Effects of taxol on neuronal differentiation of postnatal neural stem cells cultured from mouse subventricular zone.

Taxol (paclitaxel), a chemotherapeutic agent for several cancers, can adversely affect the peripheral nervous system. Recently, its negative impact on cognitive function in cancer patients has become evident. In rodents, taxol impaired learning and memory, with other possible negative effects on the brain. In this study, we investigated the effects of taxol on cultured neural stem cells (NSCs) from the mouse neurogenic region, the subventricular zone (SVZ). Taxol significantly decreased both proliferation and neuronal differentiation of NSCs. Transient treatment with taxol for one day during a 4-day differentiation greatly decreased neurogenesis along with an abnormal cell cycle progression. Yet, taxol did not kill differentiated Tuj1+ neurons and those neurons had longer neurites than neurons under control conditions. For glial differentiation, taxol significantly reduced oligodendrogenesis as observed by immunostaining for Olig2 and O4. However, differentiation of astrocytes was not affected by taxol. In contrast, differentiated oligodendrocytes were extremely sensitive to taxol. Almost no Olig2-positive cells were observed after three days of treatment with taxol. Taxol has distinct effects on neurons and glial cells during their production through differentiation from NSCs as well as post-differentiation. Thus, we suggest that taxol might interfere with neurogenesis of NSCs possibly through a disturbance in the cell cycle and may eliminate differentiated oligodendrocytes.

CAMSAP3 is required for mTORC1-dependent ependymal cell growth and lateral ventricle shaping in mouse brains.

Microtubules (MTs) regulate numerous cellular processes, but their roles in brain morphogenesis are not well known. Here, we show that CAMSAP3, a non-centrosomal microtubule regulator, is important for shaping the lateral ventricles. In differentiating ependymal cells, CAMSAP3 became concentrated at the apical domains, serving to generate MT networks at these sites. Camsap3-mutated mice showed abnormally narrow lateral ventricles, in which excessive stenosis or fusion was induced, leading to a decrease of neural stem cells at the ventricular and subventricular zones. This defect was ascribed at least in part to a failure of neocortical ependymal cells to broaden their apical domain, a process necessary for expanding the ventricular cavities. mTORC1 was required for ependymal cell growth but its activity was downregulated in mutant cells. Lysosomes, which mediate mTORC1 activation, tended to be reduced at the apical regions of the mutant cells, along with disorganized apical MT networks at the corresponding sites. These findings suggest that CAMSAP3 supports mTORC1 signaling required for ependymal cell growth via MT network regulation, and, in turn, shaping of the lateral ventricles.

hGFAP-Positive Stem Cells Depend on Brg1 for Proper Formation of Cerebral and Cerebellar Structures.

Brahma-related gene 1 (Brg1) is one of the two mutually exclusive catalytic subunits of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex. Several roles of Brg1 have been described including acting as a tumor suppressor but also functioning in neural stem cell (NSC) maintenance, neural crest development, or differentiation of oligodendrocytes and Schwann cells. Here, we generated human glial fibrillary acidic protein (hGFAP)-cre::Brg1fl/fl mice to analyze the function of Brg1 in multipotential NSCs during late stages of neural development. hGFAP-cre::Brg1fl/fl mice died approximately 2 weeks after birth. Macroscopic examination revealed a severe hydrocephalus and a decreased brain weight caused by the loss of Brg1. The cerebellum of hGFAP-cre::Brg1fl/fl mice displayed disorganized cortical layers as well as a massive hypoplasia due to a dramatically reduced number of granule neurons. The cerebrum presented with less proliferative and more apoptotic precursor cells in the subventricular zone (SVZ). Furthermore, the cerebral cortex stood out with significantly thinned upper layers and with impressive dendrite pathology. Finally, the hippocampus was severely underdeveloped with only a sparse number of detectable neurons. We conclude that NSCs depend on Brg1 to give rise to major essential brain structures including the cerebellum, the cerebral cortex, and the hippocampus.

Impact of Mesenchymal Stromal Cell Delivery Through Cardiopulmonary Bypass on Postnatal Neurogenesis.

BACKGROUND: Neurodevelopmental impairment is an important challenge for survivors after neonatal surgery with cardiopulmonary bypass (CPB). The subventricular zone, where most neural stem/progenitors originate, plays a critical role in cortical maturation of the frontal lobe. Promoting neurogenesis in the subventricular zone is therefore a potential therapeutic target for preserving cortical growth. Mesenchymal stromal cells (MSCs) promote endogenous regeneration in the rodent brain. We investigated the impact of MSC delivery through CPB on neural stem/progenitor cells and neuroblasts (ie, young neurons) in the piglet subventricular zone. METHODS: Two-week-old piglets (n = 12) were randomly assigned to one of three groups: (1) control, (2) deep hypothermic circulatory arrest, and (3) circulatory arrest, followed by MSC administration. MSCs (10 × 106 per kg) were delivered through CPB during the rewarming period. Neural stem/progenitors, proliferating cells, and neuroblasts were identified with immunohistochemistry at 3 hours after CPB. RESULTS: CPB-induced insults caused an increased proliferation of neural stem/progenitors (P < .05). MSC delivery reduced the acute proliferation. MSC treatment increased the number of neuroblasts in the outer region of the subventricular zone (P < .05) where they form migrating chains toward the frontal lobe. Conversely, the thickness of the neuroblast-dense band along the lateral ventricle was reduced after treatment (P < .05). These findings suggest that MSC treatment changes neuroblast distribution within the subventricular zone. CONCLUSIONS: MSC delivery through CPB has the potential to mitigate effects of CPB on neural stem/progenitor cells and to promote migration of neuroblasts. Further investigation is necessary to determine the long-term effect of MSC treatment during CPB on postnatal neurogenesis.

Gliogenesis in the outer subventricular zone promotes enlargement and gyrification of the primate cerebrum.

The primate cerebrum is characterized by a large expansion of cortical surface area, the formation of convolutions, and extraordinarily voluminous subcortical white matter. It was recently proposed that this expansion is primarily driven by increased production of superficial neurons in the dramatically enlarged outer subventricular zone (oSVZ). Here, we examined the development of the parietal cerebrum in macaque monkey and found that, indeed, the oSVZ initially adds neurons to the superficial layers II and III, increasing their thickness. However, as the oSVZ grows in size, its output changes to production of astrocytes and oligodendrocytes, which in primates outnumber cerebral neurons by a factor of three. After the completion of neurogenesis around embryonic day (E) 90, when the cerebrum is still lissencephalic, the oSVZ enlarges and contains Pax6+/Hopx+ outer (basal) radial glial cells producing astrocytes and oligodendrocytes until after E125. Our data indicate that oSVZ gliogenesis, rather than neurogenesis, correlates with rapid enlargement of the cerebrum and development of convolutions, which occur concomitantly with the formation of cortical connections via the underlying white matter, in addition to neuronal growth, elaboration of dendrites, and amplification of neuropil in the cortex, which are primary factors in the formation of cerebral convolutions in primates.

Phosphodiesterase7 Inhibition Activates Adult Neurogenesis in Hippocampus and Subventricular Zone In Vitro and In Vivo.

The phosphodiesterase 7 (PDE7) enzyme is one of the enzymes responsible for controlling intracellular levels of cyclic adenosine 3',5'-monophosphate in the immune and central nervous system. We have previously shown that inhibitors of this enzyme are potent neuroprotective and anti-inflammatory agents. In addition, we also demonstrated that PDE7 inhibition induces endogenous neuroregenerative processes toward a dopaminergic phenotype. Here, we show that PDE7 inhibition controls stem cell expansion in the subgranular zone of the dentate gyrus of the hippocampus (SGZ) and the subventricular zone (SVZ) in the adult rat brain. Neurospheres cultures obtained from SGZ and SVZ of adult rats treated with PDE7 inhibitors presented an increased proliferation and neuronal differentiation compared to control cultures. PDE7 inhibitors treatment of neurospheres cultures also resulted in an increase of the levels of phosphorylated cAMP response element binding protein, suggesting that their effects were indeed mediated through the activation of the cAMP/PKA signaling pathway. In addition, adult rats orally treated with S14, a specific inhibitor of PDE7, presented elevated numbers of proliferating progenitor cells, and migrating precursors in the SGZ and the SVZ. Moreover, long-term treatment with this PDE7 inhibitor shows a significant increase in newly generated neurons in the olfactory bulb and the hippocampus. Also a better performance in memory tests was observed in S14 treated rats, suggesting a functional relevance for the S14-induced increase in SGZ neurogenesis. Taken together, our results indicate for the first time that inhibition of PDE7 directly regulates proliferation, migration and differentiation of neural stem cells, improving spatial learning and memory tasks. Stem Cells 2017;35:458-472.

Dentate Gyrus Development Requires ERK Activity to Maintain Progenitor Population and MAPK Pathway Feedback Regulation.

The ERK/MAPK pathway is an important developmental signaling pathway. Mutations in upstream elements of this pathway result in neuro-cardio-facial cutaneous (NCFC) syndromes, which are typified by impaired neurocognitive abilities that are reliant upon hippocampal function. The role of ERK signaling during hippocampal development has not been examined and may provide critical insight into the cause of hippocampal dysfunction in NCFC syndromes. In this study, we have generated ERK1 and conditional ERK2 compound knock-out mice to determine the role of ERK signaling during development of the hippocampal dentate gyrus. We found that loss of both ERK1 and ERK2 resulted in 60% fewer granule cells and near complete absence of neural progenitor pools in the postnatal dentate gyrus. Loss of ERK1/2 impaired maintenance of neural progenitors as they migrate from the dentate ventricular zone to the dentate gyrus proper, resulting in premature depletion of neural progenitor cells beginning at E16.5, which prevented generation of granule cells later in development. Finally, loss of ERK2 alone does not impair development of the dentate gyrus as animals expressing only ERK1 developed a normal hippocampus. These findings establish that ERK signaling regulates maintenance of progenitor cells required for development of the dentate gyrus.

Paucimannosidic glycoepitopes are functionally involved in proliferation of neural progenitor cells in the subventricular zone.

Protein glycosylation has received much attention due to its multiple functional roles in physiological and pathophysiological conditions. Paucimannose is a common mannosidic N-glycoepitope in invertebrates and plants but has only recently been detected in vertebrates. Herein, we demonstrate the presence of paucimannosidic epitopes specifically in early postnatal neural progenitor cells (NPCs) between postnatal day 0 and 7 in mouse brain suggesting a possible role in the development of NPCs. Paucimannosidic epitopes were also detected in human glioblastoma cells and human macrophages by immunofluorescence and mass spectrometric analysis. Its expression was significantly increased after proliferation arrest indicating its importance in the regulation of cell proliferation. This hypothesis was further strengthened by reduced cell proliferation after the application of paucimannose-reactive Mannitou antibody into culture medium of growing cells. Most interestingly, this reduction in cell proliferation upon the administration of Mannitou antibody could also be observed in vivo in the subventricular zone of early postnatal mouse brain. Taken together, these observations demonstrate that paucimannosylation directly influences cell proliferation in various vertebrate cell types including early postnatal neural stem cells.

Human adipose-derived mesenchymal stromal cells increase endogenous neurogenesis in the rat subventricular zone acutely after 6-hydroxydopamine lesioning.

BACKGROUND AIMS: In Parkinson's disease (PD), neurogenesis in the subventricular zone (SVZ)-olfactory bulb (OB) axis is affected as the result of the lack of dopaminergic innervations reaching the SVZ. This aberrant network has been related to the hyposmia of PD patients, which is an early diagnostic marker of the disease. Consequently, much interest arose in finding mechanisms to modulate the SVZ-OB axis. Direct modulation of this axis could be achieved by transplantation of mesenchymal stromal cells (MSC), as it has been shown in rat and mouse PD models. However, the neurogenic effect of MSC in PD was thus far only analyzed weeks after transplantation, and little is known about effects immediately after transplantation. METHODS: We assessed the acute neuroprotective and neurogenic effects of adipose-derived MSC transplanted into the rat substantia nigra in the 6-hydroxydopamine model of PD. RESULTS: Three days after transplantation, subventricular neurogenesis was significantly increased in MSC-transplanted versus non-transplanted animals. Most MSC were found in the region of the substantia nigra and the surrounding arachnoid mater, expressing S100ß and brain-derived neurotrophic factor, whereas some MSC showed an endothelial phenotype and localized around blood vessels. CONCLUSIONS: The acute neurogenic effects and neurotrophic factor expression of MSC could help to restore the SVZ-OB axis in PD.

PDGF-responsive progenitors persist in the subventricular zone across the lifespan.

The SVZ (subventricular zone) contains neural stem cells and progenitors of various potentialities. Although initially parsed into A, B, and C cells, this germinal zone is comprised of a significantly more diverse population of cells. Here, we characterized a subset of postnatal PRPs (PDGF-AA-responsive precursors) that express functional PDGFα and ß receptors from birth to adulthood. When grown in PDGF-AA, dissociated neonatal rat SVZ cells divided to produce non-adherent clusters of progeny. Unlike the self-renewing EGF/FGF-2-responsive precursors that produce neurospheres, these PRPs failed to self-renew after three passages; therefore, we refer to the colonies they produce as spheroids. Upon differentiation these spheroids could produce neurons, type 1 astrocytes and oligodendrocytes. When maintained in medium supplemented with BMP-4 they also produced type 2 astrocytes. Using lineage tracing methods, it became evident that there were multiple types of PRPs, including a subset that could produce neurons, oligodendrocytes, and type 1 and type 2 astrocytes; thus some of these PRPs represent a unique population of precursors that are quatropotential. Spheroids also could be generated from the newborn neocortex and they had the same potentiality as those from the SVZ. By contrast, the adult neocortex produced less than 20% of the numbers of spheroids than the adult SVZ and spheroids from the adult neocortex only differentiated into glial cells. Interestingly, SVZ spheroid producing capacity diminished only slightly from birth to adulthood. Altogether these data demonstrate that there are PRPs that persist in the SVZ that includes a unique population of quatropotential PRPs.

Neural and oligodendrocyte progenitor cells: transferrin effects on cell proliferation.

NSC (neural stem cells)/NPC (neural progenitor cells) are multipotent and self-renew throughout adulthood in the SVZ (subventricular zone) of the mammalian CNS (central nervous system). These cells are considered interesting targets for CNS neurodegenerative disorder cell therapies, and understanding their behaviour in vitro is crucial if they are to be cultured prior to transplantation. We cultured the SVZ tissue belonging to newborn rats under the form of NS (neurospheres) to evaluate the effects of Tf (transferrin) on cell proliferation. The NS were heterogeneous in terms of the NSC/NPC markers GFAP (glial fibrillary acidic protein), Nestin and Sox2 and the OL (oligodendrocyte) progenitor markers NG2 (nerve/glia antigen 2) and PDGFRα (platelet-derived growth factor receptor α). The results of this study indicate that aTf (apoTransferrin) is able to increase cell proliferation of SVZ-derived cells in vitro, and that these effects were mediated at least in part by the TfRc1 (Tf receptor 1). Since OPCs (oligodendrocyte progenitor cells) represent a significant proportion of the proliferating cells in the SVZ-derived primary cultures, we used the immature OL cell line N20.1 to show that Tf was able to augment the proliferation rate of OPC, either by adding aTf to the culture medium or by overexpressing rat Tf in situ. The culture medium supplemented with ferric iron, together with aTf, increased the DNA content, while ferrous iron did not. The present work provides data that could have a potential application in human cell replacement therapies for neurodegenerative disease and/or CNS injury that require the use of in vitro amplified NPCs.

Expression of constitutively active FoxO3 in murine forebrain leads to a loss of neural progenitors.

Inactivation of FoxO proteins by phosphorylation is the result of a number of stimuli, including the insulin/IGF pathway. We were interested in the consequence of blunting this pathway by employing transgenic mice with tetracycline-controllable conditional expression of a constitutively active allele of FOXO3 under the control of the forebrain-specific CaMKIIα promoter. Although transgene-expressing mice were viable, brain weight was reduced by 30% in adult animals. Brains showed an isocortex compression with normal cortical layering, and a size reduction in regions known to depend on adult neurogenesis, i.e., the olfactory bulbs and the dentate gyrus. On postnatal activation of the transgene, adult neurogenesis was also severely affected. Investigating the molecular basis of this phenotype, we observed enhanced apoptosis starting from embryonic day E10.5 and a subsequent loss of progenitors in the ventricular/subventricular zones, but not in the isocortex or the striatum of adult mice. The enhanced apoptosis was accompanied by increased expression of PIK3IP1, which we identified as a direct transcriptional target of FOXO3. Transfection of Pik3ip1 into differentiating neural progenitors resulted in a significant reduction of viable cells. We therefore conclude that neural progenitors are particularly vulnerable to FOXO3-induced apoptosis, which is mediated by PIK3IP1, a negative PI3 kinase regulator.

Alteration of brain volume in IL-6 overexpressing mice related to autism.

Abnormal neuroimmune responses have been reported to be associated with autism and could be appropriate targets for pharmacologic intervention. Our previous studies showed that neuroimmune factor, interleukin (IL)-6, was significantly elevated in the fontal cortex and cerebellum of autistic subjects. The IL-6 overexpressing mice displayed several autism-like features as well as an abnormal dendritic spine morphology and synaptic function. The purpose of this study was to examine the volumetric differences in the brain of IL-6 overexpressing mice and compare with corresponding control mice using magnetic resonance imaging. Here we show that IL-6 overexpressing mice display an increase in the total brain volume. In addition, the lateral ventricle is also enlarged in the IL-6 overexpressing mice. The brain structures surrounding the lateral ventricle were squeezed and deformed from the normal location. These results indicate that IL-6 elevation in the brain could mediate neuroanatomical abnormalities. Taking together with our previous findings, a mechanism by which IL-6 may be involved in the pathogenesis of autism is proposed.

Nuclear factor κB activation impairs ependymal ciliogenesis and links neuroinflammation to hydrocephalus formation.

Hydrocephalus formation is a frequent complication of neuropathological insults associated with neuroinflammation. However, the mechanistic role of neuroinflammation in hydrocephalus development is unclear. We have investigated the function of the proinflammatory acting inhibitor of κB kinase (IKK)/nuclear factor κB (NF-κB) signaling system in neuroinflammatory processes and generated a novel mouse model that allows conditional activation of the IKK/NF-κB system in astrocytes. Remarkably, NF-κB activation in astrocytes during early postnatal life results in hydrocephalus formation and additional defects in brain development. NF-κB activation causes global neuroinflammation characterized by a strong, astrocyte-specific expression of proinflammatory NF-κB target genes as well as a massive infiltration and activation of macrophages. In this animal model, hydrocephalus formation is specifically induced during a critical time period of early postnatal development, in which IKK/NF-κB-induced neuroinflammation interferes with ependymal ciliogenesis. Our findings demonstrate for the first time that IKK/NF-κB activation is sufficient to induce hydrocephalus formation and provides a potential mechanistic explanation for the frequent association of neuroinflammation and hydrocephalus formation during brain development, namely impairment of ependymal cilia formation. Therefore, our study might open up new perspectives for the treatment of certain types of neonatal and childhood hydrocephalus associated with hemorrhages and infections.

A role for mDia, a Rho-regulated actin nucleator, in tangential migration of interneuron precursors.

In brain development, distinct types of migration, radial migration and tangential migration, are shown by excitatory and inhibitory neurons, respectively. Whether these two types of migration operate by similar cellular mechanisms remains unclear. We examined neuronal migration in mice deficient in mDia1 (also known as Diap1) and mDia3 (also known as Diap2), which encode the Rho-regulated actin nucleators mammalian diaphanous homolog 1 (mDia1) and mDia3. mDia deficiency impaired tangential migration of cortical and olfactory inhibitory interneurons, whereas radial migration and consequent layer formation of cortical excitatory neurons were unaffected. mDia-deficient neuroblasts exhibited reduced separation of the centrosome from the nucleus and retarded nuclear translocation. Concomitantly, anterograde F-actin movement and F-actin condensation at the rear, which occur during centrosomal and nuclear movement of wild-type cells, respectively, were impaired in mDia-deficient neuroblasts. Blockade of Rho-associated protein kinase (ROCK), which regulates myosin II, also impaired nuclear translocation. These results suggest that Rho signaling via mDia and ROCK critically regulates nuclear translocation through F-actin dynamics in tangential migration, whereas this mechanism is dispensable in radial migration.

Netrin1 is required for neural and glial precursor migrations into the olfactory bulb.

Netrin1 (NTN1) deficiency in mouse brain causes defects in axon guidance and cell migration during embryonic development. Here we show that NTN1 is required for olfactory bulb (OB) development at late embryogenesis and at early postnatal stages to facilitate the accumulation of proper numbers of granular and glomerular neuron subtypes and oligodendrocytes into the OB. In addition to the analysis of Ntn1-/- mice we made tissue and neurosphere cultures to clarify the role of NTN1 in the anterior forebrain. We propose that a subset of neural progenitors/precursors requires NTN1 to efficiently enter the rostral migratory stream to migrate into the OB. The analysis of postnatal Ntn1-/- OBs revealed a reduction of specific types of interneurons which have been shown to originate from particular subregions of the lateral ventricle walls. Based on Ntn1 expression in ventral parts of the ventricle walls, we observed a decrease in the mainly ventrally derived type II interneurons that express calcium-binding proteins calretinin and calbindin. Instead, no change in the numbers of dorsally derived tyrosine hydroxylase expressing interneurons was detected. In addition to the specific reduction of type II interneurons, our results indicate that NTN1 is required for oligodendroglial migration into the OB. Furthermore, we characterised the Ntn1 expressing subpopulation of neurosphere-forming cells from embryonic and adult brain as multipotent and self-renewing. However, NTN1 is dispensable for the proliferation of neurosphere forming progenitor cells and for their differentiation.

Newborn frontal horn cysts: cause for concern?

OBJECTIVE: To document the incidence, natural history and compare neurodevelopmental outcome of newborns with and without frontal horn cysts (FHC). STUDY DESIGN: This was a case-control study. Newborns with and without FHC were identified and matched for demographics and worst cranial ultrasound scan (CUS) findings. Neurodevelopmental outcome was assessed at 18 to 24 months. RESULT: A total of 30 FHC cases were identified from medical imaging database. Twenty-five cases occurred in preterm 32 weeks gestation with an incidence of 1% (25 of 2340). The diagnosis was made on the initial CUS in 28 cases. The cyst size and number varied from 1 to 18 mm and 1 to 6 respectively with no change noted on repeat CUS during hospital stay. Neurodevelopmental outcomes were not statistically significantly different between the groups. CONCLUSION: FHC are not uncommon in the newborn period. They appear to be benign with no impact on neurodevelopmental outcome. This information is vital for counseling parents of infants with FHC.

Use of tissue glue to prevent collapse of the cortical mantle during and after cranial surgery in children: a technical note.

INTRODUCTION: Young children with significant ventricular dilatation or large intracranial fluid spaces often have a very thin cortical mantle as a result of persistently raised intracranial pressure. This rim of cortex has a tendency to fall away from the dura into the cavity during and after intracranial surgery, due to the lack of support, once the pressure in the fluid cavity has been reduced. This can lead to tearing of cortical bridging veins and the formation of post-operative subdural haematomas. METHODS: We describe a simple technique that attempts to prevent this phenomenon occurring using tissue glue. Once the craniotomy has been performed and the dura has been formally opened, tissue glue is applied to the underside of the dura around the edge of the wound, prior to corticotomy. RESULTS AND CONCLUSION: This results in the cortical mantle adhering to the undersurface of the dura and prevents the mantle from falling into the cavity either during the procedure or post-operatively.

Cellular transfer of macromolecules across the developing choroid plexus of Monodelphis domestica.

Choroid plexus epithelial cells secrete cerebrospinal fluid (CSF) and transfer molecules from blood into CSF. Tight junctions between choroidal epithelial cells are functionally effective from early in development: the route of transfer is suggested to be transcellular. Routes of transfer for endogenous and exogenous plasma proteins and dextrans were studied in Monodelphis domestica (opossum). Pups at postnatal (P) days 1-65 and young adults were injected with biotinylated dextrans (3-70 kDa) and/or foetal protein fetuin. CSF, plasma and brain samples were collected from terminally anaesthetized animals. Choroid plexus cells containing plasma proteins were detected immunocytochemically. Numbers of plasma protein-positive epithelial cells increased to adult levels by P28, but their percentage of plexus cells declined. Numbers of cells positive for biotinylated probes increased with age, while their percentage remained constant. Colocalization studies showed specificity for individual proteins in some epithelial cells. Biotinylated probes and endogenous proteins colocalized in about 10% of cells in younger animals, increasing towards 100% by adulthood. Injections of markers into the ventricles demonstrated that protein is transferred only from blood into CSF, whereas dextrans pass in both directions. These results indicate that protein and lipid-insoluble markers are transferred by separate mechanisms present in choroid plexuses from the earliest stage of brain development, and transfer of proteins from plasma across choroid plexus epithelial cells contributes to the high protein concentration in CSF in the immature brain.

A comparison of behavioural and histological outcomes of periventricular injection of ibotenic acid in neonatal rats at postnatal days 5 and 7.

Periventricular white matter injury (PVWMI) in premature babies is a major cause of cerebral palsy. Excitotoxic ibotenic acid (IBA) causes PVWMI-like lesions when injected into the white matter of neonatal rodents, however, whether it causes sensorimotor behavioural deficits that could also model cerebral palsy has not been tested. We compared IBA injection at postnatal day 7 (P7) when rodent development is equivalent to the stage of human corticospinal maturation vulnerable to PVWMI and P5 when rodent oligodendrocyte precursor cells are more vulnerable to excitotoxicity. IBA or saline were injected bilaterally into white matter between the external angle of the lateral ventricle and the forelimb sensorimotor cortex. By P14, IBA injection at P5 caused localised hypomyelination and cyst formation in this region, although cortical grey matter remained intact. Treatment at P7 produced less hypomyelination, but more widespread loss of neurofilament immunoreactivity. From P28 onwards, corticospinal function was assessed by testing reaching and retrieval of food rewards. All rats improved with age, but there was a consistent and significant difference between IBA treated rats (P5 and P7) and controls. Histological examination following testing revealed no difference in forebrain cross-sectional area but that the lateral ventricles were significantly larger in IBA treated animals than controls, especially at P7. P5 treatment caused a significantly reduced density of anti-myelin immunoreactivity in the corpus callosum compared to the anterior commissure that was not consistently seen following P7 treatment. We conclude that IBA induced lesions provide a satisfactory model of PVWMI, particularly when made at P5.