In a study published in Science Translational Medicine, a group of researchers led by scientists from Imperial College London (UK) exhibited tau tangles associated with dementia in patients who have suffered a single head injury.
It has been well known that neurodegeneration and dementia can be caused later in life after repeated head injury – such as those sustained in contact sports such as boxing and American football.
However, this is the first time scientists have observed tau tangles in living patients who have only experienced a single severe head injury.
“Scientists increasingly realize that head injuries have a lasting legacy in the brain – and can continue to cause damage decades after the initial injury. However, up until now most of the research has focused on the people who have sustained multiple head injuries, such as boxers and American football players. This is the first time we have seen in these protein tangles in patients who have sustained a single head injury,” explained study author Nikos Gorgoraptis (Imperial College London).
The team studied 21 patients who had experienced a moderate to severe head injury at least 18 years prior to the study and 11 healthy individuals who had not suffered from a head injury.
In order to measure the amount of tau protein in each of the patients’ brains, the researchers used PET scans along with flortaucipir, which bound to the protein. The results revealed that not only were patients with head injury more likely to have tau tangles, but they also had higher levels of nerve damage. None of the healthy individuals had tau tangles.
After discovering the tau tangles in the patients, the scientists commented that this research may fast-track the development of treatment that breakdown tau tangles and allow doctors to monitor the amount of the protein.
Interestingly, the results revealed that patients with higher amounts of tau tangles did not have any reduction in brain function when compared to patients with few tangles. However, Gorgoraptis added that it can take years after the development of the tangles for symptoms such as memory loss to appear.
“What is exciting about this study is this is the first step towards a scan that can give a clear indication of how much tau is in the brain, and where it is located. As treatments develop over the coming years that might target tau tangles, these scans will help doctors select the patients who may benefit and monitor the effectiveness of these treatments,” concluded Gorgoraptis.
Sources: Gorgoraptis N, Li LM, Whittington A et al. In vivo detection of cerebral tau pathology in long-term survivors of traumatic brain injury. Sci. Transl. Med. doi:10.1126/scitranslmed.aaw1993 (2019) (Epub ahead of print); www.imperial.ac.uk/news/192788/protein-tangles-linked-with-dementia-seen/
What causes tau protein tangles?
Tau proteins normally act as a type of scaffolding to provide structural support to surrounding nerve cells in the brain. However, when these brain cells become damaged (i.e. during a head injury) the protein can form clumps or become tangled. These tangles can block synapses and prevent the distribution of essential nutrients to other cells in the brain causing them to die, which can result in neurodegeneration.
Where are tau proteins found?
Tau protein are mostly found in neurons of the central nervous system but are also expressed at low levels in CNS astrocytes and oligodendrocytes. Tau is mainly active in the distal portion of axons where they stabilize microtubules and provide flexibility as well.