Neural stem cells in the adult olfactory bulb core generate mature neurons in vivo.

Although previous studies suggest that neural stem cells (NSCs) exist in the adult olfactory bulb (OB), their location, identity, and capacity to generate mature neurons in vivo has been little explored. Here, we injected enhanced green fluorescent protein (EGFP)-expressing retroviral particles into the OB core of adult mice to label dividing cells and to track the differentiation/maturation of any neurons they might generate. EGFP-labeled cells initially expressed adult NSC markers on days 1 to 3 postinjection (dpi), including Nestin, GLAST, Sox2, Prominin-1, and GFAP. EGFP+ -doublecortin (DCX) cells with a migratory morphology were also detected and their abundance increased over a 7-day period. Furthermore, EGFP-labeled cells progressively became NeuN+ neurons, they acquired neuronal morphologies, and they became immunoreactive for OB neuron subtype markers, the most abundant representing calretinin expressing interneurons. OB-NSCs also generated glial cells, suggesting they could be multipotent in vivo. Significantly, the newly generated neurons established and received synaptic contacts, and they expressed presynaptic proteins and the transcription factor pCREB. By contrast, when the retroviral particles were injected into the subventricular zone (SVZ), nearly all (98%) EGFP+ -cells were postmitotic when they reached the OB core, implying that the vast majority of proliferating cells present in the OB are not derived from the SVZ. Furthermore, we detected slowly dividing label-retaining cells in this region that could correspond to the population of resident NSCs. This is the first time NSCs located in the adult OB core have been shown to generate neurons that incorporate into OB circuits in vivo.

Distinct Effects of BDNF and NT-3 on the Dendrites and Presynaptic Boutons of Developing Olfactory Bulb GABAergic Interneurons In Vitro.

Brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) are known to regulate neuronal morphology and the formation of neural circuits, yet the neuronal targets of each neurotrophin are still to be defined. To address how these neurotrophins regulate the morphological and synaptic differentiation of developing olfactory bulb (OB) GABAergic interneurons, we analyzed the effect of BDNF and NT-3 on GABA+-neurons and on different subtypes of these neurons: tyrosine hydroxylase (TH+); calretinin (Calr+); calbindin (Calb+); and parvalbumin (PVA+). These cells were generated from cultured embryonic mouse olfactory bulb neural stem cells (eOBNSCs) and after 14 days in vitro (DIV), when the neurons expressed TrkB and/or TrkC receptors, BDNF and NT-3 did not significantly change the number of neurons. However, long-term BDNF treatment did produce a longer total dendrite length and/or more dendritic branches in all the interneuron populations studied, except for PVA+-neurons. Similarly, BDNF caused an increase in the cell body perimeter in all the interneuron populations analyzed, except for PVA+-neurons. GABA+- and TH+-neurons were also studied at 21 DIV, when BDNF produced significantly longer neurites with no clear change in their number. Notably, these neurons developed synaptophysin+ boutons at 21 DIV, the size of which augmented significantly following exposure to either BDNF or NT-3. Our results show that in conditions that maintain neuronal survival, BDNF but not NT-3 promotes the morphological differentiation of developing OB interneurons in a cell-type-specific manner. In addition, our findings suggest that BDNF and NT-3 may promote synapse maturation by enhancing the size of synaptic boutons.

N370S-GBA1 mutation causes lysosomal cholesterol accumulation in Parkinson's disease.

BACKGROUND: Heterozygous mutations in the GBA1 gene, which encodes the lysosomal enzyme ß-glucocerebrosidase-1, increase the risk of developing Parkinson's disease, although the underlying mechanisms remain unclear. The aim of this study was to explore the impact of the N370S-GBA1 mutation on cellular homeostasis and vulnerability in a patient-specific cellular model of PD. METHODS: We isolated fibroblasts from 4 PD patients carrying the N370S/wild type GBA1 mutation and 6 controls to study the autophagy-lysosome pathway, endoplasmic reticulum stress, and Golgi apparatus structure by Western blot, immunofluorescence, LysoTracker and Filipin stainings, mRNA analysis, and electron microscopy. We evaluated cell vulnerability by apoptosis, reactive oxygen species and mitochondrial membrane potential with flow cytometry. RESULTS: The N370S mutation produced a significant reduction in ß-glucocerebrosidase-1 protein and enzyme activity and ß-glucocerebrosidase-1 retention within the endoplasmic reticulum, which interrupted its traffic to the lysosome. This led to endoplasmic reticulum stress activation and triggered unfolded protein response and Golgi apparatus fragmentation. Furthermore, these alterations resulted in autophagosome and p62/SQSTM1 accumulation. This impaired autophagy was a result of dysfunctional lysosomes, indicated by multilamellar body accumulation probably caused by increased cholesterol, enlarged lysosomal mass, and reduced enzyme activity. This phenotype impaired the removal of damaged mitochondria and reactive oxygen species production and enhanced cell death. CONCLUSIONS: Our results support a connection between the loss of ß-glucocerebrosidase-1 function, cholesterol accumulation, and the disruption of cellular homeostasis in GBA1-PD. Our work reveals new insights into the cellular pathways underlying PD pathogenesis, providing evidence that GBA1-PD shares common features with lipid-storage diseases. © 2017 International Parkinson and Movement Disorder Society.

APOE ε4 allele, along with G206D-PSEN1 mutation, alters mitochondrial networks and their degradation in Alzheimer's disease.

Introduction: Alzheimer's disease remains the most common neurodegenerative disorder, depicted mainly by memory loss and the presence in the brain of senile plaques and neurofibrillary tangles. This disease is related to several cellular alterations like the loss of synapses, neuronal death, disruption of lipid homeostasis, mitochondrial fragmentation, or raised oxidative stress. Notably, changes in the autophagic pathway have turned out to be a key factor in the early development of the disease. The aim of this research is to determine the impact of the APOE allele ε4 and G206D-PSEN1 on the underlying mechanisms of Alzheimer's disease. Methods: Fibroblasts from Alzheimer's patients with APOE 3/4 + G206D-PSEN1 mutation and homozygous APOE ε4 were used to study the effects of APOE polymorphism and PSEN1 mutation on the autophagy pathway, mitochondrial network fragmentation, superoxide anion levels, lysosome clustering, and p62/SQSTM1 levels. Results: We observed that the APOE allele ε4 in homozygosis induces mitochondrial network fragmentation that correlates with an increased colocalization with p62/SQSTM1, probably due to an inefficient autophagy. Moreover, G206D-PSEN1 mutation causes an impairment of the integrity of mitochondrial networks, triggering high superoxide anion levels and thus making APOE 3/4 + PSEN1 fibroblasts more vulnerable to cell death induced by oxidative stress. Of note, PSEN1 mutation induces accumulation and clustering of lysosomes that, along with an increase of global p62/SQSTM1, could compromise lysosomal function and, ultimately, its degradation. Conclusion: The findings suggest that all these modifications could eventually contribute to the neuronal degeneration that underlies the pathogenesis of Alzheimer's disease. Further research in this area may help to develop targeted therapies for the treatment of Alzheimer's disease.

Brain IGF-I regulates LTP, spatial memory, and sexual dimorphic behavior.

Insulin-like growth factor-I (IGF-I) exerts multiple actions, yet the role of IGF-I from different sources is poorly understood. Here, we explored the functional and behavioral consequences of the conditional deletion of Igf-I in the nervous system (Igf-I Δ/Δ), and demonstrated that long-term potentiation was impaired in hippocampal slices. Moreover, Igf-I Δ/Δ mice showed spatial memory deficits in the Morris water maze, and the significant sex-dependent differences displayed by Igf-I Ctrl/Ctrl mice disappeared in Igf-I Δ/Δ mice in the open field and rota-rod tests. Brain Igf-I deletion disorganized the granule cell layer of the dentate gyrus (DG), and it modified the relative expressions of GAD and VGLUT1, which are preferentially localized to inhibitory and excitatory presynaptic terminals. Furthermore, Igf-I deletion altered protein modules involved in receptor trafficking, synaptic proteins, and proteins that functionally interact with estrogen and androgen metabolism. Our findings indicate that brain IGF-I is crucial for long-term potentiation, and that it is involved in the regulation of spatial memory and sexual dimorphic behaviors, possibly by maintaining the granule cell layer structure and the stability of synaptic-related protein modules.

Tbr1 Misexpression Alters Neuronal Development in the Cerebral Cortex.

Changes in the transcription factor (TF) expression are critical for brain development, and they may also underlie neurodevelopmental disorders. Indeed, T-box brain1 (Tbr1) is a TF crucial for the formation of neocortical layer VI, and mutations and microdeletions in that gene are associated with malformations in the human cerebral cortex, alterations that accompany autism spectrum disorder (ASD). Interestingly, Tbr1 upregulation has also been related to the occurrence of ASD-like symptoms, although limited studies have addressed the effect of increased Tbr1 levels during neocortical development. Here, we analysed the impact of Tbr1 misexpression in mouse neural progenitor cells (NPCs) at embryonic day 14.5 (E14.5), when they mainly generate neuronal layers II-IV. By E18.5, cells accumulated in the intermediate zone and in the deep cortical layers, whereas they became less abundant in the upper cortical layers. In accordance with this, the proportion of Sox5+ cells in layers V-VI increased, while that of Cux1+ cells in layers II-IV decreased. On postnatal day 7, fewer defects in migration were evident, although a higher proportion of Sox5+ cells were seen in the upper and deep layers. The abnormal neuronal migration could be partially due to the altered multipolar-bipolar neuron morphologies induced by Tbr1 misexpression, which also reduced dendrite growth and branching, and disrupted the corpus callosum. Our results indicate that Tbr1 misexpression in cortical NPCs delays or disrupts neuronal migration, neuronal specification, dendrite development and the formation of the callosal tract. Hence, genetic changes that provoke ectopic Tbr1 upregulation during development could provoke cortical brain malformations.

Morphological Diversity of Calretinin Interneurons Generated From Adult Mouse Olfactory Bulb Core Neural Stem Cells.

Neural stem cells (NSCs) in the olfactory bulb (OB) core can generate mature interneurons in the adult mice brain. The vast majority of these adult generated cells express the calcium-binding protein Calretinin (CalR), and they migrate towards different OB layers. However, these cells have yet to be fully characterized and hence, to achieve this we injected retroviral particles expressing GFP into the OB core of adult animals and found that the CalR+ neurons generated from NSCs mainly migrate to the granule cell layer (GCL) and glomerular layer (GL) in similar proportions. In addition, since morphology and function are closely related, we used three-dimensional imaging techniques to analyze the morphology of these adult born cells, describing new subtypes of CalR+ interneurons based on their dendritic arborizations and projections, as well as their localization in the GCL or GL. We also show that the migration and morphology of these newly generated neurons can be altered by misexpressing the transcription factor Tbr1 in the OB core. Therefore, the morphology acquired by neurons located in a specific OB layer is the result of a combination of both extrinsic (e.g., layer allocation) and intrinsic mechanisms (e.g., transcription factors). Defining the cellular processes and molecular mechanisms that govern adult neurogenesis might help better understand brain circuit formation and plasticity, as well as eventually opening the way to develop strategies for brain repair.

SoxD genes are required for adult neural stem cell activation.

The adult neurogenic niche in the hippocampus is maintained through activation of reversibly quiescent neural stem cells (NSCs) with radial glia-like morphology (RGLs). Here, we show that the expression of SoxD transcription factors Sox5 and Sox6 is enriched in activated RGLs. Using inducible deletion of Sox5 or Sox6 in the adult mouse brain, we show that both genes are required for RGL activation and the generation of new neurons. Conversely, Sox5 overexpression in cultured NSCs interferes with entry in quiescence. Mechanistically, expression of the proneural protein Ascl1 (a key RGL regulator) is severely downregulated in SoxD-deficient RGLs, and Ascl1 transcription relies on conserved Sox motifs. Additionally, loss of Sox5 hinders the RGL activation driven by neurogenic stimuli such as environmental enrichment. Altogether, our data suggest that SoxD genes are key mediators in the transition of adult RGLs from quiescence to an activated mitotic state under physiological situations.

Generation of a set of isogenic iPSC lines carrying all APOE genetic variants (Ɛ2/Ɛ3/Ɛ4) and knock-out for the study of APOE biology in health and disease.

APOE genotype is the strongest genetic risk factor for Alzheimer's Disease (AD). The low degree of homology between mouse and human APOE is a concerning issue in preclinical models currently used to study the role of this gene in AD pathophysiology. A key objective of ADAPTED (Alzheimer's Disease Apolipoprotein Pathology for Treatment Elucidation and Development) project was to generate in vitro models that better recapitulate human APOE biology. We describe a new set of induced pluripotent stem cells (iPSC) lines carrying common APOE variants (Ɛ2, Ɛ3, and Ɛ3/Ɛ4) and a knock-out isogenic to the parental APOE Ɛ4/Ɛ4 line (UKBi011-A).

A collection of three integration-free iPSCs derived from old male and female healthy subjects.

Here, we present the characterization of three iPSC lines derived from dermal fibroblasts of old healthy subjects. Fibroblasts were reprogrammed using Sendai viral vectors encoding OCT4, SOX2, KLF4 and c-MYC. The iPSCs expressed endogenous pluripotency markers, could generate the three germ layers (ectoderm, mesoderm and endoderm), maintained a stable karyotype, and were free from Sendai vectors and reprogramming factors. These integration-free iPSCs can serve for establishing control cell cultures in studies searching for phenotypes and mechanisms that could potentially be dysregulated in degenerative diseases.

An integration-free iPSC line, ICCSICi007-A, derived from a female Alzheimer's disease patient with the APOE-ε4/ε4 alleles.

The epsilon4 (ε4) allele of the APOE gene, which encodes the apolipoprotein E4 (ApoE4), is the strongest genetic risk factor known for late-onset Alzheimer´s disease (LOAD). Here, we present the characterization of an iPSC line generated from dermal fibroblasts of a female AD patient using Sendai viral vectors encoding the transcription factors OCT4, SOX2, KLF4 and c-MYC. The iPSCs maintained the original genotype, a normal karyotype, were free from Sendai viral vectors and reprogramming factors, presented a normal morphology, expressed endogenous pluripotency markers, and could be differentiated into ectodermal, mesodermal and endodermal cells, confirming its pluripotency.

Generation of an integration-free iPSC line, ICCSICi006-A, derived from a male Alzheimer's disease patient carrying the PSEN1-G206D mutation.

The familial form of Alzheimer's disease (FAD), which is caused by mutations in PRESENILIN 1 (PSEN1) and amyloid precursor protein (APP) genes, represents less than 5% of all AD cases and has an early-onset. We report the generation and characterization of an iPSC line derived from a FAD patient carrying the PSEN1-G206D mutation. The iPSC line maintained the original genotype, a normal karyotype, was free from Sendai viral vectors and reprogramming factors (OCT4, SOX2, KLF4 and c-MYC), presented a typical morphology, expressed endogenous pluripotency markers, and could be differentiated into ectodermal, mesodermal and endodermal cells, confirming its pluripotency.

Generation of an integration-free iPSC line, ICCSICi005-A, derived from a Parkinson's disease patient carrying the L444P mutation in the GBA1 gene.

The L444P mutation in the GBA1 gene which encodes ß-glucocerebrosidase-1, is a major risk factor for developing Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We report the generation and characterization of an induced pluripotent stem cell (iPSC) line derived from a female PD patient carrying the L444P/wt mutation. The iPSC line presented a normal morphology, expressed endogenous pluripotency markers, could be differentiated into endodermal, mesodermal and ectodermal cells, was free from Sendai vectors and reprogramming factors, had a normal karyotype and maintained the original GBA1 genotype. Thus, this iPSC line can serve to establish cellular models of PD.

A collection of four integration-free iPSC lines derived from diagnosed sporadic Alzheimer's disease patients with different APOE alleles.

Genetic polymorphism of apolipoprotein E (APOE) confers differential susceptibility to late-onset Alzheimer's disease (LOAD). The ε3 allele of APOE, the most common isoform, does not represent a risk factor for LOAD. In contrast, the ε4 allele is the strongest genetic risk factor for this disease. Here, we present the characterization of four iPSC lines generated from dermal fibroblasts of diagnosed sporadic AD patients using Sendai viral vectors encoding OCT4, SOX2, KLF4 and c-MYC. The iPSCs expressed endogenous pluripotency markers, could be differentiated into the three germ layers, maintained the original genotypes, and were free from Sendai vectors and reprogramming factors.

A collection of integration-free iPSCs derived from Parkinson's disease patients carrying mutations in the GBA1 gene.

Mutations in the GBA1 gene, which encodes the lysosomal enzyme Glucocerebrosidase1 are major risk factors for Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We have generated induced pluripotent stem cells (iPSCs) from fibroblasts of four PD patients carrying the N370S/wt or the L444P/wt heterozygous mutations in GBA1. The iPSCs presented a normal morphology, expressed endogenous pluripotency markers and could be differentiated into endodermal, mesodermal and ectodermal cells. These iPSCs were free from Sendai viral vectors and reprogramming factors, had a normal karyotype and maintained the original GBA1 genotype.

Cholesterol and multilamellar bodies: Lysosomal dysfunction in GBA-Parkinson disease.

Lipid and cholesterol metabolism might play a role in the pathogenesis of Parkinson disease (PD). However, the association between cholesterol and PD is not clearly established. Cholesterol accumulation is closely related to the expression of multilamellar bodies (MLBs). Also, cholesterol controls autophagosome transport. Thus, impaired cholesterol and autophagosome trafficking might lead to robust autophagic vacuole accumulation. Our recent work provides the first evidence that the presence of the N370S GBA mutation produces an accumulation of cholesterol, which alters autophagy-lysosome function with the appearance of MLBs, rendering the cell more vulnerable and sensitive to apoptosis.

Treatment of deep wound infections after spinal fusion with a vacuum-assisted device in patients with spinal cord injury.

Postoperative wound infection is a severe complication after spinal instrumentation, especially in a patient with spinal injury. We used vacuum-assisted wound closure (VAC) in two patients with spinal cord injury, who presented deep wound infection after spinal instrumentation and were treated with an aggressive irrigation and debridement procedure. Three and four weeks after VAC application, the hardware was completely covered by granulation tissue and a secondary closure was undertaken. No significant complications were observed. Six months after secondary closure, the wounds remained healed, no signs of instrumentation loosening, haloing or lysis around the instrumentation were observed, and patients had completed their rehabilitation program and were discharged from hospital. Vacuum assisted wound closure appears as an excellent option in the treatment of deep wound infections after spinal instrumentation in patients with spinal cord injury.

Osteoinductive effect of bone bank allografts on human osteoblasts in culture.

Incorporation of a human bone allograft requires osteoclast activity and growth of recipient osteoblasts. The aim of this work was to study the effects produced by autoclavated and -80 degrees C frozen bone allografts on osteoblast proliferation and synthesis of interleukin 6 (IL6), activator of bone resorption, aminoterminal propeptide of procollagen I (PINP), marker of bone matrix formation, and osteoprotegerin (OPG), inhibitor of osteoclast activity and differentiation. Allografts were obtained from human femoral heads. Human osteoblasts were cultured in the presence (problem group) or in the absence (control group) of allografts during 15 days. Allografts produced a decrease in osteoblast proliferation in the first week of the experiment, and an increase in IL6 mRNA, both at 3 h and 2 days, and an increase in the IL6 released to the culture medium the second day of the experiment. We found a decrease in OPG released to the culture on the 2nd and fourth days. These results suggest an increase in bone resorption and a decrease in bone formation in the first week of the experiment. In the second week, allografts produced an increase in osteoblast proliferation and PINP release to the culture medium, indicating an increase in bone formation; an increase in OPG released to the culture medium, which would indicate a decrease in bone resorption; and a decrease in IL6, indicating a decrease in bone resorption stimulation. These results demonstrate that autoclavated and -80 degrees C frozen bone allografts produce in bone environment changes that regulate their own incorporation to the recipient bone.