Embryonic myosin is a regeneration marker to monitor utrophin-based therapies for DMD

Abstract

Duchenne muscular dystrophy (DMD) is a lethal, X-linked muscle-wasting disease caused by lack of the cytoskeletal protein dystrophin. Constitutive utrophin expression, a structural and functional paralogue of dystrophin, can successfully prevent the dystrophic pathology in the dystrophin-deficient mdx mouse model. In dystrophic muscles, utrophin is increased as part of the repair process and localized at the sarcolemma of regenerating myofibers. The presence of developmental myosin such as embryonic myosin (MyHC-emb) and neonatal represents a useful marker of muscle regeneration and a meaningful indicator of muscle damage, which correlates with the clinical severity of milder Becker muscular dystrophy and DMD patients. In the present study, we demonstrate that MyHC-emb is a robust marker of regeneration at different ages and in different skeletal muscles. We also evaluate the correlation between utrophin, dystrophin and MyHC-emb in wild-type (wt) and regenerating dystrophic muscles. Restoration of dystrophin significantly reduced MyHC-emb levels. Similarly, overexpression of utrophin in the transgenic mdx-Fiona mice reduced the number of MyHC-emb positive fibers to wt level, prevented the regenerative process and rescued the muscle function. In contrast, the absence of utrophin in the dystrophin-deficient double-knockout mice resulted in a higher MyHC-emb content and in a more severe dystrophic pathophysiology than in mdx mice. These data illustrate the importance of monitoring utrophin and MyHC-emb levels in the preclinical evaluation of therapies and provide translational support for the use of developmental myosin as a disease biomarker in DMD clinical trials.

Lack of miR-378 attenuates muscular dystrophy in mdx mice

“…Alternatively, eMyHC has been suggested as the robust biomarker of the regeneration process (60). In the latter study, the restoration of dystrophin or utrophin overexpression reduced the level of eMyHC, accompanied by the rescued muscle function of dystrophic mice (60).…”

“…The presence of centronucleated fibers, together with the morphological changes in the size of muscle fibers, has served as the most commonly used indicator of muscle regeneration for years; however, the limitations and variability of this marker were also stressed (35). Alternatively, eMyHC has been suggested as the robust biomarker of the regeneration process (60). In the latter study, the restoration of dystrophin or utrophin overexpression reduced the level of eMyHC, accompanied by the rescued muscle function of dystrophic mice (60).…”

A high–throughput digital script for multiplexed immunofluorescent analysis and quantification of sarcolemmal and sarcomeric proteins in muscular dystrophies

“…Furthermore, the acquisition procedure has been refined and a novel method for background subtraction has been implemented in an attempt to accurately identify all true dystrophin signal present at the sarcolemma. In addition, automated assessment of the levels of myofibre regeneration as assessed by the number of fibres expressing fetal and/or developmental myosin is presented [24,[40][41][42], as it is expected that a robust increased production of sarcolemmal proteins like dystrophin (or utrophin) would be associated with decrease in muscle damage [22,24].…”

Synthesis of SMT022357 enantiomers and in vivo evaluation in a Duchenne muscular dystrophy mouse model

“…3 B). Taking into consideration that force is reduced only by 13.6% in wild type mice and up to 64.2% in mdx mice [ 26 ] (48.8% in the present experiment, Fig. 3 ) it is apparent that both enantiomers (+)- 4 and (−)- 4 significantly improved EDL muscle pathophysiology and ameliorated the DMD phenotype in mdx mice.…”