An international team of researchers has found more evidence supporting the idea that the proteins responsible for Alzheimer’s can in some rare cases spread between individuals. Before we go any further – this does not mean that you can contract Alzheimer’s by being in contact with a person with the disease, but it could be “transmitted” in certain medical procedures.
The starting point of this research was a paper published in Nature back in 2015, in which a team looked at eight patients who had developed and died of a degenerative brain disorder known as Creutzfeldt-Jakob disease (CJD). These people had all received growth hormones from deceased individuals (a procedure that was deemed safe until 1985) that were contaminated with prions, infectious misfolded proteins that cause CJD and the so-called Mad Cow Disease.
Researchers showed that these individuals also had deposits of amyloid-beta proteins in their brain. Given that this protein is believed to play a key role in the development of Alzheimer’s, the findings were very important. In the follow-up study, published today in Nature, the team set out to prove a causality between the growth hormone treatment from cadavers and amyloid-beta deposits.
They injected animal models with an amyloid-like protein, similar to those found in the original treatment. The mice developed the deposits in their brains too, showing that the transmission of these proteins can happen.
“Our earlier study found that some individuals who developed CJD many years after treatment as children with cadaver-derived human pituitary growth hormone also had deposits in the brain of a type of aberrant protein characteristic of Alzheimer’s disease,” lead author Professor John Collinge of University College London said in a statement.
“We suggested that the human growth hormone – which prior to 1985 was prepared from human tissue – may have been contaminated with seeds of this material as well as the prions causing CJD.
"Our latest findings now confirm that some archived batches of this hormone did indeed contain seeds of the amyloid beta protein found in Alzheimer’s disease.”
The study raises questions about whether other medical procedures still in use today could be spreading amyloid proteins. The researchers suggest that it is important to review the risks of such protein transmission in neurosurgery, for example. Another study recently suggested that this could indeed happen.
“While we are concerned about what this could mean about how amyloid pathology might be transmitted, we also aim to understand more about the cause and consequences of amyloid beta deposition in the brain and its relationship to tau aggregation, the other hallmark for Alzheimer’s disease,” stated first author Dr Silvia Purro.