Osteocyte Shape and Mechanical Loading

Abstract

There is considerable variation in the shape of osteocyte lacunae, which is likely to influence the function of osteocytes as the professional mechanosensors of bone. In this review, we first discussed how mechanical loading could affect the shape of osteocyte lacunae. Recent studies show that osteocyte lacunae are aligned to collagen. Since collagen fiber orientation is affected by loading mode, this alignment may help to understand how mechanical loading shapes the osteocyte lacuna. Secondly, we discussed how the shape of osteocytes could influence their mechanosensation. In vitro, round osteocytes are more mechanosensitive than flat osteocytes. Altered lacunar morphology has been associated with bone pathology. It is important to know whether osteocyte shape is part of the etiology.

Three-dimensional characterisation of osteocyte volumes at multiple scales, and its relationship with bone biology and genome evolution in ray-finned fishes

“…We show, for the first time both in 3D and in actinopterygians, that osteocyte lacunae vary in volume as much as they vary in shape and orientation among bone deposition patterns . This is consistent with observations in other literature based on fossil and extant tetrapods (Baud, 1976;Marotti, 1979Marotti, , 1981de Ricqlès et al, 1991;Kerschnitzki et al, 2011;Cadena & Schweitzer, 2012;Sanchez et al, 2014Sanchez et al, , 2016van Oers et al, 2015). Notably, osteocytes in the woven bone of the actinopterygians studied here are very large.…”

“…In tetrapods, variation in osteocyte shapes and orientation results from changes in the extracellular collagen-fibre mesh (Marotti, 1979;Hernandez et al, 2004;Kerschnitzki et al, 2011;van Oers et al, 2015;Warshaw et al, 2017). This can be the consequence of different bone growth rates (Padian et al, 2001;Warshaw et al, 2017).…”

“…From when they become enclosed within this mineralised tissue they are labelled as osteocytes, contained within interconnected voids called osteocyte lacunae. As such, lacunae provide a hard-tissue record of the osteocyte morphology (Franz-Odendaal et al, 2006;Bonewald, 2011;Webster et al, 2013), which varies according to that of the extracellular collagen matrix deposited during bone growth and remodelling (Amprino, 1947;Marotti, 1979;de Ricqlès et al, 1991;Kerschnitzki et al, 2011;van Oers et al, 2015). Therefore, the morphology of osteocyte lacunae has relevance to the study of bone development and osteocyte function among other topics.…”

Retention of osteocytic micromorphology by sclerostin antibody in a concurrent ovariectomy and functional disuse model

“…Although further study is still required to fully characterize the relationship of osteocytes' morphological change and their functions, there is no doubt that the change is associated with osteoporosis since the sensing of and the sensitivity to strain and fluid flow inputs to the osteocyte are altered with variations in osteocyte morphology. 67 Scl-Ab treatment significantly decreases LASAR in the HLS alone and OVX alone groups such that it is lower in these two groups than the age-matched control, while Scl-Ab treatment in the HLS + OVX group only slightly decreased LASAR. Contrary to the seemingly more consistent change in LASAR across the groups, osteocyte volume change following Scl-Ab treatment is divergent, with the HLS group increasing while the OVX group decreases significantly and the HLS + OVX group remains stable compared with the respective controls.…”

Design, fabrication and characterization of a pure uniaxial microloading system for biologic testing

“…For example, cell differentiation, migration and signal transduction are influenced by mechanical loading [2–3]. Mechanical forces are particularly critical to bone cells, and it is known that mechanical forces at least in part, regulate bone remodeling [4–6]. Given that the mechanisms and pathways by which bone cells coordinate activity in response to normal loading have yet to be elucidated, research aimed at understanding the role of load in bone disease (eg, osteoporosis), overload and disuse must first focus on understanding the role physiologic loading plays in bone adaptation.…”