Aging-related changes of microglia and astrocytes in hypothalamus after intraperitoneal injection of hypertonic saline in rats

Neuronal Stability, Volumetric Changes, and Decrease in GFAP Expression of Marmoset (Callithrix jacchus) Subcortical Visual Nuclei During Aging

The physiological aging process is well known for functional decline in visual abilities. Among the components of the visual system, the dorsal lateral geniculate nucleus (DLG) and superior colliculus (SC) provide a good model for aging investigations, as these structures constitute the main visual pathways for retinal inputs reaching the visual cortex. However, there are limited data available on quantitative morphological and neurochemical aspects in DLG and SC across lifespan. Here, we used optical density to determine immunoexpression of glial fibrillary acidic protein (GFAP) and design-based stereological probes to estimate the neuronal number, total volume, and layer volume of the DLG and SC in marmosets (Callithrix jacchus), ranging from 36 to 143 months of age. Our results revealed an age-related increase in total volume and layer volume of the DLG, with an overall stability in SC volume. Furthermore, a stable neuronal number was demonstrated in DLG and superficial layers of SC (SCv). A decrease in GFAP immunoexpression was observed in both visual centers. The results indicate region-specific variability in volumetric parameter, possibly attributed to structural plastic events in response to inflammation and compensatory mechanisms at the cellular and subcellular level. Additionally, the DLG and SCv seem to be less vulnerable to aging effects in terms of neuronal number. The neuropeptidergic data suggest that reduced GFAP expression may reflect morphological atrophy in the astroglial cells. This study contributes to updating the current understanding of aging effects in the visual system and stablishes a crucial foundation for future research on visual perception throughout the aging process.

Sex as a Determinant of Age-Related Changes in the Brain

The notion of notable anatomical, biochemical, and behavioral distinctions within male and female brains has been a contentious topic of interest within the scientific community over several decades. Advancements in neuroimaging and molecular biological techniques have increasingly elucidated common mechanisms characterizing brain aging while also revealing disparities between sexes in these processes. Variations in cognitive functions; susceptibility to and progression of neurodegenerative conditions, notably Alzheimer's and Parkinson's diseases; and notable disparities in life expectancy between sexes, underscore the significance of evaluating aging within the framework of gender differences. This comprehensive review surveys contemporary literature on the restructuring of brain structures and fundamental processes unfolding in the aging brain at cellular and molecular levels, with a focus on gender distinctions. Additionally, the review delves into age-related cognitive alterations, exploring factors influencing the acceleration or deceleration of aging, with particular attention to estrogen's hormonal support of the central nervous system.

Effect of prenatal exposure of green tea extract on the developing central nervous system of rat fetuses; histological, immune-histochemical and ultrastructural studies

Although, several health benefits were associated with green tea, these effects may be beneficial up to a certain dose. Higher doses of green tea may cause several adverse effects. So, there is a need to test the potential negative effects of green tea during pregnancy. This study was designated to evaluate the effect of prenatal exposure of green tea extract on the development of the central nervous system of 20-day old rat fetuses. The pregnant rats were divided into 4 groups; the control group (received distal water) and the other 3 groups received green tea extract at different doses (200, 600 & 1000 mg/kg/day, respectively) from the 6th to 15th day of gestation i.e., during the organogenesis phase of development. Cerebral cortex, cerebellum and spinal cord specimens were subjected to histological, immunohistochemical and ultrastructure investigations. The body weight of both mothers and fetuses was significantly decreased in the groups that received 600 and 1000 mg green tea extract. Also, the neuronal tissues displayed various signs of degeneration which were evident with the 600 and 1000 mg doses. Green tea extract also increases the glial fibrillary acidic protein (GFAP) and decreases the proliferating cell nuclear antigen (PCNA) which were directly proportional with increasing the dose. Administration of green tea extract during rat organogenesis period induced various histological, immunohistochemical and ultrastructural degenerative changes in the cerebral cortex, cerebellum and spinal cord of 20-day old rat fetuses. These deleterious changes were directly proportional to increasing the green tea extract dose. Thus, it should be stressed that the effect of green tea is dose-dependent and therefore it can be either beneficial or adverse.

Glia: victims or villains of the aging brain?

Aging is the strongest risk factor for metabolic, vascular and neurodegenerative diseases. Aging alone is associated with a gradual decline of cognitive and motor functions. Considering an increasing elderly population in the last century, understanding the cellular and molecular mechanisms contributing to brain aging is of vital importance. Recent genetic and transcriptomic findings strongly suggest that glia are the first cells changing with aging. Glial cells constitute around 50% of the total cells in the brain and play key roles regulating brain homeostasis in health and disease. Their essential functions include providing nutritional support to neurons, activation of immune responses, and regulation of synaptic transmission and plasticity. In this review we discuss how glia are altered in the aging brain and whether these alterations are protective or contribute to the age-related pathological cascade. We focus on the major morphological, transcriptional and functional changes affecting glia in a range of systems, including human, non-human primates, and rodents. We also highlight future directions for investigating the roles of glia in brain aging.

Selective brain neuronal and glial losses without changes in GFAP immunoreactivity: Young versus mature adult Wistar rats

Normal ageing results in brain selective neuronal and glial losses. In the present study we analyze neuronal and glial changes in Wistar rats at two different ages, 45 days (young) and 420 days (mature adult), using Nissl staining and glial fibrillary acidic protein (GFAP) immunohistochemistry associated to the Sholl analysis. Comparing mature adults with young rats we noted the former present a decrease in neuronal density in the cerebral cortex, corpus callosum, pyriform cortex, L.D.D.M., L.D.V.L., central medial thalamic nucleus and zona incerta. A decrease in glial density was found in the dorsomedial and ventromedial hypothalamic nuclei. Additionally, the neuron/glia ratio was reduced in the central medial thalamic nucleus and increased in the habenula. No changes were found in the neuronal and glial densities or neuron/glia ratio in the other studied regions. The number of astrocytic primary processes and the number of intersections counted in the Sholl analysis presented no significant difference in any of the studied regions. Overall, neither GFAP positive astrocytic density nor GFAP immunoreactivity showed alteration.

Changes in vitreal protein profile and retina mRNAs in Reeler mice: NGF, IL33 and Müller cell activation

A possible link between Nerve Growth Factor (NGF) and Reelin might take place during impaired retinal development occurring in the Reelin deficient mouse model (Reeler). To better characterize NGF and retina impairments at the Reeler retina, vitreous and retina were investigated by means of protein expression and glial cell activation. Reeler (n = 9; RELN^-/-) and WT (n = 9; wild-type RELN^+/+, B6C3Fe) mice were analyzed at 14, 21 and 28 postnatal days (p). Retinas and vitreous were subjected to confocal analysis and protein array, followed by conventional analysis. A significant increase of NGF, IL33 and TIMP1, a trend to a decrease of IL12 and IL6, as well as a significant decrease of NT3 were detected in Reeler vitreous, particularly at p28 (p<0.05). MIP3β mRNA was decreased while IL33mRNA was significantly upregulated in Reeler retina. Increased number of GFAP⁺ and Nestin⁺ cells as well as upregulation of Glutamine Synthetase and Nestin mRNAs were observed in Reeler retinas (p<0.05). These findings extend our previous studies on Reeler retina showing a selective Müller cell activation. NGF and IL33 release into vitreous would suggest a local activation of Müller cells, in addition to retinal ganglion and accessory cells. Overall, the data from this experimental study would strength the potential neuroprotective role played by activated Muller cells through NGF release.

Astrocytes and Aging

By 2050, the aging population is predicted to expand by over 100%. Considering this rapid growth, and the additional strain it will place on healthcare resources because of age-related impairments, it is vital that researchers gain a deeper understanding of the cellular interactions that occur with normal aging. A variety of mammalian cell types have been shown to become compromised with age, each with a unique potential to contribute to disease formation in the aging body. Astrocytes represent the largest group of glial cells and are responsible for a variety of essential functions in the healthy central nervous system (CNS). Like other cell types, aging can cause a loss of normal function in astrocytes which reduces their ability to properly maintain a healthy CNS environment, negatively alters their interactions with neighboring cells, and contribute to the heightened inflammatory state characteristic of aging. The goal of this review article is to consolidate the knowledge and research to date regarding the role of astrocytes in aging. In specific, this review article will focus on the morphology and molecular profile of aged astrocytes, the consequence of astrocyte dysfunction on homeostatic functions during aging, and the role of astrocytes in age-related neurodegenerative diseases.