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Aberrant expression of myogenin in inclusion body myositis: Immunohistochemical studies of transcription factors regulating myogenesis in inflammatory myopathies
Author(s) -
Kubota Akatsuki,
Shimizu Jun,
Iwata Atsushi,
Tsuji Shoji
Publication year - 2012
Publication title -
clinical and experimental neuroimmunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 15
ISSN - 1759-1961
DOI - 10.1111/cen3.12000
Subject(s) - myogenin , inclusion body myositis , myogenesis , immunohistochemistry , pathology , biology , myositis , myocyte , medicine , endocrinology
Abstract Objectives We aimed to assess the immunohistochemistry of transcription factors that regulate myogenesis ( P ax7, M yo D 1, and myogenin) in inflammatory myopathies in relation to histopathological severity, and to determine whether there are some differences in immunohistochemical findings between idiopathic inflammatory myopathy ( IIM ) and inclusion body myositis ( IBM ). Methods We assessed 49 biopsied muscle specimens: 32 from IIM patients, 13 from IBM patients, and four from control subjects. Each specimen was classified into one of four grades of histopathological severity. The numbers of regenerative myofibers and nuclei positive for P ax7, M yo D 1, or myogenin were counted. Results P ax7, M yo D 1, and myogenin showed specific nuclear staining patterns. Moreover, myogenin‐positive plaque‐shaped signals were observed within degenerative myofibers in IBM patients, and double immunofluorescence staining showed aggregation of myogenin within A β42‐positive inclusion bodies. The number of nuclei positive for P ax7, M yo D 1, or myogenin correlated with histopathological severity. In the specimens with moderate to severe histopathological changes, specimens from IBM patients showed less regenerative myofibers ( IIM , mean ± SD , 45.0 ± 22.9 per 100 myofibers; IBM , 17.7 ± 7.8 per 100 myofibers; P = 0.0007) and less myogenin‐positive nuclei ( IIM , mean ± SD , 7.28 ± 3.70 per 100 myofibers; IBM , 4.70 ± 1.40 per 100 myofibers; P = 0.0352) than those from IIM patients. Conclusion Aberrant localization of myogenin within degenerative myofibers in IBM may be related to the reduced numbers of regenerative fibers and myogenin‐positive nuclei in IBM . Further study is necessary to determine whether the expression of myogenin might be impaired in IBM .