Regulatory mechanism of cell differentiation and functional manifestation in the dental pulp.

本研究旨在阐明牙髓细胞分化和功能表现的调控机制和因素。体外实验研究了培养的牙髓细胞的增殖和分化特性。通过体内实验研究了牙髓细胞向成牙细胞的分化。采用4-META/MMA-TBB-O粘接树脂对暴露牙髓进行原位实验，研究牙髓细胞的增殖和分化情况。体外实验表明，与牙周韧带、骨髓和肌肉细胞相比，培养的牙髓细胞碱性磷酸酶活性较高，但增殖活性较低。碱性磷酸酶定位于牙髓细胞正下方的成牙层。完整牙髓未检出增殖细胞核抗原（PCNA）阳性细胞。体内实验表明，牙髓与牙本质相关移植或植入硅胶管后，牙髓细胞可分化为成牙细胞。然而，当只移植牙髓时，只产生骨组织而不产生牙本质。无菌大鼠牙髓部分切开术观察到牙本质桥的形成，而全牙髓切开术未观察到牙本质桥的形成。这些结果可能表明微环境是牙髓细胞向成牙细胞分化的必要条件。4-META/MMA-TBB-O树脂直接作用于牙髓组织的原位实验表明，虽然应用的牙髓组织既没有坏死也没有炎症，但牙本质桥的形成仅占40%左右。长期观察部分病例树脂或牙本质桥附近可见大量巨噬细胞。本研究的超微结构结果证实了软组织杂交层的存在。生化分析表明，从聚合树脂和软组织杂化层中溶解了一些元素，包括碳酸、硼酸和4MET。这些因素可能不仅影响牙髓细胞的分化，而且影响巨噬细胞的外观。少

The purpose of the present study is to clarify the regulatory mechanisms and factors of cellular differentiation and functional manifestation in the cells of the dental pulp. In vitro experiments were performed to make clear the proliferative and differentiating natures of cultured cells of the dental pulp. In vivo experiments were carried out for invetigating the differentiation from dental pulp cells into odontoblasts. In situ experiments were fulfilled to elucidate the proliferation and differentiation of the dental pulp cells by means of the application of an adhesive resin 4-META/MMA-TBB-O on the exposed dental pulp.In vitro experiments showed that the cultured pulp cells had high alkaline phosphatase activity but low proliferative activity in comparison with cultured cells from periodontal ligament, bone marrow and muscle. Localization of alkaline phosphatase was definite at the dental pulp cells just below the odontoblast layr. No positive cell for proliferative cell nuclear ant … More igen (PCNA) was detected in the intact dental pulp. In vivo experiments demonstrated that the dental pulp cells could differentiated into odontoblasts following transplantation of the dental pulp associated with dentin or into a silicone-tube. However, bone tissue but not dentin was produced when the dental pulp alone was transplanted. Dentin bridge formation was observed in the partial pulpotomy but not in the total pulpotomy in germ-free rats. These results may suggest that the microenvironment is essential for differentiation from dental pulp cells into odontoblasts. In situ experiment using 4-META/MMA-TBB-O resin directly on the pulp tissues indicated that dentin bridge formation was found only about 40%, although neither necrosis nor inflammation could be recognized in the applied pulp tissues. A large numbers of macrophages were detected adjacent to the resin or dentin bridge in some cases of long term observation. Ultrastructural findings of the present study demonstrated the existence of the soft tissue hybrid layrs. Biochemical analysis implied the dissolution of some elements including carbonic acid, boric acid, and 4MET from the polymerized resin and the soft tissue hybrid layr. It is suggested that these elements may influence not only the cellular differentiation of the pulp cells but also the appearance of macrophages. Less