Basic fibroblast growth factor and fibroblast growth factor receptor-1 in the human hippocampal formation

Localization of fibroblast growth factor 23 protein in the rat hypothalamus

Fibroblast growth factor 23 (FGF23) is an endocrine growth factor and known to play a pivotal role in phosphate homeostasis. Interestingly, several studies point towards a function of FGF23 in the hypothalamus. FGF23 classically activates the FGF receptor 1 in the presence of the co-receptor αKlotho, of both gene expression in the brain was previously established. However, studies on gene and protein expression of FGF23 in the brain are scarce and have been inconsistent. Therefore, our aim was to localise FGF23 gene and protein expression in the rat brain with focus on the hypothalamus. Also, we investigated the protein expression of αKlotho. Adult rat brains were used to localise and visualise FGF23 and αKlotho protein in the hypothalamus by immunofluorescence labelling. Furthermore, western blots were used for assessing hypothalamic FGF23 protein expression. FGF23 gene expression was investigated by qPCR in punches of the arcuate nucleus, lateral hypothalamus, paraventricular nucleus, choroid plexus, ventrolateral thalamic nucleus and the ventromedial hypothalamus. Immunoreactivity for FGF23 and αKlotho protein was found in the hypothalamus, third ventricle lining and the choroid plexus. Western blot analysis of the hypothalamus confirmed the presence of FGF23. Gene expression of FGF23 was not detected, suggesting that the observed FGF23 protein is not brain-derived. Several FGF receptors are known to be present in the brain. Therefore, we conclude that the machinery for FGF23 signal transduction is present in several brain areas, indeed suggesting a role for FGF23 in the brain.

Electroacupuncture alleviated the depression-like behavior by regulating FGF2 and astrocytes in the hippocampus of rats with chronic unpredictable mild stress

Studies have shown that basic fibroblast growth factor (FGF2) is a neurotrophic factor associated with depression. Electroacupuncture (EA) has been shown to be an effective treatment for depression. In the current study, we observed the effects of EA on hippocampal FGF2 and astrocytes, and further investigated the mechanism underlying antidepressant effect of EA. The chronic unpredictable mild stress (CUMS) method were selected to induce depressive-like behaviors of rats. Paroxetine is a commonly used antidepressant and was used as a positive control drug in this experiment. The male adult Sprague Dawley (SD) rats were randomized to four experimental groups (normal control group, CUMS group, EA group and paroxetine group, n = 10/group). EA intervention was administered once daily for 14 days at acupuncture points Baihui (GV20) and Yintang (GV29). Rats in the paroxetine group received daily paroxetine administered intragastrical. Behavioral test, immunohistochemistry (IHC), western blot (WB) and quantitative real-time PCR (qPCR) were conducted to evaluate the intervene effect and the changes of FGF2 and astrocyte marker (glial fibrillary acidic protein, GFAP). The results showed that EA and paroxetine could improve depression-like behavior in CUMS rats, and up-regulated the expression level of FGF2 in the hippocampus, increased GFAP protein expression and the mean optical density of GFAP-immunoreactive astrocyte (GFAP-ir astrocyte). Our findings have identified that EA could ameliorate depressive-like behaviors possibly by regulating the expression of FGF2 in the hippocampus, and the mechanism might be related to the effect of FGF2 on astrocytes.

Existence of FGFR1-5-HT1AR heteroreceptor complexes in hippocampal astrocytes. Putative link to 5-HT and FGF2 modulation of hippocampal gamma oscillations

The majority of the fibroblast growth factor receptor 1-serotonin 1 A receptor (FGFR1-5-HT1AR) heterocomplexes in the hippocampus appeared to be located mainly in the neuronal networks and a relevant target for antidepressant drugs. Through a neurochemical and electrophysiological analysis it was therefore tested in the current study if astrocytic FGFR1-5-HT1AR heterocomplexes also exist in hippocampus. They may modulate the structure and function of astroglia in the hippocampus leading to possible changes in the gamma oscillations. Localization of hippocampal FGFR1-5-HT1AR heterocomplexes in astrocytes was found using in situ proximity ligation assay combined with immunohistochemistry using glial fibrillary acidic protein (GFAP) immunoreactivity as a marker for astroglia. Acute i.c.v. treatment with 8-OH-DPAT alone or together with basic fibroblast growth factor (FGF2) significantly increased FGFR1-5-HT1AR heterocomplexes in the GFAP positive cells, especially in the polymorphic layer of the dentate gyrus (PoDG) but also in the CA3 area upon combined treatment. No other hippocampal regions were studied. Also, structural plasticity changes were observed in the astrocytes, especially in the PoDG region, upon these pharmacological treatments. They may also be of relevance for enhancing the astroglial volume transmission with increased modulation of the neuronal networks in the regions studied. The effects of combined FGF2 and 5-HT agonist treatments on gamma oscillations point to a significant antagonistic interaction in astroglial FGFR1-5-HT1AR heterocomplexes that may contribute to counteraction of the 5-HT1AR-mediated decrease of gamma oscillations. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.

Fibroblast Growth Factor 2-Mediated Regulation of Neuronal Exosome Release Depends on VAMP3/Cellubrevin in Hippocampal Neurons

Extracellular vesicles (EVs) are endogenous membrane-derived vesicles that shuttle bioactive molecules between glia and neurons, thereby promoting neuronal survival and plasticity in the central nervous system (CNS) and contributing to neurodegenerative conditions. Although EVs hold great potential as CNS theranostic nanocarriers, the specific molecular factors that regulate neuronal EV uptake and release are currently unknown. A combination of patch-clamp electrophysiology and pH-sensitive dye imaging is used to examine stimulus-evoked EV release in individual neurons in real time. Whereas spontaneous electrical activity and the application of a high-frequency stimulus induce a slow and prolonged fusion of multivesicular bodies (MVBs) with the plasma membrane (PM) in a subset of cells, the neurotrophic factor basic fibroblast growth factor (bFGF) greatly increases the rate of stimulus-evoked MVB-PM fusion events and, consequently, the abundance of EVs in the culture medium. Proteomic analysis of neuronal EVs demonstrates bFGF increases the abundance of the v-SNARE vesicle-associated membrane protein 3 (VAMP3, cellubrevin) on EVs. Conversely, knocking-down VAMP3 in cultured neurons attenuates the effect of bFGF on EV release. The results determine the temporal characteristics of MVB-PM fusion in hippocampal neurons and reveal a new function for bFGF signaling in controlling neuronal EV release.

Low and High Molecular Weight FGF-2 Have Differential Effects on Astrocyte Proliferation, but Are Both Protective Against Aβ-Induced Cytotoxicity

Astrocytes are the most abundant type of glial cells in the brain, and they play a key role in Alzheimer’s disease (AD). Fibroblast Growth Factor-2 (FGF-2) has been implicated as a potential therapeutic agent for treating AD. In the present study, we investigated the protective effects of low molecular weight (LMW; 17 KDa) and high molecular weight (HMW; 23 KDa) forms of FGF-2 on Aβ_1–42-induced toxicity, and proliferation in astrocytes. We show that both isoforms of FGF-2 have similar protective effects against Aβ_1–42-induced cytotoxicity in primary cultured cortical astrocytes as measured by Lactate Dehydrogenase (LDH) release assay. Additionally, 17 KDa FGF-2 significantly promoted astrocyte proliferation as measured by Trypan Blue, DRAQ5 and 5-ethynyl-2’-deoxyuridine (EdU) staining, but not 23 kDa FGF-2. Furthermore, our results demonstrated that AKT signaling pathway was required for the protective and proliferative effects of FGF-2. Downstream effector studies indicated that 17 kDa FGF-2 promoted astrocyte proliferation by enhanced expression of c-Myc, Cyclin D1, Cyclin E. Furthermore, our data suggested that Cyclin D1 was required for the proliferative effect of LMW FGF2 in astrocytes. Taken together, our findings provide important information for the similarities and differences between 23 kDa and17 kDa isoforms of FGF-2 on astrocyte survival and proliferation.

Important unanswered questions about adult neurogenesis in schizophrenia

PURPOSE OF REVIEW

Aberrant neurogenesis may contribute to the pathogenesis, pathophysiology and symptoms of schizophrenia. This review summarizes the state of knowledge of adult neurogenesis in schizophrenia and raises important unanswered questions. We highlight how alterations in signalling molecules in the local and peripheral environments in schizophrenia may regulate adult neurogenesis in the human subgranular zone of the hippocampus and the subependymal zone (SEZ).

RECENT FINDINGS

Cell proliferation and density of mature neurons are reduced in the hippocampus, yet the extent of adult neurogenesis remains unexplored in the SEZ in schizophrenia. The human SEZ is a major source of postnatally migrating cortical and striatal inhibitory interneurons, indicating that aberrant neurogenesis may extend to the SEZ and contribute to inhibitory interneuron deficits in schizophrenia. Trophic factors and inflammatory cytokines regulate the generation of new neurons in rodents, suggesting that altered expression of these signalling molecules in the brain, peripheral vasculature and cerebrospinal fluid in schizophrenia may impact adult neurogenesis in both the hippocampus and the SEZ.

SUMMARY

Knowledge about adult neurogenesis remains scant in schizophrenia. We propose that a more rigorous examination of adult neurogenesis in relation to regulatory signalling molecules will allow us to identify how abnormalities may contribute to the pathophysiology of schizophrenia.

Vascular pattern of the dentate gyrus is regulated by neural progenitors

Neurogenesis is a vital process that begins during early embryonic development and continues until adulthood, though in the latter case, it is restricted to the subventricular zone and the subgranular zone of the dentate gyrus (DG). In particular, the DG's neurogenic properties are structurally and functionally unique, which may be related to its singular vascular pattern. Neurogenesis and angiogenesis share molecular signals and act synergistically, supporting the concept of a neurogenic niche as a functional unit between neural precursors cells and their environment, in which the blood vessels play an important role. Whereas it is well known that vascular development controls neural proliferation in the embryonary and in the adult brain, by releasing neurotrophic factors; the potential influence of neural cells on vascular components during angiogenesis is largely unknown. We have demonstrated that the reduction of neural progenitors leads to a significant impairment of vascular development. Since VEGF is a potential regulator in the neurogenesis-angiogenesis crosstalk, we were interested in assessing the possible role of this molecule in the hippocampal neurovascular development. Our results showed that VEGF is the molecule involved in the regulation of vascular development by neural progenitor cells in the DG.

FGF2 Attenuates Neural Cell Death via Suppressing Autophagy after Rat Mild Traumatic Brain Injury

Traumatic brain injury (TBI) can lead to physical and cognitive deficits, which are caused by the secondary injury process. Effective pharmacotherapies for TBI patients are still lacking. Fibroblast growth factor-2 (FGF2) is an important neurotrophic factor that can stimulate neurogenesis and angiogenesis and has been shown to have neuroprotective effects after brain insults. Previous studies indicated that FGF2's neuroprotective effects might be related to its function of regulating autophagy. The present study investigated FGF2's beneficial effects in the early stage of rat mild TBI and the underlying mechanisms. One hundred and forty-four rats were used for creating controlled cortical impact (CCI) models to simulate the pathological damage after TBI. Our results indicated that pretreatment of FGF2 played a neuroprotective role in the early stage of rat mild TBI through alleviating brain edema, reducing neurological deficits, preventing tissue loss, and increasing the number of surviving neurons in injured cortex and the ipsilateral hippocampus. FGF2 could also protect cells from various forms of death such as apoptosis or necrosis through inhibition of autophagy. Finally, autophagy activator rapamycin could abolish the protective effects of FGF2. This study extended our understanding of FGF2's neuroprotective effects and shed lights on the pharmacological therapy after TBI.

Decreased serum fibroblast growth factor - 2 levels in pre- and post-treatment patients with major depressive disorder

Increasing evidence indicates that neurotrophic factor dysfunction might be involved in the pathophysiology and treatment of major depressive disorder (MDD). Fibroblast growth factor (FGF)-2, one of the major neurotrophins, plays an important role in the central nervous system (CNS). The aim of this study was to explore whether the FGF-2 in serum was associated with MDD and to evaluate the effects of antidepressant treatment on serum FGF-2 levels. Serum FGF-2 levels were determined in 28 pre- and post-treatment MDD patients and 30 healthy controls using ELISA. The results of the current study revealed that serum FGF-2 levels in MDD patients were significantly lower than those in healthy controls (p=0.005), and the serum FGF-2 levels decreased significantly but marginally following treatment for 8 weeks (p=0.005). These findings demonstrate that the lower serum FGF-2 levels contribute to the pathophysiology of MDD and that FGF-2 may be used as a peripheral biological marker for MDD.

Receptor tyrosine kinase (RTK) signalling in the control of neural stem and progenitor cell (NSPC) development

Important developmental responses are elicited in neural stem and progenitor cells (NSPC) by activation of the receptor tyrosine kinases (RTK), including the fibroblast growth factor receptors, epidermal growth factor receptor, platelet-derived growth factor receptors and insulin-like growth factor receptor (IGF1R). Signalling through these RTK is necessary and sufficient for driving a number of developmental processes in the central nervous system. Within each of the four RTK families discussed here, receptors are activated by sets of ligands that do not cross-activate receptors of the other three families, and therefore, their activation can be independently regulated by ligand availability. These RTK pathways converge on a conserved core of signalling molecules, but differences between the receptors in utilisation of signalling molecules and molecular adaptors for intracellular signal propagation become increasingly apparent. Intracellular inhibitors of RTK signalling are widely involved in the regulation of developmental signalling in NSPC and often determine developmental outcomes of RTK activation. In addition, cellular responses of NSPC to the activation of a given RTK may be significantly modulated by signal strength. Cellular propensity to respond also plays a role in developmental outcomes of RTK signalling. In combination, these mechanisms regulate the balance between NSPC maintenance and differentiation during development and in adulthood. Attribution of particular developmental responses of NSPC to specific pathways of RTK signalling becomes increasingly elucidated. Co-activation of several RTK in developing NSPC is common, and analysis of co-operation between their signalling pathways may advance knowledge of RTK role in NSPC development.

Glycosaminoglycans from aged human hippocampus have altered capacities to regulate trophic factors activities but not Aβ42 peptide toxicity

Glycosaminoglycans (GAGs) are major extracellular matrix components known to tightly regulate cell behavior by interacting with tissue effectors as trophic factors and other heparin binding proteins. Alterations of GAGs structures might thus modify the nature and extent of these interactions and alter tissue integrity. Here, we studied levels and composition of GAGs isolated from adult and aged human hippocampus and investigated if their changes can influence the function of important trophic factors and the Aβ42 peptide toxicity. Biochemical analyses showed that heparan sulfates are increased in the aged hippocampus. Moreover, GAGs from aged hippocampus showed altered capacities to regulate trophic factor activities without changing their capacities to protect cells from Aβ42 toxicity, compared to adult hippocampus GAGs. Structural alterations in GAGs from elderly were suggested by differential transcripts levels of key biosynthetic enzymes. C5-epimerase and 2-OST expressions were decreased while NDST-2 and 3-OST-4 were increased; in contrast, heparanase expression was unchanged. Results suggest that alteration of GAGs in hippocampus of aged subjects could participate to tissue impairment during aging.

Release of VEGF and FGF in the extracellular space following severe subarachnoidal haemorrhage or traumatic head injury in humans

Microdialysate fluid from 145 severely injured NSICU-patients, 88 with subarachnoidal haemorrage (SAH), and 57 with traumatic brain injury (TBI), was collected by microdialysis during the first 7 days following impact, and levels of the neurotrophins fibroblast growth factor-2 (FGF2) and vascular endothelial growth factor (VEGF) were analysed. The study illustrates both similarities and differences in the reaction patterns of the 2 inflammatory proteins. The highest concentrations of both FGF2 and VEGF were measured on Day 2 (mean (+/- SE) values being 47.1 +/- 15.33 and 116.9 +/- 41.85 pg/ml, respectively, in the pooled patient material). The VEGF concentration was significantly higher in TBI-patients, while the FGF2 showed a tendency to be higher in SAH-patients. This is the first report presenting in some detail the human cerebral response of FGF2 and VEGF following SAH and TBI. Apart from increasing the understanding of the post-impact inflammatory response of the human brain, the study identifies potential threshold values for these chemokines that may serve as monitoring indicators in the NSICU.

Effect of age on proliferation-regulating factors in human adult neurogenic regions

Neurogenesis, the birth of new neurons, continues throughout adulthood in the human subventricular zone (SVZ) and hippocampus. It is not known how levels of putative proliferation-regulating factors change with age in human adult neurogenic areas. The current project employed ELISAs to investigate changes in levels of putative proliferation-regulating factors in the healthy human SVZ and dentate gyrus throughout the adult lifespan (18-104 years). Levels of brain-derived neurotrophic factor, basic fibroblast growth factor and interleukin (IL)-1β were significantly higher in the hippocampus than in the SVZ and levels of glial-derived neurotrophic factor and transforming growth factor-α were significantly higher in the SVZ (p < 0.005), suggesting that factors with predominant influences on neurogenesis differ between the two human adult neurogenic areas. Hippocampal levels of transforming growth factor-β1 strongly increased with age (n = 9, p < 0.01), whereas hippocampal and SVZ levels of brain-derived neurotrophic factor, epidermal growth factor, basic fibroblast growth factor, glial-derived neurotrophic factor, heparin-binding epidermal growth factor, insulin-like growth factor-1, IL-1β, IL-6 and transforming growth factor-α did not change significantly with age in the SVZ or hippocampus. These findings suggest regulation of the adult neurogenic environment in the human brain may differ over time from that in other species.

The neuropeptide VGF is reduced in human bipolar postmortem brain and contributes to some of the behavioral and molecular effects of lithium

Recent studies demonstrate that the neuropeptide VGF (nonacronymic) is regulated in the hippocampus by antidepressant therapies and animal models of depression and that acute VGF treatment has antidepressant-like activity in animal paradigms. However, the role of VGF in human psychiatric disorders is unknown. We now demonstrate using in situ hybridization that VGF is downregulated in bipolar disorder in the CA region of the hippocampus and Brodmann's area 9 of the prefrontal cortex. The mechanism of VGF in relation to LiCl was explored. Both LiCl intraperitoneally and VGF intracerebroventricularly reduced latency to drink in novelty-induced hypophagia, and LiCl was not effective in VGF(+/-) mice, suggesting that VGF may contribute to the effects of LiCl in this behavioral procedure that responds to chronic antidepressant treatment. VGF by intrahippocampal injection also had novel activity in an amphetamine-induced hyperlocomotion assay, thus mimicking the actions of LiCl injected intraperitoneally in a system that phenocopies manic-like behavior. Moreover, VGF(+/-) mice exhibited increased locomotion after amphetamine treatment and did not respond to LiCl, suggesting that VGF is required for the effects of LiCl in curbing the response to amphetamine. Finally, VGF delivered intracerebroventricularly in vivo activated the same signaling pathways as LiCl and is necessary for the induction of mitogen-activated protein kinase and Akt by LiCl, thus lending insight into the molecular mechanisms underlying the actions of VGF. The dysregulation of VGF in bipolar disorder as well as the behavioral effects of the neuropeptide similar to LiCl suggests that VGF may underlie the pathophysiology of bipolar disorder.

Genetic variation in FGF20 modulates hippocampal biology

We explored the effect of single-nucleotide polymorphisms (SNPs) in the fibroblast growth factor 20 gene (FGF20) associated with risk for Parkinson's disease on brain structure and function in a large sample of healthy young-adult human subjects and also in elderly subjects to look at the interaction between genetic variations and age (N = 237; 116 men; 18-87 years). We analyzed high-resolution anatomical magnetic resonance images using voxel-based morphometry, a quantitative neuroanatomical technique. We also measured FGF20 mRNA expression in postmortem human brain tissue to determine the molecular correlates of these SNPs (N = 108; 72 men; 18-74 years). We found that the T allele carriers of rs12720208 in the 3'-untranslated region had relatively larger hippocampal volume (p = 0.0059) and diminished verbal episodic memory (p = 0.048) and showed steeper decreases of hippocampal volume with normal aging (p = 0.026). In postmortem brain, T allele carriers had greater expression of hippocampal FGF20 mRNA (p = 0.037), consistent with a previously characterized microRNA mechanism. The C allele matches a predicted miR-433 microRNA binding domain, whereas the T allele disrupts it, resulting in higher FGF20 protein translation. The strong FGF20 genetic effects in hippocampus are presumably mediated by activation of the FGFR1 (FGF receptor 1), which is expressed in mammalian brain most abundantly in the hippocampus. These associations, from mRNA expression to brain morphology to cognition and an interaction with aging, confirm a role of FGF20 in human brain structure and function during development and aging.

FGF2 modulates the voltage-dependent K+ current and changes excitability of rat dentate gyrus granule cells

Fibroblast growth factor 2 (FGF2) is involved in hippocampus-dependent learning. In this study, the effects of FGF2 on the excitability were investigated in granule cells of rat dentate gyrus. Hippocampal slices were used to perform patch clamp recordings in granule cells. Extracellularly applied FGF2 early quenched the depolarization-induced repetitive firing, suggesting a decreased excitability under these conditions. Consistently, transient and sustained voltage-gated K(+) currents decreased in a dose-dependent manner, repolarization phase of action potential was slowed down, afterhyperpolarization was reduced, and membrane resistance was decreased. These effects were not mediated by tyrosine kinase FGF2 receptors. Moreover, an involvement of G protein signaling was ruled out, as well as an intracellular action of FGF2. Considering the relationship between FGF2 and hippocampal functions, the modulation of neuron excitability by activity-driven FGF2 release may be regarded as a part of a homeostatic mechanism of self-regulation of hippocampal activity.

Fgf-2 overexpression increases excitability and seizure susceptibility but decreases seizure-induced cell loss

Fibroblast growth factor 2 (FGF-2) has multiple, pleiotropic effects on the nervous system that include neurogenesis, neuroprotection and neuroplasticity. Thus, alteration in FGF-2 expression patterns may have a profound impact in brain function, both in normal physiology and in pathology. Here, we used FGF-2 transgenic mice (TgFGF2) to study the effects of endogenous FGF-2 overexpression on susceptibility to seizures and to the pathological consequences of seizures. TgFGF2 mice display increased FGF-2 expression in hippocampal pyramidal neurons and dentate granule cells. Increased density of glutamatergic synaptic vesicles was observed in the hippocampus of TgFGF2 mice, and electrophysiological data (input/output curves and patch-clamp recordings in CA1) confirmed an increase in excitatory inputs in CA1, suggesting the presence of a latent hyperexcitability. Indeed, TgFGF2 mice displayed increased susceptibility to kainate-induced seizures compared with wild-type (WT) littermates, in that latency to generalized seizure onset was reduced, whereas behavioral seizure scores and lethality were increased. Finally, WT and TgFGF2 mice with similar seizure scores were used for examining seizure-induced cellular consequences. Neurogenesis and mossy fiber sprouting were not significantly different between the two groups. In contrast, cell damage (assessed with Fluoro-Jade B, silver impregnation and anti-caspase 3 immunohistochemistry) was significantly lower in TgFGF2 mice, especially in the areas of overexpression (CA1 and CA3), indicating reduction of seizure-induced necrosis and apoptosis. These data suggest that FGF-2 may be implicated in seizure susceptibility and in seizure-induced plasticity, exerting different, and apparently contrasting effects: favoring ictogenesis but reducing seizure-induced cell death.

Basic fibroblast growth factor-enhanced neurogenesis contributes to cognitive recovery in rats following traumatic brain injury

Stem/progenitor cells reside throughout the adult CNS and are actively dividing in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus. This neurogenic capacity of the SVZ and DG is enhanced following traumatic brain injury (TBI) suggesting that the adult brain has the inherent potential to restore populations lost to injury. This raises the possibility of developing strategies aimed at harnessing the neurogenic capacity of these regions to repair the damaged brain. One strategy is to enhance neurogenesis with mitogenic factors. As basic fibroblast growth factor (bFGF) is a potent stem cell mitogen, we set out to determine if an intraventricular administration of bFGF following TBI could affect the levels of injury-induced neurogenesis in the SVZ and DG, and the degree to which this is associated with cognitive recovery. Specifically, adult rats received a bFGF intraventricular infusion for 7 days immediately following TBI. BrdU was administered to animals daily at 2-7 days post-injury to label cell proliferation. At 1 or 4 weeks post-injury, brain sections were immunostained for BrdU and neuronal or astrocytic markers. We found that injured animals infused with bFGF exhibited significantly enhanced cell proliferation in the SVZ and the DG at 1 week post-TBI as compared to vehicle-infused animals. Moreover, following bFGF infusion, a greater number of the newly generated cells survived to 4 weeks post-injury, with the majority being neurons. Additionally, animals infused with bFGF showed significant cognitive improvement. Collectively, the current findings suggest that bFGF-enhanced neurogenesis contributes to cognitive recovery following TBI.

Neurogenesis in the human hippocampus and its relevance to temporal lobe epilepsies

Ample evidence points to the dentate gyrus as anatomical region for persistent neurogenesis in the adult mammalian brain. This has been confirmed in a variety of animal models under physiological as well as pathophysiological conditions. Notwithstanding, similar experiments are difficult to perform in humans. Postmortem studies demonstrated persisting neurogenesis in the elderly human brain. In addition, neural precursor cells can be isolated from surgical specimens obtained from patients with intractable temporal lobe epilepsy (TLE) and propagated or differentiated into neuronal and glial lineages. It remains a controversial issue, whether epileptic seizures have an effect on or even increase hippocampal neurogenesis in humans. Recent data support the notion that seizures induce neurogenesis in young patients, whereas the capacity of neuronal recruitment and proliferation decreases with age. Animal models of TLE further indicate that these newly generated neurons integrate into epileptogenic networks and contribute to increased seizure susceptibility. However, pathomorphological disturbances within the epileptic hippocampus, such as granule cell dispersion (GCD), may not directly result from compromised neurogenesis. Still, the majority of adult TLE patients present with significant dentate granule cell loss at an end stage of the disease, which relates to severe memory and learning disabilities. In conclusion, surgical specimens obtained from TLE patients represent an important tool to study mechanisms of stem cell recruitment, proliferation and differentiation in the human brain. In addition, increasing availability of surgical specimens opens new avenues to systematically explore disease pathomechanisms in chronic epilepsies.

Changes in extracellular concentrations of some cytokines, chemokines, and neurotrophic factors after insertion of intracerebral microdialysis catheters in neurosurgical patients

OBJECTIVE

The extracellular levels of eight different inflammatory agents were analyzed during the initial 36 hours after insertion of microdialysis catheters in patients.

METHODS

Cerebral extracellular fluid from 38 patients who were treated in a neurosurgical intensive care unit for severe brain injury was collected every 6 hours for 36 hours. The concentration of interleukin (IL)-1 beta, IL-6, IL-8, macrophage inflammatory protein-1 beta, regulated on activation, normal T-cell expressed and secreted (RANTES), fibroblast growth factor-2, and vascular endothelial growth factor was determined by a multiplex assay, and IL-10 was determined by enzyme-linked immunosorbent assay.

RESULTS

This is the first report regarding the presence of IL-10, IL-8, macrophage inflammatory protein-1 beta, regulated on activation, T-cell expressed and secreted, vascular endothelial growth factor, and fibroblast growth factor-2 in the tissue level proper of the living human brain. The study also provides new information regarding the response of IL-1 beta and IL-6 after insertion of a microdialysis catheter. The study confirms that the intriguing patterns of interplay between different components of the inflammatory response studied in laboratory settings are present in the human brain. This was most clearly observed in the variations in response between the three different chemokines investigated, as well as in the rapid and transient response of fibroblast growth factor-2.

CONCLUSION

The data presented illustrate the opportunity to monitor biochemical events of possible importance in the human brain and indicate the potential of such monitoring in neurosurgical intensive care. The study also underlines that any analysis of events in the brain involving mechanical invasiveness needs to take into account biochemical changes that are directly related to the manipulation of brain tissue.

Synaptic function for the Nogo-66 receptor NgR1: regulation of dendritic spine morphology and activity-dependent synaptic strength

In the mature nervous system, changes in synaptic strength correlate with changes in neuronal structure. Members of the Nogo-66 receptor family have been implicated in regulating neuronal morphology. Nogo-66 receptor 1 (NgR1) supports binding of the myelin inhibitors Nogo-A, MAG (myelin-associated glycoprotein), and OMgp (oligodendrocyte myelin glycoprotein), and is important for growth cone collapse in response to acutely presented inhibitors in vitro. After injury to the corticospinal tract, NgR1 limits axon collateral sprouting but is not important for blocking long-distance regenerative growth in vivo. Here, we report on a novel interaction between NgR1 and select members of the fibroblast growth factor (FGF) family. FGF1 and FGF2 bind directly and with high affinity to NgR1 but not to NgR2 or NgR3. In primary cortical neurons, ectopic NgR1 inhibits FGF2-elicited axonal branching. Loss of NgR1 results in altered spine morphologies along apical dendrites of hippocampal CA1 neurons in vivo. Analysis of synaptosomal fractions revealed that NgR1 is enriched synaptically in the hippocampus. Physiological studies at Schaffer collateral-CA1 synapses uncovered a synaptic function for NgR1. Loss of NgR1 leads to FGF2-dependent enhancement of long-term potentiation (LTP) without altering basal synaptic transmission or short-term plasticity. NgR1 and FGF receptor 1 (FGFR1) are colocalized to synapses, and mechanistic studies revealed that FGFR kinase activity is necessary for FGF2-elicited enhancement of hippocampal LTP in NgR1 mutants. In addition, loss of NgR1 attenuates long-term depression of synaptic transmission at Schaffer collateral-CA1 synapses. Together, our findings establish that physiological NgR1 signaling regulates activity-dependent synaptic strength and uncover neuronal NgR1 as a regulator of synaptic plasticity.

Stress-induced glucocorticoids suppress the antisense molecular regulation of FGF-2 expression

Psychological stress can upregulate basic fibroblast growth factor (FGF-2) expression. Because glucocorticoids can also upregulate FGF-2 expression, the present studies investigated whether stress-induced glucocorticoids mediate the effects of stress on FGF-2. FGF-2 is regulated by an FGF-2 antisense (AS) molecular mechanism and so the present experiments also, for the first time, assessed the effects of stress on FGF-2-AS mRNA, as well as the mediating role of glucocorticoids. The effects of either escapable shock (ES) or yoked-inescapable tail shock (IS) on FGF-2 and FGF-2-AS were determined. To test whether glucocorticoids mediate the effect of stress on FGF-2 and FGF-2-AS, animals were pretreated with temporary corticosterone (CORT) synthesis inhibitors and exposed to IS. To test whether glucocorticoids are sufficient to modulate FGF-2 and FGF-2-AS mRNA, animals were injected with CORT and mRNA measured. ES and IS similarly downregulated FGF-2-AS mRNA at 0 h post-stress and upregulated FGF-2 mRNA 2 h post-stress. Inhibition of CORT synthesis abrogated the effect of IS on both FGF-2-AS and FGF-2 mRNA. Exogenous CORT mimicked the effects of ES and IS on FGF-2, but not FGF-2-AS mRNA. The present study demonstrates that glucocorticoids mediate the effects of stress on FGF-2 and FGF-2-AS.

The fibroblast growth factor system and mood disorders

Recent evidence now suggests the involvement of the fibroblast growth factor (FGF) system in mood disorders. Specifically, several members of the FGF family have been shown to be dysregulated in individuals with major depression. In this review, we will introduce the FGF system in terms of structure and function during development, in adulthood, and in various regions and cell types. We will also review the FGF system as a mediator of neural plasticity. Furthermore, this review will summarize animal as well as human studies. The majority of animal studies have focused on stress, environmental enrichment, pharmacological manipulations, and the hippocampus. By contrast, human studies have focused on volumetric measurements, antidepressant literature, and, most recently, post-mortem microarray experiments. In summary, a reduced tone in the FGF system might alter brain development or remodeling and result in a predisposition or vulnerability to mood disorders, including major depression.

Hippocampal FGF-2 and FGFR1 mRNA expression in major depression, schizophrenia and bipolar disorder

INTRODUCTION

FGF-2 is important for stem cell proliferation, neocortical development and adult neuronal survival and growth. Reduced frontal cortical FGF-2 expression is described in major depression and is attenuated by antidepressants. We determined the distribution of hippocampal FGF-2 and its receptor (FGFR1) mRNA in post-mortem brains of people who suffered from major depression, bipolar disorder and schizophrenia and those of controls.

METHODS

FGF-2 and FGFR1 mRNA were measured within hippocampal CA1, CA4 regions and the dentate gyrus (DG), using in situ hybridization. Within hippocampal regions, cellular staining was compared between diagnostic groups, using repeated measures analysis of variance.

RESULTS

The density of FGF-2 mRNA+ cells in CA4 was reduced in depression compared to controls. The percentage of FGFR1 mRNA+ cells was higher in depression (CA1 and CA4) and schizophrenia (CA4) than in controls. FGFR1 mRNA expression was higher in depression than in the other groups in CA1, CA4 and DG. Overall FGF-2 mRNA expression was higher in DG than in CA1 and CA4.

CONCLUSIONS

We found raised measures of FGFR1 mRNA+ in major depression and, less so, in schizophrenia, along with reduced FGF-2 mRNA density in depression. Perturbations of FGF regulation could be relevant to the pathogenesis of both disorders as FGF-2 and FGFR1 are implicated in normal hippocampal synaptology, stem cell recruitment, and connectivity, and are modulated by corticosteroids.

Glioma stem cells: evidence and limitation

Gliomas, in particular the high-grade anaplastic glioma and glioblastoma multiforme (GBM), are manifested by morphological, genetic and phenotypic heterogeneity. Most of the studies hitherto have been performed on bulk glioma cells, with limited understanding on the origin and the relative contribution of particular glioma cell populations to glioma growth and progression. Recent studies have demonstrated the existence of a small fraction of glioma cells endowed with features of primitive neural progenitor cells and tumor-initiating function. Such cells have been defined as glioma stem cells. However, questions remain as to whether the currently identified glioma stem cells are the cell-of-origin for glioma initiation and progression, or the results of such processes. In this review, we discuss the current evidence and limitation in identifying glioma stem cells and the potential origin of glioma stem cells in the context of post-natal neural cell regeneration and their transformation mechanisms. The implication of these findings for glioma diagnosis and treatment will also be reviewed.