It is intended to provide a novel means of promoting the calcification of a bone in a desired part in vivo. A bone tissue is charged with negative ions by adding DMP1 (Dentin matrix protein 1) thereto. Thus, extracellular matrix binds to calcium phosphate and the calcification of the bone is promoted. By expressing DMP1 specifically in the bone tissue, DMP1 is produced in an appropriate amount and the matrix binds to calcium phosphate. As a result, bone density can be elevated and, in its turn, the calcification of the bone can be promoted without causing any side effects on osteogenesis.
