Bone marrow and periosteal skeletal stem/progenitor cells make distinct contributions to bone maintenance and repair.

A fundamental question in bone biology concerns the contributions of skeletal stem/progenitor cells (SSCs) in the bone marrow versus the periosteum to bone repair. We found that SSCs in adult bone marrow can be identified based on Lepr and Adiponectin-cre/creER expression while SSCs in adult periosteum can be identified based on Gli1 expression. Under steady-state conditions, new bone arose primarily from bone marrow SSCs.