Spatiotemporal expression of extracellular matrix components during the chondrogenic and osteogenic phases of bone healing.

In this study, we investigated the cascade of events involved in the early phases of bone healing in rats, especially the transition from chondrogenesis to osteogenesis, which involves cellular and extracellular matrix (ECM) components. We used a standardized closed tibial fracture model in Wistar rats, which was divided into nine groups of five animals each, and the fracture area was evaluated at 0, 12, 24, 48, 72, 96, 144, 192, and 240 hours post-injury. Histological, histochemical, immunohistochemical and morphometric techniques were used to evaluate the proliferating cell nuclear antigen (PCNA), transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), type I procollagen (procoll-I), type I collagen (coll-I), and type II collagen (coll-II) expression at every time point.