NCAM, vimentin and neonatal myosin heavy chain expression in human muscle diseases

The intermediate filament protein vimentin, the neonatal isoform of the myo sin heavy chain gene (MHCn), and the neural cell adhesion molecule (NCAM) a re developmentally and/or neurally regulated molecules that reappear transi ently after the induction of necrosis, or denervation. Immunostaining using antibodies against these molecules helps to identify regenerating and/or d enervated muscle fibres even if they are not recognized by conventional sta ining procedures. This study examined the expression of vimentin, MHCn, and NCAM using immunohistochemistry in 82 biopsy specimens from muscular dystr ophies, inflammatory myopathies, and neurogenic atrophies. Anti-vimentin la belled significantly more fibres than anti-MHCn staining in the inflammator y myopathies (P<0.03) but not in the muscular dystrophies (P=0.58) and neur ogenic atrophies (P=0.58). The fraction of NCAM+ fibres was always more ele vated than vimentin + or MHCn + fibres. In the necrotizing myopathies, most NCAM + fibres were regenerating ones (co-expressing vimentin). In neurogen ic atrophies, half the NCAM + fibres were regenerating and half of them wer e NCAM+/vimentin- and thus were considered to be denervated. Taken together , antivimentin staining detects a broader spectrum of regenerating fibres t han anti-MHCn, at least in the inflammatory myopathies. The number of anti- NCAM labelled fibres in the necrotizing myopathies is similar, but not iden tical, to the number of regenerating fibres. Go-staining with anti-vimentin (or anti-MHCn) and anti-NCAM identifies a subset of fibres that is conside red to be denervated.