A group of stem cells residing in the outer blood vessel appear to be involved in the brain’s reaction to stroke. These stem cell have the capacity to create news cells and were discovered two years ago by a research team at Sweden’s Lund University.
The same scientists have now said that the cells, known as pericytes, break away from the blood vessel, proliferate and migrate to damaged brain areas post a stroke. Here they are converted into inflammatory cells, known as microglia.
Pericytes are instrumental for tissue repair in many organs. The researchers believe that their healing properties apply also to the brain. For the first time “we have a study showing time that pericytes are directly involved in the brain’s reaction to stroke,” say the scientists.
“The finding that pericytes can be turned into microglia and these have an important function after a stroke was unexpected. It is also promising as it opens a new possibility to influence inflammation associated with a stroke,” said Gesine Paul-Visse, neurologist at Lund University and senior author of the study.
The scientists used a green fluorescent protein bound to the pericytes to track the cells’ path to the area of damage in the brain. They found that the cells migrate within a week of a stroke and once they reach their destination they turn into microglia cells, the ‘cleaners’ of the central nervous system. The effect of inflammation on the damaged tissue can be either positive (that is reparative) or negative. Scientists are still trying to affirm the exact role of the microglia cells in the regeneration after a stroke. “But we do know that pericytes play an important role in protecting the brain against disease and injury,” they say.
“We now need to define the effect of pericytes on the brain’s recovery after a stroke. With pericytes becoming the target for future research on brain repair, we are on the way to better understanding of the brain’s own defence and repair mechanisms.”
Since current stroke treatments using thrombolysis are limited to the first hours following a stroke there is pressing need for new drugs that can work in the long run. “We hope that targeting pericytes within a longer time window following the onset of stroke, may influence the outcome”, said Gesine Paul-Visse.