The influence of immunosuppressant, FK506 in ex vivo bone morphogenetic protein-2 gene delivery on bone regeneration

Abstract

1. Objective Tacrolimus hydrate (FK506) is a macrolide antibiotic with a different chemical structure but a mechanism of action similar to cyclosporine. It has been suggested that FK506 could stimulate the inherent osteogenic activity to increase bone formation as well as suppress the immune reaction to the constructs. The aim of the present study was to evaluate the influence of immunosuppressant, FK506, on bone regeneration following ex vivo bone morphogenetic protein (BMP-2) gene delivery in rat calvarial defects. 2. Materials and methods Thirty-six male Sprague-Dawley rats were used in this study. A 8 mm craniotomy defect was created by using a trephine bur. Six animals were randomly assigned to one of the following experimental groups: (1) non-grafted group, the defect was left empty, (2) HGF group, the defect was filled with non-transduced HGFs and collagen matrix, (3) BMP-2/HGF group, the defect was filled with BMP-2-transduced HGFs and collagen matrix. Half of animals of the each group assigned to FK506(+) group, were received FK506 injection. And the other half of animals assigned to FK506(-) group were not administrated FK506. Animals were sacrificed at 2 and 4 weeks after surgery, histologic observations and measurement of regenerated bone were performed. 3. Results The BMP-2/HGF groups showed promoted osseous healing of calvarial defects, as compared to the other groups. Comparing the groups with and without FK506, regenerated bone area was significantly greater in the BMP-2/HGF groups at 4 weeks. In non-grafted and HGF group, the amounts of regenerated bone were similar irrespective of immunosuppressive treatment. Infiltration of inflammatory cells was pronounced in groups without FK506, especially HGF and BMP-2/HGF group at 2 weeks. 4. Conclusion This investigation demonstrated the positive influence of FK506 on bone regeneration following ex vivo BMP-2 gene delivery using xenogenic cells. In gene therapy using xenogenic cell source, the use of immunosuppressive agent is recommended to reduce inflammatory response and obtain favorable results.