Muscle regeneration and satellite cells in Fukuyama type congenital muscular dystrophy

To determine the regenerative capability of muscle fibers in Fukuyama type congenital muscular dystrophy (FCMD), muscle biopsies from nine patients were subjected to morphological examination by histochemical and electron microscopic methods. These results were compared with those from six patients with Duchenne muscular dystrophy (DMD) and nine controls. Degenerating and regenerating fibers were not as frequent in FCMD as in DMD, whereas the number of type 2C fibers in the former was about twice that in the latter. On electron microscopy, numerous immature small fibers with disorganized myofibrils, an increased amount of intermediate filaments, large vesicular nuclei, and prominent nucleoli were observed in FCMD. Satellite cells (SCs), which are known to proliferate and contribute to muscle regeneration after myonecrosis, were not increased in number in FCMD. Their incidence, 7.7% +/- 1.8%, was significantly lower than the 16.2% +/- 4.0% in DMD (P less than 0.005). Moreover, the ratio of area of SC nucleus to the overall area of the SC in FCMD, 64.1% +/- 9.7%, was larger than that in DMD, 58.9% +/- 9.3% (P less than 0.005), suggesting that SCs of FCMD were not in an active state. These findings lead to the conclusion that in FCMD the regenerative process is delayed due to either intrinsic or extrinsic factors, such as dense interstitial fibrosis.