Endothelialized callus organoids drive rapid regeneration of critical-size segmental long bone defects

To recapitulate the cellular complexity of the early fracture callus, we engineered human endothelialized callus organoids (hECOs) by co-culturing periosteum-derived skeletal progenitors with endothelial cells. This co-culture resulted in cellular self-assembly, leading to spatially organized, callus-like structures.

Endothelial cells promoted skeletal progenitor cell expansion, extracellular matrix maturation, and progression toward hypertrophic cartilage, hallmarks of endochondral ossification. Multi-omics analyses identified endothelial cell-mediated activation of regenerative programs associated with skeletal maturation, matrix remodeling, and angiogenesis. Following brief in vitro differentiation, macroscale aggregates of hECOs supported rapid host vascularization and regeneration of critical-size tibial defects in immunocompromised mice.