Design-based stereology in neuroscience

Volumetric study on sheep brain using stereology technique

Three-dimensional morphometric data better show the structural and functional characteristics of the brain. The objective of this study was to estimate the volume of the cerebral structures of the sheep using design-based stereology. The brains of five sheep were used, fixed in formalin 10% and embedded in agar 6%. An average of 10-12 slab was obtained from each brain. All slabs were stained using Mulligan's method and photographs were recorded. The volume of the brain and its structures were estimated using the Cavalieri's estimator and the point counting system. The total volume was 70604.8 ± 132.45 mm3. The volume fractions of the grey and white matters were calculated as 42.55 ± 0.21% and 24.23 ± 0.51% of the whole brain, respectively. The fractional volume of the caudate nucleus and claustrum were estimated at 2.39 ± 0.08% and at 1.008 ± 0.057% of total brain volume. The volumes of corpus callosum, internal capsule and external capsule were 1.24 ± 0.053%, 3.63 ± 0.22% and 0.698 ± 0.049% of total cerebral volume, respectively. These data could help improve the veterinary comparative neuroanatomy knowledge and development of experimental studies in the field.

PGC-1α in the hippocampus mediates depressive-like and stress-coping behaviours and regulates excitatory synapses in the dentate gyrus in mice

Decreased hippocampal synaptic plasticity is an important pathological change in stress-related mood disorders, including major depressive disorder. However, the underlying mechanism is unclear. PGC-1α, a transcriptional coactivator, is a key factor in synaptic plasticity. We investigated the relationships between changes in hippocampal PGC-1α expression and depressive-like and stress-coping behaviours, and whether they are related to hippocampal synapses. Adeno-associated virus was used to alter hippocampal PGC-1α expression in male C57BL/6 mice. The sucrose preference test and forced swimming test were used to assess their depressive-like and stress-coping behaviours, respectively. Immunohistochemistry and stereology were used to calculate the total number of excitatory synapses in each hippocampal subregion (the cornu ammonis (CA) 1, CA3, and dentate gyrus). Immunofluorescence was used to visualize the changes in dendritic structure. Western blotting was used to detect the expression of hippocampal PGC-1α and mitochondrial-associated proteins, such as UCP2, NRF1 and mtTFAs. Our results showed that mice with downregulated PGC-1α expression in the hippocampus exhibited depressive-like and passive stress-coping behaviours, while mice with upregulated PGC-1α in the hippocampus exhibited increased stress-coping behaviours. Moreover, the downregulation of hippocampal PGC-1α expression resulted in a decrease in the number of excitatory synapses in the DG and in the protein expression of UCP2 in the hippocampus. Alternatively, upregulation of hippocampal PGC-1α yielded the opposite results. This suggests that hippocampal PGC-1α is involved in regulating depressive-like and stress-coping behaviours and modulating the number of excitatory synapses in the DG. This provides new insight for the development of antidepressants.

The wake- and sleep-modulating neurons of the lateral hypothalamic area demonstrate a differential pattern of degeneration in Alzheimers disease

BACKGROUND

Sleep-wake dysfunction is an early and common event in Alzheimer's disease (AD). The lateral hypothalamic area (LHA) regulates the sleep and wake cycle through wake-promoting orexinergic neurons (OrxN) and sleep-promoting melanin-concentrating hormone or MCHergic neurons (MCHN). These neurons share close anatomical proximity with functional reciprocity. This study investigated LHA OrxN and MCHN loss patterns in AD individuals. Understanding the degeneration pattern of these neurons will be instrumental in designing potential therapeutics to slow down the disease progression and remediate the sleep-wake dysfunction in AD.

METHODS

Postmortem human brain tissue from donors with AD (across progressive stages) and controls were examined using unbiased stereology. Formalin-fixed, celloidin-embedded hypothalamic sections were stained with Orx-A/MCH, p-tau (CP13), and counterstained with gallocyanin. Orx or MCH-positive neurons with or without CP13 inclusions and gallocyanin-stained neurons were considered for stereology counting. Additionally, we extracted RNA from the LHA using conventional techniques. We used customized Neuropathology and Glia nCounter (Nanostring) panels to study gene expression. Wald statistical test was used to compare the groups, and the genes were considered differentially expressed when the p-value was <.05.

RESULTS

We observed a progressive decline in OrxN alongside a relative preservation of MCHN. OrxN decreased by 58% (p=0.03) by Braak stages (BB) 1-2 and further declined to 81% (p=0.03) by BB 5-6. Conversely, MCHN demonstrated a non-statistical significant decline (27%, p=0.1088) by BB 6. We observed a progressive increase in differentially expressed genes (DEGs), starting with glial profile changes in BB2. While OrxN loss was observed, Orx-related genes showed upregulation in BB 3-4 compared to BB 0-1. GO and KEGG terms related to neuroinflammatory pathways were mainly enriched.

CONCLUSIONS

To date, OrxN loss in the LHA represents the first neuronal population to die preceding the loss of LC neurons. Conversely, MCHN shows resilience to AD p-tau accumulation across Braak stages. The initial loss of OrxN correlates with specific neuroinflammation, glial profile changes, and an overexpression of HCRT, possibly due to hyperexcitation following compensation mechanisms. Interventions preventing OrxN loss and inhibiting p-tau accumulation in the LHA could prevent neuronal loss in AD and, perhaps, the progression of the disease.

Instrumental successive negative contrast in rats: Trial distribution, reward magnitude, and prefrontal cortex activation

Successive negative contrast (SNC) has been used to study reward relativity, reward loss, and frustration for decades. In instrumental SNC (iSNC), the anticipatory performance of animals downshifted from a large reward to a small reward is compared to that of animals always reinforced with the small reward. iSNC involves a transient deterioration of anticipatory behavior in downshifted animals compared to unshifted controls. There is scattered information on the optimal parameters to produce this effect and even less information about its neural basis. Five experiments with rats trained in a runway to collect food pellets explored the effects of trial distribution (massed or spaced), amount of preshift training, reward disparity, and reward magnitude on the development of an iSNC effect. Start, run, and goal latencies were measured. Using spaced trials (one trial per day), evidence of the iSNC effect was observed with 24 preshift trials and a 32-to-4 pellet disparity. With massed trials (4 trials per session separated by 30-s intertrial intervals), evidence of iSNC was found with 12 preshift sessions (a total of 48 trials) and a 16-to-2 pellet disparity. The massed-training procedure was then used to assess neural activity in three prefrontal cortex areas using c-Fos expression in animals perfused after the first downshift session. There was evidence of increased activation in the anterior cingulate cortex and a trend toward increased activation in the infralimbic and prelimbic cortices. These procedures open a venue for studying the neural basis of the instrumental behavior of animals that experience reward loss.

VEGF expression disparities in brainstem motor neurons of the SOD1G93A ALS model: Correlations with neuronal vulnerability

Amyotrophic lateral sclerosis (ALS) is a rare neuromuscular disease characterized by severe muscle weakness mainly due to degeneration and death of motor neurons. A peculiarity of the neurodegenerative processes is the variable susceptibility among distinct neuronal populations, exemplified by the contrasting resilience of motor neurons innervating the ocular motor system and the more vulnerable facial and hypoglossal motor neurons. The crucial role of vascular endothelial growth factor (VEGF) as a neuroprotective factor in the nervous system is well-established since a deficit of VEGF has been related to motoneuronal degeneration. In this study, we investigated the survival of ocular, facial, and hypoglossal motor neurons utilizing the murine SOD1G93A ALS model at various stages of the disease. Our primary objective was to determine whether the survival of the different brainstem motor neurons was linked to disparate VEGF expression levels in resilient and susceptible motor neurons throughout neurodegeneration. Our findings revealed a selective loss of motor neurons exclusively within the vulnerable nuclei. Furthermore, a significantly higher level of VEGF was detected in the more resistant motor neurons, the extraocular ones. We also examined whether TDP-43 dynamics in the brainstem motor neuron of SOD mice was altered. Our data suggests that the increased VEGF levels observed in extraocular motor neurons may potentially underlie their resistance during the neurodegenerative processes in ALS in a TDP-43-independent manner. Our work might help to better understand the underlying mechanisms of selective vulnerability of motor neurons in ALS.

Neonatal estrogen induces male-like expression of astroglial markers of maturation and plasticity in the neocortex of female mice

Astroglia play a crucial role in various aspects of neurodevelopment including building, maintaining, and modulating neuronal circuits that underly complex behaviours in the neocortex. Telencephalic regions exhibit sex differences in neuronal networks that arise early in development. Astroglia express receptors for gonadal hormones responsible for the organization of sex differences, such as estrogen, placing them in a key position to modulate sex differences in the development of neuronal networks. Astroglial cells express specific proteins related to their morphology, function, and maturation. We have previously shown that P7-P14 is a key transition period for neocortical astroglial maturation and that males reach a mature phenotype earlier than females, at P7. In this study, we investigated whether administration of perinatal estradiol to female mice is sufficient to masculinize astroglial protein and gene expression related to maturation that we previously observed at P7. We found that canonical astroglial markers like glial fibrillary acidic protein and glutamine synthetase are not affected by perinatal estrogen, but markers of astroglial maturation, Vimentin, Aldh1a1, Dio2, and the number of actively dividing astroglia are masculinized by perinatal estradiol administration. These findings suggest that sex differences in neocortical astroglial maturation are at least in-part due to the role of perinatal estrogen. Given the higher prevalence of neurodevelopmental disorders in males compared to females and the involvement of astroglia in virtually all neurodevelopmental disorders, further research is needed to determine other contributions to sex differences in neocortical astroglial cells.

A rapid workflow for neuron counting in combined light sheet microscopy and magnetic resonance histology

Information on regional variation in cell numbers and densities in the CNS provides critical insight into structure, function, and the progression of CNS diseases. However, variability can be real or a consequence of methods that do not account for technical biases, including morphologic deformations, errors in the application of cell type labels and boundaries of regions, errors of counting rules and sampling sites. We address these issues in a mouse model by introducing a workflow that consists of the following steps: 1. Magnetic resonance histology (MRH) to establish the size, shape, and regional morphology of the mouse brain in situ. 2. Light-sheet microscopy (LSM) to selectively label neurons or other cells in the entire brain without sectioning artifacts. 3. Register LSM volumes to MRH volumes to correct for dissection errors and both global and regional deformations. 4. Implement stereological protocols for automated sampling and counting of cells in 3D LSM volumes. This workflow can analyze the cell densities of one brain region in less than 1 min and is highly replicable in cortical and subcortical gray matter regions and structures throughout the brain. This method demonstrates the advantage of not requiring an extensive amount of training data, achieving a F1 score of approximately 0.9 with just 20 training nuclei. We report deformation-corrected neuron (NeuN) counts and neuronal density in 13 representative regions in 5 C57BL/6J cases and 2 BXD strains. The data represent the variability among specimens for the same brain region and across regions within the specimen. Neuronal densities estimated with our workflow are within the range of values in previous classical stereological studies. We demonstrate the application of our workflow to a mouse model of aging. This workflow improves the accuracy of neuron counting and the assessment of neuronal density on a region-by-region basis, with broad applications for studies of how genetics, environment, and development across the lifespan impact cell numbers in the CNS.

Scaling up cell-counting efforts in neuroscience through semi-automated methods

Quantifying how the cellular composition of brain regions vary across development, aging, sex, and disease, is crucial in experimental neuroscience, and the accuracy of different counting methods is continuously debated. Due to the tedious nature of most counting procedures, studies are often restricted to one or a few brain regions. Recently, there have been considerable methodological advances in combining semi-automated feature extraction with brain atlases for cell quantification. Such methods hold great promise for scaling up cell-counting efforts. However, little focus has been paid to how these methods should be implemented and reported to support reproducibility. Here, we provide an overview of practices for conducting and reporting cell counting in mouse and rat brains, showing that critical details for interpretation are typically lacking. We go on to discuss how novel methods may increase efficiency and reproducibility of cell counting studies. Lastly, we provide practical recommendations for researchers planning cell counting.

Reduced cortical neuron number and neuron density in schizophrenia with focus on area 24: a post-mortem case-control study

Structural and functional abnormalities of the anterior cingulate cortex (ACC) have frequently been identified in schizophrenia. Alterations of von Economo neurons (VENs), a class of specialized projection neurons, have been found in different neuropsychiatric disorders and are also suspected in schizophrenia. To date, however, no definitive conclusions can be drawn about quantitative histologic changes in the ACC in schizophrenia because of a lack of rigorous, design-based stereologic studies. In the present study, the volume, total neuron number and total number of VENs in layer V of area 24 were determined in both hemispheres of postmortem brains from 12 male patients with schizophrenia and 11 age-matched male controls. To distinguish global from local effects, volume and total neuron number were also determined in the whole area 24 and whole cortical gray matter (CGM). Measurements were adjusted for hemisphere, age, postmortem interval and fixation time using an ANCOVA model. Compared to controls, patients with schizophrenia showed alterations, with lower mean total neuron number in CGM (- 14.9%, P = 0.007) and in layer V of area 24 (- 21.1%, P = 0.002), and lower mean total number of VENs (- 28.3%, P = 0.027). These data provide evidence for ACC involvement in the pathophysiology of schizophrenia, and complement neuroimaging findings of impaired ACC connectivity in schizophrenia. Furthermore, these results support the hypothesis that the clinical presentation of schizophrenia, particularly deficits in social cognition, is associated with pathology of VENs.

The influence of age and sex on the absolute cell numbers of the human brain cerebral cortex

The human cerebral cortex is one of the most evolved regions of the brain, responsible for most higher-order neural functions. Since nerve cells (together with synapses) are the processing units underlying cortical physiology and morphology, we studied how the human neocortex is composed regarding the number of cells as a function of sex and age. We used the isotropic fractionator for cell quantification of immunocytochemically labeled nuclei from the cerebral cortex donated by 43 cognitively healthy subjects aged 25-87 years old. In addition to previously reported sexual dimorphism in the medial temporal lobe, we found more neurons in the occipital lobe of men, higher neuronal density in women's frontal lobe, but no sex differences in the number and density of cells in the other lobes and the whole neocortex. On average, the neocortex has ~10.2 billion neurons, 34% in the frontal lobe and the remaining 66% uniformly distributed among the other 3 lobes. Along typical aging, there is a loss of non-neuronal cells in the frontal lobe and the preservation of the number of neurons in the cortex. Our study made possible to determine the different degrees of modulation that sex and age evoke on cortical cellularity.

A mitochondrial-targeted antioxidant (MitoQ) improves motor coordination and reduces Purkinje cell death in a mouse model of ARSACS

Mitochondrial deficits have been observed in animal models of Autosomal-recessive spastic ataxia of the Charlevoix-Saguenay (ARSACS) and in patient-derived fibroblasts. We investigated whether mitochondrial function could be restored in Sacs^-/- mice, a mouse model of ARSACS, using the mitochondrial-targeted antioxidant ubiquinone MitoQ. After 10 weeks of chronic MitoQ administration in drinking water, we partially reversed motor coordination deficits in Sacs^-/- mice but did not affect litter-matched wild-type control mice. MitoQ administration led to a restoration of superoxide dismutase 2 (SOD2) in cerebellar Purkinje cell somata without altering Purkinje cell firing deficits. Purkinje cells in anterior vermis of Sacs^-/- mice normally undergo cell death in ARSACS; however, Purkinje cells numbers were elevated after chronic MitoQ treatment. Furthermore, Purkinje cell innervation of target neurons in the cerebellar nuclei of Sacs^-/- mice were also partially restored with MitoQ treatment. Our data suggest that MitoQ is a potential therapeutic treatment for ARSACS and that it improves motor coordination via increasing cerebellar Purkinje cell mitochondria function and reducing Purkinje cell death.

A rapid workflow for neuron counting in combined light sheet microscopy and magnetic resonance histology

Information on regional variation in cell numbers and densities in the CNS provides critical insight into structure, function, and the progression of CNS diseases. However, variability can be real or can be a consequence of methods that do not account for technical biases, including morphologic deformations, errors in the application of cell type labels and boundaries of regions, errors of counting rules and sampling sites. We address these issues of by introducing a workflow that consists of the following steps: 1. Magnetic resonance histology (MRH) to establish the size, shape, and regional morphology of the mouse brain in situ. 2. Light-sheet microscopy (LSM) to selectively label all neurons or other cells in the entire brain without sectioning artifacts. 3. Register LSM volumes to MRH volumes to correct for dissection errors and morphological deformations. 4. Implement novel protocol for automated sampling and counting of cells in 3D LSM volumes. This workflow can analyze the cells density of one brain region in less than 1 min and is highly replicable to cortical and subcortical gray matter regions and structures throughout the brain. We report deformation-corrected neuron (NeuN) counts and neuronal density in 13 representative regions in 5 C57B6/6J and 2 BXD strains. The data represent the variability among cases for the same brain region and across regions within case. Our data are consistent with previous studies. We demonstrate the application of our workflow to a mouse model of aging. This workflow improves the accuracy of neuron counting and the assessment of neuronal density on a region-by-region basis, with broad applications in how genetics, environment, and development across the lifespan impact brain structure.

Applications of various stereological tools for estimation of biological tissues

To provide concise and brief important stereological application methods and techniques for estimating biological tissues. Stereology studies the quantity of biological tissue using little practice and the low price of counting and preparing tissue slices to obtain direct and accurate results. Since their establishment, the stereological techniques underwent much improvement, thus allowing more precise analysis of target structures using various approaches. Using stereological tools, advances in stereological techniques made the target tissues or organs represented by 2D instead of 3D dimensions. Process tools estimate volume, area and length. According to the exciting tissue and aims, the stereological tools perform differently. This review summarizes various stereological tools and techniques, providing brief information about the orientation method, slicer probe method, Delesse's principle, Cavalieri principle, disector, fractionator, nucleator, virtual cycloids and saucer, which are described in detail.

Host oligodendrogliopathy and α-synuclein strains dictate disease severity in multiple system atrophy

Multiple system atrophy is a progressive neurodegenerative disease with prominent autonomic and motor features. During early stages, different subtypes of the disease are distinguished by their predominant parkinsonian or cerebellar symptoms, reflecting its heterogeneous nature. The pathognomonic feature of multiple system atrophy is the presence of α-synuclein (αSyn) protein deposits in oligodendroglial cells. αSyn can assemble in specific cellular or disease environments and form αSyn strains with unique structural features, but the ability of αSyn strains to propagate in oligodendrocytes remains elusive. Recently, it was shown that αSyn strains with related conformations exist in the brains of patients. Here, we investigated whether different αSyn strains can influence multiple system atrophy progression in a strain-dependent manner. To this aim, we injected two recombinant αSyn strains (fibrils and ribbons) in multiple system atrophy transgenic mice and found that they determined disease severity in multiple system atrophy via host-restricted and cell-specific pathology in vivo. αSyn strains significantly impact disease progression in a strain-dependent way via oligodendroglial, neurotoxic and immune-related mechanisms. Neurodegeneration and brain atrophy were accompanied by unique microglial and astroglial responses and the recruitment of central and peripheral immune cells. The differential activation of microglial cells correlated with the structural features of αSyn strains both in vitro and in vivo. Spectral analysis showed that ribbons propagated oligodendroglial inclusions that were structurally distinct from those of fibrils, with resemblance to oligodendroglial inclusions, in the brains of patients with multiple system atrophy. This study, therefore, shows that the multiple system atrophy phenotype is governed by both the nature of the αSyn strain and the host environment and that by injecting αSyn strains into an animal model of the disease, a more comprehensive phenotype can be established.

Beneficial effects of the phytoestrogen genistein on hippocampal impairments of spontaneously hypertensive rats (SHR)

Hippocampal neuropathology is a recognized feature of the spontaneously hypertensive rat (SHR). The hippocampal alterations associate with cognitive impairment. We have shown that hippocampal abnormalities are reversed by 17β-estradiol, a steroid binding to intracellular receptors (estrogen receptor α and β subtypes) or the membrane-located G-protein coupled estradiol receptor. Genistein (GEN) is a neuroprotective phytoestrogen which binds to estrogen receptor β and G-protein coupled estradiol receptor. Here, we investigated whether GEN neuroprotection extends to SHR. For this purpose, we treated 5-month-old SHR for 2 weeks with 10 mg kg^-1 daily s.c injections of GEN. We analyzed the expression of doublecortin+ neuronal progenitors, glial fibrillary acidic protein+ astrocytes and ionized calcium-binding adapter molecule 1+ microglia in the CA1 region and dentate gyrus of the hippocampus using immunocytochemistry, whereas a quantitative real-time polymerase chain reaction was used to measure the expression of pro- and anti-inflammatory factors tumor necrosis factor α, cyclooxygenase-2 and transforming growth factor β. We also evaluated hippocampal dependent memory using the novel object recognition test. The results showed a decreased number of doublecortin+ neural progenitors in the dentate gyrus of SHR that was reversed with GEN. The number of glial fibrillary acidic protein+ astrocytes in the dentate gyrus and CA1 was increased in SHR but significantly decreased by GEN treatment. Additionally, GEN shifted microglial morphology from the predominantly activated phenotype present in SHR, to the more surveillance phenotype found in normotensive rats. Furthermore, treatment with GEN decreased the mRNA of the pro-inflammatory factors tumor necrosis factor α and cyclooxygenase-2 and increased the mRNA of the anti-inflammatory factor transforming growth factor β. Discrimination index in the novel object recognition test was decreased in SHR and treatment with GEN increased this parameter. Our results indicate important neuroprotective effects of GEN at the neurochemical and behavioral level in SHR. Our data open an interesting possibility for proposing this phytoestrogen as an alternative therapy in hypertensive encephalopathy.

Neuronal density and expression of calcium-binding proteins across the layers of the superior colliculus in the common marmoset (Callithrix jacchus)

The superior colliculus (SC) is a layered midbrain structure with functions that include polysensory and sensorimotor integration. Here, we describe the distribution of different immunohistochemically identified classes of neurons in the SC of adult marmoset monkeys (Callithrix jacchus). Neuronal nuclei (NeuN) staining was used to determine the overall neuronal density in the different SC layers. In addition, we studied the distribution of neurons expressing different calcium-binding proteins (calbindin [CB], parvalbumin [PV] and calretinin [CR]). Our results indicate that neuronal density in the SC decreases from superficial to deep layers. Although the neuronal density within the same layer varies little across the mediolateral axis, it tends to be lower at rostral levels, compared to caudal levels. Cells expressing different calcium-binding proteins display differential gradients of density according to depth. Both CB- and CR-expressing neurons show markedly higher densities in the stratum griseum superficiale (SGS), compared to the stratum opticum and intermediate and deep layers. However, CR-expressing neurons are twice as common as CB-expressing neurons outside the SGS. The distribution of PV-expressing cells follows a shallow density gradient from superficial to deep layers. When normalized relative to total neuronal density, the proportion of CR-expressing neurons increases between the superficial and intermediate layers, whereas that of CB-expressing neurons declines toward the deep layers. The proportion of PV-expressing neurons remains constant across layers. Our data provide layer-specific and accurate estimates of neuronal density, which may be important for the generation of biophysical models of how the primate SC transforms sensory inputs into motor signals.

Decreased Oligodendrocyte Number in Hippocampal Subfield CA4 in Schizophrenia: A Replication Study

Hippocampus-related cognitive deficits in working and verbal memory are frequent in schizophrenia, and hippocampal volume loss, particularly in the cornu ammonis (CA) subregions, was shown by magnetic resonance imaging studies. However, the underlying cellular alterations remain elusive. By using unbiased design-based stereology, we reported a reduction in oligodendrocyte number in CA4 in schizophrenia and of granular neurons in the dentate gyrus (DG). Here, we aimed to replicate these findings in an independent sample. We used a stereological approach to investigate the numbers and densities of neurons, oligodendrocytes, and astrocytes in CA4 and of granular neurons in the DG of left and right hemispheres in 11 brains from men with schizophrenia and 11 brains from age- and sex-matched healthy controls. In schizophrenia, a decreased number and density of oligodendrocytes was detected in the left and right CA4, whereas mean volumes of CA4 and the DG and the numbers and density of neurons, astrocytes, and granular neurons were not different in patients and controls, even after adjustment of variables because of positive correlations with postmortem interval and age. Our results replicate the previously described decrease in oligodendrocytes bilaterally in CA4 in schizophrenia and point to a deficit in oligodendrocyte maturation or a loss of mature oligodendrocytes. These changes result in impaired myelination and neuronal decoupling, both of which are linked to altered functional connectivity and subsequent cognitive dysfunction in schizophrenia.

A Stereological Study of the Three Types of Ganglia of Male, Female, and Undifferentiated Scrobicularia plana (Bivalvia)

Neurotransmitters modulate gonadal maturation in bivalves. However, it remains unclear whether there are differences in the nervous system structure between sexes, maturation, and ganglia. Therefore, a stereological study was conducted on the ganglia of adult peppery furrow shell (Scrobicularia plana). Equal-sized males, females, and undifferentiated (gamete absence) animals were fixed with 10% formalin and processed for light microscopy. They were serially cut into 35 µm paraffin thick sections and stained with hematoxylin-eosin. Sections with cerebral (cerebropleural), pedal, and visceral ganglia were studied. The parameters estimated were the volumes of the ganglia, the total and relative volumes of their cortex (outer layer) and medulla (neuropil), and the total number of cells (neurons, glia, and pigmented) per ganglia and compartment. The volumes and numbers were estimated, respectively, by the Cavalieri principle and by the optical fractionator. Females show a larger glia to neuron numerical ratio. Further, females have a greater ganglionic volume than undifferentiated adults, with males showing intermediate values. These facts indicate that the ganglia size is related somehow to maturation. The cell size forms the basis of the differences because total cellularity is equal among the groups. The three ganglion types differ in total volumes and the volume ratio of the cortex versus the medulla. The greater volumes of the pedal ganglia (vis-a-vis the cerebral ones) and of the visceral ganglia (in relation to all others) imply more voluminous cortexes and medullae, but more neuronal and non-neuronal cells only in the visceral. The new fundamental data can help interpret bivalve neurophysiology.

Focal amyloid and asymmetric tau in an imaging-to-autopsy case of clinical primary progressive aphasia with Alzheimer disease neuropathology

Quantification of in vivo amyloid and tau PET imaging relationships with postmortem measurements are critical for validating the sensitivity and specificity imaging biomarkers across clinical phenotypes with Alzheimer disease neuropathologic change (ADNC). This study examined the quantitative relationship between regional binding of in vivo ¹⁸F-florbetapir amyloid PET and ¹⁸F-flortaucipir tau PET with postmortem stereological counts of amyloid plaques and neurofibrillary tangles (NFT) in a case of primary progressive aphasia (PPA) with ADNC, where neurodegeneration asymmetrically targets the left hemisphere. Beginning 2 years prior to death, a 63-year-old right-handed man presenting with agrammatic variant PPA underwent a florbetapir and flortaucpir PET scan, and neuropsychological assessments and magnetic resonance imaging sessions every 6 months. Florbetapir and flortaucpir PET standard uptake value ratios (SUVRs) were quantified from 8 left and right hemisphere brain regions with stereological quantification of amyloid plaques and NFTs from corresponding postmortem sections. Pearson's correlations and measures of asymmetry were used to examine relationships between imaging and autopsy measurements. The three visits prior to death revealed decline of language measures, with marked progression of atrophy. Florbetapir PET presented with an atypical focal pattern of uptake and showed a significant positive correlation with postmortem amyloid plaque density across the 8 regions (r = 0.92; p = 0.001). Flortaucipir PET had a left-lateralized distribution and showed a significant positive correlation with NFT density (r = 0.78; p = 0.023). Flortaucipir PET and NFT density indicated a medial temporal lobe sparing presentation of ADNC, demonstrating that AD does not always target the medial temporal lobe. This study adds additional evidence, in a non-amnestic phenotype of ADNC, that there is a strong correlation between AD PET biomarkers, florbetapir and flortaucipir, with quantitative neuropathology. The atypical and focal presentation of plaque density and florbetapir PET uptake suggests not all amyloid pathology presents as diffuse across neocortex.

Odor blocking of stress hormone responses

Scents have been employed for millennia to allay stress, but whether or how they might do so is largely unknown. Fear and stress induce increases in blood stress hormones controlled by hypothalamic corticotropin releasing hormone neurons (CRHNs). Here, we report that two common odorants block mouse stress hormone responses to three potent stressors: physical restraint, predator odor, and male-male social confrontation. One odorant inhibits restraint and predator odor activation of excitatory neurons upstream of CRHNs in the bed nucleus of the stria terminalis (BNSTa). In addition, both activate inhibitory neurons upstream of CRHNs in the hypothalamic ventromedial nucleus (VMH) and silencing of VMH inhibitory neurons hinders odor blocking of stress. Together, these findings indicate that odor blocking can occur via two mechanisms: (1) Inhibition of excitatory neurons that transmit stress signals to CRHNs and (2) activation of inhibitory neurons that act directly or indirectly to inhibit stressor activation of CRHNs.

Behaviour-driven Arc expression is greater in dorsal than ventral CA1 regardless of task or sex differences

Evidence from genetic, behavioural, anatomical, and physiological study suggests that the hippocampus functionally differs across its longitudinal (dorsoventral or septotemporal) axis. Although, how to best characterize functional and representational differences in the hippocampus across its long axis remains unclear. While some suggest that the hippocampus can be divided into dorsal and ventral subregions that support distinct cognitive functions, others posit that these regions vary in their granularity of representation, wherein spatial-temporal resolution decreases in the ventral (temporal) direction. Importantly, the cognitive and granular hypotheses also make distinct predictions on cellular recruitment dynamics under conditions when animals perform tasks with qualitatively different cognitive-behavioural demands. One interpretation of the cognitive function account implies that dorsal and ventral cellular recruitment differs depending on relevant behavioural demands, while the granularity account suggests similar recruitment dynamics regardless of the nature of the task performed. Here, we quantified cellular recruitment with the immediate early gene (IEG) Arc across the entire longitudinal CA1 axis in female and male rats performing spatial- and fear-guided memory tasks. Our results show that recruitment is greater in dorsal than ventral CA1 regardless of task or sex, and thus support a granular view of hippocampal function across the long axis. We further discuss how future experiments might determine the relative contributions of cognitive function and granularity of representation to neuronal activity dynamics in hippocampal circuits.

Sex differences in developmental patterns of neocortical astroglia: A mouse translatome database

Astroglial cells are key players in the development and maintenance of neurons and neuronal networks. Astroglia express steroid hormone receptors and show rapid responses to hormonal manipulations. However, despite important sex differences in the cortex and hippocampus, few studies have examined sex differences in astroglial cells in telencephalic development. To characterize the cortical astroglial translatome in male and female mice across postnatal development, we use translating ribosome affinity purification together with RNA sequencing and immunohistochemistry to phenotype astroglia at six developmental time points. Overall, we find two distinct astroglial phenotypes between early (P1-P7) and late development (P14-adult), independent of sex. We also find sex differences in gene expression patterns across development that peak at P7 and appear to result from males reaching a mature astroglial phenotype earlier than females. These developmental sex differences could have an impact on the construction of neuronal networks and windows of vulnerability to perturbations and disease.

Muscarinic Acetylcholine Receptor Localization on Distinct Excitatory and Inhibitory Neurons Within the ACC and LPFC of the Rhesus Monkey

Acetylcholine (ACh) can act on pre- and post-synaptic muscarinic receptors (mAChR) in the cortex to influence a myriad of cognitive processes. Two functionally-distinct regions of the prefrontal cortex-the lateral prefrontal cortex (LPFC) and the anterior cingulate cortex (ACC)-are differentially innervated by ascending cholinergic pathways yet, the nature and organization of prefrontal-cholinergic circuitry in primates are not well understood. Using multi-channel immunohistochemical labeling and high-resolution microscopy, we found regional and laminar differences in the subcellular localization and the densities of excitatory and inhibitory subpopulations expressing m1 and m2 muscarinic receptors, the two predominant cortical mAChR subtypes, in the supragranular layers of LPFC and ACC in rhesus monkeys (Macaca mulatta). The subset of m1+/m2+ expressing SMI-32+ pyramidal neurons labeled in layer 3 (L3) was denser in LPFC than in ACC, while m1+/m2+ SMI-32+ neurons co-expressing the calcium-binding protein, calbindin (CB) was greater in ACC. Further, we found between-area differences in laminar m1+ dendritic expression, and m2+ presynaptic localization on cortico-cortical (VGLUT1+) and sub-cortical inputs (VGLUT2+), suggesting differential cholinergic modulation of top-down vs. bottom-up inputs in the two areas. While almost all inhibitory interneurons-identified by their expression of parvalbumin (PV+), CB+, and calretinin (CR+)-expressed m1+, the localization of m2+ differed by subtype and area. The ACC exhibited a greater proportion of m2+ inhibitory neurons compared to the LPFC and had a greater density of presynaptic m2+ localized on inhibitory (VGAT+) inputs targeting proximal somatodendritic compartments and axon initial segments of L3 pyramidal neurons. These data suggest a greater capacity for m2+-mediated cholinergic suppression of inhibition in the ACC compared to the LPFC. The anatomical localization of muscarinic receptors on ACC and LPFC micro-circuits shown here contributes to our understanding of diverse cholinergic neuromodulation of functionally-distinct prefrontal areas involved in goal-directed behavior, and how these interactions maybe disrupted in neuropsychiatric and neurological conditions.

Myelination Deficits in the Auditory Brainstem of a Mouse Model of Fragile X Syndrome

Auditory symptoms are one of the most frequent sensory issues described in people with Fragile X Syndrome (FXS), the most common genetic form of intellectual disability. However, the mechanisms that lead to these symptoms are under explored. In this study, we examined whether there are defects in myelination in the auditory brainstem circuitry. Specifically, we studied myelinated fibers that terminate in the Calyx of Held, which encode temporally precise sound arrival time, and are some of the most heavily myelinated axons in the brain. We measured anatomical myelination characteristics using coherent anti-stokes Raman spectroscopy (CARS) and electron microscopy (EM) in a FXS mouse model in the medial nucleus of the trapezoid body (MNTB) where the Calyx of Held synapses. We measured number of mature oligodendrocytes (OL) and oligodendrocyte precursor cells (OPCs) to determine if changes in myelination were due to changes in the number of myelinating or immature glial cells. The two microscopy techniques (EM and CARS) showed a decrease in fiber diameter in FXS mice. Additionally, EM results indicated reductions in myelin thickness and axon diameter, and an increase in g-ratio, a measure of structural and functional myelination. Lastly, we showed an increase in both OL and OPCs in MNTB sections of FXS mice suggesting that the myelination phenotype is not due to an overall decrease in number of myelinating OLs. This is the first study to show that a myelination defects in the auditory brainstem that may underly auditory phenotypes in FXS.

Toxic Substance-induced Hippocampal Neurodegeneration in Rodents as Model of Alzheimer’s Dementia

BACKGROUND: Alzheimer’s Dementia (AD) cases are increasing with the global elderly population. To study the part of the brain affected by AD, animal models for hippocampal degeneration are still necessary to better understand AD pathogenesis and develop treatment and prevention measures. AIM: This study was a systematic review of toxic substance-induced animal models of AD using the Morris Water Maze method in determining hippocampal-related memory impairment. Our aim was reviewing the methods of AD induction using toxic substances in laboratory rodents and evaluating the report of the AD biomarkers reported in the models. METHODS: Data were obtained from articles in the PubMed database, then compiled, categorized, and analyzed. Eighty studies published in the past 5 years were included for analysis. RESULTS AND DISCUSSION: The most widely used method was intracerebroventricular injection of amyloid-β _substances. However, some less technically challenging techniques using oral or intraperitoneal administration of other toxic substances also produce successful models. Instead of hippocampal neurodegeneration, many studies detected biomarkers of the AD pathological process while some reported inflammation, oxidative stress, neurotrophic factors, and changes of cholinergic activity. Female animals were underrepresented despite a high incidence of AD in women. CONCLUSION: Toxic substances may be used to develop AD animal models characterized with appropriate AD pathological markers. Characterization of methods with the most easy-handling techniques and more studies in female animal models should be encouraged.

Rab7 reduces α-synuclein toxicity in rats and primary neurons

During the pathogenesis of Parkinson's disease (PD), aggregation of alpha-synuclein (αSyn) induces a vicious cycle of cellular impairments that lead to neurodegeneration. Consequently, removing toxic αSyn aggregates constitutes a plausible strategy against PD. In this work, we tested whether stimulating the autolysosomal degradation of αSyn aggregates through the Ras-related in brain 7 (Rab7) pathway can reverse αSyn-induced cellular impairment and prevent neurodegeneration in vivo. The disease-related A53T mutant of αSyn was expressed in primary neurons and in dopaminergic neurons of the rat brain simultaneously with wild type (WT) Rab7 or the T22N mutant as negative control. The cellular integrity was quantified by morphological and biochemical analyses. In primary neurons, WT Rab7 rescued the αSyn-induced loss of neurons and neurites. Furthermore, Rab7 decreased the amount of reactive oxygen species and the amount of Triton X-100 insoluble αSyn. In rat brain, WT Rab7 reduced αSyn-induced loss of dopaminergic axon terminals in the striatum and the loss of dopaminergic dendrites in the substantia nigra pars reticulata. Further, WT Rab7 lowered αSyn pathology as quantified by phosphorylated αSyn staining. Finally, WT Rab7 attenuated αSyn-induced DNA damage in primary neurons and rat brain. In brief, Rab7 reduced αSyn-induced pathology, ameliorated αSyn-induced neuronal degeneration, oxidative stress and DNA damage. These findings indicate that Rab7 is able to disrupt the vicious cycle of cellular impairment, αSyn pathology and neurodegeneration present in PD. Stimulation of Rab7 and the autolysosomal degradation pathway could therefore constitute a beneficial strategy for PD.

Cortical Serotonergic and Catecholaminergic Denervation in MPTP-Treated Parkinsonian Monkeys

Decreased cortical serotonergic and catecholaminergic innervation of the frontal cortex has been reported at early stages of Parkinson's disease (PD). However, the limited availability of animal models that exhibit these pathological features has hampered our understanding of the functional significance of these changes during the course of the disease. In the present study, we assessed longitudinal changes in cortical serotonin and catecholamine innervation in motor-symptomatic and asymptomatic monkeys chronically treated with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Densitometry and unbiased stereological techniques were used to quantify changes in serotonin and tyrosine hydroxylase (TH) immunoreactivity in frontal cortices of 3 control monkeys and 3 groups of MPTP-treated monkeys (motor-asymptomatic [N = 2], mild parkinsonian [N = 3], and moderate parkinsonian [N = 3]). Our findings revealed a significant decrease (P < 0.001) in serotonin innervation of motor (Areas 4 and 6), dorsolateral prefrontal (Areas 9 and 46), and limbic (Areas 24 and 25) cortical areas in motor-asymptomatic MPTP-treated monkeys. Both groups of symptomatic MPTP-treated animals displayed further serotonin denervation in these cortical regions (P < 0.0001). A significant loss of serotonin-positive dorsal raphe neurons was found in the moderate parkinsonian group. On the other hand, the intensity of cortical TH immunostaining was not significantly affected in motor asymptomatic MPTP-treated monkeys, but underwent a significant reduction in the moderate symptomatic group (P < 0.05). Our results indicate that chronic intoxication with MPTP induces early pathology in the corticopetal serotonergic system, which may contribute to early non-motor symptoms in PD.

The thrombin receptor modulates astroglia-neuron trophic coupling and neural repair after spinal cord injury

Excessive activation of the thrombin receptor, protease activated receptor 1 (PAR1) is implicated in diverse neuropathologies from neurodegenerative conditions to neurotrauma. PAR1 knockout mice show improved outcomes after experimental spinal cord injury (SCI), however information regarding the underpinning cellular and molecular mechanisms is lacking. Here we demonstrate that genetic blockade of PAR1 in female mice results in improvements in sensorimotor co-ordination after thoracic spinal cord lateral compression injury. We document improved neuron preservation with increases in Synapsin-1 presynaptic proteins and GAP43, a growth cone marker, after a 30 days recovery period. These improvements were coupled to signs of enhanced myelin resiliency and repair, including increases in the number of mature oligodendrocytes, their progenitors and the abundance of myelin basic protein. These significant increases in substrates for neural recovery were accompanied by reduced astrocyte (Serp1) and microglial/monocyte (CD68 and iNOS) pro-inflammatory markers, with coordinate increases in astrocyte (S100A10 and Emp1) and microglial (Arg1) markers reflective of pro-repair activities. Complementary astrocyte-neuron co-culture bioassays suggest astrocytes with PAR1 loss-of-function promote both neuron survival and neurite outgrowth. Additionally, the pro-neurite outgrowth effects of switching off astrocyte PAR1 were blocked by inhibiting TrkB, the high affinity receptor for brain derived neurotrophic factor. Altogether, these studies demonstrate unique modulatory roles for PAR1 in regulating glial-neuron interactions, including the capacity for neurotrophic factor signaling, and underscore its position at neurobiological intersections critical for the response of the CNS to injury and the capacity for regenerative repair and restoration of function.

IGF1 Gene Therapy Reversed Cognitive Deficits and Restored Hippocampal Alterations After Chronic Spinal Cord Injury

The hippocampus is implicated in the generation of memory and learning, processes which involve extensive neuroplasticity. The generation of hippocampal adult-born neurons is particularly regulated by glial cells of the neurogenic niche and the surrounding microenvironment. Interestingly, recent evidence has shown that spinal cord injury (SCI) in rodents leads to hippocampal neuroinflammation, neurogenesis reduction, and cognitive impairments. In this scenario, the aim of this work was to evaluate whether an adenoviral vector expressing IGF1 could reverse hippocampal alterations and cognitive deficits after chronic SCI. SCI caused neurogenesis reduction and impairments of both recognition and working memories. We also found that SCI increased the number of hypertrophic arginase-1 negative microglia concomitant with the decrease of the number of ramified surveillance microglia in the hilus, molecular layer, and subgranular zone of the dentate gyrus. RAd-IGF1 treatment restored neurogenesis and improved recognition and working memory impairments. In addition, RAd-IGF1 gene therapy modulated differentially hippocampal regions. In the hilus and molecular layer, IGF1 gene therapy recovered the number of surveillance microglia coincident with a reduction of hypertrophic microglia cell number. However, in the neurogenic niche, IGF1 reduced the number of ramified microglia and increased the number of hypertrophic microglia, which as a whole expressed arginase-1. In summary, RAd-IGF1 gene therapy might surge as a new therapeutic strategy for patients with hippocampal microglial alterations and cognitive deficits such as those with spinal cord injury and other neurodegenerative diseases.

Outer Retinal Cell Replacement: Putting the Pieces Together

Retinal degenerative diseases (RDDs) affecting photoreceptors (PRs) are one of the most prevalent sources of incurable blindness worldwide. Due to a lack of endogenous repair mechanisms, functional cell replacement of PRs and/or retinal pigmented epithelium (RPE) cells are among the most anticipated approaches for restoring vision in advanced RDD. Human pluripotent stem cell (hPSC) technologies have accelerated development of outer retinal cell therapies as they provide a theoretically unlimited source of donor cells. Human PSC-RPE replacement therapies have progressed rapidly, with several completed and ongoing clinical trials. Although potentially more promising, hPSC-PR replacement therapies are still in their infancy. A first-in-human trial of hPSC-derived neuroretinal transplantation has recently begun, but a number of questions regarding survival, reproducibility, functional integration, and mechanism of action remain. The discovery of biomaterial transfer between donor and PR cells has highlighted the need for rigorous safety and efficacy studies of PR replacement. In this review, we briefly discuss the history of neuroretinal and PR cell transplantation to identify remaining challenges and outline a stepwise approach to address specific pieces of the outer retinal cell replacement puzzle.

Chronic chemogenetic stimulation of the anterior olfactory nucleus reduces newborn neuron survival in the adult mouse olfactory bulb

During adult rodent life, newborn neurons are added to the olfactory bulb (OB) in a tightly controlled manner. Upon arrival in the OB, input synapses from the local bulbar network and the higher olfactory cortex precede the formation of functional output synapses, indicating a possible role for these regions in newborn neuron survival. An interplay between the environment and the piriform cortex in the regulation of newborn neuron survival has been suggested. However, the specific network and the neuronal cell types responsible for this effect have not been elucidated. Furthermore, the role of the other olfactory cortical areas in this process is not known. Here we demonstrate that pyramidal neurons in the mouse anterior olfactory nucleus, the first cortical area for odor processing, have a key role in the survival of newborn neurons. Using DREADD (Designer Receptors Exclusively Activated by Designer Drugs) technology, we applied chronic stimulation to the anterior olfactory nucleus and observed a decrease in newborn neurons in the OB through induction of apoptosis. These findings provide further insight into the network regulating neuronal survival in adult neurogenesis and strengthen the importance of the surrounding network for sustained integration of new neurons.

Stereology and three-dimensional reconstructions to analyze the pulmonary vasculature

The pulmonary vasculature consists of a large arterial and venous tree with a vast alveolar capillary network (ACN) in between. Both conducting blood vessels and the gas-exchanging capillaries are part of important human lung diseases, including bronchopulmonary dysplasia, pulmonary hypertension and chronic obstructive pulmonary disease. Morphological tools to investigate the different parts of the pulmonary vasculature quantitatively and in three dimensions are crucial for a better understanding of the contribution of the blood vessels to the pathophysiology and effects of lung diseases. In recent years, new stereological methods and imaging techniques have expanded the analytical tool box and therefore the conclusive power of morphological analyses of the pulmonary vasculature. Three of these developments are presented and discussed in this review article, namely (1) stereological quantification of the number of capillary loops, (2) serial block-face scanning electron microscopy of the ACN and (3) labeling of branching generations in light microscopic sections based on arterial tree segmentations of micro-computed tomography data sets of whole lungs. The implementation of these approaches in research work requires expertise in lung preparation, multimodal imaging at different scales, an advanced IT infrastructure and expertise in image analysis. However, they are expected to provide important data that cannot be obtained by previously existing methodology.

Hippocampal volume and hippocampal neuron density, number and size in schizophrenia: a systematic review and meta-analysis of postmortem studies

Reduced hippocampal volume is a consistent finding in neuroimaging studies of individuals with schizophrenia. While these studies have the advantage of large-sample sizes, they are unable to quantify the cellular basis of structural or functional changes. In contrast, postmortem studies are well suited to explore subfield and cellular alterations, but low sample sizes and subject heterogeneity impede establishment of statistically significant differences. Here we use a meta-analytic approach to synthesize the extant literature of hippocampal subfield volume and cellular composition in schizophrenia patients and healthy control subjects. Following pre-registration (PROSPERO CRD42019138280), PubMed, Web of Science, and PsycINFO were searched using the term: (schizophrenia OR schizoaffective) AND (post-mortem OR postmortem) AND hippocampus. Subjects were adult men and women with schizophrenia or schizoaffective disorder or non-psychiatric control subjects, and key outcomes, stratified by hippocampal hemisphere and subfield, were volume, neuron number, neuron density, and neuron size. A random effects meta-analysis was performed. Thirty-two studies were included (413 patients, 415 controls). In patients, volume and neuron number were significantly reduced in multiple hippocampal subfields in left, but not right hippocampus, whereas neuron density was not significantly different in any hippocampal subfield. Neuron size, averaged bilaterally, was also significantly reduced in all calculated subfields. Heterogeneity was minimal to moderate, with rare evidence of publication bias. Meta-regression of age and illness duration did not explain heterogeneity of total hippocampal volume effect sizes. These results extend neuroimaging findings of smaller hippocampal volume in schizophrenia patients and further our understanding of regional and cellular neuropathology in schizophrenia.

A new method for physical disector analyses of numbers and mean volumes of immunohistochemically labeled cells in paraffin sections

BACKGROUND

In the neurosciences, the physical disector method represents an established quantitative stereological method for unbiased sampling and counting of cells in histological tissue sections of known thickness. Physical disector analyses are conventionally performed using plastic-embedded tissue samples, because plastic-embedding causes a comparably low and definable shrinkage of the embedded tissue, and the thickness of thin plastic sections can be determined adequately. However, immunohistochemistry protocols often don't work satisfactorily in sections of plastic-embedded tissue.

NEW METHOD

Here, a new methodological approach is presented, allowing for physical disector analyses of immunohistochemically labeled cells in paraffin sections. The embedding-related tissue shrinkage is standardized by using defined tissue sample volumes and paraffin volumes, and the extent of tissue shrinkage can be determined accurately from the sample volumes prior to and after embedding. Co-embedding of polyethylene section thickness standards together with the tissue samples allows the precise determination of individual paraffin section thicknesses by spectral reflectance measurements.

RESULTS AND COMPARISON WITH EXISTING METHOD(S)

The applicability of the new method is demonstrated by physical disector analysis of immunohistochemically identified somatotroph cells in paraffin sections of porcine pituitary gland tissue. With consideration of individual shrinkage factors and section thicknesses, the cell numbers and mean volumes estimated in paraffin disector sections do not significantly differ from the results obtained by analyses of plastic-embedded pituitary tissue samples of the identical animals (2.4% average difference).

CONCLUSIONS

The featured method enables combination of paraffin section immunohistochemistry and physical disector analyses for unbiased quantitative stereological analyses of different cell types.

Widespread, Specific, and Efficient Transgene Expression in Oligodendrocytes After Intracerebral and Intracerebroventricular Delivery of Viral Vectors in Rodent Brain

Several neurodegenerative disorders are characterized by oligodendroglial pathology and myelin loss. Oligodendrogliopathies are a group of rare diseases for which there currently is no therapy. Gene delivery through viral vectors to oligodendrocytes is a potential strategy to deliver therapeutic molecules to oligodendrocytes for disease modification. However, targeting oligodendroglial cells in vivo is challenging due to their widespread distribution in white and gray matter. In this study, we aimed to address several of these difficulties by designing and testing different oligodendroglial targeting vectors in rat and mouse brain, utilizing different promoters, serotypes, and delivery routes. We found that different oligodendroglial promoters (myelin basic protein [MBP], cytomegalovirus-enhanced MBP, and myelin-associated glycoprotein [MAG]) vary considerably in their ability to drive oligodendroglial transgene expression and different viral vector serotypes (rAAV2/7, rAAV2/8, and rAAV2/9) exhibit varying efficacies in transducing oligodendrocytes. Different administration routes through intracerebral or intraventricular injection allow widespread targeting of mature oligodendrocytes. Delivery of rAAV2/9-MAG-GFP into the cerebrospinal fluid results in GFP expression along the entire rostrocaudal axis of the spinal cord. Collectively, these results show that oligodendrocytes can be targeted with high specificity and widespread expression, which will be useful for gene therapeutic interventions or disease modeling purposes.

PS1 FAD mutants decrease ephrinB2-regulated angiogenic functions, ischemia-induced brain neovascularization and neuronal survival

Microvascular pathology and ischemic lesions contribute substantially to neuronal dysfunction and loss that lead to Alzheimer disease (AD). To facilitate recovery, the brain stimulates neovascularization of damaged tissue via sprouting angiogenesis, a process regulated by endothelial cell (EC) sprouting and the EphB4/ephrinB2 system. Here, we show that in cultures of brain ECs, EphB4 stimulates the VE-cadherin/Rok-α angiogenic complexes known to mediate sprouting angiogenesis. Importantly, brain EC cultures expressing PS1 FAD mutants decrease the EphB4-stimulated γ-secretase cleavage of ephrinB2 and reduce production of the angiogenic peptide ephrinB2/CTF2, the VE-cadherin angiogenic complexes and EC sprouting and tube formation. These data suggest that FAD mutants may attenuate ischemia-induced brain angiogenesis. Supporting this hypothesis, ischemia-induced VE-cadherin angiogenic complexes, levels of neoangiogenesis marker Endoglin, vascular density, and cerebral blood flow recovery, are all decreased in brains of mouse models expressing PS1 FAD mutants. Ischemia-induced brain neuronal death and cognitive deficits also increase in these mice. Furthermore, a small peptide comprising the C-terminal sequence of peptide ephrinB2/CTF2 rescues angiogenic functions of brain ECs expressing PS1 FAD mutants. Together, our data show that PS1 FAD mutations impede the EphB4/ephrinB2-mediated angiogenic functions of ECs and impair brain neovascularization, neuronal survival and cognitive recovery following ischemia. Furthermore, our data reveal a novel brain angiogenic mechanism targeted by PS1 FAD mutants and a potential therapeutic target for ischemia-induced neurodegeneration. Importantly, FAD mutant effects occur in absence of neuropathological hallmarks of AD, supporting that such hallmarks may form downstream of mutant effects on neoangiogenesis and neuronal survival.

Growth restricted placentas show severely reduced volume of villous components with perivascular myofibroblasts

INTRODUCTION

The restricted placental growth in IUGR is associated with a simultaneous weight and volume restriction for the placental villous tree. It is unknown whether the whole villous tree or only specific parts of it are growth restricted in IUGR. In the case of uniform growth restriction of the villous tree, IUGR placentas could be interpreted as symmetrically smaller versions of normal placentas. Otherwise, IUGR placentas would be morphologically, developmentally and, therefore, functionally different from normal placentas.

METHODS

We investigated ten normal and eleven IUGR placentas with quantitative microscopic techniques. Using immunohistochemical detection of placental myofibroblasts (γ-sm-actin) and foetoplacental endothelium (CD34), we distinguished between more centrally located villi showing the presence of myofibroblasts (contractile villi; C-villi) and more peripherally located villi showing the absence of myofibroblasts (noncontractile villi; NC-villi).

RESULTS

Compared to normal placentas, IUGR placentas showed significantly reduced mean volume of C-villi, but not of NC-villi. The volume of vessels in both, C-villi and NC-villi, was significantly reduced in IUGR. Additional stereologic estimates confirmed the known alterations in the morphology of NC-villi in IUGR.

DISCUSSION

Our results suggest that IUGR placentas are not just smaller but morphologically (and therefore functionally) different from normal placentas. We propose that the reduced volume of C-villi and vessels in C-villi reflects a developmental disturbance in the formation of C-villi, which are mostly composed of stem villi. As such, key pathological villous alterations in IUGR placentas could begin before the formation of intermediate and terminal villi, possibly already in the late first trimester of pregnancy.

Studying nerve transfers: Searching for a consensus in nerve axons count

Axonal count is the base for efficient nerve transfer; despite its capital importance, few studies have been published on human material, most research approaches being performed on experimental animal models of nerve injury. Thus, standard analysis methods are still lacking. Quantitative data obtained have to be reproducible and comparable with published data by other research groups. To share results with the scientific community, the standardization of quantitative analysis is a fundamental step. For this purpose, the experiences of the Italian, Austrian, German, Greek, and Iberian-Latin American groups have been compared with each other and with the existing literature to reach a consensus in the fiber count and draw up a protocol that can make future studies from different centers comparable. The search for a standardization of the methodology was aimed to reduce all the factors that are associated with an increase in the variability of the results. All the preferential methods to be used have been suggested. On the other hand, alternative methods and different methods have been identified to achieve the same goal, which in our experience are completely comparable; therefore, they can be used indifferently by the different centers according to their experience and availability.

LRRK2 Ablation Attenuates Αlpha-Synuclein-Induced Neuroinflammation Without Affecting Neurodegeneration or Neuropathology In Vivo

The development of disease-modifying therapies for Parkinson's disease is a major challenge which would be facilitated by a better understanding of the pathogenesis. Leucine-rich repeat kinase 2 (LRRK2) and α-synuclein are key players in Parkinson's disease, but their relationship remains incompletely resolved. Previous studies investigating the effect of LRRK2 on α-synuclein-induced neurotoxicity and neuroinflammation in preclinical Parkinson's disease models have reported conflicting results. Here, we aimed to further explore the functional interaction between α-synuclein and LRRK2 and to evaluate the therapeutic potential of targeting physiological LRRK2 levels. We studied the effects of total LRRK2 protein loss as well as pharmacological LRRK2 kinase inhibition in viral vector-mediated α-synuclein-based Parkinson's disease models developing early- and late-stage neurodegeneration. Surprisingly, total LRRK2 ablation or in-diet treatment with the LRRK2 kinase inhibitor MLi-2 did not significantly modify α-synuclein-induced motor deficits, dopaminergic cell loss, or α-synuclein pathology. Interestingly, we found a significant effect on α-synuclein-induced neuroinflammatory changes in the absence of LRRK2, with a reduced microglial activation and CD4+ and CD8+ T cell infiltration. This observed lack of protection against α-synuclein-induced toxicity should be well considered in light of the ongoing therapeutic development of LRRK2 kinase inhibitors for idiopathic Parkinson's disease. Future studies will be crucial to understand the link between these neuroinflammatory processes and disease progression as well as the role of α-synuclein and LRRK2 in these pathological events.

Biomarkers of lesion severity in a rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION)

The rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION) is similar in many of its pathophysiological responses to clinical NAION. Like human NAION, there is significant variability in the severity of the lesion produced, and little is known of the parameters associated with rNAION induction severity or if pre- or early post-induction biomarkers can be identified that enable prediction of lesion severity and ultimate loss of retinal ganglion cells (RGCs). Adult male Sprague-Dawley outbred rats were evaluated for various parameters including physiological characteristics (heart rate, respiratory rate, temperature, hematocrit [Hct]), optic nerve head (ONH) appearance, pre- and post-induction mean diameter, and intravenous fluorescein and indocyanine green angiographic patterns of vascular leakage at 5 hours post-induction, performed using a spectral domain-optical coherence tomography (SD-OCT) instrument. Early changes were correlated with ultimate RGC loss by Brn3a (+) immunohistology. RGC loss also was correlated with the relative level of laser exposure. The severity of ONH edema 2d, but not 5hr, post induction was most closely associated with the degree of RGC loss, revealing a threshold effect, and consistent with a compartment syndrome where a minimum level of capillary compression within a tight space is responsible for damage. RGC loss increased dramatically as the degree of laser exposure increased. Neither physiological parameters nor the degree of capillary leakage 5hr post induction were informative as to the ultimate degree of RGC loss. Similar to human NAION, the rNAION model exhibits marked variability in lesion severity. Unlike clinical NAION, pre-induction ONH diameter likely does not contribute to ultimate lesion severity; however, cross-sectional ONH edema can be used as a biomarker 2d post-induction to determine randomization of subjects prior to inclusion in specific neuroprotection or neuroregeneration studies.

Serial Block-Face Scanning Electron Microscopy (SBF-SEM) of Biological Tissue Samples

Serial block-face scanning electron microscopy (SBF-SEM) allows for the collection of hundreds to thousands of serially-registered ultrastructural images, offering an unprecedented three-dimensional view of tissue microanatomy. While SBF-SEM has seen an exponential increase in use in recent years, technical aspects such as proper tissue preparation and imaging parameters are paramount for the success of this imaging modality. This imaging system benefits from the automated nature of the device, allowing one to leave the microscope unattended during the imaging process, with the automated collection of hundreds of images possible in a single day. However, without appropriate tissue preparation cellular ultrastructure can be altered in such a way that incorrect or misleading conclusions might be drawn. Additionally, images are generated by scanning the block-face of a resin-embedded biological sample and this often presents challenges and considerations that must be addressed. The accumulation of electrons within the block during imaging, known as "tissue charging," can lead to a loss of contrast and an inability to appreciate cellular structure. Moreover, while increasing electron beam intensity/voltage or decreasing beam-scanning speed can increase image resolution, this can also have the unfortunate side effect of damaging the resin block and distorting subsequent images in the imaging series. Here we present a routine protocol for the preparation of biological tissue samples that preserves cellular ultrastructure and diminishes tissue charging. We also provide imaging considerations for the rapid acquisition of high-quality serial-images with minimal damage to the tissue block.

Design-based stereological study of the guinea-pig (Cavia porcellus) cerebellum

Guinea pigs have proved useful as experimental animal models in studying cerebellar anatomical and structural alterations in human neurological disease; however, they are also currently acquiring increasing veterinary interest as companion animals. The morphometric features of the normal cerebellum in guinea pigs have not been previously investigated using stereology. The objective of the present work was to establish normal volumetric and quantitative stereological parameters for cerebellar tissues in guinea pigs, by means of unbiased design-based stereology. Cerebellar total volume, gray and white matter volume fractions, molecular and granular layers volume fractions, cerebellar surface area, Purkinje cellular and nuclear volumes, and the Purkinje cell total count were stereologically estimated. For this purpose, cerebellar hemispheres from six adult male guinea pigs were employed. Isotropic, uniform random sections were obtained by applying the orientator method, and subsequently processed for light microscopy. The cerebellar total volume, the white and grey matter volume fractions, and the molecular and granular layer volumes were estimated using the Cavalieri's principle and the point counting system. The cerebellar surface area was estimated through the use of test lines; Purkinje cellular and nuclear volumes were analysed using the nucleator technique, whereas the Purkinje cell total count was obtained by means of the optical disector technique. The mean ± standard deviation total volume of a guinea-pig cerebellar hemisphere was 0.11 ± 0.01 cm³ . The mean volumetric proportions occupied by the gray and white matters were, respectively, 78.0 ± 2.6% and 22.0 ± 2.6%, whereas their mean absolute volumes were found to be 0.21 ± 0.02 cm³ and 0.059 ± 0.006 cm³ . The volumes of the molecular and granular layers were estimated at 112.4 ± 20.6 mm³ and 104.4 ± 7.3 mm³ , whereas their mean thicknesses were calculated to be 0.184 ± 0.020 mm and 0.17 ± 0.02 mm. The molecular and granular layers accounted for 40.7 ± 3.9% and 37.4 ± 1.8% of total cerebellar volume respectively. The surface area of the cerebellum measured 611.4 ± 96.8 mm² . Purkinje cells with a cellular volume of 3210.1 µm³ and with a nuclear volume of 470.9 µm³ had a higher incidence of occurrence. The mean total number of Purkinje cells for a cerebellar hemisphere was calculated to be 253,090 ± 34,754. The morphometric data emerging from the present study provide a set of reference data which might prove valuable as basic anatomical contribution for practical applications in veterinary neurology.

Distribution and overlap of entorhinal, premotor, and amygdalar connections in the monkey anterior cingulate cortex

The anterior cingulate cortex (ACC) is important for decision-making as it integrates motor plans with affective and contextual limbic information. Disruptions in these networks have been observed in depression, bipolar disorder, and post-traumatic stress disorder. Yet, overlap of limbic and motor connections within subdivisions of the ACC is not well understood. Hence, we administered a combination of retrograde and anterograde tracers into structures important for contextual memories (entorhinal cortex), affective processing (amygdala), and motor planning (dorsal premotor cortex) to assess overlap of labeled projection neurons from (outputs) and axon terminals to (inputs) the ACC of adult rhesus monkeys (Macaca mulatta). Our data show that entorhinal and dorsal premotor cortical (dPMC) connections are segregated across ventral (A25, A24a) and dorsal (A24b,c) subregions of the ACC, while amygdalar connections are more evenly distributed across subregions. Among all areas, the rostral ACC (A32) had the lowest relative density of connections with all three regions. In the ventral ACC, entorhinal and amygdalar connections strongly overlap across all layers, especially in A25. In the dorsal ACC, outputs to dPMC and the amygdala strongly overlap in deep layers. However, dPMC input to the dorsal ACC was densest in deep layers, while amygdalar inputs predominantly localized in upper layers. These connection patterns are consistent with diverse roles of the dorsal ACC in motor evaluation and the ventral ACC in affective and contextual memory. Further, distinct laminar circuits suggest unique interactions within specific ACC compartments that are likely important for the temporal integration of motor and limbic information during flexible goal-directed behavior.

Human brain pathology in myotonic dystrophy type 1: A systematic review

Brain involvement in myotonic dystrophy type 1 (DM1) is characterized by heterogeneous cognitive, behavioral, and affective symptoms and imaging alterations indicative of widespread grey and white matter involvement. The aim of the present study was to systematically review the literature on brain pathology in DM1. We conducted a structured search in EMBASE (index period 1974–2017) and MEDLINE (index period 1887–2017) on December 11, 2017, using free text and index search terms related to myotonic dystrophy type 1 and brain structures or regions. Eligible studies were full‐text studies reporting on microscopic brain pathology of DM1 patients without potentially interfering comorbidity. We discussed the findings based on the anatomical region and the nature of the anomaly. Neuropathological findings in DM1 can be classified as follows: (1) protein and nucleotide deposits; (2) changes in neurons and glial cells; and (3) white matter alterations. Most findings are unspecific to DM1 and may occur with physiological aging, albeit to a lesser degree. There are similarities and contrasts with Alzheimer's disease; both show the appearance of neurofibrillary tangles in the limbic system without plaque occurrence. Likewise, there is myelin loss and gliosis, and there are dilated perivascular spaces in the white matter resemblant of cerebral small vessel disease. However, we did not find evidence of lacunar infarction or microbleeding. The various neuropathological findings in DM1 are reflective of the heterogeneous clinical and neuroimaging features of the disease. The strength of conclusions from this study's findings is bounded by limited numbers of participants in studies, methodological constraints, and lack of assessed associations between histopathology and clinical or neuroimaging findings.

Accumulation of neurofibrillary tangles and activated microglia is associated with lower neuron densities in the aphasic variant of Alzheimer's disease

The neurofibrillary tangles (NFT) and amyloid-ß plaques (AP) that comprise Alzheimer's disease (AD) neuropathology are associated with neurodegeneration and microglial activation. Activated microglia exist on a dynamic spectrum of morphologic subtypes that include resting, surveillant microglia capable of converting to activated, hypertrophic microglia closely linked to neuroinflammatory processes and AD neuropathology in amnestic AD. However, quantitative analyses of microglial subtypes and neurons are lacking in non-amnestic clinical AD variants, including primary progressive aphasia (PPA-AD). PPA-AD is a language disorder characterized by cortical atrophy and NFT densities concentrated to the language-dominant hemisphere. Here, a stereologic investigation of five PPA-AD participants determined the densities and distributions of neurons and microglial subtypes to examine how cellular changes relate to AD neuropathology and may contribute to cortical atrophy. Adjacent series of sections were immunostained for neurons (NeuN) and microglia (HLA-DR) from bilateral language and non-language regions where in vivo cortical atrophy and Thioflavin-S-positive APs and NFTs were previously quantified. NeuN-positive neurons and morphologic subtypes of HLA-DR-positive microglia (i.e., resting [ramified] microglia and activated [hypertrophic] microglia) were quantified using unbiased stereology. Relationships between neurons, microglia, AD neuropathology, and cortical atrophy were determined using linear mixed models. NFT densities were positively associated with hypertrophic microglia densities (P < 0.01) and inversely related to neuron densities (P = 0.01). Hypertrophic microglia densities were inversely related to densities of neurons (P < 0.01) and ramified microglia (P < 0.01). Ramified microglia densities were positively associated with neuron densities (P = 0.02) and inversely related to cortical atrophy (P = 0.03). Our findings provide converging evidence of divergent roles for microglial subtypes in patterns of neurodegeneration, which includes hypertrophic microglia likely driving a neuroinflammatory response more sensitive to NFTs than APs in PPA-AD. Moreover, the accumulation of both NFTs and activated hypertrophic microglia in association with low neuron densities suggest they may collectively contribute to focal neurodegeneration characteristic of PPA-AD.

Hesperidin protects against behavioral alterations and loss of dopaminergic neurons in 6-OHDA-lesioned mice: the role of mitochondrial dysfunction and apoptosis

Hesperidin is a flavonoid glycoside that is frequently found in citrus fruits. Our group have demonstrated that hesperidin has neuroprotective effect in 6-hydroxydopamine (6-OHDA) model of Parkinson's disease (PD), mainly by antioxidant mechanisms. Although the pathophysiology of PD remains uncertain, a large body of evidence has demonstrated that mitochondrial dysfunction and apoptosis play a critical role in dopaminergic nigrostriatal degeneration. However, the ability of hesperidin in modulating these mechanisms has not yet been investigated. In the present study, we examined the potential of a 28-day hesperidin treatment (50 mg/kg/day, p.o.) in preventing behavioral alterations induced by 6-OHDA injection via regulating mitochondrial dysfunction, apoptosis and dopaminergic neurons in the substantia nigra pars compacta (SNpc) in C57BL/6 mice. Our results demonstrated that hesperidin treatment improved motor, olfactory and spatial memory impairments elicited by 6-OHDA injection. Moreover, hesperidin treatment attenuated the loss of dopaminergic neurons (TH+ cells) in the SNpc and the depletion of dopamine (DA) and its metabolities 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum of 6-OHDA-lesioned mice. Hesperidin also protected against the inhibition of mitochondrial respiratory chain complex-I, -IV and V, the decrease of Na + -K + -ATPase activity and the increase of caspase-3 and -9 activity in the striatum. Taken together, our findings indicate that hesperidin mitigates the degeneration of dopaminergic neurons in the SNpc by preventing mitochondrial dysfunction and modulating apoptotic pathways in the striatum of 6-OHDA-treated mice, thus improving behavioral alterations. These results provide new insights on neuroprotective mechanisms of hesperidin in a relevant preclinical model of PD.

A practical guide to unbiased quantitative morphological analyses of the gills of rainbow trout (Oncorhynchus mykiss) in ecotoxicological studies

Rainbow trout (Oncorhynchus mykiss) are frequently used as experimental animals in ecotoxicological studies, in which they are experimentally exposed to defined concentrations of test substances, such as heavy metals, pesticides, or pharmaceuticals. Following exposure to a broad variety of aquatic pollutants, early morphologically detectable toxic effects often manifest in alterations of the gills. Suitable methods for an accurate and unbiased quantitative characterization of the type and the extent of morphological gill alterations are therefore essential prerequisites for recognition, objective evaluation and comparison of the severity of gill lesions. The aim of the present guidelines is to provide practicable, standardized and detailed protocols for the application of unbiased quantitative stereological analyses of relevant morphological parameters of the gills of rainbow trout. These gill parameters inter alia include the total volume of the primary and secondary gill lamellae, the surface area of the secondary gill lamellae epithelium (i.e., the respiratory surface) and the thickness of the diffusion barrier. The featured protocols are adapted to fish of frequently used body size classes (300-2000 g). They include well-established, conventional sampling methods, probes and test systems for unbiased quantitative stereological analyses of light- and electron microscopic 2-D gill sections, as well as the application of modern 3-D light sheet fluorescence microscopy (LSFM) of optically cleared gill samples as an innovative, fast and efficient quantitative morphological analysis approach. The methods shown here provide a basis for standardized and representative state-of-the-art quantitative morphological analyses of trout gills, ensuring the unbiasedness and reproducibility, as well as the intra- and inter-study comparability of analyses results. Their broad implementation will therefore significantly contribute to the reliable identification of no observed effect concentration (NOEC) limits in ecotoxicological studies and, moreover, to limit the number of experimental animals by reduction of unnecessary repetition of experiments.