Although lower bone mass is associated with increased bone fragility, studies conducted during the last grant cycle demonstrated that the mode and magnitude of microdamage formation affects bone's resistance to fracture or 'toughness'. Bones from younger donors are superior in toughness and form diffuse damage as the prominent morphology of microdamage. In contrast, bones from older donors predominantly form linear microcracks that coalesce to cause fracture. The basis of this unique association between damage morphology and toughness is not known. Our preliminary studies show for the first time that diffuse damage in bone initiates in the form of dilatational bands between the fused mineralized aggregates. Dilatational bands stain positive for osteocalcin (OC) and osteopontin (OPN). OC and OPN are present in higher amounts in diffuse damage areas than in controls and the deletion of OC or phosphorylation of bone matrix decreases toughness. Because OPN and OC vary with tissue and donor age, and are intimately associated with each other and with bone mineral where dilatational bands and diffuse damage form, the modification and loss of these non-collagenous matrix proteins may determine the damage morphology and bone's propensity to fracture. Thus the overall goal of this project is to investigate the role of OC and OPN in age-related bone fragility. Bones from human cadavers, aging mouse and transgenic (knock-outs-/- &hetrozygotes) mice including OC-/-, OC, OPN-/- OPN, OPN-OC-/- and OPN-OC and their controls will be subjected to mechanical and immunohistochemical evaluations to investigate whether: (H1): The deletion or modification of OC and or OPN in bone increases bone fragility and bone's propensity to form linear microcracks over diffuse damage;(H2) The age-related increase in bone fragility is associated with the modification and loss of OC and/or OPN that co-localize differently with diffuse damage and linear microcracks. Since OC and OPN levels can be manipulated through hormones and mechanical loading, the evidence of their new direct relationship to damage formation and bone fragility will lead to the development of novel modalities for predicting fracture, as well as strategies for improving bone quality and reducing the fracture risk.
Aging and disease may alter bone matrix and predispose an individual to a higher fracture risk. This project will identify the effects of the modifications and/or loss of two key bone proteins, osteocalcin and osteopontin, on age-related fragility fractures. This new information will lead to the development of novel modalities for predicting fracture, as well as strategies for improving bone quality and reducing the fracture risk.
| Thomas, Corinne J; Cleland, Timothy P; Sroga, Grazyna E et al. (2018) Accumulation of carboxymethyl-lysine (CML) in human cortical bone. Bone 110:128-133 |
| Nikel, Ond?ej; Poundarik, Atharva A; Bailey, Stacyann et al. (2018) Structural role of osteocalcin and osteopontin in energy dissipation in bone. J Biomech 80:45-52 |
| Hull, Robert; Keblinski, Pawel; Lewis, Dan et al. (2018) Stochasticity in materials structure, properties, and processing-A review. Appl Phys Rev 5: |
| Bailey, Stacyann; Karsenty, Gerard; Gundberg, Caren et al. (2017) Osteocalcin and osteopontin influence bone morphology and mechanical properties. Ann N Y Acad Sci 1409:79-84 |
| Thomas, Corinne J; Cleland, Timothy P; Zhang, Sheng et al. (2017) Identification and characterization of glycation adducts on osteocalcin. Anal Biochem 525:46-53 |
| Schmidt, F N; Zimmermann, E A; Campbell, G M et al. (2017) Assessment of collagen quality associated with non-enzymatic cross-links in human bone using Fourier-transform infrared imaging. Bone 97:243-251 |
| Pizzoccaro, Marie-Alix; Nikel, Ondrej; Sene, Saad et al. (2016) Adsorption of benzoxaboroles on hydroxyapatite phases. Acta Biomater 41:342-50 |
| Cleland, Timothy P; Thomas, Corinne J; Gundberg, Caren M et al. (2016) Influence of carboxylation on osteocalcin detection by mass spectrometry. Rapid Commun Mass Spectrom 30:2109-15 |
| Sroga, Gra?yna E; Vashishth, Deepak (2016) A strategy to quantitate global phosphorylation of bone matrix proteins. Anal Biochem 499:85-89 |
| Poundarik, Atharva A; Vashishth, Deepak (2015) Multiscale imaging of bone microdamage. Connect Tissue Res 56:87-98 |
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