920. Bone Regeneration with Xenogeneic BMP-2 Producing Fibroblasts.

Bone fractures such as pelvic fracture or sternal fracture could be a serious, life-threatening event requiring emergency medical care and lengthy rehabilitation. We have selected BMP-2 as a possible answer for the treatment of severe bone fractures. BMP-2 is known as the powerful inducers of osteogenic differentiation. Due to the short half-life of BMPs in vivo, continuous production of BMPs by gene therapy could be one of the good methods for the successful regeneration of a bone defect. We have tested ex-vivo approach for the regeneration of critical sized bone defect. We investigated whether xenogeneic BMP-2 producing cells had the ability to regenerate cortical bone at the diaphysis of a long bone in a rabbit without using a scaffold. We have constructed BMP-2 producing NIH3T3 and human foreskin fibroblasts. The expression levels of BMP2 were confirmed by ELISA. Osteogenic activities were determined by alkaline phaosphatase assay. Radiographic analysis was performed at 1, 2, 3, 4, 5 and 6 weeks after injection of the cells. Radiological union was observed beginning at 3 weeks after injection and complete thickness cortical bone was observed at 6 weeks after injection. The tibia was harvested at 6 weeks and histological examination was performed. The regenerated bone was almost identical to the normal cortical bone. Fibrous tissue was formed at the end of normal bone without the evidence of bone formation in the control. Immunohistochemical and histological staining was used to analyze the regenerated tissue. At one week after injection, inflammatory cells were observed. At four weeks after injection, cortical was similar to normal bone. At 6 weeks after injection, the structure of regenerated bone tissue was almost identical to that of the normal bone tissue. Osteocalcin expression was observed from regenerated bone osteocytes.Our results suggest that bone regeneration with BMP-2 could have induced the osteoblastic transformation of the pre-osteogenic cells which were recruited into the defect area. These results show that ex vivo gene therapy using BMP-2 producing fibroblasts could be an effective tool for the promoting of bone formation.Molecular Therapy (2006) 13, S355–S355; doi: 10.1016/j.ymthe.2006.08.1010 [ABSTRACT FROM AUTHOR]