Remodelling of intrinsic tongue muscles in a Duchenne muscular dystrophy mouse model: regional differences in fibre size and regeneration.

OBJECTIVES

To assess muscle fibre size, fibre damage, regeneration, and fibrosis in intrinsic longitudinal tongue muscles in a mouse model of Duchenne muscular dystrophy (DMD).

DESIGN

A cross-sectional study was conducted using mdx5Cv dystrophic and wild-type (WT) mice at 3, 6, and 12 months of age (5-7 animals per genotype per time point). Tongue and masseter samples were cryosectioned (10 µm) and stained for analysis. Standardised regions of interest were placed in the superior longitudinal (SL) and inferior longitudinal (IL) tongue muscles. Fibre size was assessed using fibre number and minimum Feret diameter; regeneration by centrally nucleated fibres; fibrosis by Sirius Red staining; and fibre damage by immunoglobulin M (IgM) uptake. The masseter muscle was evaluated as a comparative reference. Differences by genotype (mdx5Cv vs WT) and muscle region (SL vs IL) were analysed using two-way repeated measures ANOVA; data were pooled across ages, as no significant age effects were found.

RESULTS

Genotype and muscle region significantly influenced remodelling in intrinsic tongue muscles. In dystrophic mice, fibres were larger in the IL than the SL muscle (p = 0.002), whereas no regional difference was observed in WT mice. Regeneration was increased in dystrophic tongues and was higher in the IL than the SL muscle (p < 0.001). Collagen deposition differed by muscle region but showed no effects of genotype, and IgM-positive fibres were rare.

CONCLUSIONS

Intrinsic tongue muscles in mice with DMD exhibit structural alterations characterized by compensatory fibre hypertrophy and modest regeneration, with pronounced regional differences between longitudinal muscles.