Early satellite cell activation on isolated single muscle fibers

Abstract

Satellite cells are cells of the skeletal Muscle lineage located between the basal lamina and sarcolemma of muscle fibers. Upon injury, normally quiescent satellite cells become "activated" to move, proliferate and differentiate into myoblasts which fuse onto existing myofibers or form new fibers. Hepatocyte Growth Factor (HGF) and crushed muscle extract (CME) have previously been shown to activate satellite cells 'in vitro'. More recently, nitric oxide (NO) release from nitric oxide synthase (NOS) was suggested to activate satellite cells 'in vivo'. We used isolated muscle fibers, a system that allows detailed study of activation signals, o examine the hypothesis that HGF and NO promote satellite cell activation. Normal mouse flexor digitorum brevis (FDB) muscles were dissected, digested in collagenase, and isolated fibers were plated on vitrogen-coated dishes. Fibers were grown in basal medium plus bromodeoxyuridine (BrdU), with or without compounds that could activate satellite cells, and fixed 48 hourslater. Activation was assessed by counting BrdU positive attached, as well as free proliferating satellite cells per fiber. (Abstract shortened by UMI.)