Alternatively activated brain-infiltrating macrophages facilitate recovery from collagenase-induced intracerebral hemorrhage

• Published in: Molecular brain 2016-04, Vol.9 (42), p.42-42, Article 42
• Main Authors: Min, Hyunjung, Jang, Yong Ho, Cho, Ik-Hyun, Yu, Seong-Woon, Lee, Sung Joong
• Format: Article
• Language: English
• Subjects: Analysis; Animals; Blood-brain barrier; Bone Marrow Cells - pathology; Brain - pathology; Care and treatment; Cell Polarity; Cerebral Hemorrhage - chemically induced; Cerebral Hemorrhage - pathology; Collagenases; Complications and side effects; Disability; Health aspects; Hematoma - pathology; Intracerebral hemorrhage; Macrophage Activation; Macrophages; Macrophages - metabolism; Mice, Inbred C57BL; Monocytes - pathology; Neuroglia - metabolism; Phenotype; Risk factors; Solubility
• ISSN: 1756-6606; 1756-6606
• DOI: 10.1186/s13041-016-0225-3

Intracerebral hemorrhage (ICH) is one of the major causes of stroke. After onset of ICH, massive infiltration of macrophages is detected in the peri-hematoma regions. Still, the function of these macrophages in ICH has not been completely elucidated. In a collagenase-induced ICH model, CX3CR1(+) macrophages accumulated in the peri-hematoma region. Characterization of these macrophages revealed expression of alternatively activated (M2) macrophage markers. In the macrophage-depleted mice, ICH-induced brain lesion volume was larger and neurological deficits were more severe compared to those of control mice, indicating a protective role of these macrophages in ICH. In the ICH-injured brain, mannose receptor-expressing macrophages increased at a delayed time point after ICH, indicating M2 polarization of the brain-infiltrating macrophages in the brain microenvironment. To explore this possibility, bone marrow-derived macrophages (BMDM) were co-cultured with mouse brain glial cells and then tested for activation phenotype. Upon co-culture with glia, the number of mannose receptor-positive M2 macrophages was significantly increased. Furthermore, treatment with glia-conditioned media increased the number of BMDM of M2 phenotype. In this study, our data suggest that brain-infiltrating macrophages after ICH are polarized to the M2 phenotype by brain glial cells and thereby contribute to recovery from ICH injury.