Brain Slices Research Articles

Astrocyte aquaporin mediates a tonic water efflux maintaining brain homeostasis

Brain water homeostasis not only provides a physical protection, but also determines the diffusion of chemical molecules key for information processing and metabolic stability. As a major type of glia in brain parenchyma, astrocytes are the dominant cell type expressing aquaporin water channel. How astrocyte aquaporin contributes to brain water homeostasis in basal physiology remains to be understood. We report that astrocyte aquaporin 4 (AQP4) mediates a tonic water efflux in basal conditions. Acute inhibition of astrocyte AQP4 leads to intracellular water accumulation as optically resolved by fluorescence-translated imaging in acute brain slices, and in vivo by fiber photometry in mobile mice. We then show that aquaporin-mediated constant water efflux maintains astrocyte volume and osmotic equilibrium, astrocyte and neuron Ca2+ signaling, and extracellular space remodeling during optogenetically induced cortical spreading depression. Using diffusion-weighted magnetic resonance imaging (DW-MRI), we observed that in vivo inhibition of AQP4 water efflux heterogeneously disturbs brain water homeostasis in a region-dependent manner. Our data suggest that astrocyte aquaporin, though bidirectional in nature, mediates a tonic water outflow to sustain cellular and environmental equilibrium in brain parenchyma.

Potential of ex vivo organotypic slice cultures in neuro-oncology.

Over recent decades, in vitro and in vivo models have significantly advanced brain cancer research; however, each presents distinct challenges for accurately mimicking in situ conditions. In response, organotypic slice cultures have emerged as a promising model recapitulating precisely specific in vivo phenotypes through an ex vivo approach. Ex vivo organotypic brain slice models can integrate biological relevance and patient-specific variability early in drug discovery, thereby aiming for more precise treatment stratification. However, the challenges of obtaining representative fresh brain tissue, ensuring reproducibility, and maintaining essential central nervous system (CNS)-specific conditions reflecting the in situ situation over time have limited the direct application of ex vivo organotypic slice cultures in robust clinical trials. In this review, we explore the benefits and possible limitations of ex vivo organotypic brain slice cultures in neuro-oncological research. Additionally, we share insights from clinical experts in neuro-oncology on how to overcome these current limitations and improve the practical application of organotypic brain slice cultures beyond academic research.

Dysregulation of zebrin-II cell subtypes in the cerebellum is a shared feature across polyglutamine ataxia mouse models and patients

Spinocerebellar ataxia type 7 (SCA7) is a genetic neurodegenerative disorder caused by a CAG-polyglutamine repeat expansion. Purkinje cells (PCs) are central to the pathology of ataxias, but their low abundance in the cerebellum underrepresents their transcriptomes in sequencing assays. To address this issue, we developed a PC enrichment protocol and sequenced individual nuclei from mice and patients with SCA7. Single-nucleus RNA sequencing in SCA7-266Q mice revealed dysregulation of cell identity genes affecting glia and PCs. Specifically, genes marking zebrin-II PC subtypes accounted for the highest proportion of DEGs in symptomatic SCA7-266Q mice. These transcriptomic changes in SCA7-266Q mice were associated with increased numbers of inhibitory synapses as quantified by immunohistochemistry and reduced spiking of PCs in acute brain slices. Dysregulation of zebrin-II cell subtypes was the predominant signal in PCs of SCA7-266Q mice and was associated with the loss of zebrin-II striping in the cerebellum at motor symptom onset. We furthermore demonstrated zebrin-II stripe degradation in additional mouse models of polyglutamine ataxia and observed decreased zebrin-II expression in the cerebella of patients with SCA7. Our results suggest that a breakdown of zebrin subtype regulation is a shared pathological feature of polyglutamine ataxias.

Correlation Between Regulation of Intestinal Flora by Danggui-Shaoyao-San and Improvement of Cognitive Impairment in Mice With Alzheimer's Disease.

The abnormal central glucose metabolism in Alzheimer's disease (AD) is related to the brain-gut axis. This study aims to explore the target of Danggui-Shaoyao-San (DSS) in improving cognitive impairment. This study analyzed the differences in mice intestinal flora by 16S rRNA sequencing. The cognitive protective effects of DSS were observed through the Morris water maze and the new object recognition. The mitigation effects of DSS on Aβ and p-tau, regulatory effects on glucose metabolism targets, and intestinal structure effects were observed through brain and colon slices staining. The differences in neural ultrastructure were compared by transmission electron microscopy. The results showed that DSS affected the composition of intestinal dominant bacteria and bacteria genera and regulated the abundance of intestinal bacteria in AD mice. DSS improved the behavior of AD mice, alleviated the deposition of AD pathological products in the brain and colon, regulated the expression of glycometabolism-related proteins, and improved the colon barrier structure and neural ultrastructure in the brain of mice with AD. Our findings suggest that DSS may affect AD central glucose metabolism and improve cognition by regulating the gut-brain axis.

The discovery of JAL-TA9 which cleaves amyloid-β with proteolytic activity

Amyloid-β (Aβ) 42, one of the causes of Alzheimer's disease (AD), is produced by the cleavage of amyloid precursor protein (APP) by β- or γ-secretases. Since Aβ42 oligomers exhibit strong neurotoxicity, Aβ42 is predicted to be a potentially efficient target for drug therapies. Recently, we screened peptides that activate MMP7 using our peptide library and found that the synthetic peptide JAL-TA9 (YKGSGFRMI), which is derived from the BoxA region of Tob1 protein, showed proteolytic activity. It is generally accepted that an enzyme should be a large molecular protein consisting of more than thousands of amino acids. Thus, this is the first finding that a small synthetic peptide has protease activity, and we termed Catalytide as the general name of peptides with protease activity. In this study, we demonstrate the cleavage activity of JAL-TA9 not only against the authentic soluble form of Aβ42 but also against the solid type of Aβ42 in the central region. In addition, we demonstrated the cleavage activity using brain slices of AD patients. JAL-TA9 decreased the amount of accumulated Aβ42 in the brain of Alzheimer's patients. Taken together, JAL-TA9 is an attractive seed for the development of peptide drugs with a new strategy for Alzheimer's disease.

Simultaneous Optical and Electrophysiological Monitoring of Neuronal Cells in Brain Slices

Simultaneous Optical and Electrophysiological Monitoring of Neuronal Cells in Brain Slices

Patch-Clamp Recordings from the Dendrite of a Dopaminergic Neuron in a Brain Slice

Patch-Clamp Recordings from the Dendrite of a Dopaminergic Neuron in a Brain Slice

Establishing a Whole-Cell Voltage-Clamp Configuration for Electrophysiological Recordings in Brain Slices

Establishing a Whole-Cell Voltage-Clamp Configuration for Electrophysiological Recordings in Brain Slices

Establishing a Whole-Cell Voltage-Clamp Configuration for Electrophysiological Recordings in Brain Slices

Establishing a Whole-Cell Voltage-Clamp Configuration for Electrophysiological Recordings in Brain Slices

Simultaneous Optical and Electrophysiological Monitoring of Neuronal Cells in Brain Slices

Simultaneous Optical and Electrophysiological Monitoring of Neuronal Cells in Brain Slices

Patch-Clamp Recordings from the Dendrite of a Dopaminergic Neuron in a Brain Slice

Patch-Clamp Recordings from the Dendrite of a Dopaminergic Neuron in a Brain Slice

Recording Whole-Cell Currents with GABA Puffing in a Mouse Brain Slice

Recording Whole-Cell Currents with GABA Puffing in a Mouse Brain Slice

Optical Recording of Neuronal Activity in Brain Slices Stained with a Voltage-Sensitive Dye

Optical Recording of Neuronal Activity in Brain Slices Stained with a Voltage-Sensitive Dye

Establishing a Whole-Cell Configuration for Two-Photon Calcium Imaging of Brain Slices

Establishing a Whole-Cell Configuration for Two-Photon Calcium Imaging of Brain Slices

Optical Recording of Neuronal Activity in Brain Slices Stained with a Voltage-Sensitive Dye

Optical Recording of Neuronal Activity in Brain Slices Stained with a Voltage-Sensitive Dye

An Electrophysiological Study of Retinogeniculate and Corticogeniculate Synapses in Mouse Brain Slices

An Electrophysiological Study of Retinogeniculate and Corticogeniculate Synapses in Mouse Brain Slices

An Electrophysiological Study of Retinogeniculate and Corticogeniculate Synapses in Mouse Brain Slices

An Electrophysiological Study of Retinogeniculate and Corticogeniculate Synapses in Mouse Brain Slices

Electrophysiological Recordings of Reprogrammed Neurons in a Mouse Brain Slice

Electrophysiological Recordings of Reprogrammed Neurons in a Mouse Brain Slice

Recording Whole-Cell Currents with GABA Puffing in a Mouse Brain Slice

Recording Whole-Cell Currents with GABA Puffing in a Mouse Brain Slice

Establishing a Whole-Cell Configuration for Two-Photon Calcium Imaging of Brain Slices

Establishing a Whole-Cell Configuration for Two-Photon Calcium Imaging of Brain Slices