A NOVEL HUMAN BONE-MARROW STROMA-DERIVED CELL-LINE TF274 IS HIGHLY OSTEOGENIC IN-VITRO AND IN-VIVO

A novel, immortalized, human bone marrow stroma-derived cell line TF27 4 is described which has the ability to form bone both in vitro and in vivo. Under basal conditions these cells expressed alkaline phosphata se (ALP) and type I collagen genes which are characteristic of the ost eoblast phenotype. ALP levels were upregulated in the presence of oste otropic agents such as parathyroid hormone (PTH), transforming growth factor beta (TGF-beta), and BMP-2. In addition, PTH also increased cAM P levels in these cells. The capacity of these cells to form bone in v itro was evaluated by culturing them in the presence of L-ascorbic aci d and P-glycerophosphate. Matrix mineralization in these cultures was assessed by Alizarin Red staining and increased Ca-45 uptake. Under th ese conditions mineralized nodule formation was observed in less than 2 weeks. Northern analysis of TF274 cells at various times during the mineralization process indicated a temporal expression of the osteocal cin gene that is typically associated with differentiating osteoblasts . The osteogenic nature of TF274 cells was confirmed in vivo using the severe combined immunodeficient (SCID) mouse model. Antibodies to hum an leukocyte antigens (HLA), class I antigens, and human OKa blood gro up antigen were used to demonstrate that the lesions formed were of hu man origin. By 21 days, the lesion consisted of a homogeneous focus of ALP-positive cells containing areas of mineralized bone lined with ta rtarate-resistant acid phosphatase (TRAP) positive osteoclasts. Thus, the TF274 cells exhibit osteogenic potential both in vitro and in virt o. This immortalized cell line represents a consistent source of cells that can be used to study human osteoblast differentiation both in vi tro and in vivo.