Identification and Functional Characterization of Two Distinct Muscle Stem Cell Populations in Golden Pompano Trachinotus ovatus.

Unlike mammals with determinate growth patterns, large-bodied teleost fish exhibit indeterminate growth. Two distinct muscle stem cell populations have been discovered in teleost fish: muscle satellite cells expressing Pax3 and Pax7, akin to those in mammals, and growth-specific stem cells in the external cell layer (ECL) regulated by Meox1. However, their origins and regulatory mechanisms remain elusive in large teleost fishes. In this study, we identified these two stem cell populations in the golden pompano (Trachinotus ovatus), an economically significant teleost species. In situ hybridization revealed that muscle satellite cells are localized in mononucleated cells at the edges of muscle fibers, while growth-specific stem cells are distributed within the myosepta. Interestingly, growth-specific stem cells in T. ovatus differ from those in zebrafish in their origin, distribution, and expression patterns, which could be a contributing factor to T. ovatus's ability for indeterminate growth, whereas zebrafish exhibit determinate growth. Investigations into the repair and regeneration of skeletal muscle following injury demonstrated that Meox1 also plays a role in repairing injured skeletal muscle, although its involvement occurs later than that of Pax3a/Pax7a. In conclusion, our findings confirm the presence of two distinct muscle stem cell populations in teleost fish, shedding light on the complexity of muscle growth. This research provides insights into muscle development and regeneration, with potential applications in aquaculture for improving muscle growth in economically important fish species.