Stroke: Macrophages migrate from the blood
Microglia in the brain do not light up
"The trick with our model is that this feature is transferred to the daughter cells circulating in the blood, whereas resident microglia in the brain are not marked," explains pharmacologist Stumm. Immigrated immune cells can therefore be easily distinguished from microglia by their color. The researchers were able to show that during a healthy mouse life, virtually no macrophages generated by bone marrow stem cells settle in the brain. This complements earlier findings by professors Geissmann and Mass that macrophages located in tissues develop very early during embryonic development, colonize the entire embryo and from then on maintain themselves through cell division.
With the help of their model study on mice, the researchers have now discovered that shortly after a stroke, numerous macrophages that had migrated from the blood begin to attack dead and adjacent healthy brain tissue. Contrary to previous assumptions, the outsiders withdrew completely from the healthy brain tissue in the following days and were then only found in the dead brain tissue.
Researchers inactivated the Cxcr4 gene function
In a next step, the researchers inactivated the Cxcr4 gene function, leaving intact the molecular switch that helps them detect the immigrated immune cells. "We were interested in Cxcr4 because this protein acts like an antenna, i.e. as a receptor, for a messenger substance that is believed to be involved in inflammatory processes in the brain," says Prof. Stumm. The researchers found that a stroke initially attracted fewer macrophages into the brain when the Cxcr4 function was missing. In the following days, the macrophages that had migrated into the brain migrated only incompletely into the dead brain tissue. Some remained in healthy brain tissue for far too long and prevented the resident microglia from settling down.标签：