title: Key changes in denervated muscles and their impact on regeneration and reinnervation.
abstract: The neuromuscular junction becomes progressively less receptive to regenerating axons if nerve repair is delayed for a long period of time. It is difficult to ascertain the denervated muscle's residual receptivity by time alone. Other sensitive markers that closely correlate with the extent of denervation should be found. After a denervated muscle develops a fibrillation potential, muscle fiber conduction velocity, muscle fiber diameter, muscle wet weight, and maximal isometric force all decrease; remodeling increases neuromuscular junction fragmentation and plantar area, and expression of myogenesis-related genes is initially up-regulated and then down-regulated. All these changes correlate with both the time course and degree of denervation. The nature and time course of these denervation changes in muscle are reviewed from the literature to explore their roles in assessing both the degree of detrimental changes and the potential success of a nerve repair. Fibrillation potential amplitude, muscle fiber conduction velocity, muscle fiber diameter, mRNA expression levels of myogenic regulatory factors and nicotinic acetylcholine receptor could all reflect the severity and length of denervation and the receptiveness of denervated muscle to regenerating axons, which could possibly offer an important clue for surgical choices and predict the outcomes of delayed nerve repair.
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA ; Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China ; Department of Orthopedic Surgery, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wu
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA ; Department of Orthopedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC, USA.
authors.forename: Aditya
authors.initials: A
authors.lastname: Chawla
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Spinner
authors.affiliation: Department of Hand Surgery, Huashan Hospital, Fudan University, Shanghai, China.
authors.forename: Cong
authors.initials: C
authors.lastname: Yu
authors.affiliation: Departments of Orthopedic Surgery and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Yaszemski
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Windebank
authors.affiliation: Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, USA ; Shanghai Key Laboratory of Peripheral Nerve and Microsurgery, Shanghai, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
keywords: denervation; fibrillation potential; gene expression; maximal isometric force; muscle fiber conduction velocity; muscle fiber diameter; nerve regeneration; neural regeneration; neuromuscular junction; reinnervation