Immunolocalization of tenascin-C in human type II fiber atrophy

Tenascin-C is a multifunctional extracellular matrix glycoprotein with stim ulatory and antiadhesive or inhibitory properties for axon growth. Its loca tion and discontinous expression are restricted in innervated muscle tissue s. Tenascin-C accumulated interstitially among human denervated muscle fibe rs and close to normal-sized fibers. To expand our knowledge of the express ion of tenascin-C in human neuromuscular disorders, we investigated immunhi stologically 20 human muscle specimens with type II myofiber atrophy of chi ldren and adults. Tenascin-C immunoreactivity in adult type II atrophy was frequent, and accumulation in children was sparse and weak. In both groups, tenascin-C immunoreactivity was found: 1. Interstitially around normal-sized type II muscle fibers. 2. Around atrophic type II muscle fibers. 3. Around small-caliber myofibers with centrally located nuclei. These results indicate that tenascin-C immunoreactivity: (1) is detectable around early denervated and reinnervated muscle fibers and, therefore, (2) may reflect in part the molecularly ongoing process of denervation and rein nervation in human type II fiber atrophy.