Expression of midkine in regenerating skeletal muscle fibers and cultured myoblasts of human skeletal muscle.

Midkine is a member of a family of developmentally regulated neurotrophic and heparin-binding growth factors. The expression of midkine was examined immunohistochemically in biopsied muscle specimens from patients with various myopathies. The intense immunoreactivity of midkine was observed in the sarcoplasm at an early stage regenerating fibers of small diameter. Midkine immunoreactivity was also detected in cultured human skeletal muscle myoblasts from the proliferation stage to the differentiation stage. These results suggest that midkine may be an important skeletal muscle growth-promoting factor that participates in the growth process during skeletal muscle development, proliferation, and differentiation, and in the skeletal muscle regeneration in various neuromuscular disorders. This is the first report demonstrating the presence of midkine in skeletal muscle cells. Copyright 2002 S. Karger AG, Basel