Role of osteopontin and osteocalcin in the organic-inorganic interface of bone tissue

Nikel, Ondřej
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Vashishth, Deepak
Mutin, P. Hubert
Laurencin, Danielle
Kotha, Shiva
Boivin, Georges
Cramer, Steven M.
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Biomedical engineering
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Via tissue-level mechanical testing on a genetically modified animal model lacking OC and/or OPN, it was shown that OC and OPN contribute, as individual proteins and as a complex, to energy dissipation during static and cyclic loading. The OC and OPN were also found to be involved in tissue recovery when loading is removed. To verify that changes in recovery and energy dissipation in bone are linked to presence or absence of OC and OPN, and not due to collateral changes in collagen and mineral structure, a robust NMR method was developed to study bone structure at the atomic length scale. A comprehensive set of NMR experiments confirmed that the absence of OC and OPN does not appear to alter the order of collagen or the mineral. Instead, removal of OC and OPN leads to small changes in the organic-mineral interface that imply an increased exposure to hydroxyapatite (HA) mineral for some charged amino acids and for noncollagenous components including glucosaminoglycans and citrate. The results support a model where OC and OPN are present in the extrafibrillar interfaces.
December 2013
School of Engineering
Dept. of Biomedical Engineering
Rensselaer Polytechnic Institute, Troy, NY
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