title: Local applications of myostatin-siRNA with atelocollagen increase skeletal muscle mass and recovery of muscle function.
abstract: BACKGROUND
  Growing evidence suggests that small-interfering RNA (siRNA) can promote gene silencing in mammalian cells without induction of interferon synthesis or nonspecific gene suppression. Recently, a number of highly specific siRNAs targeted against disease-causing or disease-promoting genes have been developed. In this study, we evaluate the effectiveness of atelocollagen (ATCOL)-mediated application of siRNA targeting myostatin (Mst), a negative regulator of skeletal muscle growth, into skeletal muscles of muscular dystrophy model mice.
  
  
  RESULTS
  We injected a nanoparticle complex containing myostatin-siRNA and ATCOL (Mst-siRNA/ATCOL) into the masseter muscles of mutant caveolin-3 transgenic (mCAV-3Tg) mice, an animal model for muscular dystrophy. Scrambled (scr) -siRNA/ATCOL complex was injected into the contralateral muscles as a control. Two weeks after injection, the masseter muscles were dissected for histometric analyses. To investigate changes in masseter muscle activity by local administration of Mst-siRNA/ATCOL complex, mouse masseter electromyography (EMG) was measured throughout the experimental period via telemetry. After local application of the Mst-siRNA/ATCOL complex, masseter muscles were enlarged, while no significant change was observed on the contralateral side. Histological analysis showed that myofibrils of masseter muscles treated with the Mst-siRNA/ATCOL complex were significantly larger than those of the control side. Real-time PCR analysis revealed a significant downregulation of Mst expression in the treated masseters of mCAV-3Tg mice. In addition, expression of myogenic transcription factors was upregulated in the Mst-siRNA-treated masseter muscle, while expression of adipogenic transcription factors was significantly downregulated. EMG results indicate that masseter muscle activity in mCAV-3Tg mice was increased by local administration of the Mst-siRNA/ATCOL complex.
  
  
  CONCLUSIONS
  These data suggest local administration of Mst-siRNA/ATCOL complex could lead to skeletal muscle hypertrophy and recovery of motor disability in mCAV-3Tg mice. Therefore, ATCOL-mediated application of siRNA is a potential tool for therapeutic use in muscular atrophy diseases.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Kawakami
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Kawai
authors.forename: Nao
authors.initials: N
authors.lastname: Kinouchi
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Mori
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ohsawa
authors.forename: Naozumi
authors.initials: N
authors.lastname: Ishimaru
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Sunada
authors.forename: Sumihare
authors.initials: S
authors.lastname: Noji
authors.forename: Eiji
authors.initials: E
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D003094:Collagen / Q000008:administration & dosage* / Q000494:pharmacology; D004576:Electromyography; D008406:Masseter Muscle / Q000033:anatomy & histology* / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D055435:Myostatin / Q000235:genetics*; D009929:Organ Size / Q000187:drug effects*; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics / Q000494:pharmacology
chemical_list: D055435:Myostatin; D034741:RNA, Small Interfering; C059821:atelocollagen; D003094:Collagen