Adenovirus-mediated BMP2 expression in human bone marrow stromal cells

Recombinant adenoviral vectors have been shown to be potential new tools fo r a variety of musculoskeletal defects. Much emphasis in the field of ortho pedic research has been placed on developing systems for the production of bone. This study aims to determine the necessary conditions for sustained p roduction of high levels of active bone morphogenetic protein 2 (BMP2) usin g a recombinant adenovirus type 5 (Ad5BMP2) capable of eliciting BMP2 synth esis upon infection and to evaluate the consequences for osteoprogenitor ce lls. The results indicate that high levels (144 ng/ml) of BMP2 can be produ ced in non-osteoprogenitor cells (A549 cell line) by this method and the re sultant protein appears to be three times more biologically active than the recombinant protein. Surprisingly, similar levels of BMP2 expression could not be achieved after transduction with Ad5BMP2 of either human bone marro w stromal cells or the mouse bone marrow stromal cell line W20-17. However, human bone marrow stromal cells cultured with 1 muM dexamethasone for four days, or further stimulated to become osteoblast-like cells with 50 mug/ml ascorbic acid, produced high levels of BMP2 upon Ad5BMP2 infection as comp ared to the undifferentiated cells. The increased production of BMP2 in ade novirus transduced re] Is following exposure to 1 CIM dexamethasone was red uced if the cells were not given 50 mug/ml ascorbic acid. When bone marrow stromal cells were allowed to become confluent in culture prior to differen tiation, BMP2 production in response to Ad5BMP2 infection was lost entirely . Furthermore, the increase in BMP2 synthesis seen during differentiation w as greatly decreased when Ad5BMP2 was administered prior to dexamethasone t reatment. In short, the efficiency of adenovirus mediated expression of BMP 2 in bone marrow stromal cells appears to be dependent on the differentiati on state of these cells.