Cell death, axonal damage, and cell birth in the immature rat brain following induction of hydrocephalus

Memantine associated with ventricular-subcutaneous shunt promotes behavioral improvement, reduces reactive astrogliosis and cell death in juvenile hydrocephalic rats

Hydrocephalus is defined as the accumulation of cerebrospinal fluid in the brain ventricles. The usual treatment of hydrocephalus is surgical (shunt), but not all patients can undergo treatment immediately after diagnosis. Thus, neuroprotective measures were tested to minimize the tissue damage involved. Memantine is a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, which has shown a neuroprotective action in neurodegenerative diseases. This study aimed to evaluate the neuroprotective response of memantine in animals treated with or without a ventricular-subcutaneous shunt. Seven-day-old male Wistar rats induced by intracisternal injection of kaolin were used, divided into five groups: intact control (n=10), hydrocephalic (n=10), hydrocephalic treated with memantine (20mg/kg/day) (n=10), hydrocephalic treated with shunt (n=10), hydrocephalic treated with shunt and memantine (20mg/kg/day) (n=10). Memantine administration was started on the day after hydrocephalus induction and continued until the last day of the experimental period, totaling 21 consecutive days of drug application. The CSF shunt surgery was performed seven days after hydrocephalus induction. Behavioral tests (open field, and modified Morris water maze), histological, and immunohistochemical evaluations were performed. Treatment with memantine resulted in significant improvement (p<0.05) in sensorimotor development, preservation of spatial memory, reduction of astrocytic reaction in the corpus callosum, cortex, and germinal matrix. When associated with the shunt, it has also been shown to reduce the cell death cascade. It is concluded that memantine is a promising adjuvant drug with beneficial potential for the treatment of lesions secondary to hydrocephalus.

The Anti-Inflammatory Agent Bindarit Attenuates the Impairment of Neural Development through Suppression of Microglial Activation in a Neonatal Hydrocephalus Mouse Model

Neonatal hydrocephalus presents with various degrees of neuroinflammation and long-term neurologic deficits in surgically treated patients, provoking a need for additional medical treatment. We previously reported elevated neuroinflammation and severe periventricular white matter damage in the progressive hydrocephalus (prh) mutant which contains a point mutation in the Ccdc39 gene, causing loss of cilia-mediated unidirectional CSF flow. In this study, we identified cortical neuropil maturation defects such as impaired excitatory synapse maturation and loss of homeostatic microglia, and swimming locomotor defects in early postnatal prh mutant mice. Strikingly, systemic application of the anti-inflammatory small molecule bindarit significantly supports healthy postnatal cerebral cortical development in the prh mutant. While bindarit only mildly reduced the ventricular volume, it significantly improved the edematous appearance and myelination of the corpus callosum. Moreover, the treatment attenuated thinning in cortical Layers II-IV, excitatory synapse formation, and interneuron morphogenesis, by supporting the ramified-shaped homeostatic microglia from excessive cell death. Also, the therapeutic effect led to the alleviation of a spastic locomotor phenotype of the mutant. We found that microglia, but not peripheral monocytes, contribute to amoeboid-shaped activated myeloid cells in prh mutants' corpus callosum and the proinflammatory cytokines expression. Bindarit blocks nuclear factor (NF)-kB activation and its downstream proinflammatory cytokines, including monocyte chemoattractant protein-1, in the prh mutant. Collectively, we revealed that amelioration of neuroinflammation is crucial for white matter and neuronal maturation in neonatal hydrocephalus. Future studies of bindarit treatment combined with CSF diversion surgery may provide long-term benefits supporting neuronal development in neonatal hydrocephalus.SIGNIFICANCE STATEMENT In neonatal hydrocephalus, little is known about the signaling cascades of neuroinflammation or the impact of such inflammatory insults on neural cell development within the perinatal cerebral cortex. Here, we report that proinflammatory activation of myeloid cells, the majority of which are derived from microglia, impairs periventricular myelination and cortical neuronal maturation using the mouse prh genetic model of neonatal hydrocephalus. Administration of bindarit, an anti-inflammatory small molecule that blocks nuclear factor (NF)-kB activation, restored the cortical thinning and synaptic maturation defects in the prh mutant brain through suppression of microglial activation. These data indicate the potential therapeutic use of anti-inflammatory reagents targeting neuroinflammation in the treatment of neonatal hydrocephalus.

The association of Edaravone with shunt surgery improves behavioral performance, reduces astrocyte reaction and apoptosis, and promotes neuroprotection in young hydrocephalic rats

The neuroprotective effect of Edaravone in young hydrocephalic rats associated with a CSF derivation system was evaluated. The drug has already been shown to be beneficial in experimental hydrocephalus, but the combination of this drug with shunt surgery has not yet been investigated. Fifty-seven-day-old Wistar rats submitted to hydrocephalus by injection of kaolin in the cisterna magna were used and divided into five groups: control (n = 10), hydrocephalic (n = 10), hydrocephalic treated with Edaravone (20 mg/kg/day) (n = 10), hydrocephalic treated with shunt (n = 10) and hydrocephalic treated with shunt and Edaravone (n = 10). Administration of the Edaravone was started 24 h after hydrocephalus induction (P1) and continued until the experimental endpoint (P21). The CSF shunt surgery was performed seven days after hydrocephalus induction (P7). Open-field tests, histological evaluation by hematoxylin and eosin, immunohistochemistry by Caspase-3 and GFAP, and ELISA biochemistry by GFAP were performed. Edaravone reduced reactive astrogliosis in the corpus callosum and germinal matrix (p < 0.05). When used alone or associated with CSF shunt surgery, the drug decreased the cell death process (p < 0.0001) and improved the morphological aspect of the astroglia (p < 0.05). The results showed that Edaravone associated with CSF bypass surgery promotes neuroprotection in young hydrocephalic rats by reducing reactive astrogliosis and decreasing cell death.

Long-term risk of shunt failure after brain tumor surgery

Long-term risks and survival times of ventriculoperitoneal (VP) shunts implanted due to hydrocephalus (HC) after craniotomy for brain tumors are largely unknown. The aim of this study was to establish the overall VP shunt survival rates during a decade after shunt insertion and to determine risks of shunt failure after brain tumor surgery in the long-term period. In this population-based cohort from a well-defined geographical region, all adult patients (> 18 years) from 2004 to 2013 who underwent craniotomies for intracranial tumors leading to VP shunt dependency were included. Our brain tumor database was cross-linked to procedure codes for shunt surgery (codes AAF) to extract brain tumor patients who became VP shunt dependent after craniotomy. The VP shunt survival time, i.e. the shunt longevity, was calculated from the day of shunt insertion after brain tumor surgery until the day of its failure. A total of 4174 patients underwent craniotomies, of whom 85 became VP shunt dependent (2%) afterwards. Twenty-eight patients (33%) had one or more shunt failures during their long-term follow-up, yielding 1-, 5-, and 10-year shunt success rates of 77%, 71%, and 67%, respectively. Patient age, sex, tumor location, primary/repeat craniotomy, placement of external ventricular drainage (EVD), ventricular entry, post-craniotomy hemorrhage, post-shunting meningitis/infection, and multiple shunt revisions were not statistically significant risk factors for shunt failure. Median shunt longevity was 457.5 days and 21.5 days for those with and without pre-craniotomy HC, respectively (p < 0.01). This study can serve as benchmark for future studies.

Identification of key molecular biomarkers involved in reactive and neurodegenerative processes present in inherited congenital hydrocephalus

BACKGROUND

Periventricular extracellular oedema, myelin damage, inflammation, and glial reactions are common neuropathological events that occur in the brain in congenital hydrocephalus. The periventricular white matter is the most affected region. The present study aimed to identify altered molecular and cellular biomarkers in the neocortex that can function as potential therapeutic targets to both treat and evaluate recovery from these neurodegenerative conditions. The hyh mouse model of hereditary hydrocephalus was used for this purpose.

METHODS

The hyh mouse model of hereditary hydrocephalus (hydrocephalus with hop gait) and control littermates without hydrocephalus were used in the present work. In tissue sections, the ionic content was investigated using energy dispersive X-ray spectroscopy scanning electron microscopy (EDS-SEM). For the lipid analysis, matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) was performed in frozen sections. The expression of proteins in the cerebral white matter was analysed by mass spectrometry. The oligodendrocyte progenitor cells (OPCs) were studied with immunofluorescence in cerebral sections and whole-mount preparations of the ventricle walls.

RESULTS

High sodium and chloride concentrations were found indicating oedema conditions in both the periventricular white matter and extending towards the grey matter. Lipid analysis revealed lower levels of two phosphatidylinositol molecular species in the grey matter, indicating that neural functions were altered in the hydrocephalic mice. In addition, the expression of proteins in the cerebral white matter revealed evident deregulation of the processes of oligodendrocyte differentiation and myelination. Because of the changes in oligodendrocyte differentiation in the white matter, OPCs were also studied. In hydrocephalic mice, OPCs were found to be reactive, overexpressing the NG2 antigen but not giving rise to an increase in mature oligodendrocytes. The higher levels of the NG2 antigen, diacylglycerophosphoserine and possibly transthyretin in the cerebrum of hydrocephalic hyh mice could indicate cell reactions that may have been triggered by inflammation, neurocytotoxic conditions, and ischaemia.

CONCLUSION

Our results identify possible biomarkers of hydrocephalus in the cerebral grey and white matter. In the white matter, OPCs could be reacting to acquire a neuroprotective role or as a delay in the oligodendrocyte maturation.

Risk of early failure of VP shunts implanted for hydrocephalus after craniotomies for brain tumors in adults

Risks and survival times of ventriculoperitoneal (VP) shunts implanted due to hydrocephalus after craniotomies for brain tumors are largely unknown. The purpose of this study was to determine the overall timing of VP shunting and its failure after craniotomy for brain tumors in adults. The authors also wished to explore risk factors for early VP shunt failure (within 90 days). A population-based consecutive patient cohort of all craniotomies for intracranial tumors leading to VP shunt dependency in adults (> 18 years) from 2004 to 2013 was studied. Patients with pre-existing VP shunts prior to craniotomy were excluded. The survival time of VP shunts, i.e., the shunt longevity, was calculated from the day of shunt insertion post-craniotomy for a brain tumor until the day of shunt revision requiring replacement or removal of the shunt system. Out of 4774 craniotomies, 85 patients became VP shunt-dependent (1.8% of craniotomies). Median time from craniotomy to VP shunting was 1.9 months. Patients with hydrocephalus prior to tumor resection (N = 39) had significantly shorter time to shunt insertion than those without (N = 46) (p < 0.001), but there was no significant difference with respect to early shunt failure. Median time from shunt insertion to shunt failure was 20 days (range 1–35). At 90 days, 17 patients (20%) had confirmed shunt failure. Patient age, sex, tumor location, primary/secondary craniotomy, extra-axial/intra-axial tumor, ventricular entry, post-craniotomy bleeding, and infection did not show statistical significance. The risk of early shunt failure (within 90 days) of shunts after craniotomies for brain tumors was 20%. This study can serve as benchmark for future studies.

Neurobehavioural changes and morphological study of cerebellar purkinje cells in kaolin induced hydrocephalus

Cerebellar abnormalities are commonly associated with hydrocephalus. However, the effect of hydrocephalus on the otherwise normal cerebellum has been largely neglected. This study assesses the morphological changes in the Purkinje cells in relation to cerebellar dysfunction observed in juvenile hydrocephalic rats. Fifty-five three-week old albino Wistar rats were used, hydrocephalus was induced by intracisternal injection of kaolin (n = 35) and others served as controls (n = 20). Body weight measurements, hanging wire, negative geotaxis, and open field tests were carried out at the onset and then weekly for 4 weeks, rats were killed, and their cerebella processed for Hematoxylin and Eosin, Cresyl violet and Golgi staining. Qualitative and quantitative studies were carried out; quantitative data were analyzed using two-way ANOVA and independent T tests at p < 0.05. Hydrocephalic rats weighed less than controls (p = 0.0247) but their cerebellar weights were comparable. The hydrocephalic rats had a consistently shorter latency to fall in the hanging wire test (F(4,112) = 18.63; p < 0.0001), longer latency to turn in the negative geotaxis test (F(4,112) = 22.2; p < 0.0001), and decreased horizontal (F(4,112) = 4.172, p = 0.0035) and vertical movements (F(4,112) = 4.397; p = 0.0024) in the open field test than controls throughout the 4 weeks post-induction. Cellular compression in the granular layer, swelling of Purkinje cells with vacuolations, reduced dendritic arborization and increased number of pyknotic Purkinje cells were observed in hydrocephalic rats. Hydrocephalus caused functional and morphological changes in the cerebellar cortex. Purkinje cell loss, a major pathological feature of hydrocephalus, may be responsible for some of the motor deficits observed in this condition.

Fetal brain damage in congenital hydrocephalus

BACKGROUND

Congenital hydrocephalus (HCP) is a developmental brain disorder characterized by the abnormal accumulation of cerebrospinal fluid within the ventricles. It is caused by genetic and acquired factors that start during early embryogenesis with disruption of the neurogerminal areas. As might be expected, early-onset hydrocephalus alters the process of brain development leading to irreparable neurological deficit. A primary alteration of the ependyma/neural stem cells (affecting vesicle trafficking and abnormal cell junctions) leads to its loss or denudation and translocation of neural progenitor cells (NPCs) and neural stem cells (NSCs) into the cerebrospinal fluid (CSF). Under these abnormal conditions, morphological and functional processes, underlying the concept of astroglial reaction, are initiated in an attempt to recover homeostasis in the periventricular zone. This astroglial reaction includes astrocyte hypertrophy, hyperplasia, and development of a new layer with reorganized functional features that resemble the ependyma. Despite decades of research, there is a lack of information concerning the biological basis of the brain abnormalities that are associated with HCP.

DISCUSSION

The present review of current literature discusses the neuropathological changes during gestation following the onset of congenital hydrocephalus and the unanswered questions into the pathophysiology of the disease. A better understanding of those missing points might help create novel therapeutic strategies that can reverse or even prevent the ultimate neurological impairment that affects this population and improve long-term clinical outcome.

Kaolin-induced hydrocephalus causes acetylcholinesterase activity dysfunction following hypothalamic damage in infant rats

In hydrocephalus, the progressive accumulation of cerebrospinal fluid (CSF) causes dilatation of the lateral ventricles affecting the third ventricle and diencephalic structures such as the hypothalamus. These structures play a key role in the regulation of several neurovegetative functions by the production of the hormones. Since endocrine disturbances are commonly observed in hydrocephalic children, we investigated the impact of progressive ventricular dilation on the hypothalamus of infant rats submitted to kaolin-induced hydrocephalus. Seven-day-old infant rats were submitted to hydrocephalus induction by kaolin 20% injection method. After 14 days, the animals were decapitated and brain was collected to analyze mitochondrial function, neuronal activity by acetylcholinesterase (AChE) enzyme, oxidative damage, glial activation, and, neurotransmission-related proteins and anti-apoptotic processes in the hypothalamus. The hydrocephalic animals showed reduction in respiratory rates in the States of phosphorylation (P < 0.01) and non-phosphorylation (P < 0.05); increase in AChE activity in both the cytosol (P < 0.05) and the membrane (P < 0.01); decrease in synaptophysin (P < 0.05) and Bcl-2 (P < 0.05) contents and; increase in protein carbonyl (P < 0.01), GFAP (P < 0.01) and Iba-1 (P < 0.05) levels. The results demonstrate that ventricular dilation causes hypothalamic damage characterized by cholinergic dysfunction and suggests further investigation of the synthesis and secretion of hormones to generate new approaches and to assist in the treatment of hydrocephalic patients with hormonal alterations.

Impaired neural differentiation and glymphatic CSF flow in the Ccdc39 rat model of neonatal hydrocephalus: genetic interaction with L1cam

Neonatal hydrocephalus affects about one child per 1000 births and is a major congenital brain abnormality. We previously discovered a gene mutation within the coiled-coil domain-containing 39 (Ccdc39) gene, which causes the progressive hydrocephalus (prh) phenotype in mice due to lack of ependymal-cilia-mediated cerebrospinal fluid (CSF) flow. In this study, we used CRISPR/Cas9 to introduce the Ccdc39 gene mutation into rats, which are more suitable for imaging and surgical experiments. The Ccdc39^prh/prh mutants exhibited mild ventriculomegaly at postnatal day (P)5 that progressed into severe hydrocephalus by P11 (P<0.001). After P11, macrophage and neutrophil invasion along with subarachnoid hemorrhage were observed in mutant brains showing reduced neurofilament density, hypomyelination and increased cell death signals compared with wild-type brains. Significantly more macrophages entered the brain parenchyma at P5 before hemorrhaging was noted and increased expression of a pro-inflammatory factor (monocyte chemoattractant protein-1) was found in the cortical neural and endothelial cells in the mutant brains at P11. Glymphatic-mediated CSF circulation was progressively impaired along the middle cerebral artery from P11 as mutants developed severe hydrocephalus (P<0.001). In addition, Ccdc39^prh/prh mutants with L1 cell adhesion molecule (L1cam) gene mutation, which causes X-linked human congenital hydrocephalus, showed an accelerated early hydrocephalus phenotype (P<0.05-0.01). Our findings in Ccdc39^prh/prh mutant rats demonstrate a possible causal role of neuroinflammation in neonatal hydrocephalus development, which involves impaired cortical development and glymphatic CSF flow. Improved understanding of inflammatory responses and the glymphatic system in neonatal hydrocephalus could lead to new therapeutic strategies for this condition.

This article has an associated First Person interview with the joint first authors of the paper.

Summary: Glymphatic CSF circulation and development of the cerebral cortex are impaired in our new genetic rat model of neonatal hydrocephalus with the onset of parenchymal inflammation and hemorrhage.

A Distinct Metabolite Profile Correlates with Neurodegenerative Conditions and the Severity of Congenital Hydrocephalus

In congenital hydrocephalus, cerebrospinal fluid accumulation is associated with increased intracranial pressure (ICP), ischemia/hypoxia, metabolic impairment, neuronal damage, and astrocytic reaction. The aim of this study was to identify whether a metabolite profile revealing tissue responses according to the severity of hydrocephalus can be detected. The hyh mutant mouse used for this study exhibits 2 different forms of hydrocephalus, severe and moderate. In a comprehensive investigation into the 2 progressions of hydrocephalus, mice with severe hydrocephalus were found to have higher ICP and astrocytic reaction. Several metabolites from the mouse brain cortex were analyzed with 1H high-resolution magic angle spinning nuclear magnetic resonance (1H HR-MAS NMR) spectroscopy. A differential profile for metabolites including glutamate and glutamine was found to correlate with the severity of hydrocephalus and can be explained due to differential astrocytic reactions, neurodegenerative conditions, and the presence of ischemia. The glutamate transporter EAAT2 and the metabolite taurine were found to be key histopathological markers of affected parenchymata. In conclusion, a differential metabolite profile can be detected according to the severity of hydrocephalus and associated ICP and therefore can be used to monitor the efficacy of experimental therapies.

Feasibility of fast brain diffusion MRI to quantify white matter injury in pediatric hydrocephalus

OBJECTIVE

Traditionally, diffusion MRI (dMRI) has been performed in parallel with high-resolution conventional MRI, which requires long scan times and may require sedation or general anesthesia in infants and young children. Conversely, fast brain MRI permits image acquisition without the need for sedation, although its short pulse sequences, susceptibility to motion artifact, and contrast resolution have limited its use to assessing ventricular size or major structural variations. Here, the authors demonstrate the feasibility of leveraging a 3-direction fast brain MRI protocol to obtain reliable dMRI measures.

METHODS

Fast brain MRI with 3-direction dMRI was performed in infants and children before and after hydrocephalus treatment. Regions of interest in the posterior limbs of the internal capsules (PLICs) and the genu of the corpus callosum (gCC) were drawn on diffusion-weighted images, and mean diffusivity (MD) data were extracted. Ventricular size was determined by the frontal occipital horn ratio (FOHR). Differences between and within groups pre- and posttreatment, and FOHR-MD correlations were assessed.

RESULTS

Of 40 patients who met inclusion criteria (median age 27.5 months), 15 (37.5%), 17 (42.5%), and 8 (20.0%) had posthemorrhagic hydrocephalus (PHH), congenital hydrocephalus (CH), or no intracranial abnormality (controls), respectively. A hydrocephalus group included both PHH and CH patients. Prior to treatment, the FOHR (p < 0.001) and PLIC MD (p = 0.027) were greater in the hydrocephalus group than in the controls. While the mean gCC MD in the hydrocephalus group (1.10 × 10-3 mm2/sec) was higher than that of the control group (0.98), the difference was not significant (p = 0.135). Following a median follow-up duration of 14 months, decreases in FOHR, PLIC MD, and gCC MD were observed in the hydrocephalus group and were similar to those in the control group (p = 0.107, p = 0.702, and p = 0.169, respectively). There were no correlations identified between FOHR and MDs at either time point.

CONCLUSIONS

The utility of fast brain MRI can be extended beyond anatomical assessments to obtain dMRI measures. A reduction in PLIC and gCC MD to levels similar to those of controls was observed within 14 months following shunt surgery for hydrocephalus in PHH and CH infants. Further studies are required to assess the role of fast brain dMRI for assessing clinical outcomes in pediatric hydrocephalus patients.

Establishing reproducible predictors of cerebellar mutism syndrome based on pre-operative imaging

PURPOSE

To establish some explicit, feasible, and reproducible predictors for CMS.

MATERIALS AND METHODS

This study was a retrospective case study. Data were obtained from 82 patients with medulloblastoma at a single center, Beijing Tiantan Hospital. Based on medical records, we created two independent samples: the CMS group comprising 23 patients and the non-CMS group comprising 23 patients. Pre-operative imaging was studied by performing quantitative assessments of specific indicators.

RESULTS

The CMS group showed greater differences in pre-operative imaging data with the non-CMS group. The A_axi/d_axi ratio in pre-operative MR imaging captured in the axial plane was used to quantify the compression of the cerebellum and brainstem, and significant differences were observed between the CMS group and non-CMS group (p = 0.0002). In the sagittal plane, D_sag*d_sag was used to quantify the area of the tumor that invaded the brainstem, and significant differences were observed between the two groups (p = 0.0003). In the coronal plane, A_cor/d_cor was used to quantify the compression of the upper functional brain region, and significant differences were noted between the two groups (p = 0.0219). Additionally, Evans' index was introduced to quantify the degree of hydrocephalus. The CMS group tended to show an increased Evans' index (p = 0.0027).

CONCLUSION

Based on pre-operative imaging data, some reproducible predictors, such as A_axi/d_axi, D_sag*d_sag, A_cor/d_cor, and Evans' index, were established.

Dendritic and Synaptic Degeneration in Pyramidal Neurons of the Sensorimotor Cortex in Neonatal Mice With Kaolin-Induced Hydrocephalus

Obstructive hydrocephalus is a brain disorder in which the circulation of cerebrospinal fluid (CSF) is altered in a manner that causes expansion of fluid-filled intracranial compartments particularly the ventricles. The pyramidal neurons of the sensorimotor cortex are excitatory in nature and their dendritic spines are targets of excitatory synapses. This study evaluated the effect of hydrocephalus on dendritic arborization and synaptic structure of the pyramidal neurons of the sensorimotor cortex of neonatal hydrocephalic mice. Sterile kaolin suspension (0.01 ml of 250 mg/mL) was injected intracisternally into day old mice. Control animals mice received sham injections. Pups were weighed and sacrificed on postnatal days (PND) 7, 14 and 21. Fixed brain tissue blocks were silver impregnated using a modified Golgi staining technique and immunolabeled with synaptophysin to determine dendritic morphology and synaptic integrity respectively. Data were analyzed using ANOVA at α 0.05. Golgi staining revealed diminished arborization of the basal dendrites and loss of dendritic spines in the pyramidal neurons of hydrocephalic mice. Compared to age-matched controls, there was a significant reduction in the percentage immunoreactivity of anti-synaptophysin in hydrocephalic mice on PND 7 (14.26 ± 1.91% vs. 62.57 ± 9.40%), PND 14 (4.19 ± 1.57% vs. 93.01 ± 1.66%) and PND 21 (17.55 ± 2.76% vs. 99.11 ± 0.63%) respectively. These alterations suggest impaired neuronal connections that are essential for the development of cortical circuits and may be the structural basis of the neurobehavioral deficits observed in neonatal hydrocephalus.

Behavioral and Biochemical Features of the Course and Surgical Treatment of Experimental Obstructive Hydrocephalus in Young Rats

INTRODUCTION

Hydrocephalus is a multifactorial disease, affecting the dynamics of cerebrospinal fluid (CSF) and leading to severe neurological impairment in children; in spite of the recent advances in hydrocephalus research, it has many physiopathological aspects that still remain poorly understood, especially after treatment.

OBJECTIVES

To analyze the clinical, radiological, histopathological, and biochemical aspects of kaolin-induced hydrocephalus in an experimental model, both in the acute phase and after shunt treatment, by means of behavioral tests, magnetic resonance imaging (MRI) scans, histopathological studies, and level of inflammatory interleukins in the CSF.

METHODS

Seven-day-old Wistar rats were used and subdivided into three subgroups: treated hydrocephalic (n = 24), untreated hydrocephalic (n = 17), and controls (n = 5). The hydrocephalic groups underwent cisternal injection of 15% kaolin for induction of hydrocephalus at 7 days of age. The treated group was submitted to a ventricular-subcutaneous shunt (VSCS) 1 week after induction. All animals were euthanized at 21 days of age. They underwent motor function and memory testing as well as brain MRI scans. Histopathological analysis for glial fibrillary acidic protein and Ki-67 was done, and CSF was collected for measurement of IL-1β, IL-6, and TNF-α.

RESULTS

The average time to reach the water maze platform was highest in the untreated hydrocephalic group. The magnetization transfer rates were 37.21 and 33.76 before and after shunting, respectively. The mean astrocyte counts were 2.45, 1.36, and 90.5 for shunted, untreated, and control animals, respectively. The mean CSF IL-1β concentrations were 62.3 and 249.6 pg/mL, the average IL-6 levels were 104.2 and 364.7 pg/mL, and the average TNF-α values were 4.9 and 170.5 pg/mL for the treated hydrocephalic group and the untreated group, respectively.

CONCLUSIONS

Pups treated with a CSF shunt showed better performance on memory tests. VSCS did not revert demyelination caused by hydrocephalus. Likewise, reactive astrocytosis and cell proliferation over the germinal matrix were not reversed after shunting. Hydrocephalic animals had raised levels of inflammatory interleukins, which returned to normal after treatment.

Comprehensive analysis of differentially expressed profiles of long non-coding RNAs and messenger RNAs in kaolin-induced hydrocephalus

BACKGROUNDS

The pathophysiology of hydrocephalus induced brain damage remains unclear. Long non-coding RNAs (lncRNAs) have been demonstrated to be implicated in many central nervous system diseases. However, the roles of lncRNAs in hydrocephalus injury are poorly understood.

METHODS

The present study depicted the expression profiles of lncRNAs and messenger RNAs (mRNAs) in C57BL/6 mice with kaolin-induced hydrocephalus and saline controls using high-throughput RNA sequencing. Afterward, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to identify potential targets that correlated with hydrocephalus. In addition, co-expression networks and cis- and trans-regulation were predicted using bioinformatics methods. Finally, representative lncRNAs and mRNAs were further validation using quantitative real-time polymerase chain reaction.

RESULTS

A total of 1575 lncRNAs and 1168 mRNAs were differentially expressed (DE) in hydrocephalus. GO and KEGG analyses indicated several immune and inflammatory response-associated pathways may be important in the hydrocephalus. Besides, functional enrichment analysis based on co-expression network showed several similar pathways, such as chemokine signaling pathway, phagosome, MAPK signaling pathway and complement and coagulation cascade. Cis-regulation prediction revealed 5 novel lncRNAs might regulate their nearby coding genes, and trans-regulation revealed several lncRNAs participate in pathways regulated by transcription factors, including BPTF, FOXM1, NR5A2, P2RX5, and NR6A1.

CONCLUSIONS

In conclusion, our results provide candidate genes involved in hydrocephalus and suggest a new perspective on the modulation of lncRNAs in hydrocephalus.

Acupuncture at ST36 exerts neuroprotective effects via inhibition of reactive astrogliosis in infantile rats with hydrocephalus

BACKGROUND

Acupuncture has been associated with improved cerebral circulation, analgesia, neuromodulatory function and neurogenesis. In particular, acupuncture at ST36 has been widely used in several central nervous system (CNS) disorders, including neurodegenerative diseases. However, its effects on hydrocephalus have not been studied. Our aim was to evaluate the effects of acupuncture at ST36 on behaviour, motor development and reactive astrogliosis in infantile rats with hydrocephalus.

METHODS

Hydrocephalus was induced in sixteen 7-day-old pup rats by injection of 20% kaolin into the cisterna magna. One day after hydrocephalus induction, acupuncture was applied once daily (for 30 min) for a total of 21 days in eight randomly selected animals (HAc group) while the remaining eight remained untreated (H group). An additional eight healthy animals were included as controls (C group). All animals were weighed daily and, from the fifth day after hydrocephalus induction, underwent MRI to determine the ventricular ratio (VR). Rats were also exposed to modified open-field tests every 3 days until the end of the experiment. After 21 days all the animals were euthanased and their brains removed for histology and immunohistochemistry.

RESULTS

Hydrocephalic rats showed an increase in VR when compared with control rats (P<0.01). In addition, these animals exhibited delayed weight gain, which was attenuated with acupuncture treatment. Hydrocephalic animals treated with acupuncture performed better in open field tests (P<0.05), and had a reduction in reactive astrocyte cell density in the corpus callosum and external capsule, as assessed by GFAP (glial fibrillary acidic protein) immunohistochemistry (P<0.05).

CONCLUSIONS

These findings indicate that acupuncture at ST36 has a neuroprotective potential mediated, in part, by inhibition of astrogliosis.

The effect of tumor removal via craniotomies on preoperative hydrocephalus in adult patients with intracranial tumors

The efficacy of tumor removal via craniotomies on preoperative hydrocephalus (HC) in adult patients with intracranial tumors is largely unknown. Therefore, we sought to evaluate the effect of tumor resection in patients with preoperative HC and identify the incidence and risk factors for postoperative VP shunt dependency. All craniotomies for intracranial tumors at Oslo University Hospital in patients ≥ 18 years old during a 10-year period (2004-2013) were reviewed. Patients with radiologically confirmed HC requiring surgery and subsequent development of shunt dependency were identified by cross-linking our prospectively collected tumor database to surgical procedure codes for hydrocephalus treatment (AAF). Patients with preexisting ventriculoperitoneal (VP) shunts (N = 41) were excluded. From 4774 craniotomies performed on 4204 patients, a total of 373 patients (7.8%) with HC preoperatively were identified. Median age was 54.4 years (range 18.1-83.9 years). None were lost to follow-up. Of these, 10.5% (39/373) required permanent CSF shunting due to persisting postoperative HC. The risk of becoming VP shunt dependent in patients with preexisting HC was 7.0% (26/373) within 30 days and 8.9% (33/373) within 90 days. Only secondary (repeat) surgery was a significant risk factor for VP shunt dependency. In this large, contemporary, single-institution consecutive series, 10.5% of intracranial tumor patients with preoperative HC became shunt-dependent post-craniotomy, yielding a surgical cure rate for HC of 89.5%. To the best of our knowledge, this is the first and largest study regarding postoperative shunt dependency after craniotomies for intracranial tumors, and can serve as benchmark for future studies.

Diffusion tensor imaging study of pediatric patients with congenital hydrocephalus: 1-year postsurgical outcomes

OBJECTIVE The purpose of this study was to investigate white matter (WM) structural abnormalities using diffusion tensor imaging (DTI) in children with hydrocephalus before CSF diversionary surgery (including ventriculoperitoneal shunt insertion and endoscopic third ventriculostomy) and during the course of recovery after surgery in association with neuropsychological and behavioral outcome. METHODS This prospective study included 54 pediatric patients with congenital hydrocephalus (21 female, 33 male; age range 0.03-194.5 months) who underwent surgery and 64 normal controls (30 female, 34 male; age range 0.30-197.75 months). DTI and neurodevelopmental outcome data were collected once in the control group and 3 times (preoperatively and at 3 and 12 months postoperatively) in the patients with hydrocephalus. DTI measures, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values were extracted from the genu of the corpus callosum (gCC) and the posterior limb of internal capsule (PLIC). Group analysis was performed first cross-sectionally to quantify DTI abnormalities at 3 time points by comparing the data obtained in the hydrocephalus group for each of the 3 time points to data obtained in the controls. Longitudinal comparisons were conducted pairwise between different time points in patients whose data were acquired at multiple time points. Neurodevelopmental data were collected and analyzed using the Adaptive Behavior Assessment System, Second Edition, and the Bayley Scales of Infant Development, Third Edition. Correlation analyses were performed between DTI and behavioral measures. RESULTS Significant DTI abnormalities were found in the hydrocephalus patients in both the gCC (lower FA and higher MD, AD, and RD) and the PLIC (higher FA, lower AD and RD) before surgery. The DTI measures in the gCC remained mostly abnormal at 3 and 12 months after surgery. The DTI abnormalities in the PLIC were significant in FA and AD at 3 months after surgery but did not persist when tested at 12 months after surgery. Significant longitudinal DTI changes in the patients with hydrocephalus were found in the gCC when findings at 3 and 12 months after surgery were compared. In the PLIC, trend-level longitudinal changes were observed between preoperative findings and 3-month postoperative findings, as well as between 3- and 12-month postoperative findings. Significant correlation between DTI and developmental outcome was found at all 3 time points. Notably, a significant correlation was found between DTI in the PLIC at 3 months after surgery and developmental outcome at 12 months after surgery. CONCLUSIONS The data showed significant WM abnormality based on DTI in both the gCC and the PLIC in patients with congenital hydrocephalus before surgery, and the abnormalities persisted in both the gCC and the PLIC at 3 months after surgery. The DTI values remained significantly abnormal in the gCC at 12 months after surgery. Longitudinal analysis showed signs of recovery in both WM structures between different time points. Combined with the significant correlation found between DTI and neuropsychological measures, the findings of this study suggest that DTI can serve as a sensitive imaging biomarker for underlying neuroanatomical changes and postsurgical developmental outcome and even as a predictor for future outcomes.

Hydrocephalus compacted cortex and hippocampus and altered their output neurons in association with spatial learning and memory deficits in rats

Hydrocephalus is a common neurological disorder in children characterized by abnormal dilation of cerebral ventricles as a result of the impairment of cerebrospinal fluid flow or absorption. Clinical presentation of hydrocephalus varies with chronicity and often shows cognitive dysfunction. Here we used a kaolin-induction method in rats and studied the effects of hydrocephalus on cerebral cortex and hippocampus, the two regions highly related to cognition. Hydrocephalus impaired rats' performance in Morris water maze task. Serial three-dimensional reconstruction from sections of the whole brain freshly froze in situ with skull shows that the volumes of both structures were reduced. Morphologically, pyramidal neurons of the somatosensory cortex and hippocampus appear to be distorted. Intracellular dye injection and subsequent three-dimensional reconstruction and analyses revealed that the dendritic arbors of layer III and V cortical pyramid neurons were reduced. The total dendritic length of CA1, but not CA3, pyramidal neurons was also reduced. Dendritic spine densities on both cortical and hippocampal pyramidal neurons were decreased, consistent with our concomitant findings that the expressions of both synaptophysin and postsynaptic density protein 95 were reduced. These cortical and hippocampal changes suggest reductions of excitatory connectivity, which could underlie the learning and memory deficits in hydrocephalus.

Changes in Rat Brain Tissue Microstructure and Stiffness during the Development of Experimental Obstructive Hydrocephalus

Understanding neural injury in hydrocephalus and how the brain changes during the course of the disease in-vivo remain unclear. This study describes brain deformation, microstructural and mechanical properties changes during obstructive hydrocephalus development in a rat model using multimodal magnetic resonance (MR) imaging. Hydrocephalus was induced in eight Sprague-Dawley rats (4 weeks old) by injecting a kaolin suspension into the cisterna magna. Six sham-injected rats were used as controls. MR imaging (9.4T, Bruker) was performed 1 day before, and at 3, 7 and 16 days post injection. T2-weighted MR images were collected to quantify brain deformation. MR elastography was used to measure brain stiffness, and diffusion tensor imaging (DTI) was conducted to observe brain tissue microstructure. Results showed that the enlargement of the ventricular system was associated with a decrease in the cortical gray matter thickness and caudate-putamen cross-sectional area (P < 0.001, for both), an alteration of the corpus callosum and periventricular white matter microstructure (CC+PVWM) and rearrangement of the cortical gray matter microstructure (P < 0.001, for both), while compression without gross microstructural alteration was evident in the caudate-putamen and ventral internal capsule (P < 0.001, for both). During hydrocephalus development, increased space between the white matter tracts was observed in the CC+PVWM (P < 0.001), while a decrease in space was observed for the ventral internal capsule (P < 0.001). For the cortical gray matter, an increase in extracellular tissue water was significantly associated with a decrease in tissue stiffness (P = 0.001). To conclude, this study characterizes the temporal changes in tissue microstructure, water content and stiffness in different brain regions and their association with ventricular enlargement. In summary, whilst diffusion changes were larger and statistically significant for majority of the brain regions studied, the changes in mechanical properties were modest. Moreover, the effect of ventricular enlargement is not limited to the CC+PVWM and ventral internal capsule, the extent of microstructural changes vary between brain regions, and there is regional and temporal variation in brain tissue stiffness during hydrocephalus development.

Development of an experimental model of neurocysticercosis-induced hydrocephalus. Pilot study

PURPOSE

To develop an experimental model of neurocysticercosis-induced hydrocephalus

METHODS

There were used 17 rats. Ten animals were inoculated with Taenia crassiceps cysts into the subarachnoid. Five animals were injected with 0. ml of 25% kaolin (a standard solution for the development of experimental hydrocephalus) and two animals were injected with saline. Magnetic resonance imaging (MRI) was used to evaluate enlargement of the ventricles after one or three months of inoculation. Volumetric study was used to quantify the ventricle enlargement.

RESULTS

Seven of the 10 animals in the cyst group developed hydrocephalus, two of them within one month and five within three months after inoculation. Three of the five animals in the kaolin group had hydrocephalus and none in the saline group. Ventricle volumes were significantly higher in the 3-months MRI cyst subgroup than in the 1-month cyst subgroup. Differences between cyst subgroups and kaolin group did not reach statistical significance.

CONCLUSION

The developed model may reproduce the human condition of neurocysticercosis-related hydrocephalus, which exhibits a slowly progressive chronic course.

MR assessment of pediatric hydrocephalus: a road map

PURPOSE

This study was conducted to design a rational approach to the MR diagnosis of hydrocephalus based on a pathophysiologic reevaluation of its possible mechanisms and to apply it to the different etiological contexts.

METHOD

A review of the literature reports describing new physiologic models of production and absorption and of the hydrodynamics of the CSF was made.

RESULTS

Besides the secretion of CSF by the choroid plexuses, and its passive, pressure-dependent transdural absorption (arachnoid villi, dural clefts, cranial, and spinal nerve sheaths), water transporters, aquaporins, allow water (if not ions and organic molecules) to exchange freely between the brain parenchyma and the CSF spaces across the ependymal and the pial interfaces (including the Virchow-Robin spaces). Consequently, the CSF bulk flow is not necessarily global, and situations of balanced absorption-secretion may occur separately in different CSF compartments such as the ventricular, intracranial, or intraspinal CSF spaces. This means that rather than from a hypothetical pressure gradient from the plexuses to the dural sinuses, the dynamics of the CSF depend on the force provided in those different compartments by the arterial systolic pulsation of the pericerebral (mostly), intracerebral, and intraventricular (choroid plexuses) vascular beds.

CONCLUSION

Using MR imaging, diverse varieties of hydrocephalus may tentatively be explained by applying those concepts to the correspondingly diverse causal diseases. Hopefully, this may have an impact on the choice of the treatment strategies also.

Mechanical stress models of Alzheimer's disease pathology

INTRODUCTION

Extracellular accumulation of amyloid-β protein and intracellular accumulation of tau in brain tissues have been described in animal models of Alzheimer's disease (AD) and mechanical stress-based diseases of different mechanisms, such as traumatic brain injury (TBI), arterial hypertension (HTN), and normal pressure hydrocephalus (NPH).

METHODS

We provide a brief overview of experimental models of TBI, HTN, and NPH showing features of tau-amyloid pathology, neuroinflammation, and neuronal loss.

RESULTS

"Alzheimer-like" hallmarks found in these mechanical stress-based models were compared with AD features found in transgenic models.

DISCUSSION

The goal of this review is, therefore, to build on current concepts of onset and progression of AD lesions. We point to the importance of accumulated mechanical stress in brain as an environmental and endogenous factor that pushes protein deposition and neuronal injury over the disease threshold. We further encourage the development of preventing strategies and drug screening based on mechanical stress models.

Mechanical Stress as the Common Denominator between Chronic Inflammation, Cancer, and Alzheimer's Disease

The pathogenesis of common diseases, such as Alzheimer's disease (AD) and cancer, are currently poorly understood. Inflammation is a common risk factor for cancer and AD. Recent data, provided by our group and from others, demonstrate that increased pressure and inflammation are synonymous. There is a continuous increase in pressure from inflammation to fibrosis and then cancer. This is in line with the numerous papers reporting high interstitial pressure in cancer. But most authors focus on the role of pressure in the lack of delivery of chemotherapy in the center of the tumor. Pressure may also be a key factor in carcinogenesis. Increased pressure is responsible for oncogene activation and cytokine secretion. Accumulation of mechanical stress plays a key role in the development of diseases of old age, such as cardiomyopathy, atherosclerosis, and osteoarthritis. Growing evidence suggest also a possible link between mechanical stress in the pathogenesis of AD. The aim of this review is to describe environmental and endogenous mechanical factors possibly playing a pivotal role in the mechanism of chronic inflammation, AD, and cancer.

Oral antioxidant therapy for juvenile rats with kaolin-induced hydrocephalus

Background

Oxidative and nitrosylative changes have been shown to occur in conjunction with the hypoxic changes and cellular/axonal damage in hydrocephalic rodent brains. We hypothesized that antioxidant therapy would improve behavioral, neurophysiological, and/or neurobiochemical outcomes in juvenile rats following induction of hydrocephalus.

Methods

Three-week old rats received an injection of kaolin (aluminum silicate) into the cisterna magna. Magnetic resonance (MR) imaging was performed two weeks later to assess ventricle size and stratify rats to four treatment conditions. Rats were treated for two weeks daily with sham therapy of either oral canola oil or dextrose or experimental therapy of a low or high dose of an antioxidant mixture containing α-tocopherol, L-ascorbic acid, coenzyme Q10 (CoQ10), reduced glutathione, and reduced lipoic acid. Behavior was examined thrice weekly.

Results

All hydrocephalic groups lagged in weight gain in comparison to non-hydrocephalic controls, all developed significant ventriculomegaly, and all exhibited white matter destruction. Canola oil with or without the antioxidant mixture normalized antioxidant capacity in brain tissue, and the dextrose-treated rats had the greatest ventricular enlargement during the treatment period. However, there were no significant differences between the four treatment groups of hydrocephalic rats for the various behavioral tasks. Glial fibrillary acidic protein and myelin basic protein quantitation showed no differences between the treatment groups or with control rats. There was increased lipid peroxidation in the hydrocephalic rats compared to controls but no differences between treatment groups.

Conclusion

The antioxidant cocktail showed no therapeutic benefits for juvenile rats with kaolin-induced hydrocephalus although canola oil might have mild benefit.

Anatomical and diffusion MRI of deep gray matter in pediatric spina bifida

Individuals with spina bifida myelomeningocele (SBM) exhibit brain abnormalities in cortical thickness, white matter integrity, and cerebellar structure. Little is known about deep gray matter macro- and microstructure in this population. The current study utilized volumetric and diffusion-weighted MRI techniques to examine gray matter volume and microstructure in several subcortical structures: basal ganglia nuclei, thalamus, hippocampus, and amygdala. Sixty-six children and adolescents (ages 8–18; M = 12.0, SD = 2.73) with SBM and typically developing (TD) controls underwent T₁- and diffusion-weighted neuroimaging. Microstructural results indicated that hippocampal volume was disproportionately reduced, whereas the putamen volume was enlarged in the group with SBM. Microstructural analyses indicated increased mean diffusivity (MD) and fractional anisotropy (FA) in the gray matter of most examined structures (i.e., thalamus, caudate, hippocampus), with the putamen exhibiting a unique pattern of decreased MD and increased FA. These results provide further support that SBM differentially disrupts brain regions whereby some structures are volumetrically normal whereas others are reduced or enlarged. In the hippocampus, volumetric reduction coupled with increased MD may imply reduced cellular density and aberrant organization. Alternatively, the enlarged volume and significantly reduced MD in the putamen suggest increased density.

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Spina bifida resulted in reduced hippocampal and enlarged putamen volumes.

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Spina bifida resulted in reduced MD and increased FA in the putamen.

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Periventricular regions were differentiated by increased MD and FA in spina bifida.

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Spina bifida resulted in greater FA for all regions, except the hippocampus.

Kaolin-induced ventriculomegaly at weaning produces long-term learning, memory, and motor deficits in rats

Ventriculomegaly occurs when there is imbalance between creation and absorption of cerebrospinal fluid (CSF); even when treated, long-term behavioral changes occur. Kaolin injection in the cisterna magna of rats produces an obstruction of CSF outflow and models one type of hydrocephalus. Previous research with this model shows that neonatal onset has mixed effects on Morris water maze (MWM) and motoric performance; we hypothesized that this might be because the severity of ventricular enlargement was not taken into consideration. In the present experiment, rats were injected with kaolin or saline on postnatal day (P)21 and analyzed in subgroups based on Evan's ratios (ERs) of the severity of ventricular enlargement at the end of testing to create 4 subgroups from least to most severe: ER0.4-0.5, ER0.51-0.6, ER0.61-0.7, and ER0.71-0.82, respectively. Locomotor activity (dry land and swimming), acoustic startle with prepulse inhibition (PPI), and MWM performance were tested starting on P28 (122cm maze) and again on P42 (244cm maze). Kaolin-treated animals weighed significantly less than controls at all times. Differences in locomotor activity were seen at P42 but not P28. On P28 there was an increase in PPI for all but the least severe kaolin-treated group, but no difference at P42 compared with controls. In the MWM at P28, all kaolin-treated groups had longer path lengths than controls, but comparable swim speeds. With the exception of the least severe group, probe trial performance was worse in the kaolin-treated animals. On P42, only the most severely affected kaolin-treated group showed deficits compared with control animals. This group showed no MWM learning and no memory for the platform position during probe trial testing. Swim speed was unaffected, indicating motor deficits were not responsible for impaired learning and memory. These findings indicate that kaolin-induced ventriculomegaly in rats interferes with cognition regardless of the final enlargement of the cerebral ventricles, but final size critically determines whether lasting locomotor, learning, and memory impairments occur.

Fingerprint changes in CSF composition associated with different aetiologies in human neonatal hydrocephalus: glial proteins associated with cell damage and loss

Background

In hydrocephalus an imbalance between production and absorption of cerebrospinal fluid (CSF) results in fluid accumulation, compression and stretching of the brain parenchyma. In addition, changes in CSF composition have a profound influence on the development and function of the brain and together, these can result in severe life-long neurological deficits. Brain damage or degenerative conditions can result in release of proteins expressed predominantly in neurons, astroglia, or oligodendroglia into the brain interstitial fluid, CSF and blood. Determination of such products in the CSF might be of value in diagnosing cause, aetiology and/or assessing the severity of the neurological damage in patients with hydrocephalus. We therefore analysed CSF from human neonates with hydrocephalus for these proteins to provide an insight into the pathophysiology associated with different aetiologies.

Methods

CSF was collected during routine lumbar puncture or ventricular tap. Samples were categorized according to age of onset of hydrocephalus and presumed cause (fetal-onset, late-onset, post-haemorrhagic or spina bifida with hydrocephalus). Glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), vimentin and 2^′ , 3^′-cyclic nucleotide 3^′-phosphodiesterase (CNPase) were analysed through Western blotting of hydrocephalic CSF samples (n = 17) and compared with data from CSF of normal infants without neurological deficits (n = 8).

Results

GFAP was significantly raised only in CSF from post-haemorrhagic hydrocephalus while MBP was significantly raised in post-haemorrhagic and in spina bifida with hydrocephalus infants. Vimentin protein was only detected in some CSF samples from infants with late-onset hydrocephalus but not from other conditions. Surprisingly, CNPase was found in all neonatal CSF samples, including normal and hydrocephalic groups, although it was reduced in infants with late onset hydrocephalus compared with normal and other hydrocephalic groups.

Conclusions

Apart from CNPase, which is an enzyme, the markers investigated are intracellular intermediate filaments and would be present in CSF only if the cells are compromised and the proteins released. Raised GFAP observed in post-haemorrhagic hydrocephalus must reflect damage to astrocytes and ependyma. Raised MBP in post-haemorrhagic and spina bifida with hydrocephalus indicates damage to oligodendrocytes and myelin. Vimentin protein detected in some of the late-onset hydrocephalic samples indicates damage to glial and other progenitors and suggests this condition affects periventricular regions. The presence of CNPase in all CSF samples was unexpected and indicates a possible novel role for this enzyme in brain development/myelination. Less CNPase in some cases of late-onset hydrocephalus could therefore indicate changes in myelination in these infants. This study demonstrates differential glial damage and loss in the developing human neonatal hydrocephalic brain associated with different aetiologies.

Genetic deletion of afadin causes hydrocephalus by destruction of adherens junctions in radial glial and ependymal cells in the midbrain

Adherens junctions (AJs) play a role in mechanically connecting adjacent cells to maintain tissue structure, particularly in epithelial cells. The major cell–cell adhesion molecules at AJs are cadherins and nectins. Afadin binds to both nectins and α-catenin and recruits the cadherin-β-catenin complex to the nectin-based cell–cell adhesion site to form AJs. To explore the role of afadin in radial glial and ependymal cells in the brain, we generated mice carrying a nestin-Cre-mediated conditional knockout (cKO) of the afadin gene. Newborn afadin-cKO mice developed hydrocephalus and died neonatally. The afadin-cKO brain displayed enlarged lateral ventricles and cerebral aqueduct, resulting from stenosis of the caudal end of the cerebral aqueduct and obliteration of the ventral part of the third ventricle. Afadin deficiency further caused the loss of ependymal cells from the ventricular and aqueductal surfaces. During development, radial glial cells, which terminally differentiate into ependymal cells, scattered from the ventricular zone and were replaced by neurons that eventually covered the ventricular and aqueductal surfaces of the afadin-cKO midbrain. Moreover, the denuded ependymal cells were only occasionally observed in the third ventricle and the cerebral aqueduct of the afadin-cKO midbrain. Afadin was co-localized with nectin-1 and N-cadherin at AJs of radial glial and ependymal cells in the control midbrain, but these proteins were not concentrated at AJs in the afadin-cKO midbrain. Thus, the defects in the afadin-cKO midbrain most likely resulted from the destruction of AJs, because AJs in the midbrain were already established before afadin was genetically deleted. These results indicate that afadin is essential for the maintenance of AJs in radial glial and ependymal cells in the midbrain and is required for normal morphogenesis of the cerebral aqueduct and ventral third ventricle in the midbrain.

Reduced subventricular zone proliferation and white matter damage in juvenile ferrets with kaolin-induced hydrocephalus

Hydrocephalus is a neurological condition characterized by altered cerebrospinal fluid (CSF) flow with enlargement of ventricular cavities in the brain. A reliable model of hydrocephalus in gyrencephalic mammals is necessary to test preclinical hypotheses. Our objective was to characterize the behavioral, structural, and histological changes in juvenile ferrets following induction of hydrocephalus. Fourteen-day old ferrets were given an injection of kaolin (aluminum silicate) into the cisterna magna. Two days later and repeated weekly until 56 days of age, magnetic resonance (MR) imaging was used to assess ventricle size. Behavior was examined thrice weekly. Compared to age-matched saline-injected controls, severely hydrocephalic ferrets weighed significantly less, their postures were impaired, and they were hyperactive prior to extreme debilitation. They developed significant ventriculomegaly and displayed white matter destruction. Reactive astroglia and microglia detected by glial fibrillary acidic protein (GFAP) and Iba-1 immunostaining were apparent in white matter, cortex, and hippocampus. There was a hydrocephalus-related increase in activated caspase 3 labeling of apoptotic cells (7.0 vs. 15.5%) and a reduction in Ki67 labeling of proliferating cells (23.3 vs. 5.9%) in the subventricular zone (SVZ). Reduced Olig2 immunolabeling suggests a depletion of glial precursors. GFAP content was elevated. Myelin basic protein (MBP) quantitation and myelin biochemical enzyme activity showed early maturational increases. Where white matter was not destroyed, the remaining axons developed myelin similar to the controls. In conclusion, the hydrocephalus-induced periventricular disturbances may involve developmental impairments in cell proliferation and glial precursor cell populations. The ferret should prove useful for testing hypotheses about white matter damage and protection in the immature hydrocephalic brain.

Diffusion tensor imaging properties and neurobehavioral outcomes in children with hydrocephalus

BACKGROUND AND PURPOSE

White matter structural alterations and the correlation with neuropsychological deficits in children with hydrocephalus have not been well investigated. In this prospective study, the objectives were the following: 1) to apply DTI to detect in vivo white matter alterations based on diffusion properties in children with acute hydrocephalus, 2) to quantify early neuropsychological deficits, and 3) to explore the correlation between potential neuropsychological deficits and abnormalities in functionally related white matter.

MATERIALS AND METHODS

A total of 44 children, 24 with hydrocephalus and 20 controls, were enrolled in the study. DTI indices, FA, MD, AD, and RD, were evaluated in the gCC, sCC, PLIC, and ALIC. The ABAS-II was used as a broad screener of development, including conceptual, social, practical, and motor skills. The correlation between the Motor Scale and DTI indices in the PLIC was analyzed.

RESULTS

DTI analyses showed that the gCC and sCC in children with hydrocephalus had lower FA and higher MD, driven by the increased RD with statistical significance (P < .05) or trend-level significance (P = .06). The PLIC and ALIC had significantly higher AD in children with hydrocephalus (P < .05). On the ABAS-II, parent ratings of general adaptive skills, conceptual skills, and motor skills were significantly lower in children with hydrocephalus (all at P < .05). The MD and RD values in the PLIC were found to have trend-level or significant correlation with the Motor Scale (P = .057, .041, respectively).

CONCLUSIONS

DTI reveals alterations in the white matter structure in children with hydrocephalus with preliminary findings suggesting correlation with clinical motor deficits.

Astrocytes acquire morphological and functional characteristics of ependymal cells following disruption of ependyma in hydrocephalus

Hydrocephalic hyh mutant mice undergo a programmed loss of the neuroepithelium/ependyma followed by a reaction of periventricular astrocytes, which form a new cell layer covering the denuded ventricular surface. We present a comparative morphological and functional study of the newly formed layer of astrocytes and the multiciliated ependyma of hyh mice. Transmission electron microscopy, immunocytochemistry for junction proteins (N-cadherin, connexin 43) and proteins involved in permeability (aquaporin 4) and endocytosis (caveolin-1, EEA1) were used. Horseradish peroxidase (HRP) and lanthanum nitrate were used to trace the intracellular and paracellular transport routes. The astrocyte layer shares several cytological features with the normal multiciliated ependyma, such as numerous microvilli projected into the ventricle, extensive cell–cell interdigitations and connexin 43-based gap junctions, suggesting that these astrocytes are coupled to play an unknown function as a cell layer. The ependyma and the astrocyte layers also share transport properties: (1) high expression of aquaporin 4, caveolin-1 and the endosome marker EEA1; (2) internalization into endocytic vesicles and early endosomes of HRP injected into the ventricle; (3) and a similar paracellular route of molecules moving between CSF, the subependymal neuropile and the pericapillary space, as shown by lanthanum nitrate and HRP. A parallel analysis performed in human hydrocephalic foetuses indicated that a similar phenomenon would occur in humans. We suggest that in foetal-onset hydrocephalus, the astrocyte assembly at the denuded ventricular walls functions as a CSF–brain barrier involved in water and solute transport, thus contributing to re-establish lost functions at the brain parenchyma–CSF interphase.

Cerebrospinal fluid volume measurements in hydrocephalic rats

Object Experimental data about the evolution of intracranial volume and pressure in cases of hydrocephalus are limited due to the lack of available monitoring techniques. In this study, the authors validate intracranial CSF volume measurements within the lateral ventricle, while simultaneously using impedance sensors and pressure transducers in hydrocephalic animals. Methods A volume sensor was fabricated and connected to a catheter that was used as a shunt to withdraw CSF. In vitro bench-top calibration experiments were created to provide data for the animal experiments and to validate the sensors. To validate the measurement technique in a physiological system, hydrocephalus was induced in weanling rats by kaolin injection into the cisterna magna. At 28 days after induction, the sensor was implanted into the lateral ventricles. After sealing the skull using dental cement, an acute CSF drainage/infusion protocol consisting of 4 sequential phases was performed with a pump. Implant location was confirmed via radiography using intraventricular iohexol contrast administration. Results Controlled CSF shunting in vivo with hydrocephalic rats resulted in precise and accurate sensor measurements (r = 0.98). Shunting resulted in a 17.3% maximum measurement error between measured volume and actual volume as assessed by a Bland-Altman plot. A secondary outcome confirmed that both ventricular volume and intracranial pressure decreased during CSF shunting and increased during infusion. Ventricular enlargement consistent with successful hydrocephalus induction was confirmed using imaging, as well as postmortem. These results indicate that volume monitoring is feasible for clinical cases of hydrocephalus. Conclusions This work marks a departure from traditional shunting systems currently used to treat hydrocephalus. The overall clinical application is to provide alternative monitoring and treatment options for patients. Future work includes development and testing of a chronic (long-term) volume monitoring system.

Pathophysiology of congenital and neonatal hydrocephalus

The pathophysiology of congenital and neonatal hydrocephalus is not well understood although the prognosis for patients with this disorder is far from optimal. A major obstacle to advancing our knowledge of the causes of this disorder and the cellular responses that accompany it is the multifactorial nature of hydrocephalus. Not only is the epidemiology varied and complex, but the injury mechanisms are numerous and overlapping. Nevertheless, several conclusions can be made with certainty: the age of onset strongly influences the degree of impairment; injury severity is dependent on the magnitude and duration of ventriculomegaly; the primary targets are periventricular axons, myelin, and microvessels; cerebrovascular injury mechanisms are prominent; gliosis and neuroinflammation play major roles; some but not all changes are preventable by draining cerebrospinal fluid with shunts and third ventriculostomies; cellular plasticity and physiological compensation probably occur but this is a major under-studied area; and pharmacologic interventions are promising. Rat and mouse models have provided important insights into the pathogenesis of congenital and neonatal hydrocephalus. Ependymal denudation of the ventricular lining appears to affect the development of neural progenitors exposed to cerebrospinal fluid, and alterations of the subcommissural organ influence the patency of the cerebral aqueduct. Recently these impairments have been observed in patients with fetal-onset hydrocephalus, so experimental findings are beginning to be corroborated in humans. These correlations, coupled with advanced genetic manipulations in animals and successful pharmacologic interventions, support the view that improved treatments for congenital and neonatal hydrocephalus are on the horizon.

The relationship between ventricular dilatation, neuropathological and neurobehavioural changes in hydrocephalic rats

Background

The motor and cognitive deficits observed in hydrocephalus are thought to be due to axonal damage within the periventricular white matter. This study was carried out to investigate the relationship between ventricular size, cellular changes in brain, and neurobehavioural deficits in rats with experimental hydrocephalus.

Methods

Hydrocephalus was induced in three-week old rats by intracisternal injection of kaolin. Behavioural and motor function were tested four weeks after hydrocephalus induction and correlated to ventricular enlargement which was classified into mild, moderate or severe. Gross brain morphology, routine histology and immunohistochemistry for oligodendrocytes (CNPase), microglia (Iba-1) and astrocytes (GFAP) were performed to assess the cellular changes.

Results

Decreases in open field activity and forelimb grip strength in hydrocephalus correlated with the degree of ventriculomegaly. Learning in Morris water maze was significantly impaired in hydrocephalic rats. Gradual stretching of the ependymal layer, thinning of the corpus callosum, extracellular oedema and reduced cortical thickness were observed as the degree of ventriculomegaly increased. A gradual loss of oligodendrocytes in the corpus callosum and cerebral cortex was most marked in the severely-hydrocephalic brains, whereas the widespread astrogliosis especially in the subependymal layer was most marked in the brains with mild hydrocephalus. Retraction of microglial processes and increase in Iba-1 immunoreactivity in the white matter was associated ventriculomegaly.

Conclusions

In hydrocephalic rats, oligodendrocyte loss, microglia activation, astrogliosis in cortical areas and thinning of the corpus callosum were associated with ventriculomegaly. The degree of ventriculomegaly correlated with motor and cognitive deficits.

Cerebral white matter oxidation and nitrosylation in young rodents with kaolin-induced hydrocephalus

Hydrocephalus is associated with reduced blood flow in periventricular white matter. To investigate hypoxic and oxidative damage in the brains of rats with hydrocephalus, kaolin was injected into the cisterna magna of newborn 7- and 21-day-old Sprague-Dawley rats, and ventricle size was assessed by magnetic resonance imaging at 7, 21, and 42 days of age. In-situ evidence of hypoxia in periventricular capillaries and glial cells was shown by pimonidazole hydrochloride binding. Biochemical assay of thiobarbituric acid reaction and immunohistochemical detection of malondialdehyde and 4-hydroxy-2-nonenal indicated the presence of lipid peroxidation in white matter. Biochemical assay of nitrite indicated increased nitric oxide production. Nitrotyrosine immunohistochemistry showed nitrosylated proteins in white matter reactive microglia and astrocytes. Activities of the antioxidant enzymes catalase and glutathione peroxidase were not increased, and altered hypoxia-inducible factor 1α was not detected by quantitative reverse transcription-polymerase chain reaction. Cerebral vascular endothelial growth factor expression determined by quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay was not changed, but vascular endothelial growth factor immunoreactivity was increased in reactive astrocytes of hydrocephalic white matter. To determine if nitric oxide synthase is involved in the pathogenesis, we induced hydrocephalus in 7-day-old wild-type and neuronal nitric oxide synthase-deficient mice. At 7 days, the wild-type and mutant mice exhibited equally severe ventriculomegaly and no behavioral differences, although increased glial fibrillary acidic protein was less in the mutant mice. We conclude that hypoxia, via peroxidation and nitrosylation, contributes to brain changes in young rodents with hydrocephalus and that compensatory mechanisms are negligible.

Morphological and morphometric analysis of the hippocampus in Wistar rats with experimental hydrocephalus

BACKGROUND

The present study aims at better establishing the alterations caused by the usual enlargement of brain ventricles in this structure.

METHODS

Hydrocephalus was induced in 7-day-old Wistar rats by the injection of kaolin into the cisterna magna. Morphological studies were performed on the hippocampus 7, 14 and 21 days after injection. The total number of neurons in each hippocampus subarea as well as that of pyknotic neurons were counted. Then we calculated the pyknotic index (PI) by hippocampal subarea, taking into account the level of ventricular dilatation and time of induction of hydrocephalus.

RESULTS

PI was statistically larger in the CA1 subarea of the experimental group after 1 week of hydrocephalus induction as compared to the corresponding control as well as in animals that had developed mild hydrocephalus in groups G1, G2 and G3.

CONCLUSION

Hydrocephalus caused morphological alterations in the hippocampus, leading to important changes in its shape.

Diffusion tensor imaging of white matter injury in a rat model of infantile hydrocephalus

OBJECTIVE

Diffusion tensor imaging (DTI) is a non-invasive MRI technique that has been used to quantify white matter (WM) abnormality in both clinical and experimental hydrocephalus (HCP). However, no DTI study has been conducted to characterize anisotropic diffusion properties in an animal model of infantile HCP. This DTI study was designed to investigate a rat model of HCP induced at postnatal day 21, a time developmentally equivalent to the human infancy.

METHODS

DTI data were acquired at approximately 4 weeks after the induction of HCP with kaolin injection. Using a 7 Tesla small animal MRI scanner we performed high-resolution DTI on 12 rats with HCP and 6 saline controls. Regions of interest (ROI) examined with quantitative comparisons include the genu, body, and splenium of the corpus callosum (gCC, bCC, and sCC, respectively), anterior, middle, and posterior external capsule (aEC, mEC, and pEC, respectively), internal capsule (IC), and fornix (FX). For each ROI, DTI metrics including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Dax), and radial diffusivity (Drad) were calculated.

RESULTS

We found that the anisotropic diffusion properties were abnormal across multiple WM regions in the brains of the HCP rats. Statistically significant differences included: (1) decreased FA and increased MD and Drad values in the gCC and bCC; (2) increased Dax in the sCC; (3) increased FA and Dax in the aEC; (4) increased FA in the mEC; (5) increased MD and Drad in the pEC; (6) increased FA and Dax in IC; (7) increased FA in FX.

CONCLUSIONS

These preliminary results provide the first evidence of WM injury quantified by DTI in a rat model of infantile HCP. Our data showed that DTI is a sensitive tool to characterize patterns of WM abnormalities and support the notion that WM impairment is region specific in response to HCP.

Reactive astrocytosis in feline neonatal hydrocephalus: acute, chronic, and shunt-induced changes

PURPOSE

Reactive astrocytosis has been implicated in injury and recovery patterns associated with hydrocephalus. To investigate temporal changes in astrogliosis during the early progression of hydrocephalus, after shunting, and after long-term ventriculomegaly, glial fibrillary protein (GFAP) levels were analyzed in a feline model.

METHODS

Obstructive hydrocephalus was induced in 10-day-old kittens by intracisternal injections of 25% kaolin. Acute non-shunted animals were killed 15 days post-kaolin injection to represent the pre-shunt condition. Shunt-treated animals received ventriculoperitoneal shunts 15 days post-injection and were killed 10 or 60 days later to represent short- and long-term recovery periods. Chronic untreated animals had Ommaya reservoirs implanted 15 days post-kaolin, which were tapped intermittently until they were killed 60 days later. Ventriculomegaly was monitored by neuroimaging before and after shunting and at death. RNA and total protein from primary visual cortex were analyzed by Northern and Western blotting.

RESULTS

GFAP RNA and protein levels for acute and chronic non-shunted hydrocephalic animals were 77% and 247% (p < 0.01) and 659% (p < 0.05) and 871% (p < 0.05) higher than controls, respectively. Shunted animals with short-term recovery demonstrated a mismatch in GFAP levels, with RNA expression decreasing 26% and protein increasing 335% (p < 0.01). Shunted animals with a long-term recovery exhibited GFAP RNA and protein levels 201% and 357% above normal, respectively.

CONCLUSIONS

These results indicate that a reactive astrocytic response continues to rise dramatically in chronic hydrocephalus, suggesting ongoing gliosis and potential damage. Shunting partially ameliorates the continuation of astrogliosis, but does not completely reverse this inflammatory reaction even after a long recovery.

Magnetic resonance imaging indicators of blood-brain barrier and brain water changes in young rats with kaolin-induced hydrocephalus

BACKGROUND

Hydrocephalus is associated with enlargement of cerebral ventricles. We hypothesized that magnetic resonance (MR) imaging parameters known to be influenced by tissue water content would change in parallel with ventricle size in young rats and that changes in blood-brain barrier (BBB) permeability would be detected.

METHODS

Hydrocephalus was induced by injection of kaolin into the cisterna magna of 4-week-old rats, which were studied 1 or 3 weeks later. MR was used to measure longitudinal and transverse relaxation times (T1 and T2) and apparent diffusion coefficients in several regions. Brain tissue water content was measured by the wet-dry weight method, and tissue density was measured in Percoll gradient columns. BBB permeability was measured by quantitative imaging of changes on T1-weighted images following injection of gadolinium diethylenetriamine penta-acetate (Gd-DTPA) tracer and microscopically by detection of fluorescent dextran conjugates.

RESULTS

In nonhydrocephalic rats, water content decreased progressively from age 3 to 7 weeks. T1 and T2 and apparent diffusion coefficients did not exhibit parallel changes and there was no evidence of BBB permeability to tracers. The cerebral ventricles enlarged progressively in the weeks following kaolin injection. In hydrocephalic rats, the dorsal cortex was more dense and the white matter less so, indicating that the increased water content was largely confined to white matter. Hydrocephalus was associated with transient elevation of T1 in gray and white matter and persistent elevation of T2 in white matter. Changes in the apparent diffusion coefficients were significant only in white matter. Ventricle size correlated significantly with dorsal water content, T1, T2, and apparent diffusion coefficients. MR imaging showed evidence of Gd-DTPA leakage in periventricular tissue foci but not diffusely. These correlated with microscopic leak of larger dextran tracers.

CONCLUSIONS

MR characteristics cannot be used as direct surrogates for water content in the immature rat model of hydrocephalus, probably because they are also influenced by other changes in tissue composition that occur during brain maturation. There is no evidence for widespread persistent opening of BBB as a consequence of hydrocephalus in young rats. However, increase in focal BBB permeability suggests that periventricular blood vessels may be disrupted.

Reactive astrocytosis, microgliosis and inflammation in rats with neonatal hydrocephalus

The deleterious effects of hydrocephalus, a disorder that primarily affects children, include reactive astrocytosis, microgliosis and inflammatory responses; however, the roles that these mechanisms play in the pathophysiology of hydrocephalus are still not clear in terms of cytopathology and gene expression. Therefore we have examined neuroinflammation at both the cellular and the molecular levels in an experimental model of neonatal obstructive hydrocephalus. On post-natal day 1, rats received an intracisternal injection of kaolin to induce hydrocephalus; control animals received saline injections. Prior to sacrifice on post-natal day 22, animals underwent magnetic resonance imaging to quantify ventricular enlargement, and the parietal cortex was harvested for analysis. Immunohistochemistry and light microscopy were performed on 5 hydrocephalic and 5 control animals; another set of 5 hydrocephalic and 5 control animals underwent molecular testing with Western blots and a gene microarray. Scoring of immunoreactivity on a 4-point ranking scale for GFAP and Iba-1 demonstrated an increase in reactive astrocytes and reactive microglia respectively in the hydrocephalic animals compared to controls (2.90±0.11 vs. 0.28±0.26; 2.91±0.11 vs. 0.58±0.23, respectively). Western blots confirmed these results. Microarray analysis identified significant (1.5-fold) changes in 1729 of 33,951 genes, including 26 genes out of 185 genes (26/185) in the cytokine-cytokine receptor interaction pathway, antigen processing and presentation pathways (15/66), and the apoptosis pathway (10/69). Collectively, these results demonstrate alterations in normal physiology and an up-regulation of the inflammatory response. These findings lead to a better understanding of neonatal hydrocephalus and begin to form a baseline for future treatments that may reverse these effects.

Neuropathology and structural changes in hydrocephalus

In the context of spina bifida, hydrocephalus is usually caused by crowding of the posterior fossa with obstruction to cerebrospinal fluid flow from the forth ventricle, and less often by malformation of the cerebral aqueduct. Enlargement of the cerebral ventricles causes gradual destruction of periventricular white matter axons. Motor, sensory, visual, and memory systems may be disturbed through involvement of the long projection axons, periventricular structures including the corpus callosum, and the fimbria-fornix pathway. Secondary changes occur in neuronal cell bodies and synapses, but there is minimal death of neurons. The clinical syndrome of hydrocephalic brain dysfunction is thus due to subcortical disconnection. Some of the brain dysfunction is reversible by shunting, probably through restoration of cerebral blood flow and normalization of the extracellular environment. However, destroyed axons cannot be restored.

Minocycline inhibits glial proliferation in the H-Tx rat model of congenital hydrocephalus

BACKGROUND

Reactive astrocytosis and microgliosis are important features of the pathophysiology of hydrocephalus, and persistent glial "scars" that form could exacerbate neuroinflammation, impair cerebral perfusion, impede neuronal regeneration, and alter biomechanical properties. The purpose of this study was to determine the efficacy of minocycline, an antibiotic known for its anti-inflammatory properties, to reduce gliosis in the H-Tx rat model of congenital hydrocephalus.

METHODS

Minocycline (45 mg/kg/day i.p. in 5% sucrose at a concentration of 5-10 mg/ml) was administered to hydrocephalic H-Tx rats from postnatal day 15 to day 21, when ventriculomegaly had reached moderate to severe stages. Treated animals were compared to age-matched non-hydrocephalic and untreated hydrocephalic littermates. The cerebral cortex (both gray matter laminae and white matter) was processed for immunohistochemistry (glial fibrillary acidic protein, GFAP, for astrocytes and ionized calcium binding adaptor molecule, Iba-1, for microglia) and analyzed by qualitative and quantitative light microscopy.

RESULTS

The mean number of GFAP-immunoreactive astrocytes was significantly higher in untreated hydrocephalic animals compared to both types of controls (p < 0.001). Minocycline treatment of hydrocephalic animals reduced the number of GFAP immunoreactive cells significantly (p < 0.001). Likewise, the mean number of Iba-1 immunoreactive microglia was significantly higher in untreated hydrocephalic animals compared to both types of controls (p < 0.001). Furthermore, no differences in the numbers of GFAP-positive astrocytes or Iba-1-positive microglia were noted between control animals receiving no minocycline and control animals receiving minocycline, suggesting that minocycline does not produce an effect under non-injury conditions. Additionally, in six out of nine regions sampled, hydrocephalic animals that received minocycline injections had significantly thicker cortices when compared to their untreated hydrocephalic littermates.

CONCLUSIONS

Overall, these data suggest that minocycline treatment is effective in reducing the gliosis that accompanies hydrocephalus, and thus may provide an added benefit when used as a supplement to ventricular shunting.

Longitudinal evaluation of an N-ethyl-N-nitrosourea-created murine model with normal pressure hydrocephalus

BACKGROUND

Normal-pressure hydrocephalus (NPH) is a neurodegenerative disorder that usually occurs late in adult life. Clinically, the cardinal features include gait disturbances, urinary incontinence, and cognitive decline.

METHODOLOGY/PRINCIPAL FINDINGS

Herein we report the characterization of a novel mouse model of NPH (designated p23-ST1), created by N-ethyl-N-nitrosourea (ENU)-induced mutagenesis. The ventricular size in the brain was measured by 3-dimensional micro-magnetic resonance imaging (3D-MRI) and was found to be enlarged. Intracranial pressure was measured and was found to fall within a normal range. A histological assessment and tracer flow study revealed that the cerebral spinal fluid (CSF) pathway of p23-ST1 mice was normal without obstruction. Motor functions were assessed using a rotarod apparatus and a CatWalk gait automatic analyzer. Mutant mice showed poor rotarod performance and gait disturbances. Cognitive function was evaluated using auditory fear-conditioned responses with the mutant displaying both short- and long-term memory deficits. With an increase in urination frequency and volume, the mutant showed features of incontinence. Nissl substance staining and cell-type-specific markers were used to examine the brain pathology. These studies revealed concurrent glial activation and neuronal loss in the periventricular regions of mutant animals. In particular, chronically activated microglia were found in septal areas at a relatively young age, implying that microglial activation might contribute to the pathogenesis of NPH. These defects were transmitted in an autosomal dominant mode with reduced penetrance. Using a whole-genome scan employing 287 single-nucleotide polymorphic (SNP) markers and further refinement using six additional SNP markers and four microsatellite markers, the causative mutation was mapped to a 5.3-cM region on chromosome 4.

CONCLUSIONS/SIGNIFICANCE

Our results collectively demonstrate that the p23-ST1 mouse is a novel mouse model of human NPH. Clinical observations suggest that dysfunctions and alterations in the brains of patients with NPH might occur much earlier than the appearance of clinical signs. p23-ST1 mice provide a unique opportunity to characterize molecular changes and the pathogenic mechanism of NPH.

Disruption of the neurogenic niche in the subventricular zone of postnatal hydrocephalic hyh mice

Neural stem cells persist after embryonic development in the subventricular zone (SVZ) niche and produce new neural cells during postnatal life; ependymal cells are a key component associated with this neurogenic niche. In the animal model of human hydrocephalus, the hyh mouse, the ependyma of the lateral ventricles is progressively lost during late embryonic and early postnatal life and disappears from most of the ventricular surface throughout its life span. To determine the potential consequences of this loss on the SVZ, we characterized the abnormalities in this neurogenic niche in hyh mice. There was overall disorganization and a marked reduction of proliferative cells in the SVZ of both newborn and adult hyh hydrocephalic mice in vivo; neuroblasts were displaced to the ventricular surface, and their migration through the rostral migratory stream was reduced. The numbers of resident neural progenitor cells in hyh mice were also markedly reduced, but they were capable of proliferating, forming neurospheres, and differentiating into neurons and glia in vitro in a manner indistinguishable from that of wild-type progenitor cells. These findings suggest that the reduction of proliferative activity observed in vivo is not caused by a cell autonomous defect of SVZ progenitors but is a consequence of a reduced number of these cells. Furthermore, the overall tissue disorganization of the SVZ and displacement of neuroblasts imply alterations in the neurogenic niche of postnatal hyh mice.

Beta8 integrin regulates neurogenesis and neurovascular homeostasis in the adult brain

Central nervous system (CNS) neurovascular units are multicellular complexes consisting of neural cells, blood vessels and a milieu of extracellular matrix (ECM) proteins. ECM-mediated adhesion and signaling events within neurovascular units probably contribute to proper CNS development and physiology; however, the molecular mechanisms that control these events remain largely undetermined. Previous studies from our group and others showed that ablation of the ECM receptor, alphavbeta8 integrin, in neural progenitor cells (NPCs) of the embryonic mouse brain results in severe developmental neurovascular pathologies and premature death. Here, we have investigated the functions for this integrin in the adult brain by studying mice harboring a homozygous-null beta8 gene mutation generated on an outbred background that permits survival for several months. We show that adult beta8-/- mice display widespread defects in neurovascular unit homeostasis, including increased numbers of intracerebral blood vessels with pronounced perivascular astrogliosis. Furthermore, in neurogenic regions of the adult brain, where NPCs cluster around blood vessels in neurovascular niches, beta8 integrin is essential for normal control of NPC proliferation and survival. Analysis of NPCs cultured ex vivo reveals that the growth and survival defects correlate, in part, with diminished integrin-mediated activation of latent transforming growth factor beta1 (TGFbeta1), which is an ECM protein ligand for alphavbeta8 integrin. Collectively, these data identify essential functions for beta8 integrin in regulating neurovascular unit physiology in the post-natal mouse brain.