Study finds marrow-derived cells increasingly populate human brain microglia with age
Researchers used somatic mutation tracking to show that blood-origin cells infiltrate the brains of older adults, becoming a major component of the microglial population.
A new approach that leverages the unique pattern of somatic mutations in individual cell clones was applied to brain tissue from 20 aged individuals, uncovering a consistent influx of marrow-derived cells into the human brain. Detailed single-cell profiling, supported by mitochondrial DNA variant tracing, demonstrated that these cells adopt microglial characteristics and may constitute a large fraction of the overall microglial community in older adults.
The study further examined population data and found that most types of clonal hematopoiesis correlate with a lower incidence of Alzheimer’s disease, implying a potential protective effect. These results challenge the long-standing view that human microglia are solely embryonic in origin and highlight a dynamic, age-related remodeling of the brain’s immune landscape. The work underscores the importance of peripheral hematopoietic contributions to brain health and opens avenues for therapeutic strategies targeting microglial turnover. The research was published in Nature in 2026.
Why it matters
It reveals that blood-derived cells help renew brain immune cells with age, influencing Alzheimer’s risk.
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