Gene

Osteoblast

Cell biology

Haematopoiesis

Ecology

Biology

Mesenchymal stem cell

Stromal cell

Stem cell

Cartilage

Cancer research

Bone marrow

Chondrocyte

Computational biology

Evolutionary biology

Immunology

Genetics

Niche

Osteocyte

Anatomy

In vitro

Transcription factor

Phenotype

Cellular differentiation

Cell Reports

The bone marrow microenvironment is composed of heterogeneous cell populations of non-hematopoietic cells with complex phenotypes and undefined trajectories of maturation. Among them, mesenchymal cells maintain the production of stromal, bone, fat, and cartilage cells. Resolving these unique cellular subsets within the bone marrow remains challenging. Here, we used single-cell RNA sequencing of non-hematopoietic bone marrow cells to define specific subpopulations. Furthermore, by combining computational prediction of the cell state hierarchy with the known expression of key transcription factors, we mapped differentiation paths to the osteocyte, chondrocyte, and adipocyte lineages. Finally, we validated our findings using lineage-specific reporter strains and targeted knockdowns. Our analysis reveals differentiation hierarchies for maturing stromal cells, determines key transcription factors along these trajectories, and provides an understanding of the complexity of the bone marrow microenvironment.

Mapping Distinct Bone Marrow Niche Populations and Their Differentiation Paths