Measurement and estimation of osteocyte mechanical strain

Osteocytes are the most abundant cell type in bone and are responsible for sensing mechanical strain and signaling bone (re)modeling, making them the primary mechanosensors within bone. Under aging and osteoporotic conditions, bone is known to be less responsive to loading (exercise), but it is unclear why. Perhaps, the levels of mechanical strain required to initiate these biological events are not perceived by the osteocytes embedded within the bone tissue. In this review we examine the methods used to measure and estimate the strains experienced by osteocytes in vivo as well as the results of related published experiments. Although the physiological levels of strain experienced by osteocytes in vivo are still under investigation, through computational modeling and laboratory experiments, it has been shown that there is significant amplification of average bone strain at the level of the osteocyte lacunae. It has also been proposed that the material properties of the perilacunar region surrounding the osteocyte can have significant effects of the strain perceived by the embedded osteocyte. These facts have profound implications for studies involving osteoporotic bone where the material properties are known to become stiffer.