Figure 4

In vivo analysis of the effect of PTH on muscle strength.

(a) The mean hang time in the four-limb hanging wire test for the PTH-treated mdx mice (n = 6) was 132 ± 61.6 s. In contrast, the mean hang time for the saline-injected mdx mice (n = 7) was significantly shorter (p = 0.03) at 49.5 ± 44.9 s. (b) Mice were made to run on a treadmill at 25 cm/s for 100 min. All of the C57BL/10 mice (n = 6) ran for 100 min and the mean distance covered was 1486 ± 7.4 m. The PTH-treated mdx (n = 6) mice ran a mean distance of 843.6 ± 352 m, but one did run for 100 min. None of the saline-injected mdx mice (n = 7) ran for 100 min and the mean distance covered was 425 ± 190 m. Both the C57BL/10- and PTH-treated mdx mice ran significantly longer than the saline-injected mdx mice (p < 0.01 and p = 0.03, respectively). (c) Mean mCT value of the fourth lumbar vertebrae of the mice in each group measured to confirm the effect of PTH on bone density. The mean mCT values of the C57BL/10, PTH-treated mdx and saline-injected mdx mice were 1521.871, 1304.34 and 1207.272 Hounsfield units, respectively. (d) Thin sections of the gastrocnemius muscle from the C57BL/10, saline-injected mdx and PTH-treated mdx mice were stained with HE for histological examination. (e) The diameters of myofibers in the tissues from the C57BL/10 (n = 5), saline-injected mdx (n = 7) and PTH-treated mdx (n = 6) mice were 33.62 ± 10.6, 25.41 ± 10.4 and 31.16 ± 12.9 μm, respectively (p < 0.01). (f) The rates of myofibers with central nuclei for the C57BL/10 (n = 5), saline-injected mdx (n = 7) and PTH-treated mdx (n = 6) mice were 0.34% ± 2.0%, 93.2% ± 2.0% and 83.01% ± 4.0%, respectively (p < 0.01). These results show that the histology of myofibers from mdx mice is improved by PTH treatment. B10, C57BL/10; Saline mdx, saline-injected mdx; PTH mdx, PTH-treated mdx.