The dynamic transcriptional landscape of intussusceptive angiogenesis

Vascular Endothelial Factor-A (VEGF) is the master regulator of vascular growth
in development and tissue repair and is the key target for therapeutic angiogenesis.
However, its therapeutic modes of action are still elusive. In fact, at therapeutic doses,
VEGF stimulates vascular growth in skeletal muscle through intussusception, also known
as splitting angiogenesis, rather than through the commonly studied process of
sprouting (1). A key feature of intussusception is the formation of endothelial cellular
processes projecting into the vascular lumen, termed intraluminal sprouts. These
projections from opposite sides of the vascular wall fuse to form transluminal pillars,
which then grow in circumference, merge laterally, and eventually divide the affected
vessel into two new ones (2). However, the specific functional cell states that endothelial
cells may adopt in response to VEGF in order to perform intussusceptive remodeling
remain unknown. Therefore, here we set out, for the first time, to capture such dynamic
and transient endothelial cell phenotypes by analyzing the transcriptomic changes
induced by VEGF delivery to skeletal muscle, at single-cell resolution and over time. In
particular we sought to:
1. Identify which endothelial communities are induced by VEGF delivery
2. Investigate the defining biological processes and markers of such communities, and
validate them in vivo
3. Seek intussusceptive-defining processes by comparing the identified functional
states of VEGF-induced intussusception against those of sprouting angiogenesis.