In vitro neuronal network activity as a new functional diagnostic system to detect effects of Cerebrospinal fluid from autoimmune encephalitis patients.

The intent of this study was to investigate if cerebrospinal fluid (CSF) from autoimmune encephalitis (AE) patients regulates in vitro neuronal network activity differentially to healthy human control CSF (hCSF). To this end, electrophysiological effects of CSF from AE patients or hCSF were measured by in vitro neuronal network activity (ivNNA) recorded with microelectrode arrays (MEA). CSF from patients with either N-methyl-D-aspartate-receptor-antibody (pCSFNMDAR, n = 7) or Leucine-rich-glioma-inactivated-1-Ab (pCSFLGI1, n = 6) associated AE suppressed global spiking activity of neuronal networks by a factor of 2.17 (p < 0.05) or 2.42 (p < 0.05) compared to hCSF. The former also suppressed synchronous network bursting by a factor of 1.93 (p < 0.05) in comparison to hCSF (n = 13). As a functional diagnostic test, this parameter reached a sensitivity of 86% for NMDAR-Ab- and 100% for LGI1-Ab-associated AE vs. hCSF at a specificity of 85%. To explore if modulation at the NMDAR influences effects of hCSF or pathological CSF, we applied the NMDAR-antagonist 2-Amino-5-phosphono-pentanoic acid (AP5). In CSF from NMDAR-Ab-associated AE patients, spike rate reduction by AP5 was more than 2-fold larger than in hCSF (p < 0.05), and network burst rate reduction more than 18-fold (p < 0.01). Recording ivNNA might help discriminating between functional effects of CSF from AE patients and hCSF, and thus could be used as a functional diagnostic test in AE. The pronounced suppression of ivNNA by CSF from NMDAR-Ab-associated AE patients and simultaneous antagonism at the NMDAR by AP5, particularly in burst activity, compared to hCSF plus AP5, confirms that the former contains additional ivNNA-suppressing factors.

Dementia with Lewy bodies: cerebrospinal fluid suppresses neuronal network activity.

One of the core clinical criteria of Dementia with Lewy bodies (DLB) are fluctuations of cognition. Underlying processes may be rather functional than neurodegenerative, reflected by, for example, factors present in cerebrospinal fluid (CSF). The aim of this study was to identify in-vitro neuronal network activity (ivNNA) changes of CSF from DLB patients compared with patients with Parkinson's disease (PD) and controls. Primary neuronal mouse cultures were grown on microelectrode arrays to record ivNNA when exposed to respective CSF samples. If exposed to CSF of DLB patients, ivNNA showed a reduced spike rate and burst rate compared with CSF of PD patients and controls. Our data are suggestive of the presence of functional factors in the CSF of DLB patients that differentiate network activity from PD patients and controls. Future studies should evaluate whether this pilot observation might be related to fluctuations of cognition in DLB.

Freshly frozen E18 rat cortical cells can generate functional neural networks after standard cryopreservation and thawing procedures.

Primary dissociated brain tissue from rodents is widely used in a variety of different scientific methods to investigate cellular processes in vitro. Often, for this purpose cell cultures need to be generated just on time, requiring extensive animal lab infrastructure. We show here that cryopreservation and thawing of dissociated tissue from rat cerebral cortex at embryonic day 18 is feasible without affecting its ability to form functional neuronal networks in vitro. Vitality of fresh and re-thawed cortical cells was comparable, assessed by CellTiter-Blue-assay, CytoTox-ONE assay, immunocytochemical characterization and in vitro neuronal network activity recordings on microelectrode arrays. These findings suggest that planning and execution of experiments might be considerably facilitated by using cryo-preserved neurons instead of acutely dissociated neural cultures due to fewer logistical issues with regard to animal breeding and pregnancy timed preparations.

Impaired action potential initiation in GABAergic interneurons causes hyperexcitable networks in an epileptic mouse model carrying a human Na(V)1.1 mutation.

Mutations in SCN1A and other ion channel genes can cause different epileptic phenotypes, but the precise mechanisms underlying the development of hyperexcitable networks are largely unknown. Here, we present a multisystem analysis of an SCN1A mouse model carrying the NaV1.1-R1648H mutation, which causes febrile seizures and epilepsy in humans. We found a ubiquitous hypoexcitability of interneurons in thalamus, cortex, and hippocampus, without detectable changes in excitatory neurons. Interestingly, somatic Na(+) channels in interneurons and persistent Na(+) currents were not significantly changed. Instead, the key mechanism of interneuron dysfunction was a deficit of action potential initiation at the axon initial segment that was identified by analyzing action potential firing. This deficit increased with the duration of firing periods, suggesting that increased slow inactivation, as recorded for recombinant mutated channels, could play an important role. The deficit in interneuron firing caused reduced action potential-driven inhibition of excitatory neurons as revealed by less frequent spontaneous but not miniature IPSCs. Multiple approaches indicated increased spontaneous thalamocortical and hippocampal network activity in mutant mice, as follows: (1) more synchronous and higher-frequency firing was recorded in primary neuronal cultures plated on multielectrode arrays; (2) thalamocortical slices examined by field potential recordings revealed spontaneous activities and pathological high-frequency oscillations; and (3) multineuron Ca(2+) imaging in hippocampal slices showed increased spontaneous neuronal activity. Thus, an interneuron-specific generalized defect in action potential initiation causes multisystem disinhibition and network hyperexcitability, which can well explain the occurrence of seizures in the studied mouse model and in patients carrying this mutation.

Encephalopathic Susac's Syndrome associated with livedo racemosa in a young woman before the completion of family planning.

BACKGROUND: Susac's Syndrome (SS) consists of the triad of encephalopathy, branch retinal artery occlusions (BRAO) and hearing loss (HL). Histopathologically, SS is characterised by a microangiopathy, and some observations suggest that an immune-mediated damage of endothelial cells might play a role. These findings also implicate a similarity between SS and other autoimmune diseases, most notably juvenile dermatomyositis (JDM). However, SS and JDM are commonly thought to affect distinct and non-overlapping sets of organs, and it is currently not clear how these specificities arise. Moreover, in the absence of clinical trials, some authors suggest that therapeutic approaches in SS should rely on the model of other autoimmune diseases such as JDM. CASE PRESENTATION: Here, we report a case of SS in a 32-year-old pregnant woman. She initially was admitted to the hospital with subacute severe encephalopathy and multifocal neurologic signs. As cranial magnetic resonance imaging (MRI) revealed multifocal white matter lesions including the corpus callosum, erroneously a diagnosis of multiple sclerosis (MS) was made, and intravenous methylprednisolone (IVMP) therapy was initiated. A few days later, an exanthema appeared on the trunk and extremities, which was diagnosed as livedo racemosa (LR). Several weeks later, the patient was readmitted to the clinic with an obscuration of her left visual hemifield and a bilateral HL. Ophthalmologic examination revealed extensive ischemic damage to both retinae. Now the correct diagnosis of SS was established, based on the above triad of clinical symptoms in conjunction with typical MRI and fundoscopic findings. When SS was diagnosed, the standard therapy with intravenous cyclophosphamide (IVCTX) was not instituted because of a significant risk of permanent infertility. Instead, sustained control of disease activity could be achieved with a therapeutic regime combining prednisolone, intravenous immunoglobulins (IVIG), mycophenylate mofetil (MM), and methotrexate (MTX). CONCLUSIONS: An association with LR has only been described in very few cases of SS before and further underlines the pathogenetic relationship between SS and other autoimmune diseases such as JDM. In young women with SS and the desire for a child the combination of MM and MTX may represent a reasonable alternative to IVCTX.

Episodic itch in a case of spinal glioma.

BACKGROUND: Itch is a frequent complaint reported by patients and is usually ascribed to dermatological or metabolic causes. In neurological disorders, however, it is a very unusual symptom and thus its neurological aetiology is likely to be overlooked. There are only very few reports about permanent itch related to lesions of the central nervous system. To our knowledge we report the first case of episodic itch associated with a central nervous lesion. CASE PRESENTATION: A 74-year-old female suffered from long-standing episodes of itch of the dermatomes C2 to C6 on the right side that was refractory to any treatment. On occurrence it propagated in a proximal to distal fashion. Between the episodes the patient was asymptomatic. MRI of the cervical spine uncovered a spinal glioma that matched the location of the symptoms. Treatment with gabapentin led to a prompt reduction of the symptoms. CONCLUSION: Patients with intractable pruritus and dermatomal presentation ought to undergo neurological examination and spinal cord imaging. Thus, ongoing frustrating and sometimes even harmful treatment trials could be avoided.

In vitro neuronal network activity in NMDA receptor encephalitis.

BACKGROUND: Anti-NMDA-encephalitis is caused by antibodies against the N-methyl-D-aspartate receptor (NMDAR) and characterized by a severe encephalopathy with psychosis, epileptic seizures and autonomic disturbances. It predominantly occurs in young women and is associated in 59% with an ovarian teratoma. RESULTS: We describe effects of cerebrospinal fluid (CSF) from an anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis patient on in vitro neuronal network activity (ivNNA). In vitro NNA of dissociated primary rat cortical populations was recorded by the microelectrode array (MEA) system.The 23-year old patient was severely affected but showed an excellent recovery following multimodal immunomodulatory therapy and removal of an ovarian teratoma. Patient CSF (pCSF) taken during the initial weeks after disease onset suppressed global spike- and burst rates of ivNNA in contrast to pCSF sampled after clinical recovery and decrease of NMDAR antibody titers. The synchrony of pCSF-affected ivNNA remained unaltered during the course of the disease. CONCLUSION: Patient CSF directly suppresses global activity of neuronal networks recorded by the MEA system. In contrast, pCSF did not regulate the synchrony of ivNNA suggesting that NMDAR antibodies selectively regulate distinct parameters of ivNNA while sparing their functional connectivity. Thus, assessing ivNNA could represent a new technique to evaluate functional consequences of autoimmune encephalitis-related CSF changes.

Species-dependent differences of embryonic stem cell-derived neural stem cells after Interferon gamma treatment.

Pluripotent stem cell (pSC)-derived, neural stem cells (NSCs) are actually extensively explored in the field of neuroregeneration and to clarify disease mechanisms or model neurological diseases in vitro. Regarding the latter, proliferation and differentiation of pSC-derived NSCs are investigated under the influence of a variety of different substances among them key players of inflammation. However, results generated on a murine genetic background are not always representative for the human situation which increasingly leads to the application of human cell culture systems derived from human pSCs. We investigated here, if the recently described interferon gamma (IFNγ)-induced dysregulated neural phenotype characterized by simultaneous expression of glial and neuronal markers on murine NSCs (Walter et al., 2011, 2012) can also be found on a human genetic background. For this purpose, we performed experiments with human embryonic stem cell-derived NSCs. We could show that the IFNγ-induced dysregulated neural phenotype cannot be induced in human NSCs. This difference occurs, although typical genes like signal transducers and activators of transcription 1 (Stat 1) or interferon regulatory factor 9 (IRF-9) are similarly regulated by IFNγ in both, murine and human populations. These results illustrate that fundamental differences between murine and human neural populations exist in vitro, independent of anatomical system-related properties.

Interferon gamma and sonic hedgehog signaling are required to dysregulate murine neural stem/precursor cells.

BACKGROUND: The pro-inflammatory cytokine interferon gamma (IFNγ), a key player in various neurological diseases, was recently shown to induce a dysregulated phenotype in neural stem/precursor cells (NSPCs) that is characterized by the simultaneous expression of glial and neuronal markers and irregular electrophysiological properties. Thus far, the mechanisms of this phenomenon have remained unclear. METHODOLOGY/PRINCIPAL FINDINGS: To determine if binding of the signal transducers and activators of transcription (Stat 1) to the sonic hedgehog (SHH) promoter is important for this phenomenon to occur, chromatin immunoprecipitation and pharmacological inhibition studies were performed. We report here that the activation of both the Stat 1 and SHH pathways is necessary to elicit the dysregulated phenotype. CONCLUSIONS/SIGNIFICANCE: Thus, blocking these pathways might preserve functional differentiation of NSPCs under inflammatory conditions leading to more effective regeneration.

Flavin mononucleotide-based fluorescent proteins function in mammalian cells without oxygen requirement.

Usage of the enhanced green fluorescent protein (eGFP) in living mammalian cells is limited to aerobic conditions due to requirement of oxygen during chromophore formation. Since many diseases or disease models are associated with acute or chronic hypoxia, eGFP-labeling of structures of interest in experimental studies might be unreliable leading to biased results. Thus, a chromophore yielding a stable fluorescence under hypoxic conditions is desirable. The fluorescence of flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) does not require molecular oxygen. Recently, the advantages of FbFPs for several bacterial strains and yeasts were described, specifically, their usage as a real time fluorescence marker in bacterial expression studies and their ability of chromophore formation under anaerobic conditions. Our objective was to verify if FbFPs also function in mammalian cells in order to potentially broaden the repertoire of chromophores with ones that can reliably be used in mammalian studies under hypoxic conditions. In the present study, we demonstrate for the first time, that FbFPs can be expressed in different mammalian cells, among them murine neural stem cells during proliferative and differentiated stages. Fluorescence intensities were comparable to eGFP. In contrast to eGFP, the FbFP fluorescence did not decrease when cells were exposed to defined hypoxic conditions neither in proliferating nor in differentiated cells. Thus, FbFPs can be regarded as an alternative to eGFP in studies that target cellular structures which are exposed to hypoxic conditions.

In vitro generation of three-dimensional substrate-adherent embryonic stem cell-derived neural aggregates for application in animal models of neurological disorders.

In vitro-differentiated embryonic stem (ES) cells comprise a useful source for cell replacement therapy, but the efficiency and safety of a translational approach are highly dependent on optimized protocols for directed differentiation of ES cells into the desired cell types in vitro. Furthermore, the transplantation of three-dimensional ES cell-derived structures instead of a single-cell suspension may improve graft survival and function by providing a beneficial microenvironment for implanted cells. To this end, we have developed a new method to efficiently differentiate mouse ES cells into neural aggregates that consist predominantly (>90%) of postmitotic neurons, neural progenitor cells, and radial glia-like cells. When transplanted into the excitotoxically lesioned striatum of adult mice, these substrate-adherent embryonic stem cell-derived neural aggregates (SENAs) showed significant advantages over transplanted single-cell suspensions of ES cell-derived neural cells, including improved survival of GABAergic neurons, increased cell migration, and significantly decreased risk of teratoma formation. Furthermore, SENAs mediated functional improvement after transplantation into animal models of Parkinson's disease and spinal cord injury. This unit describes in detail how SENAs are efficiently derived from mouse ES cells in vitro and how SENAs are isolated for transplantation. Furthermore, methods are presented for successful implantation of SENAs into animal models of Huntington's disease, Parkinson's disease, and spinal cord injury to study the effects of stem cell-derived neural aggregates in a disease context in vivo.

Ammonium chloride influences in vitro-neuronal network activity.

UNLABELLED: The objective of the present work is to image functional alterations in hepatic encephalopathy (HE) by ammonia-induced changes of in vitro-neuronal network activity and to identify counteracting strategies. Synchronous bursting behavior of rat cortical cells which is the result of synaptic interaction of excitatory and inhibitory neurons was recorded in vitro on microelectrode arrays (MEAs) after ammonium chloride exposure. In order to test the involvement of astrocytic glutamine metabolism and N-methyl-d-aspartic acid- (NMDA-) receptor function in the observed ammonia-induced network dysregulation and to identify potentially protective strategies, we investigated effects of the glutamine synthetase (GS) inhibitor methionine-sulfoximine (MSO) and the NMDA-receptor antagonist DL-2-Amino-5-phosphono-pentanoic acid (AP-5), respectively. We observed a characteristic ammonia-induced increase of global network activity while network synchrony was suppressed. The increase of global activity, but not the suppression of network synchrony was prevented by inhibiting GS. However, blocking NMDA-receptors prevented both, network excitation and desynchronization. CONCLUSIONS: 1. The observed desynchronization of in vitro-neuronal network activity after ammonium chloride treatment might reflect global neuronal network changes in HE in vivo and suggests the MEA technology as a valuable tool for measuring changes of neuronal connectivity in vitro. 2. Astrocytic glutamine metabolism might be involved in increased global network activity, but not in the suppression of network synchrony. 3. Overactivation of NMDA-receptors might underlie both, the ammonia-induced increase of activity and suppression of network synchrony, suggesting that NMDA-receptor function is involved in HE and that their blockage might be protective. 4. Measuring neuronal network activity in vitro by the MEA technology might help to describe functionally protective measures in HE.

Volume transmission-mediated encephalopathies: a possible new concept?

There is strong evidence that the composition of cerebrospinal fluid (CSF) influences brain development, neurogenesis, and behavior. The bidirectional exchange of CSF and interstitial fluid (ISF) across the ependymal and pia-glial membranes is required for these phenomena to occur. Because ISF surrounds the parenchymal compartment, neuroactive substances in the CSF and ISF can influence neuronal activity. Functionally important neuroactive substances are distributed to distant sites of the central nervous system by the convection and diffusion of CSF and ISF, a process known as volume transmission. It has recently been shown that pathologically altered CSF from patients with acute traumatic brain injury suppresses in vitro neuronal network activity (ivNNA) recorded by multielectrode arrays measuring synchronously bursting neural populations. Functionally relevant substances in pathologically altered CSF have been biochemically identified, and ivNNA has been partially recovered by pharmacologic intervention. It remains unclear whether the in vivo parenchymal compartment remains unaffected by pathologically altered CSF that significantly impairs ivNNA. We hypothesize that pathologic CSF alterations are not just passive indicators of brain diseases but that they actively and directly evoke functional disturbances in global brain activity through the distribution of neuroactive substances, for instance, secondary to focal neurologic disease. For this mechanism, we propose the new term volume transmission-mediated encephalopathies (VTE). Recording ivNNA in the presence of pure human CSF could help to identify and monitor functionally relevant CSF alterations that directly result in VTEs, and the collected data might point to therapeutic ways to antagonize these alterations.

Late-stage neurosyphilis presenting with severe neuropsychiatric deficits: diagnosis, therapy, and course of three patients.

Neurosyphilis is an infectious disease that has reappeared over the past two decades. It is caused by Treponema pallidum subspecies pallidum that can affect the central nervous system (CNS) during any stage of the disease. Besides early CNS involvement predominantly presenting with symptoms of meningitis, a parenchymal affection of the brain leading to severe neuropsychiatric symptoms particularly emerges at later stages, but is rarely seen nowadays due to early antibiotic treatment. Together with the clinical findings, a characteristic combination of serological and cerebrospinal fluid (CSF) abnormalities leads to the diagnosis of neurosyphilis and is required to assess its activity. However, particularly at later stages of disease and after antibiotic treatment, serological and CSF abnormalities may become ambiguous and, therefore, difficult to interpret. This can be accompanied by persisting or fluctuating neuropsychological deficits. To this day, no well-controlled clinical data exists concerning the treatment of late-stage neurosyphilis, neither on type, optimal dosage, duration, and long-term efficacy of antibiotic therapy. Therefore, treatment and follow-up of late-stage neurosyphilis are challenging tasks. Here, we present three cases of neurosyphilis with severe neuropsychiatric symptoms in non-immunocompromised patients and a review of the recent literature.

Stress-resistant neural stem cells positively influence regional energy metabolism after spinal cord injury in mice.

The importance of stem cells to ameliorate the devastating consequences of traumatic injuries in the adult mammalian central nervous system calls for improvements in the capacity of these cells to cope, in particular, with the host response to the injury. We have previously shown, however, that in the acutely traumatized spinal cord local energy metabolism led to decreased ATP levels after neural stem cell (NSC) transplantation. As this might counteract NSC-mediated regenerative processes, we investigated if NSC selected for increased oxidative stress resistance are better suited to preserve local energy content. For this purpose, we exposed wild-type (WT) NSC to hydrogen peroxide prior to transplantation. We demonstrate here that transplantation of WT-NSC into a complete spinal cord compression injury model even lowers the ATP content beyond the level detected in spinal cord injury-control animals. Compared to WT-NSC, stress-resistant (SR) NSC did not lead to a further decrease in ATP content. These differences between WT- and SR-NSC were observed 4 h after the lesion with subsequent transplantation. At 24 h after lesioning, these differences were no more as obvious. Thus, in contrast to native NSC, transplantation of NSC selected for oxidative stress resistance can positively influence local energy metabolism in the first hours after spinal cord compression. The functional relevance of this observation has to be tested in further experiments.

Restoring neuronal function after stroke by cell replacement: anatomic and functional considerations.

BACKGROUND AND PURPOSE: A major challenge to effective treatment after stroke is the restoration of neuronal function. In recent years, cell-based therapies for stroke have been explored in experimental animal models, and the results have suggested behavioral improvements. However, the anatomic targets of a cell-based stroke therapy and the relationship of cell grafts to post stroke reorganization are poorly understood, which results in difficulties defining strategies for neuronal substitution. Given that stroke causes a variety of secondary changes at locations beyond the infarct lesion, overcoming these difficulties is even more important. SUMMARY OF REVIEW: We describe which brain structures and cell types are candidates for substitution and how new neuronal functionality could be implemented in a damaged brain by capitalizing on current concepts of post stroke plasticity.

A new role for interferon gamma in neural stem/precursor cell dysregulation.

BACKGROUND: The identification of factors that compromise neurogenesis is aimed at improving stem cell-based approaches in the field of regenerative medicine. Interferon gamma (IFNγ) is a main pro-inflammatory cytokine and up-regulated during several neurological diseases. IFNγ is generally thought to beneficially enhance neurogenesis from fetal or adult neural stem/precursor cells (NSPCs). RESULTS: We now provide direct evidence to the contrary that IFNγ induces a dysfunctional stage in a substantial portion of NSPC-derived progeny in vitro characterized by simultaneous expression of glial fibrillary acid protein (GFAP) and neuronal markers, an abnormal gene expression and a functional phenotype neither typical for neurons nor for mature astrocytes. Dysfunctional development of NSPCs under the influence of IFNγ was finally demonstrated by applying the microelectrode array technology. IFNγ exposure of NSPCs during an initial 7-day proliferation period prevented the subsequent adequate differentiation and formation of functional neuronal networks. CONCLUSIONS: Our results show that immunocytochemical analyses of NSPC-derived progeny are not necessarily indicating the correct cellular phenotype specifically under inflammatory conditions and that simultaneous expression of neuronal and glial markers rather point to cellular dysregulation. We hypothesize that inhibiting the impact of IFNγ on NSPCs during neurological diseases might contribute to effective neurogenesis and regeneration.

Encephalopathy associated with autoimmune thyroid disease in patients with Graves' disease: clinical manifestations, follow-up, and outcomes.

BACKGROUND: The encephalopathy associated with autoimmune thyroid disease (EAATD) is characterized by neurological/psychiatric symptoms, high levels of anti-thyroid antibodies, increased cerebrospinal fluid protein concentration, non-specific electroencephalogram abnormalities, and responsiveness to the corticosteroid treatment in patients with an autoimmune thyroid disease. Almost all EAATD patients are affected by Hashimoto's thyroiditis (HT), although fourteen EAATD patients with Graves' disease (GD) have been also reported. METHODS: We have recorded and analyzed the clinical, biological, radiological, and electrophysiological findings and the data on the therapeutic management of all GD patients with EAATD reported so far as well as the clinical outcomes in those followed-up in the long term. RESULTS: Twelve of the fourteen patients with EAATD and GD were women. The majority of GD patients with EAATD presented with mild hyperthyroidism at EAATD onset or shortly before it. Active anti-thyroid autoimmunity was detected in all cases. Most of the patients dramatically responded to corticosteroids. The long term clinical outcome was benign but EAATD can relapse, especially at the time of corticosteroid dose tapering or withdrawal. GD and HT patients with EAATD present with a similar clinical, biological, radiological, and electrophysiological picture and require an unaffected EAATD management. CONCLUSIONS: GD and HT equally represent the possible background condition for the development of EAATD, which should be considered in the differential diagnosis of all patients with encephalopathy of unknown origin and an autoimmune thyroid disease, regardless of the nature of the underlying autoimmune thyroid disease.

Cerebrospinal fluid of brain trauma patients inhibits in vitro neuronal network function via NMDA receptors.

Neurological diseases frequently induce pathological changes of cerebrospinal fluid (CSF) that might secondarily influence brain activity, as the CSF-brain barrier is partially permeable. However, functional effects of CSF on neuronal network activity have not been specified to date. Here, we report that CSF specimens from patients with reduced Glasgow Coma Scale values caused by severe traumatic brain injury suppress synchronous activity of in vitro-generated neuronal networks in comparison with controls. We present evidence that underlying mechanisms include increased N-methyl-D-aspartate receptor activity mediated by a CSF fraction containing elevated amino acid concentrations. These proof-of-principle data suggest that determining effects of CSF specimens on neuronal network activity might be of diagnostic value.

Niche-dependent development of functional neuronal networks from embryonic stem cell-derived neural populations.

BACKGROUND: The present work was performed to investigate the ability of two different embryonic stem (ES) cell-derived neural precursor populations to generate functional neuronal networks in vitro. The first ES cell-derived neural precursor population was cultivated as free-floating neural aggregates which are known to form a developmental niche comprising different types of neural cells, including neural precursor cells (NPCs), progenitor cells and even further matured cells. This niche provides by itself a variety of different growth factors and extracellular matrix proteins that influence the proliferation and differentiation of neural precursor and progenitor cells. The second population was cultivated adherently in monolayer cultures to control most stringently the extracellular environment. This population comprises highly homogeneous NPCs which are supposed to represent an attractive way to provide well-defined neuronal progeny. However, the ability of these different ES cell-derived immature neural cell populations to generate functional neuronal networks has not been assessed so far. RESULTS: While both precursor populations were shown to differentiate into sufficient quantities of mature NeuN+ neurons that also express GABA or vesicular-glutamate-transporter-2 (vGlut2), only aggregate-derived neuronal populations exhibited a synchronously oscillating network activity 24 weeks after initiating the differentiation as detected by the microelectrode array technology. Neurons derived from homogeneous NPCs within monolayer cultures did merely show uncorrelated spiking activity even when differentiated for up to 12 weeks. We demonstrated that these neurons exhibited sparsely ramified neurites and an embryonic vGlut2 distribution suggesting an inhibited terminal neuronal maturation. In comparison, neurons derived from heterogeneous populations within neural aggregates appeared as fully mature with a dense neurite network and punctuated vGlut2 expression within presynaptic vesicles. Also those NPCs that had migrated away from adherent neural aggregates maintained their ability to generate a synchronously oscillating neuronal network, even if they were separated from adherent aggregates, dissociated and re-plated. CONCLUSION: These findings suggest that the complex environment within niches and aggregates of heterogeneous neural cell populations support the generation of fully mature neurons and functional neuronal networks from ES cell-derived neural cells. In contrast, homogeneous ES cell-derived NPCs within monolayer cultures exhibited an impaired functional neuronal maturation.