In a mouse model for stroke, substituting the blood with whole blood obtained from a healthy donor mouse reduces stroke symptoms, reveals a paper published in Nature Communications this week. The discovery could potentially lead to the development of a treatment for stroke.
Stroke can cause a breakdown of the blood–brain barrier and can also cause a systemic reaction outside the brain. Xuefang Ren and colleagues show in a series of experiments involving a total of 333 male mice that blood replacement therapy reduces this systemic reaction. They demonstrate that this outcome may be caused by reducing levels of a protein called matrix metalloproteinase-9 (MMP-9) through blood replacement.
The levels of MMP-9 in the blood are known to be increased in mice (and humans) in the first few hours after a stroke occurs. By performing blood replacement therapy in mice approximately 6½ to 7 hours following a stroke, the authors found that volume of the infarct (the area of dead tissue in the brain resulting from a lack of blood supply) was reduced and they observed improved neurological deficits. They also found less MMP-9 and fewer proteins and immune cells related to inflammation in the mice’s blood following blood replacement. When the authors artificially added MMP-9 to the blood from healthy donor mice before the transfusion to mice with stroke, the blood replacement did not improve stroke symptoms.
Together, these findings suggest that blood replacement reduces the level of inflammation by reducing MMP-9 levels in the blood and brain of mice after a stroke.
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