Rationale and Objectives
To identify micro–computed tomography (CT) imaging biomarkers for evaluating the effects of emodin, a potential drug to treat osteoporosis, in the mouse model of lipopolysaccharide (LPS)-mediated osteoporosis.
Materials and Methods
Forty male imprinting control region (ICR) mice with LPS-induced bone resorption were equally divided into four experimental groups: phosphate-buffered saline–treated (control), emodin-treated, LPS-treated, and LPS + emodin–treated groups. Emodin (50 mg/kg) was administered orally on alternate days for 8 days, and LPS (5 mg/kg) was injected intraperitoneally on days 1 and 4. After 8 days, the mice were sacrificed, and micro-CT images of the left proximal femurs were obtained. Three-dimensional images were analyzed by using commercial software to measure the bone volume to total volume fraction (BV/TV), trabecular number (Tb-N), trabecular thickness (Tb-Th), and trabecular separation (Tb-Sp) as CT imaging biomarkers. Histologic analyses of the femurs were performed using hematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP) immunohistochemical staining.
Results
The LPS + emodin–treated group demonstrated marked suppression of LPS-induced bone resorption compared to the LPS-treated group (BV/TV, 28.84% vs. 40.76%; Tb-N, 2.65 vs. 3.45 mm −1 ; Tb-Sp, 300.81 vs. 212.31 μm; Tb-Th, 116.94 vs. 131.25 μm). TRAP immunohistochemical analysis showed fewer osteoclasts per field of tissue in the LPS + emodin–treated group than in the LPS-treated group (27.8 vs. 41.8). The BV/TV, Tb-N, and Tb-Sp data correlated well with the histomorphometric findings.
Conclusions
The findings reveal a novel effect of emodin on bone remodeling in the LPS-mediated osteoporotic mouse model. The ex vivo micro-CT imaging is a promising tool for assessing the therapeutic effects of potential drugs on osteoporosis.
Osteoporosis is a bone disorder characterized by bone mass decline and trabecular architecture deterioration, leading to increased bone fragility and risk of spontaneous fracture . An imbalance in bone remodeling, a physiological process characterized by bone formation by osteoblasts and bone resorption by osteoclasts, causes most of the adult skeletal diseases including osteoporosis . The literature includes many studies of bone remodeling to prevent and overcome osteoporosis.
Emodin (3-methyl-1,6,8-trihydroxyanthraquinone) is a natural compound present in the roots and bark of numerous plants of the genus Rhamnus , a herb widely used as a laxative in traditional Chinese medicine . It reportedly has a variety of biological activities, such as anticancer, vasorelaxative, immunosuppressive, anti-inflammatory, and wound-healing properties . The effect of emodin on bone remodeling has been studied in vitro: it was found to have a beneficial effect on bone health with anabolic activity to prevent osteoporosis . However, no study on the pharmacologic role or biologic effects of emodin has been performed in an animal model until now.
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Materials and methods
Mouse Model and Experimental Groups
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Micro-CT System
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Image Analysis
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Histologic Analysis
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Statistical Analysis
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Results
Imaging Findings
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Table 1
Mean (SD) Values of the Bone Parameters Measured by Micro-CT Analysis
Parameter Control Emodin LPS LPS + Emodin_P_ ∗ BV/TV (%) 43.30 (8.41) 40.33 (9.25) 28.84 (3.87) 40.76 (10.16) .000 Tb-N (mm −1 ) 3.74 (0.44) 3.48 (0.62) 2.65 (0.34) 3.45 (0.75) .005 Tb-Sp (μm) 190.40 (27.60) 222.50 (45.44) 300.81 (35.40) 212.31 (53.37) .000 Tb-Th (μm) 124.19 (27.20) 121.60 (27.81) 116.94 (24.13) 131.25 (36.23) .788
BV/TV, bone volume/total volume fraction; CT, computed tomography; LPS, lipopolysaccharide; SD, standard deviation; Tb-N, trabecular number; Tb-Sp, trabecular separation; Tb-Th, trabecular thickness.
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Table 2
Results of the Mann–Whitney Test
Parameter Control versus Emodin Control versus LPS Control versus LPS + Emodin LPS versus LPS + Emodin BV/TV .218 .000 .315 .000 Tb-N .505 .000 .130 .015 Tb-Sp .123 .000 .089 .000
BV/TV, bone volume/total volume fraction; LPS, lipopolysaccharide; Tb-N, trabecular number; Tb-Sp, trabecular separation.
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Histologic Findings
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Discussion
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Acknowledgment
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