Microglia changes in the aging pineal gland: a view from the endolysosomal system.

C.L. FREITES; E.M. MUÑOZ

Congreso; XXXVI Annual Meeting SAN 2021; 2021

Argentine Society for Research in Neurosciences

Microglia are multifunctional immune cells within the brain. In the circadian pineal gland (PG), these phagocytes interact with other cell populations and constituent elements to finely modulate their development and function. As long-lived cells, microglia participate in changes that occur during normal aging, such as alterations in the architecture and functionality of subcellular organelles. We compared the PG of old male Wister rats versus young rats by evaluating the expression pattern of ED1/CD68, using immunofluorescence staining followed by quantitative confocal microscopy. ED1 is a marker for lysosomal and associate compartments. Our results showed that the pineal Iba1+ cell population is composed of different subtypes according to the arrangement and cytoplasmic distribution of ED1, in both 3- and 18-month-old samples. However, our quantitative analysis revealed significant changes in the relative density of each phenotype with respect to age. To evaluate the functionality of the different ED1+ structures, we studied the expression of the lysosomal protease cathepsin D. Immunoreactivity for this enzyme in the aged PG suggests that microglia with ED1+ bodies might retain certain proteolytic capacity. Our results indicate that the pineal microglia themselves undergo many changes across their lifespan, including their phagocytic capacity. Microglia, as a plastic and resilient cell population, may continue to influence PG homeostasis and function even as the PG ages.