Neurotransmitter metabolites were quantified by high performance liquid chromatography. Expectedly, HVA and 5-HIAA levels were significantly higher and total protein levels lower in ventricular compared to lumbar CSF while there were no differences in MHPG levels. However, in contrast to HVA and 5-HIAA and similar to total protein, lumbar ORX-A levels were significantly higher than ventricular levels. The higher lumbar compared to ventricular ORX-A levels may reflect elevated contributions from the spinal cord. The finding of a ventriculo-lumbar difference for ORX-A should be considered in studies utilizing its CSF levels in assessing Orexin system status.

[Peculiarities of neurodegeneration in hippocampus fields after kainic acid action in rats]

Comparison between results of different ways of application of excitotoxin (kainic acid, KA), intrahippocampal (0.2 μg/μl) and intraventricular (0.6 μg/μl), was carried out in the course of investigations of the prolonged action of KA on the morphological state of various fields in dorsal hippocampus. Light microscopy with Cresyl Violet staining and fluorescent microscopy with staining by fluoro-jade B were used in our researches. The results revealed that KA, being injected intrahippocampally at a dose, which does not result in animal epileptization, caused obvious degenerative phenomena in hippocampus. Two weeks after KA injection the layers of pyramid cells in the fields CA3 and CA4 were absent, and in four weeks, degenerative changes and cell lysis were spread on the CA1 field as well. Four weeks after KA intraventricular administration in rats with epileptic status the damages of various levels were observed in hippocampus, from partial injuries of pyramid neurons in the fields CA3 and CA4 up to full loss of layers of pyramids in the fields CA1, CA3 and CA4. In both ways of KA injection, in the CA2 field the layer of cells mainly remained undamaged what indicates a special role of this field. After a single-time KA administration the both ways of injection led to the long-term damages of a neural tissue, possibly, of a general character, but differing in rates of neuron reactions in different fields to the damaging factor. An explanation of the prolonged action of KA excitotoxicity might be in the activation of GluR6-containing kainate receptors in pyramid neurons in CA3 field which brings to chronic character in single-time KA action and promotes the destruction of the remaining neurons by necrotic way while at the initial stage of KA influence the neurons perish by apoptotic way.

Modeling the neurovascular niche: unbiased transcriptome analysis of the murine subventricular zone in response to hypoxic insult

Premature infants often experience chronic hypoxia, resulting in cognitive & motor neurodevelopmental handicaps. These sometimes devastating handicaps are thought to be caused by compromised neural precursor cell (NPC) repair/recovery resulting in variable central nervous system (CNS) repair/recovery. We have identified differential responses of two mouse strains (C57BL/6 & CD1) to chronic hypoxia that span the range of responsiveness noted in the premature human population. We previously correlated several CNS tissue and cellular behaviors with the different behavioral parameters manifested by these two strains. In this report, we use unbiased array technology to interrogate the transcriptome of the subventricular zone (SVZ) in these strains. Our results illustrate differences in mRNA expression in the SVZ of both C57BL/6 and CD1 mice following hypoxia as well as differences between C57BL/6 and CD1 SVZ under both normoxic and hypoxic conditions. Differences in expression were found in gene sets associated with Sox10-mediated neural functions that explain, in part, the differential cognitive and motor responsiveness to hypoxic insult. This may shed additional light on our understanding of the variable responses noted in the human premature infant population and facilitate early intervention approaches. Further interrogation of the differentially expressed gene sets will provide a more complete understanding of the differential responses to, and recovery from, hypoxic insult allowing for more informed modeling of the ranges of disease severity observed in the very premature human population.

3D mapping of cerebrospinal fluid local volume changes in patients with hydrocephalus treated by surgery: preliminary study

OBJECTIVE

To develop automated deformation modelling for the assessment of cerebrospinal fluid (CSF) local volume changes in patients with hydrocephalus treated by surgery.

METHODS

Ventricular and subarachnoid CSF volume changes were mapped by calculating the Jacobian determinant of the deformation fields obtained after non-linear registration of pre- and postoperative images. A total of 31 consecutive patients, 15 with communicating hydrocephalus (CH) and 16 with non-communicating hydrocephalus (NCH), were investigated before and after surgery using a 3D SPACE (sampling perfection with application optimised contrast using different flip-angle evolution) sequence. Two readers assessed CSF volume changes using 3D colour-encoded maps. The Evans index and postoperative volume changes of the lateral ventricles and sylvian fissures were quantified and statistically compared.

RESULTS

Before surgery, sylvian fissure and brain ventricle volume differed significantly between CH and NCH (P = 0.001 and P = 0.025, respectively). After surgery, 3D colour-encoded maps allowed for the visual recognition of the CSF volume changes in all patients. The amounts of ventricle volume loss of CH and NCH patients were not significantly different (P = 0.30), whereas readjustment of the sylvian fissure volume was conflicting in CH and NCH patients (P < 0.001). The Evans index correlated with ventricle volume in NCH patients.

CONCLUSION

3D mapping of CSF volume changes is feasible providing a quantitative follow-up of patients with hydrocephalus.

KEY POINTS

• MRI can provide helpful information about cerebrospinal fluid volumes. • 3D CSF mapping allows quantitative follow-up in communicating and non-communicating hydrocephalus. • Following intervention, fissures and cisterns readjust in both forms of hydrocephalus. • These findings support the hypothesis of suprasylvian block in communicating hydrocephalus. • 3D mapping may improve shunt dysfunction detection and guide valve pressure settings.

Cell proliferation in ependymal/subventricular zone and nNOS expression following focal cerebral ischemia in adult rats

Neuronal nitric oxide synthase (nNOS) regulates neurogenesis in normal developing brain, but the role of nNOS in neurogenesis in the ischemic brain remains unclear. To investigate the temporal and spatial relationship between cell proliferation of the ependymal/subventricular zone (SVZ), a principal neuroproliferative region in the adult brain, and nNOS expression, the male Sprague-Dawley rats weighing 250-350 g were used. The focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). 10 microl of 0.2% fluorescence dye DiI was injected into the right lateral ventricle to prelabel ependymal/subventricular zone cells before ischemia. The rats were killed immediately after ischemia and days 1, 3, 7, 11, 14, 21 and 28 after ischemia. DiI-labeled cell counting was employed to assess cell proliferation. Immunohistochemistry and grayscale analysis were performed to determine nNOS localization and its quantity in the specific regions. Compared with control, the density of DiI-labeled cells in the ipsilateral ependyma/SVZ was significantly higher at days 1, 3, 7 and 11 after ischemia, whereas the quantity of nNOS expression in the ependyma/SVZ adjacent regions was significantly lower at the above time points. Additionally, nNOS positive cells were largely excluded from SVZ, and their long processes did not enter the ependyma/SVZ. Our results indicate that after focal cerebral ischemia, decreased nNOS expression in the ipsilateral ependymal/SVZ adjacent regions might be related to cell proliferation in the ependymal/SVZ.

Temporal changes of neurogenesis in the mouse hippocampus after experimental subarachnoid hemorrhage

Recent studies indicate the existence of progenitor cells and their potential for neurogenesis in the subventricular zone (SVZ) and the hippocampus dentate gyrus (DG) of normal adult mammalian brain. Increased neurogenesis has been shown following cerebral ischemia and traumatic brain injury; however, the involvement of neurogenesis in subarachnoid hemorrhage (SAH) has not been examined. Adult male CD-1 mice were subjected to SAH by endovascular perforation of the left anterior cerebral artery. Mice received intraperitoneal injections of the cell proliferation-specific marker 5'-bromodeoxyuridine (BrdU) after SAH induction. BrdU incorporation was examined from 1 to 30 days after SAH by immunohistochemistry. The BrdU-positive cells were detected in SVZ and DG of normal control brain, and were significantly decreased in both areas three days after SAH. The number of these cells had recovered to its control level seven days after SAH. Double staining with BrdU and NeuN indicated that the majority of the BrdU-positive cells migrating into the granular cell layer of the DG became NeuN-positive 30 days after SAH. In conclusion, temporal changes of the neurogenesis as shown in the present study suggest that neurogenesis in the hippocampus may affect functional outcome after SAH. The induction of the neurogenesis can provide therapeutic value against SAH.

Cortical gyrification induced by fibroblast growth factor 2 in the mouse brain

Gyrification allows an expanded cortex with greater functionality to fit into a smaller cranium. However, the mechanisms of gyrus formation have been elusive. We show that ventricular injection of FGF2 protein at embryonic day 11.5-before neurogenesis and before the formation of intrahemispheric axonal connections-altered the overall size and shape of the cortex and induced the formation of prominent, bilateral gyri and sulci in the rostrolateral neocortex. We show increased tangential growth of the rostral ventricular zone (VZ) but decreased Wnt3a and Lef1 expression in the cortical hem and adjacent hippocampal promordium and consequent impaired growth of the caudal cortical primordium, including the hippocampus. At the same time, we observed ectopic Er81 expression, increased proliferation of Tbr2-expressing (Tbr2(+)) intermediate neuronal progenitors (INPs), and elevated Tbr1(+) neurogenesis in the regions that undergo gyrification, indicating region-specific actions of FGF2 on the VZ and subventricular zone (SVZ). However, the relative number of basal radial glia-recently proposed to be important in gyrification-appeared to be unchanged. These findings are consistent with the hypothesis that increased radial unit production together with rapid SVZ growth and heightened localized neurogenesis can cause cortical gyrification in lissencephalic species. These data also suggest that the position of cortical gyri can be molecularly specified in mice. In contrast, a different ligand, FGF8b, elicited surface area expansion throughout the cortical primordium but no gyrification. Our findings demonstrate that individual members of the diverse Fgf gene family differentially regulate global as well as regional cortical growth rates while maintaining cortical layer structure.

GABA(A) receptor characterization and subunit localization in the human sub-ventricular zone

It is now well established that the human brain continuously produces new stem cells until well into old age. One of these stem-cell rich areas in the human brain is the sub-ventricular zone (SVZ). The human SVZ is organized in four distinctive layers containing type A, B and C cells. To date, no studies have investigated the distribution of inhibitory neurotransmitters such as γ-aminobutyric acid (GABA) and their respective receptors on the different cell types in the human SVZ. GABA(A) receptors (GABA(A)R) are ubiquitously expressed, inhibitory heteropentameric chloride ion channels comprised of a variety of subunits that are targeted by many prescribed drugs. In this study we present detailed immunohistochemical data on the regional and cellular localization of α₁, α₂, α3, β₂,₃ and γ₂ subunits of GABA(A)R in the human SVZ. The results from our double and triple labeling studies demonstrate that the cell types and subunit composition throughout the SVZ is heterogeneous; the thickness of the SVZ and GABA(A)R α₂ and γ₂ expression is increased especially in the vicinity of large SVZ blood vessels. GABA(A)R γ₂ is the most specific to the SVZ and present on various cells that express, either glial fibrillary acidic protein (GFAPδ) or polysialic acid-neural cell adhesion molecule (PSA-NCAM) separately, or together in a respective ratio of 7:6:2. Proliferating (type C) cells in the SVZ express GAD65/67, GFAPδ and GABA(A)R β₂,₃ receptor subunits. Within the SVZ the majority of cells have an unexpected nuclear GABA(A)R β₂,₃ expression that is inversely proportional to that of PCNA (proliferating cell nuclear antigen marker), which is a very different pattern of expression compared with underlying caudate nucleus cells. Taken together our results provide a detailed description of the chemo-architecture of the adult human SVZ demonstrating the importance of GABA and GABA(A) receptors on the various cell types in the SVZ.

Diversity of neural precursor cell types in the prenatal macaque cerebral cortex exists largely within the astroglial cell lineage

The germinal zones of the embryonic macaque neocortex comprise the ventricular zone (VZ) and the subventricular zone (SVZ). The mammalian SVZ is subdivided into an inner SVZ and an outer SVZ, with the outer SVZ being particularly large in primates. The existence of distinct precursor cell types in the neocortical proliferative zones was inferred over 100 years ago and recent evidence supports this concept. Precursor cells exhibiting diverse morphologies, patterns of transcription factor expression, and fate potential have been identified in the neocortical proliferative zones. Neurogenic precursor cells are thought to exhibit characteristics of glial cells, but the existence of neurogenic precursor cells that do not share glial specific properties has also been proposed. Therefore, one question that remains is whether neural precursor cells in the prenatal neocortex belong within the astroglial cell class, as they do in neurogenic regions of the adult neocortex, or instead include a diverse collection of precursor cells belonging to distinct cell classes. We examined the expression of astroglial markers by mitotic precursor cells in the telencephalon of prenatal macaque and human. We show that in the dorsal neocortex all mitotic cells at the surface of the ventricle, and all Pax6+ and Tbr2+ mitotic cells in the proliferative zones, express the astroglial marker GFAP. The majority of mitotic cells undergoing division away from the ventricle express GFAP, and many of the GFAP-negative mitoses express markers of cells derived from the ventral telencephalon or extracortical sites. In contrast, a markedly lower proportion of precursor cells express GFAP in the ganglionic eminence. In conclusion, we propose that the heterogeneity of neural precursor cells in the dorsal cerebral cortex develops within the GFAP+ astroglial cell class.

Increased Reissner's fiber material in the subcommissural organ and ventricular area in bile duct ligated rats

Hepatic encephalopathy is a common neuropsychiatric complication of acute and chronic liver failure. Whether brain structures with strategic positions in the interface of blood-brain barriers such as the circumventricular organs are involved in hepatic encephalopathy is not yet established. Among the circumventricular organs, the subcommissural organ secretes a glycoprotein known as Reissner's fiber, which condenses and forms an ever-growing thread-like structure into the cerebrospinal fluid. In the present work we describe the Reissner's fiber material within the subcommissural organ and its serotoninergic innervation in an animal model of chronic hepatic encephalopathy following bile duct ligation in experimental rats. The study involved immunohistochemical techniques with antibodies against Reissner's fiber and 5-hydroxytryptamine (5-HT). Four weeks after surgical bile duct ligation, a significant rise of Reissner's fiber immunoreactivity was observed in all subcommissural organ areas compared with controls. Moreover, significant Reissner's fiber immunoreactive materials within the ependyma and inside the parenchyma close to the ventricular borders were also seen in bile duct ligated rats, but not in control rats. Increased Reissner's fiber material in bile duct ligated rats seems to be related to a reduction of 5-HT innervation of the subcommissural organ, the ventricular borders and the nucleus of origin, the dorsal raphe nucleus. Our data describe alterations of the subcommissural organ/Reissner's fiber material and the subcommissural organ 5-HT innervation probably due to a general 5-HT deficit in bile duct ligated rats.

Increased ventricular lactate in chronic fatigue syndrome. III. Relationships to cortical glutathione and clinical symptoms implicate oxidative stress in disorder pathophysiology

Chronic fatigue syndrome (CFS) is a complex illness, which is often misdiagnosed as a psychiatric illness. In two previous reports, using (1)H MRSI, we found significantly higher levels of ventricular cerebrospinal fluid (CSF) lactate in patients with CFS relative to those with generalized anxiety disorder and healthy volunteers (HV), but not relative to those with major depressive disorder (MDD). In this third independent cross-sectional neuroimaging study, we investigated a pathophysiological model which postulated that elevations of CSF lactate in patients with CFS might be caused by increased oxidative stress, cerebral hypoperfusion and/or secondary mitochondrial dysfunction. Fifteen patients with CFS, 15 with MDD and 13 HVs were studied using the following modalities: (i) (1)H MRSI to measure CSF lactate; (ii) single-voxel (1)H MRS to measure levels of cortical glutathione (GSH) as a marker of antioxidant capacity; (iii) arterial spin labeling (ASL) MRI to measure regional cerebral blood flow (rCBF); and (iv) (31)P MRSI to measure brain high-energy phosphates as objective indices of mitochondrial dysfunction. We found elevated ventricular lactate and decreased GSH in patients with CFS and MDD relative to HVs. GSH did not differ significantly between the two patient groups. In addition, we found lower rCBF in the left anterior cingulate cortex and the right lingual gyrus in patients with CFS relative to HVs, but rCBF did not differ between those with CFS and MDD. We found no differences between the three groups in terms of any high-energy phosphate metabolites. In exploratory correlation analyses, we found that levels of ventricular lactate and cortical GSH were inversely correlated, and significantly associated with several key indices of physical health and disability. Collectively, the results of this third independent study support a pathophysiological model of CFS in which increased oxidative stress may play a key role in CFS etiopathophysiology.

A paravascular pathway facilitates CSF flow through the brain parenchyma and the clearance of interstitial solutes, including amyloid β

Because it lacks a lymphatic circulation, the brain must clear extracellular proteins by an alternative mechanism. The cerebrospinal fluid (CSF) functions as a sink for brain extracellular solutes, but it is not clear how solutes from the brain interstitium move from the parenchyma to the CSF. We demonstrate that a substantial portion of subarachnoid CSF cycles through the brain interstitial space. On the basis of in vivo two-photon imaging of small fluorescent tracers, we showed that CSF enters the parenchyma along paravascular spaces that surround penetrating arteries and that brain interstitial fluid is cleared along paravenous drainage pathways. Animals lacking the water channel aquaporin-4 (AQP4) in astrocytes exhibit slowed CSF influx through this system and a ~70% reduction in interstitial solute clearance, suggesting that the bulk fluid flow between these anatomical influx and efflux routes is supported by astrocytic water transport. Fluorescent-tagged amyloid β, a peptide thought to be pathogenic in Alzheimer's disease, was transported along this route, and deletion of the Aqp4 gene suppressed the clearance of soluble amyloid β, suggesting that this pathway may remove amyloid β from the central nervous system. Clearance through paravenous flow may also regulate extracellular levels of proteins involved with neurodegenerative conditions, its impairment perhaps contributing to the mis-accumulation of soluble proteins.

miR-132 enhances dendritic morphogenesis, spine density, synaptic integration, and survival of newborn olfactory bulb neurons

An array of signals regulating the early stages of postnatal subventricular zone (SVZ) neurogenesis has been identified, but much less is known regarding the molecules controlling late stages. Here, we investigated the function of the activity-dependent and morphogenic microRNA miR-132 on the synaptic integration and survival of olfactory bulb (OB) neurons born in the neonatal SVZ. In situ hybridization revealed that miR-132 expression occurs at the onset of synaptic integration in the OB. Using in vivo electroporation we found that sequestration of miR-132 using a sponge-based strategy led to a reduced dendritic complexity and spine density while overexpression had the opposite effects. These effects were mirrored with respective changes in the frequency of GABAergic and glutamatergic synaptic inputs reflecting altered synaptic integration. In addition, timely directed overexpression of miR-132 at the onset of synaptic integration using an inducible approach led to a significant increase in the survival of newborn neurons. These data suggest that miR-132 forms the basis of a structural plasticity program seen in SVZ-OB postnatal neurogenesis. miR-132 overexpression in transplanted neurons may thus hold promise for enhancing neuronal survival and improving the outcome of transplant therapies.

Intracerebroventricular administration of neuronostatin delays gastric emptying and gastrointestinal transit in mice

Neuronostatin is a 13-amino acid amidated peptide widely distributed in various organs including gastrointestinal tract. However, the effect of neuronostatin on gastrointestinal motility has not been well characterized. In the present work, effects of central administration of neuronostatin on gastric emptying and gastrointestinal transit were investigated. The results indicated that intracerebroventricular (i.c.v.) administration of neuronostatin (1, 5, 10 or 20nmol/mouse) delayed gastric emptying and gastrointestinal transit in a dose-related manner in mice. The effects were significantly reversed by melanocortin 3/4 receptor antagonist SHU9119 or classical opioid receptor antagonist naloxone, suggesting that the central melanocortin system and opioid system may be involved in the gastrointestinal effects elicited by i.c.v. administration of neuronostatin. In addition, we found that C-terminal amidation modification of neuronostatin is essential to exert its gastrointestinal effects. These results indicated that neuronostatin may play an important role in regulating gastrointestinal function.

[Developmental expression and cellular distribution of metabotropic glutamate receptor 5 in the frontal cortex of human fetus]

OBJECTIVE

To investigate the expression of metabotropic glutamate receptor 5 (mGluR5) and its cellular distribution in the frontal cortex, ventricular zone (VZ) and subventricular zone (SVZ) in human fetuses.

METHODS

According to the gestational age, the collected fetuses were divided into 4 groups, namely 9-11 weeks, 14-16 weeks, 22-24 weeks and 32-36 weeks. Brain tissue blocks including the frontal lobe or VZ/SVZ were prepared into slices, and the expression pattern and cellular distribution of mGluR5 in the frontal cortex and VZ/SVZ were observed by immunohistochemistry or immunofluorescence.

RESULTS

mGluR5 immunoreactivity was present in the cell membrane in the frontal cortex, VZ and SVZ from the 9th to 36th weeks and the immunoreactivity in the marginal zone (MZ) and cortical plate (CP) was markedly stronger than that in VZ and SVZ. The cells expressing mGluR5 included neural stem/progenitor cells in the VZ and SVZ, immature neurons in the VZ and MZ, and numerous mature neurons in the CP.

CONCLUSION

mGluR5 is expressed by a variety of cells such as neural stem cells in the frontal cortex, VZ and SVZ in human fetus, suggesting a role of mGluR5 in the development of human cerebral cortex.

[Neurochemical markers of cells of the periventricular brain area in the masu salm on Oncorhynchus masou (Salmonidae)]

Localization of GABA, tyrosine hydroxylase (TH), NADPH-diaphorase, transcription factor Pax6, and the proliferative cell antigen (PCNA) in the periventricular area of the brain of the masu salmon Oncorhynchus masou of varying age groups was studied. The presence of heterogeneous cell populations with radially orientated outgrowths in the diencephalon, central gray matter of the dorsomedial tegmentum, medulla oblongata, and spinal cord of the masu salmon was shown. TH-, GABA-immunopositive, and NADPH-d-positive cells are located in the areas of PCNA-immunogenic proliferative zones. It is possible that these cells are descendants of the radial neuroglia and that they participate in the growth and physiological regeneration of diencephalic and medullar structures. In various age groups of the masu salmon, the marking of TH-, GABA, PCNA, and Pax6 reveals the neuromeric structure of the brain.

Deficiency of mDia, an actin nucleator, disrupts integrity of neuroepithelium and causes periventricular dysplasia

During development of the central nervous system, the apical-basal polarity of neuroepithelial cells is critical for homeostasis of proliferation and differentiation of neural stem cells. While adherens junctions at the apical surface of neuroepithelial cells are important for maintaining the polarity, the molecular mechanism regulating integrity of these adherens junctions remains largely unknown. Given the importance of actin cytoskeleton in adherens junctions, we have analyzed the role of mDia, an actin nucleator and a Rho effector, in the integrity of the apical adherens junction. Here we show that mDia1 and mDia3 are expressed in the developing brain, and that mDia3 is concentrated in the apical surface of neuroepithelium. Mice deficient in both mDia1 and mDia3 develop periventricular dysplastic mass widespread throughout the developing brain, where neuroepithelial cell polarity is impaired with attenuated apical actin belts and loss of apical adherens junctions. In addition, electron microscopic analysis revealed abnormal shrinkage and apical membrane bulging of neuroepithelial cells in the remaining areas. Furthermore, perturbation of Rho, but not that of ROCK, causes loss of the apical actin belt and adherens junctions similarly to mDia-deficient mice. These results suggest that actin cytoskeleton regulated by Rho-mDia pathway is critical for the integrity of the adherens junctions and the polarity of neuroepithelial cells, and that loss of this signaling induces aberrant, ectopic proliferation and differentiation of neural stem cells.

MicroRNA profiling in subventricular zone after stroke: MiR-124a regulates proliferation of neural progenitor cells through Notch signaling pathway

Background

The Notch signaling pathway regulates adult neurogenesis under physiological and pathophysiological conditions. MicroRNAs are small non-coding RNA molecules that regulate gene expression. The present study investigated the effect of miR-124a on the Notch signaling pathway in stroke-induced neurogenesis.

Methodology and Principal Findings

We found that adult rats subjected to focal cerebral ischemia exhibited substantial reduction of miR-124a expression, a neuron specific miRNA, in the neural progenitor cells of the subventricular zone (SVZ) of the lateral ventricle, which was inversely associated with activation of Notch signals. In vitro, transfection of neural progenitor cells harvested from the SVZ of adult rat with miR-124a repressed Jagged-1 (JAG1), a ligand of Notch, in a luciferase construct containing the JAG1 target site. Introduction of miR-124a in neural progenitor cells significantly reduced JAG1 transcript and protein levels, leading to inactivation of Notch signals. Transfection of neural progenitor cells with miR-124a significantly reduced progenitor cell proliferation and promoted neuronal differentiation measured by an increase in the number of Doublecortin positive cells, a marker of neuroblasts. Furthermore, introduction of miR-124a significantly increased p27Kip1 mRNA and protein levels, a downstream target gene of the Notch signaling pathway.

Conclusions

Collectively, our study demonstrated that in vivo, stroke alters miRNA expression in SVZ neural progenitor cells and that in vitro, miR-124a mediates stroke-induced neurogenesis by targeting the JAG-Notch signaling pathway.

Anti-allodynic effects of intrathecally and intracerebroventricularly administered 26RFa, an intrinsic agonist for GRP103, in the rat partial sciatic nerve ligation model

26RFa and QRFP are endogenous ligands of GPR103. 26RFa binding sites are widely distributed in the brain and the spinal cord where they are involved in processing pain. In the present study, the effects of intrathecal and intracerebroventricular applications of 26RFa on the level of mechanical allodynia induced by partial sciatic nerve ligation were examined in rats. The level of mechanical allodynia was measured using von Frey filaments. Intrathecal and intracerebroventricular injection of 26RFa attenuated the level of mechanical allodynia. 26RFa has been reported to activate not only GPR103 but also neuropeptide FF2 receptor and the effect of intrathecally and intracerebroventricularly administered 26RFa was not antagonized by BIBP3226, an antagonist of neuropeptide FF receptor. Immunohistochemical examination revealed that QRFP-like immunoreactivity (QRFP-LI) was expressed mainly in the small to medium sized neurons in the L5 dorsal root ganglion (DRG) and that partial sciatic nerve injury increased the percentage of QRFP-LI positive neurons. 7 days after the nerve injury, QRFP-LI positive neurons in the L5 DRG ipsilateral to the partial sciatic nerve injury were larger than those in the L5 DRG ipsilateral to the sham operation. These data suggest that (1) exogenously applied 26RFa modulates nociceptive transmission at the spinal and the supraspinal brain in the neuropathic pain model, (2) the mechanism 26RFa uses to produce an anti-allodynic effect may be mediated by the activation of GPR103, and (3) partial sciatic nerve ligation affects the expression of QRFP-LI in the dorsal root ganglion.

Reelin controls progenitor cell migration in the healthy and pathological adult mouse brain

Understanding the signals that control migration of neural progenitor cells in the adult brain may provide new therapeutic opportunities. Reelin is best known for its role in regulating cell migration during brain development, but we now demonstrate a novel function for reelin in the injured adult brain. First, we show that Reelin is upregulated around lesions. Second, experimentally increasing Reelin expression levels in healthy mouse brain leads to a change in the migratory behavior of subventricular zone-derived progenitors, triggering them to leave the rostral migratory stream (RMS) to which they are normally restricted during their migration to the olfactory bulb. Third, we reveal that Reelin increases endogenous progenitor cell dispersal in periventricular structures independently of any chemoattraction but via cell detachment and chemokinetic action, and thereby potentiates spontaneous cell recruitment to demyelination lesions in the corpus callosum. Conversely, animals lacking Reelin signaling exhibit reduced endogenous progenitor recruitment at the lesion site. Altogether, these results demonstrate that beyond its known role during brain development, Reelin is a key player in post-lesional cell migration in the adult brain. Finally our findings provide proof of concept that allowing progenitors to escape from the RMS is a potential therapeutic approach to promote myelin repair.