Abstract 63: Mutation of Platelet-Derived Growth Factor Receptor B Causes Cerebrovascular Malformation and Enhances Brain Arteriovenous Malformation Severity in Mice

Background and Purpose: Deletion of Endoglin (Eng), an arteriovenous malformation (AVM) causative gene causes AVM in the brain angiogenic region. Reduction of pericytes is correlate with brain AVM hemorrhage. The platelet-derived growth factor B and its receptor β (PDGF-B/PDGFRβ) play important roles in regulating pericyte recruitment during angiogenesis. We hypothesize that mutation of PDGFRβ causes cerebrovascular malformation and enhances bAVM severity in Eng mutant mice. Methods: Three mouse models were used: (1) Pdgfrβ F7 (F7) mice that have mutations disrupting Pdgfrβ signaling, (2) Pdgfb -icreER; Eng f /f mice that have Pdgfb promoter driving, tamoxifen (TM) inducible cre expression in ECs and an floxed Eng gene; and (3) Pdgfb -icreER; Eng f /f ;F7 +/- mice. Brain angiogenesis was induced by intra-brain injection of an adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF). Brain AVMs were induced in Pdgfb -icreER; Eng f /f and Pdgfb -icreER; Eng f /f ;F7 mice by TM induced EC Eng deletion and intra-brain AAV-VEGF injection. Brain AVM phenotypes were analyzed 8-weeks after model induction by latex vascular cast to detect arteriovenous shunts and macroscopic level of AVMs, immunostaining and Prussian blue staining to quantify dysplasia vessels and hemorrhage. Results: Compared to WT mice, F7 +/- and F7 +/+ mice have more dysplastic vessels and fewer vascular pericyte before and after AAV-VEGF injection. F7 +/- and F7 +/+ mice showed hemorrhage on the AAV-VEGF injection sites and AVM like vessels (a few arteriovenous shunts) in 16% F7 +/- and 66% of F7 +/+ mice. Pdgfb -icreER; Eng f /f mice showed dysplastic vessels and hemorrhage at AAV-VEGF injection sites. Compared to Pdgfb -icreER; Eng f /f mice, Pdgfb -icreER; Eng f /f ;F7 +/- had a higher penetrance of bAVM (71% vs 50%) and more dysplastic vessels. Conclusion: F7 mutation cause AVM like structure in mouse brain and exacerbates bAVM phenotype in Eng mutant mice.