Histological evaluation of induced new bone formation by crude BMP

Crude bovine BMP was implanted into the thigh muscle pouch of mice. Tetracycline was injected 1 week and calcein was injected 2 weeks after implant. At 3 weeks after implant, the mice were sacrificed and reviewed histologically. Coexistence of calcified bone and osteoid was observed in Villanueva Goldner stained sections. Toluidine blue staining demonstrated cartilaginous matrix and adjacent locus, and spherical cells varying in shape and size were observed. Calcified lamellar bone was present in the border, and osteoid with osteoblast-like cells was found on the bone marrow side. Calcein labeling appeared as a strong line in the margin and was definitely observed as weak fluorescence in the center under fluorescence microscopy. These results suggest the presence of ossification mode different from the intramembranous and endochondral ossification modes.