Quantitative, structural and molecular changes in neuroglia of aging mammals: A review

Abstract

The neuroglia of the central and peripheral nervous systems undergo numerous changes during normal aging. Astrocytes become hypertrophic and accumulate intermediate filaments. Oligodendrocytes and Schwann cells undergo alterations that are often accompanied by degenerative changes to the myelin sheath. In microglia, proliferation in response to injury, motility of cell processes, ability to migrate to sites of neural injury, and phagocytic and autophagic capabilities are reduced. In sensory ganglia, the number and extent of gaps between perineuronal satellite cells – that leave the surfaces of sensory ganglion neurons directly exposed to basal lamina– increase significantly. The molecular profiles of neuroglia also change in old age, which, in view of the interactions between neurons and neuroglia, have negative consequences for important physiological processes in the nervous system. Since neuroglia actively participate in numerous nervous system processes, it is likely that not only neurons but also neuroglia will prove to be useful targets for interventions to prevent, reverse or slow the behavioral changes and cognitive decline that often accompany senescence.

On the connectivity in the central nervous system and the age-induced changes of its network organization

“…However, subsequent studies (see von Bartheld, 2018; Pannese, 2011 for reviews), exploiting more accurate morphometric methods, have evidenced that during normal aging neuronal loss is limited to restricted regions of the central nervous system and is quite small (probably no more than 10%). Similar concepts apply to astrocytes as well (see Pannese, 2021) and changes with aging in astrocyte number were detected only in specific brain regions. Moreover, the idea of an overabundance of glial cells as compared to neurons also changed with the development of modern counting methods and the concept that glial cells are not more abundant than neurons in human brains is now becoming increasingly accepted in the field (von Bartheld, 2018).…”

“…The most common age-related structural changes undergone by neurons involve a reduction in the complexity of dendrite arborization and dendritic length, and the myelin sheaths of axons may become less compact (Dickstein et al, 2007;Pannese 2011). Concerning glial cells, astrocytes may become hypertrophic and accumulate intermediate filaments, oligodendrocytes and Schwann cells exhibit alterations consistent with the observed changes to the myelin sheaths, while in microglia, proliferation in response to injury, motility of cell processes, ability to migrate and phagocytic capabilities are often reduced (Rodriguez-Arellano et al, 2015;Pannese, 2021). Possible age-related modifications affecting VT processes in the cortex were also investigated (Nicholson, 2005) indicating no significant changes of the extracellular space in terms of volume and tortuosity, suggesting that, at least in the cortex, diffusion properties for small signaling molecules should not change dramatically with age.…”

Senescence in Primary Rat Astrocytes Induces Loss of the Mitochondrial Membrane Potential and Alters Mitochondrial Dynamics in Cortical Neurons

“…Nevertheless, in previous studies, the cells were in direct contact with each other. The improvement observed in Figures 2A,B in the neurons + CA might be due to the contribution of nutrients that this type of glia provides to neurons, which, when senesce, cease to be supplemented as astrocytes become senescent ( Pannese, 2021 ).…”

Event‐Related Spectral Perturbation, Inter Trial Coherence, and Functional Connectivity in motor execution: A comparative EEG study of old and young subjects

“…Cortical volume reduction is the result of shrinkage or loss of large neurons (Haug & Eggers, 1991 ; Terry et al., 1987 ). During normal aging neuroglia cells also undergo numerous changes just as white matter integrity (Bennett & Madden, 2014 ; Pannese, 2021 ).…”