Hyperbaric oxygen treatment promotes neural stem cell proliferation in the subventricular zone of neonatal rats with hypoxic-ischemic brain damage

Hyperbaric oxygen therapy for the treatment of neonatal hypoxic-ischemic brain damage has been used clinically for many years, but its effectiveness remains controversial. In addition, the mechanism of this potential neuroprotective effect remains unclear. This study aimed to investigate the influence of hyperbaric oxygen on the proliferation of neural stem cells in the subventricular zone of neonatal Sprague-Dawley rats (7 days old) subjected to hypoxic-ischemic brain damage. Six hours after modeling, rats were treated with hyperbaric oxygen once daily for 7 days. Immunohistochemistry revealed that the number of 5-bromo-2′-deoxyuridine positive and nestin positive cells in the subventricular zone of neonatal rats increased at day 3 after hypoxic-ischemic brain damage and peaked at day 5. After hyperbaric oxygen treatment, the number of 5-bromo-2′- deoxyuridine positive and nestin positive cells began to increase at day 1, and was significantly higher than that in normal rats and model rats until day 21. Hematoxylin-eosin staining showed that hyperbaric oxygen treatment could attenuate pathological changes to brain tissue in neonatal rats, and reduce the number of degenerating and necrotic nerve cells. Our experimental findings indicate that hyperbaric oxygen treatment enhances the proliferation of neural stem cells in the subventricular zone of neonatal rats with hypoxic-ischemic brain damage, and has therapeutic potential for promoting neurological recovery following brain injury.     

Hypoxia/ischemia depletes the rat perinatal subventricular zone of oligodendrocyte progenitors and neural stem cells

Cerebral hypoxia/ischemia of the newborn has a frequency of 4/1,000 births and remains a major cause of cerebral palsy, epilepsy, and mental retardation. Despite progress in understanding the pathogenesis of hypoxic-ischemic injury, the data are incomplete regarding the mechanisms leading to permanent brain injury. Here we tested the hypothesis that cerebral hypoxia/ischemia damages stem/progenitor cells in the subventricular zone (SVZ), resulting in a permanent depletion of oligodendrocytes. We used a widely accepted rat model and examined animals at recovery intervals ranging from 4 h to 3 weeks. Within hours after the hypoxic-ischemic insult 20% of the total cells were deleted from the SVZ. The residual damaged cells appeared necrotic. During 48 h of recovery deaths accumulated; however, these later deaths were predominantly apoptotic. Many apoptotic SVZ cells stained with a marker for immature oligodendrocytes. At 3 weeks survival, the SVZ was smaller and markedly less cellular, and it contained less than 1/4 the normal complement of neural stem cells. The corresponding subcortical white matter was dysmyelinated, relatively devoid of oligodendrocytes and enriched in astrocytes. We conclude that neural stem cells and oligodendrocyte progenitors in the SVZ are vulnerable to hypoxia/ischemia. Consequently, the developmental production of oligodendrocytes is compromised and regeneration of damaged white matter oligodendrocytes does not occur resulting in failed regeneration of CNS myelin in periventricular loci. The resulting dysgenesis of the brain that occurs subsequent to perinatal hypoxic/ischemic injury may contribute to the cognitive and motor dysfunction that results from asphyxia of the newborn.     

Human embryonic neural stem cell transplantation increases subventricular zone cell proliferation and promotes peri‐infarct angiogenesis after focal cerebral ischemia

Neurogenesis and angiogenesis are two important processes that may contribute to the repair of brain injury after stroke. This study was designed to investigate whether transplantation of human embryonic neural stem cells (NSCs) into cortical peri‐infarction 24 h after ischemia effects cell proliferation in the subventricular zone (SVZ) and angiogenesis in the peri‐infarct zone. NSCs were prepared from embryonic human brains at 8 weeks gestation. Focal cerebral ischemia was induced by permanent occlusion of the middle cerebral artery of adult rats. Animals were randomly divided into two groups (n = 30, each) at 24 h after ischemia: NSC‐grafted and medium‐grafted groups. Toluidine blue staining and 5′‐bromo‐2′‐deoxyuridine (BrdU) or von Willebrand factor (vWF) immunohistochemistry were performed at 7, 14 and 28 days after transplantation. NSC transplantation increased the number of BrdU‐positive cells in the ischemic ipsilateral SVZ compared with the medium control at 7 days (P < 0.01). This difference in SVZ cell proliferation persisted at 14 days (P < 0.01), but was not significant at 28 days (P > 0.05). In addition, angiogenesis, as indicated by BrdU and vWF staining in cortical peri‐infarct regions, was augmented by 46% and 65% in NSC‐grafted rats versus medium‐grafted rats at 7 and 14 days, respectively (P < 0.05). However, this increase became non‐significant at 28 days (P > 0.05). Our results indicate that NSC transplantation enhances endogenous cell proliferation in the SVZ and promotes angiogenesis in the peri‐infarct zone, even if it is performed in the acute phase of ischemic injury.     

Age-related proteomic changes in the subventricular zone and their association with neural stem/progenitor cell proliferation

In the mammalian central nervous system, generation of new neurons persists in the subventricular zone (SVZ) throughout life. However, the capacity for neurogenesis in this region declines with aging. Recent studies have examined the degree of these age-related neurogenic declines and the changes of cytoarchitecture of the SVZ with aging. However, little is known about the molecular changes in the SVZ with aging. In this study, we dissected the SVZs from rats aged postnatal day 28, 3 months, and 24 months. The SVZ tissues were processed for 2-D gel electrophoresis to identify protein changes following aging. Protein spots were subsequently subjected to mass spectrometry analysis to compare age-related alterations in the SVZ proteome. We also examined the level of cell proliferation in the SVZ in animals of these three age groups by using bromodeoxyuridine labeling. We found significant age-related changes in the expression of several proteins that play critical roles in the proliferation and survival of neural stem/progenitor cells in the SVZ. Among these proteins, glial fibrillary acidic protein, ubiquitin carboxy terminal hydrolase 1, glutathione S-transferase omega, and preproalbumin were increased with aging, whereas collapsin response-mediated protein 4 (CRMP-4), CRMP-5, and microsomal protease ER60 exhibited declines with aging. We have also observed a significant decline of neural stem/progenitor cell proliferation in the SVZ with aging. These alterations in protein expression in the SVZ with aging likely underlie the diminishing proliferative capacity of stem/progenitor cells in the aging brain.     

Gypenosides pre-treatment protects the brain against cerebral ischemia and increases neural stem cells/progenitors in the subventricular zone

Gypenosides (GPs) have been reported to have neuroprotective effects in addition to other bioactivities. The protective activity of GPs during stroke and their effects on neural stem cells (NSCs) in the ischemic brain have not been fully elucidated. Here, we test the effects of GPs during stroke and on the NSCs within the subventricular zone (SVZ) of middle cerebral artery occlusion (MCAO) rats. Our results show that pre-treatment with GPs can reduce infarct volume and improve motor function following MCAO. Pre-treatment with GPs significantly increased the number of BrdU-positive cells in the ipsilateral and contralateral SVZ of MCAO rats. The proliferating cells in both sides of the SVZ were glial fibrillary acidic protein (GFAP)/nestin-positive type B cells and doublecortin (DCX)/nestin-positive type A cells. Our data indicate that GPs have neuroprotective effects during stroke which might be mediated through the enhancement of neurogenesis within the SVZ. These findings provide new evidence for a potential therapy involving GPs for the treatment of stroke.     

Temporal profile of stem cell division, migration, and differentiation from subventricular zone to olfactory bulb after transient forebrain ischemia in gerbils.

The stage of neurogenesis can be divided into three steps: proliferation, migration, and differentiation. To elucidate their detailed relations after ischemia, the three steps were comprehensively evaluated, in the subventricular zone (SVZ) through the rostral migratory stream (RMS) to the olfactory bulb (OB), in adult gerbil brain after 5 minutes of transient forebrain ischemia. Bromodeoxyuridine (BrdU), highly polysialylated neural cell adhesion molecule (PSA-NCAM), neuronal nuclear antigen (NeuN), and glial fibrillary acidic protein (GFAP) were used as markers for proliferation, migration, and differentiation, respectively. The number of BrdU-labeled cells that coexpressed PSA-NCAM and the size of PSA-NCAM-positive cell colony increased in the SVZ with a peak at 10 d after transient ischemia. In the RMS, the number of BrdU-labeled cells that coexpressed PSA-NCAM increased, with a delayed peak at 30 d, when the size of RMS itself became larger and the number of surrounding GFAP-positive cells increased. In the OB, BrdU + NeuN double positive cells were detected at 30 and 60 d. NeuN staining and terminal deoxynucleotidyl dUTP nick-end labeling staining showed no neuronal cell loss around the SVZ, and in the RMS and the OB after transient ischemia. These findings indicate that transient forebrain ischemia enhances neural stem cell proliferation in the SVZ without evident neuronal cell loss, and has potential neuronal precursor migration with activation of GFAP-positive cells through the RMS to the OB.     

Temporal profile of CREB phosphorylation after focal ischemia in rat brain.

The phosphorylation of cAMP response element binding protein (CREB) in the rat brain was examined immunohistochemically at 3.5 h, 12 h, 24 h and 48 h of recirculation after focal ischemia induced by occlusion of the middle cerebral artery for 1.5 h. Brain sections were stained with affinity purified anti-phosphorylated CREB antibody. The ischemic core revealed a significant, but transient increase in number of phosphorylated CREB-positive cells at 3.5 h of recirculation, followed by a rapid decrease during the subsequent period. In the peri-ischemia area, the number of phosphorylated CREB-positive cells showed a more marked increase as compared to that in the ischemic core at 3.5 h of recirculation, and the increase continued until 48 h of recirculation with a tendency for gradual decline. Persistent enhancement of CREB phosphorylation may thus be closely related to the neuronal viability and neuroprotective mechanisms, whereas rapid disappearance of CREB phosphorylation may clearly precede neuronal death.     

Neural stem cells in the subventricular zone are resilient to hypoxia/ischemia whereas progenitors are vulnerable.

Perinatal hypoxic-ischemic (H/I) brain injury remains a major cause of neurologic disability. Because we have previously demonstrated that this insult depletes cells from the subventricular zone (SVZ), the goal of the present investigation was to compare the relative vulnerability to H/I of neural stem cells versus progenitors. The dorsolateral SVZs of P6 rats were examined at 2 to 48 hours of recovery from H/I using hematoxylin and eosin, in situ end labeling (ISEL), terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate-biotin nick end labeling (TUNEL), electron microscopy, and immunofluorescence. Pyknotic nuclei and ISEL cells were observed by 4 hours of recovery, peaked at 12 hours, and persisted for at least 48 hours. Many active-caspase-3 cells were observed at 12 hours and they comprised one third of the total TUNEL population. Electron microscopy revealed that hybrid cell deaths predominated at 12 hours of recovery. Importantly, few dying cells were observed in the medial SVZ, where putative stem cells reside, and no nestin medial SVZ cells showed caspase-3 activation. By contrast, active-caspase-3/PSA-NCAM progenitors were prominent in the lateral SVZ. These data demonstrate that early progenitors are vulnerable to H/I, whereas neural stem cells are resilient. The demise of these early progenitors may lead to the depletion of neuronal and late oligodendrocyte progenitors, contributing to cerebral dysgenesis after perinatal insults.     

Perinatal hypoxia/ischemia damages and depletes progenitors from the mouse subventricular zone

Hypoxia-ischemia (H/I) as a result of asphyxia at term remains a major cause of neurologic disability. Our previous studies in the P7 rat model of perinatal H/I have shown that progenitors within the subventricular zone (SVZ) are vulnerable to this insult. Since many investigators are using transgenic and knockout mice to determine the importance of specific molecules in the evolution of damage after a stroke, there is a need to perform comparative studies on the relative vulnerability of the mouse SVZ. Here we assess damage to the SVZ of 5-, 7- and 10-day-old C57BL/6 mice after unilateral common carotid artery cauterization followed by 70 min of H/I (10% O2). Whereas 5- and 7-day-old mice sustained little SVZ damage as assessed by hematoxylin and eosin staining, there was a 16% reduction of cellularity in 10-day-old animals by 18 h of recovery. Additionally, swollen cells were observed in the medial region of the SVZ of 10-day-old mice. However, few caspase-3+ and TUNEL+ cells were observed in this region, which contains the putative neural stem cells. Rather, the majority of the dying cells were situated in the mediolateral and lateral tail of the SVZ. At 18 h of recovery, there was a 2-fold increase in the frequency of TUNEL+ cells in the ipsilateral SVZ as well as a 3-fold increase in the frequency of active-caspase-3+ cells. We conclude that progenitors within the neonatal mouse SVZ are vulnerable to hypoxic/ischemic insult. The demise of these early progenitors likely leads to depletion of neuronal and late oligodendrocyte progenitors, contributing to cerebral dysgenesis.     

Unmasking the responses of the stem cells and progenitors in the subventricular zone after neonatal and pediatric brain injuries

There is great interest in the regenerative potential of the neural stem cells and progenitors that populate the subventricular zone (SVZ). However, a comprehensive understanding of SVZ cell responses to brain in-juries has been hindered by the lack of sensitive approaches to study the cellular composition of this niche. Here we review progress being made in deciphering the cells of the SVZ gleaned from the use of a recently designed lfow cytometry panel that allows SVZ cells to be parsed into multiple subsets of progenitors as well as putative stem cells. We review how this approach has begun to unmask both the heterogeneity of SVZ cells as well as the dynamic shifts in cell populations with neonatal and pediatric brain injuries. We also discuss how lfow cytometric analyses also have begun to reveal how speciifc cytokines, such as Leuke-mia inhibitory factor are coordinating SVZ responses to injury.     

Effect of Angelica sinensis on neural stem cell proliferation in neonatal rats following intrauterine hypoxia

BACKGROUND:Angelica sinensis is a widely used herb in Chinese traditional medicine.It has been shown to improve hypoxia in embryonic rats and reduce nestin expression in neural stem cells,resulting in proliferation of neural stem cells.OBJECTIVE:To study the protective effect of Angelica on neural stem cell proliferation in neonatal rats after intrauterine hypoxia.DESIGN,TIME AND SETTING:The randomized,controlled,experiment was performed at the Department of Histology and Embryology,Luzhou Medical College,China from July 2007 to January 2008.MATERIALS:Because gestational days 14-15 are a key stage in rat nervous system development,21 healthy,pregnant Sprague Dawley rats(14 days after conception)were used for this study.Nestin monoclonal primary antibody was obtained from Chemicon,USA.Angelica parenteral solution(250 g/L)was obtained from Pharmaceutical Preparation Section,Second Affiliated Hospital of Wuhan University,China.METHODS:Rats were randomly divided into a control group(n=5),a hypoxia group(n=8),and an Angelica group(n=8).Saline(8 mL/kg)was injected into the caudal vein of rats in the hypoxia group once a day for seven consecutive days.Intrauterine hypotonic hypoxia was induced using 13% O2 for two hours per day on three consecutive days.Rats in the Angelica group received injections of Angelica parenteral solution(250 g/L);all other protocols were the same as the hypoxia group.The control group procedures were identical to the hypoxia group,but under normal,non-hypoxic conditions.After birth,brain tissues were immediately obtained from neonatal rats and prepared for nestin immunohistochemistry.MAIN OUTCOME MEASURES:Nestin-positive cells in hippocampal CA3 area of neonatal rats in each group were quantified using image analysis to detect signal absorbance.RESULTS:The number of nestin-positive cells increased in the hippocampal CA3 area of neonatal rats in the hypoxia group.The number of nestin-positive cells was less in the Angelica group than in the hypoxia group.Integral absorbance of nestin-positive cells in the hippocampal CA3 area of neonatal rats was significantly higher in the hypoxia group,compared with the control group(P<0.05).The integral absorbance of nestin positive cells was lower in the Angelica group,compared with the hypoxia group(P<0.05).CONCLUSION:Intrauterine hypoxia,induced for 2 hours daily for three consecutive days,with an oxygen concentration of 13%,stimulated the proliferation of neural stem cells.Angelica injection has a protective effect on neural stem cells from neonatal rats following intrauterine hypoxia by decreasing proliferation of neural stem cells.     

Effect of Angelica sinensis on neural stem cell proliferation in neonatal rats following intrauterine hypoxia★

BACKGROUND： Angelica sinensis is a widely used herb in Chinese traditional medicine. It has been shown to improve hypoxia in embryonic rats and reduce nestin expression in neural stem cells, resulting in proliferation of neural stem cells.
OBJECTIVE： To study the protective effect of Angelica on neural stem cell proliferation in neonatal rats after intrauterine hypoxia.
DESIGN, TIME AND SETTING： The randomized, controlled, experiment was performed at the Department of Histology and Embryology, Luzhou Medical College, China from July 2007 to January 2008.
MATERIALS： Because gestational days 14-15 are a key stage in rat nervous system development, 21 healthy, pregnant Sprague Dawley rats （14 days after conception） were used for this study. Nestin monoclonal primary antibody was obtained from Chemicon, USA. Angelica parenteral solution （250 g/L） was obtained from Pharmaceutical Preparation Section, Second Affiliated Hospital of Wuhan University, China.
METHODS： Rats were randomly divided into a control group （n = 5）, a hypoxia group （n = 8）, and an Angelica group （n = 8）. Saline （8 mL/kg） was injected into the caudal vein of rats in the hypoxia group once a day for seven consecutive days. Intrauterine hypotonic hypoxia was induced using 13% O2 for two hours per day on three consecutive days. Rats in the Angelica group received injections of Angelica parenteral solution （250 g/L）; all other protocols were the same as the hypoxia group. The control group procedures were identical to the hypoxia group, but under normal, non-hypoxic conditions. After birth, brain tissues were immediately obtained from neonatal rats and prepared for nestin immunohistochemistry.
MAIN OUTCOME MEASURES： Nestin-positive cells in hippocampal CA3 area of neonatal rats in each group were quantified using image analysis to detect signal absorbance.
RESULTS： The number of nestin-positive cells increased in the hippocampal CA3 area of neonatal rats in the hypoxia group. The number of nestin-pos     

Fibroblast growth factor 2 is required for maintaining the neural stem cell pool in the mouse brain subventricular zone

Cells within the subventricular zone (SVZ) express basic Fgf (Fgf2) and Fgf receptor proteins. We show that the absence of Fgf2 gene products reduces by 50% the dividing progenitor population of the anterior SVZ (SVZa) without changing their cell cycle time. Every 2-3 cell cycles of the SVZa progenitor cell population, 30,000 newly generated neurons capable of long-term survival are added to the glomerular layer of the olfactory bulb. Fgf2 knockout mice have smaller olfactory bulbs due to decreased output of these newly generated cells into the bulbs. A population of slow-dividing neural stem cells (NSCs) residing in the SVZa is identified by its slow cell cycle kinetics (cell cycle approx. 20 days); these cells, called 'S' cells, are negative for glial fibrillary acidic protein and occasionally express brain-lipid-binding protein, a molecular marker of radial glia. The number of these dividing NSCs is reduced from about 13,000 in wild-type to 8,500 cells in Fgf2 knockout mice. Thus, FGF2 regulates the number of proliferative cells and olfactory bulb neurogenesis by maintaining a slow-dividing stem cell pool within the SVZa.     

Ampakine CX546 increases proliferation and neuronal differentiation in subventricular zone stem/progenitor cell cultures

Ampakines are chemical compounds known to modulate the properties of ionotropic α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA)-subtype glutamate receptors. The functional effects attributed to ampakines involve plasticity and the increase in synaptic efficiency of neuronal circuits, a process that may be intimately associated with differentiation of newborn neurons. The subventricular zone (SVZ) is the main neurogenic niche of the brain, containing neural stem cells with brain repair potential. Accordingly, the identification of new pharmaceutical compounds with neurogenesis-enhancing properties is important as a tool to promote neuronal replacement based on the use of SVZ cells. The purpose of the present paper is to examine the possible proneurogenic effects of ampakine CX546 in cell cultures derived from the SVZ of early postnatal mice. We observed that CX546 (50 μm) treatment triggered an increase in proliferation, evaluated by BrdU incorporation assay, in the neuroblast lineage. Moreover, by using a cell viability assay (TUNEL) we found that, in contrast to AMPA, CX546 did not cause cell death. Also, both AMPA and CX546 stimulated neuronal differentiation as evaluated morphologically through neuronal nuclear protein (NeuN) immunocytochemistry and functionally by single-cell calcium imaging. Accordingly, short exposure to CX546 increased axonogenesis, as determined by the number and length of tau-positive axons co-labelled for the phosphorylated form of SAPK/JNK (P-JNK), and dendritogenesis (MAP2-positive neurites). Altogether, this study shows that ampakine CX546 promotes neurogenesis in SVZ cell cultures and thereby may have potential for future stem cell-based therapies.     

19-Nortestosterone influences neural stem cell proliferation and neurogenesis in the rat brain

Abuse of androgenic anabolic steroids can affect brain function leading to behavioural changes. In this study, the effects of the testosterone analogue, 19-nortestosterone, on rat neural stem cells was examined. The androgen receptor is expressed by cultured embryonic and adult neural stem cells, and is also present in the ventricular epithelium during development and in the adult brain in, among others, dentate gyrus. In neural stem cells stimulated with epidermal growth factor, nandrolone reduced cell proliferation, especially in adult ones. The decrease was abolished by flutamide, a receptor antagonist. Nandrolone also decreased the BrdU labelling of neural stem cells in the dentate gyrus, demonstrating an effect of the hormone on cell proliferation in vivo. The effect of nandrolone was observed with both female and male rats but it was more pronounced in pregnant rats, indicating an involvement of oestrogen in nandrolone action. Nandrolone also decreased the number of newly born neuronal cells in the dentate gyrus of male rats. The results show that nandrolone has important effects on the proliferation and differentiation of neural stem cells expressing the cognate androgen receptor. The data show that the use of nandrolone may severely affect the formation of neural stem cells and could therefore have long-term negative consequences in the brain.     

新生大鼠海马区及室管膜下区神经干细胞分离、培养和分化特性

目的建立大鼠神经干细胞（NSCs）分离、培养方法，观察其生长、增殖和分化特点。方法利用无血清培养技术，从新生大鼠海马、室管膜下区分离NSCs，进行体外扩增培养、传代观察。采用荧光免疫细胞化学检测技术，观察鉴定NSCs及其分化结果。结果分离获取的细胞具有自我更新和增殖能力，原代及传代培养均可形成细胞克隆，克隆中的细胞巢蛋白（nestin）表达阳性，显微镜下观察见典型的干细胞特征，诱导后可分化神经元和星形胶质细胞。结论上法分离培养的细胞为具有自我更新和增殖能力的NSCs，可诱导分化为终末神经细胞。     

Temporal profile of neurogenesis in the subventricular zone,dentate gyrus and cerebral cortex following transient focal cerebral ischemia

Abstract

Background: In the adult mammalian brain, it is considered that neurogenesis persists in limited regions such as the hippocampal dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricle. On the other hand, neurogenesis in the cortex after cerebral ischemia and its role in post-stroke recovery have not been clarified yet. In this study, we investigated neurogenesis in the cortex and the spatiotemporal profile of neural progenitors in SVZ and DG of rats subjected to transient focal cerebral ischemia.

Materials and methods: Male Sprague–Dawley rats (270–300 g) were subjected to 60 minute middle cerebral artery occlusion. Proliferating cells were labeled by the cumulative administration of BrdU 1, 2, 3, 4, 6 and 8 weeks after ischemia induction (at weeks 1–4, 6 and 8). Double labeling was also performed with antibodies against BrdU and NeuN.

Results: BrdU-positive cells proliferated in DG and SVZ of the bilateral hemispheres, and their proliferation peaked at week 3 in SVZ and at week 4 in DG. In the peri-infarct zone of cerebral cortex, BrdU-positive cells co-expressed NeuN from weeks 3 to 8.

Conclusion: Neurogenesis was observed in the cerebral cortex and proliferation of neural progenitors occurred in SVZ and DG of rats subjected to transient focal cerebral ischemia. Our data might indicate that endogenous dormant neural stem cells residing in the cortex were activated by ischemic insult to induce the proliferation of neural progenitors and differentiation into mature neurons.     

Controlling neural stem cell division within the adult subventricular zone: an APPealing job

For years, scientists investigating amyloid precursor protein (APP) have focused on its pathogenetic role in the brains of Alzheimer's disease patients. Now, a study by Caille et al. adds new sites of action and new physiological functions for APP. They show that there are binding sites for secreted N-terminal nonamyloidogenic APP (sAPP) on epidermal growth factor (EGF)-responsive neural stem cells in the subventricular zone of the adult brain, where sAPP acts as an EGF cofactor to stimulate proliferation of these cells. This result opens the hypothesis that changes in the levels of sAPP could influence activity of the neurogenic regions of the adult brain in normal and pathological conditions.     

Structural remodeling of gray matter astrocytes in the neonatal pig brain after hypoxia/ischemia

Astrocytes play a vital role in the brain; their structural integrity and sustained function are essential for neuronal viability, especially after injury or insult. In this study, we have examined the response of astrocytes to hypoxia/ischemia (H/I), employing multiple methods (immunohistochemistry, iontophoretic cell injection, Golgi‐Kopsch staining, and D ‐aspartate uptake) in a neonatal pig model of H/I. We have identified morphological changes in cortical gray matter astrocytes in response to H/I. Initial astrocytic changes were evident as early as 8 h post‐insult, before histological evidence for neuronal damage. By 72 h post‐insult, astrocytes exhibited significantly fewer processes that were shorter, thicker, and had abnormal terminal swellings, compared with astrocytes from control brains that exhibited a complex structure with multiple fine branching processes. Quantification and image analysis of astrocytes at 72 h post‐insult revealed significant decreases in the average astrocyte size, from 686 μm² in controls to 401 μm² in H/I brains. Sholl analysis revealed a significant decrease (>60%) in the complexity of astrocyte branching between 5 and 20 μm from the cell body. D ‐Aspartate uptake studies revealed that the H/I insult resulted in impaired astrocyte function, with significantly reduced clearance of the glutamate analog, D ‐aspartate. These results suggest that astrocytes may be involved in the pathophysiological events of H/I brain damage at a far earlier time point than first thought. Developing therapies that prevent or reverse these astrocytic changes may potentially improve neuronal survival and thus might be a useful strategy to minimize brain damage after an H/I insult. © 2009 Wiley‐Liss, Inc.