Abstract 4951: A Genetic Model of Vascular Inflammation: Switchable Expression of Hypoxia Inducible Factor1 Alpha (HIF1a) Produces Multistage Targetable Endothelial Activation

Abstract

Angiogenesis is a linchpin of survival and tissue restoration following ischemia, but also a prerequisite for atherosclerosis. Angiogenesis is induced by a complex interplay of tissue hypoxia, acidosis, and inflammation; conditions coordinated by a myriad of molecular regulators. We have created a switchable transgenic model of microvascular network elaboration allowing day-to-day kinetic analysis. Doxycycline induction of a Tet-regulated constitutively active hypoxia-inducible factor-1a mutant transgene, HIF-1a ^Pro402/564A/Asn803A was targeted to the skin (TetOn-HIF-1a mice). These mice first demonstrate microvascular dilatation on Dox d1, a burst of endothelial proliferation on d3, followed by an exponential decline by d14 –28. Plasma levels of the bone marrow mobilization factors VEGF, PlGF, and SDF1 spike on d3, while tissue levels of these recruitment and retention factors peak at d14. HIF-1 conditioned stroma and activated endothelium recruit large numbers of bone marrow-derived cells of multiple monocytic lineages. There is a striking, day/stage specific decoration of TetOn-HIF-1a microvessels by targeted nanoparticles. AlphaVbeta3 integrin-targeted nanoparticle binding is evident on d3, but absent by d14. VCAM-1-targeted nanoparticles display similar kinetics peaking on d3 (see Figure ); falling to background levels by d14. Thus, a monogenetic perturbation of a master regulatory transcription factor recapitulates the complex multitissue compartmental contributions to ischemic angiogenesis, providing a platform for functional investigation of the biology and therapeutic efficacy of inflammation with vascular-targeted nanoparticles. Figure 1. Decoration of the d3 TetOn-HIF- 1a microvasculature by Alexa Fluor 594 loaded, VCAM targeted, PFOB nanoparticles.