Inflammation halts new brain cell growth in adults

Chronic low-grade inflammation is one of the most consistent features of ageing, in the brain as much as anywhere else. Until now, the precise pathway linking inflammatory signals to reduced neurogenesis (the birth of new neurons) was not well understood. The study, published in Nature Communications, maps part of that chain using human hippocampal stem cells.

TNF-alpha as the trigger

Using single-cell RNA sequencing, the researchers tracked individual cells exposed to TNF-alpha, a key inflammatory protein. TNF-alpha triggered production of type I interferons, molecules normally deployed against viruses. Those interferons then recruited T cells via a receptor called CXCR3. The T cells directly suppressed neurogenesis.

Crucially, the progenitor cells that would normally mature into new neurons switched roles in the inflamed environment. Instead of becoming neurons, they adopted an immune-defensive function. The researchers stress this is a preliminary finding from a laboratory model, and whether the identical mechanism operates in the living human brain remains to be established.

The ageing connection

As we age, chronic inflammation tends to increase while neurogenesis declines. This study suggests these two trends may be mechanistically linked. TNF-alpha is already a target for anti-inflammatory drugs in other diseases. The possibility that blocking it could restore neurogenesis is intriguing from a longevity perspective, though the gap between a lab model and a viable therapy is substantial.

The CXCR3 receptor and the interferon pathway are both pharmacologically accessible in principle. Whether targeting them safely improves brain health in ageing humans is a question that future research will need to answer.

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