Runner's niche: multipurpose stromal cells maintained by exercise.

Using newly developed reporter and lineage-tracing mice, Shen et al. found perivascular stromal cells coexpressing osteolectin and leptin receptor in the bone marrow that specifically supported lymphoid progenitors, served as osteoblast progenitors, and were maintained by mechanical stimulation. Exercise may thus have joint positive influences on lymphopoiesis and bone formation.