Researchers studying a type of cell found in the trillions in our
brain have made an important discovery as to how it responds to brain
injury and disease such as stroke. A University of Bristol team has
identified proteins which trigger the processes that underlie how
astrocyte cells respond to neurological trauma.
The star-shaped astrocytes, which outnumber neurons in humans,
are a type of glial cell that comprise one of two main categories of
cell found in the brain along with neurons. The cells, which have
branched extensions that reach synapses (the connections between
neurons) blood vessels, and neighbouring astrocytes, play a pivotal role
in almost all aspects of brain function by supplying physical and
nutritional support for neurons. They also contribute to the
communication between neurons and the response to injury.
However, the cells are also known to trigger both beneficial and
detrimental effects in response to neurological trauma. When the brain
is subjected to injury or disease, the cells react in a number of ways,
including a change in shape. In severe cases, the altered cells form a
scar, which is thought to have beneficial, as well as detrimental
effects by allowing prompt repair of the blood-brain barrier, and
limiting cell death, but also impairing the regeneration of nerve fibres
and the effective incorporation of neuronal grafts - where additional
neuronal cells are added to the injured site.
The cells change shape via the regulation of a structural component
of the cell called the actin cytoskeleton, which is made up of
filaments that shrink and grow to physically manoeuvre parts of the
cell. In the lab, the team cultured astrocytes in a dish and were able
to make them change shape by chemically or genetically manipulating
proteins that control actin, and also by mimicking the environment that
the cells would be exposed to during a stroke.
By doing so the team found that very dramatic changes in cell shape
were caused by controlling the actin cytoskeleton in the in vitro
stroke model. The team also identified additional protein molecules
that control this process, suggesting that a complex mechanism is
Dr Jonathan Hanley from the University's School of Biochemistry
said: "Our findings are crucial to our understanding of how the brain
responds to many disorders that affect millions of people every year.
Until now, the details of the actin-based mechanisms that control
astrocyte morphology were unknown, so we anticipate that our work will
lead to future discoveries about this important process."