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Increasing mechanical load to 2G in a 1G environment has a negative effect on bone quality of mature male rats
Author(s) -
Lessley Jenny,
Stoecker Barbara J.,
Globus Ruth K.,
Baer Lisa,
Tash Joseph
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.20.5.lb103
Subject(s) - von mises yield criterion , spaceflight , cancellous bone , hypergravity , cortical bone , stiffness , chemistry , biomechanics , biomedical engineering , centrifuge , femur , anatomy , materials science , nuclear medicine , surgery , composite material , structural engineering , medicine , finite element method , physics , astronomy , nuclear physics , engineering
Bone loss due to reduced gravity is a major problem in the spaceflight environment and increased mechanical loading created by artificial gravity is a potential countermeasure. In this study, 24 adult male Fischer 344 rats were randomly assigned to three groups: Vivarium Control (VC) ‐ Fed ad libitum; Stationary Control (SC) ‐ Pair‐Fed to 2G; and 2G Group (2G). Mechanical load was set to 2G by housing animals on a 24‐ft diameter centrifuge at NASA Ames Research Center. Final body weights after 45 days were 346, 325, and 287 g respectively indicating that centrifugation reduced body weight by mechanisms in addition to reduced food intake. Microarchitecture of the isolated distal femur was evaluated with a microCT 40 scanner; one hundred 16.5 micron slices of cancellous bone were contoured as a volume of interest (VOI). Finite element analysis predicted bone strength. Cortical thickness of the femoral midshaft and connectivity density and trabecular number (TbN) of the VOI were reduced and trabecular separation (TbSp) was increased in the SC compared to the VC. Strain, force to compress the VOI, and stiffness were decreased and von Mises stresses increased in SC compared to VC. Bone volume fraction and TbN decreased in 2G compared to SC and TbSp was increased. Strength parameters including force and stiffness tended to decrease (p<0.07) and von Mises stresses tended to increase (p<0.08) in 2G compared to SC. Increasing mechanical load to 2G by continuous centrifugation may be too great a force for optimal bone quality. (Supported by Niblack Scholars Fund, Okla. Agric. Expt. Station and NASA Grant NNA04CC54A).