Hydrocephalic Rat Brain Research Articles

Inhibition of Wnt/β-catenin signal is alleviated reactive gliosis in rats with hydrocephalus.

Reactive gliosis has been implicated in the pathogenesis of communicating hydrocephalus. Because the activation of Wnt/β-catenin signaling pathway is considered as a significant factor to contribute to brain development, neurodegenerative process, and reactive gliosis, we target this pathway for intervention by using sFRP-l and investigated the expression of β-catenin, cyclin D-1, and glial fibrillary acidic protein (GFAP) in the brain of experimental hydrocephalic rats in terms of protein and gene expression. Therefore, 30 adult SD rats were randomly divided into the normal group (n = 5), the sham operation group (n = 5), the hydrocephalus group (n = 10), and the sFRP-l group (n = 10). Hydrocephalic rat models were induced by intraventricular injections of 3% kaolin while sFRP-l group was treated by sFRP-l with kaolin injections. The ventricular dilatation was examinated by MRI at 2-week post-operation. After that, β-catenin, cyclin D-1, and GFAP were qualified by Western blot and immunohistochemistry. According to the result, the expression of β-catenin and cyclin D-1 increased (P < 0. 05) in the brain tissue of the hydrocephalus group compared with that of the sham group, while GFAP expression in the hydrocephalus group is more obvious (P < 0. 05). In the sFRP-l group, the expression of β-catenin and cyclin D-1 and GFAP expression is lower (P < 0. 05) compared with those of the hydrocephalus group. We demonstrated that the Wnt/β-catenin pathway is activated in the experimental hydrocephalic rat brain. sFRP-l inhibited the expression of β-catenin and cyclin D-1 and alleviated reactive gliosis in the hydrocephalic rat brain tissue, while the development of hydrocephalus was delayed. These results suggest that regulating Wnt/β-catenin signaling pathway may provide new therapeutic methods for hydrocephalic patients.

Differences in distribution and regulation of astrocytic aquaporin‐4 in human and rat hydrocephalic brain

Aquaporin-4 (AQP4) is the most abundant cellular water channel in brain and could be a molecular basis for a cerebrospinal fluid absorption route additional to the arachnoid villi. In the search for 'alternative' cerebrospinal fluid absorption pathways it is important to compare experimental findings with human pathophysiology. This study compares expression of AQP4 in hydrocephalic human brain with human controls and hydrocephalic rat brain. Cortical biopsies from patients with chronic hydrocephalus (n = 29) were sampled secondary to planned surgical intervention. AQP4 in human hydrocephalic cortex relative to controls was quantified by Western blotting (n = 28). A second biopsy (n = 13) was processed for immunohistochemistry [glial fibrillary acidic protein (GFAP), CD68, CD34 and AQP4] and double immunofluorescence (AQP4 + GFAP and AQP4 + CD34). Brain tissue from human controls and kaolin-induced hydrocephalic rats was processed in parallel. Immunohistochemistry and immunofluorescence were assessed qualitatively. Western blotting showed that AQP4 abundance was significantly increased (P < 0.05) in hydrocephalic human brain compared with controls. AQP4 immunoreactivity was present in both white and grey matter. In human brain (hydrocephalic and controls) AQP4 immunoreactivity was found on the entire astrocyte membrane, unlike hydrocephalic rat brain where pronounced endfeet polarization was present. Endothelial AQP4 immunoreactivity was not observed. This study shows a significant increase in astrocytic AQP4 in human hydrocephalic cortex compared with control. Cell type specific expression in astrocytes is conserved between rat and human, although differences of expression in specific membrane domains are seen. This study addresses direct translational aspects from rat to human, hereby emphasizing the relevance and use of models in hydrocephalus research.

O.067 Spatiotemporal regulation of aquaporin-4 in the kaolin induced hydrocephalic rat brain – Experimental study using in vivo MRI and immunological methods

O.067 Spatiotemporal regulation of aquaporin-4 in the kaolin induced hydrocephalic rat brain – Experimental study using in vivo MRI and immunological methods

Fragmentation of Protein Kinase N (PKN) in the Hydrocephalic Rat Brain

PKN (protein kinase N; also called protein kinase C-related kinase (PRK-1)), is a serine/threonine protein kinase that is ubiquitously expressed in several organs, including the brain. PKN has a molecular mass of 120 kDa and has two domains, a regulatory and a catalytic domain, in its amino-terminals and carboxyl-terminus, respectively. Although the role of PKN has not been fully elucidated, previous studies have revealed that PKN is cleaved to a constitutively active catalytic fragment of 55 kDa in response to apoptotic signals. Hydrocephalus is a pathological condition caused by insufficient cerebrospinal fluid (CSF) circulation and subsequent excess of CSF in the brain. In this study, in order to elucidate the role of PKN in the pathophysiology of hydrocephalus, we examined PKN fragmentation in hydrocephalic model rats.Hydrocephalus was induced in rats by injecting kaolin into the cisterna magna. Kaolin-induced rats (n=60) were divided into three groups according to the observation period after treatment (group 1: 3–6 weeks, group 2: 7–12 weeks, and group 3: 13–18 weeks). Sham-treated control rats, injected with sterile saline (n=20), were similarly divided into three groups. Spatial learning ability was estimated by a modified water maze test. Thereafter, brains were cut into slices and ventricular dilatation was estimated. Fragmentation of PKN was observed by Western blotting in samples collected from the parietal cortex, striatum, septal nucleus, hippocampus, and periaqueductal gray matter.All kaolin-induced rats showed ventricular dilatation. Most of them showed less spatial learning ability than those of sham-treated controls. In most regions, fragmentation of PKN had occurred in a biphasic manner more frequently than that in controls. The appearance of PKN fragmentation in periaqueductal gray matter was correlated with the extent of ventricular dilation and spatial learning disability. These results revealed that PKN fragmentation was observed in rats with kaolin-induced hydrocephalus, models for chronically-damaged brain dysfunction, suggesting that persistent brain insult, such as apoptosis, had occurred in these models. PKN fragmentation could be a hallmark for evaluating morphological and functional damage of the hydrocephalus.

Defective cell cycle control underlies abnormal cortical development in the hydrocephalic Texas rat.

There is a significant body of evidence to suggest a physiological role for the CSF in both the developing and adult brain. Our recent studies suggest a critical role for this fluid in the developing brain of the hydrocephalic Texas (H-Tx) rat. A key feature of the foetal-onset hydrocephalus in this rat is obstruction in the flow and/or absorption of fluid that is associated with abnormal development of the cerebral cortex resulting in a reduction in the number of neuronal precursors generated. Cells from the affected cerebral cortex do proliferate in vitro and show dose-dependent responses to growth factor stimulation, suggesting that germinal cells are under inhibitory influences in vivo. We tested the hypothesis that the CSF of the affected brains was responsible for the abnormal development. Cells analysed at the time of extraction from affected brains showed an accumulation of cells in the S-phase of the cell cycle, which was reflected in a concentration of cells containing high levels of DNA in the germinal matrix of histological sections of affected brains. CSF from the lateral ventricle of affected foetal brains not only inhibited in vitro proliferation of normal neuronal progenitors, but it also resulted in an accumulation of cells in the S-phase of the cell cycle mimicking the situation in vivo. Fluid from normal foetal brains did not have this effect. From the work detailed here on the mechanistic basis of the deficient cortical development in the foetal hydrocephalic rat brain, we conclude that the content of the CSF is critical in maintaining germinal matrix function and output and, therefore, that the CSF has a vital role in brain development.

Green tea polyphenol (-)-epigallocatechin gallate prevents oxidative damage on periventricular white matter of infantile rats with hydrocephalus.

Hydrocephalus causes damage to periventricular white matter at least in part through chronic ischemia. Emphasizing the periventricular ischemia/hypoxia in hydrocephalus, various authors indicated the secondary biochemical impairment and oxidative damage in experimentally induced and congenital hydrocephalic rat brain. (-)-Epigallocatechin gallate (EGCG), the main constituent of green tea polyphenols, has been shown to be of some protective value in various models of neurological injury as a free oxygen radical scavenger. In the present study the effects of EGCG were examined on the periventricular oxidative damage in experimental childhood-onset hydrocephalus. Hydrocephalus was induced in 3 weeks-old rat pups by kaolin injection into the cisterna magna. A single daily dose of 50 mg/kg of EGCG injected into the peritoneum of the rats for 15 days significantly reduced periventricular white matter malondialdehyde levels when compared to non-treated hydrocephalic animals. Our results indicate that EGCG may have a protective effect against periventricular white matter oxidative damage in hydrocephalus induced infantile rats.

Altered diffusion and perfusion in hydrocephalic rat brain: a magnetic resonance imaging analysis.

It can be inferred from data published in the literature that brain compression occurs in the early stages of acute hydrocephalus and that drainage of extracellular waste products is impaired. The authors hypothesized that compression of the cortex would alter water distribution and retard the diffusion of fluid in the hydrocephalic brain. Proton diffusion, blood perfusion, and T1 and T2 relaxation times were determined in adult rat brain by using magnetic resonance imaging prior to, and 1 and 8 days after induction of hydrocephalus by kaolin injection. Five anatomical regions of interest were studied. The striatum, dorsal cortex, and lateral cortex exhibited decreased T2 and apparent diffusion coefficient (ADC) values but no change in perfusion. Examination of white matter revealed an initial decrease in ADC followed by a significant increase. The T2 relaxation times increased and perfusion decreased progressively between 1 and 8 days after induction of hydrocephalus. Acute experimental hydrocephalus causes compression of gray matter, perhaps associated with reduction in total water, which impairs diffusion of water in the tissue. White matter compression and hypoperfusion precede the development of edema. These findings have importance for understanding the neurochemical changes that occur in hydrocephalic brains.

Altered diffusion and perfusion in hydrocephalic rat brain: a magnetic resonance imaging analysis

It can be inferred from data published in the literature that brain compression occurs in the early stages of acute hydrocephalus and that drainage of extracellular waste products is impaired. The authors hypothesized that compression of the cortical extracellular compartment will alter water distribution and retard the diffusion of fluid in the hydrocephalic brain. Using magnetic resonance imaging proton diffusion, blood perfusion, and T1 and T2 relaxation times were determined in adult rat brain prior to, and 1 and 8 days following induction of hydrocephalus by using kaolin injection. Five anatomical regions of interest were studied. The striatum, dorsal cortex, and lateral cortex were shown to exhibit decreased T2 and apparent diffusion coefficient (ADC) values but no change in perfusion. Examination of white matter demonstrated an initial decrease in ADC followed by a significant increase. The T2 relaxation times increased and perfusion decreased progressively from 1 to 8 days. Acute experimental hydrocephalus causes compression of gray matter, perhaps associated with reduction in total water, which impairs diffusion of protons in the tissue. White matter compression and hypoperfusion precede the development of edema. These findings have importance for understanding the neurochemical changes that occur in hydrocephalic brains.

Glucose metabolism and protective biochemical mechanisms in a rat brain affected by kaolin-induced hydrocephalus.

To clarify glucose metabolism in a hydrocephalic rat brain, substances related to glycolytic metabolism were biochemically measured. Kaolin-induced hydrocephalic rats were sacrificed and lactate dehydrogenase (LDH), LDH isozyme, lactate, adenosine triphosphate (ATP), and isocitrate dehydrogenase (ICDH) were measured in the following regions: cortex, thalamus, midbrain, hippocampus, cerebellum, and pons with medulla. During the development of hydrocephalus, lactate and LDH increased in most regions, the LDH M-subunit increased in the cortex, and ICDH decreased in most regions. However, ATP levels did not change. The increases in lactate, LDH and M-subunit suggested an anaerobic environment in the cell leading to activation of the anaerobic glycolysis. The decrease in ICDH represented a diminution of the tricarboxylic acid cycle. Through these alterations, the ATP level can be kept constant during the course of hydrocephalus, allowing the brain to create a better biochemical milieu.

Changes in brain glutamine synthetase activity in congenital hydrocephalic rats (LEW-HYR) after ventriculoperitoneal shunt.

Significantly reduced activities of glutamine synthetase (GS), which is predominantly present in glial cells, occur in the early stage of congenital hydrocephalic rat (LEW-HYR) brain development. GS activity is reported to be related to brain dysfunction. The effect of ventriculoperitoneal (VP) shunt on the suppression of GS activity was studied in the LEW-HYR. VP shunting improved the attenuation of GS activity in the LEW-HYR and the response of GS activity to methionine sulfoximine (a competitive GS inhibitor) treatment was similar to that seen in normal siblings. However, no enhancement of GS activity by hydrocortisone could be detected, although this enhancement occurs in the normal siblings. These results suggest that VP shunting is not completely effective in improving the suppression of brain GS activity in the LEW-HYR, since the suppression of GS activity in the LEW-HYR might be programmed genetically.

Immunohistochemical localization of superoxide dismutase in congenital hydrocephalic rat brain.

The effects of active oxygen species in the development of congenital hydrocephalus have been investigated. Superoxide dismutase (SOD) is one of the scavengers of active oxygen species and there have been many recent reports on the relationship between neurological disorders by active oxygen species following reperfusion for ischemic brain and SOD. In this study, the localization of Cu-SOD and Zn-SOD in WIC-Hyd congenitally hydrocephalic rat brains was identified by the enzyme unlabeled antibody method. We examined the localization of SOD in the choroid plexus, hippocampus, and ependymal cells of the lateral ventricle and aqueduct of WIC-Hyd rats. SOD was hardly observed in the choroid plexus and faintly localized in the hippocampus and ependymal cells of the congenitally hydrocephalic brain, but was observed equally in the cytoplasm of the choroid plexus, hippocampus, and ependymal cells in control animals. In the hippocampus, less SOD was found in hydrocephalic rats than in controls. The SOD was slightly observed in the CA1 pyramidal cells in hydrocephalic rats. In the lateral ventricle and aqueductal ependyma, less SOD was found in hydrocephalic than in controls rats. The amount of Cu, Zn-SOD in the congenitally hydrocephalic rat brain was less than in the control, especially in the choroid plexus. Therefore, we suspect that the production of SOD is congenitally reduced in the congenitally hydrocephalic rat brain, and this may promote the impairment of the function of choroid plexus and cilia due to increased active oxygen species. The reduction of SOD in the choroid plexus, hippocampus and ependymal cells of ventricles or aqueduct may promote the development of hydrocephalus in the congenitally hydrocephalic rat.

Energy metabolism in kaolin-induced hydrocephalic rat brain. Assessed by phosphorus (31P) magnetic resonance spectroscopy and the diversity of lactate-dehydrogenase and its isoenzyme patterns.

Energy metabolism in kaolin-induced hydrocephalic rat brain was assessed by means of 31-phosphorus magnetic resonance spectroscopy and measurement of the activity of lactate dehydrogenase (LDH) as well as its isoenzyme patterns. Decreases in beta-adenosine triphosphate and phosphocreatine were observed in hydrocephalic rat brains. While the intracellular pH was decreased at 2 to 4 weeks, it showed some recovery 6 weeks after injection of kaolin. The activity of LDH increased in the hydrocephalic state, and its isoenzyme-pattern changes were as follows: the LDH5 fraction was predominant in 1-week to 4-week rats while the LDH4 fraction was predominant in 4-week rat brains, and at 6-weeks, the LDH4 and LDH5 fractions were decreased. These data from rat brains with kaolin-induced hydrocephalus indicate that anaerobic glycolysis is the primary pathway of energy metabolism in the acute hydrocephalic state, while in the chronic state the emphasis shifts to aerobic glycolysis.

Raphe-cell transplantation into the hippocampus of the hydrocephalic rat brain.

Raphe-cell transplantation into the hippocampus of the hydrocephalic rat brain.

Changes in cerebral microvasculature in congenital hydrocephalus of the inbred rat lew/jms: Light and electron microscopic examination

The vascular apparatus in congenitally hydrocephalic rat brains was studied. The characteristic findings were structural changes in the small vessels with formation of an intracerebral cavity in the periventricular white matter. Stenotic or occluded blood vessels were located in an edematous area adjacent to the dilated lateral ventricles. Electron microscopically, the endothelial cells of capillaries and venules in the periventricular edematous region showed an irregular surface with indentations, and contained numerous plasmalemmal vesicles. Occluded capillaries were found in the border zone between the edematous and nonedematous area. These vascular changes indicate the presence of a disturbed microcirculation in the hydrocephalic brain.

The ventricular system in hydrocephalic rat brains produced by a deficiency of vitamin B12 or of folic acid in the maternal diet

The ventricular system in hydrocephalic rat brains produced by a deficiency of vitamin B₁₂ or of folic acid in the maternal diet