Adenoviral gene transfer in a rat fracture model

For the enhancement of fracture healing, either purified proteins or vectors for expression of growth factors in situ may be used. Adenoviral vectors directly convert cells to express a transgene. However, the cell types which are preferentially infected and the time of expression during fracture healing are currently not known. The adenoviral type 5 vectors used in this study are replication incompetent viruses, one encoding β-galactosidase (β-GAL) and one green fluorescent protein. Femora of 35 Sprague-Dawley rats were fractured. Three days after stabilization with Kirschner wire, 10¹² pfu viral suspension were injected into the fracture zone. As a control, five animals received injections of adenovirus type 2. Animals were sacrificed after 3 days, 1, 2 and 4 weeks. Fractures healed radiographically within 2-3 weeks. All specimens were examined for β-GAL and green fluorescent protein (GFP) expression. Fibroblast and osteoblasts within callus tissue displayed a high transgene expression (week 1). A decrease of expression was observed during the observation period. In this experimental study, we have demonstrated that all cells of the primary callus can be transfected using adenoviral vectors, which provide a tool to further investigate adenoviral transfer of growth factors such as bone morphogenetic protein-2 (BMP-2).