The Interplay of Angiogenesis and Osteogenesis in Non‐Stabilized Incomplete Tibial Fractures: A Temporal Study in Rats

Prior research on angiogenesis and osteogenesis during bone fracture healing has primarily focused on stabilized models, often within controlled environments. However, the dynamic interplay of these processes in the context of long bone fractures without scaffolds or external factors remains poorly understood. This study investigated the temporal dynamics of angiogenesis and osteogenesis in a non-stabilized incomplete transverse tibia bone fracture model. Multi-modal observation approach was carried out using micro-CT analysis of bone mineral density, histological assessment of fracture healing, and confocal microscopy for visualization and co-localization of key angiogenic (CD31, endomucin) and osteogenic (collagen 1, osteocalcin, PDGFRB) markers. Our findings revealed a dynamic and interdependent relationship between these processes. H type blood vessels persisted throughout the healing process, and significant correlations were observed between the expression of angiogenic and osteogenic markers. The role of hypoxia, a critical regulator of both processes, was investigated by analyzing HIF1-α expression. Increased expression of SLIT3, a guidance molecule, was also observed at later stages of healing, suggesting its potential involvement in vascular remodeling. These findings provide crucial insights into the molecular mechanisms underlying bone fracture repair in the absence of additional supporting external elements such as scaffolds or stabilizers. By elucidating the temporal dynamics of these key processes, we identify potential targets for therapeutic interventions aimed at accelerating and optimizing bone regeneration. Consideration of these interactions can lead to the development of effective clinical strategies for enhancing bone healing in non-stabilized incomplete fractures.