# Identification of unique nitric oxide-expressing hematopoietic stem cells and their special vascular niche

> **NIH NIH R01** · BETH ISRAEL DEACONESS MEDICAL CENTER · 2022 · $432,962

## Abstract

Project Abstract Hematopoietic stem cells (HSCs) reside in the regulatory microenvironment within the bone
marrow (BM), termed the niche. Despite extensive research efforts made over the past decades, cellular
constituents and locations of the HSC niche have remained controversial. While early studies suggested that
HSCs are adjacent to osteoblasts on the bone surface, a growing amount of more recent evidence indicate that
HSCs are rather adjacent to sinusoidal vessels in the central marrow; some other showed HSCs are near BM
arteries. These conflicting observations may be explained by the heterogeneity of HSCs and the niche, as well
as the paucity of markers to identify HSC subsets in the histological analysis. This project focuses on proposing
most primitive HSCs among others, and their niche. The overall hypothesis to be tested is that nitric oxide (NO)
identifies unprecedented HSCs with distinctly high self-renewing and reconstituting potential. We further
hypothesize that these NO+ HSCs are regulated by unique transitional vessels which connect arteries to
sinusoidal vessels, while NO- HSCs with a relatively limited self-renewing potential are adjacent to sinusoidal
veins. This hypothesis is based on the following preliminary data. We showed that, within
CD150+CD48+cKit+Sca1+Lin- HSCs, there was a quiescent population (5-10%) with high expression levels of
NO and CD200 receptors (CD200R). These NO+CD200Rhigh HSCs exhibited high blood reconstituting potential
which was further increased by serial transplant, while NO- HSCs' reconstituting potential was relatively limited
and abolished by serial transplant. This observation suggest NO+ HSCs possess a distinctly high self-renewal
and reconstituting potential. Moreover, NO+ HSCs were adjacent to transitional vessels, while NO- HSCs were
adjacent to sinusoids which did not express cilia or CD200. To further bring mechanistic insights into NO+ HSCs
and their niche and to promote clinical translation of our basic findings, we will pursue the following aims. In Aim
1, we will seek to characterize NO+ HSCs' self-renewal, reconstituting potential and molecular features, and
elucidate their intrinsic regulatory mechanisms of NO+ HSCs, by using the combination of single cell RNA
sequencing, transplantation assay, genetic deletion, and in vivo microscopy tracking of symmetric or asymmetric
division of photolabeled individual HSCs. In Aim 2, we will elucidate NO+ HSCs' locations and extrinsic regulatory
mechanisms. We will validate localization of NO+ HSCs to transitional vessels by performing deep whole-mount
2-photon BM imaging of novel HSC-reporter mice. We will further elucidate roles of transitional vessels' CD200
and cilia in HSC regulation and protection from radiation stress. We will finally investigate therapeutic potential
of CD200R agonist treatment to mitigate post-irradiation hematopoiesis failure. Completion of the project may
address the controversy about the niche location by proposing unp...

## Key facts

- **NIH application ID:** 10398258
- **Project number:** 5R01DK121889-03
- **Recipient organization:** BETH ISRAEL DEACONESS MEDICAL CENTER
- **Principal Investigator:** Joji Fujisaki
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $432,962
- **Award type:** 5
- **Project period:** 2021-04-28 → 2024-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10398258

## Citation

> US National Institutes of Health, RePORTER application 10398258, Identification of unique nitric oxide-expressing hematopoietic stem cells and their special vascular niche (5R01DK121889-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10398258. Licensed CC0.

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