# Investigating the requirement and regulation of vascular progenitors derived from the Second Heart Field in Pharyngeal Arch Artery development

> **NIH NIH F31** · RBHS-NEW JERSEY MEDICAL SCHOOL · 2022 · $40,959

## Abstract

PROJECT SUMMARY
The improper formation or remodeling of the Pharyngeal Arch Arteries (PAAs) are among some of the most
severe and life-threatening forms of congenital heart disease, such as those seen in patients with DiGeorge
Syndrome. We have previously shown that the PAA endothelium originates from a subpopulation of mesodermal
progenitors termed the Second Heart Field (SHF). In addition, Vascular Endothelial Growth Factor Receptor 2
(VEGFR2), an RTK which is required for vascular development is highly expressed in these SHF progenitors as
they contribute the PAAs. However, to what extent SHF-derived ECs are required for PAA formation, and the
mechanisms which regulate the contribution of SHF progenitors to PAAs remains unclear. To address this, we
developed a mouse model to conditionally ablate VEGFR2 from the SHF by crossing VEGFR2GFP/+;Isl1Cre/+ and
VEGFR2f/f;Rosa26mTmG/mTmG, with the initial hypothesis that the loss of VEGFR2 from SHF vascular progenitors
would lead to the absence of PAAs. Unexpectedly, we saw VEGFR2-positive endothelium in
VEGFR2GFP/f;Isl1Cre/+ mutant embryos in which VEGFR2 is deleted in the SHF. However, pharyngeal
endothelium in these mutants was hypoplastic and disorganized in comparison to control embryos. The use of
the Cre reporter Rosa26mTmG demonstrated that these VEGFR2-positive ECs are not of SHF origin but instead,
are from another progenitor source, suggesting a possible role for endothelial compensation. Interestingly,
embryos heterozygous for VEGFR2 in the SHF lineage showed an impediment in SHF progenitor contribution,
in addition to the disorganized and irregular phenotype seen in the knockout embryos, suggesting a possible
haploinsufficiency of VEGFR2 in the SHF. Thus, we hypothesize that the SHF contains vascular progenitors
essential for proper formation and remodeling of the PAAs. Further, we hypothesize that endothelial cell (EC)
progenitors from pre-existing vasculature contributes to the PAAs when SHF contribution is attenuated. Here,
we propose to test these hypotheses by addressing the following specific aims: 1) To determine the requirement
and mechanisms regulating SHF-derived EC contribution in PAA development; 2) To identify the EC progenitor
source(s) that contribute to PAA development when SHF-derived EC contribution is compromised; 3) To
determine mechanism(s) that regulate the compensation of PAA ECs when SHF-derived EC contribution is
compromised. We will utilize conditional knockout mouse models and immunohistochemistry to fate map and
identify the requirement of SHF vascular progenitors in PAA development, and to identify the sources of the non-
SHF-derived ECs in the PAAs of embryos null for VEGFR2 in the SHF. Furthermore, we will use a combination
of immunohistochemistry and in situ hybridization to provide insight on the mechanisms regulating these vascular
progenitors in PAA development. Elucidating sources and mechanisms that drive PAA formation will lead to a
better understanding...

## Key facts

- **NIH application ID:** 10388192
- **Project number:** 5F31HL150949-03
- **Recipient organization:** RBHS-NEW JERSEY MEDICAL SCHOOL
- **Principal Investigator:** AnnJosette Ramirez
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $40,959
- **Award type:** 5
- **Project period:** 2020-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10388192

## Citation

> US National Institutes of Health, RePORTER application 10388192, Investigating the requirement and regulation of vascular progenitors derived from the Second Heart Field in Pharyngeal Arch Artery development (5F31HL150949-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10388192. Licensed CC0.

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