Microarchitectural profiling of aging bone with depth
posterposted on 19.11.2019, 15:40 by Sammie DaviesSammie Davies
Bone is a highly adaptive material and is known to change its structure and composition in times of disuse or overuse . These periods can determine the microarchitecture of bone. This is evident when comparing the skeletal system of those considered “normal” and those coined “tactical athletes” such as military, firefighters and law enforcement . However, occupation is not the only factor that can determine the structure and composition of bone. There are age-related changes that also occur. One example of this is the variability of bone mineral density (BMD) with age. It is known that BMD peaks at 20 years old, plateaus and then declines at 40 years old [3–5]. This reduction is believed to be a result of supressed bone remodelling rates . Alongside BMD, the trabecular structure of bone also changes with age. Trabeculae become thinner or are lost and porosity increases [7–9]. This can lead to a decrease in bone strength .
This may explain why many skeletal diseases are age correlated, such as osteoporosis (OP) and osteoarthritis (OA). A low BMD alongside the increased porosity seen in OP can lead to increased fragility and risk of fracture . Bone mineralisation is also affected in OA, believed to occur due to overloading and resultant hypomineralisation [12–15]. This overloading is thought to explain why the risk of developing OA is significantly higher in these “tactical athletes” described above . Many studies that have observed the age-related changes to bone considered their samples globally. However, it should be taken into consideration the depth at which these changes occur. Depth related changes propose that there is a factor, extrinsic to the bone, such as loading or abnormal joint tissue, that is determining its structure. By looking at the depth of these changes, this may suggest the extent of this factor’s influence.
In the current study, we aimed to offer a microarchitectural depth profile of bone of various ages at a resolution of 2mm. Here, we could investigate the relationship between bone matrix mineralisation, trabecular bone microstructure and aging at differing depths. For this purpose, we determined bone matrix mineralisation (TMD), bone morphometry and bone volume fraction (BV/TV) using micro-CT at different depths in human femoral head cores of varying ages. These cores were harvested from donors from the Melbourne Femur Collection. We aimed to evaluate whether differences in trabecular microstructure could be explained by bone adaptation in age in response to changes in the bone matrix mineralisation and determine the depth to which these changes occur.
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