Utilization of a murine model to investigate the molecular process of transphyseal bone formation.

The purpose of this investigation was to establish a model that allows efficient and broad-based molecular studies of bony bridge formation and to correlate basic histologic findings and novel in situ hybridization assays with previous studies. We disrupted the hindlimb tibial physis of skeletally immature mice. Histologic examination of the damaged limbs at weeks 1, 3, and 5 using the HBQ method and in situ hybridization for col2, col1O, Indian hedgehog (ihh), and vascular endothelial growth factor (VEGF) were consistent with previous reports in non-murine models documenting initial evidence of ossification at 1 week post-injury and a fully ossified bony bridge at 3 weeks. In situ hybridization assays documented the absence of ihh and VEGF in the disrupted region, suggesting that bone formation is not occurring via the process of endochondral ossification. We conclude that a murine model provides an excellent opportunity for further examination of the molecular mechanism of induced transphyseal ossification.