Intra-hematomal White Matter Tracts Act As a Scaffold for Macrophage Infiltration After Intracerebral Hemorrhage

Abstract

Intracerebral hemorrhage (ICH) is a stroke subtype with high mortality and severe morbidity. Hemorrhages frequently develop within the white matter, but whether white matter fibers within the hematoma survive after ICH has not been well studied. The current study examines whether white matter fibers persist in the hematoma after ICH, fibers that might be impacted by evacuation, and their relationship to macrophage infiltration in a porcine model. Male piglets had 2.5 ml blood with or without CD47 blocking antibody injected into the right frontal lobe. Brains were harvested from 3 days to 2 months after ICH for brain histology. White matter fibers were detected within the hematoma 3 and 7 days after hemorrhage by brain histology and myelin basic protein immunohistochemistry. White matter still remained in the hematoma cavity at 2 months after ICH. Macrophage scavenger receptor-1 positive macrophages/microglia and heme oxygenase-1 positive cells infiltrated into the hematoma along the intra-hematomal white matter fibers at 3 and 7 days after ICH. Treatment with CD47 blocking antibody enhanced the infiltration of these cells. In conclusion, white matter fibers exist within the hematoma after ICH and macrophages/microglia may use such fibers as a scaffold to infiltrate into the hematoma and aid in hematoma clearance.

Keywords: Intracerebral hemorrhage; Microglia/macrophages; Phagocytosis; White matter.

Conflict of interest statement

Conflict of interest: Jingyin Chen, Sravanthi Koduri, Shuhui Dai, Yasunori Toyota, Ya Hua, Neeraj Chaudhary, Aditya S. Pandey, Richard F. Keep, and Guohua Xi declare that they have no conflict of interest.

© 2020. Springer Science+Business Media, LLC, part of Springer Nature.

Figures

Figure 1.

White matter survival in the hematoma. A) Coronal sections of perfused piglet brain showing hematomas with white matter inside (arrows) at 3 and 7 days. Scale intervals in (A) = 1 mm. B) H&E staining of white matter fibers (arrows) inside the hematoma at 3 and 7 days after ICH. Scale bar in the contralateral and the ipsilateral hemisphere = 1 mm; Scale bar in the hematoma = 50 μm.

Figure 2.

White matter survival in the hematoma cavity 2 months after ICH. A) A brain section showing hematoma cavity formation in the brain. B, C) H&E staining showing hemosiderin deposition and white matter in the cavity. Arrows indicate survived white matter. Scale intervals in (A) = 1mm, scale bar (B) = 100 μm, scale bar in (C) = 20 μm.

Figure 3.

MBP staining of white matter fibers inside the hematoma at days 3 and 7 after ICH. The asterisk indicates the hematoma. Scale bar in the contralateral and the ipsilateral hemisphere = 1 mm; Scale bar in the hematoma = 50 μm.

Figure 4.

HO-1 (A) and MSR1 (B) immunoreactivity and numbers of positive cells in the hematoma in areas without (w/o) white matter fibers vs. with white matter fibers (with) at 3 and 7 days after ICH. Values are mean ± SD, n=4, *p

Figure 5.

HO-1 immunoreactivity and numbers of positive cells in the hematoma in areas without (w/o) white matter fibers vs. with white matter fibers (with) at 3 and 7 days after ICH in animals treated with CD47 blocking antibody. Values are mean ± SD, n=6, #p<0.01 vs. w/o white matter fibers. Scale bar=20 μm.

Figure 6.

Numbers of HO-1 positive cells in the hematoma in areas with white matter fibers at 3 days (A) and 7 days (B) in pigs with ICH or ICH + CD47 blocking antibody (ICH+CD47Ab). Values are mean ± SD, n=4 in ICH and n=6 in ICH+CD47 blocking antibody, *p<0.05, #p<0.01 vs. ICH.