Dynamic acoustic radiation force retains bone structural and mechanical integrity in a functional disuse XXXX model.

@entity174 @entity3145 @entity19 @entity604 @entity170 @entity2331 @entity258
UNASSIGNED: Disuse @entity2331 and @entity604 have been extensively reported in long duration space mission and long term bed rest. The pathology of the @entity604 is similar to @entity170 but highly confined to weight bearing bones. The current anabolic and/or anti-resorptive drugs have systemic effects and are costly over extended time, with concerns of long term @entity174 risk. This study use @entity258 ( @entity258 ) as a non-invasive acoustic force and anabolic stimulus to countermeasure disuse induced @entity604 . Four-month old C57BL/6 @entity19 were randomized into five groups, 1) age-matched (AM), 2) non-suspended sham (NS), 3) non-suspended- @entity258 (NU), 4) suspended sham (SS), and 5) suspended- @entity258 (SU) groups. After four weeks of suspension,  CT analyses showed significant decreases in trabecular bone volume fraction (BV/TV) (-36%, p<0.005), bone @entity3145 ( @entity3145 ) (-3%, p<0.05), trabecular thickness (Tb.Th) (-12.5%, p<0.005), and increase in bone surface/bone volume (+BS/BV) (+16%, p<0.005), relative to age-matched (AM). The application of @entity258 for 20min/day for 5days/week, significantly increased @entity3145 (+3%, p<0.05), Tb.Th (+6%, p<0.05), and decreased BS/BV (-10%, p<0.005), relative to suspension alone (SS) @entity19 . Histomorphometry analyses showed a breakdown of bone microstructure under disuse conditions consist with  CT results. In comparison to SS @entity19 , @entity258 treated bone showed increased structural integrity with increased bone formation rates at metaphysical endosteal and trabecular surfaces (+0.104  0.07 vs 0.031  0.30 m(3)/ m(2)/day) relative to SS. Four-point bending mechanical tests of disused SS femurs showed reduced elastic modulus (-53%, p<0.05), yield (-33%, p<0.05) and ultimate strength (-45%, p<0.05) at the femoral diaphysis relative to AM bone. @entity258 stimulation mitigated the adverse effects of disuse on bone elastic modulus (+42%, p<0.05), yield strength (+29%, p<0.05), and ultimate strength (+39%, p<0.05) relative to SS femurs. @entity258 provides the essential mechanical stimulus to retain bone morphological and mechanical integrity in disuse conditions. This study demonstrates @entity258 potential as regional therapeutic agent to countermeasure disuse induced @entity604 while maintaining bone's integrity.
