Rocio E. Gonzalez-Castaneda

A New Bilayer Chitosan Scaffolding as a Dural Substitute: Experimental Evaluation

OBJECTIVEnTo evaluate whether bilayer chitosan scaffolding (BChS) can provide a watertight dural closure and permit regeneration by fibroblasts in an experimental in vivo model.nnnMETHODSnIn the in vitro phase, BChS was elaborated and the following characteristics were evaluated: pore size, thickness, water absorption capacity, tensile strength, strain, and toughness. In the second in vivo phase, 27 durectomized New Zealand rabbits were randomly assigned into three duraplasty groups with autologous dura, collagen matrix (CM), or BChS. In all groups, fluid leakage pressure was measured at 10, 21, or 180 days. Histology response to regeneration was evaluated through hematoxylin and eosin stain.nnnRESULTSnBChS was standardized to obtain bilayer scaffoldings with a nonporous layer and a porous layer. The pore size was 10 μm, total thickness was 400 μm, strain was 57.8%, and tensile strength was 5.5 gr/mm(2). The physical characteristics of BChS allowed dural closure without cerebrospinal fluid (CSF) leak. There were no differences in fluid leakage pressures between the BChS, dura, and CM groups. Histologic analysis showed fibroblast migration with adequate dural regeneration.nnnCONCLUSIONSnBChS is an ideal alternative for a watertight dural closure because it can be sutured, and it induces organized regeneration with fibroblasts without evidence of fibrosis.

Stress by noise produces differential effects on the proliferation rate of radial astrocytes and survival of neuroblasts in the adult subgranular zone.

The subgranular zone (SGZ) in the dentate gyrus contains radial astrocytes, known as Type-1 or Type-B cells, which generate neuroblasts (Type-2 cells or Type-D cells) that give rise to granular neurons. Stress increases glucocorticoid levels that target SGZ and modify the proliferation and apoptosis of hippocampal cells. Yet, it is not well-known whether stress differentially affects SGZ progenitors. We investigated the effects of noise-induced stress on the rate of proliferation and apoptosis of the Type-1 cells, Type-2 cells and newly generated granular neurons in the SGZ. We exposed Balb/C mice to noise using a standardized rodents audiogram-fitted adaptation of a human noisy environment. We measured corticosterone serum levels at different time points. Animals received BrdU injections for 3 days and sequential sacrifices were done to carry out double-immunohistochemical analyses. We found that a 24-h noise exposure did not produce adaptative response in the curve of corticosterone as compared to a 12-h noise exposure. The percentage of BrdU+/GFAP+ cells was significantly reduced in the stress group as compared to controls. A high proportion of CASP-3+/GFAP+ radial astrocytes were found in the stress group. The percentage of BrdU+/doublecortin+ cells was higher in controls than in the stress group. Interestingly, the apoptosis rate of doublecortin-expressing cells in the stress group was slightly lesser than in controls. Remarkably, we did not find significant differences in the number of BrdU+/NeuN+ and CASP-3+/NeuN+ neurons. These data indicate that stress differentially affects the rate of proliferation and apoptosis in SGZ progenitors and suggest a possible compensatory mechanism to keep the net number of granular neurons.

Rapid Eye Movement Sleep Deprivation Produces Long-Term Detrimental Effects in Spatial Memory and Modifies the Cellular Composition of the Subgranular Zone.

Sleep deprivation (SD) affects spatial memory and proliferation in the dentate gyrus. It is unknown whether these deleterious effects persist in the long run. The aim of this study was to evaluate the proliferation, differentiation and maturation of neural progenitors as well as spatial memory 21 days after suffering SD. Sixty-day old male Balb/C mice were exposed to 72-h REM-SD. Spatial memory, cell fate, apoptosis and expression levels of insulin-like growth factor 1 receptor (IGF-1R) were evaluated in the hippocampus at 0, 14, and 21 days after SD or control conditions. After 21-days recovery period, memory performance was assessed with the Barnes maze, we found a significant memory impairment in SD mice vs. control (94.0 ± 10.2 s vs. 25.2 ± 4.5 s; p < 0.001). The number of BrdU+ cells was significantly decreased in the SD groups at day 14 (controls = 1.6 ± 0.1 vs. SD mice = 1.2 ± 0.1 cells/field; p = 0.001) and at day 21 (controls = 0.2 ± 0.03 vs. SD mice = 0.1 ± 0.02 cells/field; p < 0.001). A statistically significant decrease was observed in neuronal differentiation (1.4 ± 0.1 cells/field vs. 0.9 ± 0.1 cells/field, p = 0.003). Apoptosis was significantly increased at day 14 after SD (0.53 ± 0.06 TUNEL+ cells/field) compared to controls (0.19 ± 0.03 TUNEL+ cells/field p < 0.001) and at 21-days after SD (SD mice 0.53 ± 0.15 TUNEL+ cells/field; p = 0.035). At day 0, IGF-1R expression showed a statistically significant reduction in SD animals (64.6 ± 12.2 units) when compared to the control group (102.0 ± 9.8 units; p = 0.043). However, no statistically significant differences were found at days 14 and 21 after SD. In conclusion, a single exposition to SD for 72-h can induce deleterious effects that persist for at least 3 weeks. These changes are characterized by spatial memory impairment, reduction in the number of hippocampal BrdU+ cells and persistent apoptosis rate. In contrast, changes IGF-1R expression appears to be a transient event. Highlight Sleep deprivation affects spatial memory and proliferation in the dentate gyrus. To date it is unknown whether these deleterious effects are persistent over a long period of time. We analyzed the effects of sleep deprivation in the hippocampus after 21 days of recovery sleep. Our findings indicate that after sleep recovery, the detrimental effects of SD can be observed for at least 2 weeks, as shown by a reduction in memory performance, changes in the hippocampal cellular composition and higher apoptotic rate over a long period of time.

Sex-related effects of sleep deprivation on depressive- and anxiety-like behaviors in mice.

Anxiety and depressive symptoms are generated after paradoxical sleep deprivation (PSD). However, it is not clear whether PSD produces differential effects between females and males. The aim of this study was to assess the effect of PSD on anxiety- and depressive-like behaviors between sexes. Male and female BALB/c mice were divided in three groups: the control group, the 48-h PSD group and the 96-h PSD group. Immediately after PSD protocols, the forced swimming and open field test were applied. Sucrose consumption test was used to evaluate the middle-term effect of PSD. We found that corticosterone serum levels showed significant differences in the 96-h PSD females as compared to 96-h PSD males. In the open-field test, the 48-h and 96-h PSD females spent more time at the periphery of the field, and showed high locomotion as compared to males. In the elevated plus maze, the 48-h PSD females spent more time in closed arms than males, which is compatible with anxiety-like behavior. The forced swim test indicated that the 96-h PSD males spent more time swimming as compared to the 96-h PSD females. Remarkably, the 96-h PSD males had lower sucrose intake than the 96-h PSD females, which suggest that male mice have proclivity to develop a persistent depressive-like behavior late after PSD. In conclusion, male mice showed a significant trend to depressive-like behaviors late after sleep deprivation. Conversely, female have a strong tendency to display anxiety- and depressive-like behaviors immediately after sleep deprivation.

Early-life exposure to noise reduces mPFC astrocyte numbers and T-maze alternation/discrimination task performance in adult male rats

In this experiment, we evaluated the long-term effects of noise by assessing both astrocyte changes in medial prefrontal cortex (mPFC) and mPFC-related alternation/discrimination tasks. Twenty-one-day-old male rats were exposed during a period of 15 days to a standardized rats′ audiogram-fitted adaptation of a human noisy environment. We measured serum corticosterone (CORT) levels at the end of the exposure and periodically registered body weight gain. In order to evaluate the long-term effects of this exposure, we assessed the rats′ performance on the T-maze apparatus 3 months later. Astrocyte numbers and proliferative changes in mPFC were also evaluated at this stage. We found that environmental noise (EN) exposure significantly increased serum CORT levels and negatively affected the body weight gain curve. Accordingly, enduring effects of noise were demonstrated on mPFC. The ability to solve alternation/discrimination tasks was reduced, as well as the number of astroglial cells. We also found reduced cytogenesis among the mPFC areas evaluated. Our results support the idea that early exposure to environmental stressors may have long-lasting consequences affecting complex cognitive processes. These results also suggest that glial changes may become an important element behind the cognitive and morphological alterations accompanying the PFC changes seen in some stress-related pathologies.

Alterations of Growth Factors in Autism and Attention-Deficit/Hyperactivity Disorder

Growth factors (GFs) are cytokines that regulate the neural development. Recent evidence indicates that alterations in the expression level of GFs during embryogenesis are linked to the pathophysiology and clinical manifestations of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASD). In this concise review, we summarize the current evidence that supports the role of brain-derived neurotrophic factor, insulin-like growth factor 2, hepatocyte growth factor (HGF), glial-derived neurotrophic factor, nerve growth factor, neurotrophins 3 and 4, and epidermal growth factor in the pathogenesis of ADHD and ASD. We also highlight the potential use of these GFs as clinical markers for diagnosis and prognosis of these neurodevelopmental disorders.

Neural stem cells in the adult brain: From benchside to clinic

Increasing evidence indicates that neural stem cells (NSCs) play an important role in sustaining cellular homeostasis and brain tissue restoration. The study of all mechanisms that control and modulate the function of NSC is a crucial step for the design of therapies against chronic neurodegenerative processes. In this special issue of the journal, we had the pleasure to edit the topic entitled “Neural Stem Cells in the Adult Brain: From Benchside to Clinic.” This special compilation of paper was aimed to provide a global forum for publications of original peer-reviewed manuscripts that reported original research findings in the field of adult neural stem cell, including short communications, full-length research, and review articles. Below, we briefly discuss the papers you may find in this issue. n nK. Nakaguchi et al., in their paper entitled “Growth factors released from gelatin hydrogel microspheres increase new neurons in the adult mouse brain”, suggest that new neurons born in the subventricular zone (SVZ) may be able to replace neurons lost in degenerative disease or injury and improve or repair neurological deficits. In this excellent paper, they tested whether delivering growth factors via gelatin hydrogel microspheres can support neurogenesis in the SVZ. Their findings indicated that hepatocyte growth factor-containing microspheres increased the number of new neurons migrating from the SVZ towards the injured striatum in a stroke model in mouse. Therefore, they propose that gelatin hydrogel microspheres may be a good delivery tool for the sustained release of growth factors to promote neural regeneration of damaged brain tissues. n nJ. Tu and S. O. Ugoya discuss that traumatic brain injury (TBI) is one of the leading causes of major disability and death worldwide. Neural stem cells (NSCs) have recently been shown to contribute to the cellular remodeling and may represent a possible therapy for TBI. In their work the authors nicely summarized a critical assessment of recent data and developed a view comprising of six points to possible quality translation of NSCs in TBI. n nB. P. Carreira et al., in their paper entitled “Regulation of injury-induced neurogenesis by nitric oxide”, sustain that nitric oxide (NO), a pleiotropic signaling molecule in the central nervous system, is able to modulate neurogenesis, acting as a pro- or antineurogenic agent. In their interesting review, they discussed the relevance of the NO system for the treatment of neurodegenerative diseases or several pathological conditions that affect the brain. n nJ. Namiki et al. analyzed the phosphorylation of nestin, an intermediate filament protein commonly used as a neural stem/progenitor cell marker. Nestin is required for the survival and self-renewal of neural stem cells. In this study, the authors nicely reported CNS-specific phosphorylation sites in nestin that allow distinguishing vascular expression of nestin from other intermediate filament protein subtypes. n nHormonal signals from the pancreatic islets influence the energy homeostasis of the brain and vice versa. In an excellent review, M. Machida and coworkers explain the correlation between the insulin-mediated regulatory system of the CNS and the pancreatic endocrine system. Remarkably, adult neurogenesis from undifferentiated neural stem cells is greatly decreased in diabetic patients, and as a result their learning and memory functions decline. In their paper, the authors summarized latest research regarding this endocrinal and neurological relationship. n nL. Calatrava-Ferreras et al. explained that cerebellar ataxias, a heterogeneous group of diseases characterized by motor incoordination, may be treated using cell transplantations. Specifically they propose the use of human umbilical cord blood mononuclear cells as a promising approach for restoration of cerebellar function n nS. Martinez-Herrero et al. discuss that adrenomedullin (AM) acts as a growth and cell fate regulatory factor for adult neural stem cells. AM regulates the proliferation rate and the differentiation of stem/progenitor cells into neurons, astrocytes, and oligodendrocytes, probably through the PI3K/Akt pathway. AM gene is also able to regulate the cytoskeleton rearrangements, which is important for cellular morphogenesis. In addition, AM appears to contribute to neural stem cell growth regulation by allowing cells to pass through mitosis. Consequently, AM may contribute to program stem cells for future clinical uses. n nFinally, R. Ramos-Zuniga et al. discussed the ethical implications on the use of stem cells. They explain that every clinical project should take that into account, along with potential clinical applications, the principle of “primum non nocere” (first, do no harm). The authors also indicate the importance of keeping a close clinical surveillance to establish the possible risks in the use of stem-cell-based therapies. n nWith this compendium of cutting-edge review articles and original articles written for experts in the stem-cell field, we hope these in the field of adult neural stem cells will help be helpful and educational for readers. n n nOscar Gonzalez-Perez n nJose M. Garcia-Verdugo n nAlfredo Quinones-Hinojosa n nSonia Luquin n nGraciela Gudino-Cabrera n nRocio E. Gonzalez-Castaneda

Phenytoin enhances the phosphorylation of epidermal growth factor receptor and fibroblast growth factor receptor in the subventricular zone and promotes the proliferation of neural precursor cells and oligodendrocyte differentiation

Phenytoin is a widely used antiepileptic drug that induces cell proliferation in several tissues, such as heart, bone, skin, oral mucosa and neural precursors. Some of these effects are mediated via fibroblast growth factor receptor (FGFR) and epidermal growth factor receptor (EGFR). These receptors are strongly expressed in the adult ventricular–subventricular zone (V‐SVZ), the main neurogenic niche in the adult brain. The aim of this study was to determine the cell lineage and cell fate of V‐SVZ neural progenitors expanded by phenytoin, as well as the effects of this drug on EGFR/FGFR phosphorylation. Male BALB/C mice received 10 mg/kg phenytoin by oral cannula for 30 days. We analysed the proliferation of V‐SVZ neural progenitors by immunohistochemistry and western blot. Our findings indicate that phenytoin enhanced twofold the phosphorylation of EGFR and FGFR in the V‐SVZ, increased the number of bromodeoxyuridine (BrdU)+/Sox2+ and BrdU+/doublecortin+ cells in the V‐SVZ, and expanded the population of Olig2‐expressing cells around the lateral ventricles. After phenytoin removal, a large number of BrdU+/Receptor interacting protein (RIP)+ cells were observed in the olfactory bulb. In conclusion, phenytoin enhanced the phosphorylation of FGFR and EGFR, and promoted the expression of neural precursor markers in the V‐SVZ. In parallel, the number of oligodendrocytes increased significantly after phenytoin removal.

Environmental noise exposure modifies astrocyte morphology in hippocampus of young male rats

Background: Chronic exposure to noise induces changes on the central nervous system of exposed animals. Those changes affect not only the auditory system but also other structures indirectly related to audition. The hippocampus of young animals represents a potential target for these effects because of its essential role in individuals’ adaptation to environmental challenges. Objective: The aim of the present study was to evaluate hippocampus vulnerability, assessing astrocytic morphology in an experimental model of environmental noise (EN) applied to rats in pre-pubescent stage. Materials and Methods: Weaned Wistar male rats were subjected to EN adapted to the rats’ audiogram for 15 days, 24u2009h daily. Once completed, plasmatic corticosterone (CORT) concentration was quantified, and immunohistochemistry for glial fibrillary acidic protein was taken in hippocampal DG, CA3, and CA1 subareas. Immunopositive cells and astrocyte arborizations were counted and compared between groups. Results: The rats subjected to noise exhibited enlarged length of astrocytes arborizations in all hippocampal subareas. Those changes were accompanied by a marked rise in serum CORT levels. Conclusions: These findings confirm hippocampal vulnerability to EN and suggest that glial cells may play an important role in the adaptation of developing the participants to noise exposure.