The Karolinska Institutet team, led by Jonas Frisén, presents direct evidence that new neurons are produced in the human hippocampus into the late 70s. Using single-nucleus RNA sequencing, flow cytometry with machine learning, and spatial tools (RNAscope and Xenium), they identified dividing neural progenitor cells concentrated in the dentate gyrus. The study reveals substantial individual variability, highlights differences versus animal models, and suggests possible relevance for diseases such as Alzheimer’s and depression while calling for further research.
Adults Can Grow New Brain Cells into Their 70s, Study Finds
The Karolinska Institutet team, led by Jonas Frisén, presents direct evidence that new neurons are produced in the human hippocampus into the late 70s. Using single-nucleus RNA sequencing, flow cytometry with machine learning, and spatial tools (RNAscope and Xenium), they identified dividing neural progenitor cells concentrated in the dentate gyrus. The study reveals substantial individual variability, highlights differences versus animal models, and suggests possible relevance for diseases such as Alzheimer’s and depression while calling for further research.
14:20, 03.11.2025Science
New evidence shows adult neurogenesis persists into late adulthood
Summary: A team at Sweden’s Karolinska Institutet, led by Jonas Frisén, reports direct evidence that the adult human hippocampus continues to generate new neurons into the late 70s. Using multiple complementary techniques on brain tissue spanning birth to age 78, the researchers located dividing neural progenitor cells and immature neurons in a discrete region of the hippocampus called the dentate gyrus.
What the researchers did
The team analyzed human hippocampal tissue obtained from several biobanks across different countries. They applied single-nucleus RNA sequencing to profile gene activity in individual nuclei, flow cytometry combined with machine-learning to isolate and detect rare dividing cells, and spatial gene-expression methods (RNAscope and Xenium) to map where these cells reside within tissue sections.
Key findings
The investigators identified definitive neural progenitor cells in adult human hippocampus samples and confirmed these cells were actively dividing using Ki67, a standard proliferation marker. Both progenitor cells and young neurons were concentrated in the dentate gyrus, a hippocampal subregion linked to memory formation, spatial learning and adaptation.
Comparisons with animal data (mice, pigs, monkeys) showed many similarities in progenitor-cell types, though notable differences in gene expression were found. Importantly, the study documented substantial individual variability: some adults had many progenitor cells while others had few or none.
Implications and caveats
The results strengthen the evidence that human neurogenesis can continue through late adulthood and point researchers to a specific anatomical target for future studies and potential therapies. This has implications for conditions that involve the hippocampus—such as Alzheimer’s disease and depression—because stimulating neurogenesis might someday contribute to repair or improved function.
However, the authors emphasize caution: differences in gene expression between humans and animals and the wide individual variability mean that translation to treatments will require many more studies. The presence of progenitor cells does not automatically guarantee functional integration of new neurons or clinical benefit.
Practical takeaways
While mechanistic therapies are still in the future, the study supports the broader concept of lifelong brain plasticity. Lifestyle factors known to support brain health—regular physical exercise, sustained learning, social engagement and cognitive challenges—remain sensible strategies to promote hippocampal function, though direct evidence that these activities increase neurogenesis in humans is still being investigated.
Publication: The study is available online in the journal Science.