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Effects of Microgravity on the Creep Behavior of Murine Intervertebral Discs
Author(s) -
Bailey Jeannie F.,
Cheng Kevin K.,
Hargens Alan R.,
Masuda Koichi,
Lotz Jeffrey C.
Publication year - 2011
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.25.1_supplement.668.1
Subject(s) - creep , intervertebral disc , strain (injury) , anatomy , biomechanics , swelling , materials science , displacement (psychology) , biomedical engineering , chemistry , medicine , composite material , psychology , psychotherapist
Objective The purpose of this study was to analyze the effects of microgravity on intervertebral discs. Methods Eight C57BL/6 mice (16‐weeks old) were divided into two groups: 1) exposed to microgravity conditions during a 15‐day NASA mission, STS‐131; and 2) ground‐based controls. After animal sacrifice, the caudal intervertebral discs were first imaged by x‐ray to calculate disc height and cross‐sectional area. Then the C7/C8 motion segments were harvested for biomechanical testing. Discs were subjected to five cycles of compressive creep loading at 0.5 MPa for 20 min with 40 min recovery. The displacement vs. time data were fit to a fluid transport model to calculate tissue permeability (K), time‐dependence of annular strain (G), and strain‐dependence of nucleus swelling pressure (D). Results We observed that flight discs were 32% shorter (p=0.012) and had a 70% decrease in D (p=0.02) compared to controls. D was moderately correlated with disc height (R 2 =0.56, p=0.0013). No statistically‐significant differences were observed for K and G. Conclusion These differences in D and height are comparable with historical data for mouse caudal discs degenerated by static compressive loading. Consequently, our data suggest that 15‐days of microgravity induce intervertebral disc degeneration. Research supported by NASA grant NNX09AP11G.