Rat Brain Cells Research Articles

In vitro models to study insulin and glucocorticoids modulation of trimethyltin (TMT)-induced neuroinflammation and neurodegeneration, and in vivo validation in db/db mice.

Brain susceptibility to a neurotoxic insult may be increased in a compromised health status, such as metabolic syndrome. Both metabolic syndrome and exposure to trimethyltin (TMT) are known to promote neurodegeneration. In combination the two factors may elicit additive or compensatory/regulatory mechanisms. Combined effects of TMT exposure (0.5-1μM) and mimicked metabolic syndrome-through modulation of insulin and glucocorticoid (GC) levels-were investigated in three models: tridimensional rat brain cell cultures for neuron-glia effects; murine microglial cell line BV-2 for a mechanistic analysis of microglial reactivity; and db/db mice as an in vivo model of metabolic syndrome. In 3D cultures, low insulin condition significantly exacerbated TMT's effect on GABAergic neurons and promoted TMT-induced neuroinflammation, with increased expression of cytokines and of the regulator of intracellular GC activity, 11β-hydroxysteroid dehydrogenase 1 (11β-Hsd1). Microglial reactivity increased upon TMT exposure in medium combining low insulin and high GC. These results were corroborated in BV-2 microglial cells where lack of insulin exacerbated the TMT-induced increase in 11β-Hsd1 expression. Furthermore, TMT-induced microglial reactivity seems to depend on mineralocorticoid receptor activation. In diabetic BKS db mice, a discrete exacerbation of TMT neurotoxic effects on GABAergic neurons was observed, together with an increase of interleukin-6 (IL-6) and of basal 11β-Hsd1 expression as compared to controls. These results suggest only minor additive effects of the two brain insults, neurotoxicant TMT exposure and metabolic syndrome conditions, where 11β-Hsd1 appears to play a key role in the regulation of neuroinflammation and of its protective or neurodegenerative consequences.

Argininosuccinate neurotoxicity and prevention by creatine in argininosuccinate lyase deficiency: An in vitro study in rat three-dimensional organotypic brain cell cultures.

The urea cycle disorder (UCD) argininosuccinate lyase (ASL) deficiency, caused by a defective ASL enzyme, exhibits a wide range of phenotypes, from life-threatening neonatal hyperammonemia to asymptomatic patients, with only the biochemical marker argininosuccinic acid (ASA) elevated in body fluids. Remarkably, even without ever suffering from hyperammonemia, patients often develop severe cognitive impairment and seizures. The goal of this study was to understand the effect on the known toxic metabolite ASA and the assumed toxic metabolite guanidinosuccinic acid (GSA) on developing brain cells, and to evaluate the potential role of creatine (Cr) supplementation, as it was described protective for brain cells exposed to ammonia. We used an in vitro model, in which we exposed three-dimensional (3D) organotypic rat brain cell cultures in aggregates to different combinations of the metabolites of interest at two time points (representing two different developmental stages). After harvest and cryopreservation of the cell cultures, the samples were analyzed mainly by metabolite analysis, immunohistochemistry, and western blotting. ASA and GSA were found toxic for astrocytes and neurons. This toxicity could be reverted in vitro by Cr. As well, an antiapoptotic effect of ASA was revealed, which could contribute to the neurotoxicity in ASL deficiency. Further studies in human ASL deficiency will be required to understand the biochemical situation in the brain of affected patients, and to investigate the impact of high or low arginine doses on brain Cr availability. In addition, clinical trials to evaluate the beneficial effect of Cr supplementation in ASL deficiency would be valuable.

Lipid Heterogeneity between Astrocytes and Neurons Revealed by Single‐Cell MALDI‐MS Combined with Immunocytochemical Classification

AbstractTranscriptomics characterizes cells based on their potential molecular repertoire whereas direct mass spectrometry (MS) provides information on the actual compounds present within cells. Single‐cell matrix‐assisted laser desorption/ionization (MALDI) MS can measure the chemical contents of individual cells but spectra are difficult to correlate to conventional cell types, limiting the metabolic information obtained. We present a protocol that combines MALDI‐MS with immunocytochemistry to assay over a thousand individual rat brain cells. The approach entwines the wealth of knowledge obtained by immunocytochemical profiling with mass spectral information on the predominant lipids within each cell. While many lipid species showed a high degree of similarity between neurons and astrocytes, seventeen significantly differed between the two cell types, including four phosphatidylethanolamines elevated in astrocytes and nine phosphatidylcholines in neurons.

Lipid Heterogeneity between Astrocytes and Neurons Revealed by Single-Cell MALDI-MS Combined with Immunocytochemical Classification.

Transcriptomics characterizes cells based on their potential molecular repertoire whereas direct mass spectrometry (MS) provides information on the actual compounds present within cells. Single-cell matrix-assisted laser desorption/ionization (MALDI) MS can measure the chemical contents of individual cells but spectra are difficult to correlate to conventional cell types, limiting the metabolic information obtained. We present a protocol that combines MALDI-MS with immunocytochemistry to assay over a thousand individual rat brain cells. The approach entwines the wealth of knowledge obtained by immunocytochemical profiling with mass spectral information on the predominant lipids within each cell. While many lipid species showed a high degree of similarity between neurons and astrocytes, seventeen significantly differed between the two cell types, including four phosphatidylethanolamines elevated in astrocytes and nine phosphatidylcholines in neurons.

Napabucasin prevents brain injury in neuronal neonatal rat cells through suppression of apoptosis and inflammation

The present study investigates the protective effect of napabucasin on the expression of apoptosis markers and inflammatory factors in the neuronal rat cells with post-isolation damage. The level of ROS determined by the fluorescence measurement in the neuronal rat cells with post-isolation damage was 310.21 RFU compared to 21.45 RFU in sham cell cultures. Napabucasin treatment decreased ROS level in the neuronal rat cells with post-isolation damage in dose based manner. ROS level decreased to 278.67, 203.65, 163.32 and 26.87 RFU, respectively in 1, 2, 3 and 4 μM napabucasin treated cell cultures. Treatment with napabucasin increased GSH level significantly (P < 0.05) in the neuronal rat cells with post-isolation damage. Napabucasin treatment at with 1, 2, 3 and 4 μM concentrations increased SOD activity to 2.4, 3.6, 5.1 and 6.1 U/mg, respectively. Treatment with napabucasin increased the activity of catalase in dose based manner. Napabucasin treatment increased Gpx in injured brain cells of neonatal rats. A significant (P < 0.05) increase in the activity of AChE was observed in neuronal rat cells with post-isolation damage on treatment with napabucasin. Treatment with napabucasin reduced the level of TNF-α and IL-6 significantly (P < 0.05) compared to untreated group. Napabucasin treatment decreased the expression of Bax, caspase-3 and p53 proteins in the neuronal rat cells with post-isolation damage. Napabucasin treatment protects post-isolation damage in the neuronal cells of neonatal rats by suppression of apoptosis and oxidative stress. Therefore, napabucasin can be used for the treatment of brain injury.

Intranasal delivery of hGDNF plasmid DNA nanoparticles results in long-term and widespread transfection of perivascular cells in rat brain

The intranasal route of administration allows large therapeutics to circumvent the blood–brain barrier and be delivered directly to the CNS. Here we examined the distribution and pattern of cellular transfection, and the time course of transgene expression, in the rat brain after intranasal delivery of plasmid DNA nanoparticles (NPs) encoding hGDNF fused with eGFP. Intranasal administration of these NPs resulted in transfection and transgene expression throughout the rat brain, as indicated by eGFP ELISA and eGFP-positive cell counts. Most of the transfected cells were abluminal and immediately adjacent to capillaries and are likely pericytes, consistent with their distribution by perivascular transport. Intranasal administration of these plasmid DNA NPs resulted in significant, long-term transgene expression in rat brain, with highest levels at 1 week and continued expression for 6 months. These results provide evidence in support of intranasal DNA NPs as a non-invasive, long-term gene therapy approach for various CNS disorders.

Alleviation of Stress-Induced Damage to Rat Brain Cells by Transcranial Electromagnetic Stimulation

The effect of transcranial electromagnetic stimulation on immobilization stress-induced damage to rat brain cells was studied. Electromagnetic stimulation was performed by microwave (λ = 5.6 mm) electromagnetic radiation with a power density of 0.67, 1.3, and 2.0 W/cm2 modulated by low-frequency pulses with a repetition rate of 78 Hz. A statistically significant blocking effect of electromagnetic stimulation on the process of stress-induced damage to brain cells (neurons) was detected in all three cases as the state of the neural network cells before and after stress exposure was compared. The most pronounced anti-stress effect was observed when electromagnetic stimulation with a power of 1.3 W/cm2 was used. A biophysical model of the anti-stress effect is proposed: according to the model, microwave radiation causes a globule–tangle phase transition in albumin, the major protein of the cerebrospinal fluid, and the tryptophan molecule fixed inside the globule is released. Free tryptophan enters the brain with the cerebrospinal fluid flow and enhances serotonin production, which blocks the stress effect, in the neural network of the brain.

Glutamine Synthetase in Rat Brain Cells

Objective. To use an immunohistochemical method to study glutamine synthetase (GS)-synthesizing brain cells. Materials and methods. Enzyme was detected on frontal rat brain sections (n = 10) using mouse monoclonal antibodies. Specimens were analyzed by light and confocal laser microscopy. Results. GS was found to be expressed in all areas of the brain, mainly by two types of cells, with different structures and topographies. The main type of cell with immunopositive reactions to glial fibrillary acidic protein were identical to astrocytes. The other structural and locational type of cell differed from typical astrocytes. Conclusions. The data obtained here provide evidence that GS is not a selective marker for any particular population of rat brain cells.

MRNA expression of transient receptor potential melastatin (TRPM) channels 2 and 7 in perinatal brain development

TRPM7 and TRPM2 are non-specific cation channels of the Transient Receptor Potential channel superfamily. Each channel has gained attention for their potential to mediate oxidative and anoxic cell death (Rama and García, 2016; Nazıroğlu, 2011a; Abiria et al., 2017; Sun, 2017), however their physiological expression and roles in the developing brain remain poorly defined. We employed real-time reverse transcription PCR to examine mRNA expression of TRPM7 and TRPM2 in the developing rat brain and brain-specific cell types. We determined the temporal and spatial expression patterns at four developmental time points (postnatal day 7, 14, 21, and 90) in four critical regions of the brain (cortex, hippocampus, striatum, and cerebellum) and examined gene expression in neuronal, astrocytic, and microglial primary cell cultures. Our results revealed that TRPM7 mRNA expression peaks in the cortex at 2-weeks after birth, and thus correlates most closely with a period of rat brain development associated with neurite outgrowth, which is heightened at 2-weeks after birth. Our cell-specific gene expression assays revealed that TRPM7 was expressed at equivalent levels in neurons, astrocytes, and microglia. Conversely, TRPM2 was most highly expressed in microglia with little expression in neurons and astrocytes. In the hippocampus and striatum, the expression profile of TRPM2 parallels the perinatal expression timeline for microglial infiltration and maturation in the rat brain. Microglial maturation is highest from the time of birth, up to 7-days, but subsequently declines. The latter developmental expression profiles indicate a role for TRPM2 in microglial activation.

Short Term Development and Fate of MGE-Like Neural Progenitor Cells in Jaundiced and Non-Jaundiced Rat Brain

Neonatal hyperbilirubinemia targets specific brain regions and can lead to kernicterus. One of the most debilitating symptoms of kernicterus is dystonia, which results from bilirubin toxicity to the globus pallidus (GP). Stem cell transplantation into the GP to replace lost neurons and restore basal ganglia circuits function is a potential therapeutic strategy to treat dystonia in kernicterus. In this study we transplanted human medial ganglionic eminence (MGE)-like neural progenitor cells (NPCs) that we differentiated into a primarily gamma-aminobutyric acid (GABA)ergic phenotype, into the GP of non-immunosuppressed jaundiced (jj) and non-jaundiced (Nj) rats. We assessed the survival and development of graft cells at three time-points post-transplantation. While grafted MGE-like NPCs survived and generated abundant fibers in both jj and Nj brains, NPC survival was greater in the jj brain. These results were consistent with our previous finding that excitatory spinal interneuron-like NPCs exhibited a higher survival rate in the jj brain than in the Nj brain. Our findings further support our hypothesis that slightly elevated bilirubin levels in the jj brain served as an antioxidant and immunosuppressant to protect the transplanted cells. We also identified graft fibers growing toward brain regions that receive projections from the GP, as well as host fibers extending toward the graft. These promising findings suggest that MGE-like NPCs may have the capacity to restore the circuits connecting GP and other nuclei.

Ultrastructural Features of Alkhumra Hemorrhagic Fever Virus Infection of Cells Under In Vivo and In Vitro Conditions.

Alkhumra hemorrhagic fever virus (AHFV) is an emerging novel flavivirus that was discovered in Saudi Arabia in 1995. The virus has since caused several outbreaks in the country that resulted in case fatality rates ranging from 1% to 25%. Meager information has been published on the ultrastructural features of the virus on cells under in vitro or in vivo conditions. The present electron microscopic study examined and compared the intracellular growth of the AHFV on the LLC-MK2 cells and brain cells of new born Wistar rats, inoculated intracerebrally. The cytopathological changes in both cell systems were noted, and localization of the virus particles in different cellular components was observed. Both apoptotic and lytic cell interactions were seen in the electron micrographs of both the LLC-MK2 and the rat brain cells. The results were discussed in relation to similar situations reported for other virus members of the genus Flavivirus.

Morphological alterations induced by the exposure to TiO2 nanoparticles in primary cortical neuron cultures and in the brain of rats.

Nowadays, nanoparticles (NPs) of titanium dioxide (TiO2) are abundantly produced. TiO2 NPs are present in various food products, in paints, cosmetics, sunscreens and toothpastes. However, the toxicity of TiO2 NPs on the central nervous system has been poorly investigated until now. The aim of this study was to evaluate the toxicity of TiO2 NPs on the central nervous system in vitro and in vivo. In cell cultures derived from embryonic cortical brain of rats, a significant decrease in neuroblasts was observed after 24 to 96 h of incubation with TiO2 NPs (5 to 20 μg/ml). This phenomenon resulted from an inhibition of neuroblast proliferation and a concomitant increase in apoptosis. In the same time, a gliosis, characterized by an increase in proliferation of astrocytes and the hypertrophy of microglial cells, occurred. The phagocytosis of TiO2 NPs by microgliocytes was also observed. In vivo, after intraperitoneal injection, the TiO2 NPs reached the brain through the blood brain barrier and the nanoparticles promoted various histological injuries such as cellular lysis, neuronal apoptosis, and inflammation. A reduction of astrocyte population was observed in some brain area such as plexiform zone, cerebellum and subependymal area. An oxidative stress was also detected by immunohistochemistry in neurons of hippocampus, cerebellum and in subependymal area. In conclusion, our study demonstrated clearly the toxic impact of TiO2 NPs on rat brain and neuronal cells and pointed about not yet referenced toxicity impacts of TiO2 such as the reduction of neuroblast proliferation both in vitro and in vivo.

TGF-β1 EXPRESSION BY GLIOMA C6 CELLS IN VITRO

FRBCS was obtained from suspensions of fetal rat brain cells on the 14th (E14) day of gestation. C6glioma cells were cultured for 48h in the presence of FRBCS or FRBCS + anti-TGF-β1 monoclonal antibody. Immunocytochemical staining for TGF-β1 and p53was performed. The proportion of TGF-β1-immunopositive tumor cells in C6glioma cultures was statistically significantly higher than in the control cell cultures of normal fetal rat brain. FRBCS reduced the proportion of TGF-β1-immunopositive tumor cells and increased the proportion of p53-immunopositive cells in C6glioma cultures. In cells cultured with FRBCS + anti-TGF-β1monoclonal antibody, the above effects of FRBCS were abrogated. The obtained results suggest that TGF-β1seems to be responsible for decrease in TGF-β1 expression and increase in p53expression in C6glioma cells treated with FRBCS.

Methodological aspects of MRI of transplanted superparamagnetic iron oxide-labeled mesenchymal stem cells in live rat brain.

In vivo tracking of transplanted mesenchymal stem cells (MSCs) migration and homing is vital for understanding the mechanisms of beneficial effects of MSCs transplantation in animal models of diseases and in clinical trials. Transplanted cells can be labeled with superparamagnetic iron oxide (SPIO) particles and visualized in vivo using a number of iron sensitive MRI techniques. However, the applicability of those techniques for SPIO-labeled MSCs tracking in live brain has not been sufficiently investigated. The goal of this study was to estimate the efficiency of various MRI techniques of SPIO-labeled cell tracing in the brain. To achieve that goal, the precision and specificity of T2WI, T2*WI and SWI (Susceptibility-Weighted Imaging) techniques of SPIO-labeled MSCs tracing in vitro and in live rat brain were for the first time compared in the same experiment. We have shown that SWI presents the most sensitive pulse sequence for SPIO-labeled MSCs MR visualization. After intracerebral administration due to limitations caused by local micro-hemorrhages the visualization threshold was 102 cells, while after intra-arterial transplantation SWI permitted detection of several cells or even single cells. There is just one publication claiming detection of individual SPIO-labeled MSCs in live brain, while the other state much lower sensitivity, describe detection of different cell types or high resolution tracing of MSCs in other tissues. This study confirms the possibility of single cell tracing in live brain and outlines the necessary conditions. SWI is a method convenient for the detection of single SPIO labeled MSCs and small groups of SPIO labeled MSCs in brain tissue and can be appropriate for monitoring migration and homing of transplanted cells in basic and translational neuroscience.

Effects of ginsenoside‑Rg1 on the proliferation and glial‑like directed differentiation of embryonic rat cortical neural stem cells invitro.

Ginsenoside-Rg1, the main active component of Panax notoginseng, exhibits a number of pharmacological functions, including promoting protein synthesis in the brain, increasing the number of synapses, improving memory and promoting recovery of brain function following injury. The effect of ginsenoside-Rg1 on proliferation and glial-like-directed differentiation in the cortical neural stem cells (NSCs) of embryonic rat brain was investigated. The present study used MTS assays to identify the optimum dose and window time of ginsenoside-Rg1 administration to stimulate the proliferation of cortical NSCs in the rat embryonic tissue. The oxygen glucose deprivation (OGD) set-up was used as a cell injury model. Immunofluorescent staining was used for identification of NSCs and subsequent observation of their proliferation and glial-like directed differentiation. Nestin expression was the marker for the presence of NSCs among the cortical cells of embryonic rat brain. The optimum dose of ginsenoside-Rg1 for proliferation of NSCs was 0.32 µg/ml. The optimum window time of 0.32 µg/ml ginsenoside-Rg1 administration on proliferation of NSCs was 6 h. Ginsenoside-Rg1 at 0.32 µg/ml concentration promoted incorporation of bromo-2-deoxyuridine, and expression of nestin and vimentin in primary and passaged NSCs, and NSCs following OGD. Ginsenoside-Rg1 had a role in promoting proliferation and glial-like-directed differentiation of cortical NSCs. The plausible explanation for these responses is that ginsenoside-Rg1 acts similarly to the growth factors to promote the proliferation and differentiation of NSCs.

The characteristics of acetylation of histone H3 at Lys24 in the hippocampus and neocortex of rats that were exposed to hypoxic stress at different stages of prenatal development

Hypoxic stress has a considerable effect on fetal development and may lead to irreversible longterm developmental disorders of the brain, increasing the risk of neurological complications. Modern research shows that epigenetic mechanisms may play a key role in the development of these pathologies. Here, we studied histone H3 acetylation at lysine 24 in the neurons of the brain structures that are most sensitive to hypoxia (hippocampus and neocortex) after severe hypobaric hypoxia (180 mmHg, 3 h) on the 14–16th and 17–19th days of prenatal ontogeny. Using the immunohistochemical method, it was found that severe hypobaric hypoxia on the 14–16th and 17th–19th days of prenatal ontogeny leads to a prolonged (at least up to 3 months) decrease in the degree of acetylation of histone H3 at lysine 24, but not general histone acetylation, in the hippocampus and neocortex of rats. The intensity of changes depends both on the time of the presentation of hypoxia, and on the areas of the brain that are studied. Thus, in the CA1 region and the dentate gyrus of the hippocampus, hypoxia leads to more-pronounced changes in the number of immunopositive cells and cells with intense immunostaining to the H3 histones acetylated at lysine 24 than in the fifth layer of the neocortex. This may be due to the mismatch between the critical periods of the development of different regions of the brain and the differences in their sensitivity to hypoxia. The discovered modifications of the epigenetic status of brain cells in rats that were subjected to prenatal hypoxia may underlie previously shown long-term changes in behavior and learning abilities.

Investigations of primary blast-induced traumatic brain injury

The development of an advanced blast simulator (ABS) has enabled the reproducible generation of single-pulse shock waves that simulate free-field blast with high fidelity. Studies with rodents in the ABS demonstrated the necessity of head restraint during head-only exposures. When the head was not restrained, violent global head motion was induced by pressures that would not produce similar movement of a target the size and mass of a human head. This scaling artefact produced changes in brain function that were reminiscent of traumatic brain injury (TBI) due to impact-acceleration effects. Restraint of the rodent head eliminated these, but still produced subtle changes in brain biochemistry, showing that blast-induced pressure waves do cause brain deficits. Further experiments were carried out with rat brain cell aggregate cultures that enabled the conduct of studies without the gross movement encountered when using rodents. The suspension nature of this model was also exploited to minimize the boundary effects that complicate the interpretation of primary blast studies using surface cultures. Using this system, brain tissue was found not only to be sensitive to pressure changes, but also able to discriminate between the highly defined single-pulse shock waves produced by underwater blast and the complex pressure history exposures experienced by aggregates encased within a sphere and subjected to simulated air blast. The nature of blast-induced primary TBI requires a multidisciplinary research approach that addresses the fidelity of the blast insult, its accurate measurement and characterization, as well as the limitations of the biological models used.

GLP-1 increases Kiss-1 mRNA expression in kisspeptin-expressing neuronal cells.

Feeding-related metabolic factors exert regulatory influences on the hypothalamic-pituitary-gonadal axis. Glucagon-like peptide-1 (GLP-1) is an anorexigenic hormone synthesized from the ileum in response to food intake. The purpose of this study was to examine the direct effect of GLP-1 on hypothalamic kisspeptin and gonadotropin-releasing hormone (GnRH) expression using the rat clonal hypothalamic cell line rHypoE-8. GLP-1 significantly increased Kiss-1 mRNA expression in rHypoE-8 cells up to 1.94 ± 0.22-fold. This effect of GLP-1 on Kiss-1 gene expression was also observed in GT1-7 GnRH-producing neurons and in primary cultures of fetal rat brain. GLP-1 increased cAMP-mediated signaling, as determined by cAMP response element activity assays, but failed to activate extracellular signal-regulated kinase pathways. Another anorexigenic factor, leptin, similarly increased Kiss-1 mRNA levels up to 1.34 ± 0.08-fold in rHypoE-8 cells. However, combined treatment with GLP-1 and leptin failed to potentiate their individual effects on Kiss-1 mRNA expression. Gnrh mRNA expression was not significantly increased by GLP-1 stimulation in rHypoE-8, but kisspeptin significantly stimulated the expression of Gnrh mRNA in these cells. Our current observations suggest that the anorexigenic peptide GLP-1 directly regulates Kiss-1 mRNA expression in these hypothalamic cell lines and in neuronal cells of fetal rat brain and affects the expression of Gnrh mRNA.

Postvaccination Accumulation of the Influenza Virus Antigen in the Rat Choroid Plexus

We examined the accessibility of influenza virus and diphtheria-tetanus toxin (DiTe) antigens to the choroid plexus (CP) within the postvaccination period and the expression of CD11b molecules (by immunohistochemistry). Eighteen Dark Agouti (DA) rats were divided into three groups: (i) animals administered with influenza vaccine (Flu), (ii) animals administered with DiTe vaccine (DiTe), and (iii) nontreated (Contr) animals. The serum antibody titers following influenza and diphtheria-tetanus vaccination were detected by the ELISA test. Immunohistochemical staining revealed a great number of viral antigen-positive and CD11b-positive brain cells in Flu rats compared to a very small number of the respective cells in DiTe animals and no staining in the Contr group. DiTe- and Flu-rats showed significant increases in the serum anti-tetanus toxoid and anti-influenza virus antibody levels compared to those in the Contr group. The results obtained attract attention towards the dynamic role of the CP in the immunosurveillance of the CNS. Based on the viral antigen deposits accumulated in the CP, it has been proposed that the latter can play an active role in modulation of the immune response after influenza vaccine immunization.

Pericytes promote abnormal tumor angiogenesis in a rat RG2 glioma model.

In glioma angiogenesis, tumor vessels cause morphological and functional abnormalities associated with malignancy and tumor progression. We hypothesized that certain structural changes or scantiness of functional pericytes may be involved in the formation of dysfunctional blood vessels in gliomas. In this study, we performed morphological examinations to elucidate the possible involvement of pericytes in brain tumor vessel abnormalities using a rat RG2 glioma model. After implantation of RG2 glioma cells in the syngeneic rat brain, gliomas were formed as early as day 7. In immunohistochemical examinations, desmin-positive pericytes, characterized by morphological abnormalities, were abundantly found on leaky vessels, as assessed by extravasation of lectin and high-molecular-weight dextrans. Interestingly, desmin-positive pericytes seemed to be characteristic of gliomas in rats. These pericytes were also found to express heat-shock protein 47, which plays an important role in the formation of the basement membrane, suggesting that RG2 pericytes promoted angiogenesis by producing basement membrane as a scaffold for newly forming blood vessels and caused functional abnormalities. We concluded that RG2 pericytes may be responsible for abnormal tumor angiogenesis lacking the functional ability to maintain the blood-brain barrier.