Effect of underwater low intensity pulsed ultrasound on early biochemical markers of bone metabolism in aged mice

Abstract:

Objective：To preliminarily explore the feasibility of underwater low intensity pulsed ultrasound（LIPUS） device，and to study its effect on early biochemical markers of bone metabolism in aged mice. Methods：A total of 44 female C57BL6 mice were randomly divided into sham control group and ultrasound group（both groups were divided into 12-14 month subgroup and 20-23 month subgroup）. An underwater LIPUS device was constructed and used for irradiation in the corresponding groups. A theoretical simulation of the underwater LIPUS device was carried out using COMSOL 5.3 software，and a sound pressure distribution map was drawn. Orbital blood samples were collected from the mice and tested for serum levels of calcium（Ca） and phosphorus（P） using an automatic biochemical analyzer；the levels of bone alkaline phosphatase（BALP） and β isomer of C-terminal telopeptide of type I col－lagen（β-CTX） were determined by enzyme-linked immunosorbent assay. Results：The underwater LIPUS was able to penetrate the cortical bone with sound pressure distributed into the medullary cavity. Compared with the mice aged 12 to 14 months，the mice aged 20 to 23 months had no significantly different serum levels of Ca，P，and β-CTX（P=0.611，0.660，and 0.855，respectively），but had a significantly reduced BALP level（4.35±1.87 vs. 2.24±0.70，P=0.002）. Compared with the sham control group，the ultrasound group had a significantly reduced serum Ca level（12-14 month subgroup：9.59±0.30 vs. 8.42±0.29，P=0.000；20-23 month subgroup：9.82±0.32 vs. 8.86±0.64；P=0.000），a significantly increased serum P level（12-14 month subgroup：8.99±0.76 vs. 10.33±1.09，P=0.014；20-23 month subgroup：8.49±0.72 vs 10.17±1.17，P=0.002），a significantly increased expression level of BALP（12-14 month subgroup：4.35±1.84 vs. 6.17±1.09，P=0.006；20-23 month group：2.24±0.70 vs. 5.05±0.94，P=0.000），and a significantly decreased expression level of β-CTX（only in the 20-23 month subgroup：189.1±57.94 vs. 114.8±19.72，P=0.047）. Conclusion：It is feasible to construct an underwater LUPUS device，and it can effectively improve the early biochemical markers of bone metabolism in aged C57BL6 mice.