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

<p>Abstract</p> <p>Background</p> <p>Reactive astrocytosis and microgliosis are important features of the pathophysiology of hydrocephalus, and persistent glial "scars" that form could exacerbate neuroinflammation, impair cerebral perfusion, impede neuronal regeneration, and alter biomechanical properties. The purpose of this study was to determine the efficacy of minocycline, an antibiotic known for its anti-inflammatory properties, to reduce gliosis in the H-Tx rat model of congenital hydrocephalus.</p> <p>Methods</p> <p>Minocycline (45 mg/kg/day i.p. in 5% sucrose at a concentration of 5-10 mg/ml) was administered to hydrocephalic H-Tx rats from postnatal day 15 to day 21, when ventriculomegaly had reached moderate to severe stages. Treated animals were compared to age-matched non-hydrocephalic and untreated hydrocephalic littermates. The cerebral cortex (both gray matter laminae and white matter) was processed for immunohistochemistry (glial fibrillary acidic protein, GFAP, for astrocytes and ionized calcium binding adaptor molecule, Iba-1, for microglia) and analyzed by qualitative and quantitative light microscopy.</p> <p>Results</p> <p>The mean number of GFAP-immunoreactive astrocytes was significantly higher in untreated hydrocephalic animals compared to both types of controls (<it>p </it>< 0.001). Minocycline treatment of hydrocephalic animals reduced the number of GFAP immunoreactive cells significantly (<it>p </it>< 0.001). Likewise, the mean number of Iba-1 immunoreactive microglia was significantly higher in untreated hydrocephalic animals compared to both types of controls (<it>p </it>< 0.001). Furthermore, no differences in the numbers of GFAP-positive astrocytes or Iba-1-positive microglia were noted between control animals receiving no minocycline and control animals receiving minocycline, suggesting that minocycline does not produce an effect under non-injury conditions. Additionally, in six out of nine regions sampled, hydrocephalic animals that received minocycline injections had significantly thicker cortices when compared to their untreated hydrocephalic littermates.</p> <p>Conclusions</p> <p>Overall, these data suggest that minocycline treatment is effective in reducing the gliosis that accompanies hydrocephalus, and thus may provide an added benefit when used as a supplement to ventricular shunting.</p

Effect of hydrocephalus on rat brain extracellular compartment

<p>Abstract</p> <p>Background</p> <p>The cerebral cortex may be compressed in hydrocephalus and some experiments suggest that movement of extracellular substances through the cortex is impaired. We hypothesized that the extracellular compartment is reduced in size and that the composition of the extracellular compartment changes in rat brains with kaolin-induced hydrocephalus.</p> <p>Methods</p> <p>We studied neonatal (newborn) onset hydrocephalus for 1 or 3 weeks, juvenile (3 weeks) onset hydrocephalus for 3–4 weeks or 9 months, and young adult (10 weeks) onset hydrocephalus for 2 weeks, after kaolin injection. Freeze substitution electron microscopy was used to measure the size of the extracellular compartment. Western blotting and immunohistochemistry with quantitative image densitometry was used to study the extracellular matrix constituents, phosphacan, neurocan, NG2, decorin, biglycan, and laminin.</p> <p>Results</p> <p>The extracellular space in cortical layer 1 was reduced significantly from 16.5 to 9.6% in adult rats with 2 weeks duration hydrocephalus. Western blot and immunohistochemistry showed that neurocan increased only in the periventricular white matter following neonatal induction and 3 weeks duration hydrocephalus. The same rats showed mild decorin increases in white matter and around cortical neurons. Juvenile and adult onset hydrocephalus was associated with no significant changes.</p> <p>Conclusion</p> <p>We conclude that compositional changes in the extracellular compartment are negligible in cerebral cortex of hydrocephalic rats at various ages. Therefore, the functional change related to extracellular fluid flow should be reversible.</p

Low levels of amyloid-beta and its transporters in neonatal rats with and without hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Previous studies in aging animals have shown that amyloid-beta protein (Aβ) accumulates and its transporters, low-density lipoprotein receptor-related protein-1 (LRP-1) and the receptor for advanced glycation end products (RAGE) are impaired during hydrocephalus. Furthermore, correlations between astrocytes and Aβ have been found in human cases of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD). Because hydrocephalus occurs frequently in children, we evaluated the expression of Aβ and its transporters and reactive astrocytosis in animals with neonatal hydrocephalus.</p> <p>Methods</p> <p>Hydrocephalus was induced in neonatal rats by intracisternal kaolin injections on post-natal day one, and severe ventriculomegaly developed over a three week period. MRI was performed on post-kaolin days 10 and 21 to document ventriculomegaly. Animals were sacrificed on post-kaolin day 21. For an age-related comparison, tissue was used from previous studies when hydrocephalus was induced in a group of adult animals at either 6 months or 12 months of age. Tissue was processed for immunohistochemistry to visualize LRP-1, RAGE, Aβ, and glial fibrillary acidic protein (GFAP) and with quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify expression of LRP-1, RAGE, and GFAP.</p> <p>Results</p> <p>When 21-day post-kaolin neonatal hydrocephalic animals were compared to adult (6–12 month old) hydrocephalic animals, immunohistochemistry demonstrated levels of Aβ, RAGE, and LRP-1 that were substantially lower in the younger animals; in contrast, GFAP levels were elevated in both young and old hydrocephalic animals. When the neonatal hydrocephalic animals were compared to age-matched controls, qRT-PCR demonstrated no significant changes in Aβ, LRP-1 and RAGE. However, immunohistochemistry showed very small increases or decreases in individual proteins. Furthermore, qRT-PCR indicated statistically significant increases in GFAP.</p> <p>Conclusion</p> <p>Neonatal rats with and without hydrocephalus had low expression of Aβ and its transporters when compared to adult rats with hydrocephalus. No statistical differences were observed in Aβ and its transporters between the control and hydrocephalic neonatal animals.</p

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

<p>Abstract</p> <p>Background</p> <p>Hydrocephalus is associated with enlargement of cerebral ventricles. We hypothesized that magnetic resonance (MR) imaging parameters known to be influenced by tissue water content would change in parallel with ventricle size in young rats and that changes in blood-brain barrier (BBB) permeability would be detected.</p> <p>Methods</p> <p>Hydrocephalus was induced by injection of kaolin into the cisterna magna of 4-week-old rats, which were studied 1 or 3 weeks later. MR was used to measure longitudinal and transverse relaxation times (T1 and T2) and apparent diffusion coefficients in several regions. Brain tissue water content was measured by the wet-dry weight method, and tissue density was measured in Percoll gradient columns. BBB permeability was measured by quantitative imaging of changes on T1-weighted images following injection of gadolinium diethylenetriamine penta-acetate (Gd-DTPA) tracer and microscopically by detection of fluorescent dextran conjugates.</p> <p>Results</p> <p>In nonhydrocephalic rats, water content decreased progressively from age 3 to 7 weeks. T1 and T2 and apparent diffusion coefficients did not exhibit parallel changes and there was no evidence of BBB permeability to tracers. The cerebral ventricles enlarged progressively in the weeks following kaolin injection. In hydrocephalic rats, the dorsal cortex was more dense and the white matter less so, indicating that the increased water content was largely confined to white matter. Hydrocephalus was associated with transient elevation of T1 in gray and white matter and persistent elevation of T2 in white matter. Changes in the apparent diffusion coefficients were significant only in white matter. Ventricle size correlated significantly with dorsal water content, T1, T2, and apparent diffusion coefficients. MR imaging showed evidence of Gd-DTPA leakage in periventricular tissue foci but not diffusely. These correlated with microscopic leak of larger dextran tracers.</p> <p>Conclusions</p> <p>MR characteristics cannot be used as direct surrogates for water content in the immature rat model of hydrocephalus, probably because they are also influenced by other changes in tissue composition that occur during brain maturation. There is no evidence for widespread persistent opening of BBB as a consequence of hydrocephalus in young rats. However, increase in focal BBB permeability suggests that periventricular blood vessels may be disrupted.</p

Morphological and Behavioral Changes in the Pathogenesis of a Novel Mouse Model of Communicating Hydrocephalus

The Ro1 model of hydrocephalus represents an excellent model for studying the pathogenesis of hydrocephalus due to its complete penetrance and inducibility, enabling the investigation of the earliest cellular and histological changes in hydrocephalus prior to overt pathology. Hematoxylin and eosin staining, immunofluorescence and electron microscopy were used to characterize the histopathological events of hydrocephalus in this model. Additionally, a broad battery of behavioral tests was used to investigate behavioral changes in the Ro1 model of hydrocephalus. The earliest histological changes observed in this model were ventriculomegaly and disorganization of the ependymal lining of the aqueduct of Sylvius, which occurred concomitantly. Ventriculomegaly led to thinning of the ependyma, which was associated with periventricular edema and areas of the ventricular wall void of cilia and microvilli. Ependymal denudation was subsequent to severe ventriculomegaly, suggesting that it is an effect, rather than a cause, of hydrocephalus in the Ro1 model. Additionally, there was no closure of the aqueduct of Sylvius or any blockages within the ventricular system, even with severe ventriculomegaly, suggesting that the Ro1 model represents a model of communicating hydrocephalus. Interestingly, even with severe ventriculomegaly, there were no behavioral changes, suggesting that the brain is able to compensate for the structural changes that occur in the pathogenesis of hydrocephalus if the disorder progresses at a sufficiently slow rate

Neurologic effects of exogenous saccharides: A review of controlled human, animal, and in vitro studies

Objectives: Current research efforts are centered on delineating the novel health benefits of naturally derived saccharides, including growing interest in their abilities to influence neurologic health. We performed a comprehensive review of the literature to consolidate all controlled studies assessing various roles of exogenous saccharide compounds and polysaccharide-rich extracts from plants, fungi, and other natural sources on brain function, with a significant focus on benefits derived from oral intake. Methods: Studies were identified by conducting electronic searches on PubMed and Google Scholar. Reference lists of articles were also reviewed for additional relevant studies. Only articles published in English were included in this review. Results: Six randomized, double-blind, placebo-controlled clinical studies were identified in which consumption of a blend of plant-derived polysaccharides showed positive effects on cognitive function and mood in healthy adults. A separate controlled clinical study observed improvements in well-being with ingestion of a yeast beta-glucan. Numerous animal and in vitro studies have demonstrated the ability of individual saccharide compounds and polysaccharide-rich extracts to modify behavior, enhance synaptic plasticity, and provide neuroprotective effects. Discussion: Although the mechanisms by which exogenous saccharides can influence brain function are not well understood at this time, the literature suggests that certain naturally occurring compounds and polysaccharide-rich extracts show promise, when taken orally, in supporting neurologic health and function. Additional well-controlled clinical studies on larger populations are necessary, however, before specific recommendations can be made

Hydrocephalus induces dynamic spatiotemporal regulation of aquaporin-4 expression in the rat brain

<p>Abstract</p> <p>Background</p> <p>The water channel protein aquaporin-4 (AQP4) is reported to be of possible major importance for accessory cerebrospinal fluid (CSF) circulation pathways. We hypothesized that changes in AQP4 expression in specific brain regions correspond to the severity and duration of hydrocephalus.</p> <p>Methods</p> <p>Hydrocephalus was induced in adult rats (~8 weeks) by intracisternal kaolin injection and evaluated after two days, one week and two weeks. Using magnetic resonance imaging (MRI) we quantified lateral ventricular volume, water diffusion and blood-brain barrier properties in hydrocephalic and control animals. The brains were analysed for AQP4 density by western blotting and localisation by immunohistochemistry. Double fluorescence labelling was used to study cell specific origin of AQP4.</p> <p>Results</p> <p>Lateral ventricular volume was significantly increased over control at all time points after induction and the periventricular apparent diffusion coefficient (ADC) value significantly increased after one and two weeks of hydrocephalus. Relative AQP4 density was significantly decreased in both cortex and periventricular region after two days and normalized after one week. After two weeks, periventricular AQP4 expression was significantly increased. Relative periventricular AQP4 density was significantly correlated to lateral ventricular volume. AQP4 immunohistochemical analysis demonstrated the morphological expression pattern of AQP4 in hydrocephalus in astrocytes and ventricular ependyma. AQP4 co-localized with astrocytic glial fibrillary acidic protein (GFAP) in glia limitans. In vascular structures, AQP4 co-localized to astroglia but not to microglia or endothelial cells.</p> <p>Conclusions</p> <p>AQP4 levels are significantly altered in a time and region dependent manner in kaolin-induced hydrocephalus. The presented data suggest that AQP4 could play an important neurodefensive role, and may be a promising future pharmaceutical target in hydrocephalus and CSF disorders.</p