Figure 4. HOTAIR knockdown attenuates BMP9-induced ectopic bone formation from iMAD cells in vivo. (A) Gross view (a) and μCT imaging (b) of the BMP9-induced ectopic bone formation from iMAD-Ctrl and iMAD-KD cells. The retrieved bone masses from indicated groups were imaged using μCT followed by 3D reconstruction (b). No detectable masses were retrieved from the Ad-GFP-transduced iMAD-Ctrl or iMAD-KD cells group. (B) The average bone volumes (a) and average bone density (b) for the indicated groups were determined and analyzed using the Amira program. Representative images are shown. “**” p < 0.05, iMAD-Ctrl+BMP9 group vs iMAD-KD+BMP9 group. (C) HE (a) and Trichrome staining (b) of the retrieved bone masses. Representative images are shown. TB, trabecular bone; MSCs, undifferentiated MSCs.