Inflammation changes brain stem cells

The key focus of the study was neurogenesis in the hippocampus, which is the formation of new neurons in this area of the brain. The hippocampus is one of the few areas of the adult human brain where neural cell generation continues; it is important for learning, memory, and mood regulation. Decreased neurogenesis has been linked to age-related changes, neurodegeneration, and mood disorders.

The researchers focused on the role of cytokines, which are signaling molecules that the body releases in response to threats (such as viral infections) and trigger an immune response. Elevated cytokine levels are characteristic of chronic inflammation. In the experiment, the researchers added one of the key cytokines, tumor necrosis factor alpha (TNF—alpha), to human hippocampal stem cells.

TNF‑α not only slows down the transformation of stem cells into neurons, it switches them into an immune response mode. In this state, the cells stop forming new nerve cells and instead begin to release signals that attract T‑lymphocytes, which support the inflammatory process. According to experts, it was particularly unexpected that stem cells are actively involved in maintaining the immune response in the brain.

An important additional discovery concerns the signaling pathway involving type I interferons, molecules commonly associated with the body’s antiviral defense. The researchers showed that blocking this pathway using an existing therapeutic antibody partially restores the ability of stem cells to form new neurons and reduces the recruitment of pro-inflammatory T cells.

According to the study’s co-authors, the discovered mechanism explains why prolonged inflammation is particularly harmful to brain health. Additionally, it points to potential therapeutic strategies, as protecting or restoring the hippocampus’s regenerative potential could be a new avenue for preventing and treating conditions associated with cognitive decline.