An Alzheimer’s protein found in contaminated vials of human growth hormone can spread in the brains of mice. That finding, published online December 13 in Nature, adds heft to the idea that, in very rare cases, amyloid-beta can travel from one person’s brain to another’s.
Decades ago, over a thousand young people in the United Kingdom received injections of growth hormone derived from cadavers’ brains as treatment for growth deficiencies. Four of these people died with unusually high levels of A-beta in their brains, a sign of Alzheimer’s disease (SN: 10/17/15, p. 12). The results hinted that A-beta may have been delivered along with the growth hormone.
Now researchers have confirmed not only that A-beta was in some of those old vials, but also that it can spark A-beta accumulation in mice’s brains. Neurologist John Collinge of University College London and colleagues found that brain injections of the contaminated growth hormone led to clumps of A-beta in the brains of mice genetically engineered to produce the protein, while brain injections with synthetic growth hormone did not.
Amyloid-beta (brown) accumulated inside brain blood vessels (No. 1) and formed plaques in the cerebellum (No. 2) in the brains of mice injected with growth hormone that came from cadavers.
The results suggest that A-beta can “seed” the protein in people’s brains, under the right circumstances. Still, that doesn’t mean that Alzheimer’s disease is transmissible in day-to-day life.
“There is no evidence that Alzheimer’s disease is contagious,” says neurologist and neuroscientist David Holtzman of Washington University in St. Louis, who cowrote an accompanying editorial in Nature. The four people who showed signs of A-beta accumulation “were injected repeatedly either in the muscle or intravenously with material that came from human brains,” he says. “This is not a practice done anymore.”