Stress-Induced Changes in Bone Marrow Stromal Cell Populations Revealed through Single-Cell Protein Expression Mapping

Stromal cell populations that maintain hematopoietic stem and progenitor cells (HSPCs) are generally characterized in steady-state conditions. Here, we report a comprehensive atlas of bone marrow stromal cell subpopulations under homeostatic and stress conditions using mass cytometry (CyTOF)-based single-cell protein analysis. We identified 28 subsets of non-hematopoietic cells during homeostasis, 14 of which expressed hematopoietic regulatory factors. Irradiation-based conditioning for HSPC transplantation led to the loss of most of these populations, including the LeptinR+ and Nestin+ subsets. In contrast, a subset expressing Ecto-5′-nucleotidase (CD73) was retained and a specific CD73+NGFRhigh population expresses high levels of cytokines during homeostasis and stress. Genetic ablation of CD73 compromised HSPC transplantation in an acute setting without long-term changes in bone marrow HSPCs. Thus, this protein-based expression mapping reveals distinct sets of stromal cells in the bone marrow and how they change in clinically relevant stress settings to contribute to early stages of hematopoietic regeneration. [Display omitted] •Single-cell mass cytometry defines 28 subsets of bone marrow stromal cells (BMSCs)•Cytokine profiling and persistence to radiation reveal BMSC niche candidates•LeptinR+ and Nestin+ putative niche cells are lost with radiation conditioning•CD73+ BMSCs contribute to HSPC engraftment and acute hematopoietic recovery Severe et al. used single-cell mass cytometry to define 28 subsets of bone marrow stromal cells based on protein expression. Cytokine production and response to stress functionally selected niche candidates. While LeptinR+ and Nestin+ cells were lost with conditioning, CD73+ subpopulations contribute to HSPC engraftment and acute hematopoietic recovery.