Utilizing an in vitro microglial model to study aging-associated lysosomal profile

Microglia, the resident macrophages of the central nervous system, are involved in many different processes to support its homeostasis. With aging, these cells start to show multiple changes in their morphology and function. Some evidence also points towards lysosomal dysfunction in aged microglia. Senescence, a state of irreversible cell cycle arrest, is suggested to be a potential driver behind aging-related microglial dysfunction. However, most of our current knowledge comes from animal studies, which cannot account for the differences between rodent and human microglia. This creates a strong need for tools that would allow to study microglial aging in human cells. Here, we establish an in vitro model of chemically induced senescence in the immortalized human microglia SV40 (IMhu) cells using a combination of 3 different chemicals. The model recapitulates key senescence- and aging-associated features, including reduced proliferation, increased cell size, reduced Lamin B1 expression, changes in nuclear area and shape as well as disrupted heterochromatin organisation and DNA damage. Furthermore, we observed altered expression of lysosomal genes, indicating underlying functional changes. Further studies assessing lysosomal pH and degradative capability could help us better understand lysosomal dysfunction associated with microglial aging. In the future, this could help us uncover the molecular mechanisms behind lysosomal aging in humans as well as identify and screen new targets to restore its function.