Philip Cheng1, Li Ma1,2, Sonali Shaligram1, Espen J Walker1, Shun-Tai Yang1, Chaoliang Tang1, Wan Zhu1, Lei Zhan1, Qiang Li1,3, Xiaonan Zhu1, Michael T Lawton3, Hua Su1. 1. 1Department of Anesthesia and Perioperative Care, Center for Cerebrovascular Research, University of California, San Francisco, California. 2. 2Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China; and. 3. 3Department of Neurological Surgery, University of California, San Francisco, California.
Abstract
OBJECTIVE: A high level of vascular endothelial growth factor (VEGF) has been implicated in brain arteriovenous malformation (bAVM) bleeding and rupture. However, direct evidence is missing. In this study the authors used a mouse bAVM model to test the hypothesis that elevation of focal VEGF levels in bAVMs exacerbates the severity of bAVM hemorrhage. METHODS: Brain AVMs were induced in adult mice in which activin receptor-like kinase 1 (Alk1, a gene that causes AVM) gene exons 4-6 were floxed by intrabasal ganglia injection of an adenoviral vector expressing Cre recombinase to induce Alk1 mutation and an adeno-associated viral vector expressing human VEGF (AAV-VEGF) to induce angiogenesis. Two doses of AAV-VEGF (5 × 109 [high] or 2 × 109 [low]) viral genomes were used. In addition, the common carotid artery and external jugular vein were anastomosed in a group of mice treated with low-dose AAV-VEGF 6 weeks after the model induction to induce cerebral venous hypertension (VH), because VH increases the VEGF level in the brain. Brain samples were collected 8 weeks after the model induction. Hemorrhages in the bAVM lesions were quantified on brain sections stained with Prussian blue, which detects iron deposition. VEGF levels were quantified in bAVM tissue by enzyme-linked immunosorbent assay. RESULTS: Compared to mice injected with a low dose of AAV-VEGF, the mice injected with a high dose had higher levels of VEGF (p = 0.003) and larger Prussian blue-positive areas in the bAVM lesion at 8 or 9 weeks after model induction (p = 0.002). VH increased bAVM hemorrhage in the low-dose AAV-VEGF group. The overall mortality in the high-dose AAV-VEGF group was 26.7%, whereas no mouse died in the low-dose AAV-VEGF group without VH. In contrast, VH caused a mortality of 50% in the low-dose AAV-VEGF group. CONCLUSIONS: Using mouse bAVM models, the authors provided direct evidence that elevation of the VEGF level increases bAVM hemorrhage and mouse mortality.
OBJECTIVE: A high level of vascular endothelial growth factor (VEGF) has been implicated in brain arteriovenous malformation (bAVM) bleeding and rupture. However, direct evidence is missing. In this study the authors used a mousebAVM model to test the hypothesis that elevation of focal VEGF levels in bAVMs exacerbates the severity of bAVM hemorrhage. METHODS:Brain AVMs were induced in adult mice in which activin receptor-like kinase 1 (Alk1, a gene that causes AVM) gene exons 4-6 were floxed by intrabasal ganglia injection of an adenoviral vector expressing Cre recombinase to induce Alk1 mutation and an adeno-associated viral vector expressing humanVEGF (AAV-VEGF) to induce angiogenesis. Two doses of AAV-VEGF (5 × 109 [high] or 2 × 109 [low]) viral genomes were used. In addition, the common carotid artery and external jugular vein were anastomosed in a group of mice treated with low-dose AAV-VEGF 6 weeks after the model induction to induce cerebral venous hypertension (VH), because VH increases the VEGF level in the brain. Brain samples were collected 8 weeks after the model induction. Hemorrhages in the bAVM lesions were quantified on brain sections stained with Prussian blue, which detects iron deposition. VEGF levels were quantified in bAVM tissue by enzyme-linked immunosorbent assay. RESULTS: Compared to mice injected with a low dose of AAV-VEGF, the mice injected with a high dose had higher levels of VEGF (p = 0.003) and larger Prussian blue-positive areas in the bAVM lesion at 8 or 9 weeks after model induction (p = 0.002). VH increased bAVM hemorrhage in the low-dose AAV-VEGF group. The overall mortality in the high-dose AAV-VEGF group was 26.7%, whereas no mouse died in the low-dose AAV-VEGF group without VH. In contrast, VH caused a mortality of 50% in the low-dose AAV-VEGF group. CONCLUSIONS: Using mousebAVM models, the authors provided direct evidence that elevation of the VEGF level increases bAVM hemorrhage and mousemortality.