Alzheimer’s is linked to blood transfusions: Scientists discover the protein behind the memory-robbing disorder may have been transmitted in a now-banned procedure
- Hormones that spur growth in short children used to be taken from cadavers
- Banned in 1985 amid fears of the transmission of disease-causing prions
- Tested hormones given to patients who died with signs of Alzheimer’s
- When given to mice, the rodents developed signs of the disease within a year
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Alzheimer’s has been linked to blood transfusions after scientists discovered the memory-robbing disease may have been transferred between patients in a version of the procedure that is now banned.
Hormones that help to spur growth in children who are abnormally short used to be taken from the pituitary glands of cadavers.
This was replaced by synthetic hormones in 1985 after fears were raised about the transmission of misfolded proteins, known as prions, which can cause the fatal brain disorder Creutzfeldt-Jakob disease (CJD).
Scientists tested samples of hormones that were given to patients who later died of CJD with abnormal amyloid protein clumps in their brains – a key sign of Alzheimer’s.
Not only did these samples contain significant levels of amyloids, they also caused the same clumps in mice within a year of them being injected.
Experts worry instruments that are used in brain surgery may spread amyloids. However, others stress experiments have only ever been conducted on mice, with there being no evidence Alzheimer’s can be spread among humans.
Alzheimer’s has been linked to blood transfusions after scientists discovered the disease may have been transferred between patients in a now-banned procedure (stock)
The study, published in Nature, was carried out by University College London and led by Dr John Collinge, a professor of neurology at the UCL Institute of Prion Diseases.
Alzheimer’s is the most common form of dementia and affects more than 520,000 people in the UK, according to the Alzheimer’s Society. The disease has around 5.7million patients in the US, Alzheimer’s Association statistics show.
It occurs when connections between the brain’s billions of nerve cells get lost due to a build-up of amyloid and tau proteins that form abnormal plaques and tangles.
Over time, different areas of the vital organ shrink, with the region responsible for memories usually being affected first. There is no cure with treatments focusing on slowing the disease’s progression and managing symptoms.
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The researchers drew one of their 2015 studies, which analysed the autopsied brains of eight people who died young from CJD.
The disease is thought to occur when high levels of prions – known as ‘amyloid seeds’ – cause irreversible damage to nerve cells. More than 200 people worldwide died of CJD as a result of hormone transfusions.
All of the patients had been treated as children in the 1980s with a human growth hormone taken from cadavers. This procedure was first carried out in the UK in 1958.
Although none of them developed the ‘full picture’ of dementia, six of them had worrying amounts of the naturally-occurring amyloid proteins in their brains.
In an Alzheimer’s patient’s brain, abnormal levels of amyloids clump together to form plaques that collect between nerve cells and disrupt their function.
Six of the brains also had some degree of of cerebral amyloid angiopathy (CAA), which occurs when amyloids build in the brain’s blood vessels and can cause bleeding. CAA is seen to some extent in nearly all Alzheimer’s patients.
To build on this research, the scientists tracked down some of the batches of the human growth hormone that the deceased had been treated with.
Testing these samples revealed that some contained significant levels of both amyloid and tau proteins. Tau has been shown to form tangles in the area of the brain associated with memory loss in Alzheimer’s sufferers.
The samples were then injected into mice who were genetically at-risk of developing the amyloid clumps seen in Alzheimer’s. Other rodents were injected with brain tissue from known dementia patients.
The mice that were injected with the now-banned growth hormones showed clear signs of amyloid clumping along blood vessels in their brains and developed CAA within a year.
This occurred to a greater extent among the rodents who were injected with tissue from Alzheimer’s patients.
The study therefore suggests that human-growth hormone batches that have been stored for decades can still cause worrying amyloid clumps in mice.
‘We have now provided experimental evidence to support our hypothesis that amyloid pathology can be transmitted to people from contaminated materials,’ Professor Collinge said.
‘We cannot yet confirm whether medical or surgical procedures have ever caused Alzheimer’s disease itself in people, or how common it might be to acquire amyloid pathology in this way.’
‘It will be important to review risks of transmission of amyloid pathology by other medical procedures still done today, including instruments used in brain surgery, drawing on other research and what we already know about accidental CJD transmission.’
Dr Rob Buckle, chief science officer at the Medical Research Council, which helped fund the study, stressed that the experiments were carried out on mice that were genetically at-risk of developing amyloid clumps.
Dr Tibor Hortobágyi, a reader in old age psychiatry at King’s College London, argued that normal mice do not have the capacity to develop human-like Alzheimer’s and therefore genetically-modified rodents had to be used.
He did stress, however, that the hormones were injected directly into the animal’s brains, which does not occur in existing medical procedures or the now-banned blood transfusion.
The researchers said the samples were injected into the mice’s brains ‘in order to optimise the chance of detecting seeds in this scarce material’.
Dr Hortobágyi added the study only provides evidence that amyloids can be transferred to mice – not tau or Alzheimer’s disease itself.
‘It is important to stress that there is no indication that Alzheimer’s disease is a contagious disease or is transmissible via blood transfusion,’ he said.
‘This study did not look at surgical instruments at all, so we can’t make any conclusions about that and any suggested implications about that are speculation beyond the scope of this work.’
The Royal College of Surgeons and the Society of British Neurological Surgeons welcomed the study but added more, larger trials are needed.
A spokesperson said: ‘The risks of developing one of these degenerative diseases as a consequence of neurosurgery seems substantially smaller than the everyday risks of the procedures themselves and the diseases they are used to treat’.
Professor Bart De Strooper, director of the UK Dementia Research Institute at UCL, referenced a 2016 Scandinavian study that analysed almost 1.5million people’s health records and found no evidence blood transfusions can cause Alzheimer’s.
Dr James Pickett, head of research at Alzheimer’s Society, concluded: ‘There remains absolutely no evidence that Alzheimer’s disease is contagious.’
WHAT IS ALZHEIMER’S?
Alzheimer’s disease is a progressive, degenerative disease of the brain, in which build-up of abnormal proteins causes nerve cells to die.
This disrupts the transmitters that carry messages, and causes the brain to shrink.
More than 5 million people suffer from the disease in the US, where it is the 6th leading cause of death.
WHAT HAPPENS?
As brain cells die, the functions they provide are lost.
That includes memory, orientation and the ability to think and reason.
The progress of the disease is slow and gradual.
On average, patients live five to seven years after diagnosis, but some may live for ten to 15 years.
EARLY SYMPTOMS:
- Loss of short-term memory
- Disorientation
- Behavioral changes
- Mood swings
- Difficulties dealing with money or making a phone call
LATER SYMPTOMS:
- Severe memory loss, forgetting close family members, familiar objects or places
- Becoming anxious and frustrated over inability to make sense of the world, leading to aggressive behavior
- Eventually lose ability to walk
- May have problems eating
- The majority will eventually need 24-hour care
Source: Alzheimer’s Association
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