Solubilization and concentration of a bone-inducing substance from a murine osteosarcoma

The osteogenic factor from murine osteosarcoma was soluble in 4M guanidine-HCl. The precipitate that appeared after dialysis of the guanidine solution against deionized water showed a higher osteogenetic activity than did the initial dry powder of tumor tissue. Electron-microscopically, this bone-inducing fraction seems to be homogenous. Neither a fibrous nor collagenous cross-banded structure was observed in the fraction. Since the chemical analysis of the fraction also showed a relatively low content of hydroxyproline, the osteogenic factor is probably not collagen.