Author
Xiao Ou Mao
Bio: Xiao Ou Mao is an academic researcher from Buck Institute for Research on Aging. The author has contributed to research in topics: Neurogenesis & Subventricular zone. The author has an hindex of 50, co-authored 70 publications receiving 13133 citations.
Papers published on a yearly basis
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TL;DR: Findings implicate the angiogenesis factor VEGF in neurogenesis as well in murine cerebral cortical cultures and in adult rat brain in vivo.
Abstract: Vascular endothelial growth factor (VEGF) is an angiogenic protein with neurotrophic and neuroprotective effects. Because VEGF promotes the proliferation of vascular endothelial cells, we examined the possibility that it also stimulates the proliferation of neuronal precursors in murine cerebral cortical cultures and in adult rat brain in vivo. VEGF (>10 ng/ml) stimulated 5-bromo-2'-deoxyuridine (BrdUrd) incorporation into cells that expressed immature neuronal marker proteins and increased cell number in cultures by 20-30%. Cultured cells labeled by BrdUrd expressed VEGFR2/Flk-1, but not VEGFR1/Flt-1 receptors, and the effect of VEGF was blocked by the VEGFR2/Flk-1 receptor tyrosine kinase inhibitor SU1498. Intracerebroventricular administration of VEGF into rat brain increased BrdUrd labeling of cells in the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampal dentate gyrus (DG), where VEGFR2/Flk-1 was colocalized with the immature neuronal marker, doublecortin (Dcx). The increase in BrdUrd labeling after the administration of VEGF was caused by an increase in cell proliferation, rather than a decrease in cell death, because VEGF did not reduce caspase-3 cleavage in SVZ or SGZ. Cells labeled with BrdUrd after VEGF treatment in vivo include immature and mature neurons, astroglia, and endothelial cells. These findings implicate the angiogenesis factor VEGF in neurogenesis as well.
1,472 citations
TL;DR: In the ischemic brain VEGF exerts an acute neuroprotective effect, as well as longer latency effects on survival of new neurons and on angiogenesis, and that these effects appear to operate independently.
Abstract: Vascular endothelial growth factor (VEGF) is an angiogenic protein with therapeutic potential in ischemic disorders, including stroke. VEGF confers neuroprotection and promotes neurogenesis and cerebral angiogenesis, but the manner in which these effects may interact in the ischemic brain is poorly understood. We produced focal cerebral ischemia by middle cerebral artery occlusion for 90 minutes in the adult rat brain and measured infarct size, neurological function, BrdU labeling of neuroproliferative zones, and vWF-immunoreactive vascular profiles, without and with intracerebroventricular administration of VEGF on days 1-3 of reperfusion. VEGF reduced infarct size, improved neurological performance, enhanced the delayed survival of newborn neurons in the dentate gyrus and subventricular zone, and stimulated angiogenesis in the striatal ischemic penumbra, but not the dentate gyrus. We conclude that in the ischemic brain VEGF exerts an acute neuroprotective effect, as well as longer latency effects on survival of new neurons and on angiogenesis, and that these effects appear to operate independently. VEGF may, therefore, improve histological and functional outcome from stroke through multiple mechanisms.
1,099 citations
TL;DR: A role for ischemia-induced neurogenesis in what may be adaptive processes that contribute to recovery after stroke is supported.
Abstract: Because neurogenesis persists in the adult mammalian brain and can be regulated by physiological and pathological events, we investigated its possible involvement in the brain's response to focal cerebral ischemia. Ischemia was induced by occlusion of the middle cerebral artery in the rat for 90 min, and proliferating cells were labeled with 5-bromo-2'-deoxyuridine-5'-monophosphate (BrdUrd) over 2-day periods before sacrificing animals 1, 2 or 3 weeks after ischemia. Ischemia increased the incorporation of BrdUrd into cells in two neuroproliferative regions-the subgranular zone of the dentate gyrus and the rostral subventricular zone. Both effects were bilateral, but that in the subgranular zone was more prominent on the ischemic side. Cells labeled with BrdUrd coexpressed the immature neuronal markers doublecortin and proliferating cell nuclear antigen but did not express the more mature cell markers NeuN and Hu, suggesting that they were nascent neurons. These results support a role for ischemia-induced neurogenesis in what may be adaptive processes that contribute to recovery after stroke.
1,074 citations
TL;DR: It is suggested that neurogenesis is increased in AD hippocampus, where it may give rise to cells that replace neurons lost in the disease, and that stimulating hippocampal neuroGenesis might provide a new treatment strategy.
Abstract: Neurogenesis, which persists in the adult mammalian brain, may provide a basis for neuronal replacement therapy in neurodegenerative diseases like Alzheimer's disease (AD). Neurogenesis is increased in certain acute neurological disorders, such as ischemia and epilepsy, but the effect of more chronic neurodegenerations is uncertain, and some animal models of AD show impaired neurogenesis. To determine how neurogenesis is affected in the brains of patients with AD, we investigated the expression of immature neuronal marker proteins that signal the birth of new neurons in the hippocampus of AD patients. Compared to controls, Alzheimer's brains showed increased expression of doublecortin, polysialylated nerve cell adhesion molecule, neurogenic differentiation factor and TUC-4. Expression of doublecortin and TUC-4 was associated with neurons in the neuroproliferative (subgranular) zone of the dentate gyrus, the physiological destination of these neurons (granule cell layer), and the CA1 region of Ammon's horn, which is the principal site of hippocampal pathology in AD. These findings suggest that neurogenesis is increased in AD hippocampus, where it may give rise to cells that replace neurons lost in the disease, and that stimulating hippocampal neurogenesis might provide a new treatment strategy.
981 citations
TL;DR: In HN33, an immortalized hippocampal neuronal cell line, VEGF reduced cell death associated with an in vitro model of cerebral ischemia: at a maximally effective concentration of 50 ng/ml, V EGF approximately doubled the number of cells surviving after 24 h of hypoxia and glucose deprivation.
Abstract: Vascular endothelial growth factor (VEGF) is a hypoxia-inducible angiogenic peptide with recently identified neurotrophic effects. Because some neurotrophic factors can protect neurons from hypoxic or ischemic injury, we investigated the possibility that VEGF has similar neuroprotective properties. In HN33, an immortalized hippocampal neuronal cell line, VEGF reduced cell death associated with an in vitro model of cerebral ischemia: at a maximally effective concentration of 50 ng/ml, VEGF approximately doubled the number of cells surviving after 24 h of hypoxia and glucose deprivation. To investigate the mechanism of neuroprotection by VEGF, the expression of known target receptors for VEGF was measured by Western blotting, which showed that HN33 cells expressed VEGFR-2 receptors and neuropilin-1, but not VEGFR-1 receptors. The neuropilin-1 ligand placenta growth factor-2 failed to reproduce the protective effect of VEGF, pointing to VEGFR-2 as the site of VEGF's neuroprotective action. Two phosphatidylinositol 3′-kinase inhibitors, wortmannin and LY294002, reversed the neuroprotective effect of VEGF, implicating the phosphatidylinositol 3′-kinase/Akt signal transduction system in VEGF-mediated neuroprotection. VEGF also protected primary cultures of rat cerebral cortical neurons from hypoxia and glucose deprivation. We conclude that in addition to its known role as an angiogenic factor, VEGF may exert a direct neuroprotective effect in hypoxic-ischemic injury.
675 citations
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TL;DR: Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models and is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.
Abstract: Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. Hypoxia has been shown to be a major inducer of VEGF gene transcription. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high-affinity VEGF receptors. The role of VEGF in developmental angiogenesis is emphasized by the finding that loss of a single VEGF allele results in defective vascularization and early embryonic lethality. VEGF is critical also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with various VEGF inhibitors in a variety of malignancies are ongoing. Very recently, an anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the Food and Drug Administration as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.
3,414 citations
TL;DR: Analysis of preclinical cellular and behavioral models of depression and antidepressant actions, as well as clinical neuroimaging and postmortem studies, are consistent with the hypothesis that decreased expression of BDNF and possibly other growth factors contributes to depression and that upregulation ofBDNF plays a role in the actions of antidepressant treatment.
2,999 citations
TL;DR: The factors that regulate proliferation and fate determination of adult neural stem cells are discussed and the potential significance of adult neurogenesis in memory, depression, and neurodegenerative disorders such as Alzheimer's and Parkinson's disease is addressed.
2,911 citations
TL;DR: The mechanism of mitochondrial RIRR highlights the central role of mitochondria-formed ROS, and all of the known ROS-producing sites and their relevance to the mitochondrial ROS production in vivo are discussed.
Abstract: Byproducts of normal mitochondrial metabolism and homeostasis include the buildup of potentially damaging levels of reactive oxygen species (ROS), Ca2+, etc., which must be normalized. Evidence suggests that brief mitochondrial permeability transition pore (mPTP) openings play an important physiological role maintaining healthy mitochondria homeostasis. Adaptive and maladaptive responses to redox stress may involve mitochondrial channels such as mPTP and inner membrane anion channel (IMAC). Their activation causes intra- and intermitochondrial redox-environment changes leading to ROS release. This regenerative cycle of mitochondrial ROS formation and release was named ROS-induced ROS release (RIRR). Brief, reversible mPTP opening-associated ROS release apparently constitutes an adaptive housekeeping function by the timely release from mitochondria of accumulated potentially toxic levels of ROS (and Ca2+). At higher ROS levels, longer mPTP openings may release a ROS burst leading to destruction of mitochondria, and if propagated from mitochondrion to mitochondrion, of the cell itself. The destructive function of RIRR may serve a physiological role by removal of unwanted cells or damaged mitochondria, or cause the pathological elimination of vital and essential mitochondria and cells. The adaptive release of sufficient ROS into the vicinity of mitochondria may also activate local pools of redox-sensitive enzymes involved in protective signaling pathways that limit ischemic damage to mitochondria and cells in that area. Maladaptive mPTP- or IMAC-related RIRR may also be playing a role in aging. Because the mechanism of mitochondrial RIRR highlights the central role of mitochondria-formed ROS, we discuss all of the known ROS-producing sites (shown in vitro) and their relevance to the mitochondrial ROS production in vivo.
2,893 citations
TL;DR: Previously undescribed prognostic subclasses of high-grade astrocytoma are identified and discovered to resemble stages in neurogenesis, suggesting functional relevance of tumor subtype molecular signatures is suggested by the ability of cell line signatures to predict neurosphere growth.
2,840 citations