Reduction of astrogliosis and microgliosis by cerebrospinal fluid shunting in experimental hydrocephalus

Unveiling the role of astrogliosis in Alzheimer's disease Pathology: Insights into mechanisms and therapeutic approaches

Alzheimer's disease (AD) is one of the most debilitating age-related disorders that affect people globally. It impacts social and cognitive behavior of the individual and is characterized by phosphorylated tau and Aβ accumulation. Astrocytesmaintain a quiescent, anti-inflammatory state on anatomical level, expressing few cytokines and exhibit phagocytic activity to remove misfolded proteins. But in AD, in response to specific stimuli, astrocytes overstimulate their phagocytic character with overexpressing cytokine gene modules. Upon interaction with generated Aβ and neurofibrillary tangle, astrocytes that are continuously activated release a large number of inflammatory cytokines. This cytokine storm leads to neuroinflammation which is also one of the recognizable features of AD. Astrogliosis eventually promotes cholinergic dysfunction, calcium imbalance, oxidative stress and excitotoxicity. Furthermore, C5aR1, Lcn2/, BDNF/TrkB and PPARα/TFEB signaling dysregulation has a major impact on the disease progression. This review clarifies numerous ways that lead to astrogliosis, which is stimulated by a variety of processes that exacerbate AD pathology and make it a suitable target for AD treatment. Drugs under clinical and preclinical investigations that target several pathways managing astrogliosis and are efficacious in ameliorating the pathology of the disease are also included in this study. D-ALA2GIP, TRAM-34, Genistein, L-serine, MW150 and XPro1595 are examples of few drugs targeting astrogliosis. Therefore, this study may aid in the development of a potent therapeutic agent for ameliorating astrogliosis mediated AD progression.

Microcirculatory Impairment and Cerebral Injury in Hydrocephalus and the Effects of Cerebrospinal Fluid Diversion

BACKGROUND AND OBJECTIVES

Hydrocephalus is characterized by progressive enlargement of cerebral ventricles, resulting in impaired microvasculature and cerebral hypoperfusion. This study aimed to demonstrate the microvascular changes in hydrocephalic rats and the effects of cerebrospinal fluid (CSF) release on cerebral blood flow (CBF).

METHODS

On postnatal day 21 (P21), male Wistar rats were intracisternally injected with either a kaolin suspension or saline. On P47, Evan's ratio (ER) was measured using MRI. On P49, the arteriolar diameter and vascular density of the pia were quantified using a capillary video microscope. The CBF was measured using laser Doppler flowmetry. The expressions of NeuN and glial fibrillary acidic protein determined by immunochemical staining were correlated with the ER. The CBF and rotarod test performance were recorded before and after CSF release. The expressions of 4-hydroxynonenal (4-HNE) and c-caspase-3 were studied on P56.

RESULTS

Ventriculomegaly was induced to varying degrees, resulting in the stretching and abnormal narrowing of pial arterioles, which regressed with increasing ER. Quantitative analysis revealed significant decreases in the arteriolar diameter and vascular density in the hydrocephalic group compared with those in the control group. In addition, the CBF in the hydrocephalic group decreased to 30%-50% of that in the control group. In hydrocephalus, the neurons appear distorted, and the expression of 4-HNE and reactive astrogliosis increase in the cortex. After CSF was released, improvements in the CBF and rotarod test performance were inversely associated with the ER. In addition, the levels of 4-HNE and c-caspase-3 were further elevated.

CONCLUSION

Rapid ventricular dilatation is associated with severe microvascular distortion, vascular regression, cortical hypoperfusion, and cellular changes that impair the recovery of CBF and motor function after CSF release. Moreover, CSF release may induce reperfusion injury. This pathophysiology should be taken into account when treating hydrocephalus.

Use of neurofilament light chain to identify structural brain diseases in dogs

BACKGROUND

Neurofilament light chain (NfL) is released into the peripheral circulation by damaged axons.

OBJECTIVES

To evaluate the diagnostic value of serum NfL concentration in dogs with intracranial diseases.

ANIMALS

Study included 37 healthy dogs, 31 dogs with idiopathic epilepsy (IE), 45 dogs with meningoencephalitis of unknown etiology (MUE), 20 dogs with hydrocephalus, and 19 dogs with brain tumors.

METHODS

Cohort study. Serum NfL concentrations were measured in all dogs using single-molecule array technology.

RESULTS

Serum NfL concentration in dogs with each structural disease was significantly higher than in healthy dogs and dogs with IE (P = .01). The area under the receiver operating characteristic curve of NfL for differentiating between dogs with structural diseases and IE was 0.868. An optimal cutoff value of the NfL 27.10 pg/mL had a sensitivity of 86.67% and a specificity of 74.19% to differentiate the dogs with IE from those with structural brain diseases. There were significant correlations between NfL concentrations and lesion size: (1) MUE, P = .01, r = 0.429; (2) hydrocephalus, P = .01, r = 0.563.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum NfL could be a useful biomarker for distinguishing IE from structural diseases in dogs and predicting the lesion sizes of MUE and hydrocephalus.

Improve the diagnosis of idiopathic normal pressure hydrocephalus by combining abnormal cortical thickness and ventricular morphometry

Background

The primary imaging markers for idiopathic Normal Pressure Hydrocephalus (iNPH) emphasize morphological measurements within the ventricular system, with no attention given to alterations in brain parenchyma. This study aimed to investigate the potential effectiveness of combining ventricular morphometry and cortical structural measurements as diagnostic biomarkers for iNPH.

Methods

A total of 57 iNPH patients and 55 age-matched healthy controls (HC) were recruited in this study. Firstly, manual measurements of ventricular morphology, including Evans Index (EI), z-Evans Index (z-EI), Cella Media Width (CMW), Callosal Angle (CA), and Callosal Height (CH), were conducted based on MRI scans. Cortical thickness measurements were obtained, and statistical analyses were performed using surface-based morphometric analysis. Secondly, three distinct models were developed using machine learning algorithms, each based on a different input feature: a ventricular morphology model (LVM), a cortical thickness model (CT), and a fusion model (All) incorporating both features. Model performances were assessed using 10-fold cross validation and tested on an independent dataset. Model interpretation utilized Shapley Additive Interpretation (SHAP), providing a visualization of the contribution of each variable in the predictive model. Finally, Spearman correlation coefficients were calculated to evaluate the relationship between imaging biomarkers and clinical symptoms.

Results

iNPH patients exhibited notable differences in cortical thickness compared to HC. This included reduced thickness in the frontal, temporal, and cingulate cortices, along with increased thickness in the supracentral gyrus. The diagnostic performance of the fusion model (All) for iNPH surpassed that of the single-feature models, achieving an average accuracy of 90.43%, sensitivity of 90.00%, specificity of 90.91%, and Matthews correlation coefficient (MCC) of 81.03%. This improvement in accuracy (6.09%), sensitivity (11.67%), and MCC (11.25%) compared to the LVM strategy was significant. Shap analysis revealed the crucial role of cortical thickness in the right isthmus cingulate cortex, emerging as the most influential factor in distinguishing iNPH from HC. Additionally, significant correlations were observed between the typical triad symptoms of iNPH patients and cortical structural alterations.

Conclusion

This study emphasizes the significant role of cortical structure changes in the diagnosis of iNPH, providing a novel insights for assisting clinicians in improving the identification and detection of iNPH.

Early postnatal microglial ablation in the Ccdc39 mouse model reveals adverse effects on brain development and in neonatal hydrocephalus

BACKGROUND

Neonatal hydrocephalus is a congenital abnormality resulting in an inflammatory response and microglial cell activation both clinically and in animal models. Previously, we reported a mutation in a motile cilia gene, Ccdc39 that develops neonatal progressive hydrocephalus (prh) with inflammatory microglia. We discovered significantly increased amoeboid-shaped activated microglia in periventricular white matter edema, reduced mature homeostatic microglia in grey matter, and reduced myelination in the prh model. Recently, the role of microglia in animal models of adult brain disorders was examined using cell type-specific ablation by colony-stimulating factor-1 receptor (CSF1R) inhibitor, however, little information exists regarding the role of microglia in neonatal brain disorders such as hydrocephalus. Therefore, we aim to see if ablating pro-inflammatory microglia, and thus suppressing the inflammatory response, in a neonatal hydrocephalic mouse line could have beneficial effects.

METHODS

In this study, Plexxikon 5622 (PLX5622), a CSF1R inhibitor, was subcutaneously administered to wild-type (WT) and prh mutant mice daily from postnatal day (P) 3 to P7. MRI-estimated brain volume was compared with untreated WT and prh mutants P7-9 and immunohistochemistry of the brain sections was performed at P8 and P18-21.

RESULTS

PLX5622 injections successfully ablated IBA1-positive microglia in both the WT and prh mutants at P8. Of the microglia that are resistant to PLX5622 treatment, there was a higher percentage of amoeboid-shaped microglia, identified by morphology with retracted processes. In PLX-treated prh mutants, there was increased ventriculomegaly and no change in the total brain volume was observed. Also, the PLX5622 treatment significantly reduced myelination in WT mice at P8, although this was recovered after full microglia repopulation by P20. Microglia repopulation in the mutants worsened hypomyelination at P20.

CONCLUSIONS

Microglia ablation in the neonatal hydrocephalic brain does not improve white matter edema, and actually worsens ventricular enlargement and hypomyelination, suggesting critical functions of homeostatic ramified microglia to better improve brain development with neonatal hydrocephalus. Future studies with detailed examination of microglial development and status may provide a clarification of the need for microglia in neonatal brain development.

Vanadium improves memory and spatial learning and protects the pyramidal cells of the hippocampus in juvenile hydrocephalic mice

Background

Hydrocephalus is a neurological condition known to cause learning and memory disabilities due to its damaging effect on the hippocampal neurons, especially pyramidal neurons. Vanadium at low doses has been observed to improve learning and memory abilities in neurological disorders but it is uncertain whether such protection will be provided in hydrocephalus. We investigated the morphology of hippocampal pyramidal neurons and neurobehavior in vanadium-treated and control juvenile hydrocephalic mice.

Methods

Hydrocephalus was induced by intra-cisternal injection of sterile-kaolin into juvenile mice which were then allocated into 4 groups of 10 pups each, with one group serving as an untreated hydrocephalic control while others were treated with 0.15, 0.3 and 3 mg/kg i.p of vanadium compound respectively, starting 7 days post-induction for 28 days. Non-hydrocephalic sham controls (n = 10) were sham operated without any treatment. Mice were weighed before dosing and sacrifice. Y-maze, Morris Water Maze and Novel Object Recognition tests were carried out before the sacrifice, the brains harvested, and processed for Cresyl Violet and immunohistochemistry for neurons (NeuN) and astrocytes (GFAP). The pyramidal neurons of the CA1 and CA3 regions of the hippocampus were assessed qualitatively and quantitatively. Data were analyzed using GraphPad prism 8.

Results

Escape latencies of vanadium-treated groups were significantly shorter (45.30 ± 26.30 s, 46.50 ± 26.35 s, 42.99 ± 18.44 s) than untreated group (62.06 ± 24.02 s) suggesting improvements in learning abilities. Time spent in the correct quadrant was significantly shorter in the untreated group (21.19 ± 4.15 s) compared to control (34.15 ± 9.44 s) and 3 mg/kg vanadium-treated group (34.35 ± 9.74 s). Recognition index and mean % alternation were lowest in untreated group (p = 0.0431, p=0.0158) suggesting memory impairments, with insignificant improvements in vanadium-treated groups. NeuN immuno-stained CA1 revealed loss of apical dendrites of the pyramidal cells in untreated hydrocephalus group relative to control and a gradual reversal attempt in the vanadium-treated groups. Astrocytic activation (GFAP stain) in the untreated hydrocephalus group were attenuated in the vanadium-treated groups under the GFAP stain. Pyknotic index in CA1 pyramidal layer of untreated (18.82 ± 2.59) and 0.15mg/kg vanadium-treated groups (18.14 ± 5.92) were significantly higher than control (11.11 ± 0.93; p = 0.0205, p = 0.0373) while there was no significant difference in CA3 pyknotic index across all groups.

Conclusion

Our results suggest that vanadium has a dose-dependent protective effect on the pyramidal cells of the hippocampus and on memory and spatial learning functions in juvenile hydrocephalic mice.

Distinct cerebral cortical perfusion patterns in idiopathic normal-pressure hydrocephalus

The aims of the study are to evaluate idiopathic normal-pressure hydrocephalus (INPH)-related cerebral blood flow (CBF) abnormalities and to investigate their relation to cortical thickness in INPH patients. We investigated cortical CBF utilizing surface-based early-phase ¹⁸ F-florbetaben (E-FBB) PET analysis in two groups: INPH patients and healthy controls. All 39 INPH patients and 20 healthy controls were imaged with MRI, including three-dimensional volumetric images, for automated surface-based cortical thickness analysis across the entire brain. A subgroup with 37 participants (22 INPH patients and 15 healthy controls) that also underwent ¹⁸ F-fluorodeoxyglucose (FDG) PET imaging was further analyzed. Compared with age- and gender-matched healthy controls, INPH patients showed statistically significant hyperperfusion in the high convexity of the frontal and parietal cortical regions. Importantly, within the INPH group, increased perfusion correlated with cortical thickening in these regions. Additionally, significant hypoperfusion mainly in the ventrolateral frontal cortex, supramarginal gyrus, and temporal cortical regions was observed in the INPH group relative to the control group. However, this hypoperfusion was not associated with cortical thinning. A subgroup analysis of participants that also underwent FDG PET imaging showed that increased (or decreased) cerebral perfusion was associated with increased (or decreased) glucose metabolism in INPH. A distinctive regional relationship between cerebral cortical perfusion and cortical thickness was shown in INPH patients. Our findings suggest distinct pathophysiologic mechanisms of hyperperfusion and hypoperfusion in INPH patients.

AQP4, Astrogenesis, and Hydrocephalus: A New Neurological Perspective

Aquaporin 4 (AQP4) is a cerebral glial marker that labels ependymal cells and astrocytes' endfeet and is the main water channel responsible for the parenchymal fluid balance. However, in brain development, AQP4 is a marker of glial stem cells and plays a crucial role in the pathophysiology of pediatric hydrocephalus. Gliogenesis characterization has been hampered by a lack of biomarkers for precursor and intermediate stages and a deeper understanding of hydrocephalus etiology is needed. This manuscript is a focused review of the current research landscape on AQP4 as a possible biomarker for gliogenesis and its influence in pediatric hydrocephalus, emphasizing reactive astrogliosis. The goal is to understand brain development under hydrocephalic and normal physiologic conditions.

Distinct volumetric features of cerebrospinal fluid distribution in idiopathic normal-pressure hydrocephalus and Alzheimer's disease

Objective

The aims of the study were to measure the cerebrospinal fluid (CSF) volumes in the lateral ventricle, high-convexity subarachnoid space, and Sylvian fissure region in patients with idiopathic normal-pressure hydrocephalus (INPH) and Alzheimer’s disease (AD), and to evaluate differences in these volumes between INPH and AD groups and healthy controls.

Methods

Forty-nine INPH patients, 59 AD patients, and 26 healthy controls were imaged with automated three-dimensional volumetric MRI.

Results

INPH patients had larger lateral ventricles and CSF spaces of the Sylvian fissure region and smaller high-convexity subarachnoid spaces than other groups, and AD patients had larger lateral ventricles and CSF spaces of the Sylvian fissure region than the control group. The INPH group showed a negative correlation between lateral ventricle and high-convexity subarachnoid space volumes, while the AD group showed a positive correlation between lateral ventricle volume and volume for CSF spaces of the Sylvian fissure region. The ratio of lateral ventricle to high-convexity subarachnoid space volumes yielded an area under the curve of 0.990, differentiating INPH from AD.

Conclusions

Associations between CSF volumes suggest that there might be different mechanisms between INPH and AD to explain their respective lateral ventricular dilations. The ratio of lateral ventricle to high-convexity subarachnoid space volumes distinguishes INPH from AD with good diagnostic sensitivity and specificity. We propose to refer to this ratio as the VOSS (ventricle over subarachnoid space) index.

Evaluation of the blood neutrophil-to-lymphocyte ratio as a biomarker for meningoencephalitis of unknown etiology in dogs

Background

The neutrophil‐to‐lymphocyte ratio (NLR) has been identified as a biomarker in several inflammatory and autoimmune diseases. Multiple sclerosis (MS) has been found to be associated with changes in the NLR in humans.

Objectives

To examine the diagnostic value of the NLR in meningoencephalitis of unknown etiology (MUE) in dogs.

Animals

Thirty‐eight MUE dogs, 20 hydrocephalic dogs, 10 brain tumor (BT) dogs, 32 idiopathic epilepsy (IE) dogs, and 41 healthy dogs.

Methods

Retrospective study. Medical records were reviewed to identify dogs with a diagnosis of neurologic disease. The NLR was determined in all dogs.

Results

The median NLR was significantly higher in MUE dogs (6.08) than in healthy (1.78, P < .001), IE (2.50, P < .05), and hydrocephalic dogs (1.79, P < .05). The area under the receiver operating characteristic curve of the NLR for differentiation between MUE and healthy dogs was 0.96, and between the MUE dogs and dogs with other forebrain diseases was 0.86. An optimal cutoff of 4.16 for the NLR had a sensitivity of 71.1% and specificity of 83.9% to differentiate the MUE dogs from the dogs with other forebrain diseases.

Conclusions and Clinical Importance

The NLR could be a biomarker for diagnosing MUE and distinguishing it from other intracranial diseases in dogs.

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.

Spontaneous angiogram-negative subarachnoid hemorrhage: a retrospective single center cohort study

Background

Spontaneous angiogram-negative subarachnoid hemorrhage (SAH) is considered a benign illness with little of the aneurysmal SAH-related complications. We describe the clinical course, SAH-related complications, and outcome of patients with angiogram-negative SAH.

Methods

We retrospectively reviewed all adult patients admitted to a neurosurgical intensive care unit during 2004–2018 due to spontaneous angiogram-negative SAH. Our primary outcome was a dichotomized Glasgow Outcome Scale (GOS) at 3 months. We assessed factors that associated with outcome using multivariable logistic regression analysis.

Results

Of the 108 patients included, 84% had a favorable outcome (GOS 4–5), and mortality was 5% within 1 year. The median age was 58 years, 51% were female, and 93% had a low-grade SAH (World Federation of Neurosurgical Societies grading I–III). The median number of angiograms performed per patient was two. Thirty percent of patients showed radiological signs of acute hydrocephalus, 28% were acutely treated with an external ventricular drain, 13% received active vasospasm treatment and 17% received a permanent shunt. In the multivariable logistic regression model, only acute hydrocephalus associated with unfavorable outcome (odds ratio = 4.05, 95% confidence interval = 1.05–15.73). Two patients had a new bleeding episode.

Conclusion

SAH-related complications such as hydrocephalus and vasospasm are common after angiogram-negative SAH. Still, most patients had a favorable outcome. Only acute hydrocephalus was associated with unfavorable outcome. The high rate of SAH-related complications highlights the need for neurosurgical care in these patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00701-021-05069-7.

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.

Elevated CSF inflammatory markers in patients with idiopathic normal pressure hydrocephalus do not promote NKCC1 hyperactivity in rat choroid plexus

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible neurological condition of unresolved etiology characterized by a clinical triad of symptoms; gait disturbances, urinary incontinence, and cognitive deterioration. In the present study, we aimed to elucidate the molecular coupling between inflammatory markers and development of iNPH and determine whether inflammation-induced hyperactivity of the choroidal Na⁺/K⁺/2Cl^- cotransporter (NKCC1) that is involved in cerebrospinal fluid (CSF) secretion could contribute to the iNPH pathogenesis.

METHODS

Lumbar CSF samples from 20 iNPH patients (10 with clinical improvement upon CSF shunting, 10 without clinical improvement) and 20 elderly control subjects were analyzed with the novel proximity extension assay technique for presence of 92 different inflammatory markers. RNA-sequencing was employed to delineate choroidal abundance of the receptors for the inflammatory markers found elevated in the CSF from iNPH patients. The ability of the elevated inflammatory markers to modulate choroidal NKCC1 activity was determined by addition of combinations of rat version of these in ex vivo experiments on rat choroid plexus.

RESULTS

11 inflammatory markers were significantly elevated in the CSF from iNPH patients compared to elderly control subjects: CCL28, CCL23, CCL3, OPG, CXCL1, IL-18, IL-8, OSM, 4E-BP1, CXCL6, and Flt3L. One inflammatory marker, CDCP1, was significantly decreased in iNPH patients compared to control subjects. None of the inflammatory markers differed significantly when comparing iNPH patients with and without clinical improvement upon CSF shunting. All receptors for the elevated inflammatory markers were expressed in the rat and human choroid plexus, except CCR4 and CXCR1, which were absent from the rat choroid plexus. None of the elevated inflammatory markers found in the CSF from iNPH patients modulated the choroidal NKCC1 activity in ex vivo experiments on rat choroid plexus.

CONCLUSION

The CSF from iNPH patients contains elevated levels of a subset of inflammatory markers. Although the corresponding inflammatory receptors are, in general, expressed in the choroid plexus of rats and humans, their activation did not modulate the NKCC1-mediated fraction of choroidal CSF secretion ex vivo. The molecular mechanisms underlying ventriculomegaly in iNPH, and the possible connection to inflammation, therefore remains to be elucidated.

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.

Increased plasma levels of chitinase 3-like 1 (CHI3L1) protein in patients with idiopathic normal-pressure hydrocephalus

Idiopathic normal-pressure hydrocephalus (iNPH) is an uncommon neurological disorder with no known pathological hallmarks. INPH may share common degenerative pathways with other neurological diseases, such as Alzheimer's disease (AD). However, the reversible properties of iNPH may share differing pathophysiological mechanisms with other diseases. This study aimed at assessing the diagnostic value of plasma chitinase 3-like 1 (CHI3L1) protein levels as a disease-specific biomarker for iNPH. We selected both iNPH and AD patients as well as normal and disease control subjects from an enrolled dementia registry. A total of 121 AD, 80 iNPH, 13 idiopathic Parkinson's disease, and 23 mild cognitive impairment patients with 83 healthy controls were included in the final analysis. The Aβ42, total tau, and phosphorylated tau levels within the cerebrospinal fluid, as well as plasma levels of CHI3L1, were measured using commercially available enzyme-linked immunosorbent assay kits. CHI3L1 levels for iNPH patients were higher than those of the other groups. Analysis of covariance adjusting for age showed significantly increased plasma CHI3L1 levels in iNPH patients than in the controls (p < 0.001). CHI3L1 plasma levels may be useful in differentiating iNPH patients from healthy individuals.

MR Elastography demonstrates reduced white matter shear stiffness in early-onset hydrocephalus

INTRODUCTION

Hydrocephalus that develops early in life is often accompanied by developmental delays, headaches and other neurological deficits, which may be associated with changes in brain shear stiffness. However, noninvasive approaches to measuring stiffness are limited. Magnetic Resonance Elastography (MRE) of the brain is a relatively new noninvasive imaging method that provides quantitative measures of brain tissue stiffness. Herein, we aimed to use MRE to assess brain stiffness in hydrocephalus patients compared to healthy controls, and to assess its associations with ventricular size, as well as demographic, shunt-related and clinical outcome measures.

METHODS

MRE was collected at two imaging sites in 39 hydrocephalus patients and 33 healthy controls, along with demographic, shunt-related, and clinical outcome measures including headache and quality of life indices. Brain stiffness was quantified for whole brain, global white matter (WM), and lobar WM stiffness. Group differences in brain stiffness between patients and controls were compared using two-sample t-tests and multivariable linear regression to adjust for age, sex, and ventricular volume. Among patients, multivariable linear or logistic regression was used to assess which factors (age, sex, ventricular volume, age at first shunt, number of shunt revisions) were associated with brain stiffness and whether brain stiffness predicts clinical outcomes (quality of life, headache and depression).

RESULTS

Brain stiffness was significantly reduced in patients compared to controls, both unadjusted (p ≤ 0.002) and adjusted (p ≤ 0.03) for covariates. Among hydrocephalic patients, lower stiffness was associated with older age in temporal and parietal WM and whole brain (WB) (beta (SE): -7.6 (2.5), p = 0.004; -9.5 (2.2), p = 0.0002; -3.7 (1.8), p = 0.046), being female in global and frontal WM and WB (beta (SE): -75.6 (25.5), p = 0.01; -66.0 (32.4), p = 0.05; -73.2 (25.3), p = 0.01), larger ventricular volume in global, and occipital WM (beta (SE): -11.5 (3.4), p = 0.002; -18.9 (5.4), p = 0.0014). Lower brain stiffness also predicted worse quality of life and a higher likelihood of depression, controlling for all other factors.

CONCLUSIONS

Brain stiffness is reduced in hydrocephalus patients compared to healthy controls, and is associated with clinically-relevant functional outcome measures. MRE may emerge as a clinically-relevant biomarker to assess the neuropathological effects of hydrocephalus and shunting, and may be useful in evaluating the effects of therapeutic alternatives, or as a supplement, of shunting.

Abnormal cortical thickening and thinning in idiopathic normal-pressure hydrocephalus

We investigated differences in cortical thickness between idiopathic normal-pressure hydrocephalus (INPH) patients and healthy controls. We also explored whether a relationship exists between cortical thinning and gait disturbance in INPH patients. Forty-nine INPH patients and 26 healthy controls were imaged with MRI, including 3-dimensional volumetric images, for automated surface-based cortical thickness analysis across the entire brain. Compared with age- and gender-matched healthy controls, unexpectedly, INPH patients showed statistically significant cortical thickening mainly in areas located in the high convexity of the frontal, parietal, and occipital regions. Additionally, cortical thinning mainly in temporal and orbitofrontal regions was observed in the INPH group relative to the control group. The Gait Status Scale (GSS) scores were negatively correlated with cortical thickness in the medial orbital part of the superior frontal gyrus, gyrus rectus, superior temporal gyrus, temporal pole, and insula. A distinctive pattern of cortical thickness changes was found in INPH patients. We cautiously suggest that cortical thickening in INPH can result from reactive gliosis. Further, our results support the hypothesis that cortical thinning in INPH can result from neuronal degeneration. In addition, cortical thinning can play an important role in gait disturbances in INPH patients.

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.

Loss of Rsph9 causes neonatal hydrocephalus with abnormal development of motile cilia in mice

Hydrocephalus is a brain disorder triggered by cerebrospinal fluid accumulation in brain cavities. Even though cerebrospinal fluid flow is known to be driven by the orchestrated beating of the bundled motile cilia of ependymal cells, little is known about the mechanism of ciliary motility. RSPH9 is increasingly becoming recognized as a vital component of radial spokes in ciliary "9 + 2" ultrastructure organization. Here, we show that deletion of the Rsph9 gene leads to the development of hydrocephalus in the early postnatal period. However, the neurodevelopment and astrocyte development are normal in embryonic Rsph9^-/- mice. The tubular structure of the central aqueduct was comparable in Rsph9^-/- mice. Using high-speed video microscopy, we visualized lower beating amplitude and irregular rotation beating pattern of cilia bundles in Rsph9^-/- mice compared with that of wild-type mice. And the centriolar patch size was significantly increased in Rsph9^-/- cells. TEM results showed that deletion of Rsph9 causes little impact in ciliary axonemal organization but the Rsph9^-/- cilia frequently had abnormal ectopic ciliary membrane inclusions. In addition, hydrocephalus in Rsph9^-/- mice results in the development of astrogliosis, microgliosis and cerebrovascular abnormalities. Eventually, the ependymal cells sloughed off of the lateral wall. Our results collectively suggested that RSPH9 is essential for ciliary structure and motility of mouse ependymal cilia, and its deletion causes the pathogenesis of hydrocephalus.

Long-Term Intellectual and Fine Motor Outcomes in Spina Bifida Are Related to Myelomeningocele Repair and Shunt Intervention History

OBJECTIVE

Lifespan outcomes of simultaneous versus sequential myelomeningocele repair and shunt placement or effects of repeated shunt revisions on specific domains of IQ or fine motor dexterity are largely unknown. The current study addressed these gaps in a large cohort of children and adults with spina bifida myelomeningocele (SBM).

METHODS

Participants between 7 and 44 years of age with SBM and shunted hydrocephalus were recruited from international clinics at two time points. Each participant completed a standardized neuropsychological evaluation that included estimates of IQ and fine motor dexterity. Simultaneous versus sequential surgical repair and number of shunt revisions were examined in relation to long-term IQ and fine motor scores.

RESULTS

Simultaneous myelomeningocele repair and shunting were associated with more frequent shunt revisions, as well as to lower Full Scale and verbal IQ scores, controlling for number of shunt revisions. More shunt revisions across study time points were associated with higher nonverbal IQ (NVIQ) scores. No effects were observed on fine motor dexterity.

CONCLUSIONS

Findings indicate generally greater influence of surgery type over shunt revision history on outcomes in well-managed hydrocephalus. Findings supported apparent, domain-specific benefits of sequential compared to simultaneous surgery across the lifespan in SBM. Higher NVIQ scores with greater number of additional shunt revisions across surgery type supported positive outcomes with effective surgical management for hydrocephalus.

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.

MR diffusion changes in the perimeter of the lateral ventricles demonstrate periventricular injury in post-hemorrhagic hydrocephalus of prematurity

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Diffusion MRI demonstrates PHH is associated with LVP microstructural injury.

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The greatest PHH-associated disruption occurs at the frontal and occipital horns.

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Greater ventricular size is associated with greater disruption.

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dMRI may provide useful biomarkers for PHH monitoring and intervention.

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The region of LVP injury encompasses neuroprogenitor regions.

Objectives

Injury to the preterm lateral ventricular perimeter (LVP), which contains the neural stem cells responsible for brain development, may contribute to the neurological sequelae of intraventricular hemorrhage (IVH) and post-hemorrhagic hydrocephalus of prematurity (PHH). This study utilizes diffusion MRI (dMRI) to characterize the microstructural effects of IVH/PHH on the LVP and segmented frontal-occipital horn perimeters (FOHP).

Study design

Prospective study of 56 full-term infants, 72 very preterm infants without brain injury (VPT), 17 VPT infants with high-grade IVH without hydrocephalus (HG-IVH), and 13 VPT infants with PHH who underwent dMRI at term equivalent. LVP and FOHP dMRI measures and ventricular size-dMRI correlations were assessed.

Results

In the LVP, PHH had consistently lower FA and higher MD and RD than FT and VPT (p<.050). However, while PHH FA was lower, and PHH RD was higher than their respective HG-IVH measures (p<.050), the MD and AD values did not differ. In the FOHP, PHH infants had lower FA and higher RD than FT and VPT (p<.010), and a lower FA than the HG-IVH group (p<.001). While the magnitude of AD in both the LVP and FOHP were consistently less in the PHH group on pairwise comparisons to the other groups, the differences were not significant (p>.050). Ventricular size correlated negatively with FA, and positively with MD and RD (p<.001) in both the LVP and FOHP. In the PHH group, FA was lower in the FOHP than in the LVP, which was contrary to the observed findings in the healthy infants (p<.001). Nevertheless, there were no regional differences in AD, MD, and RD in the PHH group.

Conclusion

HG-IVH and PHH results in aberrant LVP/FOHP microstructure, with prominent abnormalities among the PHH group, most notably in the FOHP. Larger ventricular size was associated with greater magnitude of abnormality. LVP/FOHP dMRI measures may provide valuable biomarkers for future studies directed at improving the management and neurological outcomes of IVH/PHH.

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.

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.

Erythropoietin protects the subventricular zone and inhibits reactive astrogliosis in kaolin-induced hydrocephalic rats

PURPOSE

To elucidate the potential role of erythropoietin (EPO) as a neuroprotective agent against reactive astrogliosis and reducing the thinning rate of subventricular zone (SVZ) in kaolin-induced hydrocephalic rats.

METHOD

Thirty-six ten-week-old Sprague-Dawley rats were used in this study. Hydrocephalus was induced with 20% kaolin suspension injected into the cistern of thirty rats and leaving the six rats as normal group. The hydrocephalic rats were randomly divided into hydrocephalic and treatment group. The treatment group received daily dose of recombinant human erythropoietin (rhEPO) from day 7 to day 21 after induction. The animals were sacrificed at 7 (only for hydrocephalic group) and 14 or 21 (for both groups) days after induction. Brain was removed and was prepared for histological analysis by hematoxylin and eosin staining as well as immunohistochemistry for 4-HNE, GFAP, Iba-1, and Ki-67.

RESULTS

Histopathological analysis showed that animals treated with rhEPO had a reduced astrocyte reactivity displayed by lower GFAP expression. Hydrocephalic rats received rhEPO also displayed reduced microglial activation shown by lower Iba-1 protein expression. Exogenous rhEPO exerted its protective action in reducing astrogliosis by inhibiting lipid peroxidation that was documented in this study as lower expression of 4-HNE than non-treated group. The SVZ thickness was progressively declining in hydrocephalus group, while the progression rate could be reduced by rhEPO.

CONCLUSION

Erythropoietin has a potential use for inhibiting lipid peroxidation, and reactive astrogliosis in hydrocephalic animal model. The reduced thinning rate of SVZ demonstrated that EPO also had effect in reducing the hydrocephalus progressivity. Further research is warranted to explore its efficacy and safety to use in clinical setting.

Ventricular and Periventricular Anomalies in the Aging and Cognitively Impaired Brain

Ventriculomegaly (expansion of the brain’s fluid-filled ventricles), a condition commonly found in the aging brain, results in areas of gliosis where the ependymal cells are replaced with dense astrocytic patches. Loss of ependymal cells would compromise trans-ependymal bulk flow mechanisms required for clearance of proteins and metabolites from the brain parenchyma. However, little is known about the interplay between age-related ventricle expansion, the decline in ependymal integrity, altered periventricular fluid homeostasis, abnormal protein accumulation and cognitive impairment. In collaboration with the Baltimore Longitudinal Study of Aging (BLSA) and Alzheimer’s Disease Neuroimaging Initiative (ADNI), we analyzed longitudinal structural magnetic resonance imaging (MRI) and subject-matched fluid-attenuated inversion recovery (FLAIR) MRI and periventricular biospecimens to map spatiotemporally the progression of ventricle expansion and associated periventricular edema and loss of transependymal exchange functions in healthy aging individuals and those with varying degrees of cognitive impairment. We found that the trajectory of ventricle expansion and periventricular edema progression correlated with degree of cognitive impairment in both speed and severity, and confirmed that areas of expansion showed ventricle surface gliosis accompanied by edema and periventricular accumulation of protein aggregates, suggesting impaired clearance mechanisms in these regions. These findings reveal pathophysiological outcomes associated with normal brain aging and cognitive impairment, and indicate that a multifactorial analysis is best suited to predict and monitor cognitive decline.

Cortical Oligodendrocytes in Kaolin-Induced Hydrocephalus in Wistar Rat: Impact of Degree and Duration of Ventriculomegaly

BACKGROUND

Oligodendrocytes are critical to the function of the brain. They generate the myelin sheath which ensures saltatory conduction, which is a more energy saving and efficient means of axonal impulse transmission. Ventriculomegaly results in neuronal degeneration and astrogliosis.

PURPOSE

The effect of the degree of ventriculomegaly on oligodendrocyte in kaolin-induced hydrocephalus and the timeline have not been extensively documented, hence this study.

METHODS

A total of 81 rats that were 3 weeks old were divided into 4 groups each consisting of control and experimental subgroups. Kaolin suspension was intracisternally injected to induce hydrocephalus and the animal sacrificed post-induction at 1, 2, 3, and 4 weeks. Two 1-mm-thick coronal slices at optic chiasma level were fixed in 10% buffered formal-saline and Karnovsky's fixative for light and transmission electron microscopy (TEM), respectively. The former slices were processed and stained with hematoxylin and eosin for glial density, cortical thickness, and oligodendrocyte evaluations. Subcortical white matter region of the latter were processed by conventional techniques for TEM.

RESULTS

Compared with their corresponding control rats, thickness of the dorsolateral cortex was significantly reduced across the 2-4 week post-induction (WPI), glial density was significantly increased in the mild and moderate ventriculomegaly subgroups 1 WPI but only in mild ventriculomegaly subset 2 WPI. In the 4 WPI group, there was significant increase in glial density across the 3 ventriculomegaly subsets. Early hydropic changes of oligodendrocytes were noted in the inner pyramidal layer mostly in the 4 WPI experimental rats. Dilation of the endoplasmic reticulum precedes that of mitochondria, while mitochondrial crista disruption was noted in the 3 and 4 WPI rats. The nuclear membrane of the oligodendrocytes was progressively deformed from the 2nd to 4th WPI.

CONCLUSION

This study reported degenerative changes of oligodendrocytes and its organelles in kaolin-induced hydrocephalus. Degeneration was worse with duration and in the deep cortical layers.

Environmental enrichment reduces brain damage in hydrocephalic immature rats

PURPOSE

We investigate the effects of environmental enrichment (EE) on morphological alterations in different brain structures of pup rats submitted to hydrocephalus condition.

METHODS

Hydrocephalus was induced in 7-day-old pup rats by injection of 20% kaolin into the cisterna magna. Ventricular dilatation and magnetization transfer to analyze myelin were assessed by magnetic resonance. Hydrocephalic and control rats exposed to EE (n = 10 per group) were housed in cages with a tunnel, ramp, and colored plastic balls that would emit sound when touched. The walls of the housing were decorated with colored adhesive tape. Moreover, tactile and auditory stimulation was performed daily throughout the experiment. Hydrocephalic and control rats not exposed to EE (n = 10 per group) were allocated singly in standard cages. All animals were weighed daily and exposed to open-field conditions every 2 days until the end of the experiment when they were sacrificed and the brains removed for histology and immunohistochemistry. Solochrome cyanine staining was performed to assess the thickness of the corpus callosum. The glial fibrillary acidic protein method was used to evaluate reactive astrocytes, and the Ki67 method to assess cellular proliferation in the subventricular zone.

RESULTS

The hydrocephalic animals exposed to EE showed better performance in Open Field tests (p < 0.05), while presenting lower weight gain. In addition, these animals showed better myelination as revealed by magnetization transfer (p < 0.05). Finally, the EE group showed a reduction in reactive astrocytes by means of glial fibrillary acidic protein immunostaining and preservation of the proliferation potential of progenitor cells.

CONCLUSION

The results suggest that EE can protect the developing brain against damaging effects caused by hydrocephalus.

NADPH oxidase-derived H2O2 mediates the regulatory effects of microglia on astrogliosis in experimental models of Parkinson's disease

Astrogliosis has long been recognized in Parkinson's disease (PD), the most common neurodegenerative movement disorder. However, the mechanisms of how astroglia become activated remain unclear. Reciprocal interactions between microglia and astroglia play a pivotal role in regulating the activities of astroglia. The purpose of this study is to investigate the mechanism by which microglia regulate astrogliosis by using lipopolysaccharide (LPS) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse PD models. We found that the activation of microglia preceded astroglia in the substantia nigra of mice treated with either LPS or MPTP. Furthermore, suppression of microglial activation by pharmacological inhibition or genetic deletion of NADPH oxidase (NOX2) in mice attenuated astrogliosis. The important role of NOX2 in microglial regulation of astrogliosis was further mirrored in a mixed-glia culture system. Mechanistically, H₂O₂, a product of microglial NOX2 activation, serves as a direct signal to regulate astrogliosis. Astrogliosis was induced by H₂O₂ through a process in which extracellularly generated H₂O₂ diffused into the cytoplasm and subsequently stimulated activation of transcription factors, STAT1 and STAT3. STAT1/3 activation regulated the immunological functions of H₂O₂-induced astrogliosis since AG490, an inhibitor of STAT1/3, attenuated the gene expressions of both proinflammatory and neurotrophic factors in H₂O₂-treated astrocyte. Our findings indicate that microglial NOX2-generated H₂O₂ is able to regulate the immunological functions of astroglia via a STAT1/3-dependent manner, providing additional evidence for the immune pathogenesis and therapeutic studies of PD.

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Microglia are capable of regulating the immunological functions of astrogliosis in Parkinson's disease.

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NADPH oxidase-derived H₂O₂ is recognized as a paracrine signal for microglial regulation of astrogliosis.

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Transcription factors STAT1 and STAT3 play pivotal roles in H₂O₂-induced astroglial activation.

FcRγ-dependent immune activation initiates astrogliosis during the asymptomatic phase of Sandhoff disease model mice

Sandhoff disease (SD) is caused by the loss of β-hexosaminidase (Hex) enzymatic activity in lysosomes resulting from Hexb mutations. In SD patients, the Hex substrate GM2 ganglioside accumulates abnormally in neuronal cells, resulting in neuronal loss, microglial activation, and astrogliosis. Hexb^−/− mice, which manifest a phenotype similar to SD, serve as animal models for examining the pathophysiology of SD. Hexb^−/− mice reach ~8 weeks without obvious neurological defects; however, trembling begins at 12 weeks and is accompanied by startle reactions and increased limb tone. These symptoms gradually become severe by 16–18 weeks. Immune reactions caused by autoantibodies have been recently associated with the pathology of SD. The inhibition of immune activation may represent a novel therapeutic target for SD. Herein, SD mice (Hexb^−/−) were crossed to mice lacking an activating immune receptor (FcRγ^−/−) to elucidate the potential relationship between immune responses activated through SD autoantibodies and astrogliosis. Microglial activation and astrogliosis were observed in cortices of Hexb^−/− mice during the asymptomatic phase, and were inhibited in Hexb^−/−FcRγ^−/− mice. Moreover, early astrogliosis and impaired motor coordination in Hexb^−/− mice could be ameliorated by immunosuppressants, such as FTY720. Our findings demonstrate the importance of early treatment and the therapeutic effectiveness of immunosuppression in SD.

Are Shunt Revisions Associated with IQ in Congenital Hydrocephalus? A Meta -Analysis

Although it is generally acknowledged that shunt revisions are associated with reductions in cognitive functions in individuals with congenital hydrocephalus, the literature yields mixed results and is inconclusive. The current study used meta-analytic methods to empirically synthesize studies addressing the association of shunt revisions and IQ in individuals with congenital hydrocephalus. Six studies and three in-house datasets yielded 11 independent samples for meta-analysis. Groups representing lower and higher numbers of shunt revisions were coded to generate effect sizes for differences in IQ scores. Mean effect size across studies was statistically significant, but small (Hedges' g = 0.25, p < 0.001, 95 % CI [0.08, 0.43]) with more shunt revisions associated with lower IQ scores. Results show an association of lower IQ and more shunt revisions of about 3 IQ points, a small effect, but within the error of measurement associated with IQ tests. Although clinical significance of this effect is not clear, results suggest that repeated shunt revisions because of shunt failure is associated with a reduction in cognitive functions.

High fibrosis indices in cerebrospinal fluid of patients with shunt-dependent post-traumatic chronic hydrocephalus

Objective

A possible relationship between fibrosis along the route of cerebrospinal fluid (CSF) flow and the subsequent development of hydrocephalus has been indicated in previous studies. These changes in the fibrosis index may reflect the severity of hydrocephalus and could potentially become a diagnostic tool. The object of this study was to analyze the levels of procollagen type I C-terminal propeptide (PICP), procollagen type III N-terminal propeptide (PIIINP), hyaluronic acid (HA), and laminin (LN) in the CSF of patients with post-traumatic hydrocephalus and determine the significance of their presence.

Subjects and methods

Forty-four patients were included in the study: 24 patients with shunt-dependent post-traumatic hydrocephalus (group A - hydrocephalus group); ten brain trauma patients without any sign of hydrocephalus (group B - trauma group); ten patients without brain trauma and hydrocephalus (group C - normal control group). CSF levels of PICP, PIIINP, HA, LN and transforming growth factor-β1(TGF-β1) were detected using enzyme-linked immunosorbent assay (ELISA).

Results

Levels of PICP, PIIINP, HA, and LN in the group of hydrocephalus patients were significantly higher than those in the post-trauma patients without hydrocephalus (p < 0.05) and normal control patients (p < 0.05). Moreover, the increased levels of PICP, PIIINP, HA, and LN were positively correlated with the level of TGF-β1 (p < 0.05).

Conclusion

We demonstrated an increase of fibrosis factors including PICP, PIIINP, HA, and LN, that was positively correlated with TGF-β1 levels. This indicates an important role for the process of fibrosis in the development of post-traumatic chronic hydrocephalus and shows the potential utility of PICP, PIIINP, HA, and LN as a diagnostic index in shunt-dependent post-traumatic chronic hydrocephalus.

Ventricular-subcutaneous shunt for the treatment of experimental hydrocephalus in young rats: technical note

BACKGROUND

Hydrocephalus is a complex disease that affects cerebrospinal fluid (CSF) dynamics and is very common in children. To this date, CSF shunting is still the standard treatment for childhood hydrocephalus, but, nevertheless, the effects of such an operation on the developing brain are widely unknown. To help overcome this, experimental models of CSF shunts are surely very useful tools.

OBJECTIVE

The objective of this study was to describe a feasible and reliable technique of an adapted ventricular-subcutaneous shunt for the treatment of kaolin-induced hydrocephalus in young rats.

METHODS

We developed a ventricular-subcutaneous shunt (VSCS) technique which was used in 31 Wistar young rats with kaolin-induced hydrocephalus. Hydrocephalus was induced at 7 days of age, and shunt implantation was performed 7 days later. Our technique used a 0.7-mm gauge polypropylene catheter tunneled to a subcutaneous pocket created over the animal's back and inserted into the right lateral ventricle. All animals were sacrificed 14 days after shunt insertion.

RESULTS

Twenty-four rats survived and remained well until the study was ended. No major complications were seen. Their weight gain went back to normal. They all underwent ambulatory behavioral testing prior and after VSCS, which showed improvement in their motor skills. We have also obtained magnetic resonance (MR) scans of 16 pups confirming reduction of ventricular size after shunting and indicating effective treatment. Histopathological analysis of brain samples before and after shunting showed reversion of ependymal and corpus callosum disruption, as well as fewer reactive astrocytes in shunted animals.

CONCLUSIONS

An experimental CSF shunt technique was devised. Excessive CSF of hydrocephalic rats is diverted into the subcutaneous space where it can be resorbed. This technique has a low complication rate and is effective. It might be applied to various types of experimental studies involving induction and treatment of hydrocephalus.

Diffusion tensor imaging with direct cytopathological validation: characterisation of decorin treatment in experimental juvenile communicating hydrocephalus

BACKGROUND

In an effort to develop novel treatments for communicating hydrocephalus, we have shown previously that the transforming growth factor-β antagonist, decorin, inhibits subarachnoid fibrosis mediated ventriculomegaly; however decorin's ability to prevent cerebral cytopathology in communicating hydrocephalus has not been fully examined. Furthermore, the capacity for diffusion tensor imaging to act as a proxy measure of cerebral pathology in multiple sclerosis and spinal cord injury has recently been demonstrated. However, the use of diffusion tensor imaging to investigate cytopathological changes in communicating hydrocephalus is yet to occur. Hence, this study aimed to determine whether decorin treatment influences alterations in diffusion tensor imaging parameters and cytopathology in experimental communicating hydrocephalus. Moreover, the study also explored whether diffusion tensor imaging parameters correlate with cellular pathology in communicating hydrocephalus.

METHODS

Accordingly, communicating hydrocephalus was induced by injecting kaolin into the basal cisterns in 3-week old rats followed immediately by 14 days of continuous intraventricular delivery of either human recombinant decorin (n = 5) or vehicle (n = 6). Four rats remained as intact controls and a further four rats served as kaolin only controls. At 14-days post-kaolin, just prior to sacrifice, routine magnetic resonance imaging and magnetic resonance diffusion tensor imaging was conducted and the mean diffusivity, fractional anisotropy, radial and axial diffusivity of seven cerebral regions were assessed by voxel-based analysis in the corpus callosum, periventricular white matter, caudal internal capsule, CA1 hippocampus, and outer and inner parietal cortex. Myelin integrity, gliosis and aquaporin-4 levels were evaluated by post-mortem immunohistochemistry in the CA3 hippocampus and in the caudal brain of the same cerebral structures analysed by diffusion tensor imaging.

RESULTS

Decorin significantly decreased myelin damage in the caudal internal capsule and prevented caudal periventricular white matter oedema and astrogliosis. Furthermore, decorin treatment prevented the increase in caudal periventricular white matter mean diffusivity (p = 0.032) as well as caudal corpus callosum axial diffusivity (p = 0.004) and radial diffusivity (p = 0.034). Furthermore, diffusion tensor imaging parameters correlated primarily with periventricular white matter astrocyte and aquaporin-4 levels.

CONCLUSIONS

Overall, these findings suggest that decorin has the therapeutic potential to reduce white matter cytopathology in hydrocephalus. Moreover, diffusion tensor imaging is a useful tool to provide surrogate measures of periventricular white matter pathology in communicating hydrocephalus.

Abnormal Injury Response in Spontaneous Mild Ventriculomegaly Wistar Rat Brains: A Pathological Correlation Study of Diffusion Tensor and Magnetization Transfer Imaging in Mild Traumatic Brain Injury

Spontaneous mild ventriculomegaly (MVM) was previously reported in ∼43% of Wistar rats in association with vascular anomalies without phenotypic manifestation. This mild traumatic brain injury (TBI) weight drop model study investigates whether MVM rats (n = 15) have different injury responses that could inadvertently complicate the interpretation of imaging studies compared with normal rats (n = 15). Quantitative MRI, including diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI), and immunohistochemistry (IHC) analysis were used to examine the injury pattern up to 8 days post-injury in MVM and normal rats. Prior to injury, the MVM brain showed significant higher mean diffusivity, axial diffusivity, and radial diffusivity, and lower fractional anisotropy (FA) and magnetization transfer ratio (MTR) in the corpus callosum than normal brain (p < 0.05). Following TBI, normal brains exhibited significant decreases of FA in the corpus callosum, whereas MVM brains demonstrated insignificant changes in FA, suggesting less axonal injury. At day 8 after mild TBI, MTR of the normal brains significantly decreased whereas the MTR of the MVM brains significantly increased. IHC staining substantiated the MRI findings, demonstrating limited axonal injury with significant increase of microgliosis and astrogliosis in MVM brain compared with normal animals. The radiological-pathological correlation data showed that both DTI and MTI were sensitive in detecting mild diffuse brain injury, although DTI metrics were more specific in correlating with histologically identified pathologies. Compared with the higher correlation levels reflecting axonal injury pathology in the normal rat mild TBI, the DTI and MTR metrics were more affected by the increased inflammation in the MVM rat mild TBI. Because MVM Wistar rats appear normal, there was a need to screen rats prior to TBI research to rule out the presence of ventriculomegaly, which may complicate the interpretation of imaging and IHC observations.

Rescue of a Mouse Model of Spinal Muscular Atrophy With Respiratory Distress Type 1 by AAV9-IGHMBP2 Is Dose Dependent

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is an autosomal recessive disease occurring during childhood. The gene responsible for disease development is a ubiquitously expressed protein, IGHMBP2. Mutations in IGHMBP2 result in the loss of α-motor neurons leading to muscle atrophy in the distal limbs accompanied by respiratory complications. Although genetically and clinically distinct, proximal SMA is also caused by the loss of a ubiquitously expressed gene (SMN). Significant preclinical success has been achieved in proximal SMA using viral-based gene replacement strategies. We leveraged the technologies employed in SMA to demonstrate gene replacement efficacy in an SMARD1 animal model. Intracerebroventricular (ICV) injection of single-stranded AAV9 expressing the full-length cDNA of IGHMBP2 in a low dose led to a significant level of rescue in treated SMARD1 animals. Consistent with drastically increased survival, weight gain, and strength, the rescued animals demonstrated a significant improvement in muscle, NMJ, motor neurons, and axonal pathology. In addition, increased levels of IGHMBP2 in lumbar motor neurons verified the efficacy of the virus to transduce the target tissues. Our results indicate that AAV9-based gene replacement is a viable strategy for SMARD1, although dosing effects and potential negative impacts of high dose and ICV injection should be thoroughly investigated.

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.

Increased levels of tumour necrosis factor alpha (TNFα) but not transforming growth factor-beta 1 (TGFβ1) are associated with the severity of congenital hydrocephalus in the hyh mouse

AIMS

Here, we tested the hypothesis that glial responses via the production of cytokines such as transforming growth factor-beta 1 (TGFβ1) and tumour necrosis factor alpha (TNFα), which play important roles in neurodegenerative diseases, are correlated with the severity of congenital hydrocephalus in the hyh mouse model. We also searched for evidence of this association in human cases of primary hydrocephalus.

METHODS

Hyh mice, which exhibit either severe or compensated long-lasting forms of hydrocephalus, were examined and compared with wild-type mice. TGFβ1, TNFα and TNFαR1 mRNA levels were quantified using real-time PCR. TNFα and TNFαR1 were immunolocalized in the brain tissues of hyh mice and four hydrocephalic human foetuses relative to astroglial and microglial reactions.

RESULTS

The TGFβ1 mRNA levels were not significantly different between hyh mice exhibiting severe or compensated hydrocephalus and normal mice. In contrast, severely hydrocephalic mice exhibited four- and two-fold increases in the mean levels of TNFα and TNFαR1, respectively, compared with normal mice. In the hyh mouse, TNFα and TNFαR1 immunoreactivity was preferentially detected in astrocytes that form a particular periventricular reaction characteristic of hydrocephalus. However, these proteins were rarely detected in microglia, which did not appear to be activated. TNFα immunoreactivity was also detected in the glial reaction in the small group of human foetuses exhibiting hydrocephalus that were examined.

CONCLUSIONS

In the hyh mouse model of congenital hydrocephalus, TNFα and TNFαR1 appear to be associated with the severity of the disease, probably mediating the astrocyte reaction, neurodegenerative processes and ischaemia.

Dual-porosity poroviscoelasticity and quantitative hydromechanical characterization of the brain tissue with experimental hydrocephalus data

Hydromechanical brain models often involve constitutive relations which must account for soft tissue deformation and creep, together with the interstitial fluid movement and exchange through capillaries. The interaction of rather unknown mechanisms which produce, absorb, and circulate the cerebrospinal fluid within the central nervous system can further add to their complexity. Once proper models for these phenomena or processes are selected, estimation of the associated parameters could be even more challenging. This paper presents the results of a consistent, coupled poroviscoelastic modeling and characterization of the brain tissue as a dual-porosity system. The model draws from Biot's theory of poroviscoelasticity, and adopts the generalized Kelvin's rheological description of the viscoelastic tissue behavior. While the interstitial space serves as the primary porosity through which the bulk flow of the interstitial fluid occurs, a secondary porosity network comprising the capillaries and venous system allows for its partial absorption into the blood. The correspondence principle is used in deriving a time-dependent analytical solution to the proposed model. It allows for identical poroelastic formulation of the original poroviscoelastic problem in the Laplace transform space. Hydrocephalus generally refers to a class of medical conditions which share the ventricles enlargement as a common feature. A set of published data from induced hydrocephalus and follow-up perfusion of cats' brains is used for quantitative characterization of the proposed model. A selected portion of these data including the ventricular volume and rate of fluid absorption from the perfused brain, together with the forward model solution, is utilized via an inverse problem technique to find proper estimations of the model parameters. Results show significant improvement in model predictions of the experimental data. The convoluted and coupled solution results are presented through the time-dependent plots of the ventricular volume undergoing the perfusion experiment. The plots demonstrate the intricate interplay of viscous and poroelastic diffusive time scales, and their competition in reaching the steady state response of the system.

Imaging of spontaneous ventriculomegaly and vascular malformations in Wistar rats: implications for preclinical research

Wistar rats are widely used in biomedical research and commonly serve as a model organism in neuroscience studies. In most cases when noninvasive imaging is not used, studies assume a consistent baseline condition in rats that lack visible differences. While performing a series of traumatic brain injury studies, we discovered mild spontaneous ventriculomegaly in 70 (43.2%) of 162 Wistar rats that had been obtained from 2 different vendors. Advanced magnetic resonance (MR) imaging techniques, including MR angiography and diffusion tensor imaging, were used to evaluate the rats. Multiple neuropathologic abnormalities, including presumed arteriovenous malformations, aneurysms, cysts, white matter lesions, and astrogliosis were found in association with ventriculomegaly. Postmortem microcomputed tomography and immunohistochemical staining confirmed the presence of aneurysms and arteriovenous malformations. Diffusion tensor imaging showed significant decreases in fractional anisotropy and increases in mean diffusivity, axial diffusivity, and radial diffusivity in multiple white matter tracts (p < 0.05). These results could impact the interpretation, for example, of a pseudo-increase of axon integrity and a pseudo-decrease of myelin integrity, based on characteristics intrinsic to rats with ventriculomegaly. We suggest the use of baseline imaging to prevent the inadvertent introduction of a high degree of variability in preclinical studies of neurologic disease or injury in Wistar rats.

Fingerprint changes in CSF composition associated with different aetiologies in human neonatal hydrocephalus: inflammatory cytokines

PURPOSE

Hydrocephalus (HC) has a multifactorial and complex picture of pathophysiology due to aetiology, age at and duration since onset. We have previously identified distinctions in markers of cell death associated with different aetiologies. Here, we examined cerebrospinal fluid (CSF) from human HC neonates for cytokines to identify further distinguishing features of different aetiologies.

METHODS

CSF was collected during routine lumbar puncture or ventricular tap from neonates with hydrocephalus, or with no neurological condition (normal controls). Total protein, Fas receptor, Fas ligand, stem cell factor (SCF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin growth factor-1 (IGF-1), tumour necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) were measured and compared between 8 unaffected and 28 HC neonatal CSF samples.

RESULTS

Total protein was significantly (P < 0.05) raised in late-onset hydrocephalus (LOH). Fas receptor was raised (P < 0.05) in post-haemorrhagic hydrocephalus (PHH) and spina bifida with hydrocephalus (SB/HC), but no difference in Fas ligand was found. SCF was raised (P < 0.05) in SB/HC. HGF was found in all HC and was increased (P < 0.01) in PHH. Increased VEGF was found in PHH (P < 0.01) and SB/HC (P < 0.05). Variable levels of IL-6, TNF-α and IGF-1 were found in all HC groups compared with none in normal.

CONCLUSIONS

LOH was unusual with significantly raised total protein indicating an inflammatory state. Increased Fas receptor, VEGF, IGF-1 and HGF suggest anti-apoptotic and repair mechanism activation. By contrast, elevated TNF-α and IL-6 indicate inflammatory processes in these neonatal brains. Taken with our previous study, these data indicate that different pathophysiology, inflammation and repair are occurring in HC of different aetiologies and that additional treatment strategies may benefit these infants in addition to fluid diversion.

Structure and function of the ependymal barrier and diseases associated with ependyma disruption

The neuroepithelium is a germinal epithelium containing progenitor cells that produce almost all of the central nervous system cells, including the ependyma. The neuroepithelium and ependyma constitute barriers containing polarized cells covering the embryonic or mature brain ventricles, respectively; therefore, they separate the cerebrospinal fluid that fills cavities from the developing or mature brain parenchyma. As barriers, the neuroepithelium and ependyma play key roles in the central nervous system development processes and physiology. These roles depend on mechanisms related to cell polarity, sensory primary cilia, motile cilia, tight junctions, adherens junctions and gap junctions, machinery for endocytosis and molecule secretion, and water channels. Here, the role of both barriers related to the development of diseases, such as neural tube defects, ciliary dyskinesia, and hydrocephalus, is reviewed.

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.

A novel rat model to study the role of intracranial pressure modulation on optic neuropathies

Reduced intracranial pressure is considered a risk factor for glaucomatous optic neuropathies. All current data supporting intracranial pressure as a glaucoma risk factor comes from retrospective and prospective studies. Unfortunately, there are no relevant animal models for investigating this link experimentally. Here we report a novel rat model that can be used to study the role of intracranial pressure modulation on optic neuropathies. Stainless steel cannulae were inserted into the cisterna magna or the lateral ventricle of Sprague-Dawley and Brown Norway rats. The cannula was attached to a pressure transducer connected to a computer that recorded intracranial pressure in real-time. Intracranial pressure was modulated manually by adjusting the height of a column filled with artificial cerebrospinal fluid in relation to the animal’s head. After data collection the morphological appearance of the brain tissue was analyzed. Based on ease of surgery and ability to retain the cannula, Brown Norway rats with the cannula implanted in the lateral ventricle were selected for further studies. Baseline intracranial pressure for rats was 5.5±1.5 cm water (n=5). Lowering of the artificial cerebrospinal fluid column by 2 cm and 4 cm below head level reduced ICP to 3.7±1.0 cm water (n=5) and 1.5±0.6 cm water (n=4), a reduction of 33.0% and 72.7% below baseline. Raising the cerebrospinal fluid column by 4 cm increased ICP to 7.5±1.4 cm water (n=2) corresponding to a 38.3% increase in intracranial pressure. Histological studies confirmed correct cannula placement and indicated minimal invasive damage to brain tissues. Our data suggests that the intraventricular cannula model is a unique and viable model that can be used to study the effect of altered intracranial pressure on glaucomatous optic neuropathies.

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.