Gene therapy for bone formation: In vitro and in vivo osteogenic activity of an adenovirus expressing BMP7

Bone morphogenetic proteins (BMPs) are well-established agents for inducing orthotopic and ectopic bone formation. However, their clinical usefulness as regenerative agents may be limited by a short in vivo half-life and low specific activity. BMP gene therapy is an alternative route for exploiting the bone-inductive activity of this class of molecules. To test the feasibi lity of this approach, we examined the osteogenic activity of AdCMV-BMP7, a n adenovirus containing BMP7 cDNA under control of the CMV promoter that wa s constructed using Cre/lox recombination (Hardy et at. [1997] J. Virol. 71 .1842-1849). Adenovirus vectors were shown to readily infect a wide variety of cell types in vitro including osteoblasts, fibroblasts, and myoblasts. COS7 cells transduced with AdCMV-BMP7 produced high levels of BMP-7 (approx imately 0.5 mu g/10(6) cells). Furthermore, transduction of C2C12 murine my oblast cells with AdCMVBMP-7 suppressed the muscle phenotype and induced in vitro osteoblast differentiation. To test its in vivo biological activity, AdCMV-BMP7 was mixed with a bovine bone-derived collagen carrier (10(8) pl aque-forming units virus/site) and was implanted into mouse muscle and derm al pouches. In both cases, an ossicle containing cortical and trabecular bo ne and a clearly defined marrow cavity formed at the site of virus implanta tion within 4 weeks. These data demonstrate that AdCMV-BMP7 transduced cell s produce biologically active BMP-7 both in vitro and in vivo and show that gene therapy by direct viral transduction using a virus/matrix implant may be a viable route for stimulating bone regeneration. (C) 2000 Wiley-Liss, Inc.