Functional Contribution of the Marrow Stromal Cell Population and the Effect of Oral Dihydrotachysterol Treatment

This study investigates the proliferative and osteogenic role of marrow stromal/osteoprogenitor cells in the development ofthe cortical bone deficit in ovariectomized (OVX) female rats. In vitro, clonal growth ofmarrow stromal cells fromOVX rats was significantly impaired (vs. sham-operated controls). Yet in vivo, cells from sham-operated and OVX rats had equal osteogenic potential in several in vivo experimental situations, such as in intraperitoneally implanted millipore diffusion chambers and in intramuscular implants ofmarrow plus osteoinductive bone matrix (composite grafts). Long-term (6 mo) dihydrotachysterol (DHT) treatment ofOVX rats enhanced their in vitro proliferative potential and clonal growth, as well as their osteogenic expression in composite grafts. The observation that the in vivo osteogenic performance ofOVX rat marrow stromal cells was normal at extraosseous sites suggests that the mechanisms leading to osteopenia may involve an abnormality in cell-matrix interactions.