2016 Fiscal Year Annual Research Report
Analysis of the initial mineralization in secondary ossification center by the Life Science and Material Science viewpoints
| Project/Area Number |
16H06990
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| Research Institution | Okayama University |
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Principal Investigator |
ハラ エミリオ・サトシ 岡山大学, 医歯薬学総合研究科, 助教 (40779443)
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| Project Period (FY) |
2016-08-26 – 2018-03-31
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| Keywords | cartilage / secondary ossification / apatite / epiphysis / biomineralization / chondrocyte |
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| Outline of Annual Research Achievements |
We investigated the initial stages of endochondral ossification during secondary ossification of mouse femur epiphysis. We found that the very initial starting point of mineral formation in the epiphysis occurs at post-natal day 6 (P6), by using microCT and histological analysis. Initial minerals were found in the surroundings of hypertrophic chondrocytes in the medial side of the epiphysis. Interestingly, histological and immunohistochemical analyses showed that initial mineralization until P6 was based on chondrocyte activity only, i.e., it occurred in the absence of osteoblasts. Osteoblasts and endothelial cells were observed inside the epiphysis onward P7.
Electron microscopy-based ultrastructural analysis showed that cell-secreted matrix vesicles were absent in the early steps of osteoblast-independent endochondral ossification. Instead, chondrocyte membrane fragments were found in the fibrous matrix surrounding the hypertrophic chondrocytes. EDS analysis and electron diffraction study indicated that cell membrane fragments acted as nuclei for newly formed calcospherites which initially showed an amorphous calcium phosphate phase, and then transformed into apatite crystal phase. These findings would be valuable to develop novel organic-inorganic hybrid materials for manipulation of biomineralization.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The achievements are beyond the expected. The results are very clear, and the applicant has prepared one manuscript with the obtained data on initial mineral formation.
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| Strategy for Future Research Activity |
The applicant plans to investigate the mechanisms of chondrocyte burst associated with mineral formation and expansion. Chondrocyte burst could be involved in space-making for mineral expansion. External factors that affect chondrocyte burst will be analyzed as next steps.
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