Deletion of the Autism-Associated Protein SHANK3 Abolishes Structural Synaptic Plasticity after Brain Trauma.

Autism spectrum disorders (ASDs) are characterized by repetitive behaviors and impairments of sociability and communication. About 1% of ASD cases are caused by mutations of SHANK3, a major scaffolding protein of the postsynaptic density. We studied the role of SHANK3 in plastic changes of excitatory synapses within the central nervous system by employing mild traumatic brain injury (mTBI) in WT and Shank3 knockout mice. In WT mice, mTBI triggered ipsi- and contralateral loss of hippocampal dendritic spines and excitatory synapses with a partial recovery over time. In contrast, no significant synaptic alterations were detected in Shank3∆11-/- mice, which showed fewer dendritic spines and excitatory synapses at baseline. In line, mTBI induced the upregulation of synaptic plasticity-related proteins Arc and p-cofilin only in WT mice. Interestingly, microglia proliferation was observed in WT mice after mTBI but not in Shank3∆11-/- mice. Finally, we detected TBI-induced increased fear memory at the behavioral level, whereas in Shank3∆11-/- animals, the already-enhanced fear memory levels increased only slightly after mTBI. Our data show the lack of structural synaptic plasticity in Shank3 knockout mice that might explain at least in part the rigidity of behaviors, problems in adjusting to new situations and cognitive deficits seen in ASDs.

SHANK2 Mutations Result in Dysregulation of the ERK1/2 Pathway in Human Induced Pluripotent Stem Cells-Derived Neurons and Shank2(-/-) Mice.

SHANK2 (ProSAP1) is a postsynaptic scaffolding protein of excitatory synapses in the central nervous system and implicated in the development of autism spectrum disorders (ASD). Patients with mutations in SHANK2 show autism-like behaviors, developmental delay, and intellectual disability. We generated human induced pluripotent stem cells (hiPSC) from a patient carrying a heterozygous deletion of SHANK2 and from the unaffected parents. In patient hiPSCs and derived neurons SHANK2 mRNA and protein expression was reduced. During neuronal maturation, a reduction in growth cone size and a transient increase in neuronal soma size were observed. Neuronal proliferation was increased, and apoptosis was decreased in young and mature neurons. Additionally, mature patient hiPSC-derived neurons showed dysregulated excitatory signaling and a decrease of a broad range of signaling molecules of the ERK-MAP kinase pathway. These findings could be confirmed in brain samples from Shank2(-/-) mice, which also showed decreased mGluR5 and phospho-ERK1/2 expression. Our study broadens the current knowledge of SHANK2-related ASD. We highlight the importance of excitatory-inhibitory balance and mGluR5 dysregulation with disturbed downstream ERK1/2 signaling in ASD, which provides possible future therapeutic strategies for SHANK2-related ASD.

A serum microRNA sequence reveals fragile X protein pathology in amyotrophic lateral sclerosis.

Knowledge about converging disease mechanisms in the heterogeneous syndrome amyotrophic lateral sclerosis (ALS) is rare, but may lead to therapies effective in most ALS cases. Previously, we identified serum microRNAs downregulated in familial ALS, the majority of sporadic ALS patients, but also in presymptomatic mutation carriers. A 5-nucleotide sequence motif (GDCGG; D = G, A or U) was strongly enriched in these ALS-related microRNAs. We hypothesized that deregulation of protein(s) binding predominantly to this consensus motif was responsible for the ALS-linked microRNA fingerprint. Using microRNA pull-down assays combined with mass spectrometry followed by extensive biochemical validation, all members of the fragile X protein family, FMR1, FXR1 and FXR2, were identified to directly and predominantly interact with GDCGG microRNAs through their structurally disordered RGG/RG domains. Preferential association of this protein family with ALS-related microRNAs was confirmed by in vitro binding studies on a transcriptome-wide scale. Immunohistochemistry of lumbar spinal cord revealed aberrant expression level and aggregation of FXR1 and FXR2 in C9orf72- and FUS-linked familial ALS, but also patients with sporadic ALS. Further analysis of ALS autopsies and induced pluripotent stem cell-derived motor neurons with FUS mutations showed co-aggregation of FXR1 with FUS. Hence, our translational approach was able to take advantage of blood microRNAs to reveal CNS pathology, and suggests an involvement of the fragile X-related proteins in familial and sporadic ALS already at a presymptomatic stage. The findings may uncover disease mechanisms relevant to many patients with ALS. They furthermore underscore the systemic, extra-CNS aspect of ALS.

Autism-associated SHANK3 mutations impair maturation of neuromuscular junctions and striated muscles.

Heterozygous mutations of the gene encoding the postsynaptic protein SHANK3 are associated with syndromic forms of autism spectrum disorders (ASDs). One of the earliest clinical symptoms in SHANK3-associated ASD is neonatal skeletal muscle hypotonia. This symptom can be critical for the early diagnosis of affected children; however, the mechanism mediating hypotonia in ASD is not completely understood. Here, we used a combination of patient-derived human induced pluripotent stem cells (hiPSCs), Shank3Δ11(-/-) mice, and Phelan-McDermid syndrome (PMDS) muscle biopsies from patients of different ages to analyze the role of SHANK3 on motor unit development. Our results suggest that the hypotonia in SHANK3 deficiency might be caused by dysfunctions in all elements of the voluntary motor system: motoneurons, neuromuscular junctions (NMJs), and striated muscles. We found that SHANK3 localizes in Z-discs in the skeletal muscle sarcomere and co-immunoprecipitates with α-ACTININ. SHANK3 deficiency lead to shortened Z-discs and severe impairment of acetylcholine receptor clustering in hiPSC-derived myotubes and in muscle from Shank3Δ11(-/-) mice and patients with PMDS, indicating a crucial role for SHANK3 in the maturation of NMJs and striated muscle. Functional motor defects in Shank3Δ11(-/-) mice could be rescued with the troponin activator Tirasemtiv that sensitizes muscle fibers to calcium. Our observations give insight into the function of SHANK3 besides the central nervous system and imply potential treatment strategies for SHANK3-associated ASD.

FUS-mediated regulation of acetylcholine receptor transcription at neuromuscular junctions is compromised in amyotrophic lateral sclerosis.

Neuromuscular junction (NMJ) disruption is an early pathogenic event in amyotrophic lateral sclerosis (ALS). Yet, direct links between NMJ pathways and ALS-associated genes such as FUS, whose heterozygous mutations cause aggressive forms of ALS, remain elusive. In a knock-in Fus-ALS mouse model, we identified postsynaptic NMJ defects in newborn homozygous mutants that were attributable to mutant FUS toxicity in skeletal muscle. Adult heterozygous knock-in mice displayed smaller neuromuscular endplates that denervated before motor neuron loss, which is consistent with 'dying-back' neuronopathy. FUS was enriched in subsynaptic myonuclei, and this innervation-dependent enrichment was distorted in FUS-ALS. Mechanistically, FUS collaborates with the ETS transcription factor ERM to stimulate transcription of acetylcholine receptor genes. Co-cultures of induced pluripotent stem cell-derived motor neurons and myotubes from patients with FUS-ALS revealed endplate maturation defects due to intrinsic FUS toxicity in both motor neurons and myotubes. Thus, FUS regulates acetylcholine receptor gene expression in subsynaptic myonuclei, and muscle-intrinsic toxicity of ALS mutant FUS may contribute to dying-back motor neuronopathy.

Synaptic FUS Localization During Motoneuron Development and Its Accumulation in Human ALS Synapses.

Mutations in the fused in Sarcoma (FUS) gene induce cytoplasmic FUS aggregations, contributing to the neurodegenerative disease amyotrophic lateral sclerosis (ALS) in certain cases. While FUS is mainly a nuclear protein involved in transcriptional processes with limited cytoplasmic functions, it shows an additional somatodendritic localization in neurons. In this study we analyzed the localization of FUS in motoneuron synapses, these being the most affected neurons in ALS, using super-resolution microscopy to distinguish between the pre- and postsynaptic compartments. We report a maturation-based variation of FUS localization in rodent synapses where a predominantly postsynaptic FUS was observed in the early stages of synaptic development, while in mature synapses the protein was entirely localized in the axonal terminal. Likewise, we also show that at the synapse of human motoneurons derived from induced pluripotent stem cells of a healthy control, FUS is mainly postsynaptic in the early developmental stages. In motoneurons derived from ALS patients harboring a very aggressive juvenile FUS mutation, increased synaptic accumulation of mutated FUS was observed. Moreover increased aggregation of other synaptic proteins Bassoon and Homer1 was also detected in these abnormal synapses. Having demonstrated changes in the FUS localization during synaptogenesis, a role of synaptic FUS in both dendritic and axonal cellular compartments is probable, and we propose a gain-of-toxic function due to the synaptic aggregation of mutant FUS in ALS.

Retinoic acid worsens ATG10-dependent autophagy impairment in TBK1-mutant hiPSC-derived motoneurons through SQSTM1/p62 accumulation.

Mutations in the TBK1 (TANK binding kinase 1) gene are causally linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). TBK1 phosphorylates the cargo receptors OPTN and SQSTM1 regulating a critical step in macroautophagy/autophagy. Disruption of the autophagic flux leads to accumulation of cytosolic protein aggregates, which are a hallmark of ALS. hiPSC-derived TBK1-mutant motoneurons (MNs) showed reduced TBK1 levels and accumulation of cytosolic SQSTM1-positive aggresomes. By screening a library of nuclear-receptor-agonists for modifiers of the SQSTM1 aggregates, we identified 4-hydroxy(phenyl)retinamide (4HPR) as a potent modifier exerting detrimental effects on mutant-TBK1 motoneurons fitness exacerbating the autophagy overload. We have shown by TEM that TBK1-mutant motoneurons accumulate immature phagophores due a failure in the elongation phase, and 4HPR further worsens the burden of dysfunctional phagophores. 4HPR-increased toxicity was associated with the upregulation of SQSTM1 in a context of strongly reduced ATG10, while rescue of ATG10 levels abolished 4HPR toxicity. Finally, we showed that 4HPR leads to a downregulation of ATG10 and to an accumulation of SQSTM1+ aggresomes also in hiPSC-derived C9orf72-mutant motoneurons. Our data show that cultured human motoneurons harboring mutations in TBK1 gene display typical ALS features, like decreased viability and accumulation of cytosolic SQSTM1-positive aggresomes. The retinoid 4HPR appears a strong negative modifier of the fitness of TBK1 and C9orf72-mutant MNs, through a pathway converging on the mismatch of initiated autophagy and ATG10 levels. Thus, autophagy induction appears not to be a therapeutic strategy for ALS unless the specific underlying pathway alterations are properly addressed. Abbreviations: 4HPR: 4-hydroxy(phenyl)retinamide; AKT: AKT1 serine/threonine kinase 1; ALS: amyotrophic lateral sclerosis; ATG: autophagy related; AVs: autophagic vesicle; C9orf72: chromosome 9 open reading frame 72; CASP3: caspase 3; CHAT: choline O-acetyltransferase; CYCS: cytochrome c, somatic; DIV: day in vitro; FTD: frontotemporal dementia; FUS: FUS RNA binding protein; GFP: green fluorescent protein; hiPSCs: human induced pluripotent stem cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MNs: motoneurons; mRFP: monomeric red fluorescent protein; MTOR: mechanistic target of rapamycin kinase; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; RARA: retinoic acid receptor alpha; SLC18A3/VACHT: solute carrier family 18 (vesicular acetylcholine transporter), member 3; SQSTM1/p62: sequestosome 1; TBK1: TANK binding kinase 1; TEM: transmission electron microscopy.

NEK1 loss-of-function mutation induces DNA damage accumulation in ALS patient-derived motoneurons.

Mutations in genes coding for proteins involved in DNA damage response (DDR) and repair, such as C9orf72 and FUS (Fused in Sarcoma), are associated with neurodegenerative diseases and lead to amyotrophic lateral sclerosis (ALS). Heterozygous loss-of-function mutations in NEK1 (NIMA-related kinase 1) have also been recently found to cause ALS. NEK1 codes for a multifunctional protein, crucially involved in mitotic checkpoint control and DDR. To resolve pathological alterations associated with NEK1 mutation, we compared hiPSC-derived motoneurons carrying a NEK1 mutation with mutant C9orf72 and wild type neurons at basal level and after DNA damage induction. Motoneurons carrying a C9orf72 mutation exhibited cell specific signs of increased DNA damage. This phenotype was even more severe in NEK1c.2434A>T neurons that showed significantly increased DNA damage at basal level and impaired DDR after induction of DNA damage in an maturation-dependent manner. Our results provide first mechanistic insight in pathophysiological alterations induced by NEK1 mutations and point to a converging pathomechanism of different gene mutations causative for ALS. Therefore, our study contributes to the development of novel therapeutic strategies to reduce DNA damage accumulation in neurodegenerative diseases and ALS.

ALS-causing mutations differentially affect PGC-1α expression and function in the brain vs. peripheral tissues.

BACKGROUND: Monogenetic forms of amyotrophic lateral sclerosis (ALS) offer an opportunity for unraveling the molecular mechanisms underlying this devastating neurodegenerative disorder. In order to identify a link between ALS-related metabolic changes and neurodegeneration, we investigated whether ALS-causing mutations interfere with the peripheral and brain-specific expression and signaling of the metabolic master regulator PGC (PPAR gamma coactivator)-1α (PGC-1α). METHODS: We analyzed the expression of PGC-1α isoforms and target genes in two mouse models of familial ALS and validated the stimulated PGC-1α signaling in primary adipocytes and neurons of these animal models and in iPS derived motoneurons of two ALS patients harboring two different frame-shift FUS/TLS mutations. RESULTS: Mutations in SOD1 and FUS/TLS decrease Ppargc1a levels in the CNS whereas in muscle and brown adipose tissue Ppargc1a mRNA levels were increased. Probing the underlying mechanism in neurons, we identified the monocarboxylate lactate as a previously unrecognized potent and selective inducer of the CNS-specific PGC-1α isoforms. Lactate also induced genes like brain-derived neurotrophic factor, transcription factor EB and superoxide dismutase 3 that are down-regulated in PGC-1α deficient neurons. The lactate-induced CNS-specific PGC-1α signaling system is completely silenced in motoneurons derived from induced pluripotent stem cells obtained from two ALS patients harboring two different frame-shift FUS/TLS mutations. CONCLUSION: ALS mutations increase the canonical PGC-1α system in the periphery while inhibiting the CNS-specific isoforms. We identify lactate as an inducer of the neuronal PGC-1α system directly linking brain metabolism and neuroprotection. Changes in the PGC-1α system might be involved in the ALS accompanied metabolic changes and in neurodegeneration.

4-Aminopyridine Induced Activity Rescues Hypoexcitable Motor Neurons from Amyotrophic Lateral Sclerosis Patient-Derived Induced Pluripotent Stem Cells.

Despite decades of research on amyotrophic lateral sclerosis (ALS), there is only one approved drug, which minimally extends patient survival. Here, we investigated pathophysiological mechanisms underlying ALS using motor neurons (MNs) differentiated from induced pluripotent stem cells (iPSCs) derived from ALS patients carrying mutations in FUS or SOD1. Patient-derived MNs were less active and excitable compared to healthy controls, due to reduced Na(+) /K(+) ratios in both ALS groups accompanied by elevated potassium channel (FUS) and attenuated sodium channel expression levels (FUS, SOD1). ALS iPSC-derived MNs showed elevated endoplasmic reticulum stress (ER) levels and increased caspase activation. Treatment with the FDA approved drug 4-Aminopyridine (4AP) restored ion-channel imbalances, increased neuronal activity levels and decreased ER stress and caspase activation. This study provides novel pathophysiological data, including a mechanistic explanation for the observed hypoexcitability in patient-derived MNs and a new therapeutic strategy to provide neuroprotection in MNs affected by ALS. Stem Cells 2016;34:1563-1575.

FUS Mislocalization and Vulnerability to DNA Damage in ALS Patients Derived hiPSCs and Aging Motoneurons.

Mutations within the FUS gene (Fused in Sarcoma) are known to cause Amyotrophic Lateral Sclerosis (ALS), a neurodegenerative disease affecting upper and lower motoneurons. The FUS gene codes for a multifunctional RNA/DNA-binding protein that is primarily localized in the nucleus and is involved in cellular processes such as splicing, translation, mRNA transport and DNA damage response. In this study, we analyzed pathophysiological alterations associated with ALS related FUS mutations (mFUS) in human induced pluripotent stem cells (hiPSCs) and hiPSC derived motoneurons. To that end, we compared cells carrying a mild or severe mFUS in physiological- and/or stress conditions as well as after induced DNA damage. Following hyperosmolar stress or irradiation, mFUS hiPS cells recruited significantly more cytoplasmatic FUS into stress granules accompanied by impaired DNA-damage repair. In motoneurons wild-type FUS was localized in the nucleus but also deposited as small punctae within neurites. In motoneurons expressing mFUS the protein was additionally detected in the cytoplasm and a significantly increased number of large, densely packed FUS positive stress granules were seen along neurites. The amount of FUS mislocalization correlated positively with both the onset of the human disease (the earlier the onset the higher the FUS mislocalization) and the maturation status of the motoneurons. Moreover, even in non-stressed post-mitotic mFUS motoneurons clear signs of DNA-damage could be detected. In summary, we found that the susceptibility to cell stress was higher in mFUS hiPSCs and hiPSC derived motoneurons than in controls and the degree of FUS mislocalization correlated well with the clinical severity of the underlying ALS related mFUS. The accumulation of DNA damage and the cellular response to DNA damage stressors was more pronounced in post-mitotic mFUS motoneurons than in dividing hiPSCs suggesting that mFUS motoneurons accumulate foci of DNA damage, which in turn might be directly linked to neurodegeneration.

Stepwise acquirement of hallmark neuropathology in FUS-ALS iPSC models depends on mutation type and neuronal aging.

Autosomal-dominant mutations within the gene FUS (fused in sarcoma) are responsible for 5% of familial cases of amyotrophic lateral sclerosis (ALS). The FUS protein is physiologically mainly located in the nucleus, while cytoplasmic FUS aggregates are pathological hallmarks of FUS-ALS. Data from non-neuronal cell models and/or models using heterologous expression of FUS mutants suggest cytoplasmic FUS translocation as a pivotal initial event which leads to neurodegeneration depending on a second hit. Here we present the first human model of FUS-ALS using patient-derived neurons carrying endogenous FUS mutations leading to a benign (R521C) or a more severe clinical phenotype (frameshift mutation R495QfsX527). We thereby showed that the severity of the underlying FUS mutation determines the amount of cytoplasmic FUS accumulation and cellular vulnerability to exogenous stress. Cytoplasmic FUS inclusions formed spontaneously depending on both, severity of FUS mutation and neuronal aging. These aggregates showed typical characteristics of FUS-ALS including methylated FUS. Finally, neurodegeneration was not specific to layer V cortical neurons perfectly in line with the current model of disease spreading in ALS. Our study highlights the value and usefulness of patient-derived cell models in FUS-ALS.

Super-Resolution Microscopy Reveals Presynaptic Localization of the ALS/FTD Related Protein FUS in Hippocampal Neurons.

Fused in Sarcoma (FUS) is a multifunctional RNA-/DNA-binding protein, which is involved in the pathogenesis of the neurodegenerative disorders amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). A common hallmark of these disorders is the abnormal accumulation of mutated FUS protein in the cytoplasm. Under normal conditions FUS is confined to the nuclear compartment, in neurons, however, additional somatodendritic localization can be observed. In this study, we carefully analyzed the subcellular localization of endogenous FUS at synaptic sites of hippocampal neurons which are among the most affected cell types in FTD with FUS pathology. We could confirm a strong nuclear localization of FUS as well as its prominent and widespread neuronal expression throughout the adult and developing rat brain, particularly in the hippocampus, the cerebellum and the outer layers of the cortex. Intriguingly, FUS was also consistently observed at synaptic sites as detected by neuronal subcellular fractionation as well as by immunolabeling. To define a pre- and/or postsynaptic localization of FUS, we employed super-resolution fluorescence localization microscopy. FUS was found to be localized within the axon terminal in close proximity to the presynaptic vesicle protein Synaptophysin1 and adjacent to the active zone protein Bassoon, but well separated from the postsynaptic protein PSD-95. Having shown the presynaptic localization of FUS in the nervous system, a novel extranuclear role of FUS at neuronal contact sites has to be considered. Since there is growing evidence that local presynaptic translation might also be an important mechanism for plasticity, FUS - like the fragile X mental retardation protein FMRP - might act as one of the presynaptic RNA-binding proteins regulating this machinery. Our observation of presynaptic FUS should foster further investigations to determine its role in neurodegenerative diseases such as ALS and FTD.

B-scan ultrasonographic monitoring of orthotopic xenografted plexiform neurofibroma in mice.

BACKGROUND/AIM: Xenografted benign tumours in immunodeficient mice provide an in vivo model to study tumour biology and the effect of agents on tumour growth. Conventionally, these small grafts can only be monitored upon sacrificing the animals. We evaluated ultrasound biomicroscopy for monitoring such grafts in vivo. MATERIALS AND METHODS: Small fragments (<10 mm(3)) of a plexiform neurofibroma obtained from patients with established diagnosis of neurofibromatosis type-1 (NF1) were orthotopically-xenografted onto the sciatic nerve of immunodeficient mice and monitored using a high-resolution in vivo micro-imaging system. RESULTS: Grafts were identified in most cases and were distinguished from the surrounding inflammatory host tissues by detailed ultrasonographic signals. Graft sizes could be calculated precisely from serial scan sections and monitored during the whole course of drug treatment. CONCLUSION: High frequency sonographic measurement is a superior non-invasive method for monitoring small grafts of slowly growing benign tumours in mice in vivo, e.g. plexiform neurofibroma, and is especially suitable for tracing the effects of drugs at multiple time-points, thus allowing a very cost-effective follow-up.

Effects of pigment epithelium derived factor (PEDF) on malignant peripheral nerve sheath tumours (MPNSTs).

Neurofibromatosis type 1 (NF1) is an inherited genetic disease affecting 1 in 3,500 individuals. A prominent feature of NF1 is the formation of benign tumours of the peripheral nerve sheath (neurofibromas). However, these can become malignant and form highly metastatic malignant peripheral nerve sheath tumours (MPNST), which are usually fatal despite aggressive surgery, chemotherapy, and radiotherapy. Recent studies have shown that pigment epithelium-derived factor (PEDF) can induce differentiation and inhibit angiogenesis in several kinds of tumours. The present study was designed to determine the in vitro and in vivo effects of PEDF on MPNST angiogenesis and tumour growth. PEDF inhibited proliferation and augmented apoptosis in S462 MPNST cells after 48 h of treatment in culture. In xenografts of S462 MPNST cells in athymic nude mice, PEDF suppressed MPNST tumour burden, due mainly to inhibition of angiogenesis. These results demonstrate for the first time inhibitory effects of PEDF on the growth of human MPNST via induction of anti-angiogenesis and apoptosis. Our results suggest that PEDF could be a novel approach for future therapeutic purposes against MPNST.

The dynactin p150 subunit: cell biology studies of sequence changes found in ALS/MND and Parkinsonian syndromes.

The dynactin p150glued subunit, encoded by the gene DCTN1 is part of the dynein-dynactin motor protein complex responsible for retrograde axonal transport. This subunit is a candidate modifier for neurodegenerative diseases, in particular motoneuron and extrapyramidal diseases. Based on an extensive screening effort of all 32 exons in more than 2,500 ALS/MND patients, patients suffering from Parkinsonian Syndromes and controls, we investigated 24 sequence variants of p150 in cell-based studies. We used both non-neuronal cell lines and primary rodent spinal motoneurons and report on cell biological abnormalities in five of these sequence alterations and also briefly report on the clinical features. Our results suggest the presence of biological changes caused by some p150 mutants pointing to a potential pathogenetic significance as modifier of the phenotype of the human disease.

Intranasal delivery of neural stem/progenitor cells: a noninvasive passage to target intracerebral glioma.

Stem cell-based therapies for neurological disorders, including brain tumors, advance continuously toward clinical trials. Optimized cell delivery to the central nervous system remains a challenge since direct intracerebral injection is an invasive method with low transplantation efficiency. We investigated the feasibility of intranasal administration of neural stem/progenitor cells (NSPCs) as an alternative, noninvasive, and direct passage for the delivery of stem cells to target malignant gliomas. Tumor-targeting and migratory pathways of murine and human NSPCs were investigated by intravital magnetic resonance imaging and in histological time course analyses in the intracerebral U87, NCE-G55T2, and syngenic Gl261 glioblastoma models. Intranasally administered NSPCs displayed a rapid, targeted tumor tropism with significant numbers of NSPCs accumulating specifically at the intracerebral glioma site within 6 hours after intranasal delivery. Histological time series analysis revealed that NSPCs migrated within the first 24 hours mainly via olfactory pathways but also by systemic distribution via the microvasculature of the nasal mucosa. Intranasal application of NSPCs leads to a rapid, targeted migration of cells toward intracerebral gliomas. The directional distribution of cells accumulating intra- and peritumorally makes the intranasal delivery of NSPCs a promising noninvasive and convenient alternative delivery method for the treatment of malignant gliomas with the possibility of multiple dosing regimens.

Cancer stem cell-like cells derived from malignant peripheral nerve sheath tumors.

This study aims to examine whether or not cancer stem cells exist in malignant peripheral nerve sheath tumors (MPNST). Cells of established lines, primary cultures and freshly dissected tumors were cultured in serum free conditions supplemented with epidermal and fibroblast growth factors. From one established human MPNST cell line, S462, cells meeting the criteria for cancer stem cells were isolated. Clonal spheres were obtained, which could be passaged multiple times. Enrichment of stem cell-like cells in these spheres was also supported by increased expression of stem cell markers such as CD133, Oct4, Nestin and NGFR, and decreased expression of mature cell markers such as CD90 and NCAM. Furthermore, cells of these clonal S462 spheres differentiated into Schwann cells, smooth muscle/fibroblast and neurons-like cells under specific differentiation-inducing cultural conditions. Finally, subcutaneous injection of the spheres into immunodeficient nude mice led to tumor formation at a higher rate compared to the parental adherent cells (66% versus 10% at 2.5 × 10(5)). These results provide evidence for the existence of cancer stem cell-like cells in malignant peripheral nerve sheath tumors.

Imatinib mesylate (Glivec) inhibits Schwann cell viability and reduces the size of human plexiform neurofibroma in a xenograft model.

Plexiform neurofibromas (PNF), one of the major features of neurofibromatosis type 1 (NF1), are characterized by complex cellular composition and mostly slow but variable growth patterns. In this study, we examined the effect of imatinib mesylate, a receptor tyrosine kinase inhibitor, on PNF-derived Schwann cells and PNF tumour growth in vitro and in vivo. In vitro, PNF-derived primary Schwann cells express platelet-derived growth factors receptors (PDGFR) alpha and beta, both targets of imatinib, and cell viability was reduced by imatinib mesylate, with 50% inhibition concentration (IC(50)) of 10 microM. For in vivo studies, PNF tumour fragments xenografted onto the sciatic nerve of athymic nude mice were first characterized. The tumours persisted for at least 63 days and maintained typical characteristics of PNFs such as complex cellular composition, low proliferation rate and angiogenesis. A transient enlargement of the graft size was due to inflammation by host cells. Treatment with imatinib mesylate at a daily dose of 75 mg/kg for 4 weeks reduced the graft size by an average of 80% (n = 8), significantly different from the original sizes within the group and from sizes of the grafts in 11 untreated mice in the control group (P < 0.001). We demonstrated that grafting human PNF tumour fragments into nude mice provides an adequate in vivo model for drug testing. Our results provide in vivo and in vitro evidence for efficacy of imatinib mesylate for PNF.

Observations on the function of nuclear factor kappa B (NF-kappaB) in the survival of adult primary sensory neurons after nerve injury.

Peripheral nerve transections cause much more neuronal death in embryonic and neonatal dorsal root ganglia (DRG) than in adult DRG. Here we used transgenic approaches to examine the hypothesis that NF-kappaB is an important intrinsic factor of adult DRG neurons for their in vivo capacity to survive after nerve injury. We generated transgenic mice expressing the NF-kappaB super-inhibitor (IkappaBalpha-SI), a multi-mutant form of IkappaBalpha, specifically in adult neurons. Adult DRG neurons in these transgenic animals are not abnormally susceptible to apoptosis after peripheral nerve injury, although there is a significant inhibition in the ability of NF-kappaB to translocate into their nucleus. We investigated the observed lack of NF-kappaB neuroprotective function at the level of NF-kappaB transcriptional activity using transgenic NF-kappaB/LacZ reporter mice. We show that the expression of the NF-kappaB reporter transgene is restricted in naïve and injured DRG neurons. However, NF-kappaB transcriptional activity in adult DRG neurons is evident upon exposure to Trichostatin A (TSA) which is a specific inhibitor of histone deacetylases. Taken together our results illustrate that the functions of NF-kappaB are limited in adult primary sensory neurons due to a transcriptional repression mechanism mediated by histone deacetylases, and that intrinsic neuroprotective factors other than NF-kappaB are responsible for the resistance of adult DRG neurons to apoptosis in response to nerve injury.