Analysis of the Expressions and functions of the transcription factor (AP-1) in reparative dentinogenesis

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 12671855
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Conservative dentistry
• Research Institution: KYUSHU UNIVERSITY
• Principal Investigator: HIRATA Masako Kyushu Univ., Dental Hospital, Research associate, 歯学部・附属病院, 助手 (10153769)
• Co-Investigator(Kenkyū-buntansha): TANAKA Teruo Kyushu Univ., Science of Dentistry, Professor, 大学院・歯学研究院, 教授 (60077667) ; AKAMINE Akifumi Kyushu Univ., Science of Dentistry, Professor, 大学院・歯学研究院, 教授 (00117053) ; YAMAZA Takayosi Kyushu Univ., Science of Dentistry, Research associate, 大学院・歯学研究院, 助手 (80304814)
• Project Period (FY): 2000 – 2001
• Keywords: reparative dentin / drilling stimulation / rat molar / transcription factor / AP-1 / osteocalcin / dental pulp

Research Abstract

The aim of this study is to examine the regulatory mechanism in reparative dentin formation after cavity preparation. The mesial surface of rat first molar was prepared. Morphological changes and expressions of nuclear transcription factor (AP-1) and matrix protein (osteocalcin) at the dentin-pulp interface under the cavity were investigated by light, immunohistochemical, and immunoelectron microscopy. By light microscopy, after 0 and 2hours of the preparation, inflammatory changes were occurred at the interface, and damaged odontoblasts were completely separated from dentin matrix. After 1 to 3 days, odontoblast-like cells were gathered to the dentin/pulp interface under the cavity to synthesize reparative dentin matrix. After 10 days, reparative dentin with tubular structure was abundantly formed under the cavity.
By immunhistochemical microscopy, after 2days of the preparation, immunoreactivity for Jun-D was specifically observed at the nucleus of odontoblast-like cell in the dentin/pulp interface under the cavity. By immunoelectron microscopy, after 3 days of the preparation, osteocalcin was found in not only developed Golgi apparatus, but also vesicles and granules of odontoblast-like cell. Type I collagen fibrils were also contained in the vacuoles and secreted from the cells. Osteocalcin was also found on and around type I collagen fibrils of predentin of reparative dentin. In the dentin matrix, some dentinal tubules were filled with type I collagen stained with osteocalcin.
Therefore, it is suggested that AP-1 takes part in the regulation of the rapid formation of reparative dentin and blockage of the dentinal tubules exposed by cavity preparation. It is also indicated that osteocalcin may participate in the conservation of dental pulp vitality from external irritants by tooth preparation.