Alzheimer's traces found seeded in autopsied brains, scientists report
Discovery may offer clues to how degenerative diseases like Alzheimer's occur and are transmitted
An Alzheimer's protein has been found in the brains of people who received injections of human growth hormone in the U.K. decades ago, offering possible clues to how Alzheimer's disease is transmitted
About 15,000 people now living worldwide received such human growth hormone injections.
More than 200 of them developed the brain-wasting illness Creutzfeldt-Jakob disease (CJD) after they were treated with human growth hormone as children, mainly for growth deficiency.
The discovery may offer clues to how degenerative diseases like Alzheimer's occur and how they spread, researchers say.
Before 1985, human growth hormone was made from thousands of human pituitary glands from just outside the brain that were pooled together. Human growth hormone is now made in the lab.
In Wednesday's issue of the journal Nature, researchers report the discovery of Alzheimer's protein in the brains of seven out of eight people they studied who died of CJD from contaminated human growth hormone.
"Unexpectedly, in an autopsy study of eight individuals … aged 35-51 years, in four we found moderate to severe grey matter and vascular amyloid-beta pathology," study author John Collinge of University College London and his co-authors said.
'Very special situation'
Four showed substantial Alzheimer's-like pathology, Collinge told reporters. Only one of the eight was free of any the amyloid-beta protein.
"It's important to understand that this relates to a very special situation where people have been injected with essentially extracts of human tissue. In no way is this suggesting that Alzheimer's disease is in any way a contagious disease," Collinge said.
In mice and monkey models, scientists have taken brain tissue of humans who died of Alzheimer's disease and injected it into the animals, which went on to develop Alzheimer's-like pathology. Collinge believes this is the most likely explanation for the human cases among those injected with human growth hormone.
The researchers believe the batches of human pituitary gland were likely contaminated with the amyloid-beta protein common in the elderly.
Since the study simply describes what happened to these people, it doesn't prove growth hormone injections caused the amyloid protein buildup.
Not regular infection
The subjects also didn't show full-blown Alzheimer's features in the brain, namely the buildup of two "bad" proteins, amyloid and tau, said Dr. Carmela Tartaglia, who studies neurodegenerative diseases at Toronto Western Hospital.
"This is not like a regular infection. This is really we're seeding a part of somebody's brain, and that's going to another person," Tartaglia said.
For this to be transmitted, a fair amount has to be injected into the other person, said Dr. Constantin Polychronakos, a pediatric endocrinologist at Montreal Children's Hospital. He treated children with human-derived growth hormone back in the 1970s and early '80s.
"These new findings are very interesting scientifically because they tell us a little bit about Alzheimer's disease but in terms of saying well could someone treated with growth hormone 30 years ago develop Alzheimer's now, it's possible but extremely unlikely."
For those in the field of neurodegenerative diseases, Collinge said the findings should make those who doubted Alzheimer's could be seeded to take the risk seriously and to research it further.
Currently, low concentrations of beta amyloid seeds can't be detected in the blood or other fluids, which is another avenue to research, Collinge said.
"I think that we're going to have to rethink how we do the screening for probably all organs as well as surgical instruments," Tartaglia said.
Tartaglia said the findings confirm the brain can build up more than one type of abnormal protein and supports the shift in no longer placing CJD in a separate category from other neurodegenerative diseases.