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Small oscillatory accelerations, independent of matrix deformations, increase osteoblast activity and enhance bone morphology.

Garman R, Rubin C, Judex S - PLoS ONE (2007)

Bottom Line: Oscillatory accelerations, applied in the absence of weight bearing, resulted in 70% greater bone formation rates in the trabeculae of the metaphysis, but similar levels of bone resorption, when compared to contralateral controls.Quantity and quality of trabecular bone also improved as a result of the acceleration stimulus, as evidenced by a significantly greater bone volume fraction (17%) and connectivity density (33%), and significantly smaller trabecular spacing (-6%) and structural model index (-11%).In retrospect, acceleration, as opposed to direct mechanical distortion, represents a more generic and safe, and perhaps more fundamental means of transducing physical challenges to the cells and tissues of an organism.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
A range of tissues have the capacity to adapt to mechanical challenges, an attribute presumed to be regulated through deformation of the cell and/or surrounding matrix. In contrast, it is shown here that extremely small oscillatory accelerations, applied as unconstrained motion and inducing negligible deformation, serve as an anabolic stimulus to osteoblasts in vivo. Habitual background loading was removed from the tibiae of 18 female adult mice by hindlimb-unloading. For 20 min/d, 5 d/wk, the left tibia of each mouse was subjected to oscillatory 0.6 g accelerations at 45 Hz while the right tibia served as control. Sham-loaded (n = 9) and normal age-matched control (n = 18) mice provided additional comparisons. Oscillatory accelerations, applied in the absence of weight bearing, resulted in 70% greater bone formation rates in the trabeculae of the metaphysis, but similar levels of bone resorption, when compared to contralateral controls. Quantity and quality of trabecular bone also improved as a result of the acceleration stimulus, as evidenced by a significantly greater bone volume fraction (17%) and connectivity density (33%), and significantly smaller trabecular spacing (-6%) and structural model index (-11%). These in vivo data indicate that mechanosensory elements of resident bone cell populations can perceive and respond to acceleratory signals, and point to an efficient means of introducing intense physical signals into a biologic system without putting the matrix at risk of overloading. In retrospect, acceleration, as opposed to direct mechanical distortion, represents a more generic and safe, and perhaps more fundamental means of transducing physical challenges to the cells and tissues of an organism.

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Mean (+SE) bone volume fraction (BV/TV), connectivity density (Conn.D), structural model index (SMI), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) of control (CTR) and accelerated tibiae (ACC).Values are expressed as a percentage of their normal weight-bearing age-matched controls. *: p<0.05 between CTR and ACC.
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pone-0000653-g003: Mean (+SE) bone volume fraction (BV/TV), connectivity density (Conn.D), structural model index (SMI), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) of control (CTR) and accelerated tibiae (ACC).Values are expressed as a percentage of their normal weight-bearing age-matched controls. *: p<0.05 between CTR and ACC.

Mentions: Trabecular bone morphology and micro-architecture were also sensitive to the application of low-amplitude, high-frequency oscillatory accelerations (Fig. 2). Metaphyseal bone volume fraction (17%, p = 0.003), connectivity density (33%, p = 0.004), and trabecular number (5%, p = 0.04) were greater in accelerated bones while the structural model index and trabecular separation were 11% (p = 0.01) and 5% (p = 0.04) less (Fig. 3). In contrast to the beneficial response measured in trabecular bone, no effects of oscillatory accelerations were seen at 3 wk in the cortical bone of the mid-diaphysis (Table 2).


Small oscillatory accelerations, independent of matrix deformations, increase osteoblast activity and enhance bone morphology.

Garman R, Rubin C, Judex S - PLoS ONE (2007)

Mean (+SE) bone volume fraction (BV/TV), connectivity density (Conn.D), structural model index (SMI), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) of control (CTR) and accelerated tibiae (ACC).Values are expressed as a percentage of their normal weight-bearing age-matched controls. *: p<0.05 between CTR and ACC.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1919432&req=5

pone-0000653-g003: Mean (+SE) bone volume fraction (BV/TV), connectivity density (Conn.D), structural model index (SMI), trabecular number (Tb.N), trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp) of control (CTR) and accelerated tibiae (ACC).Values are expressed as a percentage of their normal weight-bearing age-matched controls. *: p<0.05 between CTR and ACC.
Mentions: Trabecular bone morphology and micro-architecture were also sensitive to the application of low-amplitude, high-frequency oscillatory accelerations (Fig. 2). Metaphyseal bone volume fraction (17%, p = 0.003), connectivity density (33%, p = 0.004), and trabecular number (5%, p = 0.04) were greater in accelerated bones while the structural model index and trabecular separation were 11% (p = 0.01) and 5% (p = 0.04) less (Fig. 3). In contrast to the beneficial response measured in trabecular bone, no effects of oscillatory accelerations were seen at 3 wk in the cortical bone of the mid-diaphysis (Table 2).

Bottom Line: Oscillatory accelerations, applied in the absence of weight bearing, resulted in 70% greater bone formation rates in the trabeculae of the metaphysis, but similar levels of bone resorption, when compared to contralateral controls.Quantity and quality of trabecular bone also improved as a result of the acceleration stimulus, as evidenced by a significantly greater bone volume fraction (17%) and connectivity density (33%), and significantly smaller trabecular spacing (-6%) and structural model index (-11%).In retrospect, acceleration, as opposed to direct mechanical distortion, represents a more generic and safe, and perhaps more fundamental means of transducing physical challenges to the cells and tissues of an organism.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
A range of tissues have the capacity to adapt to mechanical challenges, an attribute presumed to be regulated through deformation of the cell and/or surrounding matrix. In contrast, it is shown here that extremely small oscillatory accelerations, applied as unconstrained motion and inducing negligible deformation, serve as an anabolic stimulus to osteoblasts in vivo. Habitual background loading was removed from the tibiae of 18 female adult mice by hindlimb-unloading. For 20 min/d, 5 d/wk, the left tibia of each mouse was subjected to oscillatory 0.6 g accelerations at 45 Hz while the right tibia served as control. Sham-loaded (n = 9) and normal age-matched control (n = 18) mice provided additional comparisons. Oscillatory accelerations, applied in the absence of weight bearing, resulted in 70% greater bone formation rates in the trabeculae of the metaphysis, but similar levels of bone resorption, when compared to contralateral controls. Quantity and quality of trabecular bone also improved as a result of the acceleration stimulus, as evidenced by a significantly greater bone volume fraction (17%) and connectivity density (33%), and significantly smaller trabecular spacing (-6%) and structural model index (-11%). These in vivo data indicate that mechanosensory elements of resident bone cell populations can perceive and respond to acceleratory signals, and point to an efficient means of introducing intense physical signals into a biologic system without putting the matrix at risk of overloading. In retrospect, acceleration, as opposed to direct mechanical distortion, represents a more generic and safe, and perhaps more fundamental means of transducing physical challenges to the cells and tissues of an organism.

Show MeSH
Related in: MedlinePlus