Sahara N, Toyoki A, Ashizawa Y, Deguchi T, Suzuki K
Department of Oral Histology, Matsumoto Dental College, Shiojiri, Japan.
Anat Rec. 1996 Jan;244(1):33-49. doi: 10.1002/(SICI)1097-0185(199601)244:1<33::AID-AR4>3.0.CO;2-G.
In human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentine prior to shedding, and this resorption shows clear time-related histological changes (Sahara et al., 1992).
Using this phenomenon as an observation system, we examined the cytodifferentiation of human odontoclasts by light and electron microscopy. For a histochemical marker of odontoclast differentiation and function, tartrate-resistant acid phosphatase (TRAP) activity was determined by light and electron microscopic enzyme histochemistry.
As root resorption neared completion, TRAP-positive mononuclear cells were initially detected in the pulp chamber. They had abundant mitochondria, small lysosomes, and moderately developed rough endoplasmic reticulum throughout their cytoplasm. In these mononuclear cells, TRAP activity was localized in compartments of the biosynthetic pathway, i.e., in cisternae of the endoplasmic reticulum and Golgi lamellae, as well as small lysosomes. The TRAP-positive mononuclear cells first made contact with the predentine surface by their elongated cellular processes. After attachment, they spread out along the predentine surface and developed specialized membrane structures, clear zones, and ruffled borders. Next, they fused with each other on the predentine surface and formed typical multinucleate odontoclasts. After termination of their resorption function, the odontoclasts lost their ruffled borders and became detached from the resorbed surface. Most of the detached odontoclasts had numerous large pale vacuoles and secondary lysosomes and appeared to be in the process of degeneration.
The present study demonstrates that: (1) odontoclasts differentiated from TRAP-positive mononuclear cells, which presumably originate from circulating progenitor cells, (2) membrane specialization of odontoclasts, i.e., development of a clear zone and ruffled border, is induced following their contact with the resorption surface, (3) multinucleation of odontoclasts takes place only after their attachment to the resorption surface, (4) mature multinucleate odontoclasts can resorb predentine as well as dentine in the same way as osteoclasts resorb bone, and (5) at the end of the resorption, odontoclasts gradually lose their ruffled borders and become detached from the resorbed surface.
在人类乳牙中，破牙细胞性吸收在乳牙脱落前发生于冠部牙本质的牙髓表面，且这种吸收呈现出明显的与时间相关的组织学变化（撒哈拉等人，1992年）。
利用这一现象作为观察系统，我们通过光学显微镜和电子显微镜检查了人类破牙细胞的细胞分化情况。对于破牙细胞分化和功能的组织化学标记物，通过光学显微镜和电子显微镜酶组织化学法测定抗酒石酸酸性磷酸酶（TRAP）活性。
随着牙根吸收接近完成，最初在牙髓腔中检测到TRAP阳性单核细胞。它们的整个细胞质中含有丰富的线粒体、小溶酶体和中度发达的粗面内质网。在这些单核细胞中，TRAP活性定位于生物合成途径的区室，即内质网池和高尔基体板层以及小溶酶体中。TRAP阳性单核细胞首先通过其细长的细胞突起与前期牙本质表面接触。附着后，它们沿前期牙本质表面展开并形成特化的膜结构、透明区和皱褶缘。接下来，它们在前期牙本质表面相互融合并形成典型的多核破牙细胞。在其吸收功能终止后，破牙细胞失去其皱褶缘并从吸收表面脱离。大多数脱离的破牙细胞有许多大的淡染空泡和次级溶酶体，似乎正处于退变过程中。
本研究表明：（1）破牙细胞由TRAP阳性单核细胞分化而来，这些单核细胞可能起源于循环祖细胞；（2）破牙细胞的膜特化，即透明区和皱褶缘的形成，是在它们与吸收表面接触后诱导产生的；（3）破牙细胞的多核化仅在它们附着于吸收表面后发生；（4）成熟的多核破牙细胞能够像破骨细胞吸收骨一样吸收前期牙本质和牙本质；（5）在吸收结束时，破牙细胞逐渐失去其皱褶缘并从吸收表面脱离。
