A chronic stress paradigm comprising exposure to predation, tail suspension and restraint induces a depressive syndrome in C57BL/6J mice that occurs in some, but not all, animals. Here, we sought to extend our behavioural studies to investigate how susceptibility (sucrose preference<65%) or resilience (sucrose preference>65%) to stress-induced anhedonia affects the 5HT system and the expression of inflammation-related genes. All chronically stressed animals, displayed increased level of anxiety, but susceptible mice exhibited an increased propensity to float in the forced swim test and demonstrate hyperactivity under stressful lighting conditions. These changes were not present in resilient or acutely stressed animals. Compared to resilient animals, susceptible mice showed elevated expression of tumour necrosis factor alpha (TNF) and the 5-HT transporter (SERT) in the pre-frontal area. Enhanced expression of 5HT(2A) and COX-1 in the pre-frontal area was observed in all stressed animals. In turn, indoleamine-2,3-dioxygenase (IDO) was significantly unregulated in the raphe of susceptible animals. At the cellular level, increased numbers of Iba-1-positive microglial cells were also present in the prefrontal area of susceptible animals compared to resilient animals. Consequently, the susceptible animals display a unique molecular profile when compared to resilient, but anxious, animals. Unexpectedly, this altered profile provides a rationale for exploring anti-inflammatory, and possibly, TNF-targeted therapy for major depression.
Human neural progenitors derived from pluripotent stem cells develop into electrophysiologically active neurons at heterogeneous rates, which can confound disease-relevant discoveries in neurology and psychiatry. By combining patch clamping, morphological and transcriptome analysis on single human neurons in vitro, we defined a continuum of poor to highly functional electrophysiological states of differentiated neurons. The strong correlations between action potentials, synaptic activity, dendritic complexity and gene expression highlight the importance of methods for isolating functionally comparable neurons for in vitro investigations of brain disorders. While whole-cell electrophysiology is the gold standard for functional evaluation, it often lacks the scalability required for disease modeling studies. Here, we demonstrate a multimodal machine-learning strategy to identify new molecular features that predict the physiological states of single neurons, independently of the time spent in vitro. As further proof of concept, we selected one of the potential neurophysiological biomarkers identified in this study – GDAP1L1 – to isolate highly functional live human neurons in vitro.
Hypoxic-ischemic encephalopathy (HIE) in preterm infants is a severe disease for which no curative treatment is available. Cerebral inflammation and invasion of activated peripheral immune cells have been shown to play a pivotal role in the etiology of white matter injury, which is the clinical hallmark of HIE in preterm infants. The objective of this study was to assess the neuroprotective and anti-inflammatory effects of intravenously delivered mesenchymal stem cells (MSC) in an ovine model of HIE. In this translational animal model, global hypoxia-ischemia (HI) was induced in instrumented preterm sheep by transient umbilical cord occlusion, which closely mimics the clinical insult. Intravenous administration of 2 x 106 MSC/kg reduced microglial proliferation, diminished loss of oligodendrocytes and reduced demyelination, as determined by histology and Diffusion Tensor Imaging (DTI), in the preterm brain after global HI. These anti-inflammatory and neuroprotective effects of MSC were paralleled by reduced electrographic seizure activity in the ischemic preterm brain. Furthermore, we showed that MSC induced persistent peripheral T-cell tolerance in vivo and reduced invasion of T-cells into the preterm brain following global HI. These findings show in a preclinical animal model that intravenously administered MSC reduced cerebral inflammation, protected against white matter injury and established functional improvement in the preterm brain following global HI. Moreover, we provide evidence that induction of T-cell tolerance by MSC might play an important role in the neuroprotective effects of MSC in HIE. This is the first study to describe a marked neuroprotective effect of MSC in a translational animal model of HIE.
The prevalence of depression increases with aging. We hypothesized that like humans, old animals exhibit anhedonic-like behavior, along with signs of behavioral despair. In rodents, anhedonia, a reduced sensitivity to reward, which is listed as a core feature of major depression in the DSM-IVR, can be measured by a decrease in intake of and preference for sweet solutions. Here, sucrose intake, forced swimming, immobility in the modified tail suspension test, novelty exploration, grooming, anxiety and locomotor activity were compared in naïve 3-and 18-month-old male C57BL/6 mice. The absolute amounts and the ratio of consumed 1% sucrose solution to water intake was significantly smaller in 18-month-old mice than in 3-month-old mice. The consumption of 5%-sucrose solution requiring high levels of drinking effort, novelty exploration in two setups and grooming behavior in the splash test were reduced in older animals. Analysis of other behaviors suggested that the above-mentioned signs of anhedonic-like traits were unlikely to be attributable to the potential effect of aging on metabolic needs for water, taste perception, motor capabilities or the induction of essential anxiety and neophobia. A 4-week treatment with the antidepressant imipramine (7 mg/kg/day) or dimebon, a compound with suggested neuroprotective proneurogenic properties (1 mg/kg/day) restored sucrose intake and preference in 18-month-old mice. Meanwhile, young and old mice showed no differences in the parameters of behavioral despair evaluated in the forced swim and modified tail suspension tests. Thus, the behavioral profile of aged mice parallels that of humans with elderly depression, in whom the symptoms of hedonic deficits typically outweigh affective disturbances. The assessment of anhedonic-like traits with the sucrose preference test in 18-month-old mice will be useful in preclinical studies of elderly depression.
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