HUMAN OSTEOCLASTOMA-DERIVED STROMAL CELLS - CORRELATION OF THE ABILITY TO FORM MINERALIZED NODULES IN-VITRO WITH FORMATION OF BONE IN-VIVO

It has been suggested that the stromal element of human osteoclastomas contains osteoblastic cells, In this study, we demonstrate that osteo clast-depleted, passaged stromal cells express alkaline phosphatase an d osteocalcin in vitro and form mineralized nodules under appropriate culture conditions, In addition, we describe a model in which severe c ombined immunodeficient (SCID) mice were used to support the different iation of these putative human osteoblast progenitors in vivo, Lesions formed from human stromal cells were identified using the OKa blood g roup antigen and human procollagen type I antibodies, By 21 days, the lesion was a complete bone unit: a fully mineralized cortex, remodelin g trabeculae, and a highly cellular marrow space, Stromal cells derive d from six out of seven osteoclastomas produced identical lesions, Fur ther studies have demonstrated that the capacity of the osteoclastoma- derived stromal cells to form bone in vivo and in vitro is passage dep endent; early passages were osteogenic in both model systems, while la ter passages were not, In conclusion, we have developed a model in whi ch the osteogenic nature of cells can be confirmed in vivo, Furthermor e, human osteoclastoma-derived stromal cells provide a source of these osteogenic cells to study human osteoblast differentiation, both in v ivo and in vitro.