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25/27在牙齿发育和牙髓再生过程中的功能意义。本研究表明，热休克蛋白25/27只表达在完全分化的成牙本质细胞在牙齿发育过程中。为观察牙髓再生情况，选用4周龄和100日龄Wistar大鼠，分别进行牙再植和窝洞制备。窝洞制备后，成牙本质细胞与前牙本质间出现水肿反应，但成牙本质细胞内仍有Hsp 25/27的免疫反应。12小时后，退变的成牙本质细胞层中Hsp 25/27免疫反应消失。术后3天，新分化的成牙本质细胞取代了退化的成牙本质细胞，并开始表现出热休克蛋白25/27的免疫反应。再植牙早期Hsp 25/27免疫阳性细胞消失。术后5d，牙本质-牙髓交界处细胞饱满，核仁清晰，呈Hsp 25/27免疫活性。这些结果表明，新分化的成牙本质细胞获得Hsp 25/27的免疫反应在再生牙髓组织洞制备和牙齿再植。在牙髓间隙骨样组织形成的病例中，牙髓-牙本质边缘沿着无Hsp 25/27免疫阳性细胞。因此，Hsp 25/27免疫阳性细胞沿着牙髓-牙本质边界排列是诱导再植牙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.