How monocytes help brain repair the damage

Washington D.C : Turns out, treating strokes by reducing inflammation in the brain may actually be bad as a recent study has revealed that it can actually help the brain to self-repair.

"This is in total contrast to our previous beliefs," says Professor Zaal Kokaia from Lund University in Sweden.

Kokaia, together with Professor of Neurology Olle Lindvall and colleagues at the Weizmann Institute in Israel, is responsible for these findings. Hopefully, these new data will lead to new ways of treating stroke in the future.

When stroke occurs, the nerve cells in the damaged area of the brain die, causing an inflammation that attracts cells from the immune system. Among them is monocytes, a type of white blood cells produced in the bone marrow.

The monocytes travel to the inflamed area, and here they develop into macrophages that clear out any dead tissue. But this is not all that they do: they also secrete substances that help the brain repair the damage.

Most stroke patients recover at least partly over time. This spontaneous improvement is well known, but not its exact cause. The Lund researchers now believe that the improvement is partly due to the substances released by the immune cells.

In their study, they actually performed the opposite: in animal model of stroke they were able to ablate monocytes from the blood. Mice with decreased number of circulating monocytes were much less successful in their recovery from stroke than mice whose immune system was functioning as normal.

"Obviously, there is a difference between mice and humans, but there is no indication that our brains function differently in this regard", says Olle Lindvall.

He further argues that this new insight concerning the positive effects of inflammation could also be applied to other diseases.

The study is recently published in the international Journal of Neuroscience.