Schizophrenia (SCZ) is a psychiatric disorder that can include symptoms of disorganized speech and thoughts with uncertain underlying mechanisms possibly linked to over‐activated microglia. In this study, we used brain samples from sixteen donors with SCZ and thirteen control donors to assess the differential activation of microglia by quantifying density and 3D reconstruction of microglia stained with ionized calcium‐binding adaptor molecule‐1 (Iba1). Our samples consisted of sections from the frontal, temporal, and cingulate cortical gray matter, subcortical white matter regions (SCWM), and included the anterior corpus callosum. In the first series of studies, we performed a density analysis followed by a spatial analysis to ascertain the microglial density, distribution, and soma size in SCZ brains. Second, we performed a series of morphological quantification techniques to investigate the arborization patterns of the microglia in SCZ. The results demonstrated an increase in microglia density in the cortical gray matter regions in SCZ cases, while in the SCWM, there was a significant increase in microglia density in the frontal and temporal, but not in the other brain regions of interest (ROIs). Spatial analysis using the “nearest neighbor” demonstrated that there was no effect in “clustering”, but there were shorter distances between microglia seen in the SCZ cases. The morphological measures showed that there was a region‐dependent increase in the microglia soma size in the SCZ cases while the Sholl analysis revealed a significant decrease in the microglia arborization in the SCZ cases across all the ROI’s studied. An in‐depth 3D reconstruction of microglia in Brodmann area 9 cortical region found that there was a significant association between age and reduced microglial arborization in the SCZ cases. This region‐dependent age association can help determine whether longitudinal changes in microglial activation across age are brain region‐dependent, which may point to potential therapeutic targets.

Alzheimer's disease (AD) is a progressive neurodegenerative disease that destroys memory and cognitive function. Inflammasome activation has been suggested to play a critical role in the neuroinflammatory response in AD progression, but the cell‐type expression of inflammasome proteins in the brain has not been fully characterized. In this study, we used samples from the hippocampus formation, the subiculum, and the entorhinal cortex brain from 17 donors with low‐level AD pathology and 17 intermediate AD donors to assess the expression of inflammasome proteins. We performed analysis of hippocampal thickness, β‐amyloid plaques, and hyperphosphorylated tau to ascertain the cellular pathological changes that occur between low and intermediate AD pathology. Next, we determined changes in the cells that express the inflammasome sensor proteins NOD‐like receptor proteins (NLRP) 1 and 3, and caspase‐1. In addition, we stained section with IC100, a humanized monoclonal antibody directed against the inflammasome adaptor protein apoptosis‐associated speck‐like protein containing a caspase recruitment domain (ASC), and a commercially available anti‐ASC antibody. Our results indicate that hippocampal cortical thickness did not significantly change between low and intermediate AD pathology, but there was an increase in pTau and β‐amyloid clusters in intermediate AD cases. NLRP3 was identified mainly in microglial populations, whereas NLRP1 was seen in neuronal cytoplasmic regions. There was a significant increase of ASC in neurons labeled by IC100, whereas microglia in the hippocampus and subiculum were labeled with the commercial anti‐ASC antibody. Caspase‐1 was present in the parenchyma in the CA regions where amyloid and pTau were identified. Together, our results indicate increased inflammasome protein expression in the early pathological stages of AD, that IC100 identifies neurons in early stages of AD and that ASC expression correlates with Aβ and pTau in postmortem AD brains.

Down syndrome (DS) occurs with triplication of human chromosome 21 and is associated with deviations in cortical development evidenced by simplified gyral appearance and reduced cortical surface area. Radial glia are neuronal and glial progenitors that also create a scaffolding structure essential for migrating neurons to reach cortical targets and therefore play a critical role in cortical development. The aim of this study was to characterise radial glial expression pattern and morphology in the frontal lobe of the developing human fetal brain with DS and age-matched controls. Secondly, we investigated whether microstructural information from in vivo magnetic resonance imaging (MRI) could reflect histological findings from human brain tissue samples. Immunohistochemistry was performed on paraffin-embedded human post-mortem brain tissue from nine fetuses and neonates with DS (15–39 gestational weeks (GW)) and nine euploid age-matched brains (18–39 GW). Radial glia markers CRYAB, HOPX, SOX2, GFAP and Vimentin were assessed in the Ventricular Zone, Subventricular Zone and Intermediate Zone. In vivo diffusion MRI was used to assess microstructure in these regions in one DS (21 GW) and one control (22 GW) fetal brain. We found a significant reduction in radial glial progenitor SOX2 and subtle deviations in radial glia expression (GFAP and Vimentin) prior to 24 GW in DS. In vivo, fetal MRI demonstrates underlying radial projections consistent with immunohistopathology. Radial glial alterations may contribute to the subsequent simplified gyral patterns and decreased cortical volumes observed in the DS brain. Recent advances in fetal MRI acquisition and analysis could provide non-invasive imaging-based biomarkers of early developmental deviations.

Schizophrenia (SCZ) is a complex psychiatric disorder that involves an inflammatory response thought to be characterized by microglial activation. The inflammasome complex may play critical roles in the pathomechanism of neuroinflammation but how this relates to SCZ remains unclear. In this study, we performed an immunohistochemical (IHC) analysis to compare the expression of inflammasome proteins in brain tissue from donors with SCZ (n = 16) and non-psychiatric donors (NP; n = 13) isolated from the superior frontal cortex (SFC), superior temporal cortex, and anterior cingulate cortex brain regions. To assess changes in the cell populations that express key inflammasome proteins, we performed IHC analyses of apoptosis-associated speck-like protein containing a CARD (ASC), nod-like receptor protein 3 (NLRP3), and interleukin (IL)-18 to determine if these proteins are expressed in microglia, astrocytes, oligodendrocytes, or neurons. Inflammasome proteins were expressed mainly in microglia from SCZ and NP brains. Increased numbers of microglia were present in the SFC of SCZ brains and exhibited higher inflammasome protein expression of ASC, NLRP3, and IL-18 compared to NPs. These findings suggest that increased inflammasome signaling may contribute to the pathology underlying SCZ.

Neuronal heterotopia are ectopic nodules of nerve cells that failed to migrate appropriately during the early development of the fetal brain. Subcortical and periventricular neuronal heterotopia have been described previously in association with agenesis of the corpus callosum (ACC). Most common neuronal migration disorders are related to rare genetic mutations, but in ACC, the genetic basis is unknown in up to 55-70% of cases or is heterogeneous in nature[1]. In this case report, we investigated a neonatal brain with ACC, and neuronal heterotopia (ACC-H) diagnosed on antenatal MR imaging and consistent with band heterotopia on postmortem brain images. Histologically clusters of neurons were seen in both the subcortical and periventricular white matter (PVWM) brain region that coincided with impaired abnormalities in radial glial formation. Immunohistochemistry was performed on paraffin-embedded brain tissue blocks from this case ACC-H and an age-matched control. Using tissue sections from the frontal lobe, we examined the distribution of neuronal cells (HuC/HuD, calretinin, and parvalbumin) growth cone (drebrin) and synaptic proteins (synaptophysin and SNAP-25). Additionally, we investigated how the glia (astroglia; nestin, GFAP, vimentin); oligodendroglia (Olig2) and microglia (Iba-1) differed in ACC-H compared to an age-matched control in the corpus callosum, cortex, lateral ganglionic eminence, and PVWM. As expected in the ACC-H case, we found a lack of callosal radial glia and glutamatergic fibers. We also found a decrease in neurons in the cortical region, disturbances in radial glia and a lack of extracellular matrix components in the ACC-H case. The lateral ganglionic eminence and the PVWM regions in the ACC-H case lacked several cellular components that were identified in the control. Inside the neuronal heterotopia, we found evidence of glutamatergic and GABAergic neurons with apparent synaptic connections. The data presented from this case study provides insight as to the composition of neuronal heterotopia, and how disturbances of important migratory signals may dramatically affect ongoing brain development.

Cetaceans are well-regarded as sentinels for toxin exposure. Emerging studies suggest that cetaceans can also develop neuropathological changes associated with neurodegenerative disease. The occurrence of neuropathology makes cetaceans an ideal species for examining the impact of marine toxins on the brain across the lifespan. Here, we describe TAR DNA-binding protein 43 (TDP-43) proteinopathy and Alzheimer’s disease (AD) neuropathological changes in a beached harbor porpoise (Phocoena phocoena) that was exposed to a toxin produced by cyanobacteria called β-N-methylamino-L-alanine (BMAA). We found pathogenic TDP-43 cytoplasmic inclusions in neurons throughout the cerebral cortex, midbrain and brainstem. P62/sequestosome-1, responsible for the autophagy of misfolded proteins, was observed in the amygdala, hippocampus and frontal cortex. Genes implicated in AD and TDP-43 neuropathology such as APP and TARDBP were expressed in the brain. AD neuropathological changes such as amyloid-β plaques, neurofibrillary tangles, granulovacuolar degeneration and Hirano bodies were present in the hippocampus. These findings further support the development of progressive neurodegenerative disease in cetaceans and a potential causative link to cyanobacterial toxins. Climate change, nutrient pollution and industrial waste are increasing the frequency of harmful cyanobacterial blooms. Cyanotoxins like BMAA that are associated with neurodegenerative disease pose an increasing public health risk.