UK scientists find link between Alzheimer’s and surgery
Brain abnormalities associated with the disease could be transmitted, research shows
Brain abnormalities associated with Alzheimer’s disease could be transmitted by surgical procedures in exceptional circumstances, UK scientists have found.
The team at University College London said their experiments demonstrated the need for extreme vigilance in sterilising medical instruments, but they emphasised that there was no evidence of potential transmission of Alzheimer’s through blood transfusions or social contact.
The UCL study, published in Nature, examined batches of human growth hormone extracted from the pituitary glands of deceased donors, dating back to the early 1980s, when children of short stature were treated with HGH from cadavers.
Some HGH samples contained substantial amounts of amyloid-beta, the abnormally folded protein that builds up in the brains of Alzheimer’s patients and is believed to contribute to dementia symptoms.
Then the researchers injected the contaminated HGH samples into the brains of mice genetically susceptible to Alzheimer’s disease. Over a period of months this “seeded the development of amyloid-beta pathology” in the animals’ brains, similar to the changes seen in humans in the early stages of Alzheimer’s before symptoms appear.
Although HGH from cadavers has not been used since 1985, the UCL team said the findings “should prompt a review of the risk of transmission of amyloid-beta seeds by medical and surgical procedures” — for example on the instruments used in brain operations. But the scientists added: “There is no suggestion that Alzheimer’s disease is contagious and no supportive evidence from epidemiological studies that it is transmissible . . . by blood transfusion.”
Other Alzheimer’s experts expressed confidence in procedures put in place in the 1980s and 1990s to prevent the transmission of pathogens, particularly the prion proteins that cause Creutzfeldt-Jakob disease (CJD), through potentially infected human tissues or surgical instruments.
“These procedures are still in place and while this publication emphasises their importance, there is little reason to assume more stringent procedures are needed,” said David Brown, professor of biochemistry at the University of Bath.
John Collinge, the project leader, said it followed up a 2015 study that found traces of amyloid-beta in the brains of patients who had died from CJD as a result of treatment with contaminated HGH. “These were young people in their 30s and 40s who would not normally show signs of amyloid pathology,” he said.
The latest study adds evidence that preserved HGH contained amyloid-beta, and that the samples could transmit the protein to susceptible mice.
“I was rather amazed that we could seed the pathology so easily from material that had sat around for 30 or 40 years as a powder at room temperature,” said Professor Collinge. “But it is very important that we don’t scare people into thinking they might ‘catch’ Alzheimer’s disease.”