August 21st, 2026
The central nervous system is relatively isolated from the rest of the body; the blood-brain barrier ensures that only certain cells and molecules are permitted to pass between the body and brain. Many cell populations are specific to the brain, and even the immune systems in brain and body are relatively isolated and different from one another. Microglia are innate immune cells of the central nervous system, analogous to macrophages elsewhere in the body. They can destroy pathogens and malfunctioning cells, clear up metabolic waste such as protein aggregates and cell debris, and also participate in the intricate processes of tissue regeneration. Further, microglia assist in the maintenance and function of neural networks in the nervous system.
Unfortunately microglia become ever more inflammatory with age, a maladaptive reaction to internal age-related changes such as mitochondrial dysfunction, combined with interactions between microglia and age-related changes in their environment, such as rising levels of protein aggregates and the inflammatory signals generated by senescent cells. As is a common story in aging, an aspect of cell behavior that is necessary and helpful in youth becomes harmful and maladaptive in old age. In today's open access paper, researchers investigate one of the regulatory signal proteins involved in suppressing microglial inflammatory behavior, and demonstrate that (a) the presence of this signal declines with age, worsening microglial inflammation and (b) introducing more of the signal protein into the aged tissue environment improves microglial function.
