Bioindicators of the nanoscale structural quality of bone were investigated using ion milling and transmission electron microscopy of osteoporotic bone from human female donors. / Bone is a complex hierarchical biomaterial constantly undergoing remodeling events initiated by cell signaling and fulfilled by migratory bone cells. In osteoporosis, a multitude of signaling factors cause bone resorption to proceed quicker than bone reformation, resulting in a lower bone mineral density (BMD) and porosity as seen by thinning of the cortex and trabeculae. However, the structural motifs of these altered regions of the skeleton have not been understood on the nanoscale. In this thesis, transmission electron microscopy (TEM) was used with an image analysis technique termed nanomorphometry, developed to enable the measurement of nanoscale structural features in human bone. Several nanoscale bone quality bioindicators relevant to the collagen fibrils and bone mineral (mineral lamellae, ML) components were defined and tested (collagen fibril diameter, interfibrillar spacing, ML thickness & ML stack thickness) among two donor cohorts of post-menopausal osteoporotic female patients and age- and sex-matched controls. In one cohort, the anatomical region investigated was the intertrochanteric crest of the femur, while in the second, the femoral neck was studied. The bone sections were prepared using an ion milling workflow yielding electron-transparent views of the bone ultrastructure. Blinded image analysis of the ultrastructure revealed that in both cohorts, the thickness of the MLs was significantly larger in osteoporotic samples versus their controls. In the former cohort, it was found that anti-resorptive drug use in the treated group did not return the ML thickness back to control levels. In the latter cohort, the ML thickness correlated more closely with the proximal femur bone mineral density (BMD) than the age of the patient. These findings suggest that the morphology of the nanoscale mineral phase is affected by osteoporosis, an effect indirectly observed by other techniques, and warrants further exploration into the implications of this effect on bone quality, fragility and strength. / Thesis / Master of Applied Science (MASc) / Human bone is a biomaterial with many levels of organization from the macroscale down to the nanoscale. The material consists of roughly 30 weight % organic components (collagen, non-collagenous proteins) and 67 weight % inorganic components (calcium phosphate minerals) deposited by bone cells. Osteoporosis is a bone disease commonly associated with increased bone porosity and bone fragility. In this study, the effect of osteoporosis on the nanoscale structure of bone was directly imaged and investigated using transmission electron microscopy (TEM). Two advanced ion milling techniques (broad beam and focused ion beam) were used to thin the bone specimens for TEM. Bioindicators relating to the structure and size of collagen and mineral components in osteoporotic versus control bone were quantified in an unbiased image analysis workflow. Findings indicated an increase in the thickness of poly-crystalline bone mineral lamellae in the nanoscale structure of human osteoporotic bone from two human donor cohorts.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24981 |
| Date | January 2019 |
| Creators | Strakhov, Ivan |
| Contributors | Grandfield, Kathryn, Schwarcz, Henry P., Biomedical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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