Muscle Cells in Bone Fracture Repair

A study published in Volume 14 of the journal Bone Research on July 06, 2026, led by Dr. Ugur M. Ayturk and colleagues from the Skeletal Health and Orthopedic Research Program in the USA, revealed that muscle-resident fibroadipogenic progenitors (FAPs) and a smaller population of superficial periosteal cells play an unexpected and vital role in repairing fractured bones. The researchers engineered a mouse model utilizing Clec3b expression as a highly specific marker to track these dormant progenitor cells under normal and injured conditions, discovering that they rapidly migrate to fracture sites and differentiate into osteoblasts and bone marrow stromal cells. Within three weeks following a fracture, approximately 28% of the osteoblasts in the healing callus originated from Clec3b-lineage cells, with skeletal muscle identified as the primary source of these regenerative cells compared to the periosteum. These cells also contribute to heterotopic ossification, where bone abnormally forms in soft tissues, suggesting that therapeutically activating or limiting Clec3b-lineage cells could enhance fracture healing or prevent unwanted abnormal bone growth after injuries.