The Canalicular Structure of Compact Bone in the Rat at Different Ages

Abstract

Osteocytes communicate through a canalicular system that maintains the vitality and mineral metabolism of bone. Casting the vascular canals and canaliculi of compact bone with methacrylate and viewing them with scanning electron microscopy shows their extent and relationships. Confocal laser scanning microscopy of the same specimen before corrosion establishes the degree of calcification of the different tissue components. These methods were used to compare basal with alveolar compact bone in the rat mandible at different ages. Sections of the mandibular molar region were placed in a methacrylate resin. After polymerization and study with confocal microscopy, the organic matrix was removed. Juvenile rats had large irregular central vascular canals and lacunae that were more concentric in the basal than the alveolar bone. Cast lacunae were round, and the canaliculi from these lacunae were short and thick in both bones. Adult rats had regular concentrically arranged lacunae in the basal bone. Cast lacunae were ellipsoid and flatter in the basal bone than in the alveolar bone. The intercommunicating canaliculi were increased and canaliculi had more branching than the juvenile rats. The aged rats had fewer vascular canals, lacunae, and canaliculi and had osteoporotic changes. The cast lacunae were slender and flat especially in the basal bone. The porosity of the mandible became more pronounced in the alveolar than in the basal bone with aging. The canaliculi of mandibular compact bone thinned and developed extensive branching with adulthood but decreased in size and number with advanced age. Lacunae proceed from the large circular structures of youth to the flat forms of the aged. These studies show that the internal structure of compact bone changes with age and mirrors its functional state.

High-resolution 3D imaging of osteocytes and computational modelling in mechanobiology: insights on bone development, ageing, health and disease

“…In the same study, Vashishth and colleagues noted that ageing bone tissue is characterised by increased heterogeneity in the spatial organisation of osteocytes. A 3D study of rat bone at different ages using resin casting of the LCN and subsequent SEM and CLSM demonstrated that the internal structure of compact bone changes with age (Okada et al, 2002). Mandibles of juvenile rats had round lacunae with short, thick canaliculi, while adults had flatter, more ellipsoidal lacunae with more canaliculi, which were branched to a greater extent.…”

“…Studies in rats found that treatment of osteoporotic animals with sclerostin antibody produced marked increases in bone formation, reversing the osteoporotic changes induced by ovariectomy (Li et al, 2009;Ominsky et al, 2014). In contrast to most other therapeutic treatments, which involve anti-resorptive agents and prevent or decelerate further bone loss, sclerostin has the potential to restore lost bone mass and strength.…”

“…Each osteocyte has 50-100 cell processes, that is about one million osteocytes or more per mm 3 of bone tissue. Moreover, the shape and size of the osteocyte and the PCS reflect cell viability (Knothe Tate et al, 2004), while studies of rat bone have found a relationship between age and the number of canaliculi, (Okada et al, 2002). At the same time, the number and orientation of osteocyte cell processes are changed over the lifecourse (Holmbeck et al, 2005), with increased numbers of processes extending towards the vascularity than towards the mineralisation front when the cell is fully developed and enclosed in the mineralised matrix (Knothe Tate et al, 2004).…”

“…Moreover, X-ray micro-computed tomography (µCT) and histology have been used to study skeletal mineralisation in mice (Hafez et al, 2015). Finally, a study of rats at different ages, using acid-etched resin casting and scanning electron microscopy (SEM) to investigate the LCN, showed a developing canalicular system fusing with neighbouring canaliculi and round osteocyte lacunae with short and thick canaliculi (Okada et al, 2002). For acid-etched resin casting, the LCN is filled by a resin and the mineralised bone matrix is etched away by acid so that the relief cast of the LCN can be imaged using SEM after coating with heavy metals .…”

A comparison of the microarchitecture of lower limb long bones between some animal models and humans: a review

“…The Lacuno-canalicular network is the finest network in the cortical bone tissue which orientation and morphology depends on the species, age, anatomical location on the same bone, and arrangement of collagen fibres in the bone matrix and on effects of mechanical loads (Schneider et al 2010). For example, it was found that the density of lacunae was reduced in older rats while the number of canaliculi increased and they became more properly organized (Okada et al 2002). Some data have been reported regarding lacuno-canalicular geometry; we present some of these data below.…”