Present state and future perspectives of using pluripotent stem cells in toxicology research

The use of novel drugs and chemicals requires reliable data on their potential toxic effects on humans. Current test systems are mainly based on animals or in vitro–cultured animal-derived cells and do not or not sufficiently mirror the situation in humans. Therefore, in vitro models based on human pluripotent stem cells (hPSCs) have become an attractive alternative. The article summarizes the characteristics of pluripotent stem cells, including embryonic carcinoma and embryonic germ cells, and discusses the potential of pluripotent stem cells for safety pharmacology and toxicology. Special attention is directed to the potential application of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) for the assessment of developmental toxicology as well as cardio- and hepatotoxicology. With respect to embryotoxicology, recent achievements of the embryonic stem cell test (EST) are described and current limitations as well as prospects of embryotoxicity studies using pluripotent stem cells are discussed. Furthermore, recent efforts to establish hPSC-based cell models for testing cardio- and hepatotoxicity are presented. In this context, methods for differentiation and selection of cardiac and hepatic cells from hPSCs are summarized, requirements and implications with respect to the use of these cells in safety pharmacology and toxicology are presented, and future challenges and perspectives of using hPSCs are discussed

Volumetric associations between uncinate fasciculus, amygdala, and trait anxiety

BACKGROUND: Recent investigations of white matter (WM) connectivity suggest an important role of the uncinate fasciculus (UF), connecting anterior temporal areas including the amygdala with prefrontal-/orbitofrontal cortices, for anxiety-related processes. Volume of the UF, however, has rarely been investigated, but may be an important measure of structural connectivity underlying limbic neuronal circuits associated with anxiety. Since UF volumetric measures are newly applied measures, it is necessary to cross-validate them using further neural and behavioral indicators of anxiety. RESULTS: In a group of 32 subjects not reporting any history of psychiatric disorders, we identified a negative correlation between left UF volume and trait anxiety, a finding that is in line with previous results. On the other hand, volume of the left amygdala, which is strongly connected with the UF, was positively correlated with trait anxiety. In addition, volumes of the left UF and left amygdala were inversely associated. CONCLUSIONS: The present study emphasizes the role of the left UF as candidate WM fiber bundle associated with anxiety-related processes and suggests that fiber bundle volume is a WM measure of particular interest. Moreover, these results substantiate the structural relatedness of UF and amygdala by a non-invasive imaging method. The UF-amygdala complex may be pivotal for the control of trait anxiety

Catechol-O-methyltransferase gene variation: Impact on amygdala response to aversive stimuli

The functional catechol-O-methyltransferase (COMT) val158met polymorphism has been found to be associated with anxiety disorders and depression as well as with neural correlates of emotional processing, with, however, contradictory results. Thus, the aim of the present study was to re-evaluate the impact of the COMT val158met variant on neural activation correlates of emotional face processing in a sample of healthy probands. In 85 healthy subjects genotyped for the COMT val158met polymorphism, amygdala responses were assessed by means of fMRI. Participants were presented with anger- and fear-relevant faces in a robust emotion-processing paradigm. For exploratory reasons, a supplementary whole-brain analysis of the allele-dose model and a gender-stratified analysis were conducted. The COMT 158val allele showed an allele-dose effect on increased predominantly left-sided amygdala activity in response to fearful/angry facial stimuli (p(uncorrected)=.00004). This effect was independent from the distribution of the frequently studied 5-HTTLPR polymorphism for which a linear effect of S-alleles on amygdala responsiveness was replicated. The influence of COMT 158val alleles was only discerned in the female subgroup of probands. The whole-brain analysis suggested associations of the COMT 158val allele with increased activity in areas of the ventral visual stream and the lateral prefrontal cortex. The present results provide further support for a-potentially female-specific-role of the COMT val158met polymorphism in the genetic and neural underpinnings of anxiety- and depression-related intermediate phenotypes and may aid in further clarifying the differential role of COMT genotype driven dopaminergic tonus in the processing of emotionally salient stimuli.Katharina Domschke, Bernhard T. Baune, Linda Havlik, Anja Stuhrmann, Thomas Suslow, Harald Kugel, Peter Zwanzger, Dominik Gro, Christina Sehlmeyer, Volker Arolt, Udo Dannlowsk

Neural correlates of trait anxiety in fear extinction

BackgroundFear conditioning involves the amygdala as the main neural structure for learning fear responses whereas fear extinction mainly activates the inhibitory prefrontal cortex (PFC). In this study we investigated whether individual differences in trait anxiety affect amygdala and dorsal anterior cingulate cortex (dACC) activation during fear conditioning and extinction.MethodThirty-two healthy subjects were investigated by functional magnetic resonance imaging (fMRI) at 3 T while performing a cued fear-conditioning task. All participants completed the trait version of the State-Trait Anxiety Inventory (STAI-T). Activations of the amygdala and the dACC were examined with respect to the effects of trait anxiety.ResultsAnalysis of the fMRI data demonstrated enhanced activation in fear-related brain areas, such as the insula and the ACC, during both fear conditioning and extinction. Activation of the amygdala appeared only during the late acquisition phase whereas deactivation was observed during extinction. Regression analyses revealed that highly trait-anxious subjects exhibited sustained amygdala activation and reduced dACC involvement during the extinction of conditioned responses.ConclusionsThis study reveals that high levels of trait anxiety are associated with both increased amygdala activation and reduced dACC recruitment during the extinction of conditioned fear. This hyper-responsitivity of the amygdala and the deficient cognitive control during the extinction of conditioned fear in anxious subjects reflect an increased resistance to extinct fear responses and may thereby enhance the vulnerability to developing anxiety disorders.</jats:sec

Tumor necrosis factor gene variation predicts hippocampus volume in healthy individuals

BackgroundCytokines such as tumor necrosis factor (TNF) α have been implicated in neurodegeneration relevant to various neuropsychiatric disorders. Little is known about the genetic predisposition to neurodegenerative properties of cytokine genes on brain function and on hippocampus (HC) function in particular. In this study we investigate the neurodegenerative role of TNF polymorphisms on brain morphology in healthy individuals.MethodsVoxel-based morphometry was used in a large sample of healthy individuals (n = 303) to analyze the associations between genetic variants of TNF (rs1800629; rs361525) and brain morphology (gray matter concentration).ResultsIn a region of interest analysis of the HC, for rs1800629, we observed a strong genotype effect on bilateral HC gray matter concentration. Carriers of one or two A-alleles had significantly smaller volumes compared with GG-homozygotes. For rs361525, a similar effect was observed at almost the same location, with the A-allele resulting in smaller HC volumes compared with GG homozygotes.ConclusionsThe findings suggest a neurodegenerative role of the A-alleles of the TNF single nucleotide polymorphisms rs1800629 (-308G/A) and rs361525 (-238G/A) on hippocampal volumes in healthy individuals. Future imaging studies on the role of these single nucleotide polymorphisms in psychiatric populations of diseases with neurodegenerative components are warranted.Bernhard T. Baune, Carsten Konrad, Dominik Grotegerd, Thomas Suslow, Patricia Ohrmann, Jochen Bauer, Volker Arolt, Walter Heindel, Katharina Domschke, Sonja Schöning, Astrid Veronika Rauch, Christina Sehlmeyer, Harald Kugel and Udo Dannlowsk