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April 4, 2019
A new study pushes the pendulum on this unsettled question back to yes, asserting that neurons regenerate in the hippocampus well into old age.
“By combining human brain samples obtained under tightly controlled conditions and state-of-the-art tissue processing methods, we identified thousands of immature neurons in the [dentate gyrus, part of the hippocampus] of neurologically healthy human subjects up to the ninth decade of life,” the authors wrote in Nature Medicine. In Alzheimer’s patients, however, “the number and maturation of these neurons progressively declined as AD advanced.”
Adult hippocampal neurogenesis is an accepted phenomenon in other mammals, including mice, in which neurogenesis can apparently be stimulated though exercise.
Preservation of tissue pivotal
The newest study suggests that prior failures to detect neurogenesis evidence in human brains may be related to the preservation of tissue samples prior to research use. Wrote Scientific American:
Brain tissue has to be preserved within a few hours after death, and specific chemicals used to preserve the tissue, or the proteins that identify newly developing cells will be destroyed, said Maria Llorens-Martin, the paper’s senior author. Other researchers have missed the presence of these cells, because their brain tissue was not as precisely preserved, says Llorens-Martin, a neuroscientist at the Autonomous University of Madrid in Spain.
Some debate about adult hippocampal neurogenesis in humans remains, however. A paper published last year in Nature concluded that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans: “I don’t think this at all settles things out,” senior author Arturo Alvarez-Buylla, a professor of neurological surgery at the University of California, San Francisco, told Scientific American. “I’ve been studying adult neurogenesis all my life. I wish I could find a place [in humans] where it does happen convincingly.”
More research needed
The hippocampus plays a role in learning, memory and mood, and the prospect of neurogenesis in humans has implications for Alzheimer’s, depression, PTSD, epilepsy and more, according to Scientific American. Whether or not the adult hippocampal neurogenesis question is now settled, there’s a lot more work to be done to address these conditions.
Brain tissue from normal healthy patients and those with specific diagnoses is among the many human biospecimens available to authorized researchers through the iSpecimen Marketplace. Researchers can search the marketplace for tissue, biofluids and cells by myriad attributes, including diagnosis, patient demographics, medications, and past procedures.
Let’s connect researchers with the specimens they need and swing the pendulum toward progress.
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