2000 Fiscal Year Final Research Report Summary
Collagen Degradation and Remodeling at the Alveolar Bone-Ligament Interface.
| Project/Area Number |
11671807
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Morphological basic dentistry
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| Research Institution | Health Science University of Hokkaido |
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Principal Investigator |
YAJIMA Toshihiko Health Science University of Hokkaido, School of Dentistry, Professor, 歯学部, 教授 (10018749)
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| Co-Investigator(Kenkyū-buntansha) |
EICHI Tsuruga Health Science University of Hokkaido, School of Dentistry, Assistant Professor, 歯学部, 助手 (30295901)
IRIE Kazuharu Health Science University of Hokkaido, School of Dentistry, Associate Professor, 歯学部, 講師 (70223352)
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| Project Period (FY) |
1999 – 2000
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| Keywords | alveolar bone / osteoblast / collagen phagocytosis / osteocytes / acid phosphatase / tartrate-resistant acid phosphatase / periodontium / bone remodeling |
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| Research Abstract |
The collagen-phagocytosing activity of osteoblasts at the alveolar bone-ligament interface of rat mandibular first molars was investigated both histologically and histochemically. Alveolar bones of male Wister rats were used in this study. Collagen-containing phagosomes appeared in cuboidal osteoblasts aligned on the bone surface. The 5.7% of the osteoblasts exhibiting alkaline phosphatase activity revealed collagen-containing phagosomes. In addition, acid phosphatase activity and immunocytochemical distribution of cathepsin B were found in these collagen-containing phagosomes at similar locations. The presence of both enzymes in the phagosomes suggests that an intracellular degradation of collagen occurs. Therefore, in addition to the osteoblastic functions of synthesizing and secreting bone matrices, osteoblasts are also capable of phagocytosis and the intracellular disintegration of collagen. Our findings suggest that osteoblasts at the alveolar bone-periodontal ligament interface h
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ave a collagen-phagocytosing ability and play an important role in the physiological remodeling and metabolic breakdown of collagen fibrils of periodontal ligament without osteoclastic bone remodeling.
Based on their ultrastructural features, osteocytes have been classified into formative-, resorptive-, and degenerative-phase. However, the mechanism of the morphological changes from formative osteocytes to resorptive osteocytes is still unclear. Therefore, we examined the histochemical changes in osteocytes from two distinct areas in the mandibles, focusing on the relationship between osteocytes and osteoclastic bone resorption. Tartrate-resistant acid phosphatase (TRAP) activity was detected only in osteocytes located near sites of osteoclastic bone resorption. Osteocytes far from osteoclasts lacked TRAP activity, even those that had been enclosed in bone matrix as long as the osteocytes that did show TRAP activity. Furthermore, glycogen granules in osteocytes disappeared when the cell acquired TRAP activity. These findings suggest that the acquisition of TRAP activity in an osteocytes is closely synchronized with bone resorption. Disappearance of glycogen in osteocytes in the same area may also be related to the acquisition of TRAP activity or bone resorbing activity. The osteocytes characterized by glycogen accumulation must be in the phase that follows the formative phase, in which osteocytes display neither formation nor resorption activity. Less
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