In vitro evaluation of TAT-OP1 osteogenic properties and prospects for in vivo applications.

So far, osteogenic protein 1 (OP1) is biotechnologically produced and approved for the treatment of human lumbar spine fusion and long bone non-union fractures. When combined with the TAT sequence, it has been demonstrated in vitro to be easily taken up by PC12 neuronal cells and to acquire its biological activity after intracellular refolding. In this study, TAT-OP1 was shown to be a useful strategy to efficiently drive denatured OP1 into mouse MC3T3E1 pre-osteoblasts. The correct in vitro protein refolding was verified by the activation of the BMP cascade, while the osteogenic potential of OP1 was demonstrated by increased expression of alkaline phosphatase, osteonectin and osteocalcin.