A study on mechanisms of odontoblast differentiation during reparative dentinogenesis.

为了阐明修复性牙本质形成过程中牙髓细胞向成牙本质细胞分化的机制，我们对与细胞分化相关的几个因素进行了免疫组织化学分析。实验结果如下：1.实验结果表明：在牙齿发育过程中，牙内上皮中laminin-5、整合素α6和β4亚基的差异表达可能参与了成釉细胞的分化。这些基底膜组成的变化也可能与成牙细胞分化有关。在早期龋病的牙髓中，MHCⅱ类抗原表达细胞（hla - dr阳性树突状细胞）主要聚集在与PGP 9.5免疫反应性神经纤维相关的无细胞区。在晚期龋中，积累的hla - dr阳性细胞与PGP 9.5免疫反应性神经纤维密切相关，尤其是在成牙层下方。II类分子不仅在树突状细胞中被识别，而且在髓质无髓神经的雪旺细胞中也被识别。这表明免疫系统和神经系统在牙髓炎症和修复过程中有协同作用。用Er: YAG激光或常规钻孔制备牙髓腔后的牙髓反应进行了评价。激光组对组织非特异性碱性磷酸酶的免疫反应性更明显。ox6免疫阳性细胞和PGP 9.5免疫反应神经纤维的分布模式明显相似。3 .在牙髓-牙本质边缘，可见ox6阳性MHCⅱ类抗原表达细胞聚集，成牙髓层下可见大量珠状PGP 9.5免疫反应神经纤维，提示其参与牙髓组织修复和修复性牙本质形成。大鼠磨牙移植后牙髓腔内硬组织形成过程中，骨钙素、骨桥蛋白、骨涎蛋白和牙本质涎蛋白等非胶原蛋白在冠状区、根管区和根尖区新形成的硬组织中表现出不同的分布规律。这表明每种硬组织都是由不同来源的细胞形成的。少

In order to elucidate mechanisms by which pulp cells differentiate into odontoblasts during reparative dentinogenesis, immunohistochemical analyses for several factors related to cell differentiation were performed. The results were as follows :1. During tooth development, differential expression of laminin-5 and integrin α6 and β4 subunits in the inner dental epithelium may be involved in ameloblast differentiation. These changes in basement membrane composition might be also related to odontoblast differentiation.2. In pulps affected by early caries, MHC class II antigen-expressing cells (HLA-DR-positive dendritic cells) aggregated mainly in the cell-free zone associated with PGP 9.5-immuno-reactive nerve fibers. In advanced caries, the accumulated HLA-DR-positive cells and PGP 9.5-immunoreactive nerve fibers showed close association with each other especially beneath the odontoblast layer. Class II molecules were recognized not only in dendritic cells but also in the Schwann cells o … More f non-myelinated nerves in the pulp. These suggested a synergistic action between immune and nervous systems in pulpal inflammation and reparative process.3. Pulpal responses after cavity preparation with either Er : YAG laser or a conventional drill were evaluated. The immunoreactivity for tissue non-specific alkaline phosphatase was more pronounced in the laser group. Clear similarities in the distribution patterns of OX6-immunopositive cells and PGP 9.5- immunoreactive nerve fibers were noted. OX6-positive MHC class II antigen-expressing cells accumulated along the pulp-dentin border and numerous bead-like PGP 9.5-immunoreactive nerve fibers were observed under the odontoblastic layer, suggesting their involvement in pulp tissue repair and reparative dentin formation.4. During hard tissue formation in the pulp cavity of rat molar after transplantation into subcutaneous tissue, non-collagenous proteins, such as osteocalcin, osteopontin, bone sialoprotein and dentin sialoprotein showed different distribution patterns in newly-formed hard tissues in the coronal, root canal and apex areas, respectively. These suggested that each hard tissue was formed by differently-derived cells. Less