J. Clin. Invest. https://doi.org/10.1172/JCI90647 (2017)

Cranial irradiation as practised in cancer therapy is often associated with damage to the brain and results in neurological impairment. In the Journal of Clinical Investigation, Scadden and colleagues demonstrate that bone marrow–derived monocytes-macrophages are important for repairing such irradiation-induced brain injury. Using a mouse model of irradiation injury, the authors observe that these cells migrate to and are retained long term in the brain parenchyma. When mice are treated with the myeloid cell–stimulatory cytokine G-CSF, brain repair is improved in a manner dependent on bone marrow monocytes-macrophages. Cognitive function is similarly improved after treatment with G-CSF. This study demonstrates an unexpected connection between bone marrow–derived monocytes-macrophages and brain repair.