Aging Bone: Age Effects on Osteocyte Lacunar and Canalicular Microarchitecture

Throughout our lifetime bone is constantly remodeling. Osteocytes are thought to play an important role in the equilibrium of bone remodeling through their complex network of extracellular and intracellular communication. However, with age, our bone becomes less responsive to strain which results in a reduced bone mass and increased risk of fracture. 

Objectives: The purpose of this study was to use quantitative analysis to assess the changes of bones’ microarchitecture that accompany the aging process utilizing scanning electron microscopy (SEM). These data will be used in the creation of more anatomically accurate finite element models to predict strain perceived by young and old osteocytes.

Methods: SEM imaging was used to examine the osteocyte lacuna-canalicular system of young (n=5) and old (n=5) non-human primate femurs.  Images obtained at 300x magnification were collected to assess lacunar density of the samples, while osteocyte lacunar cross sectional area and number of canaliculi per osteocyte lacuna were measured using a magnification of 3000x.  All images were quantitatively examined using ImageJ software. 

Results: A significant increase (Student’s T-test, p<0.05) was observed between the young (n=51) and old (n=52) samples with regard to osteocyte lacunar cross sectional area (119.4±3.3 µm² vs. 131.7±3.9µm²).  The increase in cross sectional area was observed along the minor axis of the osteocyte lacuna.  A significant decrease in lacunar density was observed between samples from young (n=25) and old (n=25) bone (729.3±18.0 lacunae/mm² vs. 603.7±15.2 lacunae/mm²), while, no significant difference was observed between young and old samples in the number of canaliculi per osteocyte (37.1±1.1 vs. 36.8±1.2).  

Conclusions: These results reiterate the microstructural changes of bone that occur with age.  The values found in this study are currently being used to create more anatomically accurate finite element models to estimate changes in osteocyte strain transduction with age.