Interaction between odontoblastic syncytium coupled through gap-junction and pulpal nervous and circulatory system

我们首次在电生理上发现成牙髓细胞之间存在方向无关的间隙连接，以及成牙髓细胞与牙髓下细胞之间存在方向依赖的间隙连接。这些交流可能在成牙层形成功能性合胞体。所谓的“流体力学理论”是以牙本质小管中的流体运动为基础的。然而，它们的内径比牙釉质侧的内径大得多。也就是说，由于小管的直径太大，动水压力无法提高。我们使用不同直径和激发波长的荧光微球测量成牙本质突与牙本质小管壁之间的功能空间。细小的微球（<0.04μm）可到达牙髓。这个小空间可能有助于高流体动压，从而触发传入末端的动作电位并激活成牙干细胞膜上的机械敏感离子通道。肾上腺素能β2受体与骨形成有关。我们发现β2受体在人成牙细胞层具有免疫反应性。我们还发现冷敏感TRP通道和淋巴管的免疫反应性。因此，血液和淋巴循环、冷接受性和交感β2受体之间的相互作用可能有助于牙本质的发生。

We electrophysiologically showed direction-independent gap-junctionalcommunication between odontoblasts and direction dependent gap-junction betweenodontoblasts and underneath pulpal cells for the first time. These communicationsmay form a functional syncytium in the odontoblastic layer.So-called “the hydrodynamic theory” is based on the fluid movement in the dentinaltubules. However, their inner diameters are much larger than those in the enamel side.That is, hydrodynamic pressure could not be elevated due to this large diameter oftubules. We measured the functional space between odontoblast processes and the wallof dentinal tubules using fluorescent microspheres with different diameters andexcitation wave lengths. Small microspheres (<0.04μm) could reach the pulp. Thissmall space may contribute to the high hydrodynamic pressure that trigger actionpotentials in afferent terminals and activate mechanosensitive ion channels inodontoblast cell membrane.Adrenergic β2 receptors are associated with bone formation. We found β2 receptorimmunoreactivity in the human odontoblastic layer. We also found theimmunoreactivity of cold sensitive TRP channels and lymphatic vessels. Thus,interactions among blood and lymphatic circulation, cold receptiveness, andsympathetic β2 receptors, and may contribute to dentinogenesis.