| Objective:In present study, the relationship between the osteoporosis and the fractal dimension (FD) of femur and mandible microarchitecture were explored in genetically modified mice, which try to provide an experimental evidence for the fractal analysis in the clinical diagnosis of the mandibular diseases.Methods:Six weeks old homozygous la-hydroxylase (1α (OH) ase-/-) knockout mice, human fibroblast growth factor-23 transgenic mice (FGF23) and 1α (OH) ase-/-FGF23 mice (collectively referred to genetically modified mice, GMM) were used as the model of osteoporosis, and their wild type (WT) littermates were used as control. The femur and the mandible microarchitecture were evaluated by HE staining, Von Kossa staining, histochemistry for total collagen, and tartrate-resistant acid phosphatase (TRAP) staining. The degree of osteoporosis was estimated by X-ray photography, and microCT scanning as well as 3D reconstruction. Besides, the FD on the interest region in X-ray photography or microCT scanning was measured by Image J software, and then the statistical analysis was used to the explore the difference of FD value among the each type GMM, and the relationship between the FD in the femur and mandible microarchitecture from X-ray photography and microCT scanning.Results:(1)Compared with the WT littermates, the bone mineral density (BMD) was reduced in femoral metaphysic, and osteoblasts significantly reduced as well. Besides, the collagen significantly increased and phosphatase decreased in genetically modified mice. Except the reduction of BMD, bone length and volume were observed in the X-ray photography from GMM. The micro-CT scanning and 3D reconstruction showed loose bone structure, reduced cortical thickness and trabecular volume in GMM, especially in 1α (OH) ase-/- mFGF23 mice. Overall, GMM appears severe osteoporosis, which can serve as an excellent osteoporosis animal model. (2) The FD values in X-ray photography of femoral head and metaphyses significantly increased in GMM. However, no significant differences were observed in femoral meduallary cavity. In addition, the FD value of the piphyseal and metaphyseal significantly increased (p<0.05 and p<0.01), and the mandibular ramus as well, while no significant differences among alveolar bone. Besides, the FD value of first molar and second molar from micro-CT significantly increased, while the third molars showed no difference. Consistent with the results of histology, X-ray photography or micro-CT scanning, FD value could be used for the diagnosis of osteoporosis, the metaphyseal femoral and mandibular ramus are more appropriate region of interest. (3) Either femur metaphysis or mandibular ramus, the FD value between X-ray photography and micro-CT scanning presented a good correlation, the correlation coefficient (r) was 0.518 (p= 0.039) and 0.849 (p= 0.001), respectively. Additionally, the r value between the femur metaphysis and mandibular ramus was 0.514 (p= 0.049) in X-ray photography, and it was 0.777 (p= 0.003) in micro-CT scanning. These results suggested that fractal analysis could be used in the analysis of the mandible imaging.Conclusion:Our study demonstrated that GMM were good models of osteoporosis. Either X-rays or microCT, FD values could reflect the status of osteoporosis, and the metaphyseal femoral, mandibular ramus, and alveolar are more suitable region of interest. Moreover, the results from the high correlation of FD value between the mandible and femur suggested that fractal analysis could be used in the evaluation of the mandible imaging, and the optimized method might be expected to an auxiliary tool in the diagnosis of mandibular diseases. |
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