Astrocytes display ultrastructural alterations and heterogeneity in the hippocampus of aged APP-PS1 mice and human post-mortem brain samples.

The past decade has witnessed increasing evidence for a crucial role played by glial cells, notably astrocytes, in Alzheimer's disease (AD). To provide novel insights into the roles of astrocytes in the pathophysiology of AD, we performed a quantitative ultrastructural characterization of their intracellular contents and parenchymal interactions in an aged mouse model of AD pathology, as aging is considered the main risk factor for developing AD. We compared 20-month-old APP-PS1 and age-matched C57BL/6J male mice, among the ventral hippocampus CA1 strata lacunosum-moleculare and radiatum, two hippocampal layers severely affected by AD pathology. Astrocytes in both layers interacted more with synaptic elements and displayed more ultrastructural markers of increased phagolysosomal activity in APP-PS1 versus C57BL6/J mice. In addition, we investigated the ultrastructural heterogeneity of astrocytes, describing in the two examined layers a dark astrocytic state that we characterized in terms of distribution, interactions with AD hallmarks, and intracellular contents. This electron-dense astrocytic state, termed dark astrocytes, was observed throughout the hippocampal parenchyma, closely associated with the vasculature, and possessed several ultrastructural markers of cellular stress. A case study exploring the hippocampal head of an aged human post-mortem brain sample also revealed the presence of a similar electron-dense, dark astrocytic state. Overall, our study provides the first ultrastructural quantitative analysis of astrocytes among the hippocampus in aged AD pathology, as well as a thorough characterization of a dark astrocytic state conserved from mouse to human.

Fibulin-2 is an extracellular matrix inhibitor of oligodendrocytes relevant to multiple sclerosis.

Impairment of oligodendrocytes and myelin contributes to neurological disorders including multiple sclerosis (MS), stroke, and Alzheimer's disease. Regeneration of myelin (remyelination) decreases the vulnerability of demyelinated axons, but this repair process commonly fails with disease progression. A contributor to inefficient remyelination is the altered extracellular matrix (ECM) in lesions, which remains to be better defined. We have identified fibulin-2 (FBLN2) as a highly upregulated ECM component in lesions of MS and stroke and in proteome databases of Alzheimer's disease and traumatic brain injury. Focusing on MS, the inhibitory role of FBLN2 was suggested in the experimental autoimmune encephalomyelitis (EAE) model, in which genetic FBLN2 deficiency improved behavioral recovery by promoting the maturation of oligodendrocytes and enhancing remyelination. Mechanistically, when oligodendrocyte progenitors were cultured in differentiation medium, FBLN2 impeded their maturation into oligodendrocytes by engaging the Notch pathway, leading to cell death. Adeno-associated virus deletion of FBLN2 in astrocytes improved oligodendrocyte numbers and functional recovery in EAE and generated new myelin profiles after lysolecithin-induced demyelination. Collectively, our findings implicate FBLN2 as a hitherto unrecognized injury-elevated ECM, and a therapeutic target, that impairs oligodendrocyte maturation and myelin repair.

Emerging epigenetic dynamics in gut-microglia brain axis: experimental and clinical implications for accelerated brain aging in schizophrenia.

Brain aging, which involves a progressive loss of neuronal functions, has been reported to be premature in probands affected by schizophrenia (SCZ). Evidence shows that SCZ and accelerated aging are linked to changes in epigenetic clocks. Recent cross-sectional magnetic resonance imaging analyses have uncovered reduced brain reserves and connectivity in patients with SCZ compared to typically aging individuals. These data may indicate early abnormalities of neuronal function following cyto-architectural alterations in SCZ. The current mechanistic knowledge on brain aging, epigenetic changes, and their neuropsychiatric disease association remains incomplete. With this review, we explore and summarize evidence that the dynamics of gut-resident bacteria can modulate molecular brain function and contribute to age-related neurodegenerative disorders. It is known that environmental factors such as mode of birth, dietary habits, stress, pollution, and infections can modulate the microbiota system to regulate intrinsic neuronal activity and brain reserves through the vagus nerve and enteric nervous system. Microbiota-derived molecules can trigger continuous activation of the microglial sensome, groups of receptors and proteins that permit microglia to remodel the brain neurochemistry based on complex environmental activities. This remodeling causes aberrant brain plasticity as early as fetal developmental stages, and after the onset of first-episode psychosis. In the central nervous system, microglia, the resident immune surveillance cells, are involved in neurogenesis, phagocytosis of synapses and neurological dysfunction. Here, we review recent emerging experimental and clinical evidence regarding the gut-brain microglia axis involvement in SCZ pathology and etiology, the hypothesis of brain reserve and accelerated aging induced by dietary habits, stress, pollution, infections, and other factors. We also include in our review the possibilities and consequences of gut dysbiosis activities on microglial function and dysfunction, together with the effects of antipsychotics on the gut microbiome: therapeutic and adverse effects, role of fecal microbiota transplant and psychobiotics on microglial sensomes, brain reserves and SCZ-derived accelerated aging. We end the review with suggestions that may be applicable to the clinical setting. For example, we propose that psychobiotics might contribute to antipsychotic-induced therapeutic benefits or adverse effects, as well as reduce the aging process through the gut-brain microglia axis. Overall, we hope that this review will help increase the understanding of SCZ pathogenesis as related to chronobiology and the gut microbiome, as well as reveal new concepts that will serve as novel treatment targets for SCZ.

Manual versus automatic analysis of microglial density and distribution: a comparison in the hippocampus of healthy and lipopolysaccharide-challenged mature male mice.

Microglia, the immune resident cells of the central nervous system (CNS), are now recognized as performing crucial roles for maintaining homeostasis and determining the outcomes of various pathological challenges across life. While brightfield microscopy is a powerful and established tool to study microglia-mediated mechanisms underlying neurological diseases, microglial density and distribution are some of the most frequently investigated parameters. Their quantitative assessment provides relevant clues regarding dynamic densitometric changes in the microglial population across various CNS regions. Investigators often rely on a manual identification and analysis of these cells within key regions of interest, which can be time-consuming and introduce an experimenter bias. Automation of this process, which has been gaining popularity in recent years, represents a potential solution to minimize both experimenter's bias and time investment, thus increasing the efficacy of the experiment and uniformity of the collected data. We aimed to compare manual versus automatic analysis methods to determine whether an automatic analysis is efficient and accurate enough to replace a manual analysis in both homeostatic and pathological contexts (i.e., adult healthy and lipopolysaccharide-challenged adolescent male mice, respectively). To do so, we used a script that runs on the ImageJ software to perform microglial density analysis by automatic detection of microglial cells from brightfield microscopy images. The main core of the macro script consists in an automatic cell selection step using a threshold followed by a spatial analysis for each selected cell. The resulting data were then compared with the values obtained using a well-established manual method. Overall, the evaluation of the established automatic densitometry method with manual density and distribution analysis revealed similar results for the density and nearest neighbor distance in healthy adult mice, as well as density and distribution in lipopolysaccharide-challenged adolescent mice. Applying machine learning to the automatic process could further improve the accuracy and robustness of the method.

Prevalence of Cervical Myofascial Pain Syndrome and its Correlation with the Severity of Pain and Disability in Patients with Chronic Non-specific Neck Pain.

BACKGROUND: Nonspecific chronic neck pain is increasing according to work-related gestures and modern lifestyle. Myofascial pain syndrome is a common problem and may be a primary disease. This study was designed to evaluate the prevalence of cervical myofascial pain syndrome in patients with chronic non-specific neck pain with normal MRI. We also examined the correlation between patients' age as well as pain severity and duration. METHODS: Patients with neck pain radiating to their upper extremity were examined despite normal MRI findings. We evaluated 10 different muscles based on myofascial pain syndrome criteria and also recorded pain intensity and functional ability using visual analogue scale and neck disability index, respectively. A physical therapist with at least 10 years of clinical experience with myofascial pain syndrome performed all physical examinations. RESULTS: A total of 126 patients (69 females and 57 males) participated in this study, out of whom, 14 patients (11.1%) had no muscular involvement, while 112 cases (88.9%) revealed at least one trigger point. The infraspinatus and scalene muscles were the most commonly involved muscles accounting for 38.9% and 34.9% of all the involvements, respectively. The severity of pain was significantly associated with the disability of the patients (r=0.64, P<0.001). However, the correlation between pain and the number of trigger points was not significant (r=-0.19, P=0.31). Finally, the least significantly correlated variables were disability and the number of trigger points (r=-0.17, P=0.05). Patient's age was significantly correlated neither with the number of trigger points (r=-0.04, P=0.62), nor the pain duration (r=0.07, P=0.39). CONCLUSION: Myofascial pain syndrome is a common disorder in patients with nonspecific chronic neck pain, despite normal MRI findings. Although, pain is not correlated with the number of trigger points in these patients, we demonstrated a small correlation between patients' disability and the latter variable.