Cellular and molecular mechanisms of accelerated fracture healing by COX2 gene therapy

► COX2 gene therapy accelerates healing of multiple tibial fractures in the mouse. ► COX2 gene therapy increases recruitment and/or expansion of certain mesenchymal stem cell subpopulations in fracture calluses. ► COX2 gene therapy decreases cartilaginous callus formation during fracture healing. ► COX2 gene therapy increases angiogenesis-dependent cartilage remodeling. ► These effects of COX2 gene therapy are associated with an earlier onset of bony bridging of the fracture gap.