IDENTIFICATION OF OSTEOPONTIN IN HUMAN DENTAL CALCULUS MATRIX

Osteopontin is a prominent non-collagenous component of bone matrix, a lthough it is expressed in several other tissues. Recently, osteoponti n was reported to be involved in urinary stone formation and atheroscl erotic lesions of the aorta, suggesting that it may be a key protein a ssociated with these types of pathological mineralization. In this stu dy, whether or not human dental calculus contains osteopontin was inve stigated by immunoblotting and immunohistochemical analyses. After ext raction of calculus proteins with EDTA and separation of the proteins by electrophoresis, immunoblotting analysis revealed the presence of o steopontin. Two forms of osteopontin appeared at 61 and 68 kDa on 10% polyacrylamide gel and the proteins were digested with thrombin, a hig hly specific protease. Moreover, immunohistochemical analysis revealed that osteopontin was localized in dental calculus adherent to tooth r oots. These findings indicate that osteopontin is, in fact, present in human dental calculus and may be involved in calculus formation as th e stone matrix.