THE ARISING · Longevity & Healthspan
Neurons Made From Older Donors' Cells Struggle to Clear Damaged Mitochondria
Neurons need a steady supply of working mitochondria, the parts of a cell that make energy, and a way to remove them when they are damaged. A new laboratory study suggests that in neurons made from older people's cells, the removal process stalls before it finishes.
The work was published in Frontiers in Aging Neuroscience in October 2026 by Emilie Legault, Juan-Pablo Izabal Gamez and Janelle Drouin-Ouellet of the University of Montreal's Faculty of Pharmacy. It is cell-culture research, not a study of living people or intact brains. The team took skin cells from healthy donors aged 11 to 91 and converted them directly into neurons, which the authors call induced neurons.
That method matters. According to the paper, direct reprogramming maintains signatures of cellular aging. Most of what is known about aging neurons comes from animals, which live far shorter lives than people. Human brain tissue studied after death gives only a snapshot in time. Neurons generated from donors of different ages offer a way to study aging in human cells as it unfolds.
The cleanup process in question is called mitophagy. A cell tags a damaged mitochondrion, wraps it in a membrane bubble called an autophagosome, and delivers it to a lysosome, a compartment that breaks it down. The researchers triggered mitophagy and used confocal imaging to see where mitochondria ended up.
In the long, thin extensions of the neurons called neurites, the researchers report signs of mitochondrial impairment in cells from older donors. After mitophagy was induced, mitochondria marked for disposal piled up in autophagosomes and in vesicles carrying a lysosome marker called LAMP1. The end result, in the authors' words, was incomplete elimination of damaged mitochondria.
One finding points to where the problem lies. The activity of the lysosomal enzymes the team measured was preserved. In other words, the cleanup enzymes that were tested still worked. The failure appears to lie in the steps that get damaged mitochondria to those enzymes and through the process.
The authors describe this as the first demonstration of age-related mitophagy impairment in human neurons. They say it also confirms earlier reports of mitochondrial decline in human neurons.
The limits are clear. These are lab-grown neurons from skin cells, not neurons in a working brain. The results show an association between donor age and impaired cleanup, and they do not show what causes it. The study also does not test any treatment.
Why does it matter? Aging is a major risk factor for neurodegenerative diseases such as Parkinson's and Alzheimer's, yet how aging processes inside human neurons lead to disease is still unclear. If the stall is real and is found at a specific step, researchers have a narrower place to look. If follow-up work fails to confirm it, the idea of a specific cleanup failure in aging human neurons would weaken.
The authors say the findings pave the way for more detailed mechanistic studies aimed at finding therapeutic targets. What to watch next: work that identifies which step between tagging and breakdown is failing, and whether the same pattern appears in other human neuron models and in brain tissue.