Alsereidi, Fatmah R.

Abstract Brain arteriovenous malformations (AVMs) result from abnormal growth of vascular structures. AVMs pose a significant rupture risk, and its treatment is challenging due to the complex hemodynamics within the tangled nidus. Currently, investigating AVM hemodynamics remains a challenge due to the low resolution of clinical imaging modalities. In this study, a high-fidelity Computational Fluid Dynamics (CFD) simulation of a brain AVM from a KRAS-mutated mouse model is developed from micro-CT images. Brain AVMs were induced in mice through systemic delivery of AAV-BR1-CAG vector encoding KRASG12V-GFP transgene to cerebral endothelial cells. High-resolution microCT imaging at 6.551 𝜇𝑚 pixel size captured the complex vascular anatomy. The cerebral arteries were reconstructed using the 3D Slicer and Blender software. The curvilinear immersed boundary (CURVIB) method was employed with approximately 65 million grid points and spatial resolution of 0.7−2.3 𝜇𝑚. Our preliminary results reveal heterogeneous flow distribution through the nidus, with blood channeling through two primary pathways. The extremely low Reynolds number (0.038) indicates viscous-dominated flow characteristic of microcirculation. Our work presents the first high-resolution CFD simulation of brain AVM in the literature, providing a foundation for investigating flow-mediated vascular remodeling, rupture risk assessment, and therapeutic intervention planning in future.

OBJECTIVE Brain arteriovenous malformations (bAVMs) are rare but potentially devastating cerebrovascular lesions. Activating KRAS mutations are common in sporadic bAVMs, but their clinical implications remain unclear. The aim of this study was to investigate a novel therapeutic strategy for hemorrhagic bAVMs based on dual inhibition of the mitogen-activated protein kinase (MAPK) and vascular endothelial growth factor (VEGF) pathways using an engineered mouse model with a titratable KRAS G12V - GFP transgene. METHODS The AAV-BR1-CAG vector was used to deliver a KRAS G12V - GFP transgene specifically to cerebral endothelial cells. Mice received 5 × 10 7 to 5 × 10 10 genome copies of the vector, and bAVM formation, intracerebral hemorrhage (ICH), and overall survival were assessed. Mice with established hemorrhagic bAVMs were subsequently treated with trametinib (MEK inhibitor) or RMC-7977 (RAS inhibitor), with or without an anti–mouse VEGF antibody, starting 4 weeks after viral delivery. Overall survival was assessed. RESULTS Selective overexpression of KRAS G12V - GFP in cerebral endothelial cells led to the formation of bAVMs in a dose-dependent manner. Mice that received the highest transgene dose developed significantly more bAVMs, exhibited a higher ICH burden, and had worse overall survival compared with those that received lower transgene doses. In mice receiving the highest transgene dose, trametinib alone modestly improved the median overall survival (8.4 weeks vs 6.4 weeks, p = 0.049), while single-agent RMC-7977 showed no significant benefit. Anti-VEGF therapy alone reduced survival (6.9 weeks vs 9.6 weeks, p = 0.044). However, combination therapy with trametinib or RMC-7977 and anti-VEGF antibody significantly prolonged survival, with the most pronounced benefit seen in the RMC-7977 plus anti-VEGF group (13.1 weeks vs 6.7 weeks in controls, p = 0.024). CONCLUSIONS Our findings suggest that, in addition to promoting bAVM formation, KRAS mutations in cerebral endothelial cells might be causally implicated in bAVM rupture. Additionally, concomitant inhibition of the MAPK and VEGF pathways could be a promising novel therapeutic strategy for KRAS -mutated bAVMs.