# Image guided profiling of the native HSC niche

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $308,635

## Abstract

The concept of the stem cell niche is central both to the fundamental understanding of how stem cells are
regulated by their microenvironment, and to clinical translation that targets the microenvironment for
improving therapeutic outcome. The bone marrow (BM), where hematopoietic stem cells (HSCs) reside, is a
crowded space packed with a diversity of cell types derived from both hematopoietic and nonhematopoietic
precursors. A major challenge in studying the HSC niche has been the difficulty in identifying the rare HSCs
and their neighboring cells in the native BM microenvironment. Elegant cell type-specific deletion of molecules
critical for HSC maintenance has led to the identification of vascular endothelial cells (ECs) and
CXCL12-abundant reticular (CAR) cells as two major cell types of the HSC niche. However, deletion of such
factors impacts all ECs and CAR cells that are present throughout the BM, and are therefore not specific in
terms of their local impact in the HSC niche. Direct imaging has the potential to uncover which cell types are in
close contact with the HSCs, provided that specific markers are available for all cell types involved. As
markers for HSCs are now just beginning to emerge, and visualization of minor cell types remains a
challenge, the direct imaging approach has not progressed beyond resolving whether HSCs are in proximity
to ECs, CAR cells, or bone-lining osteoblasts. Imaging on its own also does not provide the molecular
information essential for understanding how the signals from the niche are communicated to the HSCs. We
propose that two things are needed for the field to move forward. First, development of an HSC-specific
reporter mouse will enable the identification of endogenous stem cells in their native microenvironment
without transplantation. Second, development of a method to selectively isolate the cells in close proximity to
the HSCs will enable unbiased profiling of cell types and their molecular signatures (for example, by
single-cell RNA sequencing) involved in HSC maintenance. We have now taken steps to address both of
these needs. First, we have developed (Camargo Lab) a dual genetic strategy in mice that restricts reporter
labeling near exclusively to the most quiescent long-term subset of the HSC compartment (LT-HSCs). This
reporter line is fully compatible with current intravital imaging approaches in the calvarial BM and enables live
animal tracking of native HSCs (Lin Lab) based on the expression of the green fluorescent protein (GFP)
alone, without the need for additional markers and without transplantation. In addition, we have developed a
technique for micropipette aspiration of single cells and cell clusters directly from the BM under two-photon
image guidance, enabling single cell analysis with high spatial definition. Here, we propose to bring the two
teams together to work on an integrated approach for marking, isolating and profiling the native HSCs
together with their neighboring “ni...

## Key facts

- **NIH application ID:** 10018892
- **Project number:** 5R01DK123216-02
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Fernando Camargo
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $308,635
- **Award type:** 5
- **Project period:** 2019-09-17 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10018892

## Citation

> US National Institutes of Health, RePORTER application 10018892, Image guided profiling of the native HSC niche (5R01DK123216-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10018892. Licensed CC0.

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