Muscle cell communication in development and repair.

Under basal conditions, postnatal skeletal muscle displays little cell turnover. With injury, muscle initiates a rapid repair response to reseal damaged membrane, reactivating many developmental pathways to facilitate muscle regeneration and prevent tissue loss. Muscle precursor cells become activated accompanied by differentiation and fusion during both muscle growth and regeneration; inter-cellular communication is required for successful completion of these processes. Cellular communication is mediated by lipids, fusogenic membrane proteins, and exosomes. Muscle-derived exosomes carry proteins and micro RNAs as cargo. Secreted factors such as IGF-1, TGFβ, and myostatin are also released by muscle cells providing local signaling cues to modulate muscle fusion and regeneration. Proteins that regulate myoblast fusion also participate in membrane repair and regeneration. Here we will review methods of muscle cell communication focusing on proteins that mediate membrane fusion, exosomes, and autocrine factors.