# Developmental Heterogeneity of Pulmonary Endothelial Phenotype at Single Cell Resolution

> **NIH NIH R01** · STANFORD UNIVERSITY · 2022 · $729,827

## Abstract

Postnatal lung growth during alveolarization markedly increases gas exchange surface area. Rapid
growth of the pulmonary vasculature during early alveolarization drives distal lung growth. As alveolarization
slows, the vasculature transitions from a phase of angiogenic growth to quiescence, however the molecular
mechanisms regulating this transition remain poorly defined. This gap in knowledge confounds efforts to develop
targeted therapies to treat diseases of dysregulated angiogenesis and impaired alveolarization, including
bronchopulmonary dysplasia, the most common complication of preterm birth. We recently employed single cell
transcriptomics to define endothelial cell (EC) diversity during postnatal lung development and to identify novel
mechanisms regulating pulmonary angiogenesis and quiescence. Our preliminary data identified a tremendous
increase in EC diversity after birth, marked by the appearance of numerous transcriptionally distinct clusters. A
highly proliferative EC cluster is abundant before birth, virtually disappears just after birth, but peaks again at
early alveolarization, a time of exponential pulmonary angiogenesis. The microvascular EC (MEC) broadly
separated into Car4 expressing (Car4+) and Car4- MEC. In contrast with gradual changes in gene expression
in the Car4+ MEC over time, gene expression changed dramatically in the Car4- MEC, with separation of this
population into two transcriptionally distinct clusters of “early” (P1-P7) and “late” (P21) Car4- MEC. High
expression of the paternally imprinted gene-3 (Peg3), a gene expressed by self-renewing progenitor cells,
distinguished the “early” from the “late” Car4- MEC. Peg3 also enhances NFkB signaling, a pathway we
previously identified as essential for pulmonary angiogenesis during early alveolarization. Of note, the expression
of receptor-ligand pairs suggested that cross-talk stemming from the Car4+ MEC may promote pro-proliferative
and pro-angiogenic signaling in the Car4- MEC. Taken together, our data suggest the overall hypothesis that the
early Car4- MEC represent a specialized, highly proliferative and angiogenic EC population required for the rapid
growth of the pulmonary vasculature during early alveolarization, which will be tested through three specific aims.
Aim 1 will utilize transgenic and cell-specific knock out mice, advanced imaging, and loss of function studies in primary
EC to probe the role of Peg3 in promoting proliferation, angiogenesis and NFkB activation in Car4- MEC. Aim 2 will
use FACS sorted Car4+ and Car4- MEC and a novel mouse model permitting targeting of Car4+ MEC to test if
interaction between these two distinct MEC promotes postnatal angiogenesis. Finally, Aim 3 will employ
computational ligand-receptor analysis, ATAC-Seq, and EC-specific knock out mice to determine if chronic
hyperoxia impairs angiogenesis by impairing Car4- MEC proliferation, Peg3-mediated self-renewal and Car4+
and Car4- MEC cross-talk. The successful completion of ...

## Key facts

- **NIH application ID:** 10489285
- **Project number:** 5R01HL154002-02
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Cristina Maria Alvira
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $729,827
- **Award type:** 5
- **Project period:** 2021-09-15 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10489285

## Citation

> US National Institutes of Health, RePORTER application 10489285, Developmental Heterogeneity of Pulmonary Endothelial Phenotype at Single Cell Resolution (5R01HL154002-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10489285. Licensed CC0.

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