Development of a SERS strategy to overcome the nanoparticle stabilisation effect in serum-containing samples: Application to the quantification of dopamine in the culture medium of PC-12 cells.

The analysis of serum samples by surface-enhanced Raman spectroscopy (SERS) has gained ground over the last few years. However, the stabilisation of colloids by the proteins contained in these samples has restricted their use in common practice, unless antibodies or aptamers are used. Therefore, this work was dedicated to the development of a SERS methodology allowing the analysis of serum samples in a simple and easy-to-implement way. This approach was based on the pre-aggregation of the colloid with a salt solution. Gold nanoparticles (AuNPs) were used as the SERS substrate and, owing to its physiopathological importance, dopamine was chosen as a model to implement the SERS approach. The presence of this neurotransmitter could be determined in the concentration range 0.5-50 ppm (2.64-264 µM) in the culture medium of PC-12 cells, with a R2 of 0.9874, and at even lower concentrations (0.25 ppm, 1.32 µM) in another matrix containing fewer proteins. Moreover, the effect of calcium and potassium on the dopamine exocytosis from PC-12 cells was studied. Calcium was shown to have a predominant and dose-dependant effect. Finally, PC-12 cells were exposed to dexamethasone in order to increase their biosynthesis and release of dopamine. This increase was monitored with the developed SERS approach.

HDAC7 inhibition resets STAT3 tumorigenic activity in human glioblastoma independently of EGFR and PTEN: new opportunities for selected targeted therapies.

To date, the mutational status of EGFR and PTEN has been shown as relevant for favoring pro- or anti-tumor functions of STAT3 in human glioblastoma multiforme (GBM). We have screened genomic data from 154 patients and have identified a strong positive correlation between STAT3 and HDAC7 expression. In the current work we show the existence of a subpopulation of patients overexpressing HDAC7 and STAT3 that has particularly poor clinical outcome. Surprisingly, the somatic mutation rate of both STAT3 and HDAC7 was insignificant in GBM comparing with EGFR, PTEN or TP53. Depletion of HDAC7 in a range of GBM cells induced the expression of tyrosine kinase JAK1 and the tumor suppressor AKAP12. Both proteins synergistically sustained the activity of STAT3 by inducing its phosphorylation (JAK1) and protein expression (AKAP12). In absence of HDAC7, activated STAT3 was responsible for significant imbalance of secreted pro-/anti-angiogenic factors. This inhibited the migration and sprouting of endothelial cells in paracrine fashion in vitro as well as angiogenesis in vivo. In a murine model of GBM, induced HDAC7-silencing decreased the tumor burden by threefold. The current data show for the first time that silencing HDAC7 can reset the tumor suppressor activity of STAT3, independently of the EGFR/PTEN/TP53 background of the GBM. This effect could be exploited to overcome tumor heterogeneity and provide a new rationale behind the development of specific HDAC7 inhibitors for clinical use.

Glioblastoma Circulating Cells: Reality, Trap or Illusion?

Metastases are the hallmark of cancer. This event is in direct relationship with the ability of cancer cells to leave the tumor mass and travel long distances within the bloodstream and/or lymphatic vessels. Glioblastoma multiforme (GBM), the most frequent primary brain neoplasm, is mainly characterized by a dismal prognosis. The usual fatal issue for GBM patients is a consequence of local recurrence that is observed most of the time without any distant metastases. However, it has recently been documented that GBM cells could be isolated from the bloodstream in several studies. This observation raises the question of the possible involvement of glioblastoma-circulating cells in GBM deadly recurrence by a "homing metastasis" process. Therefore, we think it is important to review the already known molecular mechanisms underlying circulating tumor cells (CTC) specific properties, emphasizing their epithelial to mesenchymal transition (EMT) abilities and their possible involvement in tumor initiation. The idea is here to review these mechanisms and speculate on how relevant they could be applied in the forthcoming battles against GBM.

Human cytomegalovirus and primary intracranial tumours: frequency of tumour infection and lack of correlation with systemic immune anti-viral responses.

AIMS: Human cytomegalovirus (HCMV) is a ubiquitous beta human herpesvirus able to influence infected cell survival and proliferation and to modulate the host immune response. As there is accumulating evidence that HCMV is detected in primary intracranial astrocytic tumours, in this study we looked for the presence of HCMV in intracranial tumours and tried to correlate this eventual presence with the anti-HCMV systemic immunoreactivity and with the detection of HCMV in peripheral blood. METHODS: In this study, we analysed 43 glioblastomas (GBM), 14 oligodendrogliomas (OL) and 20 meningiomas (MG) by immunofluorescence (IF) targeting HCMV immediate early antigen (IE1) and by nested PCR (nPCR) amplifying HCMV glycoprotein B (gB). RESULTS: Detection of IE1 by IF showed the presence of HCMV in 70% of GBM, 57% of OL and 85% of MG, in contrast to gB nPCR, which detected HCMV in only 50% of GBM, 38% of OL and 46% of MG. Unexpectedly, HCMV DNA and antigens were detected within GBM, OL and MG of patients that exhibit negative viral serology. More surprisingly, PCR on the peripheral blood did not detect HCMV in patients with a HCMV-positive tumour. CONCLUSIONS: Our results are in agreement with previous observations demonstrating HCMV in glial tumours and highlight the presence of HCMV in meningiomas. We also showed that anti-HCMV specific systemic immunoreactivity and detection of HCMV in peripheral blood are not predictive of HCMV presence in primary intracranial tumours.

Expression pattern of synaptic vesicle protein 2 (SV2) isoforms in patients with temporal lobe epilepsy and hippocampal sclerosis.

AIMS: Synaptic vesicle proteins 2 (SV2) are neuronal vesicles membrane glycoproteins that appear as important targets in the treatment of partial and generalized epilepsies. Therefore, we analysed the expression of SV2 isoforms in the hippocampus of patients with temporal lobe epilepsy (TLE). METHODS: SV2A, SV2B and SV2C immunostaining and QuantiGene branched DNA assay were performed on biopsies from 31 consecutive TLE patients with mesial temporal sclerosis (MTS) and compared with 10 autopsy controls. SV2 expression was further compared with Timm's staining, and synaptophysin, Zinc transporter 3 (ZnT3), dynorphin, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter (VGAT) expression. RESULTS: In TLE patients, SV2A and SV2B expression was decreased in areas of synaptic loss. SV2C, which is weakly expressed or absent in the hippocampus of controls, was overexpressed in 10/11 cases with classical MTS1A and mossy fibre sprouting but not in cases with other types of MTS. SV2C staining was located in the inner molecular layer of the dentate gyrus and colocalized with dynorphin, ZnT3 and VGLUT1, suggesting selective expression in presynaptic glutamatergic Zn(2+) -rich terminals of abnormal sprouting fibres. SV2 expression patterns correlated with histological subtypes of MTS, but not with clinical features or therapeutic regimens in this patient cohort. CONCLUSION: In classical MTS1A, the expression of SV2 isoforms is altered with a marked decrease of SV2A and SV2B paralleling synaptic loss and a selective increase of SV2C in sprouting mossy fibres. These findings suggest a different physiology of sprouting synapses and the possibility to target them with SV2C-specific strategies.

The susceptibility of the knee extensors to eccentric exercise-induced muscle damage is not affected by leg dominance but by exercise order.

The aims of this study were first to compare the response of dominant and non-dominant legs to eccentric exercise and second, to examine whether there is an effect of exercise order on the magnitude of symptoms associated with intense eccentric protocols. Eighteen young men performed three sets of 30 maximal eccentric isokinetic (60° s(-1)) contractions of the knee extensors (range of motion, ROM: 0°-100°, 0 = full extension) using either dominant or non-dominant leg. They repeated a similar eccentric bout using the contralateral leg 6 weeks later. The sequence of leg's use was allocated to create equally balanced groups. Four indirect markers of muscle damage including subjective pain intensity, maximal isometric strength, muscle stiffness and plasma creatine kinase (CK) activity were measured before and 24 h after exercise. All markers changed significantly following the eccentric bout performed either by dominant or non-dominant legs, but no significant difference was observed between legs. Interestingly, the comparison between the first and second eccentric bouts revealed that muscle soreness (-42%, P<0.001), CK activity (-62%, P<0.05) and strength loss (-54%, P<0.01) were significantly lower after the second bout. This study suggests that leg dominance does not influence the magnitude of exercise-induced muscle damage and supports for the first time the existence of a contralateral protection against exercise-induced muscle damage in the lower limbs.

Muscle fatigue experienced during maximal eccentric exercise is predictive of the plasma creatine kinase (CK) response.

Unaccustomed eccentric exercise may cause skeletal muscle damage with an increase in plasma creatine kinase (CK) activity. Although the wide variability among individuals in CK response to standardized lengthening contractions has been well described, the reasons underlying this phenomenon have not yet been understood. Therefore, this study investigated a possible correlation of the changes in muscle damage indirect markers after an eccentric exercise with the decline in muscle performance during the exercise. Twenty-seven healthy untrained male subjects performed three sets of 30 maximal isokinetic eccentric contractions of the knee extensors. The muscular work was recorded using an isokinetic dynamometer to assess muscle fatigue by means of various fatigue indices. Plasma CK activity, muscle soreness, and stiffness were measured before (pre) and one day after (post) exercise. The eccentric exercise bout induced significant changes of the three muscle damage indirect markers. Large inter-subject variability was observed for all criteria measured. More interestingly, the log (CK(post) /CK(pre)) and muscle stiffness appeared to be closely correlated with the relative work decrease (r = 0.84, r(2) = 0.70 and r = 0.75, r(2) = 0.56, respectively). This is the first study to propose that the muscle fatigue profile during maximal eccentric protocol could predict the magnitude of the symptoms associated with muscle damage in humans.

Wnt1 and BMP2: two factors recruiting multipotent neural crest progenitors isolated from adult bone marrow.

Recent studies have shown that neural crest-derived progenitor cells can be found in diverse mammalian tissues including tissues that were not previously shown to contain neural crest derivatives, such as bone marrow. The identification of those "new" neural crest-derived progenitor cells opens new strategies for developing autologous cell replacement therapies in regenerative medicine. However, their potential use is still a challenge as only few neural crest-derived progenitor cells were found in those new accessible locations. In this study, we developed a protocol, based on wnt1 and BMP2 effects, to enrich neural crest-derived cells from adult bone marrow. Those two factors are known to maintain and stimulate the proliferation of embryonic neural crest stem cells, however, their effects have never been characterized on neural crest cells isolated from adult tissues. Using multiple strategies from microarray to 2D-DIGE proteomic analyses, we characterized those recruited neural crest-derived cells, defining their identity and their differentiating abilities.

Neuregulin-1 modulates the differentiation of neural stem cells in vitro through an interaction with the Swi/Snf complex.

The neuregulin-1 (Nrg-1) gene is translated into several protein isoforms, which are either secreted or membrane-anchored. In vitro, neural stem cells (NSC) express mainly the cystein-rich-domain NRG (CRD-NRG) isoform, a membrane-anchored type III form. This isoform exhibits a cystein-rich-domain, which constitutes a second transmembrane domain and can be cleaved to release both a signaling EGF-containing domain (ECD) at the cell surface and an intracellular domain (ICD). The main goal of this paper was to determine the exact role of ECD and ICD in NSC survival and differentiation. Using an siRNA approach, we demonstrated that CRD-NRG inhibition was followed by a decrease in NSC proliferation and of neuronal or oligodendroglial differentiation. Overexpression of ICD but not ECD was followed by a decrease in NSC proliferation and an increase in neuronal and oligodendroglial differentiation. Moreover, we showed that ICD physically interacted in cultured NSC with BRM and BAF57, two members of the Swi/Snf remodeling complex, and that ICD stimulation of neuronal cell differentiation is dependent on the presence of BAF57.

[Adult neurogenesis or the falling of a dogma]. / La neurogenèse adulte ou l'histoire d'un dogme qui s'écroule.

The history of sciences is characterized by major discoveries, but also by challenges of theories or dogma previously established and accepted by everybody. One of the recent examples illustrating such a questioning relates to the demonstration of the persistence of a cerebral neurogenesis in the adult brain, including in human. This adult neurogenesis is however limited, both in space (it concerns only the subventricular zone and the gyrus dentatus in the hippocampus) and the type of newly-formed neurons (interneurones which most of them are GABAergic and present respectively in the olfactive bulb and CA1 area of the hippocampus). Moreover, this neurogenesis does not seem to be recruited after a brain lesion, a situation which explains why functional recovery when it is observed remains a consequence of brain plasticity. We thus legitimately address the question about the physiological role of this adult brain neurogenesis as well as a possible implication in the aetiology of various neurological disorders, like the neurodegenerative diseases or epilepsy, but also in psychiatric diseases like depression.

[Glioblastoma, an example of translational research?]. / Les glioblastomes, un exemple de recherche translationnelle?

Among patients which develop glioblastoma multiform (GBM), recurrence is the rule despite continuous progress in surgery, radiotherapy and chemotherapy. In the adult, GBM is the most frequent and most aggressive tumour of the Central Nervous System. A better understanding of the mechanisms by which these tumours relapse could promote the use of preventive therapy and could increase patients' survival. GBM stem cells have been recently described and it was demonstrated that they are specifically implied in the experimental tumorigenesis. It is thus very attractive to speculate on a possible relationship between these GBM stem cells and the neural stem cells which are persisting in the neurogenic zones of the adult brain. In this review, we formulate and discuss the hypothesis by which, in a patient with GBM, malignant stem cells might be present in the neurogenic zones, away from the tumour mass. This hypothesis could explain the tumour relapse observed after the first treatments.

Kinetic properties of the alpha2 homo-oligomeric glycine receptor impairs a proper synaptic functioning.

Ionotropic glycine receptors (GlyRs) are present in the central nervous system well before the establishment of synaptic contacts. Immature nerve cells are known, at least in the spinal cord, to express alpha2 homomeric GlyRs, the properties of which are relatively unknown compared to those of the adult synaptic form of the GlyR (mainly alpha1/beta heteromeres). Here, the kinetics properties of GlyRs at the single-channel level have been recorded in real-time by means of the patch-clamp technique in the outside-out configuration coupled with an ultra-fast flow application system (< 100 micros). Recordings were performed on chinese hamster ovary (CHO) cells stably transfected with the alpha2 GlyR subunit. We show that the onset, the relaxation and the desensitisation of alpha2 homomeric GlyR-mediated currents are slower by one or two orders of magnitude compared to synaptic mature GlyRs and to other ligand-gated ionotropic channels involved in fast synaptic transmission. First latency analysis performed on single GlyR channels revealed that their slow activation time course was due to delayed openings. When synaptic release of glycine was mimicked (1 mM glycine; 1 ms pulse duration), the opening probability of alpha2 homomeric GlyRs was low (P(o) approximately = 0.1) when compared to mature synaptic GlyRs (Po = 0.9). This low Po is likely to be a direct consequence of the relatively slow activation kinetics of alpha2 homomeric GlyRs when compared to the activation kinetics of mature alpha1/beta GlyRs. Such slow kinetics suggest that embryonic alpha2 homomeric GlyRs cannot be activated by fast neurotransmitter release at mature synapses but rather could be suited for a non-synaptic paracrine-like release of agonist, which is known to occur in the embryo.

Regulation of neural markers nestin and GFAP expression by cultivated bone marrow stromal cells.

Bone marrow stromal cells can differentiate into many types of mesenchymal cells, i.e. osteocyte, chondrocyte and adipocyte, but can also differentiate into non-mesenchymal cells, i.e. neural cells under appropriate in vivo experimental conditions (Kopen et al., 1999; Brazelton et al., 2000; Mezey et al., 2000). This neural phenotypic plasticity allows us to consider the utilization of mesenchymal stem cells as cellular material in regenerative medicine. In this study, we demonstrate that cultured adult rat stromal cells can express nestin, an intermediate filament protein predominantly expressed by neural stem cells. Two factors contribute to the regulation of nestin expression by rat stromal cells: serum in the culture medium inhibits nestin expression and a threshold number of passages must be reached below which nestin expression does not occur. Only nestin-positive rat stromal cells are able to form spheres when they are placed in the culture conditions used for neural stem cells. Likewise, only nestin-positive stromal cells are able to differentiate into GFAP (glial fibrillary acidic protein)-positive cells when they are co-cultivated with neural stem cells. We thus demonstrated that adult rat stromal cells in culture express nestin in absence of serum after passaging the cells at least ten times, and we suggest that nestin expression by these cells might be a prerequisite for the acquisition of the capacity to progress towards the neural lineage.

[What are the therapeutic hopes for stem cell in neurological diseases?]. / Quels espoirs thérapeutiques pour les cellules souches dans les maladies neurologiques?

For several years, in Parkinson's disease patients, immature neuroblasts grafts could be realized. Those immature cells come from mesencephalic regions of six to ten weeks-old embryos. Given several technical problems, clinical outcome of the patients is not favourable and moreover, it appears that the cell source is very limited. That's the reason why the use of embryonic or somatic stem cells could be promising. Stem cells are able to self-renew, and could differentiate into several cell types. In this lecture, the author reviews the biological properties of different stem cells types in order to be used in cerebral graft in several neurological diseases. Given their recently unravelled phenotypic plasticity, somatic stem cells could be the best candidate for such a clinical use for autografts.

[What are the realistic hopes for remyelinization in the central nervous system?]. / Quels sont les espoirs actuels de remyélinisation dans le système nerveux central?

Up to now, there is no therapy in order to stimulate a remyelination in the adult central nervous system. So, the study the ontogenesis of oligodendrocytes at the cellular and molecular level could provide cues in order to design such a treatment that will be efficient to remyelinate patients after a multiple sclerosis relapse. In our work, we demonstrated that both neurotransmitters acting trough ionotropic receptors, expressed by oligodendrocytes precursors and some members of the neuregulin growth factors family, could modulate the proliferation and the differentiation of oligodendrocytes progenitors. Furthermore, we demonstrated that the graft of neural stem cells in experimental demyelinated lesion in adult animals is responsible for an efficient remyelination.

The SH2 domain-containing 5-phosphatase SHIP2 is expressed in the germinal layers of embryo and adult mouse brain: increased expression in N-CAM-deficient mice.

The germinative ventricular zone of embryonic brain contains neural lineage progenitor cells that give rise to neurons, astrocytes and oligodendrocytes. The ability to generate neurons persists at adulthood in restricted brain areas. During development, many growth factors exert their effects by interacting with tyrosine kinase receptors and activate the phosphatidylinositol 3-kinase and the Ras/MAP kinase pathways. By its ability to modulate these pathways, the recently identified Src homology 2 domain-containing inositol polyphosphate 5-phosphatase 2, SHIP2, has the potential to regulate neuronal development. Using in situ hybridization technique with multiple synthetic oligonucleotides, we demonstrated that SHIP2 mRNA was highly expressed in the ventricular zone at early embryonic stages and subventricular zones at latter stages of brain and spinal cord and in the sympathetic chain. No significant expression was seen in differentiated fields. This restricted expression was maintained from embryonic day 11.5 to birth. In the periphery, large expression was detected in muscle and kidney and moderate expression in thyroid, pituitary gland, digestive system and bone. In the adult brain, SHIP2 was mainly restricted in structures containing neural stem cells such as the anterior subventricular zone, the rostral migratory stream and the olfactory tubercle. SHIP2 was also detected in the choroid plexuses and the granular layer of the cerebellum. The specificity of SHIP2 expression in neural stem cells was further demonstrated by (i) the dramatic increase in SHIP2 mRNA signal in neural cell adhesion molecule (N-CAM)-deficient mice, which present an accumulation of progenitor cells in the anterior subventricular zone and the rostral migratory stream, (ii) the abundant expression of 160-kDa SHIP2 by western blotting in proliferating neurospheres in culture and its downregulation in non-proliferating differentiated neurospheres. In conclusion, the close correlation between the pattern of SHIP2 expression in the brain and the proliferative and early differentiative events suggests that the phosphatase SHIP2 may have important roles in neural development.

Neurotransmitters as early signals for central nervous system development.

During brain ontogenesis, the temporal and spatial generation of the different types of neuronal and glial cells from precursors occurs as a sequence of successive progenitor stages whose proliferation, survival and cell-fate choice are controlled by environmental and cellular regulatory molecules. Neurotransmitters belong to the chemical microenvironment of neural cells, even at the earliest stages of brain development. It is now established that specific neurotransmitter receptors are present on progenitor cells of the developing central nervous system and could play, during neural development, a role that has remained unsuspected until recently. The present review focuses on the occurrence of neurotransmitters and their corresponding ligand-gated ion channel receptors in immature cells, including neural stem cells of specific embryonic and neonatal brain regions. We summarize in vitro and in vivo data arguing that neurotransmitters could regulate morphogenetic events such as proliferation, growth, migration, differentiation and survival of neural precursor cells. The understanding of neurotransmitter function during early neural maturation could lead to the development of pharmacological tools aimed at improving adult brain repair strategies.

Neuregulin signaling regulates neural precursor growth and the generation of oligodendrocytes in vitro.

Neuregulin 1 (Nrg-1) isoforms have been shown to influence the emergence and growth of oligodendrocytes, the CNS myelin-forming cells. We have investigated how Nrg-1 signaling of ErbB receptors specifically controls the early stages of oligodendrocyte generation from multipotential neural precursors (NPs). We show here that embryonic striatal NPs express multiple Nrg-1 transcripts and proteins as well as their specific receptors, ErbB2 and ErbB4, but not ErbB3. The major isoform synthesized by striatal NPs is a transmembrane type III isoform called cysteine-rich domain Nrg-1. To examine the biological effect of Nrg-1, we added soluble ErbB3 (sErbB3) to growing neurospheres. This inhibitor of Nrg-1 bioactivity decreased mitosis of NPs and increased their apoptosis, resulting in a significant reduction in neurosphere size and number. When NPs were induced to migrate and differentiate by adhesion of neurospheres to the substratum, the level of type III isoforms detected by RT-PCR and Western blot decreased in parallel with a reduction in Nrg-1 fluorescence intensity in differentiating astrocytes, neurons, and oligodendrocytes. Pretreatment of growing neurospheres with sErbB3 induced a threefold increase in the proportion of oligodendrocytes generated from NPs migrating out of the neurosphere. This effect was not observed with an unrelated soluble receptor. Addition of sErbB3 during NP growth and differentiation enhanced oligodendrocyte maturation as shown by expression of galactocerebroside and myelin basic protein. We propose that both type III Nrg-1 signaling and soluble ErbB receptors modulate oligodendrocyte development from NPs.

A 295-kDA intermediate filament-associated protein in radial glia and developing muscle cells in vivo and in vitro.

The RC2 antibody is frequently used to label mouse radial glial cells in all parts of the nervous system where neuronal migration occurs during embryonic and early postnatal life. The antigen recognized by this antibody still needs to be identified. We have characterized further its localization in vivo, its expression and subcellular localization in vitro, as well as its molecular nature. Histologic investigations of whole mouse embryos reveal an equally intense expression of RC2 immunostaining in radial glial cells in brain and spinal cord and in skeletal muscle. In glial cells cultures, the RC2 antibody recognizes an epitope located on the glial cytoskeleton and identified as an intermediate filament associated protein (IFAP) at the ultrastructural level. RC2 immunostaining in those cells is strongly dependent on the presence of a serum-derived activity. Serum-removal causes a decrease of the staining while adding serum back to the cells induces reexpression of RC2 immunoreactivity. By Western blotting, we find that in intermediate filament (IF) preparations obtained from cultured cerebellar glia, the RC2 antibody recognizes a 295-kDa protein whose expression is also dependent on the presence of serum in culture medium. In developing muscle cells, RC2 immunostaining is observed from the myoblast stage and disappears after complete myotube fusion. Both in vivo and in vitro, staining is first seen as a loose capping around myoblasts nuclei and progressively concentrates into Z-disks in association with the muscle IF protein desmin. The RC2 antibody also recognizes a 295-kDa protein band in muscle tissue protein extracts. Thus, the RC2 antibody recognizes a developmentally regulated cytoskeletal protein that is expressed, like other previously identified IFAPs, by cells of the glial and myogenic lineages and whose expression in vitro seems to be controlled by a signaling mechanism known to modulate astroglial morphology.