# Single-cell transcriptomic analyses reveal angiogenic vascular responses to chronic cerebral hypoperfusion

## TL;DR

This study uses single-cell RNA sequencing to identify a new type of endothelial cell in the brain that responds to reduced blood flow and may help in developing treatments for vascular dementia.

## Contribution

The discovery of a unique endothelial tip cell type and the role of apelin signaling in angiogenesis after chronic cerebral hypoperfusion.

## Key findings

- A unique endothelial tip cell type was identified and linked to angiogenesis through Apln/Aplnr signaling.
- Apln13 treatment improved angiogenesis, white matter integrity, and cognitive function in mice with chronic hypoperfusion.
- Astrocyte-tip cell communication via Vegfa-Vegfr interactions was highlighted as a key mechanism.

## Abstract

Elucidating the mechanisms underlying vascular injury and repair may guide development of therapies against vascular cognitive impairment and dementia (VD). We employed single-cell RNA sequencing to map cell populations and explore vascular responses in mouse brains collected 42 days after asymmetric common carotid artery stenosis (ACAS)-induced chronic cerebral hypoperfusion. A unique tip cell type was identified among endothelial cell (EC) clusters and validated by immunostaining. Gene Ontology analyses suggested tip cell enrichment in angiogenesis and the involvement of Apln/Aplnr signaling. Immunoblotting confirmed an increase in apelin (Apln) protein after ACAS. In EC cultures, [Pyr1]-Apelin-13 (Apln13), a selective endogenous apelin receptor agonist, enhanced EC proliferation, migration, and tube formation. Treatment with Apln13 also improved angiogenesis, white matter integrity, and cognitive functions in ACAS mice. Cell-cell interaction analyses highlighted astrocyte-tip cell crosstalk via Vegfa-Vegfr interactions.

•An endothelial tip cell subset appears in brain after chronic cerebral hypoperfusion•Apelin/Aplnr signaling is enriched in tip cells and is associated with angiogenesis•Apelin-13 improves angiogenesis and cognitive function after chronic hypoperfusion•Apelin-13 enhances endothelial cell proliferation, migration, and tube formation

An endothelial tip cell subset appears in brain after chronic cerebral hypoperfusion

Apelin/Aplnr signaling is enriched in tip cells and is associated with angiogenesis

Apelin-13 improves angiogenesis and cognitive function after chronic hypoperfusion

Apelin-13 enhances endothelial cell proliferation, migration, and tube formation

Integrative aspects of cell biology; Transcriptomics; Vascular remodeling