Scientific Resources

Here we demonstrate,both in vivo and in vitro,that growth hormone (GH) mediates precursor cell activation in the subventricular zone (SVZ) of the aged (12-month-old) brain following exercise,and that GH signaling stimulates precursor activation to a similar extent to exercise. Our results reveal that both addition of GH in culture and direct intracerebroventricular infusion of GH stimulate neural precursor cells in the aged brain. In contrast,no increase in neurosphere numbers was observed in GH receptor null animals following exercise. Continuous infusion of a GH antagonist into the lateral ventricle of wild-type animals completely abolished the exercise-induced increase in neural precursor cell number. Given that the aged brain does not recover well after injury,we investigated the direct effect of exercise and GH on neural precursor cell activation following irradiation. This revealed that physical exercise as well as infusion of GH promoted repopulation of neural precursor cells in irradiated aged animals. Conversely,infusion of a GH antagonist during exercise prevented recovery of precursor cells in the SVZ following irradiation. View Publication

Since the discovery of neural stem cells (NSC) in the embryonic and adult mammalian central nervous system (CNS),there have been a growing numbers of tissue culture media and protocols to study and functionally characterize NSCs and its progeny in vitro. One of these culture systems introduced in 1992 is referred to as the Neurosphere Assay,and it has been widely used to isolate,expand,differentiate and even quantify NSC populations. Several years later because its application as a quantitative in vitro assay for measuring NSC frequency was limited,a new single-step semisolid based assay,the Neural Colony Forming Cell (NCFC) assay was developed to accurately measure NSC numbers. The NCFC assay allows the discrimination between NSCs and progenitors by the size of colonies they produce (i.e.,their proliferative potential). The evolution and continued improvements made to these tissue culture tools will facilitate further advances in the promising application of NSCs for therapeutic use. View Publication

Down syndrome cell adhesion molecule,or DSCAM,has been implicated in many neurodevelopmental processes including axon guidance,dendrite arborization,and synapse formation. Here we show that DSCAM plays an important role in regulating the morphogenesis of cortical pyramidal neurons in the mouse. We report that DSCAM expression is developmentally regulated and localizes to synaptic plasma membranes during a time of robust cortical dendrite arborization and spine formation. Analysis of mice that carry a spontaneous mutation in DSCAM (DSCAM(del17)) revealed gross morphological changes in brain size and shape in addition to subtle changes in cortical organization,volume,and lamination. Early postnatal mutant mice displayed a transient decrease in cortical thickness,but these reductions could not be attributed to changes in neuron production or cell death. DSCAM(del17) mutants showed temporary impairments in the branching of layer V pyramidal neuron dendrites at P10 and P17 that recovered to normal by adulthood. Defects in DSCAM(del17) dendrite branching correlated with a temporal increase in apical branch spine density and lasting changes in spine morphology. At P15 and P42,mutant mice displayed a decrease in the percentage of large,stable spines and an increase in the percentage of small,immature spines. Together,our findings suggest that DSCAM contributes to pyramidal neuron morphogenesis by regulating dendrite arborization and spine formation during cortical circuit development. View Publication

In the stem cell field there is a lack of non invasive and fast methods to identify stem cell's metabolic state,differentiation state and cell-lineage commitment. Here we describe a label-free method that uses NADH as an intrinsic biomarker and the Phasor approach to Fluorescence Lifetime microscopy to measure the metabolic fingerprint of cells. We show that different metabolic states are related to different cell differentiation stages and to stem cell bias to neuronal and glial fate,prior the expression of lineage markers. Our data demonstrate that the NADH FLIM signature distinguishes non-invasively neurons from undifferentiated neural progenitor and stem cells (NPSCs) at two different developmental stages (E12 and E16). NPSCs follow a metabolic trajectory from a glycolytic phenotype to an oxidative phosphorylation phenotype through different stages of differentiation. NSPCs are characterized by high free/bound NADH ratio,while differentiated neurons are characterized by low free/bound NADH ratio. We demonstrate that the metabolic signature of NPSCs correlates with their differentiation potential,showing that neuronal progenitors and glial progenitors have a different free/bound NADH ratio. Reducing conditions in NPSCs correlates with their neurogenic potential,while oxidative conditions correlate with glial potential. For the first time we show that FLIM NADH metabolic fingerprint provides a novel,and quantitative measure of stem cell potential and a label-free and non-invasive means to identify neuron- or glial- biased progenitors. View Publication

Glioblastoma multiforme is the most malignant type of primary brain tumor with a poor prognosis. These tumors consist of a heterogeneous population of malignant cells,including well-differentiated tumor cells and less differentiated cells with stem cell properties. These cancer stem cells,known as brain tumor initiating cells,likely contribute to glioma recurrence,as they are highly invasive,mobile,resistant to radiation and chemotherapy,and have the capacity to self-renew. Glioblastoma tumor cells release excitotoxic levels of glutamate,which may be a key process in the death of peritumoral neurons,formation of necrosis,local inflammation,and glioma-related seizures. Moreover,elevated glutamate levels in the tumor may act in paracrine and autocrine manner to activate glutamate receptors on glioblastoma tumor cells,resulting in proliferation and invasion. Using a previously described culturing condition that selectively promotes the growth of brain tumor initiating cells,which express the stem cell markers nestin and SOX-2,we characterize the expression of α-amino-3-hydroxy-5-methyl-4-isozolepropionic acid (AMPA)-type glutamate receptor subunits in brain tumor initiating cells derived from glioblastomas. Here we show for the first time that glioblastoma brain tumor initiating cells express high concentrations of functional calcium-permeable AMPA receptors,compared to the differentiated tumor cultures consisting of non-stem cells. Up-regulated calcium-permeable AMPA receptor expression was confirmed by immunoblotting,immunocytochemistry,and intracellular calcium imaging in response to specific agonists. Our findings raise the possibility that glutamate secretion in the GBM tumor microenvironment may stimulate brain tumor derived cancer stem cells. View Publication

Glioblastoma growth is driven by cancer cells that have stem cell properties,but molecular determinants of their tumorigenic behavior are poorly defined. In cancer,altered activity of the epigenetic modifiers Polycomb and Trithorax complexes may contribute to the neoplastic phenotype. Here,we provide the first mechanistic insights into the role of the Trithorax protein mixed lineage leukemia (MLL) in maintaining cancer stem cell characteristics in human glioblastoma. We found that MLL directly activates the Homeobox gene HOXA10. In turn,HOXA10 activates a downstream Homeobox network and other genes previously characterized for their role in tumorigenesis. The MLL-Homeobox axis we identified significantly contributes to the tumorigenic potential of glioblastoma stem cells. Our studies suggest a role for MLL in contributing to the epigenetic heterogeneity between tumor-initiating and non-tumor-initiating cells in glioblastoma. View Publication

We isolated neural stem cells/neural progenitors (NSC) from 1-day-old rat pups born to mothers fed diets that were deficient or supplemented with n-3 polyunsaturated fatty acids (PUFAs) and compared their proliferation and differentiation in vitro. The cells isolated from the n-3PUFA-deficient pups consistently proliferated more slowly than cells that were isolated from n-3PUFA-supplemented pups,despite the fact that both were cultured under the same conditions. The differences in the proliferation rates were evaluated up until 40 days of culture and were highly significant. When the cells were allowed to differentiate,the deficient cells exhibited a higher degree of neuronal maturation in response to the addition of PUFAs in the medium,as demonstrated by an increase in neurite length,whereas the neurons derived from the supplemented pups showed no change. This result was consistent,regardless of the age of the culture. The properties of the NSC were durably modified throughout the length of the culture,although the membrane phospholipid compositions were similar. We examined the differential expression of selected mRNAs and micro RNAs. We found significant differences in the gene expression of proliferating and differentiating cells,and a group of genes involved in neurogenesis was specifically modified by n-3 PUFA treatment. We conclude that n-3 PUFA levels in the maternal diet can induce persistent modifications of the proliferation and differentiation of NSCs and of their transcriptome. Therefore,the n-3 supply received in utero may condition on a long-term basis cell renewal in the brain. View Publication

Reversing brain degeneration and trauma lesions will depend on cell therapy. Our previous work identified neural precursor cells derived from the skeletal muscle of Nestin-GFP transgenic mice,but their identity,origin,and potential survival in the brain are only vaguely understood. In this work,we show that Nestin-GFP+ progenitor cells share morphological and molecular markers with NG2-glia,including NG2,PDGFRα,O4,NGF receptor (p75),glutamate receptor-1(AMPA),and A2B5 expression. Although these cells exhibit NG2,they do not express other pericyte markers,such as α-SMA or connexin-43,and do not differentiate into the muscle lineage. Patch-clamp studies displayed outward potassium currents,probably carried through Kir6.1 channels. Given their potential therapeutic application,we compared their abundance in tissues and concluded that skeletal muscle is the richest source of predifferentiated neural precursor cells. We found that these cells migrate toward the neurogenic subventricular zone displaying their typical morphology and nestin-GFP expression two weeks after brain injection. For translational purposes,we sought to identify these neural progenitor cells in wild-type species by developing a DsRed expression vector under Nestin-Intron II control. This approach revealed them in nonhuman primates and aging rodents throughout the lifespan. View Publication

BACKGROUND Neuronal stem cells (NSCs) are promising for neurointestinal disease therapy. Although NSCs have been isolated from intestinal musclularis,their presence in mucosa has not been well described. Mucosa-derived NSCs are accessible endoscopically and could be used autologously. Brain-derived Nestin-positive NSCs are important in endogenous repair and plasticity. The aim was to isolate and characterize mucosa-derived NSCs,determine their relationship to Nestin-expressing cells and to demonstrate their capacity to produce neuroglial networks in vitro and in vivo. METHODS Neurospheres were generated from periventricular brain,colonic muscularis (Musc),and mucosa-submucosa (MSM) of mice expressing green fluorescent protein (GFP) controlled by the Nestin promoter (Nestin-GFP). Neuronal stem cells were also grown as adherent colonies from intestinal mucosal organoids. Their differentiation potential was assessed using immunohistochemistry using glial and neuronal markers. Brain and gut-derived neurospheres were transplanted into explants of chick embryonic aneural hindgut to determine their fate. KEY RESULTS Musc- and MSM-derived neurospheres expressed Nestin and gave rise to cells of neuronal,glial,and mesenchymal lineage. Although Nestin expression in tissue was mostly limited to glia co-labelled with glial fibrillary acid protein (GFAP),neurosphere-derived neurons and glia both expressed Nestin in vitro,suggesting that Nestin+/GFAP+ glial cells may give rise to new neurons. Moreover,following transplantation into aneural colon,brain- and gut-derived NSCs were able to differentiate into neurons. CONCLUSIONS & INFERENCES Nestin-expressing intestinal NSCs cells give rise to neurospheres,differentiate into neuronal,glial,and mesenchymal lineages in vitro,generate neurons in vivo and can be isolated from mucosa. Further studies are needed for exploring their potential for treating neuropathies. View Publication

In the search for ways to combat degenerative neurological disorders,neurogenesis-stimulating factors are proving to be a promising area of research. In this study,we show that the hormonal factor prolactin (PRL) can activate a pool of latent precursor cells in the adult mouse hippocampus. Using an in vitro neurosphere assay,we found that the addition of exogenous PRL to primary adult hippocampal cells resulted in an approximate 50% increase in neurosphere number. In addition,direct infusion of PRL into the adult dentate gyrus also resulted in a significant increase in neurosphere number. Together these data indicate that exogenous PRL can increase hippocampal precursor numbers both in vitro and in vivo. Conversely,PRL null mice showed a significant reduction (approximately 80%) in the number of hippocampal-derived neurospheres. Interestingly,no deficit in precursor proliferation was observed in vivo,indicating that in this situation other niche factors can compensate for a loss in PRL. The PRL loss resulted in learning and memory deficits in the PRL null mice,as indicated by significant deficits in the standard behavioral tests requiring input from the hippocampus. This behavioral deficit was rescued by direct infusion of recombinant PRL into the hippocampus,indicating that a lack of PRL in the adult mouse hippocampus can be correlated with impaired learning and memory. View Publication

Differentiation of pluripotent and lineage restricted stem cells such as neural stem cells (NSCs) was studied on conducting substrates of various nature without perturbation of the genome with exogenous genetic material or chemical stimuli. Primary mouse adult neural stem cells (NSCs) and P19 pluripotent embryonal (P19 EC) carcinoma cells were used. Expression levels of neuronal markers β-III-tubulin and neurofilament were evaluated by immunochemistry and flow cytometry. It was shown that the ability of the substrate to induce differentiation directly correlated with its conductivity. Conducting substrates (conducting oxides or doped pi-conjugated organic polymers) with different morphology,structure,and conductivity mechanisms all promoted differentiation of NSC and P19 cells into neuronal lineage to a similar degree without use of additional factors such as poly-L-ornithine coating or retinoic acid,as verified by their morphology and upregulation of the neuronal markers but not astrocyte marker GFAP. However,substrates with low conductance below ca. 10(-4) S cm(-2) did not show this ability. Morphology of differentiating cells was visualized by atomic force microscopy. NSCs cells increased β-III-tubulin expression by 95% and P19 cells by over 30%. Our results suggest that the substrate conductivity is a key factor governing the cell fate. Differentiation of P19 cells into neuronal lineage on conducting substrates was attributed to downregualtion of Akt signaling pathway and increase in expression of dual oxidase 1 (DUOX 1). View Publication

The integration of microscale engineering,microfluidics,and AC electrokinetics such as dielectrophoresis has generated novel microsystems that enable quantitative analysis of cellular phenotype,function,and physiology. These systems are increasingly being used to assess diverse cell types,such as stem cells,so it becomes critical to thoroughly evaluate whether the systems themselves impact cell function. For example,engineered microsystems have been utilized to investigate neural stem/progenitor cells (NSPCs),which are of interest due to their potential to treat CNS disease and injury. Analysis by dielectrophoresis (DEP) microsystems determined that unlabeled NSPCs with distinct fate potential have previously unrecognized distinguishing electrophysiological characteristics,suggesting that NSPCs could be isolated by DEP microsystems without the use of cell type specific labels. To gauge the potential impact of DEP sorting on NSPCs,we investigated whether electric field exposure of varying times affected survival,proliferation,or fate potential of NSPCs in suspension. We found short-term DEP exposure (1 min or less) had no effect on NSPC survival,proliferation,or fate potential revealed by differentiation. Moreover,NSPC proliferation (measured by DNA synthesis and cell cycle kinetics) and fate potential were not altered by any length of DEP exposure (up to 30 min). However,lengthy exposure (textgreater5 min) to frequencies near the crossover frequency (50-100 kHz) led to decreased survival of NSPCs (maximum ∼30% cell loss after 30 min). Based on experimental observations and mathematical simulations of cells in suspension,we find that frequencies near the crossover frequency generate an induced transmembrane potential that results in cell swelling and rupture. This is in contrast to the case for adherent cells since negative DEP frequencies lower than the crossover frequency generate the highest induced transmembrane potential and damage for these cells. We clarify contrasting effects of DEP on adherent and suspended cells,which are related to the cell position within the electric field and the strength of the electric field at specific distances from the electrodes. Modeling of electrode configurations predicts optimal designs to induce cell movement by DEP while limiting the induced transmembrane potential. We find DEP electric fields are not harmful to stem cells in suspension at short exposure times,thus providing a basis for developing DEP-based applications for stem cells. View Publication