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In situ measurement of solute transport in the bone lacunar‐canalicular system
Author(s) -
Wang Liyun,
Wang Yilin,
Han Yuefeng,
Henderson Scott,
Majeska Robert,
Weinbaum Sheldon,
Schaffler Mitchell
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a418
Subject(s) - osteocyte , fluorescence recovery after photobleaching , bone canaliculus , chemistry , biophysics , anatomy , bone matrix , diffusion , in situ , tracer , biochemistry , biology , osteoblast , membrane , physics , thermodynamics , cartilage , nuclear physics , in vitro , organic chemistry
Solute transport through the bone lacunar‐canalicular system is essential for osteocyte survival and function, but has proved difficult to measure. We report a novel approach that permits direct measurement of solute movement in intact bones. Using Fluorescence Recovery After Photobleaching, movement of a vitally injected dye (sodium fluorescein) among individual osteocytic lacunae was visualized in situ beneath the periosteum of mouse tibia at depths up to 50 μ m with confocal microscopy. Transport was analyzed using a 2‐compartment mathematical model of solute diffusion that accounted for the characteristic anatomical features of the lacunar‐canalicular system. Diffusion coefficient of fluorescein (376Da) in bone was determined to be 3.3 + 0.6 x10 −6 cm 2 /sec, which is 62% of its diffusion in water. This reduced diffusion is consistent with the presence of an osteocyte pericellular matrix whose structure resembles that proposed for the endothelial glycocalyx [Squire (2001) J Struct Biol 136 ,]. To our knowledge, this is the first study where the dynamics of molecular movement has been measured directly in the bone lacunar‐canalicular system. This in situ imaging approach should also facilitate the analysis of convection‐based transport mechanisms in bones of living animals. This study was supported by grants from NIH & NASA.