The piMEFs can effectively undergo ostepgenic, chondrogenic and adipogenic differentiation upon BMP9 stimulation <i>in vivo</i>.

<p>(<b>A</b>) The piMEFs without the removal of SV40 T Ag form larger ectopic bone masses. Subconfluent piMEFs were co-infected with BMP9, GFP and/or FLP for 16 h. The same number of cells were collected and injected into the flanks of athymic mice subcutaneously. Bony masses were retrieved from mice after 4 wk and subjected to µCT imaging. The scanning data were analyzed with Amira 5.3 software to obtain 3D iso-surface images. No masses were formed in the cells transduced with AdGFP or AdFLP alone. Representative results are shown. (<b>B</b>) The volumetric and relative density data of the ectopic bone masses were analyzed using the software Amira 5.3. HU, Hounsfield unit. (<b>C</b>) H & E, Alcian Blue, and Trichrome staining. The retrieved masses were fixed, decalcified, and subjected to H & E, Alcian Blue, and Trichrome staining. AC, adipocyte; CC, chondrocyte; OC, osteocyte.