Expression of the low-affinity NGF receptor during human muscle development, regeneration, and in tissue culture

The expression of the low-affinity NGF receptor (LNGFR) during human muscle development, regeneration, and in tissue culture was analyzed using a murine monoclonal antibody to human LNGFR (MAb ME 20.4). Muscle cells from 12-22-week fetuses stained strongly for LNGFR. In adult normal muscle, only intramuscular nerve endings showed immunoreactivity with MAb ME 20.4, but no staining was detected in muscle fibers. In Duchenne muscular dystrophy, immunohistologically demonstrable LNGFR was present in regenerating muscle fibers. In these fibers, LNGFR gene expression was also demonstrated at the transcriptional level using in situ hybridization with riboprobes coding with human LNGFR. Cultures from human fetal and adult muscle were studied by double label indirect immunofluorescence microscopy with MAb ME 20.4 and antisera against human fetal myosin. Most myosin-positive cells, both at the myoblast and myotube stages, displayed surface LNGFR immunostaining. In cells from fetal muscle, LNGFR was detected during the first 2 weeks in vitro, whereas in cells from adult muscle the expression of LNGFR was observed for up to 7 weeks. These findings suggest a potential involvement of LNGFR in human muscle development and regeneration.