Tsuchiya Masahiro, Akiba Yosuke, Takahashi Ichiro, Sasano Yasuyuki, Kashiwazaki Jun, Tsuchiya Shinobu, Watanabe Makoto
Division of Aging and Geriatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Arch Histol Cytol. 2008 Sep;71(2):89-100. doi: 10.1679/aohc.71.89.
Root resorption lacunae are principally formed by odontoclasts. While these cells develop from the same origin as osteoclasts, odontoclasts normally have fewer nuclei and a less clear zone compared with osteoclasts. We therefore, hypothesized that odontoclasts possess less differentiation in matrix resorption characteristics than osteoclasts. To test our hypothesis, we compared the TRAP-positive area and the expression patterns of two important proteolytic enzymes, cathepsin K and matrix metalloproteinase-9 (MMP-9), between odontoclasts and osteoclasts. We focused on physiological root resorption in the rat molar, which is a useful experimental model for estimating odontoclasts and osteoclasts. Observations showed the number of nuclei and the TRAP-positive area of odontoclasts to be significantly less compared with osteoclasts. Using in situ hybridization and double labeling fluorescence in situ hybridization showed the majority of odontoclasts to express both cathepsin K and MMP-9, especially 4 and 5 weeks of age, when physiological root resorption occurs actively. Moreover, putative precursor cells of odontoclasts, which typically appeared in the middle of the periodontal ligament at 3 weeks of age, expressed both enzymes. In contrast, the majority of matured osteoclasts expressed only cathepsin K but not MMP-9. We suggest that odontoclasts are comparable to osteoclasts with less differentiation with regard to the expression of proteolytic enzymes.
牙根吸收陷窝主要由破牙细胞形成。虽然这些细胞与破骨细胞起源相同，但与破骨细胞相比，破牙细胞通常细胞核较少且清亮区不明显。因此，我们推测破牙细胞在基质吸收特性方面的分化程度低于破骨细胞。为了验证我们的假设，我们比较了破牙细胞和破骨细胞之间的抗酒石酸酸性磷酸酶（TRAP）阳性面积以及两种重要蛋白水解酶组织蛋白酶K和基质金属蛋白酶-9（MMP-9）的表达模式。我们重点研究了大鼠磨牙的生理性牙根吸收，这是评估破牙细胞和破骨细胞的一个有用的实验模型。观察结果显示，与破骨细胞相比，破牙细胞的细胞核数量和TRAP阳性面积明显更少。使用原位杂交和双标记荧光原位杂交显示，大多数破牙细胞表达组织蛋白酶K和MMP-9，尤其是在4周和5周龄时，此时生理性牙根吸收活跃发生。此外，破牙细胞的假定前体细胞通常在3周龄时出现在牙周膜中部，也表达这两种酶。相比之下，大多数成熟破骨细胞仅表达组织蛋白酶K而不表达MMP-9。我们认为，就蛋白水解酶的表达而言，破牙细胞与分化程度较低的破骨细胞相当。
