Expression data from fracture hematoma tissue of young and old rats after 3days of rigid or semi-rigid fixation of an osteotomy

The long-term healing outcome of bone regeneration is known to depend not only on mechanical stability, but also on age and, more importantly, on the overlap of both parameters. Although especially the early healing period determines the healing outcome, it so far remains unclear which factor - mechanical loading or age - dominates this phase and how these factors interact on the molecular level in the early fracture hematoma. We used microarrays to detail the global programme of gene expression underlying the influence of fixation stability in young and old rats and identified distinct classes of regulated genes during this process. At day three post-osteotomy, gene expression analyses of fracture hematoma tissue were performed for four groups of Sprague-Dawley rats with a 1.5-mm osteotomy gap in the femora with varying age (12 vs. 52 weeks - biologically challenging) and fixator stiffness (ridig vs. semi-rigid - mechanically challenging).