Kathryn Strange PhD Student in the Translational Immunotherapy Research team working in the ANRI laboratory

Could there be a link between Alzheimer’s disease and stem cell transplants?

June 14, 2024

You may have seen some stories in the news recently that suggest a stem cell transplant could either help treat, or even transmit, Alzheimer’s disease.

We take a look at the research to understand more.

Alzheimer’s is a type of dementia that affects memory, thinking and behaviour. The disease is thought to be caused by a build-up of proteins in the brain which cause damage over time. 

It’s thought Alzheimer’s is mostly seen in older people because our immune system gets less good at defending and mending the body from damage as we age. 

Because Alzheimer’s is known to be so closely linked with our immune system, some researchers believe blood stem cells (the cells that create our immune system) could be the key to treating it. 

Could we 'reverse' Alzheimer's with young stem cells?

In one study, researchers tested injecting blood stem cells from young mice into older mice with Alzheimer’s disease. They found this helped boost the immune systems of the older mice, reduced the amount of protein build-up in the brain, and improved some brain function and behaviour.

But we’re a long way off from this becoming a potential treatment, as Dr Robert Danby, Chief Medical and Scientific Officer at Anthony Nolan, explained:

While studies like this are very interesting and help our understanding of Alzheimer’s, there are major differences in the physiology and anatomy of mice which mean this early-stage research can’t necessarily be directly applied to humans.

What's more, attempting to understand the impact of this work on humans would be ethically challenging. Although allogenic stem cell transplants are life-saving for patients with serious blood and bone marrow disorders, they still carry significant risk, especially in older patients with other health conditions. At this stage of our understanding, any potential benefit of a stem cell transplant Alzheimer's is likely to be outweighed by the risks involved.

Right now, most progress has been made in treatments that focus on clearing the Alzheimer’s-causing proteins from the brain, which can help slow the disease. But Alzheimer’s disease remains a major priority for global biomedical research, and there are many potential new treatments currently being investigated.

Could Alzheimer’s screening be introduced into transplant guidelines? Probably not

On the flip side of this research, some scientists are investigating whether there's Alzheimer’s could be inadvertently passed on to patients who are undergoing a stem cell transplant for another disease.

In this theory, researchers think the proteins that build up in the brain in Alzheimer’s could be transmitted via the stem cells of a donor who already has the disease. This could go on trigger a protein build up in the recipient’s brain.

To reduce the risk of this, the researchers have said potential stem cell donors should be screened for Alzheimer’s genes before donating.

However, many experts have questioned this. Not least because the only research to support this theory has been conducted in mice.

Dr Danby told us:

A stem cell transplant is a potentially curative treatment for patients who have very few options. There are many factors to consider when choosing an ideal donor and it can be very hard to find some one a match. It's also important we do this as quickly as possible.

Introducing any additional screening without very careful consideration of the implications for patient and donor safety could have unintended consequences, causing delays to patient care or even mean they are unable to find a suitable donor. In most cases, the impact of this would be much worse than any small potential risk Alzheimer’s disease.

Safety is a fundamental principle of stem cell transplant, with extensive national and international guidelines on patient and donor testing. At Anthony Nolan, we’re actively driving research and shaping guidelines to make sure the treatment is as safe and effective as possible.

Learn more about the work we’re doing to help make sure more people survive and thrive after a stem cell transplant.