The diagnosis of muscular dystrophies or the assessment of the
functional benefit of gene or cell therapies can be difficult, especially
for poorly accessible muscles, and it often lacks a singlefiber
resolution. In the present study, we evaluated whether muscle
diseases can be diagnosed from small biopsies using atomic
force microscopy (AFM). AFM was shown to provide a sensitive
and quantitative description of the resistance of normal and dystrophic
myofibers within live muscle tissues explanted from Duchenne
mdx mice. The rescue of dystrophin expression by gene
therapy approaches led to the functional recovery of treated dystrophic
muscle fibers, as probed using AFM and by in situ wholemuscle
strength measurements. Comparison of muscles treated
with viral or non-viral vectors indicated that the efficacy of the
gene transfer approaches could be distinguished with a single
myofiber resolution. This indicated full correction of the resistance
to deformation in nearly all of the muscle fibers treated with an
adeno-associated viral vector that mediates exon-skipping on the
dystrophin mRNA.
Having shown that AFM can provide a quantitative assessment of
the expression of muscle proteins and of the muscular function in
animal models, we assessed myofiber resistance in the context of
human muscular dystrophies and myopathies. Thus, various forms
of human Becker syndrome can also be detected using AFM in blind
studies of small frozen biopsies from human patients.
Interestingly, it also allowed the detection of anomalies in a fraction
of the muscle fibers from patients showing a muscle weakness
that could not be attributed to a known molecular or genetic defect.
Overall, we conclude that AFM may provide a useful method to complement
current diagnosis tools of known and unknown muscular
diseases, in research and in a clinical context.