Protein and synthetic polymer injection for induction of obstructive hydrocephalus in rats

<p>Abstract</p> <p>Background</p> <p>The objective of this study was to develop a simple and inexpensive animal model of induced obstructive hydrocephalus with minimal tissue inflammation, as an alternative to kaolin injection.</p> <p>Materials</p> <p>Two-hundred and two male Sprague-Dawley rats aged 3 weeks received intracisternal injections of kaolin (25% suspension), Matrigel, type 1 collagen from rat tail, fibrin glue (Tisseel), n-butyl-cyanoacrylate (NBCA), or ethylene vinyl alcohol copolymer (Onyx-18 and Onyx-34). Magnetic resonance imaging was used to assess ventricle size. Animals were euthanized at 2, 5, 10 and 14 days post-injection for histological analysis.</p> <p>Results</p> <p>Kaolin was associated with 10% mortality and successful induction of hydrocephalus in 97% of survivors (ventricle area proportion 0.168 ± 0.018). Rapidly hardening agents (fibrin glue, NBCA, vinyl polymer) had high mortality rates and low success rates in survivors. Only Matrigel had relatively low mortality (17%) and moderate success rate (20%). An inflammatory response with macrophages and some lymphocytes was associated with kaolin. There was negligible inflammation associated with Matrigel. A severe inflammatory response with giant cell formation was associated with ethylene vinyl alcohol copolymer.</p> <p>Conclusion</p> <p>Kaolin predictably produces moderate to severe hydrocephalus with a mild chronic inflammatory reaction and fibrosis of the leptomeninges. Other synthetic polymers and biopolymers tested are unreliable and cause different types of inflammation.</p

Blood-brain barrier disruption in CCL2 transgenic mice during pertussis toxin-induced brain inflammation

BACKGROUND: The chemokine CCL2 has an important role in the recruitment of inflammatory cells into the central nervous system (CNS). A transgenic mouse model that overexpresses CCL2 in the CNS shows an accumulation of leukocytes within the perivascular space surrounding vessels, and which infiltrate into the brain parenchyma following the administration of pertussis toxin (PTx). METHODS: This study used contrast-enhanced magnetic resonance imaging (MRI) to quantify the extent of blood–brain barrier (BBB) disruption in this model pre- and post-PTx administration compared to wild-type mice. Contrast-enhanced MR images were obtained before and 1, 3, and 5 days after PTx injection in each animal. After the final imaging session fluorescent dextran tracers were administered intravenously to each mouse and brains were examined histologically for cellular infiltrates, BBB leakage and tight junction protein. RESULTS: BBB breakdown, defined as a disruption of both the endothelium and glia limitans, was found only in CCL2 transgenic mice following PTx administration and seen on MR images as focal areas of contrast enhancement and histologically as dextrans leaking from blood vessels. No evidence of disruption in endothelial tight junctions was observed. CONCLUSION: Genetic and environmental stimuli were needed to disrupt the integrity of the BBB in this model of neuroinflammation

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

Age-related differences in 1p and 19q deletions in oligodendrogliomas

BACKGROUND: Recent reports indicate that anaplastic oligodendrogliomas frequently show allelic losses on chromosome arms 1p and 19q, and that these deletions are associated with better chemotherapeutic response and overall patient survival. Because of the diversified genetic makeup of the population and the centralized provincial referral system for brain tumor patients in Manitoba, the epidemiological features of such tumors sometimes differ from the published data acquired from non-community based settings. In this study, we assessed the prevalence of allelic deletions for chromosome arms 1p and 19q in anaplastic and in low-grade oligodendrogliomas in the Manitoba population. METHODS: Loss of heterozygosity (LOH) analysis of brain tumors was carried out using 4 microsatellite markers (D1S508, D1S2734, D19S219 and D19S412) and a PCR based assay. The tumors were consecutively acquired during the period September 1999–March 2001 and a total of 63 tumors were assessed. RESULTS: We found that allelic loss of chromosome 1p and 19q was higher in oligodendrogliomas than in other diffuse gliomas and that for anaplastic oligodendrogliomas, younger patients exhibited significantly more deletions than older patients (>60 years of age). CONCLUSIONS: These studies suggest that age may be a factor in the genetic alterations of oligodendrogliomas. In addition, these studies demonstrate that this assay can easily be carried out in a cost-effective manner in a small tertiary center

MECP2 Mutation Interrupts Nucleolin–mTOR–P70S6K Signaling in Rett Syndrome Patients

Rett syndrome (RTT) is a severe and rare neurological disorder that is caused by mutations in the X-linked MECP2 (methyl CpG-binding protein 2) gene. MeCP2 protein is an important epigenetic factor in the brain and in neurons. In Mecp2-deficient neurons, nucleoli structures are compromised. Nucleoli are sites of active ribosomal RNA (rRNA) transcription and maturation, a process mainly controlled by nucleolin and mechanistic target of rapamycin (mTOR)–P70S6K signaling. Currently, it is unclear how nucleolin–rRNA–mTOR–P70S6K signaling from RTT cellular model systems translates into human RTT brain. Here, we studied the components of nucleolin–rRNA–mTOR–P70S6K signaling in the brain of RTT patients with common T158M and R255X mutations. Immunohistochemical examination of T158M brain showed disturbed nucleolin subcellular localization, which was absent in Mecp2-deficient homozygous male or heterozygote female mice, compared to wild type (WT). We confirmed by Western blot analysis that nucleolin protein levels are altered in RTT brain, but not in Mecp2-deficient mice. Further, we studied the expression of rRNA transcripts in Mecp2-deficient mice and RTT patients, as downstream molecules that are controlled by nucleolin. By data mining of published ChIP-seq studies, we showed MeCP2-binding at the multi-copy rRNA genes in the mouse brain, suggesting that rRNA might be a direct MeCP2 target gene. Additionally, we observed compromised mTOR–P70S6K signaling in the human RTT brain, a molecular pathway that is upstream of rRNA–nucleolin molecular conduits. RTT patients showed significantly higher phosphorylation of active mTORC1 or mTORC2 complexes compared to age- and sex-matched controls. Correlational analysis of mTORC1/2–P70S6K signaling pathway identified multiple points of deviation from the control tissues that may result in abnormal ribosome biogenesis in RTT brain. To our knowledge, this is the first report of deregulated nucleolin–rRNA–mTOR–P70S6K signaling in the human RTT brain. Our results provide important insight toward understanding the molecular properties of human RTT brain

A novel Alzheimer disease locus located near the gene encoding tau protein

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordAPOE ε4, the most significant genetic risk factor for Alzheimer disease (AD), may mask effects of other loci. We re-analyzed genome-wide association study (GWAS) data from the International Genomics of Alzheimer's Project (IGAP) Consortium in APOE ε4+ (10 352 cases and 9207 controls) and APOE ε4- (7184 cases and 26 968 controls) subgroups as well as in the total sample testing for interaction between a single-nucleotide polymorphism (SNP) and APOE ε4 status. Suggestive associations (P<1 × 10-4) in stage 1 were evaluated in an independent sample (stage 2) containing 4203 subjects (APOE ε4+: 1250 cases and 536 controls; APOE ε4-: 718 cases and 1699 controls). Among APOE ε4- subjects, novel genome-wide significant (GWS) association was observed with 17 SNPs (all between KANSL1 and LRRC37A on chromosome 17 near MAPT) in a meta-analysis of the stage 1 and stage 2 data sets (best SNP, rs2732703, P=5·8 × 10-9). Conditional analysis revealed that rs2732703 accounted for association signals in the entire 100-kilobase region that includes MAPT. Except for previously identified AD loci showing stronger association in APOE ε4+ subjects (CR1 and CLU) or APOE ε4- subjects (MS4A6A/MS4A4A/MS4A6E), no other SNPs were significantly associated with AD in a specific APOE genotype subgroup. In addition, the finding in the stage 1 sample that AD risk is significantly influenced by the interaction of APOE with rs1595014 in TMEM106B (P=1·6 × 10-7) is noteworthy, because TMEM106B variants have previously been associated with risk of frontotemporal dementia. Expression quantitative trait locus analysis revealed that rs113986870, one of the GWS SNPs near rs2732703, is significantly associated with four KANSL1 probes that target transcription of the first translated exon and an untranslated exon in hippocampus (P≤1.3 × 10-8), frontal cortex (P≤1.3 × 10-9) and temporal cortex (P≤1.2 × 10-11). Rs113986870 is also strongly associated with a MAPT probe that targets transcription of alternatively spliced exon 3 in frontal cortex (P=9.2 × 10-6) and temporal cortex (P=2.6 × 10-6). Our APOE-stratified GWAS is the first to show GWS association for AD with SNPs in the chromosome 17q21.31 region. Replication of this finding in independent samples is needed to verify that SNPs in this region have significantly stronger effects on AD risk in persons lacking APOE ε4 compared with persons carrying this allele, and if this is found to hold, further examination of this region and studies aimed at deciphering the mechanism(s) are warranted