Microarchitectural profiling of aging bone with depth

2019-11-19T15:40:45Z (GMT) by Sammie Davies
Bone is a highly adaptive material and is known to change its structure and composition in times of disuse or overuse [1]. 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 [2]. 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 [6]. 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 [10].

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 [11]. 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 [16]. 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.

References:
1. Robling AG., Turner CH. Mechanical signaling for bone modeling and remodeling. Critical reviews in eukaryotic gene expression. 2009; 19(4): 319–338.
2. Cameron KL., Driban JB., Svoboda SJ. Osteoarthritis and the Tactical Athlete: A Systematic Review. Journal of Athletic Training. 2016/04/26. National Athletic Trainers Association; November 2016; 51(11): 952–961. Available at: DOI:10.4085/1062-6050-51.5.03
3. Sheth RD., Wesolowski CA., Jacob JC., Penney S., Hobbs GR., Riggs JE., et al. Effect of carbamazepine and valproate on bone mineral density. The Journal of pediatrics. Elsevier; 1 August 1995; 127(2): 256–262. Available at: DOI:10.1016/s0022-3476(95)70304-7
4. Hansson T., Roos B. Age changes in the bone mineral of the lumbar spine in normal women. Calcified Tissue International. September 1986; 38(5): 249–251. Available at: DOI:10.1007/BF02556602
5. Krølner B., Nielsen SP. Bone Mineral Content of the Lumbar Spine in Normal and Osteoporotic Women: Cross-Sectional and Longitudinal Studies. Clinical Science. 1 March 1982; 62(3): 329–336. Available at: DOI:10.1042/cs0620329
6. Compston JE., McClung MR., Leslie WD. Osteoporosis. The Lancet. 2019; 393(10169): 364–376. Available at: DOI:https://doi.org/10.1016/S0140-6736(18)32112-3
7. Stauber M., Müller R. Age-related changes in trabecular bone microstructures: global and local morphometry. Osteoporosis International. 2006; 17(4): 616–626. Available at: DOI:10.1007/s00198-005-0025-6
8. Nagaraja S., Lin ASP., Guldberg RE. Age-related changes in trabecular bone microdamage initiation. Bone. 2007; 40(4): 973–980. Available at: DOI:https://doi.org/10.1016/j.bone.2006.10.028
9. Ding M., Hvid I. Quantification of age-related changes in the structure model type and trabecular thickness of human tibial cancellous bone. Bone. 2000; 26(3): 291–295. Available at: DOI:https://doi.org/10.1016/S8756-3282(99)00281-1
10. Hildebrand T., Laib A., Müller R., Dequeker J., Rüegsegger P. Direct Three-Dimensional Morphometric Analysis of Human Cancellous Bone: Microstructural Data from Spine, Femur, Iliac Crest, and Calcaneus. Journal of Bone and Mineral Research. 1 July 1999; 14(7): 1167–1174. Available at: DOI:10.1359/jbmr.1999.14.7.1167
11. Consensus development conference: Diagnosis, prophylaxis, and treatment of osteoporosis. The American Journal of Medicine. Elsevier; 1 June 1993; 94(6): 646–650. Available at: DOI:10.1016/0002-9343(93)90218-E
12. Donell S. Subchondral bone remodelling in osteoarthritis. EFORT Open Reviews. June 2019; 4(6): 221–229. Available at: DOI:10.1302/2058-5241.4.180102
13. Li B., Aspden RM. Mechanical and material properties of the subchondral bone plate from the femoral head of patients with osteoarthritis or osteoporosis. Annals of the Rheumatic Diseases. 1 April 1997; 56(4): 247–254. Available at: DOI:10.1136/ard.56.4.247
14. Day JS., Ding M., van der Linden JC., Hvid I., Sumner DR., Weinans H. A decreased subchondral trabecular bone tissue elastic modulus is associated with pre-arthritic cartilage damage. Journal of Orthopaedic Research. September 2001; 19(5): 914–918. Available at: DOI:10.1016/S0736-0266(01)00012-2
15. van der Linden JC., Day JS., Verhaar JAN., Weinans H. Altered tissue properties induce changes in cancellous bone architecture in aging and diseases. Journal of Biomechanics. March 2004; 37(3): 367–374. Available at: DOI:10.1016/S0021-9290(03)00266-5
16. Cameron KL., Hsiao MS., Owens BD., Burks R., Svoboda SJ. Incidence of physician-diagnosed osteoarthritis among active duty United States military service members. Arthritis & Rheumatism. John Wiley & Sons, Ltd; 1 October 2011; 63(10): 2974–2982. Available at: DOI:10.1002/art.30498