Do my stem cells run out as I get older?

Yes, your stem cells do run out as you age. They decline both in number and in function. This is considered one of the core processes driving physical ageing.

It plays out across multiple tissues at the same time. In the brain, the production of new nerve cells decreases, which is linked to cognitive decline and a greater risk of neurodegenerative diseases. In muscles, the stem cells that govern muscle repair become depleted: there are fewer of them and they work less effectively. In hair follicles, the activity of the associated stem cells falls, contributing to age-related hair loss.

The powerhouses of your cells (mitochondria) also play a role. Reduced function of these organelles is associated with both ageing and declining stem cell activity. Whether that is cause or consequence is not yet fully understood. What is clear is that stem cell exhaustion contributes to age-related frailty, as the body gradually loses physiological reserve.

Research into reversing this process is ongoing, but still in its early stages. In old monkeys, infusions of ageing-resistant human stem cells led to fewer signs of ageing, better brain structure and less inflammation, without side effects over 44 weeks. In mice, age-related decline of immune stem cells was temporarily restored through a therapy delivered in the liver. These are animal experiments that cannot simply be translated to humans.

Early studies in people with age-related frailty suggest that stem cell transplantation appears to be safe, but evidence for genuine effectiveness is still lacking. In addition, stem cell transplantations carry a risk of tumour formation. For healthy people, there is currently no proven, safe therapy that counteracts stem cell exhaustion.