Histological examination on osteoblastic activities in the alveolar bone of transgenic mice with induced ablation of osteocytes
Minqi Li1,2,3, Tomoka Hasegawa3, Hiromi Hogo3, Sawako Tatsumi4, Zhusheng Liu3, Ying Guo3, Muneteru Sasaki3, Chihiro Tabata3, Tsuneyuki Yamamoto3, Kyoji Ikeda4 and Norio Amizuka3
1Department of Bone Metabolism, School of Stomatology, Shandong University, 2Shandong Provincial Key Laboratory of Oral Biomedicine, Jinan, China 3Department of Developmental Biology of Hard Tissue, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan and 4Department of Bone and Joint Disease, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan.
Offprint requests to: Minqi Li, DDS, PhD, Department of Bone Metabolism, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Biomedicine, Wenhua West Road 44-1, Jinan 250012, China. e-mail: li_min_qi@hotmail.com
Summary. The purpose of this study was to examine histological alterations on osteoblasts from the alveolar bone of transgenic mice with targeted ablation of osteoctyes. Eighteen weeks-old transgenic mice based on the diphtheria toxin (DT) receptor-mediated cell knockout (TRECK) system were used in these experiments. Mice were injected intraperitoneally with 50 µg/kg of DT in PBS, or only PBS as control. Two weeks after injections, mice were subjected to transcardiac perfusion with 4% paraformaldehyde in 0.1M phosphate buffer (pH 7.4), and the available alveolar bone was removed for histochemical analyses. Approximately 75% of osteocytes from alveolar bones became apoptotic after DT administration, and most osteocytic lacunae became empty. Osteoblastic numbers and alkaline phosphatase (ALP) activity were markedly reduced at the endosteum of alveolar bone after DT administration compared with the control. Osteoblastic ALP activity in the periodontal ligament region, on the other hand, hardly showed any differences between the two groups even though numbers were reduced in the experiment group. Silver impregnation showed a difference in the distribution of bone canaliculi between the portions near the endosteum and the periodontal ligament: the former appeared regularly arranged in contrast to the latter’s irregular distribution. Under transmission electron microscopy (TEM), the osteoblasts in the periodontal ligament showed direct contact with the Sharpey’s fibers. Thus, osteoblastic activity was affected by osteocyte ablation in general, but osteoblasts in contact with the periodontal ligament were less affected than endosteal osteoblasts. Histol Histopathol 28, 327-335 (2013)
Key words: Alveolar bone, Osteocyte, Osteoblast, Bone canalicular, Sharpey’s fiber
DOI: 10.14670/HH-28.327