Skeletal muscle-derived exosomes selectively coated miRNAs and participate in myoblast proliferation and differentiation mediated by miR-4331-3p

The phenotypic characteristics and meat quality of skeletal muscles are collectively determined by muscle cells and their intricate interactions with the extracellular microenvironment. In this study, we evaluated muscle fiber phenotypes in the longissimus dorsi (HC-L) and psoas major (HC-P) of Hechuan black pigs. The results revealed significant differences in muscle fiber diameter, density, and type (P < 0.05). Subsequently, co-culture experiments with myoblasts demonstrated that skeletal muscle-derived exosomes (SKM-Exos) promoted myoblast proliferation and differentiation with P-Exo exhibiting superior efficacy in promoting the augmentation of MyHCIIa fiber. Furthermore, SKM-Exos are inherently heterogeneous, and the microRNAs (miRNAs) present in SKM-Exos are selectively coated. Notably, the expression of miR-4331-3p was significantly higher in SKM-Exos than in the corresponding skeletal muscles. The expression of miR-4331-3p was significantly elevated in the SKM-Exos of HC-L compared to that of HC-P, and it interacted with differentially expressed genes between HC-L and HC-P. Moreover, miR-4331-3p enhanced myoblast proliferation and inhibited differentiation. Our findings offer valuable insights into the molecular processes that contribute to meat formation, including intricate cellular interactions.