High-Mobility Group Box-1-Induced Angiogenesis After Indirect Bypass Surgery in a Chronic Cerebral Hypoperfusion Model

Abstract

High-mobility group box-1 (HMGB1) is a nuclear protein that promotes inflammation during the acute phase post-stroke, and enhances angiogenesis during the delayed phase. Here, we evaluated whether indirect revascularization surgery with HMGB1 accelerates brain angiogenesis in a chronic cerebral hypoperfusion model. Seven days after hypoperfusion induction, encephalo-myo-synangiosis (EMS) was performed with or without HMGB1 treatment into the temporal muscle. We detected significant increments in cortical vasculature (p < 0.01), vascular endothelial growth factor (VEGF) expression in the temporal muscle (p < 0.05), and ratio of radiation intensity on the operated side compared with the non-operated side after EMS in the HMGB1-treated group than in the control group (p < 0.01). Altogether, HMGB1 with EMS in a chronic hypoperfusion model promoted brain angiogenesis in a VEGF-dependent manner, resulting in cerebral blood flow improvement. This treatment may be an effective therapy for patients with moyamoya disease.

Keywords: Cerebral hypoperfusion; Encephalo-myo-synangiosis; High-mobility group box-1; Moyamoya disease; Vascular endothelial growth factor.

Fig. 1

Experimental schedule. The rats underwent bilateral common carotid artery (CCAs) occlusion. Seven days after CCA occlusion, encephalo-myo-synangiosis (EMS) with or without HMGB1 administration into the temporal muscle was performed. Immunohistochemical analysis and vascular endothelial growth factor (VEGF) analysis were performed 4 and 14 days after EMS. Cerebral blood flow was assessed 14 days after EMS

Fig. 2

The number of blood vessels in the brain cortex 4 days after EMS. a Representative photomicrographs of the control and HMGB1-treated groups stained with antibody against CD31. b The number of vessels in the brain cortex 4 days after EMS was not statistically different on both sides between the two groups

Fig. 3

Number of blood vessels in the brain cortex 14 days after EMS. a Representative photomicrographs of the control- and HMGB1-treated groups stained with antibody against CD31. b The number of vessels in the brain cortex on the operated side in the HMGB1-treated group was higher than that on the operated side in the control group, and it was significantly higher compared to the non-operated side in the HMGB1-treated group (*p < 0.01)

Fig. 4

Expression of VEGF protein levels in the brain cortex and temporal muscle. a VEGF protein expression in the brain cortex 4 days after EMS was not statistically different on both sides between the two groups. b In the temporal muscle, VEGF expression on the operated side in the HMGB1-treated group was higher than that of the operated side in the control group and was significantly higher compared to the non-operated side in the same group 4 days after EMS (*p < 0.05). c VEGF expression in the brain cortex 14 days after EMS was not statistically different on both sides between the two groups. d In the temporal muscle, VEGF expression on the operated side in both groups was significantly decreased compared to the non-operated side 14 days after EMS (*p < 0.01, **p < 0.01)

Fig. 5

Cerebral blood flow 14 days after EMS. a–c Representative SPECT image obtained 14 days after EMS showing improved cerebral perfusion in both groups (A: control, B: HMGB-1, C: healthy). d The ratio of radiation intensity on the operated side compared to the non-operated side was significantly higher in the HMGB1-treated group than that in the control group (*p < 0.01). The healthy rats show no apparent laterality of cerebral blood flow