Walls Of Lateral Ventricles Research Articles

EphB Signaling Controls Lineage Plasticity of Adult Neural Stem Cell Niche Cells

Stem cells remain in specialized niches over the lifespan of the organism in many organs to ensure tissue homeostasis and enable regeneration. How the niche is maintained is not understood, but is probably as important as intrinsic stem cell self-renewal capacity for tissue integrity. We here demonstrate a high degree of phenotypic plasticity of the two main niche cell types, ependymal cells and astrocytes, in the neurogenic lateral ventricle walls in the adult mouse brain. In response to a lesion, astrocytes give rise to ependymal cells and ependymal cells give rise to niche astrocytes. We identify EphB2 forward signaling as a key pathway regulating niche cell plasticity. EphB2 acts downstream of Notch and is required for the maintenance of ependymal cell characteristics, thereby inhibiting the transition from ependymal cell to astrocyte. Our results show that niche cell identity is actively maintained and that niche cells retain a high level of plasticity.

EGF induces CREB and ERK activation at the wall of the mouse lateral ventricles

The subependymal zone at the lateral ventricular wall represents a major neurogenic niche of the adult mammalian brain and continuously provides new neurons for the olfactory bulb. A mosaic of stem and progenitor cells in this niche has the potential to respond to multiple signals including growth factors such as EGF. Recent studies using long-term ventricular infusion of EGF demonstrate intense cell proliferation around the ventricular wall, implicating the presence of EGF-reactive cells also outside the classical neurogenic lateral niche. Here we show that intraventricular injection of EGF induces within minutes CREB and ERK phosphorylation in astrocyte-like progenitor cells (type B cells) and EGF receptor-expressing transit-amplifying progenitor cells—both in the striatal and septal ventricular walls. EGF infusion for 6 days induced continued CREB and ERK activation in nestin+ cells paralleled by intense periventricular cell proliferation. In addition, the ependyma became EGF receptor-immunoreactive, revealed intense CREB phosphorylation and underwent partial de-differentiation. Our results demonstrate that intraventricular application of EGF induces CREB and ERK phosphorylation along the entire ventricular walls and thus permits a direct identification of EGF-responsive cell types. They further support the notion that not only the striatal ventricular wall where the SEZ is located but also the septal ventricular wall carries latent potential for the formation of neurons and glial cells.

Prospectively isolated CD133/CD24‐positive ependymal cells from the adult spinal cord and lateral ventricle wall differ in their long‐term in vitro self‐renewal and in vivo gene expression

In contrast to ependymal cells located above the subventricular zone (SVZ) of the adult lateral ventricle wall (LVW), adult spinal cord (SC) ependymal cells possess certain neural stem cell characteristics. The molecular basis of this difference is unknown. In this study, antibodies against multiple cell surface markers were applied to isolate pure populations of SC and LVW ependymal cells, which allowed a direct comparison of their in vitro behavior and in vivo gene expression profile. Isolated CD133(+)/CD24(+)/CD45(-)/CD34(-) ependymal cells from the SC displayed in vitro self-renewal and differentiation capacity, whereas those from the LVW did not. SC ependymal cells showed a higher expression of several genes involved in cell division, cell cycle regulation, and chromosome stability, which is consistent with a long-term self-renewal capacity, and shared certain transcripts with neural stem cells of the embryonic forebrain. They also expressed several retinoic acid (RA)-regulated genes and responded to RA exposure. LVW ependymal cells showed higher transcript levels of many genes regulated by transforming growth factor-β family members. Among them were Dlx2, Id2, Hey1, which together with Foxg1 could explain their potential to turn into neuroblasts under certain environmental conditions.

Locating and labeling neural stem cells in the brain

The phenomenon of adult neurogenesis has been demonstrated in most mammals including humans. At least two regions of the adult brain maintain stem cells throughout life; the subgranular zone (SGZ) of the hippocampal dentate gyrus, and the subventricular zone (SVZ) of the lateral ventricle wall. Both regions continuously produce neurons that mature and become integrated into functional networks that are involved in learning and memory and odor discrimination, respectively. Apart from these well-studied regions neurogenesis has been reported in a number of other brain regions, such as amygdala and cortex. However, these studies have been contested and there is currently no well-postulated function for non-SVZ/SGZ neurogenesis. The studies of the regional localization of neurogenesis in the brain have been made possible due to several methods for detecting adult neurogenesis including; bromodeoxyuridine labeling (BrdU) together with markers of mature neurons, genetic labeling, by mouse transgenesis, or with the use of viral vectors. These techniques are already put to creative use and will be essential for the discovery of the nature of the adult neural stem cells. In this mini-review, we will discuss the localization of neural stem/progenitor cells in the brain and their implications as well as discussing the pro's and con's of stem cell labeling techniques.

Editorial [Hot topic: Immunological Regulation of the Central Nervous System: From Physiological to Pathological Processes (Guest Editor: Oscar Gonzalez-Perez)

The central nervous system (CNS) is an immune-privileged organ because a selective permeability to exchange blood cells and substances from the circulatory system. Nevertheless, increasing evidence indicates that an extensive bi-directional communication takes place between the CNS and the immune system. Thus, the psyconeuroimmunology has emerged as a relative novel discipline to study interactions among psychological processes, brain functioning and the immune system. This especial issue of the Current Immunology Reviews contains nine comprehensive articles addressing the interactions between the immune and nervous systems in either physiological or pathological conditions. In an excellent review, Cordiglieri and Farina explain the role of astrocytes in initiating and tuning cerebral immune responses. Authors state that astrocytes promote or confine inflammatory processes and, in consequence, play a role in neuroprotection and CNS repair. Astrocytes act as immune-competent cells by secreting cytokines and chemokines, and participating in innate immunity. As reviewed by Tian and Rauvala, the communication between immune system and CNS is bi-directional, in fact, neurons participate in immune responses by controlling responses of microglia and T lymphocytes. Interestingly, the immune system also controls proliferation, differentiation, migration and self-renewal of adult neural stem cells, which reside in the wall of lateral ventricles of brain. Modulation of neural stem cells are mainly mediated by IL-6, IL-18, TNF-α, CNTF, LIF and IFN-γ [1–3]. Neuroinflammation plays a role in the etiology and/or progression of several neurological disorders. As reviewed by Ramos and Duran, rheumatoid arthritis is a systemic inflammatory disorder that affects the central and peripheral nervous system. As in other rheumatic diseases, TNF-α is one of the main mediators of CNS damage. Orozco et al. reviewed the effects of inflammatory reactions on neuronal excitability, cell survival impairment, and permeability to blood-borne molecules and cells. These pathological events and high levels of IL-1, IL-2, and TNF-α have been associated with epilepsy development and seizures. Cytokines and chemokines also modulate cognitive and emotional processes in the absence of overt immunological, physiological, or psychological challenges. Psychological stress and glucocorticoid-related immunosuppression is reviewed by Jauregui et al. They explain that stress increases the levels of glucocorticoids, which target resident microglia and decrease the ability of these brain cells to proliferate, to produce pro-inflammatory cytokines, and to produce toxic radicals. Brain Leonard summarizes evidence indicating that IL-1, IL-4, IL-6, IL-10, IL-13, IFN-α and TNF-α can affect cognitive and emotional processes as observed in major depression [4, 5]. Pro-inflammatory cytokines affect neuronal signaling by enhancing the glutamatergic system, which stimulates the tryptophan-kynurenine pathway. In an excellent review, Muller and Schwarz explain that high levels of IL-8 during pregnancy are associated with an increased risk for schizophrenia in the offspring. In this landmark review, the authors indicate that infections of the CNS in early childhood increase risk for developing psychoses and that IL-6 serum levels are elevated in patients with an unfavourable course of mental disease. This issue concludes with the striking proposal of Momin et al. who addressed the oncogenic and tumor-supporting potential of mesenchimal stem cells (MSCs) within the context of cancer treatment. This review states the risk for malignant transformation of MSCs, the in vivo interactions with tumor stroma and the immunosuppressive qualities of MSCs that facilitate evasion of the immune system by tumors. In summary, increasing evidence indicates that cytokines and chemokines modulate cerebral functions through multiple signaling pathways. All these interactions affect neural remodeling, synaptic plasticity, neurotransmitter releasing, neuronal regeneration, brain aging, cognitive and emotional processes, and mental disease progression. All these events modulate cognitive and emotional processes, and brain disease predisposition/progression.

Intracerebroventricular Transplantation of Cord Blood-Derived Neural Progenitors in a Child With Severe Global Brain Ischemic Injury.

Transplantation of neural stem/precursor cells has recently been proposed as a promising, albeit still controversial, approach to brain repair. Human umbilical cord blood could be a source of such therapeutic cells, proven beneficial in several preclinical models of stroke. Intracerebroventricular infusion of neutrally committed cord blood-derived cells allows their broad distribution in the CNS, whereas additional labeling with iron oxide nanoparticles (SPIO) enables to follow the fate of engrafted cells by MRI. A 16-month-old child at 7 months after the onset of cardiac arrest-induced global hypoxic/ischemic brain injury, resulting in a permanent vegetative state, was subjected to intracerebroventricular transplantation of the autologous neutrally committed cord blood cells. These cells obtained by 10-day culture in vitro in neurogenic conditions were tagged with SPIO nanoparticles and grafted monthly by three serial injections (12 × 10(6) cells/0.5 ml) into lateral ventricle of the brain. Neural conversion of cord blood cells and superparamagnetic labeling efficiency was confirmed by gene expression, immunocytochemistry, and phantom study. MRI examination revealed the discrete hypointense areas appearing immediately after transplantation in the vicinity of lateral ventricles wall with subsequent lowering of the signal during entire period of observation. The child was followed up for 6 months after the last transplantation and his neurological status slightly but significantly improved. No clinically significant adverse events were noted. This report indicates that intracerebroventricular transplantation of autologous, neutrally committed cord blood cells is a feasible, well tolerated, and safe procedure, at least during 6 months of our observation period. Moreover, a cell-related MRI signal persisted at a wall of lateral ventricle for more than 4 months and could be monitored in transplanted brain hemisphere.

Screening for cardiomyopathy in muscular dystrophy with tissue doppler imaging

To study role of Tissue Doppler imaging (TDI) in identification of cardiomyopathy before development of ventricular dysfunction. Twenty-five patients with Duchenne's (DMD) and 10 with Becker's (BMD) muscular dystrophy along with 20 controls were evaluated using TDI. Pulse Tissue Doppler signals of the lateral left ventricle wall (lateral mitral annulus) revealed reduced systolic velocities in the DMD patients (mean +/- SD: 7.8 +/- 1.1 cm/sec vs. 8.6 +/- 1.1 cm/sec in controls) in patients of DMD. 60% of the non ambulatory DMD (ejection fraction 45+/-9%) patients had mild LV dysfunction and reduced systolic velocities (6.96 +/- 1.7 cm/sec, p<0.05 vs controls). The ambulatory DMD patients also had reduced systolic velocities (7.8 +/- 1.1 cm/sec) though ejection fraction was normal. Reduced tissue Doppler systolic velocities in the ambulatory DMD patients with normal conventional echocardiography would suggest that perhaps some of these patients (20% had velocities less than Mean - 2 SD of controls) have early myocardial dysfunction (picked up only as abnormal myocardial velocities). TDI picked up systolic dysfunction of the lateral wall in DMD even when overall LV function was normal conventional echocardiography. Tissue Doppler imaging is a useful technique to pick up early ventricular dysfunction and should be evaluated in larger studies and also with other techniques like magnetic resonance imaging.

Location of the corticospinal tract at the corona radiata in human brain

Little is known about the location of the corticospinal tract (CST) at the corona radiata (CR). In the current study we attempted to elucidate the location of the CST for the hand at the CR using diffusion tensor tractography analysis based on functional MRI activation results. Functional MRI was performed at 1.5-T with timed hand grasp-release movements, and diffusion tensor tractography was performed using a Synergy-L Sensitivity Encoding (SENSE) head coil. Probabilistic mapping was obtained for 16 normal subjects using areas of functional MRI activation as the first region of interest (ROI 1) and the CST area in the lower pons as the second region of interest (ROI 2). The authors measured the antero-posterior and medio-lateral locations of pixels in the CST in two areas of the CR (CR 1 — the first axial image to show the septum pellucidum and the body of the fornix from the vertex, and CR 2 — the axial image showing the insular gyrus). The most probable locations in the medio-lateral direction (from the most medial point of the lateral ventricle wall to the most lateral point of the cerebral cortex) were 24.2% in both CR 1 and 2, and the most probable locations in the antero-posterior direction (from the most anterior point of the lateral ventricle to the most posterior point of the lateral ventricle) were 66.7 and 63.6% in CR 1 and 2, respectively. It was found that the CST for the hand descended through about one quarter (medio-lateral direction) and two-thirds (antero-posterior direction) at the CR.

Cilia Organize Ependymal Planar Polarity

Multiciliated epithelial cells, called ependymal cells, line the ventricles in the adult brain. Most ependymal cells are born prenatally and are derived from radial glia. Ependymal cells have a remarkable planar polarization that determines orientation of ciliary beating and propulsion of CSF. Disruption of ependymal ciliary beating, by injury or disease, results in aberrant CSF circulation and hydrocephalus, a common disorder of the CNS. Very little is known about the mechanisms guiding ependymal planar polarity and whether this organization is acquired during ependymal cell development or is already present in radial glia. Here we show that basal bodies in ependymal cells in the lateral ventricle walls of adult mice are polarized in two ways: (1) rotational; angle of individual basal bodies with respect to their long axis and (2) translational; the position of basal bodies on the apical surface of the cell. Conditional ablation of motile cilia disrupted rotational orientation, but translational polarity was largely preserved. In contrast, translational polarity was dramatically affected when radial glial primary cilia were ablated earlier in development. Remarkably, radial glia in the embryo have a translational polarity that predicts the orientation of mature ependymal cells. These results suggest that ependymal planar cell polarity is a multistep process initially organized by primary cilia in radial glia and then refined by motile cilia in ependymal cells.

Combinations of genetic mutations in the adult neural stem cell compartment determine brain tumour phenotypes

It has been suggested that intrinsic brain tumours originate from a neural stem/progenitor cell population in the subventricular zone of the post-natal brain. However, the influence of the initial genetic mutation on the phenotype as well as the contribution of mature astrocytes to the formation of brain tumours is still not understood. We deleted Rb/p53, Rb/p53/PTEN or PTEN/p53 in adult subventricular stem cells; in ectopically neurografted stem cells; in mature parenchymal astrocytes and in transplanted astrocytes. We found that only stem cells, but not astrocytes, gave rise to brain tumours, independent of their location. This suggests a cell autonomous mechanism that enables stem cells to generate brain tumours, whereas mature astrocytes do not form brain tumours in adults. Recombination of PTEN/p53 gave rise to gliomas whereas deletion of Rb/p53 or Rb/p53/PTEN generated primitive neuroectodermal tumours (PNET), indicating an important role of an initial Rb loss in driving the PNET phenotype. Our study underlines an important role of stem cells and the relevance of initial genetic mutations in the pathogenesis and phenotype of brain tumours.

Intraparenchymal myofibromatosis of the brain in an adult: report of an unusual case

An unusual case of intraparenchymal myofibromatosis of the brain occurring in a 29-year-old woman is described. Preoperative CT and MRI examinations revealed two well-circumscribed nodular masses localized in the wall of the left lateral ventricle and right temporal lobe, respectively. Both masses were completely resected, and the patient remains disease-free 2 years post-surgery. Histopathologically, the lesions were characterized by stratification. From outer to inner, there was a reactive glial component, lamellated well-differentiated muscle-like cells, densely compact collagen fibers and cellular tumor with nodular and hemangiopericytoma-like patterns, respectively. The myofibroblastic nature of this tumor was verified by immunohistochemical staining and ultrastructural analysis. Intraparenchymal myofibromatosis may be confused with, and should be distinguished from, meningioma, myopericytoma, solitary fibrous tumor, leiomyoma and inflammatory myofibroblastic tumor for accurate diagnosis and optimal treatment.

Home at Last: Neural Stem Cell Niches Defined

Adult neural stem cells (NSCs) are involved in regulating mammalian behavior and are controlled by diverse external stimuli. Improved understanding of the physical location of NSCs and the microenvironmental cues that regulate their behavior, which combine to define the NSC "home," or niche, may reveal how to control their function.

Grafted neural progenitors migrate and form neurons after experimental traumatic brain injury

Neural stem and progenitor cells (NSPC) generate neurons and glia, a feature that makes them attractive for cell replacement therapies. However, efforts to transplant neural progenitors in animal models of brain injury typically result in high cell mortality and poor neuronal differentiation. In an attempt to improve the outcome for grafted NSPC after controlled cortical impact we transplanted Enhanced Green Fluorescent Protein (EGFP)-positive NSPC into the contra lateral ventricle of mice one week after injury. Grafted EGFP-NSPC readily migrated to the injured hemisphere where we analyzed the proportion of progenitors and differentiated progeny at different time points. Transplantation directly into the injured parenchyma, resulted in few brains with detectable EGFP-NSPC. On the contrary, in more than 90% of the mice that received a transplant into the lateral ventricle detectable EGFP-positive cells were found. The cells were integrated into the lateral ventricle wall of the un-injured hemisphere, throughout the corpus callosum, and in the cortical perilesional area. At one-week post transplantation, grafted cells that had migrated to the perilesion area mainly expressed markers of neural progenitors and neurons, while in the corpus callosum and the ventricular lining, grafted cells with a glial fate were more abundant. After 3 months, grafted cells in the perilesion area were less abundant whereas cells that had migrated to the walls of the third- and lateral- ventricle of the injured hemisphere were still detectable, suggesting that the injury site remained a hostile environment. Transplantation to the lateral ventricle, presumably for being a neurogenic region, provides a favorable environment improving the outcome for grafted NSPC both in term of their appearance at the cortical site of injury, and their acquisition of neural markers.

Adverse Left Ventricular Mechanics in Adults With Repaired Tetralogy of Fallot

Left ventricular (LV) dysfunction is a predictor of adverse outcomes in patients with repaired tetralogy of Fallot (TOF). However, the mechanisms for LV dysfunction are not well understood. The aim of the study was to determine whether the prolonged QRS duration of right branch bundle block was associated with adverse LV mechanics. Seventy-five patients (mean age 31 +/- 2 years) with repaired TOF were studied. LV and right ventricular (RV) volumes and ejection fractions (EFs) were assessed using cardiac magnetic resonance imaging. Vector velocity imaging was used to assess longitudinal strain and intraventricular dyssynchrony. Prolonged QRS duration was associated with increased RV and LV dimensions (p = 0.01) and decreased function (RVEF r = -0.60, p <0.001 and LVEF r = -0.77, p <0.001). In addition, prolonged QRS duration was associated with heterogeneous ventricular mechanical activation and reduced strain in the lateral and septal left ventricle walls. Degree of intraventricular dyssynchrony correlated with LVEF (r = -0.59, p <0.001), QRS duration (r = 0.74, p <0.001), and septal strain (r = 0.70, p <0.001). In conclusion, LV dysfunction and dyssynchrony were observed in patients with TOF and were associated with QRS duration. It was possible that abnormal LV mechanics in combination with RV dysfunction may explain the relation between QRS duration and adverse cardiac outcomes.

Neural Stem Cells Confer Unique Pinwheel Architecture to the Ventricular Surface in Neurogenic Regions of the Adult Brain

Neural stem cells (NSCs, B1 cells) are retained in the walls of the adult lateral ventricles but, unlike embryonic NSCs, are displaced from the ventricular zone (VZ) into the subventricular zone (SVZ) by ependymal cells. Apical and basal compartments, which in embryonic NSCs play essential roles in self-renewal and differentiation, are not evident in adult NSCs. Here we show that SVZ B1 cells in adult mice extend a minute apical ending to directly contact the ventricle and a long basal process ending on blood vessels. A closer look at the ventricular surface reveals a striking pinwheel organization specific to regions of adult neurogenesis. The pinwheel's core contains the apical endings of B1 cells and in its periphery two types of ependymal cells: multiciliated (E1) and a type (E2) characterized by only two cilia and extraordinarily complex basal bodies. These results reveal that adult NSCs retain fundamental epithelial properties, including apical and basal compartmentalization, significantly reshaping our understanding of this adult neurogenic niche.

A Dlx2- and Pax6-Dependent Transcriptional Code for Periglomerular Neuron Specification in the Adult Olfactory Bulb

Distinct olfactory bulb (OB) interneurons are thought to become specified depending on from which of the different subregions lining the lateral ventricle wall they originate, but the role of region-specific transcription factors (TFs) in the generation of OB interneurons diversity is still poorly understood. Despite the crucial roles of the Dlx family of TFs for patterning and neurogenesis in the ventral telencephalon during embryonic development, their role in adult neurogenesis has not yet been addressed. Here we show that in the adult brain, Dlx 1 and Dlx2 are expressed in progenitors of the lateral but not the dorsal subependymal zone (SEZ), thus exhibiting a striking regional specificity. Using retroviral vectors to examine the function of Dlx2 in a cell-autonomous manner, we demonstrate that this TF is necessary for neurogenesis of virtually all OB interneurons arising from the lateral SEZ. Beyond its function in generic neurogenesis, Dlx2 also plays a crucial role in neuronal subtype specification in the OB, promoting specification of adult-born periglomerular neurons (PGNs) toward a dopaminergic fate. Strikingly, Dlx2 requires interaction with Pax6, because Pax6 deletion blocks Dlx2-mediated PGN specification. Thus, Dlx2 wields a dual function by first instructing generic neurogenesis from adult precursors and subsequently specifying PGN subtypes in conjunction with Pax6.

Combined Therapeutic Strategy Using Erythropoietin and Mesenchymal Stem Cells Potentiates Neurogenesis after Transient Focal Cerebral Ischemia in Rats

Many studies showed beneficial effects of either erythropoietin (EPO) or mesenchymal stem cells (MSCs) treatment in cerebral ischemia. In addition to a neuroprotective role, not only EPO but also MSC favors neurogenesis and functional recovery. In an attempt to further improve postischemic tissue repair, we investigated the effect of a systemic administration of MSC, in the presence or not of EPO, on neurogenesis and functional recovery in a transient focal cerebral ischemia model in the adult rat. Twenty-four hours after ischemia, the rats were divided into four groups, namely vehicle, MSC, EPO, and MSC+EPO, and received a single intravenous injection of MSC (2 x 10(6) cells) and/or a repeated intraperitoneal administration of EPO (1,000 UI/kg) for 3 days. The lesion volume, the MSC outcome, neurogenesis, and functional recovery were assessed 51 days after ischemia. The results showed that cellular proliferation and neurogenesis were increased along the lateral ventricle wall in the MSC+EPO group, whereas no significant effect was observed in groups receiving MSC or EPO alone. This effect was accompanied by an improvement of mnesic performances. Mesenchymal stem cells expressing neuronal or glial markers were detected in the ischemic hemisphere. These results suggest that EPO could act in a synergistic way with MSC to potentiate the postischemic neurogenesis.

Early impairment of myocardial function in young patients with β‐thalassemia major

One of the chief causes of death in patients with beta-thalassemia major (TM) remains heart failure due to iron overload. We investigated possible differences in myocardial function between a population of young asymptomatic patients with TM and healthy controls all of whom underwent an echocardiographic study, including tissue Doppler (TDI) and strain imaging (SI) analysis and cardiac magnetic resonance imaging (MRI). 30 young asymptomatic patients with TM (16 taking deferoxamine and 14 taking deferiprone) and 30 healthy subjects underwent a cardiac MRI with T2* technique and an echocardiographic evaluation including systolic myocardial velocities (Sm), early (Em) and late (Am) diastolic velocities and systolic strain (S) at the level of basal segments of the lateral left ventricle (LV), interventricular septum (Septal) and lateral right ventricle (RV) wall. The differences in T2* values and echocardiographic parameters were also compared in patients with TM subgrouped according to iron chelation therapy. The following TDI and SI measures were lower in patients than in controls: LV-Sm (P < 0.05), S-LV (P < 0.001), Septal-Sm (P < 0.05), Septal-Em (P < 0.001), S-Septal (P < 0.001), RV-Sm (P < 0.001), RV-Em (P < 0.001), RV-Em/Am (P < 0.05) and S-RV (P < 0.05). Myocardial function was better in the patients receiving deferiprone than those receiving deferoxamine. T2* values were higher in controls than in patients with TM and in those treated with deferiprone than those treated with deferoxamine. MRI data well correlated with SI parameters. Study underlines that, even in a population of young, asymptomatic and well-chelated patients with TM, there is an impairment of myocardial function and that this condition could be easily detected by more advanced ultrasound techniques such as TDI and SI. The better indices of myocardial function in patients treated with deferiprone clearly needs confirmation from larger prospective studies.

Genetic manipulation of adult mouse neurogenic niches by in vivo electroporation

Targeted ectopic expression of genes in the adult brain is an invaluable approach for studying many biological processes. This can be accomplished by generating transgenic mice or by virally mediated gene transfer, but these methods are costly and labor intensive. We devised a rapid strategy that allows localized in vivo transfection of plasmid DNA within the adult neurogenic niches without detectable brain damage. Injection of plasmid DNA into the ventricular system or directly into the hippocampus of adult mice, followed by application of electrical current via external electrodes, resulted in transfection of neural stem or progenitor cells and mature neurons. We showed that this strategy can be used for both fate mapping and gain- or loss-of-function experiments. Using this approach, we identified an essential role for cadherins in maintaining the integrity of the lateral ventricle wall. Thus, in vivo electroporation provides a new approach to study the adult brain.

Novel Extracellular Matrix Structures in the Neural Stem Cell Niche Capture the Neurogenic Factor Fibroblast Growth Factor 2 from the Extracellular Milieu

The novel extracellular matrix structures called fractones are found in the lateral ventricle walls, the principal adult brain stem cell niche. By electron microscopy, fractones were shown to contact neural stem and progenitor cells (NSPC), suggesting a role in neurogenesis. Here, we investigated spatial relationships between proliferating NSPC and fractones and identified basic components and the first function of fractones. Using bromodeoxyuridine (BrdU) for birth-dating cells in the adult mouse lateral ventricle wall, we found most mitotic cells next to fractones, although some cells emerged next to capillaries. Like capillary basement membranes, fractones were immunoreactive for laminin beta1 and gamma1, collagen IV, nidogen, and perlecan, but not laminin-alpha1, in the adult rat, mouse, and human. Intriguingly, N-sulfate heparan sulfate proteoglycan (HSPG) immunoreactivity was restricted to fractone subpopulations and infrequent subependymal capillaries. Double immunolabel for BrdU and N-sulfate HSPG revealed preferential mitosis next to N-sulfate HSPG immunoreactive fractones. To determine whether N sulfate HSPG immunoreactivity within fractones reflects a potential for binding neurogenic growth factors, we identified biotinylated fibroblast growth factor 2 (FGF-2) binding sites in situ on frozen sections, and in vivo after intracerebroventricular injection of biotinylated FGF-2 in the adult rat or mouse. Both binding assays revealed biotinylated FGF-2 on fractone subpopulations and on infrequent subependymal capillaries. The binding of biotinylated FGF-2 was specific and dependent upon HSPG, as demonstrated in vitro and in vivo by inhibition with heparatinase and by the concomitant disappearance of N-sulfate HSPG immunoreactivity. These results strongly suggest that fractones promote growth factor activity in the neural stem cell niche.