A comparison of the bone and growth phenotype of mdx, mdx:Cmah−/− and mdx:Utrn +/− murine models with the C57BL/10 wild-type mouse

Figures

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  Fig. 1.. Muscle characteristics in different muscular dystrophy mouse models. (A) H&E-stained section of tibialis anterior from a 3-week-old: (i) WT mouse showing normal, regular myofibres with peripheral nuclei and intact sarcoplasm; and (ii) mdx, (iii) mdx:Utrn+/− (shown as mdx:utr in the figure) and (iv) mdx:Cmah−/− mouse, showing many inflammatory cells with a barely visible sarcoplasm. (B) H&E-stained section of tibialis anterior from a 7-week-old: (i) WT mouse showing normal, regular myofibres with peripheral nuclei and intact sarcoplasm; and (ii) mdx, (iii) mdx:Utrn+/− and (iv) mdx:Cmah−/− mouse, showing regeneration with larger myofibres and central nuclei. (C) Muscle cell inflammation was present in all muscular dystrophy models by 3 weeks of age followed by regeneration at 5 and 7 weeks of age. (D) Mean grip strength by age and genotype, showing a reduction in muscular dystrophy mice. (E) Higher CK activity in muscular dystrophy mice at all ages. Data are presented as mean±s.d. (n>6); *P<0.05, **P<0.01, ***P<0.001 for cumulative measures of muscle damage compared to WT mice. (F) Increased weight gain is seen in the young mdx:Cmah−/− mice. (Fi) Increased rate of weight gain in…

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  Fig. 2.. Longitudinal bone growth rate in muscular dystrophy mouse models. (A) Longitudinal bone growth during the study period. Data are presented as mean±s.d. *P<0.05 compared to WT mice of the same age. (B) Examples of calcein-labelled GP in a 5-week-old (i) mdx:Cmah−/− and (ii) mdx mouse, showing the increased longitudinal growth rate in the mdx:Cmah−/− mouse (red arrows).

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  Fig. 3.. Bone parameters in muscular dystrophy mouse models. (A) Representative µCT images of tibial bone of all genotypes at 3, 5 and 7 weeks of age to show bone development (upper row, mid diaphyseal cortical bone; lower row, metaphyseal trabecular bone). (B) Compared to similarly aged WT mice, cortical bone fraction was lower in mdx:Cmah−/− mice at 3 weeks of age, but higher in all muscular dystrophy models at 7 weeks of age. (C) Cortical tissue mineral density was higher in mdx:Cmah−/− mice at 3 and 7 weeks of age and in mdx:Utrn+/− (shown as mdx:utr in the figure) mice at 5 weeks when compared to WT mice. (D) Trabecular tissue volume was lower in mdx:Cmah−/− mice at 3 and 7 weeks of age compared with WT. (E) Trabecular connectivity was lower in mdx:Utrn+/− mice at 5 weeks and mdx:Cmah−/− mice at both 5 and 7 weeks when compared to WT mice. (F,G) The number of osteoblasts (F; N.Ob/BS) and osteoclasts (G; N.Oc/BS) per bone surface were normal in all muscular dystrophy models at 5 weeks of age. Data are presented are mean±s.d. (n>6); *P<0.05, **P<0.01, ***P<0.001 compared to WT mice.

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  Fig. 4.. IGF-1 immunohistochemistry in muscular dystrophy mouse models. Immunolocalisation of IGF-1 in sections of (A) WT and (B) mdx:Cmah−/− tibiae, showing greater staining intensity in cells of both ossification centres and the growth plate (GP). (C) Control section in which rabbit IgG was substituted for the primary antibody. (D) Quantification of IGF-1 staining in GP chondrocytes and metaphysis of tibiae from WT and muscular dystrophy mouse models. Data are presented as mean±s.d. (n=6). *P<0.05, **P<0.01 compared to WT mice.

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  Fig. 5.. Bone marrow adiposity in muscular dystrophy mouse models. Three-dimensional µCT reconstructions of 7-week-old osmium-stained tibiae from: (A) WT, (B) mdx and (C) mdx:Cmah−/− mice. Bone appears grey and BMAT is white. (D) The boundaries of rBMAT and cBMAT within the tibia are shown; rBMAT lies proximal to tibia/fibula junction and cBMAT lies distal to tibia/fibula junction (shown by dashed line). (E-G) Percentage of (E) total BMAT, (F) rBMAT, (G) cBMAT. Data are presented as mean±s.d. (n=5). *P<0.05, **P<0.01 compared to WT mice. Ad.V/Ma.V, adipose volume/marrow volume.