Insights into the pathogenesis of hydrocephalus from transgenic and experimental animal models

CSF hypersecretion versus impaired CSF absorption in posthemorrhagic hydrocephalus: a systematic review

BACKGROUND

The molecular mechanisms underlying development of posthemorrhagic hydrocephalus (PHH) remain elusive. The aim of this systematic review was to evaluate existing literature on increased CSF secretion and impaired CSF absorption as pathogenic contributors to CSF accumulation in neonatal and adult PHH.

METHODS

The systematic review was conducted in accordance with the PRISMA guidelines. Relevant studies published before March 11th, 2023, were identified from PubMed and reference lists. Studies were screened for eligibility using predefined inclusion and exclusion criteria. Data from eligible studies were extracted and potential sources of bias were evaluated.

RESULTS

Nineteen studies quantified CSF production rates and/or CSF absorption capacity in human patients with PHH or animals with experimentally induced PHH. Increased CSF production was reported as early as 24 h and as late as 28 days post ictus in six out of eight studies quantifying CSF production rates in animals with experimentally induced PHH. Impaired CSF absorption was reported in all four studies quantifying CSF absorption capacity in human patients with PHH and in seven out of nine studies quantifying CSF absorption capacity in animals with experimentally induced PHH. Impaired CSF absorption was reported as early as 30 min and as late as 10 months post ictus.

CONCLUSIONS

The pathological CSF accumulation in PHH likely arises from a combination of increased CSF secretion and impaired CSF absorption, which may manifest at different time scales following a hemorrhagic event. Emergent evidence on increased CSF secretion by the choroid plexus may herald a paradigm shift in our understanding of PHH.

Intraventricular hemorrhage in term infants: a single institutional experience between 2016 and 2020

PURPOSE

Intraventricular hemorrhage (IVH) of prematurity is a known complication of preterm birth. Intraventricular hemorrhage in term infants is much less commonly encountered. To address the lack of information in the current literature concerning this demographic, we offer demographic and image findings that demonstrate etiology and predict the need for permanent cerebrospinal fluid (CSF) diversion.

METHODS

A prospectively maintained database was queried for all patients with intraventricular hemorrhage from 2016 to 2020 treated at our institution. Demographic data and etiology were collected, along with need for and timing of surgical intervention.

RESULTS

A total of 150 IVH patients were identified. Of these patients, 138 were excluded due to prematurity. Twelve patients were born at term with IVH. All patients were followed for at least 8 months. Seven patients (58.3%) underwent ventriculoperitoneal (VP) shunt placement, performed between 4 days and 4 months of age. Superficial siderosis detected by MRI during in-patient stay or follow-up showed a sensitivity of 100% and specificity of 60% for the future development of post-hemorrhagic hydrocephalus (PHH) (p < 0.05). All full-term infants who developed PHH (n = 7, 58.3%) obtained a VP shunt.

CONCLUSION

IVH in term infants occurs infrequently when compared to IVH of prematurity. Etiology of IVH in term infants remains difficult to ascertain, but the majority of patients did demonstrate risk factors. The presence of superficial siderosis on MRI significantly predicted the development of PHH and eventual need for CSF diversion.

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.

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.

Functional loss of Ccdc151 leads to hydrocephalus in a mouse model of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder affecting normal structure and function of motile cilia, phenotypically manifested as chronic respiratory infections, laterality defects and infertility. Autosomal recessive mutations in genes encoding for different components of the ciliary axoneme have been associated with PCD in humans and in model organisms. The CCDC151 gene encodes for a coiled-coil axonemal protein that ensures correct attachment of outer dynein arm (ODA) complexes to microtubules. A correct arrangement of dynein arm complexes is required to provide the proper mechanical force necessary for cilia beat. Loss-of-function mutations in CCDC151 in humans leads to PCD disease with respiratory distress and defective left-right body asymmetry. In mice with the Ccdc151Snbl loss-of-function mutation (Snowball mutant), left-right body asymmetry with heart defects have been observed. Here, we demonstrate that loss of Ccdc151 gene function via targeted gene deletion in mice leads to perinatal lethality and congenital hydrocephalus. Microcomputed tomography (microCT) X-ray imaging of Ccdc151-β-galactosidase reporter expression in whole-mount brain and histological analysis show that Ccdc151 is expressed in ependymal cells lining the ventricular brain system, further confirming the role of Ccdc151 dysfunction in hydrocephalus development. Analyzing the features of hydrocephalus in the Ccdc151-knockout animals by microCT volumetric imaging, we observe continuity of the aqueduct of Sylvius, indicating the communicating nature of hydrocephalus in the Ccdc151-knockout animals. Congenital defects in left-right asymmetry and male infertility have been also observed in Ccdc151-null animals. Ccdc151 gene deletion in adult animals results in abnormal sperm counts and defective sperm motility.This article has an associated First Person interview with the joint first authors of the paper.

Characterization of spontaneous hydrocephalus development in the young atherosclerosis-prone mice

Little has been reported on whether abnormal lipid metabolism affects hydrocephalus, although congenital malformations and infectious diseases are major causal factors for hydrocephalus development. In a study on the pathogenesis of atherogenesis in mice, we unexpectedly discovered that hydrocephalus occurred in partial apolipoptotein E (apoE) and low-density lipoprotein receptor (LDLR) double-knockout (apoE/LDLR) mice fed either chow or a high-fat and high-cholesterol diet between the ages of 4 and 12 weeks. In the 12-week-old high-fat and high-cholesterol group, the incidence rate was as high as 15%. Transcription levels of transforming growth factor-β1 (TGF-β1), Smad3, Smad4, and Smad7 in the cortex of the hydrocephalic cerebrum were significant downregulated in 4-week-old mice, but were increased in the 8 and 12-week-old groups compared with that of age-matched nonhydrocephalic mice. The mRNA level of tissue inhibitor of metalloproteinases 1 was significantly increased, whereas matrix metalloproteinase-9 was lower in hydrocephalic mice of all ages. The translation level of TGF-β1 increased in the hydrocephalic brains of 8 and 12-week-old mice. This study provides primary evidence for the connection between lipid metabolic disorder and hydrocephalus development. This may suggest that both hyperglyceridemia and hypercholesterolemia are harmful factors in hydrocephalus development because of adverse effects on TGF-β1/Smad signaling in the brain.

Opportunities in posthemorrhagic hydrocephalus research: outcomes of the Hydrocephalus Association Posthemorrhagic Hydrocephalus Workshop

The Hydrocephalus Association Posthemorrhagic Hydrocephalus Workshop was held on July 25 and 26, 2016 at the National Institutes of Health. The workshop brought together a diverse group of researchers including pediatric neurosurgeons, neurologists, and neuropsychologists with scientists in the fields of brain injury and development, cerebrospinal and interstitial fluid dynamics, and the blood-brain and blood-CSF barriers. The goals of the workshop were to identify areas of opportunity in posthemorrhagic hydrocephalus research and encourage scientific collaboration across a diverse set of fields. This report details the major themes discussed during the workshop and research opportunities identified for posthemorrhagic hydrocephalus. The primary areas include (1) preventing intraventricular hemorrhage, (2) stopping primary and secondary brain damage, (3) preventing hydrocephalus, (4) repairing brain damage, and (5) improving neurodevelopment outcomes in posthemorrhagic hydrocephalus.

Effects of Melatonin on the Cerebellum of Infant Rat Following Kaolin-Induced Hydrocephalus: a Histochemical and Immunohistochemical Study

Hydrocephalus is a developmental disorder causing abnormally collected cerebrospinal fluid within the cerebral ventricles. It leads to bigger skulls and many dysfunctions related to the nervous system. Here, we addressed whether exogenous melatonin administration could reverse the clinical features of kaolin-induced hydrocephalus in infantile rats. A controlled double-blinded study was conducted in 2-week-old 45 Wistar albino rats, which were divided into three groups: Group A, the control group, received intracisternal sham injection with solely the needle insertion; group B, the hydrocephalus group, was treated with isotonic NaCl after kaolin injection; and group C, the hydrocephalus + melatonin group, was given i.p. exogenous melatonin at a dose of 0.5 mg/100 g body weight after kaolin injection. Histological and immunohistochemical analyses were performed after the induction of hydrocephalus and melatonin administration. Glial fibrillary acidic protein was stained by immunohistochemical method. TUNEL method was used to define and quantitate apoptosis in the cerebellar tissues. Statistical analysis was performed by nonparametric Kruskal-Wallis H test, and once significance was determined among means, post hoc pairwise comparisons were carried out using Mann-Whitney U test. We found that melatonin administration significantly ameliorated ratio of substantia grisea area/substantia alba area in the cerebellum of infantile rats. Histologically, there was a significant reduction in the number of cerebellar apoptotic cells after the hydrocephalus induced by kaolin (P < 0.05). Our results clearly revealed that the histopathological changes in the cerebellum were reversed by systemic melatonin administration in infantile rats with kaolin-induced hydrocephalus. Nevertheless, further studies are needed to suggest melatonin as a candidate protective drug in children with hydrocephalus.

Dabigatran ameliorates post-haemorrhagic hydrocephalus development after germinal matrix haemorrhage in neonatal rat pups

We aim to determine if direct thrombin inhibition by dabigatran will improve long-term brain morphological and neurofunctional outcomes and if potential therapeutic effects are dependent upon reduced PAR-1 stimulation and consequent mTOR activation. Germinal matrix haemorrhage was induced by stereotaxically injecting 0.3 U type VII-S collagenase into the germinal matrix of P7 rat pups. Animals were divided into five groups: sham, vehicle (5% DMSO), dabigatran intraperitoneal, dabigatran intraperitoneal + TFLLR-NH₂ (PAR-1 agonist) intranasal, SCH79797 (PAR-1 antagonist) intraperitoneal, and dabigatran intranasal. Neurofunctional outcomes were determined by Morris water maze, rotarod, and foot fault evaluations at three weeks. Brain morphological outcomes were determined by histological Nissl staining at four weeks. Expression levels of p-mTOR/p-p70s6k at three days and vitronectin/fibronectin at 28 days were quantified. Intranasal and intraperitoneal dabigatran promoted long-term neurofunctional recovery, improved brain morphological outcomes, and reduced intracranial pressure at four weeks after GMH. PAR-1 stimulation tended to reverse dabigatran's effects on post-haemorrhagic hydrocephalus development. Dabigatran also reduced expression of short-term p-mTOR and long-term extracellular matrix proteins, which tended to be reversed by PAR-1 agonist co-administration. PAR-1 inhibition alone, however, did not achieve the same therapeutic effects as dabigatran administration.

PPARγ-induced upregulation of CD36 enhances hematoma resolution and attenuates long-term neurological deficits after germinal matrix hemorrhage in neonatal rats

Germinal matrix hemorrhage remains the leading cause of morbidity and mortality in preterm infants in the United States with little progress made in its clinical management. Survivors are often afflicted with long-term neurological sequelae, including cerebral palsy, mental retardation, hydrocephalus, and psychiatric disorders. Blood clots disrupting normal cerebrospinal fluid circulation and absorption after germinal matrix hemorrhage are thought to be important contributors towards post-hemorrhagic hydrocephalus development. We evaluated if upregulating CD36 scavenger receptor expression in microglia and macrophages through PPARγ stimulation, which was effective in experimental adult cerebral hemorrhage models and is being evaluated clinically, will enhance hematoma resolution and ameliorate long-term brain sequelae using a neonatal rat germinal matrix hemorrhage model. PPARγ stimulation (15d-PGJ2) increased short-term PPARγ and CD36 expression levels as well as enhanced hematoma resolution, which was reversed by a PPARγ antagonist (GW9662) and CD36 siRNA. PPARγ stimulation (15d-PGJ2) also reduced long-term white matter loss and post-hemorrhagic ventricular dilation as well as improved neurofunctional outcomes, which were reversed by a PPARγ antagonist (GW9662). PPARγ-induced upregulation of CD36 in macrophages and microglia is, therefore, critical for enhancing hematoma resolution and ameliorating long-term brain sequelae.

Yap is required for ependymal integrity and is suppressed in LPA-induced hydrocephalus

Timely generation and normal maturation of ependymal cells along the aqueduct are critical for preventing physical blockage between the third and fourth ventricles and the development of fetal non-communicating hydrocephalus. Our study identifies Yap, the downstream effector of the evolutionarily conserved Hippo pathway, as a central regulator for generating developmentally controlled ependymal cells along the ventricular lining of the aqueduct. Yap function is necessary for proper proliferation of progenitors and apical attachment of ependymal precursor cells. Importantly, an injury signal initiated by lysophosphatidic acid (LPA), an upstream regulator of Yap that can cause fetal haemorrhagic hydrocephalus, deregulates Yap in the developing aqueduct. LPA exposure leads to the loss of N-cadherin concentrations at the apical endfeet, which can be partially restored by forced Yap expression and more efficiently by phosphomimetic Yap. These results reveal a novel function of Yap in retaining tissue junctions during normal development and after fetal brain injury.

PAR-1, -4, and the mTOR Pathway Following Germinal Matrix Hemorrhage

Germinal matrix hemorrhage (GMH) is the most common cause of neurological complications of prematurity and has lasting implications. PAR-1 and PAR-4 receptors are involved with upstream signaling pathways following brain hemorrhage in adult models of stroke, of which the mammalian target of rapamycin (mTOR) is a potential downstream mediator. Therefore, we hypothesized a role for PAR-1, -4/ mTOR signaling following GMH brain injury. Postnatal day 7 Sprague-Dawley rats were subjected to GMH through stereotactic infusion of collagenase into the right ganglionic eminence. Rodents were euthanized at 72 h (short term), or 4 weeks (long term). Short-term mTOR expression was evaluated by Western blot in the context of PAR-1 (SCH-79797) and PAR-4 (P4pal10) inhibition. Pups in the long-term group were administered the selective mTOR inhibitor (rapamycin) with neurobehavioral and brain pathological examinations performed at 4 weeks. Pharmacological PAR-1, -4 antagonism normalized the increased mTOR expression following GMH. Early inhibition of mTOR by rapamycin improved long-term outcomes in rats. Mammalian-TOR signaling plays an important role in brain injury following neonatal GMH, possibly involving upstream PAR-1, -4 mechanisms.

Cyclooxygenase-2 Inhibition Provides Lasting Protection Following Germinal Matrix Hemorrhage in Premature Infant Rats

Germinal matrix hemorrhage (GMH) is a major cause of brain damage in prematurity and has long-lasting neurological implications. The development of brain inflammation contributes to brain injury, leading to a lifetime of neurologic deficits. PAR-1 and 4 receptors are involved with inflammatory pathways after brain hemorrhage in adult models of stroke, of which cyclooxygenase-2 (COX-2) is a potential mediator. We therefore hypothesized a role for PAR-1, 4/ COX-2 signaling following GMH. Postnatal day 7 Sprague-Dawley rats were subjected to GMH induction, which entailed stereotactic collagenase infusion into the ganglionic eminence. Animals were euthanized at two time points: 72 h (short-term) or 4 weeks (long-term). Short-term COX-2 expression was evaluated in the context of PAR-1 (SCH-79797) and PAR-4 (P4pal10) inhibition. Pups in the long-term group were administered the selective COX-2 inhibitor (NS-398); and the neurobehavioral and pathological examinations were performed 4 weeks later. Pharmacological PAR-1, 4 antagonism normalized COX-2 expression following GMH and reduced hydrocephalus. Early inhibition of COX-2 by NS-398 improved long-term neurobehavioral outcomes. COX-2 signaling plays an important role in brain injury following neonatal GMH, possibly through upstream PAR-1, 4 receptor mechanisms.

Decorin alleviated chronic hydrocephalus via inhibiting TGF-β1/Smad/CTGF pathway after subarachnoid hemorrhage in rats

Chronic hydrocephalus is one of the severe complications after subarachnoid hemorrhage (SAH). However, there is no efficient treatment for the prevention of chronic hydrocephalus, partially due to poor understanding of underlying pathogenesis, subarachnoid fibrosis. Transforming growth factor-β1(TGF-β1) is a potent fibrogenic factor implicated in wide range of fibrotic diseases. To investigate whether decorin, a natural antagonist for TGF-β1, protects against subarachnoid fibrosis and chronic hydrocephalus after SAH, two-hemorrhage-injection SAH model was conducted in 6-week-old rats. Recombinant human decorin(rhDecorin) (30ug/2ul) was administered before blood injection and on the 10th day after SAH. TGF-β1, p-Smad2/3, connective tissue growth factor (CTGF), collagen I and pro-collagen I c-terminal propeptide were assessed via western blotting, enzyme-linked immunosorbent assay, radioimmunoassay and immunofluorescence. And neurobehavioral tests and Morris water maze were employed to evaluate long-term neurological functions after SAH. We found that SAH induced heightened activation of TGF-β1/Smad/CTGF axis, presenting as a two peak response of TGF-β1 in cerebrospinal fluid, elevation of TGF-β1, p-Smad2/3, CTGF, collagen I in brain parenchyma and pro-collagen I c-terminal propeptide in cerebrospinal fluid, and increased lateral ventricle index. rhDecorin treatment effectively inhibited up-regulation of TGF-β1, p-Smad2/3, CTGF, collagen I and pro-collagen I c-terminal propeptide after SAH. Moreover, rhDecorin treatment significantly reduced lateral ventricular index and incidence of chronic hydrocephalus after SAH. Importantly, rhDecorin improved neurocognitive deficits after SAH. In conclusion, rhDecorin suppresses extracellular matrix accumulation and following subarachnoid fibrosis via inhibiting TGF-β1/Smad/CTGF pathway, preventing development of hydrocephalus and attenuating long-term neurocognitive defects after SAH.

Protease-activated receptor 1 and 4 signal inhibition reduces preterm neonatal hemorrhagic brain injury

BACKGROUND AND PURPOSE

This study examines the role of thrombin's protease-activated receptor (PAR)-1, PAR-4 in mediating cyclooxygenase-2 and mammalian target of rapamycin after germinal matrix hemorrhage.

METHODS

Germinal matrix hemorrhage was induced by intraparenchymal infusion of bacterial collagenase into the right ganglionic eminence of P7 rat pups. Animals were treated with PAR-1, PAR-4, cyclooxygenase-2, or mammalian target of rapamycin inhibitors by 1 hour, and ≤5 days.

RESULTS

We found increased thrombin activity 6 to 24 hours after germinal matrix hemorrhage, and PAR-1, PAR-4, inhibition normalized cyclooxygenase-2, and mammalian target of rapamycin by 72 hours. Early treatment with NS398 or rapamycin substantially improved long-term outcomes in juvenile animals.

CONCLUSIONS

Suppressing early PAR signal transduction, and postnatal NS398 or rapamycin treatment, may help reduce germinal matrix hemorrhage severity in susceptible preterm infants.

VEGF: a potential target for hydrocephalus

Growth factors are primarily responsible for the genesis, differentiation and proliferation of cells and maintenance of tissues. Given the central role of growth factors in signaling between cells in health and in disease, it is understandable that disruption of growth factor-mediated molecular signaling can cause diverse phenotypic consequences including cancer and neurological conditions. This review will focus on the specific questions of enlarged cerebral ventricles and hydrocephalus. It is also well known that angiogenic factors, such as vascular endothelial growth factor (VEGF), affect tissue permeability through activation of receptors and adhesion molecules; hence, recent studies showing elevations of this factor in pediatric hydrocephalus led to the demonstration that VEGF can induce ventriculomegaly and altered ependyma when infused in animals. In this review, we discuss recent findings implicating the involvement of biochemical and biophysical factors that can induce a VEGF-mimicking effect in communicating hydrocephalus and pay particular attention to the role of the VEGF system as a potential pharmacological target in the treatment of some cases of hydrocephalus. The source of VEGF secretion in the cerebral ventricles, in periventricular regions and during pathologic events including hydrocephalus following hypoxia and hemorrhage is sought. The review is concluded with a summary of potential non-surgical treatments in preclinical studies suggesting several molecular targets including VEGF for hydrocephalus and related neurological disorders.

Acute and delayed deferoxamine treatment attenuates long-term sequelae after germinal matrix hemorrhage in neonatal rats

BACKGROUND AND PURPOSE

This study investigated if acute and delayed deferoxamine treatment attenuates long-term sequelae after germinal matrix hemorrhage (GMH).

METHODS

Bacterial collagenase (0.3 U) was infused intraparenchymally into the right hemispheric ganglionic eminence in P7 rat pups to induce GMH. GMH animals received either deferoxamine or vehicle twice a day for 7 consecutive days. Deferoxamine administration was initiated at either 1 hour or 72 hours post-GMH. Long-term neurocognitive deficits and motor coordination were assessed using Morris water maze, rotarod, and foot fault tests between day 21 to 28 post-GMH. At 28 days post-GMH, brain morphology was assessed and extracellular matrix protein (fibronectin and vitronectin) expression was determined.

RESULTS

Acute and delayed deferoxamine treatment improved long-term motor and cognitive function at 21 to 28 days post-GMH. Attenuated neurofunction was paralleled with improved overall brain morphology at 28 days post-GMH, reducing white matter loss, basal ganglia loss, posthemorrhagic ventricular dilation, and cortical loss. GMH resulted in significantly increased expression of fibronectin and vitronectin, which was reversed by acute and delayed deferoxamine treatment.

CONCLUSIONS

Acute and delayed deferoxamine administration ameliorated long-term sequelae after GMH.

Transcriptome profiling of a multiple recurrent muscle-invasive urothelial carcinoma of the bladder by deep sequencing

Urothelial carcinoma of the bladder (UCB) is one of the commonly diagnosed cancers in the world. The UCB has the highest rate of recurrence of any malignancy. A genome-wide screening of transcriptome dysregulation between cancer and normal tissue would provide insight into the molecular basis of UCB recurrence and is a key step to discovering biomarkers for diagnosis and therapeutic targets. Compared with microarray technology, which is commonly used to identify expression level changes, the recently developed RNA-seq technique has the ability to detect other abnormal regulations in the cancer transcriptome, such as alternative splicing. In this study, we performed high-throughput transcriptome sequencing at ∼50× coverage on a recurrent muscle-invasive cisplatin-resistance UCB tissue and the adjacent non-tumor tissue. The results revealed cancer-specific differentially expressed genes between the tumor and non-tumor tissue enriched in the cell adhesion molecules, focal adhesion and ECM-receptor interaction pathway. Five dysregulated genes, including CDH1, VEGFA, PTPRF, CLDN7, and MMP2 were confirmed by Real time qPCR in the sequencing samples and the additional eleven samples. Our data revealed that more than three hundred genes showed differential splicing patterns between tumor tissue and non-tumor tissue. Among these genes, we filtered 24 cancer-associated alternative splicing genes with differential exon usage. The findings from RNA-Seq were validated by Real time qPCR for CD44, PDGFA, NUMB, and LPHN2. This study provides a comprehensive survey of the UCB transcriptome, which provides better insight into the complexity of regulatory changes during recurrence and metastasis.

Riding the wave of ependymal cilia: genetic susceptibility to hydrocephalus in primary ciliary dyskinesia

Congenital hydrocephalus is a relatively common and debilitating birth defect with several known physiological causes. Dysfunction of motile cilia on the ependymal cells that line the ventricular surface of the brain can result in hydrocephalus by hindering the proper flow of cerebrospinal fluid. As a result, hydrocephalus can be associated with primary ciliary dyskinesia, a rare pediatric syndrome resulting from defects in ciliary and flagellar motility. Although the prevalence of hydrocephalus in primary ciliary dyskinesia patients is low, it is a common hallmark of the disease in mouse models, suggesting that distinct genetic mechanisms underlie the differences in the development and physiology of human and mouse brains. Mouse models of primary ciliary dyskinesia reveal strain-specific differences in the appearance and severity of hydrocephalus, indicating the presence of genetic modifiers segregating in inbred strains. These models may provide valuable insight into the genetic mechanisms that regulate susceptibility to hydrocephalus under the conditions of ependymal ciliary dysfunction.

Pathophysiology of congenital and neonatal hydrocephalus

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

Increased CSF osmolarity reversibly induces hydrocephalus in the normal rat brain

BACKGROUND

Hydrocephalus is a central nervous system (CNS) disorder characterized by the abnormal accumulation of cerebrospinal fluid (CSF) in cerebral ventricles, resulting in their dilatation and associated brain tissue injury. The pathogenesis of hydrocephalus remains unclear; however, recent reports suggest the possible involvement of abnormal osmotic gradients. Here we explore the kinetics associated with manipulating CSF osmolarity on ventricle volume (VV) in the normal rat brain.

METHODS

CSF was made hyper-osmotic by introducing 10KD dextran into the lateral ventricle, either by acute injection at different concentrations or by chronic infusion at a single concentration. The induction and withdrawal kinetics of dextran infusion on VV were explored in both contexts.

RESULTS

Acute intraventricular injection of dextran caused a rapid increase in VV which completely reversed within 24 hours. These kinetics are seemingly independent of CSF osmolarity across a range spanning an order of magnitude; however, the magnitude of the transient increase in VV was proportional to CSF osmolarity. By contrast, continuous intraventricular infusion of dextran at a relatively low concentration caused a more gradual increase in VV which was very slow to reverse when infusion was suspended after five days.

CONCLUSION

We conclude that hyperosmolar CSF is sufficient to produce a proportional degree of hydrocephalus in the normal rat brain, and that this phenomenon exhibits hysteresis if CSF hyperosmolarity is persistent. Thus pathologically-induced increases in CSF osmolarity may be similarly associated with certain forms of clinical hydrocephalus. An improved understanding of this phenomenon and its kinetics may facilitate the development of novel therapies for the treatment of clinical hydrocephalus.

Congenital Hydrocephalus in Genetically Engineered Mice

There is evidence that genetic factors play a role in the complex multifactorial pathogenesis of hydrocephalus. Identification of the genes involved in the development of this neurologic disorder in animal models may elucidate factors responsible for the excessive accumulation of cerebrospinal fluid in hydrocephalic humans. The authors report here a brief summary of findings from 12 lines of genetically engineered mice that presented with autosomal recessive congenital hydrocephalus. This study illustrates the value of knockout mice in identifying genetic factors involved in the development of congenital hydrocephalus. Findings suggest that dysfunctional motile cilia represent the underlying pathogenetic mechanism in 8 of the 12 lines ( Ulk4, Nme5, Nme7, Kif27, Stk36, Dpcd, Ak7, and Ak8). The likely underlying cause in the remaining 4 lines ( RIKEN 4930444A02, Celsr2, Mboat7, and transgenic FZD3) was not determined, but it is possible that some of these could also have ciliary defects. For example, the cerebellar malformations observed in RIKEN 4930444A02 knockout mice show similarities to a number of developmental disorders, such as Joubert, Meckel-Gruber, and Bardet-Biedl syndromes, which involve mutations in cilia-related genes. Even though the direct relevance of mouse models to hydrocephalus in humans remains uncertain, the high prevalence of familial patterns of inheritance for congenital hydrocephalus in humans suggests that identification of genes responsible for development of hydrocephalus in mice may lead to the identification of homologous modifier genes and susceptibility alleles in humans. Also, characterization of mouse models can enhance understanding of important cell signaling and developmental pathways involved in the pathogenesis of hydrocephalus.

Brain abnormalities and glioma-like lesions in mice overexpressing the long isoform of PDGF-A in astrocytic cells

Background

Deregulation of platelet-derived growth factor (PDGF) signaling is a hallmark of malignant glioma. Two alternatively spliced PDGF-A mRNAs have been described, corresponding to a long (L) and a short (S) isoform of PDGF-A. In contrast to PDGF-A(S), the PDGF-A(L) isoform has a lysine and arginine rich carboxy-terminal extension that acts as an extracellular matrix retention motif. However, the exact role of PDGF-A(L) and how it functionally differs from the shorter isoform is not well understood.

Methodology/Principal Findings

We overexpressed PDGF-A(L) as a transgene under control of the glial fibrillary acidic protein (GFAP) promoter in the mouse brain. This directs expression of the transgene to astrocytic cells and GFAP expressing neural stem cells throughout the developing and adult central nervous system. Transgenic mice exhibited a phenotype with enlarged skull at approximately 6-16 weeks of age and they died between 1.5 months and 2 years of age. We detected an increased number of undifferentiated cells in all areas of transgene expression, such as in the subependymal zone around the lateral ventricle and in the cerebellar medulla. The cells stained positive for Pdgfr-α, Olig2 and NG2 but this population did only partially overlap with cells positive for Gfap and the transgene reporter. Interestingly, a few mice presented with overt neoplastic glioma-like lesions composed of both Olig2 and Gfap positive cell populations and with microvascular proliferation, in a wild-type p53 background.

Conclusions

Our findings show that PDGF-A(L) can induce accumulation of immature cells in the mouse brain. The strong expression of NG2, Pdgfr-α and Olig2 in PDGF-A(L) brains suggests that a fraction of these cells are oligodendrocyte progenitors. In addition, accumulation of fluid in the subarachnoid space and skull enlargement indicate that an increased intracranial pressure contributed to the observed lethality.

Decorin and colchicine as potential treatments for post-haemorrhagic ventricular dilatation in a neonatal rat model

BACKGROUND

Post-haemorrhagic ventricular dilatation (PHVD) after intraventricular haemorrhage (IVH) remains a significant problem in preterm infants. Due to serious disadvantages of ventriculoperitoneal shunt dependence, there is an urgent need for non-surgical interventions. Considerable experimental and clinical evidence implicates transforming growth factor β (TGFβ) in the pathogenesis of PHVD. Colchicine and decorin are both compounds with anti-TGFβ properties. The former downregulates TGFβ production and is in clinical use for another fibrotic disease, and the latter inactivates TGFβ.

OBJECTIVES

We hypothesized that administration of decorin or colchicine, which both have anti-TGFβ properties, would reduce ventricular dilatation in a model of PHVD.

METHODS

142 rat pups underwent intraventricular blood injection on postnatal days (PN) 7 and 8. Sixty-nine pups were randomized to colchicine 20 and 50 μg/kg/day or water by gavage for 13 days. Seventy were randomized to decorin 4 mg/kg or saline by intraventricular injection on PN8 and PN13. At PN21, the ventricular area was measured on coronal brain sections. Negative geotaxis was tested at PN14 in controls and in the decorin study group.

RESULTS

Ventricular size was not different between animals receiving either drug or water/saline. Intraventricular blood impaired neuromotor performance, but decorin had no effect.

CONCLUSION

Two drugs that block TGFβ by different mechanisms do not reduce ventricular dilatation in this model. Together with our previous work on losartan and pirfenidone, we conclude that blocking TGFβ alone does not prevent the development of PHVD.

The expression of twisted gastrulation in postnatal mouse brain and functional implications

Twisted gastrulation (TWSG1), an extracellular regulator of bone morphogenetic protein (BMP) signaling, is critical for embryonic brain development. Mice deficient in TWSG1 have abnormal forebrain development manifesting as holoprosencephaly. The expression and potential roles of TWSG1 in postnatal brain development are less well understood. We show that Twsg1 is expressed in the adult mouse brain in the choroid plexus (CP), hippocampus, and other regions, with the strongest expression observed in CP. TWSG1 was also detected in a human fetal brain at mid-gestation, with highest levels in the epithelium of CP. Bmp1, Bmp2, Bmp4-Bmp7 as well as BmprIA and BmprII, but not BmprIB, were expressed in CP. BMP antagonists Chordin (Chrd) and Noggin were not detected in CP, however Chrd-like 1 and brain-specific Chrd-like (Brorin) were expressed. Electrophysiological study of synaptic plasticity revealed normal paired-pulse facilitation and long-term potentiation in the CA1 region of hippocampus in Twsg1(-/-) mice. Among the homozygous mutants that survive beyond the first 2 weeks, the prevalence of hydrocephalus was 4.3%, compared to 1.5% in a wild type colony (P=0.0133) between 3 and 10 weeks of life. We detected a high level of BMP signaling in CP in wild type adult mice that was 17-fold higher than in the hippocampus (P=0.005). In contrast, transforming growth factor beta (TGFbeta) signaling was predominant in the hippocampus. Both BMP signaling and the expression of BMP downstream targets Msx1 and Msx2 were reduced in CP in Twsg1(-/-) mice. In summary, we show that Twsg1 is expressed in the adult mouse and human fetal CP. We also show that BMP is a branch of TGFbeta superfamily that is dominant in CP. This presents an interesting avenue for future research in light of the novel roles of CP in neural progenitor differentiation and neuronal repair, especially since TWSG1 appears to be the main regulator of BMP present in CP.

Sporadic obstructive hydrocephalus in Aqp4 null mice

Aquaporin-4 (Aqp4) is a water transport protein expressed in glia and ependymocytes in brain. We report here the unexpected occurrence of severe obstructive hydrocephalus in a random subset of Aqp4 knockout mice. Of 612 Aqp4 knockout mice produced by heterozygote-heterozygote or knockout-knockout breedings, 9.6% of offspring manifested progressive encephalomegaly. Encephalomegaly was never seen in wild-type or Aqp4 heterozygous mice. Examination of the subset encephalomegalic mice revealed marked triventricular hydrocephalus (lateral ventricle size approximately 500 mm(3)), elevated intracranial pressure (19 +/- 3 vs. 6.1 +/- 0.6 mm Hg), and death by age 6 weeks, with a median survival of 28 days. Intraventricular dye injection studies revealed total obstruction of the cerebral aqueduct. Evans blue extravasation studies indicated an intact blood-brain barrier in the hydrocephalic mice. Brain histology revealed reduced ventricular size and ependymocyte disorganization in some nonhydrocephalic Aqp4 null mice. Our studies establish Aqp4 deletion as a predisposing factor for the development of congenital obstructive hydrocephalus in mice. We suggest that AQP4 polymorphisms might also contribute to the development of aqueduct stenosis in humans.

Aquaporin 4 correlates with apparent diffusion coefficient and hydrocephalus severity in the rat brain: a combined MRI-histological study

Hydrocephalus features include ventricular dilatation and periventricular edema due to transependymal resorption of cerebrospinal fluid (CSF). Aquaporin 4 (AQP4), a water channel protein located at the blood-brain barrier, might facilitate the removal of this excess of water from the parenchyma into the blood. First, we hypothesized a link between AQP4 expression and the severity of hydrocephalus. We further hypothesized that movements of water through AQP4 could affect apparent diffusion coefficient (ADC) measurements. Communicating inflammatory hydrocephalus was induced in 45 rats, and at various stages, magnetic resonance imaging (MRI) was used to measure CSF volume and periventricular ADC, with immunostaining being used to determine periventricular AQP4. We found an up-regulation of periventricular AQP4 in hydrocephalic rats that was strongly correlated with both CSF volume (Pearson=0.87, p<0.00001) and periventricular ADC (Pearson=0.85, p<0.00001). AQP4 were first located on astrocyte endfeet, but later on the whole membrane of astrocytes that became hypertrophic in the most severe and chronic hydrocephalic rats. These results show that AQP4 expression follows an adaptative profile to the severity of hydrocephalus, which is probably a protective response mechanism. They also suggest that ADC, on top of informing about cell sizes and interstitial bulk water, might also indirectly reflect quantitative water channel expression.

Association between cytokines and cerebral MRI changes in the aging brain

The association between cytokines (IL-1 beta, sIL-4R, IL-6, IL-8, IL-10, IL-12, TNF-alpha) and subcortical white matter lesions, cortical atrophy and lacunar infarctions of the aging brain was investigated among 268 elderly community participants. Single pro- and anti-inflammatory cytokines were neither associated with WML nor with atrophy and lacunar infarction. An association between atrophy and the chemokine-cytokine factor (containing sIL-4R, IL-6, IL-8) remained significant after adjustment for age, gender, education, depressive symptoms, diabetes mellitus, cardiovascular diseases (stroke, TIA, myocardial infarction, myocardial insufficiency, arrhythmic heart), hypertension, body-mass index, smoking status and aggregation inhibitors as opposed to single cytokines. Atrophy of the parietal, temporal and occipital lobes was associated with the same cytokine-chemokine factor for both the whole sample or restricted to those without history of stroke/TIA. The results indicate that a combination of chemokine-cytokines rather than single cytokines may contribute to inflammatory processes associated with cortical atrophy in the aging brain.

Priorities for hydrocephalus research: report from a National Institutes of Health-sponsored workshop

OBJECT

Treatment for hydrocephalus has not advanced appreciably since the advent of cerebrospinal fluid (CSF) shunts more than 50 years ago. Many questions remain that clinical and basic research could address, which in turn could improve therapeutic options. To clarify the main issues facing hydrocephalus research and to identify critical advances necessary to improve outcomes for patients with hydrocephalus, the National Institutes of Health (NIH) sponsored a workshop titled "Hydrocephalus: Myths, New Facts, and Clear Directions." The purpose of this paper is to report on the recommendations that resulted from that workshop.

METHODS

The workshop convened from September 29 to October 1, 2005, in Bethesda, Maryland. Among the 150 attendees was an international group of participants, including experts in pediatric and adult hydrocephalus as well as scientists working in related fields, neurosurgeons, laboratory-based neuroscientists, neurologists, patient advocates, individuals with hydrocephalus, parents, and NIH program and intramural staff. Plenary and breakout sessions covered injury and recovery mechanisms, modeling, biomechanics, diagnosis, current treatment and outcomes, complications, quality of life, future treatments, medical devices, development of research networks and information sharing, and education and career development.

RESULTS

The conclusions were as follows: 1) current methods of diagnosis, treatment, and outcomes monitoring need improvement; 2) frequent complications, poor rate of shunt survival, and poor quality of life for patients lead to unsatisfactory outcomes; 3) investigators and caregivers need additional methods to monitor neurocognitive function and control of CSF variables such as pressure, flow, or pulsatility; 4) research warrants novel interdisciplinary approaches; 5) understanding of the pathophysiological and recovery mechanisms of neuronal function in hydrocephalus is poor, warranting further investigation; and 6) both basic and clinical aspects warrant expanded and innovative training programs.

CONCLUSIONS

The research priorities of this workshop provide critical guidance for future research in hydrocephalus, which should result in advances in knowledge, and ultimately in the treatment for this important disorder and improved outcomes in patients of all ages.

Do drugs that block transforming growth factor beta reduce posthaemorrhagic ventricular dilatation in a neonatal rat model?

AIM

Posthaemorrhagic ventricular dilatation (PHVD) after intraventricular haemorrhage (IVH) remains a significant problem in preterm infants. No treatment has reduced the need for cerebrospinal fluid (CSF) diversion. Considerable evidence implicates transforming growth factor-beta (TGF-beta) in the pathogenesis of PHVD. Pirfenidone and losartan reduce TGF-beta expression and decrease postinflammatory fibrosis in the lungs, kidneys, heart and liver. They have excellent CSF and brain penetration. We hypothesized that administration of pirfenidone or losartan would reduce ventricular dilatation.

METHODS

Ninety-two rat pups underwent intraventricular blood injection on postnatal days (PN) 7 and 8, and were randomised to pirfenidone, losartan or water by gavage for 14 days. Neuromotor testing was carried out twice weekly. After sacrifice at PN21, ventricular area was measured on coronal sections using image-analysis software.

RESULTS

Ninety-five percent of animals undergoing IVH developed PHVD. Ventricular size was not significantly different between animals receiving either drug or water. Neuromotor testing at PN14 was significantly worse in IVH animals than in controls; neither drug improved performance in IVH animals.

CONCLUSION

Drugs that block TGF-beta do not reduce ventricular dilatation in this model. Further study is required to identify other cytokine targets and to determine how PHVD differs from postinflammatory fibrosis in other organs.

Brain metabolism in adult chronic hydrocephalus

Normal pressure hydrocephalus (NPH) is the most frequent form of chronic hydrocephalus in adults. NPH remains underdiagnosed although between 5% and 10% of all demented patients may suffer from this disorder. As dementia is an increasing demographic problem, treatable forms such as in NPH have become a central issue in neurology. Despite the traditional perception of hydrocephalus being a disorder of disturbed CSF dynamics, in NPH metabolic impairment seems at least as important. So far, the only valid animal model of NPH is chronic adult kaolin hydrocephalus. In this model, opening of alternative CSF outflow pathways leads to normal or near-normal intracranial pressure and CSF outflow resistance. Yet, various metabolic disturbances cause ongoing ventricular enlargement and characteristic symptoms including cognitive decline and gait ataxia. Delayed hippocampal neuronal death, accumulation of beta-amyloid and disturbed cholinergic neurotransmission may contribute to memory dysfunction. Compromised periventricular blood flow, decreased dopamine levels in the substantia nigra and damaged striatal GABAergic interneurons may reflect basal ganglia symptoms. At least in human hydrocephalus cerebrovascular co-morbidity of the white matter plays an important role as well. It seems that in hydrocephalus from a certain 'point of no return' metabolic impairment becomes decoupled from CSF dynamics and, at least partly, self-sustained. This is probably the reason why despite restored CSF circulation by shunting many patients with chronic hydrocephalus still suffer from severe neurological deficits. The present paper offers a comprehensive review of the experimental and clinical data suggesting metabolic disturbances in chronic hydrocephalus.

Loss of Fyn tyrosine kinase on the C57BL/6 genetic background causes hydrocephalus with defects in oligodendrocyte development

The supportive functions of oligodendrocytes are required for the survival and development of axons, ensuring the organization of highly specialized neuronal networks in brain. Although the molecules that regulate oligodendrocyte differentiation in vitro have been identified, their roles in vivo are largely uncertain. Here we report that fyn deficiency on the C57BL/6 genetic background resulted in premature death, showing severe hydrocephalus with neonatal onset. One week after birth, fyn-deficient mice showed enlarged lateral ventricles with thinner cerebral cortices and degenerating axons in the corpus callosum. In addition, before the onset of myelination, the number of oligodendrocytes was reduced and their morphogenesis was impaired in the cerebral cortex. These results demonstrate that Fyn is essential for normal brain development and suggest that defects in oligodendrocyte development cause degeneration of cortical axons and subsequent hydrocephalus in fyn-deficient mice.

Nuclear factor I X deficiency causes brain malformation and severe skeletal defects

The transcription factor family of nuclear factor I (NFI) proteins is encoded by four closely related genes: Nfia, Nfib, Nfic, and Nfix. A potential role for NFI proteins in regulating developmental processes has been implicated by their specific expression pattern during embryonic development and by analysis of NFI-deficient mice. It was shown that loss of NFIA results in hydrocephalus and agenesis of the corpus callosum and that NFIB deficiency leads to neurological defects and to severe lung hypoplasia, whereas Nfic knockout mice exhibit specific tooth defects. Here we report the knockout analysis of the fourth and last member of this gene family, Nfix. Loss of NFIX is postnatally lethal and leads to hydrocephalus and to a partial agenesis of the corpus callosum. Furthermore, NFIX-deficient mice develop a deformation of the spine, which is due to a delay in ossification of vertebral bodies and a progressive degeneration of intervertebral disks. Impaired endochondral ossification and decreased mineralization were also observed in femoral sections of Nfix-/- mice. Consistent with the defects in bone ossification we could show that the expression level of tetranectin, a plasminogen-binding protein involved in mineralization, is specifically downregulated in bones of NFIX-deficient mice.

Loss of cell adhesion causes hydrocephalus in nonmuscle myosin II-B-ablated and mutated mice

Ablation of nonmuscle myosin (NM) II-B in mice during embryonic development leads to marked enlargement of the cerebral ventricles and destruction of brain tissue, due to hydrocephalus. We have identified a transient mesh-like structure present at the apical border of cells lining the spinal canal of mice during development. This structure, which only contains the II-B isoform of NM, also contains beta-catenin and N-cadherin, consistent with a role in cell adhesion. Ablation of NM II-B or replacement of NM II-B with decreased amounts of a mutant (R709C), motor-impaired NM II-B in mice results in collapse of the mesh-like structure and loss of cell adhesion. This permits the underlying neuroepithelial cells to invade the spinal canal and obstruct cerebral spinal fluid flow. These defects in the CNS of NM II-B-ablated mice seem to be the cause of hydrocephalus. Interestingly, the mesh-like structure and patency of the spinal canal can be restored by increasing expression of the motor-impaired NM II-B, which also rescues hydrocephalus. However, the mutant isoform cannot completely rescue neuronal cell migration. These studies show that the scaffolding properties of NM II-B play an important role in cell adhesion, thereby preventing hydrocephalus during mouse brain development.

Evaluation of the lumbar and ventricular infusion test in the diagnostic strategy of pediatric hydrocephalus and the therapeutic implications

AIM

To evaluate the infusion test as a diagnostic tool behind the choice of intervention in pediatric hydrocephalus.

MATERIALS AND METHODS

Intracranial pressure (ICP) measurement and infusion test were performed intraventricularly, by lumbar route, or combined in 40 consecutive children as a part of the standard diagnostic program in 1996-1999.

RESULTS

The median age was 18.5 months, ranging from 2 weeks to 13 years. In the subgroup of patients with radiological aqueductal stenosis (N=14), mean lumbar/intraventricular ICP was 13 (3-35)/10 (2-27). Mean lumbar/ventricular R(out) were 18 (4-49)/17 (6-37). For patients with radiological communication between the third and fourth ventricles (N=14), the mean lumbar/intraventricular ICP was 11 (7-17)/9 (1-16). Mean lumbar/ventricular R(out) were 8 (3-11)/8 (4-12). A total of 13 patients had a shunt insertion, 10 had an endoscopic third ventriculostomy (ETV), 5 had endoscopic fenestration of a cyst, and 12 had no surgery. Of the patients initially treated with EVT, 50% had a shunt insertion shortly after. For communicating hydrocephalus, 75% of the patients initially not operated based on normal R(out) values ended up having a shunt insertion.

DISCUSSION

R(out) has doubtful value as an indicator for conducting an operation or not and in the choice between EVT and shunt in children. This should be interpreted in the light of a growing understanding of hydrocephalus on a molecular level.

Diazepam binding inhibitor overexpression in mice causes hydrocephalus, decreases plasticity in excitatory synapses and impairs hippocampus-dependent learning

Diazepam binding inhibitor (DBI) and its processing products are endogenous modulators of GABAA and linked to various brain disorders ranging from anxiety and drug dependence to epilepsy. To investigate the physiological role of endogenously expressed DBI in the brain we created a transgenic mouse line overexpressing DBI gene. Transgenic mice had a 37x increased protein expression and immunohistochemistry showed excessive glial expression in the infragranular region of the dentate gyrus. Transgenic animals had significantly larger lateral ventricles and decreased plasticity of excitatory synapses without affecting either inhibitory or excitatory synaptic transmission. In behavioral tests transgenic animals had no differences in motor and exploratory activity, yet impaired hippocampus-dependent learning and memory. Overexpression did not cause anxiety or proconflict behavior, nor influenced kainic acid or pentylenetetrazole induced seizure activity. Our transgenic mouse line demonstrates that endogenously overexpressed DBI impairs hippocampus-dependent learning without anxiety or proconflict behavior.

Accelerated progression of kaolin-induced hydrocephalus in aquaporin-4-deficient mice

Hydrocephalus is caused by an imbalance in cerebrospinal fluid (CSF) production and absorption, resulting in excess ventricular fluid accumulation and neurologic impairment. Current therapy for hydrocephalus involves surgical diversion of excess ventricular fluid. The water-transporting protein aquaporin-4 (AQP4) is expressed at the brain-CSF and blood-brain barriers. Here, we provide evidence for AQP4-facilitated CSF absorption in hydrocephalus by a transparenchymal pathway into the cerebral vasculature. A mouse model of obstructive hydrocephalus was created by injecting kaolin (2.5 mg/mouse) into the cisterna magna. Intracranial pressure (ICP) was approximately 5 mm Hg and ventricular size <0.3 mm(3) in control mice. Lateral ventricle volume increased to 3.7+/-0.5 and 5.1+/-0.5 mm(3) in AQP4 null mice at 3 and 5 days after injection, respectively, significantly greater than 2.6+/-0.3 and 3.5+/-0.5 mm(3) in wildtype mice (P<0.005). The corresponding ICP was 22+/-2 mm Hg at 3 days in AQP4 null mice, significantly greater than 14+/-1 mm Hg in wildtype mice (P<0.005). Brain parenchymal water content increased by 2% to 3% by 3 days, corresponding to approximately 50 muL of fluid, indicating backflow of CSF from the ventricle into the parenchymal extracellular space. A multi-compartment model of hydrocephalus based on experimental data from wildtype mice accurately reproduced the greater severity of hydrocephalus in AQP4 null mice, and predicted a much reduced severity if AQP4 expression/function were increased. Our results indicate a significant role for AQP4-mediated transparenchymal CSF absorption in hydrocephalus and provide a rational basis for evaluation of AQP4 induction as a nonsurgical therapy for hydrocephalus.

High levels of Cre expression in neuronal progenitors cause defects in brain development leading to microencephaly and hydrocephaly

Hydrocephalus is a common and variegated pathology often emerging in newborn children after genotoxic insults during pregnancy (Hicks and D'Amato, 1980). Cre recombinase is known to have possible toxic effects that can compromise normal cell cycle and survival. Here we show, by using three independent nestin Cre transgenic lines, that high levels of Cre recombinase expression into the nucleus of neuronal progenitors can compromise normal brain development. The transgenics analyzed are the nestin Cre Balancer (Bal1) line, expressing the Cre recombinase with a nuclear localization signal, and two nestin CreER(T2) (Cre recombinase fused with a truncated estrogen receptor) mice lines with different levels of expression of a hybrid CreER(T2) recombinase that translocates into the nucleus after tamoxifen treatment. All homozygous Bal1 nestin Cre embryos displayed reduced neuronal proliferation, increased aneuploidy and cell death, as well as defects in ependymal lining and lamination of the cortex, leading to microencephaly and to a form of communicating hydrocephalus. An essentially overlapping phenotype was observed in the two nestin CreER(T2) transgenic lines after tamoxifen mediated-CreER(T2) translocation into the nucleus. Neither tamoxifen-treated wild-type nor nestin CreER(T2) oil-treated control mice displayed these defects. These results indicate that some forms of hydrocephalus may derive from a defect in neuronal precursors proliferation. Furthermore, they underscore the potential risks for developmental studies of high levels of nuclear Cre in neurogenic cells.

Genetics of human hydrocephalus

Human hydrocephalus is a common medical condition that is characterized by abnormalities in the flow or resorption of cerebrospinal fluid (CSF), resulting in ventricular dilatation. Human hydrocephalus can be classified into two clinical forms, congenital and acquired. Hydrocephalus is one of the complex and multifactorial neurological disorders.

A growing body of evidence indicates that genetic factors play a major role in the pathogenesis of hydrocephalus. An understanding of the genetic components and mechanism of this complex disorder may offer us significant insights into the molecular etiology of impaired brain development and an accumulation of the cerebrospinal fluid in cerebral compartments during the pathogenesis of hydrocephalus. Genetic studies in animal models have started to open the way for understanding the underlying pathology of hydrocephalus. At least 43 mutants/loci linked to hereditary hydrocephalus have been identified in animal models and humans. Up to date, 9 genes associated with hydrocephalus have been identified in animal models. In contrast, only one such gene has been identified in humans. Most of known hydrocephalus gene products are the important cytokines, growth factors or related molecules in the cellular signal pathways during early brain development. The current molecular genetic evidence from animal models indicate that in the early development stage, impaired and abnormal brain development caused by abnormal cellular signaling and functioning, all these cellular and developmental events would eventually lead to the congenital hydrocephalus.

Owing to our very primitive knowledge of the genetics and molecular pathogenesis of human hydrocephalus, it is difficult to evaluate whether data gained from animal models can be extrapolated to humans. Initiation of a large population genetics study in humans will certainly provide invaluable information about the molecular and cellular etiology and the developmental mechanisms of human hydrocephalus.

This review summarizes the recent findings on this issue among human and animal models, especially with reference to the molecular genetics, pathological, physiological and cellular studies, and identifies future research directions.