Study on the role of heat shock protein 27 in the process of development and regeneration of dental pulp

本研究旨在阐明热休克蛋白(HSP)25/27在牙齿发育和牙髓再生中的功能意义。本研究表明，在牙齿发育过程中，HSP25/27仅在完全分化的成牙本质细胞中表达。为观察牙髓再生情况，4周龄和100日龄Wistar大鼠分别进行牙齿再植和窝洞准备。窝洞制备可引起损伤的成牙本质细胞与前牙本质之间的水肿性反应，但HSP25/27的免疫反应仍存在于损伤的成牙本质细胞中。12h后退变的成牙本质细胞层中HSP25/27免疫反应消失。术后3d，新分化的成牙本质细胞取代退化的成牙本质细胞，并呈HSP25/27免疫反应。牙齿再植初期，HSP25/27免疫阳性细胞消失。术后第5天，牙本质-牙髓交界处核仁清晰的肥大细胞显示HSP25/27免疫活性。这些结果表明，新分化的成牙本质细胞在空洞准备和再植后的再生牙髓组织中获得了HSP25/27的免疫反应。在牙再植后牙髓间隙形成骨样组织的情况下，牙髓-牙本质边界没有HSP25/27免疫阳性细胞。因此，HSP25/27免疫阳性细胞沿牙髓-牙本质边界的排列是诱导牙再植后修复性牙本质形成的决定性因素。

The present study aims to clarify the functional significance of heat shock protein (Hsp) 25/27 during tooth development and pulpal regeneration. The present study demonstrated that Hsp 25/27 was expressed exclusively in fully-differentiated odontoblasts during tooth development. For the observation of pulp regeneration, Wistar rats, 4-week-old and 100-day-old, were used for tooth replantation and cavity preparation, respectively. Cavity preparation caused an edematous reaction between the injured odontoblasts and predentin, but the immunoreaction for Hsp 25/27 remained in the injured odontoblasts. Subsequently, Hsp 25/27-immunoreactivity disappeared in the degenerated odontoblast layer after 12 hours. On postoperative 3 days, newly differentiated odontoblasts replaced the degenerated odontoblasts, and became to exhibit the immunoreaction for Hsp 25/27. Tooth replantation also caused the disappearance of Hsp 25/27-immunopositive cells at the initial stages. On postoperative 5days, plump cells with clear nucleoli at the dentin-pulp border became to show Hsp 25/27-immureactivity. These findings indicate that newly differentiated odontoblasts acquire the immunoreaction for Hsp 25/27 in the regenerated pulpal tissue after both cavity preparation and tooth replantation. There was no Hsp 25/27-immunopositive cell along the pulp-dentin border in the case of bone-like tissue formation in the pulp space following tooth replatation. Thus, the alignment of Hsp 25/27-immunopostive cells along the pulp-dentin border is suggestive of the decisive factor to induce the reparative dentin formation after tooth replantation.