Osteocyte Lacunae and Canaliculi in Cortical and Trabecular Bones

INTRODUCTION: Osteocytes, the most abundant cells in mature bone, are strategically placed to regulate the homeostasis and mechanical adaptation of bone [1]. Interstitial fluid flow and solute transport have been hypothesized to be involved in osteocyte metabolism and mechanosensition [2]. Recent experimental and theoretical studies have shown that the anatomical features of the lacunar-canalicular system (LCS), the fluid pathway in bone, are determining factors of the magnitude of fluid flow and cellular stimulation [3, 4]. Using a newly developed fluorescence recovery after photobleaching (FRAP) approach, we have measured fluid flow and solute transport in the cortex of long bone [4, 5, 6]. However, for trabecular bone, there are few studies on load-induced fluid flow or solute transport. In theory, single trabecula are of the same dimension (200 μm) as the osteons in cortical bone, thus convective transport is also critical for the most inner cells of trabecular bone. To quantify transport characteristics of trabecular bone, the anatomy of the osteocyte LCS has to be determined as previously done for cortical bone [7]. The objective of this study was to characterize osteocyte LCS anatomical features relevant to fluid transport using confocal imaging.