Objective To investigate the effect of diabetic model mice combined with cadmium exposure on tibia by Micro-CT imaging.
Methods Forty SPF eight-week-old male C57BL6 mice were randomly divided into four groups:control group, cadmium chloride group, diabetes mellitus model group, and diabetes mellitus model combined with cadmium chloride group (combined exposure group). The cadmium chloride group was intraperitoneally injected with 3.5 mg/kg cadmium chloride 3 times per week for 4 weeks. The diabetes mellitus model was intraperitoneally injected with 40 mg/kg streptozotocin 5 days per week and detected for fasting plasma glucose after 1-2 weeks, and fasting plasma glucose ≥ 11.1 mmol/L indicated that the model was established. The diabetes mellitus model group was treated with cadmium chloride as previously described to establish a combined exposure group. The control group was intraperitoneally injected with normal saline at the same volume. After the treatment protocol, bone wet weight/body weight and bone length were measured after soft tissues were stripped from bone; right tibia of the mice was scanned by Micro-CT for three-dimensional reconstruction, and the measurements included bone mineral density, bone volume fraction, bone surface/bone volume, trabecular thickness, trabecular number, and trabecular separation.
Results No differences in bone wet weight per 100 g body weight and bone length were found among the four groups (P > 0.05). The morphological observation results showed that, compared with the control group, the other three groups had decreased trabecular number and trabecular thickness together with loose structure, and compared with the diabetes mellitus model group, the combined exposure group had more obvious such changes. Compared with the control group(0.160±0.029) g/cm3, (14.781±4.754)%, (13.397±2.962) mm-1, (2.964±0.777) mm-1, and (0.118±0.013) mm, the bone mineral density, bone volume fraction, bone surface/bone volume, and trabecular number were decreased while trabecular separation of tibial cancellous bone were increased in the cadmium chloride group(0.123±0.013) g/cm3, (7.972±2.404)%, (8.533±2.221) mm-1, (1.787±0.513) mm-1, and (0.147±0.015) mm and the combined exposure group(0.121±0.008) g/cm3, (8.571±1.710)%, (8.902±1.065) mm-1, (1.840±0.280) mm-1, and (0.154±0.008) mm (Ps < 0.05); compared with the diabetes mellitus model group, all the above indicators were significanthy different in the combined exposure group (Ps < 0.05). However, there was no difference in the bone mineral density of tibial cortical bone among the four groups (P > 0.05). Compared with the control group(5.973±0.418) mm-1, the diabetes mellitus model(6.876±0.469) mm-1 and the combined exposure group(7.568±0.595) mm-1 showed increased bone surface/bone volume of tibial cortical bone (P < 0.05); compared with the cadmium chloride group(32.765±4.053)% and (6.038±0.579)mm-1, the combined exposure group(39.901±3.386)% and (7.568±0.595)mm-1 showed increased bone volume fraction and bone surface/bone volume of tibial cortical bone (P < 0.05).
Conclusion Cadmium exposure could reduce bone volume fraction, bone surface/bone volume, trabecular number, and bone mineral density, and increase trabecular separation of tibial cancellous bone of diabetic mice, indicating osteoporosis of tibial cancellous bone.
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