Bone Marrow-Derived Alk1 Mutant Endothelial Cells and Clonally Expanded Somatic Alk1 Mutant Endothelial Cells Contribute to the Development of Brain Arteriovenous Malformations in Mice

AbstractWe have previously demonstrated that deletion of activin receptor-like kinase 1 (Alk1) or endoglin in a fraction of endothelial cells (ECs) induces brain arteriovenous malformations (bAVMs) in adult mice upon angiogenic stimulation. Here, we addressed three related questions: (1) couldAlk1− mutant bone marrow (BM)-derived ECs (BMDECs) cause bAVMs? (2) is Alk1− ECs clonally expended during bAVM development? and (3) is the number of mutant ECs correlates to bAVM severity? For the first question, we transplanted BM fromPdgfbiCreER;Alk12f/2f mice (EC-specific tamoxifen-inducible Cre withAlk1-floxed alleles) into wild-type mice, and then induced bAVMs by intra-brain injection of an adeno-associated viral vector expressing vascular endothelial growth factor and intra-peritoneal injection of tamoxifen. For the second question, clonal expansion was analyzed usingPdgfbiCreER;Alk12f/2f;confetti+/ − mice. For the third question, we titrated tamoxifen to limitAlk1 deletion and compared the severity of bAVM in mice treated with low and high tamoxifen doses. We found that wild-type mice withPdgfbiCreER;Alk12f/2f BM developed bAVMs upon VEGF stimulation andAlk1 gene deletion in BMDECs. We also observed clusters of ECs expressing the same confetti color within bAVMs and significant proliferation of Alk1− ECs at early stage of bAVM development, suggesting that Alk1− ECs clonally expanded by local proliferation. Tamoxifen dose titration revealed a direct correlation between t...

Source: Translational Stroke Research - October 21, 2021 Category: Neurology Source Type: research