Gene expression analysis of FSHD muscle with different MRI pattern

Objective: to focus on the molecular mechanisms involved in the dystrophic process that leads to selective wasting of single muscles or muscle groups in Facioscapulohumeral muscular dystrophy (FSHD). By muscle MRI we observed that T2-short tau inversion recovery (T2-STIR) sequences identify two different patterns in which each muscle can be found before the irreversible dystrophic alteration, marked as T1-weighted sequence hyperintensity. We studied these conditions in order to obtain further information on the disease pathogenesis. Design: histopathology, gene expression profiling and real time PCR were performed on muscle biopsies. Subjects: muscles (n=8) with different MRI pattern (T1-weighted normal/T2-STIR normal and T1-weighted normal/T2-STIR hyperintense) from FSHD patients. Data were also compared with inflammatory myopathies (n=7), dysferlinopathies (n=4) and normal controls (n=7). Results: myopathic and inflammatory changes characterize T2-STIR hyperintense FSHD muscles, at variance with T2-STIR normal muscles. These two states can be easily distinguished from each other by their transcriptional profile. Comparison of T2-STIR hyperintense FSHD muscles with muscles of inflammatory myopathies shows peculiar changes, although many alterations are shared among these conditions. Conclusions: at the single muscle level, different stages of the disease correspond to the two MRI patterns. T2-STIR hyperintense FSHD muscles are more similar to inflammatory myopathies than to T2-STIR normal FSHD muscles or other muscular dystrophies, and share with them upregulation of genes involved in innate and adaptive immunity. Our data suggest that selective inflammation, together with perturbation in biological processes such as neoangiogenesis, lipid metabolism and adipokine production, may play a role in FSHD progression. 26 samples of human muscle muscle tissue were analysed using the Illumina beadchip technology.