IMMUNOHISTOCHEMICAL ANALYSIS OF CLINICALLY TRANSPLANTED MUSCLES

Backgrounds. Although a number of studies have examined the morphology and function of experimentally transplanted muscles, immunohistochemi cal evaluation of clinically transplanted muscles has not been reporte d. The purpose of this study was to examine clinically transplanted mu scles at long periods after transplantation with biochemical markers s pecific for satellite cell activation and muscle regeneration. Materia ls and Methods. Nine biopsies of muscles transplanted to the paralyzed face were examined. In five cases, the gracilis muscles were transpla nted about 1 year after cross face nerve grafting. The other four case s underwent one-stage latissimus dorsi (LD) muscle transplantation. Tw elve to 162 months after transplantation, muscle biopsies were harvest ed in nine cases. In eight cases, secondary corrections of facial expr ession including debulking of the grafted muscle were required, while another muscle was transplanted in one case because of the failed firs t operation. As control, six specimens of normal LDs were examined as well. Monoclonal antibodies were employed to visualize myosin heavy ch ain (MHC) isoforms (slow, fast, and embryonic) and MyoD protein. Resul ts. Although one specimen exhibited only small, atrophic fibers indica ting failed reinnervation, the remaining eight specimens showed regula rly distributed fibers and type grouping indicating successful reinner vation, There was no statistically significant difference in fiber are a and lesser diameter between normal LDs and transplanted LDs. However , even in these successfully reinnervated muscles, intermediate and sm all fibers expressing embryonic MHC and small cells expressing MyoD we re observed, suggesting that satellite cells were activated for repair of the adjacent fibers. Conclusions. Muscle adaptation (presumably to denervation), which is a regenerative change accompanied by activatio n of satellite cells, was still seen even long periods after transplan tation. It is concluded that, in microneurovascular human skeletal mus cle transfers, there is a wide variation in the time required for rein nervation of individual muscle fibers, and it may be that human muscle fibers cannot be properly reinnervated after denervation has continue d for a certain period such as 12 months. (C) 1998 Academic Press.