Hydroxy group requirement for halofuginone-dependent inhibition of muscle fibrosis and improvement of histopathology in the mdx mouse model for Duchenne muscular dystrophy
Gili Wellner1*, Sharon Mordechay1*, Paul Evans2, Olga Genin3, Mark Pines3 and Orna Halevy1
1Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel, 2Center for Synthesis and Chemical Biology, School of Chemistry, University of College Dublin, Dublin, Ireland and 3Institute of Animal Science, the Volcani Center, Bet Dagan, Israel
* Equal contribution
Offprint requests to: Orna Halevy, Department of Animal Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel. e-mail: orna.halevy@mail.huji.ac.il
Summary. In Duchenne muscular dystrophy (DMD), the progressive loss of muscle and its ability to function is associated with significant fibrosis, representing the major disease complication in patients. Halofuginone, a halogenated analog of the naturally occurring febrifugine, has been shown to prevent fibrosis in various animal models, including those of muscular dystrophies. Here, two optically active enantiomers of deoxyhalofuginone — a halofuginone analogue in which the hydroxy group in position 3 was removed from the piperidinyl entity — were evaluated with respect to their effect on muscle histopathology in mdx mice. Male mdx mice were treated with either deoxyhalofuginone (as single enantiomers or in racemic form), or halofuginone, for 10 weeks, starting at the age of 4 weeks. Halofuginone caused a significant reduction in total collagen content, degenerative areas, as well as in utrophin and phosphorylated-Smad3 levels in the mdx diaphragms. However, neither the deoxyhalofuginone enantiomers, nor its racemic form had any effect on these parameters. A positive effect of the deoxyhalofuginone (+)-enantiomer was observed on myofiber diameters; however, it was lesser than that of halofuginone. It is concluded that the hydroxy group plays a key role in halofuginone's effects related to fibrosis in DMD, and points towards the transforming growth factor β/Smad3 signaling pathway being involved in this inhibition. Elucidation of the structure–function relationship of halofuginone, in relation to inhibiting fibrosis in muscular dystrophies, is of the utmost importance for creating the next generation of anti-fibrotic therapies that will be more efficacious and less toxic, hence improving life quality of patients. Histol Histopathol 34, 791-801 (2019)
Key words: Skeletal muscle, Duchenne muscular dystrophy, Fibrosis, Utrophin, Halofuginone
DOI: 10.14670/HH-18-083